Patent Publication Number: US-11390890-B2

Title: Dibasic organic acid producing strain and preparation and application of same

Description:
TECHNICAL FIELD 
     The present invention relates to the field of biotechnology and bioengineering. In particular, the present invention relates to a new engineered bacterium producing dibasic organic acid, and a method for preparing dibasic organic acid by using the same. 
     BACKGROUND 
     In view of the rapid growth in the demand for petroleum-based chemicals or fuels and their increasing costs, and considering the impact of geopolitical instability on crude oil prices and the impact of greenhouse gas emissions on global climate, there is an urgent need to develop a new green process with renewable and sustainable properties to produce these petroleum-based chemicals or fuels. These factors have greatly contributed to the research of using enormous biomass to produce chemicals or fuels, especially using non-food renewable resources as raw materials (second-generation biorefinery). 
     At present, the common process for biomass utilization is divided into three steps: biomass pretreatment, enzymatic hydrolysis and fermentation, wherein the pretreatment still requires high energy consumption and high pollution processes such as high temperature, high pressure, or acid and alkali treatment. In addition, although the yield of cellulolytic enzymes production has reached above the level of 100 g/L, but the application of cellulase in enzymolysis costs too much, and takes a large proportion in the whole process costs, which does not meet the basic requirements of industrial production in large scale. In the practical application, the production process of biomass-based products is greener, more sustainable, and more in line with the trend of modern industrial development, but its production costs are much higher than that of petroleum-based products. The development of bio-refining industry is seriously restricted with the economic factors. 
     DL-malic acid, the product of malic acid as an example of organic dicarboxylic acid, is triditionally completed by chemical catalytic synthesis based on petroleum-based materials, and it&#39;s application is limited in the medicine and food industry because L-malic acid needs to be obtained through optical resolution. The production of single optically active L-malic acid by microbial fermentation draws great concerns and attention. 
     At present, there are still a lot of problems for malic acid fermentation, for example, the temperature for malic acid fermentation is low, therefore the fermentation reaction needs to be continued after cooling down due to the excessive heat produced during the conventional fermentation process. This not only restricted the fermentation efficiency, but also wasted energy. For another example, the cost is higher due to the substrate of glucose, while malic acid with a production level can not be obtained by cheap substrate. 
     Therefore, there is an urgent need to develop a method for producing an organic binary acid, especially malic acid, effectively using cheap substrates. 
     SUMMARY OF THE INVENTION 
     The invention provides a new engineered strain for synthesizing a dibasic organic acid in high yield, and a preparation method and an application thereof. 
     In the first aspect, the invention provides an engineered strain with genetic modification for synthesizing a dibasic organic acid, which introduces or up-regulates the expression of a positive regulator gene for a dibasic organic acid synthesis (preferrably introduces an exogenous positive regulator gene), and/or down-regulates expression of a negative regulator gene of a dibasic organic acid synthesis, and as compared with the origin strain of the engineered strain, the capability for producing the dibasic organic acid is significantly improved, wherein, the dibasic organic acids comprise malic acid, succinic acid, fumaric acid, oxaloacetic acid, glutaric acid, or adipic acid. 
     In another preferred example, the dibasic organic acid is malic acid. 
     In another preferred embodiment, the dibasic organic acid is a C4-C6 dibasic acid. 
     In another preferred example, the producing capacity of the dibasic organic acid is industrial grade. 
     In another preferred embodiment, the original strain of the engineered strains comprises  Myceliophthora  strains,  Thielavia, Aspergillus  or  Rhizopus ; preferably,  Myceliophthora  comprises  Myceliophthora thermophila  or  Myceliophthora heterothallica ; and  Myceliophthora thermophila  is preferred;  Thielavia  comprises  Thielavia terrestris; Aspergillus  comprises  Aspergillus oryzae, Aspergillus flavus, Aspergillus sojae; Rhizopus  comprises  Rhizopus oryzae  Went et Pr.Geerl. 
     In another preferred embodiment, among the original strain genomes, each corresponding positive and/or negative regulator gene of dibasic organic acid synthesis has at least 92%, preferably at least 95%, preferably at least 98%, 99% of homology. 
     In another preferred embodiment, the term “significantly improve” means that compared to the original strain, the engineered strain provides a yield of dibasic organic acid fermentation at least more than 10 g/L, preferably at least 10-50 g/L; more preferably at least 50-300 g/L of the based on the volume of the fermentation liquid; and/or 
     the term “significantly improve” means that compared to the original strain, the engineered strain increases or improves the dibasic organic acid producing capacity by a at least 10%; preferably at least 10-50%; more preferably at least 50%-500%. In another preferred embodiment, the expression product of the positive regulator gene comprises one or more polypeptides or the derivative polypeptides thereof selected from the group consisting of aspartate aminotransferase, glutamate-aspartate transporter, and glucose transporter; and/or 
     the expression product of the negative regulator gene comprises one or more polypeptides or derived polypeptides thereof selected from the group consisting of Succinyl-CoA synthase, and Malic acid-alpha ketoglutarate transporter. 
     In another preferred embodiment, the aspartate aminotransferase is as set forth by SEQ ID NO.: 4. 
     In another preferred embodiment, the glutamate aspartate transporter is as set forth by SEQ ID NO.: 6. 
     In another preferred example, the malate dehydrogenase is as set forth by SEQ ID NO.: 10. 
     In another preferred example, the glucose transporter is as set forth by SEQ ID NO.: 96. 
     In another preferred example, the succinyl-CoA synthase is as set forth by SEQ ID NO.: 2. 
     In another preferred example, the malic acid-alpha ketoglutarate transporter is as set forth by SEQ ID NO.: 8. 
     In another preferred embodiment, an exogenous positive regulator gene for synthesizing the dibasic organic acid is introduced into the engineered strain, and the negative regulator gene of which for synthesizing the dibasic organic acid is simultaneously down regulated. 
     In another preferred embodiment, the expression product of the positive regulator gene also comprises one or more polypeptides or their derivative peptides selected from the group consisting of C4-dicarboxylic acid transporter, pyruvate carboxylase, malate dehydrogenase, glucose transporter and the combinations thereof. 
     In another preferred embodiment, the engineering strains are obtained by the following methods: 
     introducing a positive regulatory gene for synthesizing the dibasic organic acid into an original strain (preferably introducing an exogenous positive regulatory gene) or up-regulating the expression of a positive regulatory gene for synthesizing the dibasic organic acid in an original strain; or down-regulating the expression of a negitive regulatory gene for synthesizing the dibasic organic acid in an original strain. 
     In another preferred embodiment, the polypeptides or the derived polypeptides thereof are selected from the group consisting of 
     (I) one or more sequences of SEQ ID NO.: 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 26, or 96; 
     (II) one or more polypeptides derived from (1) by one or several amino acids deleted, added or substituted from the sequence of SEQ ID NO.: 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 26 or 96, and enabling the engineered strain to have a capacity for producing dibasic organic acid; and 
     (III) one or more polypeptides that have an amino acid sequence having an identity of ≥90% (preferably ≥95%, more preferably ≥98%) with the sequence of SEQ ID NO.: 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 26, or 96 and enabling the engineered strain to have a capacity for producing dibasic organic acid. 
     In another preferred embodiment, a polynucleotide sequence encoding the polypeptide or its derived polypeptide comprises: 
     (i) a polynucleotide encoding a sequence of SEQ ID NO.: 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 26, 28, 30, or 96; 
     (ii) a polynucleotide having a sequence of SEQ ID NO.: 1, 3, 5, 7, 9, 11, 13, 15, 17, 19, 21, 25, or 95; 
     (iii) a polynucleotide sequence having an identity of ≥95% (preferably ≥98%) with a sequence of SEQ ID NO.: 1, 3, 5, 7, 9, 11, 13, 15, 17, 19, 21, 25, or 95; or 
     (iv) a polynucleotide derived from SEQ ID NO.: 1, 3, 5, 7, 9, 11, 13, 15, 17, 19, 21, 25, or 95 by 1-60 (preferably 1-30, more preferably 1-10) nucleotides deleted or added at 5′ end and/or 3′ end; 
     (v) a polynucleotide complementary to any one of the sequence of (I)-(IV). 
     In another preferred embodiment, in the engineered strain with up-regulated expression or introduction of an exogenous positive regulatory gene for synthesizing the dibasic organic acid, compared to the original strain (wild type), the expression of the positive regulator gene is improved by at least 50%, preferably at least 60%, 70%, 80%, 90%, or 100%. 
     In another preferred embodiment, in the engineered strain with down-regulated expression of a negative regulatory gene for synthesizing the dibasic organic acid, compared to the original strain (wild type), the expression of the negative regulator gene is decreased by at least 50%, preferably at least 60%, 70%, 80%, 90%, or 100%. 
     In the second aspect of the invention, a method for preparing a dibasic organic acid is provided, comprising steps of: 
     (i) providing the engineered strain described in the first aspect of the invention; 
     (ii) in the presence of a substrate, culturing the engineered strain described in (i), thereby obtaining a fermentation product containing a dibasic organic acid; and optionally 
     (iii) isolating and purifying the fermentation product obtained in (ii) thereby further obtaining the dibasic organic acid. 
     In another preferred embodiment, the substrate comprises monosaccharide(s), polysaccharide(s), glycan(s), biomass, or combinations thereof. 
     In another preferred embodiment, the polysaccharide comprises sucrose, maltose, cellobiose, fibrous oligosaccharides, xylobiose, xylosaccharides or combinations thereof. 
     In another preferred embodiment, the monosaccharide comprises glucose, xylose, arabinose, or combinations thereof. 
     In another preferred embodiment, the glycan comprises cellulose, crystalline cellulose, hemicellulose, starch or combinations thereof. 
     In another preferred embodiment, the culture temperature of the engineered strain is 25-60° C., preferably 40-55° C., more preferably 45-50° C. 
     In the third aspect of the invention, a method is provided for preparing the engineered strain of the first aspect of the invention, and/or giving a capacity to a  Myceliophthora  strain or enhancing the capacity of a  Myceliophthora  strain for producing a dibasic organic acid, comprising steps of: 
     introducing or up-regulating the expression of a positive regulatory gene for synthesizing the dibasic organic acid (preferably introducing an exogenous positive regulatory gene) in an original strain; and/or down-regulating the expression of a negitive regulatory gene for synthesizing the dibasic organic acid in an original strain, thereby preparing an engineered strain of the first aspect of the invention and/or allowing  Myceliophthora  strain to synthesize the dibasic organic acid. 
     In another preferred embodiment, the method comprises steps of: 
     (a1) providing an expression vector carrying an exogenous positive regulatory gene for synthesizing the dibasic organic acid; 
     (b1) transferring the expression vector into host cells; 
     (c1) culturing the host cells; and/or the method comprises steps of: 
     (a2) knocking out the negative regulatory gene for synthesizing the dibasic organic acid in host cells; 
     (b2) culturing the host cells. 
     In the fourth aspect of the invention, combinations of expression products of a dibasic organic acid producing regulatory gene are provided, comprising at least two polypeptides selected from the group consisting of: 
     (Ia) a sequence of SEQ ID NO.: 4, 6, 10 or combinations thereof; 
     (IIa) polypeptides which are derived from (Ia) by one or more amino acids deleted, added or substituted from the sequence of SEQ ID NO.: 4, 6, or 10 and enable  Myceliophthora  strains to have a capacity and/or enhance the capacity for producing dibasic organic acid; and 
     (Ib) the sequences of SEQ ID NO.: 12, 14, 16, 18, 20, 22, 26, 28, 30, or 96 or combinations thereof; and 
     (IIb) polypeptides which are derived from (Ib) by one or more amino acids deleted, added or substituted from the sequence of SEQ ID NO.: 12, 14, 16, 18, 20, 22, 26, 28, 30, or 96 and enable  Myceliophthora  strains to have a capacity for producing dibasic organic acid and/or enhance the capacity for producing dibasic organic acid; and 
     In another preferred embodiment, the combination comprises at least the sequences of SEQ ID NO.: 4 and 6. 
     In another preferred embodiment, the combination comprises at least the sequences of SEQ ID NO.: 6 and 10. 
     In another preferred embodiment, the combination comprises at least the sequences of SEQ ID NO.: 4 and 10. 
     The fifth aspect of the invention provides a combination of the dibasic organic acid producing regulatory genes, which comprises at least two kinds of polynucleotides that encode the expression product in the combination of expression products of the fourth aspect of the invention. 
     In the sixth aspect of the invention provides a carrier comprising the combination of the fifth aspect of the invention, and/or containing an inhibitor that inhibits the negative regulator gene of the dibasic organic acid production. 
     In another preferred embodiment, the inhibitor is an interference RNA or antisense nucleic acid of the negative regulator gene (such as Succinyl-CoA synthase) of a dibasic organic acid production. 
     In another preferred embodiment, the sequence of the interfering RNA is as set forth by SEQ ID NO.: 74 or 75. 
     In another preferred embodiment, there are one or more carriers. 
     In the seventh aspect of the invention, a host cell is provided that has characteristics selected from the group consisting of: 
     (a1) containing the carrier of the first aspect of the invention; 
     (b1) the chromosomes of the host cells are artificially integrated with the polynucleotide that encodes the polypeptide of SEQ ID NO.: 4, 6, 10, or 96 or the expression of the original gene encoding said polypeptide is up-regulated; or the gene encoding the polypeptide of SEQ ID NO.: 2 and/or 8 in the chromosome of the host cell is knocked out or weakened; and optionally 
     the chromosomes of the host cells are integrated with one or more polynucleotide(s) selected from the polypeptides of SEQ ID NO.: 4, 6, 10, 12, 14, 16, 18, 20, 22, 26, and 96. 
     In another preferred embodiment, the host cell is the engineered strain of the first aspect of the invention. 
     In another preferred embodiment, the host cell is  Myceliophthora  strain, preferably  Myceliophthora thermophila.    
     The eighth aspect of the invention, a use of the combination of the forth aspect of the invention is provided for preparing the engineered strain of the first aspect of the invention, and/or giving a capacity to  Myceliophthora  strain or enhancing the capacity of  Myceliophthora  strain for producing dibasic organic acid. 
     In another preferred embodiment, said “giving” or “enhancing” the capacity for producing dibasic organic acid refers to that after reconstruction the strain originally having no capability for producing and/or accumulating dibasic organic acid ability has a capacity for industrially producing dibasic organic acid, and/or the strain originally having poor capability for producing and/or accumulating dibasic organic acid has an enhanced capacity for industrially producing dibasic organic acid. 
     In the ninth aspect of the invention, an engineered strain with genetic modification for synthesizing the dibasic organic acid is provided, said engineered strain allows the dibasic organic acid to be obtained in a fermentation temperature of 25-60° C. by using glycan and/or biomass as a fermentation substrate, 
     wherein the original strain of the engineered strain is  Myceliophthora;    
     and the dibasic organic acid comprises malic acid, succinic acid or fumaric acid. 
     In another preferred embodiment, the dibasic acid also comprises oxaloacetic acid, glutaric acid, or adipic acid. 
     In another preferred embodiment, the substrate comprises monosaccharides, polysaccharides, or the combinations thereof. 
     In another preferred embodiment, the engineered strain is artificially integrated with the positive regulatory gene for synthesizing the dibasic organic acid or up-regulates the expression of the positive regulatory gene for synthesizing the dibasic organic acid, and/or expresses down-regulatedly the negative regulatory gene of the dibasic organic acid synthesis, and compared with the original strain, the capacity of the engineered strain for producing dibasic organic acid is significantly improved. 
     In another preferred embodiment, the glycan comprises cellulose, crystalline cellulose, hemicellulose, starch (preferably corn, cassava, wheat) or combinations thereof. 
     The biomass comprises crop straw, forestry waste, papermaking industry waste, cotton textile industry waste, energy plant or part or all of its decomposition products; wherein the crop straw comprises corn straw, wheat straw, rice straw, sorghum straw, soybean straw, cotton straw, bagasse, or corncob; the forestry waste comprised branches, leaves, or sawdust; the papermaking industry waste comprises pulp slag, pulp waste; the cotton textile industry waste comprises wasten cotton and cotton textiles; the energy plants comprises sweet sorghum, switchgrass,  miscanthus , reed or combinations thereof. 
     In another preferred embodiment, the substrate only comprises glycans and/or biomass. 
     In another preferred embodiment, the fermentation temperature is 40-55° C., preferably 45-53° C., more preferably 48-50° C. 
     In another preferred embodiment, the dibasic organic acid is malic acid. 
     In another preferred embodiment, the dibasic organic acid is a C4-C6 dibasic acid. 
     In another preferred embodiment, the producing capacity of the dibasic organic acid is industrial grade. 
     In the tenth aspect of the invention, a method for preparing a dibasic organic acid is provided, comprising steps of: 
     (i) providing the engineered strain of the ninth aspect of the invention; 
     (ii) in the presence of a substrate, culturing the engineered strain of (i), thereby obtaining a fermentation product containing dibasic organic acid, wherein the fermentation temperature is 25-60° C.; and optionally 
     (iii) isolating and purifying the fermentation product obtained in (ii) thereby further obtaining the dibasic organic acid; 
     wherein, the substrate comprises glycans and/or biomass. 
     In another preferred embodiment, the culture temperature of the engineered strain is 40-55° C., preferably 45-52° C., more preferably 48-50° C. 
     In another preferred embodiment, the substrate is cellulose, hemicellulose, starch, or biomass. 
     In another preferred embodiment, the substrate further comprises monosaccharides, polysaccharides, or combinations thereof. 
     In another preferred embodiment, the polysaccharide comprises sucrose, maltose, cellobiose, fibrous oligosaccharides, xylobiose, xylosaccharides or combinations thereof. 
     In another preferred embodiment, the monosaccharide comprises glucose, xylose, arabinose, or combinations thereof. 
     In the present invention, the producing capacity comprises, but is not limited to, the fermentation product concentration (titer), and/or conversion (yield), and/or the fermentation yield (productivity). 
     It should be understand that within the scope of the invention each of the technical features described in detail above and below (such as the examples) can be combined with each other separately, so as to form a new or preferred technical proposal, which will no longer be described herein due to the length limitation. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a physical map of the mae gene expression vector pAN52-mae. 
         FIG. 2  shows a physical map of the expressing vector pAN52-TB-Ptef. 
         FIG. 3  shows a physical map of the mae gene and pyc gene co-expression vector pAN52-mae-pyc. 
         FIG. 4  shows a physical map of the mdh gene expression vector pAN52-mdh. 
         FIG. 5  shows a physical map of a binary carrier pAN52-SCLsilent-A. 
         FIG. 6  shows a physical map of a binary carrier pAN52-SCLsilent-B. 
         FIG. 7  shows a physical map of the knocking out carrier pPK2sur-barGFP::odc. 
         FIG. 8  is a physical map of the plasmid pMF272. 
         FIG. 9  shows the malic acid yield map in different strains on the eighth day with crystalline cellulose as a carbon source. 
         FIG. 10  shows a malic acid yield map in  M. thermophila  which overexpresses C4-dicarboxylic acid transporter. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     After extensive and thorough research, the inventors firstly and surprisingly discover a set of regulatory genes for producing or synthesizing a dibasic organic acid in filamentous fungi strains, especially  Myceliophthora  strains (such as  Myceliophthora  thermophilic), wherein, genes having a function of positive regulation comprise aspartate aminotransferase, glutamic acid-aspartate transporter, malate dehydrogenase, C4-dicarboxylic acid transporter, pyruvate carboxylase, glucose transporter, or combinations thereof, genes having a function of negative regulation comprise succinyl-CoA synthase, malic acid-alpha ketoglutarate transporter, or combinations thereof. It has been confirmed by the inventors that by up-regulation of one or more of the positive regulator genes and\or down-regulation of one or more of the negative regulator genes, the genetic modified engineered strain can effectively use monosaccharide, polysaccharide, glycans or mixed sugars, especially cheap polysaccharide (such as cellulose, etc.) to synthesize dibasic organic acid in high yield under high temperature conditions. In addition, the inventors also have confirmed by experiments that the regulatory function has relative strain species specificity. On this basis, the invention is completed. 
     Dibasic Organic Acid 
     As used herein, the term “dibasic organic acid” refers to organic acids in which each molecule can ionize two and only two hydrogen ions in water. The dibasic organic acid which can be used herein comprises C4-C6 dibasic organic acid, preferably C4-C5 dibasic organic acid, such as malic acid, succinic acid, fumaric acid, oxaloacetic acid, glutaric acid, or adipic acid. Preferably, the dibasic organic acid of the invention comprises malic acid or succinic acid. 
     Taking Malic acid for an example, L-malic acid is an important natural organic acid, and widely used in food, beverages, spices, healthcare, chemicals, plastics and other industries. In the food industry, L-malic acid can be used as an acidity regulator, a food preservative, a food deodoriant, or a pasta enhancer, and in the pharmaceutical industry, L-malic acid can be added in drug injections, preparations, tablets, or syrups for helping to improve the utilization rate of the medicine. In the daily chemical industry, it can be used as an ingredient of deodorants and detergents. Malic acid has an important position and plays an important role in the organic acid industry. In recent years, the demand for malic acid in the international market increases rapidly, and the market prospect is bright. 
     Traditionally, the production of malic acid is completed by chemical catalytic synthesis based on petroleum-based materials, and the product is DL-malic acid which limits its application in medicine and food industry because L-malic acid needs to be obtained through optical resolution. The production of L-malic acid with single optical rotation by microbial fermentation has been widely concerned and highly valued. 
     In addition, the inventors have found that not only the malic acid (and even organic acid) fermentation in  Myceliophthora  can be enhanced through regulating multiple new genes, but also the organic acid producing capacity of strains (including  Aspergillus  (preferably  Aspergillus oryzae, Aspergillus sojae, Aspergillus terreus, Aspergillus niger ),  Rhizopus  (preferably  Rhizopus oryzae ), beside the  Myceliophthora  with accumulation ability) can be improved by genetic modification. 
     “a capacity for producing organic acid” herein refers to the industrialized capacity for producing organic acid, which is equivalent to the term of “industrial production level”, “industrialized potential”, “industrial producing capacity”, or “organic acid producing capacity”, which can be used interchangeably, and refers to the total volume of fermentation liquid, the fermentation yield is at least 10 g/L, preferably at least 15-40 g/L; more preferably, at least 50-300 g/L, and any integer and non-integer in this range, which is no longer listed one by one. 
     For the fermentation of malic acid and other organic acids, the traditional dominant strain is  aspergillus  strain. In addition, some traditional dominant strains of organic acids include but not limited to: Citric acid- Aspergillus niger , Malic acid- Aspergillus flavus, Aspergillus oryzae , or Lactic acid- Rhizopus oryzae . But  Myceliophthora  does not belong to common strains which accumulating organic acids. The invention has shown that for strains (such as  Neurospora crassa, Trichoderma reesei ) that have few accumulation of organic acids (usually no more than the grade of gram/liter) in natural conditions, the modification of the synthesizing rout of organic acids (such as malic acid) will not effectively improve their producing yield to industrial level (10 g/l or more), but in the case of strains that did not accumulate organic acids, i.e  Myceliophthora  strains ( Myceliophthora thermophila, Myceliophthora heterothallica ), the capacity for synthesizing organic acid (malic acid) was significantly improved (10 g/I or more) by genetic modification, which is very surprising. 
     Substrate 
     As used herein, the term “substrate” refers to carbohydrates that can produce a dibasic organic acid in the presence of filamentous fungi, including monosaccharides, polysaccharides, glycans, biomass or a combination thereof, wherein the term “monosaccharide” includes but not limited to glucose, xylose, Arabia sugar or a combination thereof; “polysaccharide” includes but not limited to sucrose, cellobiose, cello-oligosaccharides, xylobiose, xylo-oligosaccharides or a combination thereof, wherein the “glycans” includes but not limited to cellulose (especially cellulose from biomass source), hemicellulose, or its combination; biomass includes but not limited to crop straw, forestry waste, paper-making industry waste, energy plant, or a combination thereof. Examples of preferred substrates are described below: 
     Glucose, xylose, and Arabia sugar are three important monosaccharides. Glucose (chemical formula is C 6 H 12 O 6 ) is also known as corn glucose, corn sugar, referred to as glucose, is one of the most widely distributed and most important monosaccharides in nature. Glucose plays an important role in biology field. It is the energy source and metabolic intermediate product of living cells, that is, the main energy supply of biological substances. It has been widely used in confectionery manufacturing and medicine field. It can be largely prepared in industry by using corn, cassava, etc. as raw materials. 
     Xylose is a five carbon pentose and is the main monosaccharide that makes up hemicellulose, therefore, xylose also widely exists in abandoned parts of agricultural products such as corn cob, straw, the skin of cotton boll and others. It can be obtained by hydrolysis from hemicellulose in biomass. 
     Arabia sugar, also called pectose, often exists in the form of heteropolysaccharide in combined with other monosaccharides. Arabia sugar exists in the cereale such as cornmeal, corncob, rice, wheat etc. and in hemicelluloses and pectic substances in the cell walls of the plants such as beet, apple and others. Xylose and arabinose are the most important five carbon sugars obtained after the degradation or pretreatment of biomass. Microorganisms are usually difficult to be used, which is the difficulty in utilizing whole sugar of biomass. 
     Sucrose, cellobiose and xylobiose are three important disaccharides. Sucrose is the main product of photosynthesis, and widely distributed in plants, especially in sugar beet, sugar cane and fruit, in which the content is extremely high. Sucrose is a disaccharide which is formed by dehydration condensation of one molecule of glucose and one molecule of fructose and widely used in the biological fermentation industry. It is the raw material of various products such as alcohol, citric acid, lactic acid, glycerol, alcohol, medicine and others. Whereas the cellulose is composed of cellobiose, which can be degraded from cellulose further hydrolyzed into two molecules of glucose. Xylobiose is a xylo-oligosaccharide formed by two xylose through beta-1,4-glycosidic bond, and is a linear disaccharide. It can be obtained by hydrolysis of hemicellulose and can further be decomposed into two xyloses. 
     Cello-oligosaccharides and xylosaccharides are two important oligosaccharides. Cello-oligosaccharides usually refer to oligosaccharides produced by glucose through the linkage of beta-1,4 glycosidic bonds. Xylosaccharides, also known as xylo oligosaccharides, are oligosaccharides formed by 2-7 of D-xylose through the linkage of beta-1,4-glycosidic bonds, and some may also contain arabinose, glucuronic acid and other side chains. Xylobioses, xylosaccharides, cello-oligosaccharides and cellobioses are the main products of cellulose and hemicellulose in plant cellulose (corn cob, bagasse, straw, etc.) through hydrolysis. 
     Biomass mainly contains cellulose, hemicellulose and lignin. All kinds of crop and energy plant straws (corn straw, wheat straw, rice straw, sorghum straw, bagasse,  miscanthus  etc.), forestry wastes (sawdust, branches and leaves), papermaking industry waste and so on are important biomass resources. Under certain conditions, they can be degraded into glycans (such as xylan, glucan), oligosaccharides and monosaccharides which can be used by some microbial fermentation. Developing the use of available biomass hydrolysates or even the biomass after simple pretreatment as a carbon source to produce chemical products (ethanol, organic acids, etc.) through fermentation is an important research at home and abroad. 
     The Dibasic Organic Acid Synthesis Regulatory Gene and its Expression Product 
     As used herein, the term “the dibasic organic acid synthesis regulatory gene” and “the polynucleotides that encode the polypeptides of the invention” can be used interchangeably, and includes “the positive regulatory gene and the negative regulator gene for synthesizing the dibasic organic acid”. Wherein the terms “positive regulatory gene for synthesizing the dibasic organic acid”, “positive regulatory gene” and “overexpressing gene” can be used interchangeably and refer to one or more positive genes capable of promoting or enhancing the synthesis of the dibasic organic acids in filamentous fungi (e.g.,  Myceliophthora, Aspergillus oryzae, Aspergillus sojae, Aspergillus terreus , etc.); the terms “negative regulatory gene for synthesizing the dibasic organic acid” and “the negative regulatory gene” refer to one or more negative genes capable of inhibiting or reducing the synthesis of the dibasic organic acids in filamentous fungi; the terms “introduction” and “artificial integration” can be used interchangeably, and the introduced gene can be exogenous and endogenous; wherein, after genetic modification, the highly expressed or overexpressed positive regulator gene or the lowly expressed or knocked out negative regulator gene can make the modified strain has significantly improved capacity for producing dibasic organic acid compared with its original strain. 
     Preferably, the expression product of the positive regulatory gene comprises one or more polypeptides of the invention or their derived polypeptides selected from the group consisting of aspartate aminotransferase, glutamic acid-aspartate transporter, C4-dicarboxylic acid transporter, malate dehydrogenase, pyruvate carboxylase, and glucose transporter. The expression product of the negative regulatory gene includes one or more polypeptides of the invention or their derived polypeptides selected from the group consisting of succinyl-CoA synthase, and malic acid-alpha ketoglutarate transporter. 
     More preferably, the polypeptides of the invention or their derived polypeptides are selected from the group consisting of 
     (I) sequences of SEQ ID NO.: 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 26, or 96; 
     (II) polypeptides which are derived from (1) by one or more amino acids deleted, added or substituted from the sequence of SEQ ID NO.: 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 26 or 96 and enable the engineered strain to have the capacity for producing dibasic organic acid; and 
     (III) polypeptides that have an amino acid sequence having a identity of ≥90% (preferably ≥95%, more preferably 98%) with the sequence of SEQ ID NO.: 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 26, or 96 and enable the engineered strain to have a capacity for producing dibasic organic acid. 
     The derived polypeptide comprises a variant of a sequence as set forth by SEQ ID NO. 2, 4, 6, 8, 10, 12, 14, 16, 20, 22 or 96 which can make the original strain have the capacity for synthesizing the dibasic organic acid. These variants include (but not limited to): deletion, insertion and/or substitution of 1-3 (usually 1-2, preferably 1) of amino acids, and addition or deletion of one or more (usually less than 3, preferably less than 2, preferably less than 1) of amino acids at the C terminal and/or N terminal. For example, in this field, the function of proteins is usually not altered by the substitution of amino acids with close or similar properties. Also, for example, the addition or deletion of one or several amino acids at the C terminal and/or N terminal will not usually alter the structure and function of the protein. The terms “fragments”, “derivatives” and “analogues” refer to polypeptides that substantially maintain the ability to allow the original strain have the capacity for synthesizing the dibasic organic acid. The polypeptide fragments, derivatives or analogs of the invention may be (i) polypeptides having one or several conservative or non-conservative amino acid residues (preferably conservative amino acid residues) substituted, or (ii) polypeptides having substituent(s) in one or more amino acid residues, or (iii) polypeptides formed by fusing the polypeptide of the invention with another compound, such as a compound that extends the half-life of the polypeptide, or (iv) a polypeptide in which the additional amino acid sequence is fused to the polypeptide sequence (a fusion protein formed by fusion of a leader sequence, a secretory sequence, or a label sequence such as 6His). These fragments, derivatives and analogs are within the scope of what is known to those skilled in the art in light of the teachings herein. A preferred class of active derivatives refers to a polypeptide formed by up to 3, preferably up to 2, more preferably up to 1 of amino acid substituted with amino acids having close or similar property as compared to the amino acid residues of Formula 1. These conserved variant polypeptides are preferably produced by the amino acid substitutions according to Table 1. 
     
       
         
           
               
               
               
             
               
                 TABLE 1 
               
               
                   
               
               
                   
                   
                 Preferred 
               
               
                 Primary residue 
                 Representative substitution 
                 substitution 
               
               
                   
               
             
            
               
                 Ala (A) 
                 Val; Leu, Ile 
                 Val 
               
               
                 Arg (R) 
                 Lys; Gin; Asn 
                 Lys 
               
               
                 Asn (N) 
                 Gln, His; Lys; Arg 
                 Gln 
               
               
                 Asp (D) 
                 Glu 
                 Glu 
               
               
                 Cys (C) 
                 Ser 
                 Ser 
               
               
                 Gln (Q) 
                 Asn 
                 Asn 
               
               
                 Glu (E) 
                 Asp 
                 Asp 
               
               
                 Gly (G) 
                 Pro; Ala 
                 Ala 
               
               
                 His (H) 
                 Asn, Gin; Lys; Arg 
                 Arg 
               
               
                 Ile (I) 
                 Leu, Val; Met; Ala; Phe 
                 Leu 
               
               
                 Leu (L) 
                 Ile, Val; Met; Ala; Phe 
                 Ile 
               
               
                 Lys (K) 
                 Arg, Gln, Asn 
                 Arg 
               
               
                 Met (M) 
                 Leu, Phe, Ile 
                 Leu 
               
               
                 Phe (F) 
                 Leu, Val; Ile, Ala; Tyr 
                 Leu 
               
               
                 Pro (P) 
                 Ala 
                 Ala 
               
               
                 Ser (S) 
                 Thr 
                 Thr 
               
               
                 Thr (T) 
                 Ser 
                 Ser 
               
               
                 Trp (W) 
                 Tyr; Phe 
                 Tyr 
               
               
                 Tyr (Y) 
                 Trp, Phe, Thr, Ser 
                 Phe 
               
               
                 Val (V) 
                 Ile, Leu, Met; Phe, Ala 
                 Leu 
               
               
                   
               
            
           
         
       
     
     In another preferred embodiment, a sequence of a polynucleotide encoding the polypeptide or its derived polypeptide of the invention (the polynucleotide of the invention) comprises: 
     (i) a polynucleotide encoding a sequence of SEQ ID NO.: 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 26, 28, 30, or 96; 
     (ii) a polynucleotide having a sequence of SEQ ID NO.: 1, 3, 5, 7, 9, 11, 13, 15, 17, 19, 21, 25, or 95; 
     (iii) a polynucleotide sequence having an identity of ≥95% (preferably ≥98%) with a sequence of SEQ ID NO.: 1, 3, 5, 7, 9, 11, 13, 15, 17, 19, 21, 25, or 95; or 
     (iv) a polynucleotide derived from SEQ ID NO.: 1, 3, 5, 7, 9, 11, 13, 15, 17, 19, 21, 25, or 95 by 1-60 (preferably 1-30, more preferably 1-10) nucleotides deleted or added at 5′ end and/or 3′ end; 
     (v) a polynucleotide complementary to any one of the sequence of (I)-(IV). 
     The full-length sequence of the polynucleotide or its fragment of the invention can usually be obtained by PCR amplification, recombination or artificially synthesis. A preferred method to obtain the polynucleotides of the invention generally has the following steps: 
     (1) transforming or transducing a suitable host cell with a recombinant expression vector of a polynucleotide (or a variant) encoding the polypeptide of the invention, or a recombinant expression vector containing the polynucleotide; 
     (2) culturing the host cell in suitable medium 
     (3) isolating and purifying proteins from the medium or the cell. 
     The sequencesofthepolypeptidesoftheinventionandthecorrespondingecoding polynucleotides are shown in table 2: 
     
       
         
           
               
               
               
               
               
             
               
                 TABLE 2 
               
               
                   
               
               
                   
                   
                   
                 nucleotide 
                 amino acid 
               
               
                 Name of the Protein 
                   
                   
                 sequence 
                 sequence 
               
               
                 (polypeptide of the 
                   
                   
                 (SEQ ID 
                 (SEQ ID 
               
               
                 invention) 
                 source 
                 function 
                 NO.:) 
                 NO.:) 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
            
               
                 succinyl-CoA  
                 
                   Myceliophthora 
                 
                 Negative 
                 1 
                 2 
               
               
                 synthase 
                 
                   thermophila 
                 
                 regulation 
                   
                   
               
               
                 aspartate 
                 
                   Myceliophthora 
                 
                 Positive 
                 3 
                 4 
               
               
                 aminotransferase 
                 
                   thermophila 
                 
                 regulation 
                   
                   
               
               
                 glutamic acid- 
                 
                   Myceliophthora 
                 
                 Positive 
                 5 
                 6 
               
               
                 aspartate 
                 
                   thermophila 
                 
                 regulation 
                   
                   
               
               
                 transporter 
                   
                   
                   
                   
               
               
                 malic acid-alpha 
                 
                   Myceliophthora 
                 
                 Negative 
                 7 
                 8 
               
               
                 ketoglutarate  
                 
                   thermophila 
                 
                 regulation 
                   
                   
               
               
                 transporter 
                   
                   
                   
                   
               
               
                 malate  
                 
                   Myceliophthora 
                 
                 Positive 
                 9 
                 10 
               
               
                 dehydrogenase 
                 
                   thermophila 
                 
                 regulation 
                   
                   
               
               
                 C4-dicarboxylic acid 
                 
                   Aspergillus 
                 
                 Positive 
                 11 
                 12 
               
               
                 transporter 
                 
                   oryzae 
                 
                 regulation 
                   
                   
               
               
                 C4-dicarboxylic acid 
                 
                   Neurospora 
                 
                 Positive 
                 13 
                 14 
               
               
                 transporter 
                 
                   crassa 
                 
                 regulation 
                   
                   
               
               
                 C4-dicarboxylic acid 
                 
                   Trichoderma 
                 
                 Positive 
                 15 
                 16 
               
               
                 transporter 
                 
                   reesei 
                 
                 regulation 
                   
                   
               
               
                 C4-dicarboxylic acid 
                 
                   Myceliophthora 
                 
                 Positive 
                 17 
                 18 
               
               
                 transporter 
                 
                   thermophila 
                 
                 regulation 
                   
                   
               
               
                 C4-dicarboxylic acid 
                 
                   Aspergillus 
                 
                 Positive 
                 19 
                 20 
               
               
                 transporter 
                 
                   niger 
                 
                 regulation 
                   
                   
               
               
                 C4-dicarboxylic acid 
                 
                   Aspergillus 
                 
                 Positive 
                 21 
                 22 
               
               
                 transporter 
                 
                   sojae 
                 
                 regulation 
                   
                   
               
               
                 pyruvate carboxylase 
                 
                   Aspergillus 
                 
                 Positive 
                 25 
                 26 
               
               
                   
                 
                   oryzae 
                 
                 regulation 
                   
                   
               
               
                 glucose transporter 
                 
                   Neurospora 
                 
                 Positive 
                 95 
                 96 
               
               
                   
                 
                   crassa 
                 
                 regulation 
               
               
                   
               
            
           
         
       
     
     Engineered Strain and Preparation Method Thereof 
     The terms “Engineering bacteria”, “engineered strain” and “genetic modified strain” of the invention can be used interchangeably, referring to the engineered strain in which the positive regulatory gene for synthesizing the dibasic organic acid is introduced or the expression of the positive regulatory gene for synthesizing the dibasic organic acid is up-regulated, and/or the expression of the negitive regulatory gene for synthesizing the dibasic organic acid is down-regulated. Among them, compared with its original strain, the dibasic organic acid producing capacity of the the engineered strain of the invention is significantly improved, wherein the dibasic organic acid comprises malic acid, succinic acid, fumaric acid, oxaloacetic acid, glutaric acid or adipic acid. 
     The original strain that can be modified to the engineered strain of the invention is usually filamentous fungi, especially filamentous fungi of  Myceliophthora , such as  Myceliophthora thermophila, Myceliophthora heterothallica , preferably  Myceliophthora thermophila . The wild original strain usually does not have the capacity to synthesize the dibasic organic acid, or does not have the capacity for producing dibasic organic acid of an amount required in industry. Normally, an original strain in which a dibasic organic acid can be produced in the natural state, but will be rapidly converted into downstream metabolites (i.e., no accumulation of a dibasic organic acid can be formed) is also within the scope of the original strain of the invention. After genetic modification, the capacity for producing dibasic organic acid of the engineered strain of the invention is significantly improved, and the term “significantly improve” includes the strain that originally has no capacity for synthesizing the dibasic organic acid has that ability, or that ability is substantially increased compared with the original strain. Preferably, the term “significantly improve” means that compared to the original strain the capacity for producing dibasic organic acid of the engineered strain is increased or improved by at least 10%; preferably at least 10-50%; more preferably at least 50%-500%. 
     In addition, the original strain that can be modified into the engineered strain of the invention can also include  Thielavia , preferably  Thielavia terrestris; Aspergillus , preferably  Aspergillus oryzae, Aspergillus flavus, Aspergillus sojae ; and  Rhizopus.    
     The engineered bacteria of the invention can be prepared by the following methods: 
     (a1) providing an expression vector carrying a positive regulatory gene for synthesizing the dibasic organic acid; 
     (b1) transferring the expression vector into a host cell; 
     (c1) culturing the host cell; and/or 
     the method comprises steps of: 
     (a2) knocking out the negitive regulatory gene for synthesizing the dibasic organic acid in host cells; 
     (b2) culturing the host cells; 
     wherein, the host cell is the original strain. 
     The negative regulatory gene of the invention can be knocked out or down regulated by genetic engineering means or substances that inhibit the expression and/or activity of the negative regulatory gene so as to obtain a new transgenic engineered bacterium. Such substances are known as “inhibitors of the invention” or “negative regulatory genes inhibitors”. The inhibitors, for example, include antibodies inhibitory mRNA, antisense RNA, microRNA (miRNA), siRNA, shRNA to the negative regulatory genes, and activity inhibitors of zinc finger transcription factors. A preferred inhibitor is a negative regulatory gene of siRNA, such as a sequence of SEQ ID NO.: 1. According to the sequence of SEQ ID NO.: 1 of the invention, siRNAs that inhibiting its expression can be designed by conventional techniques in the art, and the preferred siRNAs are shown in SEQ ID NO.: 74 and 75. 
     Combination of the Regulatory Gene for Producing Dibasic Organic Acid or the Expression Products Thereof 
     The invention also provides a combination of the polypeptides of the invention or their encoding polynucleotides. The experiment has proved that it can effectively improve the capacity of the strain for producing dibasic organic acid by using the combination of the invention to modify the original strain simultaneously. Wherein the combination of the regulatory gene expression products of the invention may include at least two polypeptides selected from the group consisting of 
     (Ia) a sequence of SEQ ID NO.: 4, 6, or 10 or combinations thereof; or 
     (IIa) a polypeptide derived from (Ia) by one or more amino acids deleted, added or substituted from the sequence of SEQ ID NO.: 4, 6, or 10 and enabling  Myceliophthora  strains to have the capacity for producing dibasic organic acid and/or increasing the capacity for producing dibasic organic acid; and optional 
     (Ib) a sequence of SEQ ID NO.: 12, 14, 16, 18, 20, 22, 26, 28, 30, 96 or combinations thereof; 
     (IIb) a polypeptide derived from (Ib) with one or more amino acids deleted, added or substituted from the sequence of SEQ ID NO.: 12, 14, 16, 18, 20, 22, 26, 28, 30, or 96 and enabling  Myceliophthora  strains to have the capacity for producing dibasic organic acid and/or increase the capacity for producing the dibasic organic acid. 
     While the combination of the dibasic organic acid producing regulatory genes of the invention contains at least two polynucleotides, and the polynucleotides correspondingly encode the polypeptides in the combination of the expression products of the invention, respectively. 
     In addition, the invention also provides a vector containing the gene combination of the invention, and a host cell comprising the vector or the chromosome with the positive regulator gene for producing the dibasic organic acid intergrated and/or with the negative regulator gene for producing the negative regulator gene down-regulated. 
     Preferrably, the chromosome of the host cell of the invention is artificially integrated with the polynucleotide that encodes the polypeptides of SEQ ID NO.: 4, 6, and/or 10; or the gene that encodes the polypeptides of SEQ ID NO.: 2 and/or 8 in the chromosome of the host cell is knocked out or weakened; and optionally 
     the chromosome of the host cell is integrated with one or more polynucleotides selected from the polypeptides of SEQ ID NO.: 4, 6, 10, 12, 14, 16, 18, 20, 22, 26, and 96. 
     The Beneficial Effects of the Invention 
     (a) By using a protoplast or an  agrobacterium  mediated transformation/transfection method, a heterologous or homologous nucleic acid sequence is stably introduced into an original strain, said nucleic acid sequence is operably linked to the expression regulatory region, while knocking-out or mutation or attenuated expression and screening for gene and knock out the transformants with the assistance of green fluorescent protein are also included. The genetic operation technique system of  Myceliophthora thermophila  is underdeveloped. The present invention firstly uses the genetic engineering technology to transform  Myceliophthora thermophila  and thereby producing the dicarboxylic acid by fermentation. 
     (b) A set of new key genes impacting the dicarboxylic acid fermentation level in filamentous fungi are discovered, and the fermentation level of the dicarboxylic acid (especially malic acid) is improved through the genetic modification in  Myceliophthora , wherein the genes include succinyl-CoA synthase, aspartate aminotransferase, malic acid-alpha ketone glutaric acid transporter, glutamic acid-aspartate transporter and C4-dicarboxylic acid transporter, glucose transporter, or malate dehydrogenase. 
     (c) Under certain conditions, dibasic acids are produced from the recombinant strains with a variety of carbon sources as fermentation substrates, including biomass resources, which greatly reduces the cost of fermentation of biomass-based chemicals. L-malic acid is directly produced by fermentation of microorganisms (and the production of other dibasic organic acids and even more chemicals are allowed). 
     (d) The fermentation temperature is high. The fermentation can be conducted at 40-50 degrees (preferably 45 degrees), which significantly save the condensation costs during the fermentation, thereby reducing the cost of the fermentation. The strains of the invention can synthesize the dibasic organic acid with high yield at high temperature which can not be tolerated by the room temperature filamentous fungi (such as  Aspergillus ). 
     The invention will now be further described with reference to specific embodiments. It should be understood that these examples are merely illustrative of the invention and are not intended to limit the scope of the invention. The experimental methods not specified for conditions in the following examples are generally carried out according to conventional conditions, such as those described in Sambrook et al., Molecular Cloning: Laboratory Manual (New York: Cold Spring Harbor Laboratory Press, 1989), or conditions suggested by the manufacturer. Unless otherwise specified, percentages and parts are those by weight. 
     Example 1 Overexpressing C4-Dicarboxylic Acid Transporter Encoding Gene Mae in  Myceliophthora thermophila  to Allow  Myceliophthora thermophila  to Obtain a Capacity for Producing Malic Acid 
     1. Construction of a vector with mae overexpressed (pAN52-mae) 
     Pan52-TB-Intron (Liu Q, Li J, Ying S, Wang J, Sun W, Tian C, Feng M. 2014. Unveiling equal importance of two 14-3-3 proteins for morphogenesis, conidiation, stress tolerance and virulence of an insect pathogen. Environ Microbiol. doi: 10.1111/1462-2920.12634) was used as the skeleton to construct the expression vector, wherein the plasmid pCSN44 (available from fungal genetics stock center) was used as a template and Hygromycin phosphotransferase coding gene (hph) was PCR amplified under the regulatory of TrpC promoter according to the guidance of primers. The sequences of the primers are as follows: 
     
       
         
           
               
               
            
               
                   
                 hph-F (SEQ ID NO.: 23): 
               
               
                   
                 GCTCTAGACAGAAGATGATATTGAAGGAGC 
               
               
                   
                   
               
               
                   
                 hph-R (SEQ ID NO.: 24): 
               
               
                   
                 CCCAAGCTTCTATTCCTTTGCCCTCGGACGAG 
               
            
           
         
       
     
     The hph.PCR reaction system is: 
     5× phusion HF buffer 10 μL, 10 mM dNTPs 1 μL, GLT-F 2.5 μL, GLT-R 2.5 μL, cDNA 1 μL, Phusion DNA polymerase 0.5 μL, water 32.5 μL. The PCR reaction conditions are as follows: 98° C. for 30 s at first, then 98° C. for 10 s, 65° C. for 30 s, 72° C. for 1.5 min, 34 cycles, 72° C. for 10 min, and 4° C. for 10 min at last. 
     After PCR reaction, the gene was digested by XbaI and HindIII and ligated into the linearized vector pAN52-TB-Intron, which was digested by the same enzymes. The ligation product was digested with restriction endonuclease and subjected to sequencing. The sequence result shows that the nucleotide sequence of hph is shown as SEQ ID NO.: 27, which indicates that the recombinant expression plasmid carrying hph gene with correct sequence and insertion cite was obtained and named as pAN52-hph. 
     C4-dicarboxylic acid transporter encoding gene mae (XM_001820829.2, SEQ ID NO.: 11) was obtained by PCR amplication taking  Aspergillus oryzae  DSM1863 (DSMZ, purchased from German Microorganism and Cell Culture Co., Ltd.) as the template under the guidance of primers, and the gene was digested by BgIII and then ligated into linearized vector pAN52-hph which was digested by BgIII and EcoRV, the ligation product was digested with restriction endonuclease, and a vector carrying mae gene was obtained and named as pAN52-hph-mae. and the sequences of the primers are as follows: 
     
       
         
           
               
            
               
                 Mae-F: 5′(SEQ ID NO.: 43): 
               
               
                 GGAAGATCTTAATTAACTCGAGCGGCCGCGTTTAAACACTAGTATGCTG 
               
               
                   
               
               
                 ACACCTCCCAAGTTTG 
               
               
                   
               
               
                 Mae-R: 5′(SEQ ID NO.: 44): 
               
               
                 ATCCTAATCAGATACAT CCTCATCTTTA 
               
            
           
         
       
     
     Taking the genes of original strain  Myceliophthora thermophila  ATCC42464 (purchased from American Type Culture Collection) as the template, a promoter of 1.4 kb upstream of translation extension factor encoding reading frame (MYCTH_2298136) (named as Ptef promoter) was amplified by PCR and the sequence of SEQ ID NO.: 28 was amplified using primers, and the sequences of the primers are as follows: 
     
       
         
           
               
               
            
               
                   
                 Tef-F: (SEQ ID NO.: 29): 
               
               
                   
                 CCTTAATTAACATGTACCTTGACGTCCTCCGAG 
               
               
                   
                   
               
               
                   
                 Tef-R: (SEQ ID NO.: 30): 
               
               
                   
                 GGACTAGTTCTGAAGAACGAAACTGGC GACT 
               
            
           
         
       
     
     After PCR reaction, the gene was digested by PacI and SpeI and ligated into the linearized vector pAN52-hph-mae, which was digested by the same enzyme. The ligation product was digested with restriction endonuclease and verified to obtain a mae expression vector under the regulatory of promotor tef which and named as pAN52-mae. 
     The physical spectrum is shown in  FIG. 1 . 
     2, Introducing the Expression Vector (pAN52-Mae) into  Myceliophthora thermophila    
     2.1  Myceliophthora thermophila  ATCC42464 was cultured in MM slant medium [20 mL of 50× Vogel&#39;s salt, 20 g of sucrose, 15 g of agar, and 20 mL of histidine (50 mg/mL) were adjusted to 1 L and sterilized under high pressure. 50× Vogel&#39;s salt (1 L): trisodium citrate (½H 2 O) 150 g, anhydrous KH 2 PO 4  250 g, anhydrous NH 4 NO 3  100 g, MgSO 4 .7H 2 O 10 g, CaCl 2 .2H 2 O 5 g, salt solution of trace elements 5 mL and biotin (0.1 mg/mL) 2.5 mL were adjusted to 1 L] for 10 days at 45° C. to be used. 
     2.2 Protoplast Transformation of  Myceliophthora thermophila    
     1) Preparation of the Mycelium 
     Mature spores of  Myceliophthora thermophila  was collected with sterilized water containing 0.05% Tween-80. The hyphae was filtered and obtained with the lense paper and then placed on MM plates with cellophane and cultured at 45 for 14 h. 
     2) Preparation of the Protoplast 
     The cellophane with mycelium was placed in 30 mL of lysate (formulation: 0.15 g of lyase, and 30 mL of solution A was added aseptically, the product was filtered for sterilization, solution A: 1.0361 g of potassium dihydrogen phosphate and 21.864 g of sorbitol were dissolved in 90 mL of deionized water. Potassium hydroxide was used to adjust the pH to 5.6, and the product was quantified to 100 mL and sterilized at high temperature) and lysed at 28° C. for 2 h and gently shaked every 20 min. 
     Then the mixture was filtered with cellophane and centrifuged at 4° C. under 2000 rpm for 10 min. The supernatant was discarded. To the remain was added 4 mL of solution B (0.735 g of calcium chloride, 18.22 g of sorbitol and 1 mL of Tris-HCl 1M pH 7.5 was dissolved in 90 mL of deionized water. Hydrochloric acid was used to adjusted the pH to 7.6, and the product was quantified to 100 mL and sterilized at high temperature). The mixture was centrifuged at 4° C. under 2000 rpm for 10 min. The supernatant was discarded. A certain volume of solution B was added as 200 L/plasmid. 
     3) Transformation of Protoplast 
     To the pre-cooled 15 mL centrifuge tubes are sequentially added with 50 μL of pre-cooled PEG (12.5 g of PEG6000, 0.368 g of CaCl 2 , 500 μL of Tris HCl, 1M, pH, 7.5), 10 μL of plasmid pAN52-mae linearized with HindIII, and 200 μL of protoplasts. After placing on ice for 20 min, to the centrifuge tubes were added with 2 mL of precooled PEG, and the product was kept in room temperature for 5 min, then added with 4 mL of solution B and gently mixed. 3 mL of the above solution was added into 12 mL of melt MM medium with corresponding antibiotics. The mixture was placed in the plate, and cultured at 45° C. After 2 d-4 d, single mycelium was selected from the solution under the stereomicroscope and subjected to the corresponding resistant plate for growth. 
     2.3 Validation of  Myceliophthora thermophila  Transformant 
     1) Genome Extraction 
     Genomic DNAs were extracted from the transformants selected in the above transformation process, using phenol chloroform method, which includes the following operations: 
     1) To 2.0 mL sterile DNA extraction tube was added 200 mg of zirconium beads and 1 mL of lysate (lysis buffer, formula: 0.2M Tris-HCl (pH 7.5), 0.5M NaCl, 10 mM EDTA, 1% SDS (w/v)).  Myceliophthora thermophila  hyphae growing on the plate were selected and placed in DNA extraction tube. 
     2) All the DNA extraction tubes were placed on the grinding mill, which were vibrated at the maximum speed for 30 s twice. 
     3) The tubes were heated in water bath at 65° C. for 30 min, and during the process the tubes were taken out for vortex oscillation every few minutes. 
     4) The tubes were retrieved after the water bath process completed, and to each tube was added 80 μL of pH 7.5, 1M, Tris HCl for neutralization. 
     5) 400 μl of phenol was added to the tubes: chloroform (1:1), and centrifuged at 13000 rpm for 5 minutes. 
     6) 300 μL of supernatant was taken and placed into a new 1.5 mL EP tube, to which was added 600 μL of 95% ethanol (DNA grade). 
     7) The product was incubated on ice for one hour, followed by centrifugation at 4° C. at 13000 rpm, then a white DNA precipitate can be observed at the EP tube bottom. 
     8) 400 μL of 75% alcohol (DNA level) was used for washing, and the product was centrifuged at 4 degree at 13000 rpm, and the supernatant was gently removed. 
     9) The EP tube was subjected to a vacuum concentrator and vacuum dried to remove alcohol. 
     10) 50 μL of ddH 2 O was added to dissolve DNA, and NanoDrop was used to measure DNA concentration. After the measurement, the extracted DNA was put in a refrigerator at −20° C. for PCR verification in the next step. 
     2) PCR Verification of  Myceliophthora thermophila  Transformat 
     The extracted genomic DNAs were used as a template to validate the transformants with tef-F and mea-R as primers. PCR reaction system: 5× phusion GC buffer 4 μL, 10 mM dNTPs 0.2 μL, 1 μL for each primers, genome 1 μL, DMSO 0.6 μL, Phusion DNA polymerase 0.1 μL, and water 12.1 μL. PCR reaction condition: 98° C. for 30 s at first, then 98° C. for 10 s, 62° C. for 30 s, 72° C. for 1.5 min, 30 cycles, 72° C. for 10 min and 4° C. for 10 min at last. 
     3) PCR amplification products were subjected to 1% agarose gel electrophoresis (110 V voltage, 30 min). Under the gel imaging system, the gene amplified bands were observed and showed that in the guidance of the upstream primer tef-F and the downstream primer mae-R, a 2360 bp target band was obtained by PCR amplification, which indicated that the pAN52-mae linearized by hindIII was integrated into the  Myceliophthora thermophila  genome. 
     3. Determination of Malic Acid Producing Capacity of  Myceliophthora thermophila  Transformant 
     The above verified transformants were all inoculated into 50 mL of medium with crystalline cellulose (Avicel) as the carbon source in a 250 mL Erlenmeyer flask (formulation: 75 g/L of carbon source, 6.0 g/L of peptone, 0.15 g/L of KH 2 PO 4 , 0.15 g/L of K 2 HPO 4 , 0.10 g/L of CaCl 2 .2H 2 O, 0.10 g/L of MgSO 4 ,7H 2 O, 80.0 g/L of calcium carbonate, 1 mL/L 0.5 g/L biotin, and 1 ml/L of trace element solution; the formulation of the trace element solution (100 mL): 5 g of C 6 H 8 O.7H 2 O, 5 g of ZnSO 4 .7H 2 O, 1 g of Fe(NH 4 ) 2 (SO 4 ).6H 2 O, 0.25 g of CuSO 4 .5H 2 O, 0.05 g of MnSO 4 .H 2 O, 0.05 g of H 3 BO 3 , 0.05 g of NaMoO 4 .2H 2 O, dissolved in water to a volume of 100 mL) in an inoculation amount of 2.5×10 5 /mL and cultured at 45° C. in 150 rpm. On the eighth day the malic acid content was determined. 
     1) Sample Treatment: 
     1 mL of fermentation broth was placed in a 15 mL centrifuge tube, to which was added 1 mL of 1M H 2 SO 4 , and then placed at 80° C. for 30 min with full vibration every 0 min. After that 2 mL double distilled water was added to the centrifuge tube. After through vibration, 1 mL of liquid was subjected to a 1.5 mL centrifuge tube and centrifuged in 12000 rpm for 10 min. The content of C4-bicarboxylic acid was verified by measuring the supernatant. 
     2) Verification of the Content of C4-Bicarboxylic Acid 
     The content of malic acid and succinic acid in the treated sample were determined by HPLC, wherein the detector was UV detector, the mobile phase was 5 mM H 2 SO 4 , and the flow rate was 0.5 mL/min. The results showed that mae overexpression in  Myceliophthora thermophila  can significantly promote the malic acid production, in which the strains with a highest yield were named as JG141. On the eighth day, the malic acid production was 42 g/L ( FIG. 9 ), the succinic acid production was 3.86 g/L for the corresponding carbon source. The experiments showed that after the genetic modification, the fermentation of malic acid could be carried out in  Myceliophthora thermophila  by using the carbon source including crystalline cellulose. 
     Example 2 Overexpression of C4-Dicarboxylic Acid Transporter Encoding the Genes of  Myceliophthora thermophila  from Different Origins can Obtain Recombinant Microorganisms with Significant Increased Capacity for Producing Malic Acid 
     1. Homology Comparison Analysis of C4-Dicarboxylic Acid Transporter 
     In this example, C4-dicarboxylic acid transporter from  Aspergillus oryzae  NRRL3488 (AO090023000318, mae, SEQ ID NO.: 12), C4-dicarboxylic acid transporter from  Neurospora crassa  (XP_958365, NCmae, SEQ ID NO.: 14), C4-dicarboxylic acid transporter from  Trichoderma reesei  (XP_006963989, Trmae, SEQ ID NO.: 16), C4-dicarboxylic acid transporter from  Myceliophthora thermophila  (XP_003663832, Mtmae, SEQ ID NO.: 18), C4-dicarboxylic acid transporter from  Aspergillus niger  NRRL599 (XM_001398094, Anmae, SEQ ID NO.: 20), C4-dicarboxylic acid transporter from  Aspergillus sojae  NBRC4239 (Asmae, SEQ ID NO.: 22) were selected. 
     2. Construction of C4-Dicarboxylic Acid Transporter Gene Expression Vector Promoter 
     A 1.0 kb upstream promoter of the translation elongation encoding frame tef (MYCTH_2298136) was amplified by PCR from the original strain of  Myceliophthora thermophila  ATCC 42464 as a template. The reaction system and conditions were shown in Step 1 of Example 1. According to the constructed plasmids, the primers used for PCR amplification were: 
     
       
         
           
               
               
            
               
                   
                 Tef-2F: 
               
               
                   
                 (SEQ ID NO.: 55) 
               
               
                   
                 GAAGATCTCATGTACCTTGACGTCCTCCGAG 
               
               
                   
                   
               
               
                   
                 Tef-2R: 
               
               
                   
                 (SEQ ID NO.: 56) 
               
               
                   
                 GGACTAGTTCTGAAGAACGAAACTGGCGACT 
               
            
           
         
       
     
     After PCR reaction, the recombinant plasmid was digested with BgIII and SpeI and ligated into the linearized vector pAN52-TB-Intron, which was digested by the same enzyme. The ligation product was digested with restriction endonuclease and identified to obtain the recombinant vector, named as pAN52-TB-Ptef. The physical map was shown in  FIG. 2 . 
     3. Construction of C4-Dicarboxylic Acid Transporter Gene Expression Vector 
     3.1 The gene encoding C4-dicarboxylic acid transporter Ncmae (SEQ ID NO.: 13) was obtained by PCR amplification using  Neurospora crassa  (purchased from FGSC) as a template, and the primers used for PCR amplification were as follows: 
     
       
         
           
               
               
            
               
                   
                 NCmae-F: 
               
               
                   
                 (SEQ ID NO.: 45) 
               
               
                   
                 GGACTAGTATGGGCAGCCAGCCTCCCATGC 
               
               
                   
                   
               
               
                   
                 NCmae-R: 
               
               
                   
                 (SEQ ID NO.: 46) 
               
               
                   
                 CGGAATTCCTAATGATCCTCCACATCCTCA 
               
            
           
         
       
     
     3.2 The gene encoding C4-dicarboxylic acid transporter Trma(SEQ ID NO.: 15) was obtained by PCR amplification using  Trichoderma reesei  (purchased from ATCC) as a template, and the primers used for PCR amplification were as follows: 
     
       
         
           
               
               
            
               
                   
                 Trmae-F: 
               
               
                   
                 (SEQ ID NO.: 47) 
               
               
                   
                 GGACTAGTATGAAAGCGGCATTCCCTCATGC 
               
               
                   
                   
               
               
                   
                 Trmae-R: 
               
               
                   
                 (SEQ ID NO.: 48) 
               
               
                   
                 CGGAATTCTCAGTGATCCTCCACATTCTCATC 
               
            
           
         
       
     
     3.3 The gene encoding C4-dicarboxylic acid transporter Mtmae(SEQ ID NO.: 17) was obtained by PCR amplification using  Myceliophthora thermophila  ATCC42464 (purchased from ATCC) as a template, and the primers used for PCR amplification were as follows: 
     
       
         
           
               
               
            
               
                   
                 Mtmae-F: 
               
               
                   
                 (SEQ ID NO.: 49) 
               
               
                   
                 CGGACTAGTATGTCAACACCGCGGCGAAG 
               
               
                   
                   
               
               
                   
                 Mtmae-R: 
               
               
                   
                 (SEQ ID NO.: 50) 
               
               
                   
                 CCGGAATTCTTAATGATCCTCCACGTCCTC 
               
            
           
         
       
     
     3.4 The gene encoding C4-dicarboxylic acid transporter Anmae(XM_001398094)(SEQ ID NO.: 19) was obtained by PCR amplification using  Aspergillus niger  NRRL599 as a template, and the primers used for PCR amplification were as follows: 
     
       
         
           
               
               
            
               
                   
                 Anmae-F: 
               
               
                   
                 (SEQ ID NO.: 51) 
               
               
                   
                 GGACTAGTATGAACGTTGAAACGAGC 
               
               
                   
                   
               
               
                   
                 Anmae-R: 
               
               
                   
                 (SEQ ID NO.: 52) 
               
               
                   
                 CGGAATTCTCATTCAGACACATCCTCAT 
               
            
           
         
       
     
     3.5 The gene encoding C4-dicarboxylic acid transporter Asmae(SEQ ID NO.: 21) was obtained by PCR amplification using  Aspergillus sojae  NBRC4239 as a template, and the primers used for PCR amplification were as follows: 
     
       
         
           
               
               
            
               
                   
                 Asmae-F: 
               
               
                   
                 (SEQ ID NO.: 53) 
               
               
                   
                 GCTCTAGAATGCTGACACCTCCCAAGTTTGAGGATG 
               
               
                   
                   
               
               
                   
                 Asmae-R 
               
               
                   
                 (SEQ ID NO.: 54) 
               
               
                   
                 CCTTAATTAACTAATCAGATACATCCTCATCTTTACCC 
               
            
           
         
       
     
     The PCR product of C4-dicarboxylic acid transporter gene fragments obtained through PCR amplification and analysis and the plasmid pAN52EF-Intron were digested by restriction endonuclease SpeI and EcoRI. Then, they were ligated by T4 DNA ligase to obtain the expression plasmids, named as pAN52-Ptef-Ncmae, pAN52-Ptef-Trmae, pAN52-Ptef-Mtmae, pAN52-Ptef-Anmae, and pAN52-Ptef-Asmae respectively. 
     4. Analysis of Malic Acid Produced by Fermentation of  Myceliophthora thermophila  Recombinant Transformants 
     (1) The Obtain of Recombinant  Myceliophthora thermophila  Transformants 
     The constructed gene expression vectors (pAN52-Ptef-Ncmae, pAN52-Ptef-Trmae, pAN52-Ptef-Mtmae, pAN52-Ptef-Anmae, pAN52-Ptef-Asmae) were integrated into the original strains of  Myceliophthora thermophila  strains genome and use glufosinate at a final concentration of 100 μg/mL as an antibiotic for screening. The method of the example was shown in step 2 in example 1. The transformat was verified using primer tef-2F and the downstream primer corresponding to gene cloning. PCR system and methods were shown in step 1.3 in example 1. 
     All of the transformants verified were inoculated into a 250 mL conical flask containing 50 mL of medium with crystalline cellulose (Avicel) as the carbon source (see step 3 in example 1) in a inoculation amount of 2.5×10 5 /mL, then subjected to the culture at 45° C. in 150 rpm, and the sample was taken on eighth day. After the sample was treated by the method as described in step 3.2 of example 1, the malic acid content in the fermentation broth was determined. 
     The results showed that overexpression of C4-dicarboxylic acid transporter derived from different species in  Myceliophthora thermophila  can significantly promote the production of malic acid, and the malic acid yield went up to (see  FIG. 10 ): 37.9 g/L (Ncmae), 26.1 g/L (Mtmae), 16.6 g/L (Trmae), 0.24 g/L (Anmae) and 59.4 g/L (Asmae), respectively. It showed that C4-dicarboxylic acid transporter from  Neurospora crassa, Myceliophthora thermophila, Trichoderma reesei  and  Aspergillus sojae  can be used to construct  Myceliophthora thermophila  strains for malic acid fermentation in industry. But it should be noted that although C4-dicarboxylic acid transporters from  Aspergillus niger  and  Aspergillus oryzae  have a high identity (about 90%), in this experiment when the C4-dicarboxylic acid transporter from  Aspergillus niger  was overexpressed in the  Myceliophthora thermophila , the transformants did not show the capacity of producing malic acid suitable for industrial application. It can be seen that even in the  Aspergillus  strain with an ability for accumulating malic acid, the proteins with high identity failed to enable other strains have better malic acid-producing capacity. 
     For the genes derived from different strains, the inventors conducted more experiments to study whether genes from non-dominant strains for organic acids accumulation ( Neurospora crassa, Trichoderma reesei , etc.) can be used by metabolic engineering method to improve the capacity for producing dibasic acid of their own or other strains. 
     Example 3 the C4-Two Carboxylic Acid Transport Protein Coding Gene Mae and Pyruvate Carboxylase Gene Pyc are Simultaneously Expressed in the  Myceliophthora thermophila  so as to Strengthen the Ability to Produce Malic Acid 
     1. Construction of Co-Expression Vectors Containing Mae and Pyc 
     The promoters of of  Aspergillus nidulans  gpdA was amplified by PCR using the plasmid pAN52-TB-Intron as the template in the guidance of primers. The PCR conditions and system were described in step 1 of Example 1. The primer was shown as follows: 
     
       
         
           
               
            
               
                 ANgpadA-F: 
               
               
                 (SEQ ID NO.: 61) 
               
               
                 CCTTAATTAAGTCCAGATCATGGTTGACCGGTG 
               
               
                   
               
               
                 ANgpdA-R: 
               
               
                 (SEQ ID NO.: 62) 
               
               
                 GAACCTCCTTCAGAGAGGTTCGTGTTTAAACTGATGTCTGCTCAAGCGG 
               
               
                   
               
               
                 GGTA 
               
            
           
         
       
     
     Then the cellobioses hydrolase encoding gene cbh (MYCTH_109566) terminator (SEQ ID NO.: 85) was amplified by PCR using the primers and the original strain  Myceliophthora thermophila  genome as a template. The primers were shown as follows: 
     
       
         
           
               
            
               
                 CBH-F: 
               
               
                 (SEQ ID NO.: 63) 
               
               
                 ACCCCGCTTGAGCAGACATCAGTTTAAACACGAACCTCTCTGAAGGAGG 
               
               
                   
               
               
                 TTC 
               
               
                   
               
               
                 CBH-R: 
               
               
                 (SEQ ID NO.: 64) 
               
               
                 CCCAAGCTTCTAATAGGGATAATAAGCTAGGGTC 
               
            
           
         
       
     
     The gpdA promoter and cbh terminator were ligated together by fusion PCR using the method of gene overlap extension (SOE), which was invented by Horton et al. 1989 (Horton R M, Hunt H D, Ho S N, Pullen J K, Pease L R. 1989. Engineering hybrid genes without the use of restriction enzymes: gene splicing-by-overlap extension. Gene 77: 61-68). 
     The An_gpdA promoter and cbh terminator were digested by HindIII to provide adhesive ends and then ligated into pAN52-mae which was digested with the same enzyme to give the recombinant vector: pAN52-mae-PgpdA-Tcbh. 
     Pyruvate carboxylase encoding gene pyc (XM_001820829.2, SEQ ID NO.: 25) was amplified by PCR using  Aspergillus oryzae  DSM1863 cDNA as a template in the guidance of primer PYC-F (SEQ ID NO.: 57) and PYC-R (SEQ ID NO.: 58), then digested by PmeI and ligated into pAN52-mae-PgpdA-Tcbh which was digested with the same enzyme. The recombinant plasmid was verified by PCR with primers PYC-F and PYC-R, and then sequenced. The sequencing results confirmed that the sequence of the plasmid was the nucleotide sequence of pyc gene, which showed that the recombinant plasmid with the correct insertion position and carrying pyc gene was obtained and named as pAN52-mae-pyc. The physical map of the expression vector was shown in  FIG. 3 . 
     2. Determination of Malic Acid-Producing Capacity by  Myceliophthora thermophila  Transformants Fermentation Using Monosaccharides, Glycans and Biomass as a Carbon Source. 
     The coexpression vector pAN52-mae-pyc containing mae and pyc was linearized by BgIII and then integrated into the genome of the original strain  Myceliophthora thermophila , and the method was described in step 2 of example 1. The transformants were obtained and verified using peimers mae-F (SEQ ID NO.: 43) and mae-R (SEQ ID NO.: 44) (to verify mae was intergrated into the genome), PYC-F and PYC-R (to verify pyc was integrated into the genome). PCR system and conditions was shown in step 1.3 of example 1. 
     The verified transformants were all inoculated into 250 mL Erlenmeyer flask with 50 mL of medium containing glucose, D-xylose, cellobiose, xylan, crystalline cellulose, sucrose, soluble starch, corncobs xylose slag and corncobs delignification as carbon source (the formulation was shown in step 3 of example 1) and cultured in an inoculated amount of 2.5×10 5  cells/mL at 45° C. in 150 rpm and sampled on the eighth day. After the sample was treated by the method as described in step 3.2 of example 1, the malic acid content in the fermentation broth was determined. 
     The results showed that when mae and pyc were overexpressed simultaneously in  Myceliophthora thermophila , the production of malic acid was significantly promoted. One of the strains was named as JG207. On the eighth day, the yields of malic acid and succinic acid in the transformants using various carbon sources were: 62 g/L and 3.2 g/L (glucose), 28 g/L and 6.4 g/L (D-xylose), 78.7 g/L and 8.6 g/L (cellobiose), 61.3 g/L and 11 g/L (xylan), 63 g/L and 7.2 g/L (crystalline cellulose), 36.3 g/L and 4.7 g/L (sucrose), 46.3 g/L and 16.0 g/L (soluble starch), 36.8 g/L and 9.1 g/L (corncobs xylose slag), 55.15 g/L and 8.1 g/L (corncob delignification slag). 
     Example 4 Overexpressing Malate Dehydrogenase Encoding Gene Mdh in  Myceliophthora thermophila  Transformant Further Enhanced its Ability to Produce Malic Acid 
     1. Construction of Mdh Overexpression Vectors 
     The promoter PtrpC (SEQ ID NO.: 86) of the tryptophan synthase-encoding gene from  Aspergillus nidulans  was amplified under the guidance of primers using pAN52-TB-Intron as a template. The primers were shown as follows: 
     
       
         
           
               
            
               
                 Trpc-F: 
               
               
                 (SEQ ID NO.: 65) 
               
               
                 CTTTCTAGACGACGTTAACTGATATTGAAGGAGC 
               
               
                   
               
               
                 Trpc-R: 
               
               
                 (SEQ ID NO.: 66) 
               
               
                 CGTGCAATCCATCTTGTTCAATCATTTGGATGCTTGGGTAGAATAGGTAA 
               
            
           
         
       
     
     The neomycin phosphotransferase encoding gene neo (GI: 339515868) was amplified by PCR using primers and plasmid pEGFP-N2 as a template. The reaction system and conditions were shown in Step 1 of Example 1. The primers were shown as follows: 
     
       
         
           
               
            
               
                 NEO-F: 
               
               
                 (SEQ ID NO.: 67) 
               
               
                 TTACCTATTCTACCCAAGCATCCAAATGATTGAACAAGATGGATTGCACG 
               
               
                   
               
               
                 NEO-R: 
               
               
                 (SEQ ID NO.: 68) 
               
               
                 AAAAAAAGCTTGGTACCATCGATGCGGCCGCCCGCGGTCAGAAGAACTCG 
               
               
                   
               
               
                 TCAA. 
               
            
           
         
       
     
     The sequence of PtrpC and Neo were ligated together by the fusion PCR method and the specific method is gene overlap extension (SOE). 
     PtrpC and neo were digested by XbaI and HindIII to obtain sticky ends and then ligated into pAN52-TN-Intron which was digested by the same enzymes to obtain the recombinant vector with Neo as the screening marker, and the product was named as pAN52-TN. 
     The sequence of the promoter MtPgpdA at 1.5K upstream of 3-phosphoglyceraldehyde dehydrogenase-encoding gene of the original strain  Myceliophthora thermophila  was optimized to remove the restriction site, and the artificially synthesized sequence was shown as SEQ ID NO.: 69. Using the above as a template and in guidance of primers, MtPgpdA was amplified, then digested by BgIII and BamHI, and then ligated into the linearized vector pAN52-TN which was digested by the same enzyme enzymes, so as to obtain the recombinant plasmid containing gpdA promoter: pAN52-TN-MtPgpdA. The primers were shown as follows: 
     
       
         
           
               
               
            
               
                   
                 MtPgpdA-F: 
               
               
                   
                 (SEQ ID NO.: 70) 
               
               
                   
                 TGCAGATCTTTAATTAACTCGAGTGACGGTGCTTTTCACCTCTC 
               
               
                   
                   
               
               
                   
                 MtPgpdA-R: 
               
               
                   
                 (SEQ ID NO.: 71) 
               
               
                   
                 AGTGGATCCGAATTCGATATCGTTTAAACACTAGTTTTGATTTC 
               
               
                   
                   
               
               
                   
                 TGTGATGTGG 
               
            
           
         
       
     
     The malate dehydrogenase encoding gene mdh (MYCTH_2315052) in  Myceliophthora thermophila  was amplified by PCR in the guidance of primers and using the original strain of  Myceliophthora thermophila  cDNA as template. The primers were shown as follows: 
     
       
         
           
               
               
            
               
                   
                 MtMDH-F: 
               
               
                   
                 (SEQ ID NO.: 59) 
               
               
                   
                 CGGACTAGTATGGTCAAAGCTGTCGTTGCTG 
               
               
                   
                   
               
               
                   
                 MtMDH-R: 
               
               
                   
                 (SEQ ID NO.: 60) 
               
               
                   
                 CGCGGATCCTCACTTCTGGGGGGGGTTGTG. 
               
            
           
         
       
     
     After digested by SpeI and BamHI, the plasmid was ligated into linearized plasmid pAN52-TN-MtPgpdA which was digested by the same enzymes so as to obtain recombinant vector expressing mdh, named as pAN52-mdh, and the physical map of the expressing vector was shown in  FIG. 4 . 
     2. Determination of the Capacity of  Myceliophthora thermophila  Transformant for Producing Malic Acid. 
     The mdh overexpression vector pAN52-mdh was linearized by BgI II and then intergrated into the  Myceliophthora thermophila  JG207 strains genome. The final concentration was 100 μg/mL. G418 was used as the screening antibiotics. The method was shown in step 2 of example 1. The transformant was verified and contained using primers MtPgpdA-F and MtMDH-R. The PCR system and methods were described in step 1.3 of example 1. 
     All of the transformants verified were inoculated into a 250 mL conical flask containing 50 mL of medium with crystalline cellulose (Avicel) as the carbon source (see step 3 in example 1) in a inoculation amount of 2.5×10 5 /mL and subjected to culture at 45° C. in 150 rpm, and sampled on eighth day. After the sample was treated by the method as described in step 3.2 of example 1, determine the malic acid content in the fermentation broth. 
     The results showed that when mae and pyc were overexpressed in  Myceliophthora thermophila  simultaneously, the malic acid production can be significantly promoted. One of the strains was named as JG319. On the eighth day the yield of malic acid was 75 g/L ( FIG. 9 ), the yield of succinic acid was 9.3 g/L. The conversion rate of malic acid went up to 1.0 g/g Avicel. 
     Example 5 Inhibiting the Expression of Succinyl-CoA Synthase by RNA Interference to Improve the Fermentation Level of Malic Acid 
     1. The upstream promoters interfering vector construction, named as P1 and P2 promoter (SEQ ID NO.: 72 and 73), were digested with BgIII and PmeI and then ligated respectively into linearized vector pAN52-TB-Intron which was digested with the same enzymes to obtain the recombinant plasmid respectively named as pAN52-TB-Psilent-A and pAN52-TB-Psilent-B. 
     The first interference sequence SCL-S1 (SEQ ID NO. 74) of the succinyl-CoA synthase encoding gene scl in  Myceliophthora thermophila  was amplified by PCR in the guidance of primers, and the primers were shown as follows: 
     
       
         
           
               
               
            
               
                   
                 SCL1-F: 
               
               
                   
                 (SEQ ID NO.: 31) 
               
               
                   
                 CCATCGATCATCAAGAACCTGTACCGCATC 
               
               
                   
                   
               
               
                   
                 SCL1-R:, 
               
               
                   
                 (SEQ ID NO.: 32) 
               
               
                   
                 GGGTTTAAACCAATGATGGGGA, TCTTCAGGTC. 
               
            
           
         
       
     
     The second interference sequence SCL-S2 (SEQ ID NO.: 75) of the succinyl-CoA synthase encoding gene scl in  Myceliophthora thermophila  was amplified by PCR in the guidance of primers. 
     
       
         
           
               
               
            
               
                   
                 SCL2-F: 
               
               
                   
                 (SEQ ID NO.: 33) 
               
               
                   
                 CGCGGATCCCAATGATGGGGATCTTCAGGTC 
               
               
                   
                   
               
               
                   
                 SCL2-R: 
               
               
                   
                 (SEQ ID NO.: 34) 
               
               
                   
                 CGCGGATCCGTTTAAACCATCAAGAACCTGTACCGCATC.  
               
            
           
         
       
     
     Two interference sequences of scl were digested with ClaI/PmeI and BamHI respectively and then ligated into the linearized plasmids pAN52-TB-Psilent-A and pAN52-TB-Psilent-B which were digested with the same enzymes so as to obtain a binary vector of transcription element containing SCL gene interference sequence hairpin structure and screening marker bar gene: pAN52-SCLsilent-A and pAN52-SCLsilent-B. The physical maps were shown in  FIG. 5  and  FIG. 6 . 
     2, Interfering the Succinyl-CoA Synthase Expression Significantly Increased the Malic Acid-Producing Ability in Microorganisms 
     The binary vector pAN52-SCLsilent-A and pAN52-SCLsilent-B of transcription element containing the hairpin structure of the SCL gene interference sequence and screening marker bar gene were integrated into the genome of the  Myceliophthora thermophila  JG207 strain respectively. The final concentration was 100 μg/ML and glufosinate was used as screening antibiotic. The method was described in Example 1, Step 2. The transformant was obtained and verified using primers Intron-F(AGCTGTTTACTCATTATTAC, SEQ ID NO.: 76) and SCL2-R(SEQ ID NO.: 34). The PCR system and methods were described in step 1.3 of example 1. 
     All of the verified transformants were inoculated into a 250 mL conical flask containing 50 mL of medium with crystalline cellulose (Avicel) as the carbon source (see step 3 in example 1) at a inoculation amount of 2.5×10 5 /mL. The product was cultured at 45° C. in 150 rpm, and sampled on eighth day. After the sample was treated by the method as described in step 3.2 of example 1, the malic acid content in the fermentation broth was determined. 
     The results showed that the yield of the malic acid in  Myceliophthora thermophila  JG207 intergrated with pAN52-SCLsilent-A was similar to that in the original strain JG207, and the yield of malic aid was 68 g/L on the eighth day. While compared to the original strain JG207, the yield of the malic acid in  Myceliophthora thermophila  JG207 intergrated with pAN52-SCLsilent-B was improved significantly, the strain with highest yield was named as JG207S, and the final yield of the malic acid (fermented for eighth days) was 74.8 g/L ( FIG. 9 ), which was increased by 15.3%. 
     This example illustrates that the transcription of the RNA interference sequence hairpin structure regulated by the time-controlled promoter interfered the translation of the key enzymes encoding genes in the TCA cycle, thereby reducing the tricarboxylic acid cycle and significantly improving the malic acid producing ability in the microorganism. 
     Since then, the inventors used the single gene mutant of  Neurospora crassa  as a host to screen out the new key genes for producing malic acid in microorganism: aspartate aminotransferase, glutamic acid-aspartate transporter, Malic acid-alpha ketoglutarate transporter. In the following experiment, the inventors further verified these newly discovered genes which were related to the synthesis of dicarboxylic acid. 
     Example 6 Regulating Aspartate Aminotransferase in  Myceliophthora thermophila  During the Malic Acid-Aspartate Shuttle Pathway can Significantly Improve the Ability of Microorganisms to Synthesize Malic Acid 
     1. Construction of Aspartate Aminotransferase Expression Vector 
     The nucleic acid sequence C17941 (MYCTH_2314321) (SEQ ID NO.: 3) encoding aspartate aminotransferase was contained by PCR amplification using  Myceliophthora thermophila  genome as a template with primer pairs designed according to aspartate aminotransferase searched in the published genome database information (http://genome.jgi.doe.gov/Spoth2/Spoth2.home.html). After the nucleic acid sequence was digested with SpeI and EcoRI, it was ligated into linearized vector pAN52gpdA-C17941 which was digested with the same enzymes to obtain the recombinant plasmid and named as pAN52gpdA-C17941. The primers were shown as follows: 
     
       
         
           
               
               
            
               
                   
                 Cl7941-F: 
               
               
                   
                 (SEQ ID NO.: 35) 
               
               
                   
                 GGACTAGTATGGCGCCGACGTCAACAACG 
               
               
                   
                   
               
               
                   
                 Cl7941-R: 
               
               
                   
                 (SEQ ID NO.: 36) 
               
               
                   
                 CGGAATTCTCATTGCACCTCCCGAACCAC 
               
            
           
         
       
     
     2. Determination of Malic Acid-Producing Capacity of  Myceliophthora thermophila  Transformant 
     The aspartate aminotransferase overexpression vector pAN52gpdA-C17941 was intergrated into  Myceliophthora thermophila  AS2 strain (which was intergrated with  Myceliophthora thermophila  transformant of Asmae overexpression vector derived from  Aspergillus sojae , see example 2) genome, with a final concentration of 100 μg/mL and using G418 as the screening antibiotic. The method was shown in step 2 of Example 1. 
     All of the verified transformants were inoculated into a 250 mL conical flask containing 50 mL of medium with crystalline cellulose (Avicel) as the carbon source (see step 3 in example 1) at a inoculation amount of 2.5×10 5 /mL. The product was cultured at 45° C. in 150 rpm, and sampled on eighth day. After the sample was treated by the method as described in step 3.2 of example 1, the malic acid content in the fermentation broth was determined. 
     The results showed that the intergration of the aspartate aminotransferase into  Myceliophthora thermophila  AS2 can significantly promote the production of malic acid. The strain with the highest yield was named as CN201. On the eighth days the yield of malic acid was 69.2 g/L ( FIG. 9 ), which was increased by 10% compared to the control strain AS2. 
     This example illustrated that the overexpression of the gene related to malic acid-aspartic acid shuttle pathway, i.e. aspartate aminotransferase can improve the ability of microorganisms to produce malic acid. 
     Example 7 Regulating Glutamic Acid-Aspartate Transporter  Myceliophthora thermophila  During the Malic Acid-Aspartate Shuttle Pathway can Significantly Improve the Ability of Microorganisms to Synthesize Malic Acid 
     1. Construction of Glutamic Acid-Aspartate Transporter Expression Vector 
     The nucleic acid sequence C11241(MYCTH_2300593)(SEQ ID NO.: 5) encoding aspartate aminotransferase was contained by PCR amplification using  Myceliophthora thermophila  genome as a template with primer pairs designed according to glutamic acid-aspartate transporter searched in the published genome database information (http://genome.jgi.doe.gov/Spoth2/Spoth2.home.html), and the primer pairs were: 
     
       
         
           
               
               
            
               
                   
                 Cl1241-F: 
               
               
                   
                 (SEQ ID NO.: 35) 
               
               
                   
                 GGACTAGTATGTCCAAGGCCGCAACTGTC 
               
               
                   
                   
               
               
                   
                 Cl1241-R: 
               
               
                   
                 (SEQ ID NO.: 36) 
               
               
                   
                 CGGAATTCCTACGCCGTCTTTGCGTTCATC. 
               
            
           
         
       
     
     After the nucleic acid sequence was digested with SpeI and EcoRI, it was ligated into linearized vector pAN52-TN-MtPgpdA which was digested with the same enzymes to obtain the recombinant plasmid named as pAN52gpdA-C11241. 
     2. Determination of Malic Acid-Producing Capacity of  Myceliophthora thermophila  Transformant 
     The glutamic acid-aspartate transporter overexpression vector pAN52gpdA-C11241 was intergrated into  Myceliophthora thermophila  AS2 strain (which was intergrated with  Myceliophthora thermophila  transformant of Asmae overexpression vector from  Aspergillus sojae , see example 2) genome, with a final concentration of 100 μg/mL and using G418 as the screening antibiotic. The method was shown in step 2 of Example 1. 
     All of the verified transformants were inoculated into a 250 mL conical flask containing 50 mL of medium with crystalline cellulose (Avicel) as the carbon source (see step 3 in example 1) at a inoculation amount of 2.5×10 5 /mL. The product was subjected to culture at 45° C. in 150 rpm, and sampled on eighth day. 
     After the sample was treated by the method as described in step 3.2 of example 1, the malic acid content in the fermentation broth was determined. The results showed that overexpression of  Aspergillus sojae  Asme and  Myceliophthora thermophila  glutamic acid-aspartate transporter (C11241) simultaneously can significantly promote the malic acid production in  Myceliophthora thermophila . One of the strains was named as CN202, and on the eighth day the yield of malic acid was 66.9 g/L ( FIG. 9 ), which was increased by 10% compared to the control strain AS2. 
     This example illustrated that the overexpression of gene glutamic acid-aspartate transporter related to malic acid-aspartic acid shuttle pathway can improve the ability of microorganisms to produce malic acid. 
     Example 8 Gene Deletion of Malic Acid-Alpha Ketoglutarate Transporter Gene could Improve the Ability of  Myceliophthora thermophila  Strain CN2 to Produce Malic Acid 
     (1) Amplification of Malic Acid-Alpha Ketoglutarate Transporter Gene and its Upstream and Downstream Homologous Arm Nucleic Acid Fragments 
     The upstream and downstream homologous arm nucleic acid sequences of the gene encoding malic acid-alpha ketoglutarate transporter UL and DL were obtained by PCR amplification using  Myceliophthora thermophila  genome as template with the primer pairs designed according to the sequence of malic acid-alpha ketoglutarate transporter gene (MYCTH_2081554, SEQ ID NO.: 91) and its upstream and downstream homologous arm nucleic acid searched in the published genome database information (http://genome.jgi.doe.gov/Spoth2/Spoth2.home.html), and the primer pairs were: 
     
       
         
           
               
               
            
               
                   
                 Cl4837-UF: 
               
               
                   
                 (SEQ ID NO.: 39) 
               
               
                   
                 GCTCTAGATGCTTGCAGGAACTCTCTGTGAAACC 
               
               
                   
                   
               
               
                   
                 Cl4837-UR: 
               
               
                   
                 (SEQ ID NO.: 40) 
               
               
                   
                 GCGTTAACCCCACAGTTTGGAGAGACGACATCG 
               
               
                   
                   
               
               
                   
                 Cl4837-DF: 
               
               
                   
                 (SEQ ID NO.: 41) 
               
               
                   
                 CCTTAATTAATGTATATACGGGGCGAATACGAAGG 
               
               
                   
                   
               
               
                   
                 Cl4837-DR: 
               
               
                   
                 (SEQ ID NO.: 42) 
               
               
                   
                 CGGAATTCTTCCTCCTGCAAACTCAGCTTGAG.  
               
            
           
         
       
     
     UL and DL were sequenced by Beijing Liuhe Huada Gene Technology Co., Ltd. and analyzed by NCBI Blast. 
     (2) Construction of a Vector with Malic Acid-Alpha Ketoglutarate Transporter Gene-Knocked Out 
     Sur gene fragment (GI:2547090) was amplified using plasmid pPK2surGFP as a template with the following primer pairs: 
     
       
         
           
               
            
               
                 Sur-F: 
               
               
                 (SEQ ID NO.: 77) 
               
               
                 GCTCTAGAGTTAACGCGGCCGCGACTAGATCTGTGCCAACGCCACAG 
               
               
                   
               
               
                 Sur-R: 
               
               
                 (SEQ ID NO.: 78) 
               
               
                 CGGAATTCGTTTAAACTTAATTAACCGACGGAATTGAGGATATCAGTCAC 
               
            
           
         
       
     
     PCR products and plasmid pPK2barGFP were digested with restriction endonuclease XbaI and EcoRI and then ligated by T4 DNA ligase to obtain plasmid pPK2sur-barGFP. 
     The above upstream and downstream homologous arm fragments of malic acid-alpha ketoglutarate transporter gene were obtained through PCR amplification and sequencing analysis. The PCR product of the upstream homologous arm was digested with restriction endonuclease XbaI and HpaI and the PCR product of the downstream homologous arm was digested with PacI and EcoRI. The plasmid pPK2sur-barGFP was digested with the same enzymes and then ligated with the upstream and downstream homologous arms using T4 DNA ligase to obtain the knock-out vector: pPK2sur-barGFP::odc ( FIG. 7 ). 
     (3) The Vector pPK2sur-barGFP::Odc with Gene Knocked Out was Used to Transform  Myceliophthora thermophila  AS2 to Obtain Transformants 
     The transformant was verified by PCR with the primer CI4837-F2 located outside the upstream homologous arm at the 5′ end of gene of malic acid-alpha ketoglutarate transporter in  Myceliophthora thermophila  and Sur-R2 within Sur gene, the primers were as follows: 
     
       
         
           
               
               
            
               
                   
                 Cl4837-F2: 
               
               
                   
                 (SEQ ID NO.: 87) 
               
               
                   
                 CAGACTGTGTGGTTCTGCAACAGG 
               
               
                   
                   
               
               
                   
                 Sur-R2: 
               
               
                   
                 (SEQ ID NO.: 88) 
               
               
                   
                 GGCCAACAGTACGAAGCATTTCG 
               
            
           
         
       
     
     PCR results showed that CI4837-F2 and Sur-R were able to amplify fragments of 3 KB size, which indicated that the Sur gene had been replaced malic acid-alpha ketoglutarate transportermalate encoding gene C4837. 
     At the same time, the transformant genome was amplified using ORF amplified primers CI4837-F and CI4837-R of malic acid-alpha ketoglutarate transporter encoding gene doc, and the sequences of the primers were as follows: 
     
       
         
           
               
               
            
               
                   
                 Cl4837-F: 
               
               
                   
                 (SEQ ID NO.: 89) 
               
               
                   
                 ATGGCGTCAGCAAAGGAGAAGG 
               
               
                   
                   
               
               
                   
                 Cl4837-R: 
               
               
                   
                 (SEQ ID NO.: 90) 
               
               
                   
                 CTACGCCTCGCCATCCCTAATC 
               
            
           
         
       
     
     PCR result showed that no fragment was amplified by using primers CI4837-F and CI4837-R, which indicated that the obtained transformants were pure nuclei. 
     (4) Fermentation of the Transformants to Produce Malic Acid 
     250 mL triangle flask was used as a fermentation container, and the volume of the fermentation system in each was 50 mL of. The formulation of the fermentation medium of malic acid was as follows: microcrystalline cellulose 7.5%, peptone 6.0 g/L, 0.15 g/L KH 2 PO 4 , 0.15 g/L K 2 HPO 4 , 0.10 g/L CaCl 2 .2H 2 O, 0.10 g/L, MgSO 4 .7H 2 O, 80.0 g/L calcium carbonate, 1 ml/L trace elements solution (5 g NaCl, 5 g FeSO4.7H 2 O, 1 g citric acid/L water). 
     32 transformants were collected by physiological saline solution. After filtered with 2-layer lens wiping paper, the number of spores was calculated, and the inoculation amount was 2.5×10 5 /ml. The transformants were cultured at 45° C. at 150 rpm and sampled on fourth, sixth and eighth days. After the samples were treated, the malic acid content was analyzed by HPLC. One strain was named as CN203, in which the yield of malic acid was 70.5 g/L ( FIG. 9 ) on the eighth day. Compared to the control strain AS2, the yield of malic acid was increased by more than 10%. 
     Example 9 Overexpression of Glucose Transporter Gene in  Myceliophthora thermophila  can Increase Producing Capacity 
     1. Construction of Glt-1 Overexpression Vector (pAN52-Glt) 
     The glucose transporter encoding gene glt-1 (NCU01633, SEQ ID NO: 95) was amplified by PCR using cDNA under glucose condition from  Neurospora crassa  FGSC #2489 (purchased from Fungal Genetics Stock Center) as a template and primers. The primers were shown as follows: 
     
       
         
           
               
               
            
               
                   
                 GLT-F: 
               
               
                   
                 (SEQ ID NO.: 93) 
               
               
                   
                 CGGACTAGTATGGTCAAAGCTGTCGTTGCTG 
               
               
                   
                   
               
               
                   
                 GLT-R: 
               
               
                   
                 (SEQ ID NO.: 94) 
               
               
                   
                 CGCGGATCCTCACTTCTGGGGGGGGTTGTG. 
               
            
           
         
       
     
     The gene was digested with SpeI and EcoRI and then ligated into the linearized plasmid pAN52-TB-MtPgpdA which was digested with the same enzymes, so as to obtain glt-1 expression vector, named as pAN52-glt. 
     2. Introducing the Expression Vector (pAN52-Glt) into  Myceliophthora thermophila    
     The glt-1 overexpression vector pAN52-glt was linearized by BgI II and then intergrated into the  Myceliophthora thermophila  JG207 strains genome. The final concentration was 100 μg/mL. G418 was used as screening antibiotic. The method was shown in step 2 of example 1. The transformant was verified and obtained using primers MtPgpdA-F and GLT-R. The PCR system and methods were described in step 1.3 of example 1. 
     All of the verified transformants were inoculated into a 250 mL triangular flask containing 50 mL of medium with glucose and cellulose as the carbon source (see step 3 in example 1) at an inoculation amount of 2.5×10 5 /mL. The product was subjected to culture at 45° C. at 150 rpm. The sample was taken on the eighth day. After the sample was treated by the method as described in step 3.2 of example 1, the malic acid content in the fermentation broth was determined. 
     The results showed that the overexpression of glt-1 in malic acid-highly producing strain YG207 could significantly promote the capacity for producing malic acid and the strain with the strongest producing ability was named as JG207G. After four days of fermentation, the yield of malic acid was 42 g/L for glucose and 51 g/L for cellulose. Compared to the original strain JG207 (29 g/L), the yield was increased by 45% and 75%, respectively. The results showed that the overexpression of glucose transporter gene in  Myceliophthora thermophila  strain JG207 could effectively improve the capacity for producing malic acid by fermentation. 
     Example 10 Overexpression of C4-Dicarboxylic Acid Transporter in  Neurospora crassa  Failed to Obtain the Capacity for Producing Malic Acid at an Industrial Level 
     1. Construction of C4-Dicarboxylic Acid Transporter Gene Expression Vector 
     The sequence of nucleic acid encoding C4-dicarboxylic acid transporter gene Ncmae (NCU07517) (SEQ ID NO.: 13) was obtained by PCR amplification using  Neurospora crassa  genome as a template. The primers used for PCR amplification were NCU7517-F:GCTCTAGAATGGGCAGCCAGCCTCCCATGC (SEQ ID NO.: 79) and NCU7517-R:CCTTAATTAACTAATGATCCTCCACATCCTCA (SEQ ID NO.: 80). The sequence of nucleic acid encoding C4-dicarboxylic acid transporter gene mae (NCU07517) (SEQ ID NO.: 11) was obtained by PCR amplification using  Aspergillus oryzae  DSM1863 genome as a template. The primers used for PCR amplification were 
     
       
         
           
               
               
            
               
                   
                 Asmae-F: 
               
               
                   
                 (SEQ ID NO.: 53) 
               
               
                   
                 GCTCTAGAATGCTGACACCTCCCAAGTTTGAGGATG 
               
               
                   
                   
               
               
                   
                 mae-2R: 
               
               
                   
                 (SEQ ID NO.: 81) 
               
               
                   
                 CCTTAATTAACTAATCAGATACATCCTCATCTTTACCC 
               
            
           
         
       
     
     The PCR product of C4-dicarboxylic acid transporter gene fragments obtained through PCR amplification and analysis and the plasmid pMF272 were digested by restriction endonuclease XbaI and PacI (the physical spectrum was shown in  FIG. 8 ). 
     Then they were ligated by T4 DNA ligase to obtain the expression plasmid, named as pMF272-Nrmae and pMF272-mae respectively. 
     2. Integrating C4-Dicarboxylic Acid Transporter Encoding Gene into  Neurospora crassa  Genome 
     After expression vectors pMF272-Nrmae and pMF272-mae of C4-dicarboxylic acid transporter were transformed into  Neurospora crassa  FGSC9015, the verified transformants were all inoculated into 50 mL of medium in a 250 mL triangular flask containing D-glucose as the carbon source (formula: glucose 100 g/L, peptone 6.0 g/L, 0.15 g/L KH 2 PO 4 , 0.15 g/L K 2 HPO 4 , 0.10 g/L CaCl 2 .2H 2 O, 0.10 g/L MgSO 4 .7H 2 O, Calcium carbonate 80.0 g/L, and 1 ml/L trace elements solution (5 g NaCl, 5 g FeSO4.7H 2 O, 1 g citric acid/L water) at an inoculation amount of 1×10 6 /mL, and cultured at 25° C. at 200 rpm. On the fourth day, the supernatant was tested to determine the malic acid content in the fermentation broth. The results showed that when Ncmae from  Neurospora crassa  was expressed in  Neurospora crassa  FGSC9015, the highest yield of malic acid was 2.7 g/L and when mae from  Aspergillus oryzae  was expressed in  Neurospora crassa  FGSC9015, the highest yield of malic acid was 2.5 g/L. Compared to the control strain  Neurospora crassa  FGSC9015 (with a yield of 1.5 g/L), the expression of C4-dicarboxylic acid transporter was increased, but it could not meet the needs of industrial applications. 
     This experiment showed that the capacity for producing malic acid can not be effectively increased to an industrial level by modifying the malic acid synthesis pathway (such as overexpression of malate transporter) in these non-dominant strains of organic acids accumulation, such as  Neurospora crassa . Although it had been reported that in  Aspergillus  the dominant strain of organic acid accumulation, the capacity for producing malic acid can be effectively increased to an industrial level by modifying the malic acid synthesis pathway, the capacity could not be promoted to these non-dominant strains of organic acid accumulation. 
     Example 11 Overexpression of C4-Dicarboxylic Acid Transporter in  Trichoderma Reesei  Failed to Improve the Ability of Microorganisms to Produce Malic Acid 
     1. Construction of C4-Dicarboxylic Acid Transporter (SEQ ID NO.: 11) Overexpression Vector in  Aspergillus oryzae    
     Encoding reading frame mae (SEQ ID NO.: 11) of C4-dicarboxylic acid transporter gene was amplified by PCR from cDNA of  Aspergillus  DSM1863, and the primers were as follows: 
     
       
         
           
               
               
            
               
                   
                 Amae-F: 
               
               
                   
                 (SEQ ID NO.: 82) 
               
               
                   
                 TTCCAACTAGTATGCTGACACCTCCCAAG 
               
               
                   
                   
               
               
                   
                 Amae-R: 
               
               
                   
                 (SEQ ID NO.: 83) 
               
               
                   
                 AATGGTTAACCTAATCAGATACATCCTC 
               
            
           
         
       
     
     After the PCR reaction, the PCR product was digested with restriction endonuclease SpeI and HpaI and ligated into the SpeI and HpaI digestion sites of plasmid pCY01 (containing hygromycin resistance gene, and on both sides of the polyclonal digestion site are promoters of elongation factor of  Myceliophthora thermophila  and terminators of  Aspergillus  trpC) to obtain plasmid pNEO-Amae. Plasmid pNEO-Amae was transformed into  Trichoderma reesei  QM6a by protoplast method, and the obtained transformants were QM6a-Amae. 
     2. Detecting the Acid-Producing Ability of the Recombinant Strains Obtained by Overexpressing C4-Dicarboxylic Acid Transporter in  Trichoderma reesei    
     1.25×10 7  spores were inoculated to 50 mL of acid-producing medium which was the same as that described in Example, and the product was cultured in 150 rpm at 28 degrees for 8 days. 1 mL of fermentation liquid was added to the 1 mL of 2M sulfuric acid, and reacted at 80 degrees for 20 min. To the above was added 2 mL of water, and centrifuged at 14000 rpm for 10 min after mixing. The supernant was tested to determine the content of malic acid using HPLC as described in Example 1. The yield of malic acid in the original strain was 2.5±0.6 g/L and that in the transformant was 2.4±0.4 g/L. 
     The results showed that the expression of C4-dicarboxylic acid transporter in  Trichoderma reesei  failed to improve the ability for producing malic acid to industrial level. 
     This experiment showed that the capacity for producing malic acid can not be effectively increased to an industrial level by modifying the malic acid synthesis pathway (such as overexpression of malate transporter) in these non-dominant strains of organic acids accumulation, such as  Trichoderma reesei . Although it had been reported that in  Aspergillus  the dominant strain of organic acid accumulation the capacity for malic acid can not be effectively increased to an industrial level by modifying the malic acid synthesis pathway, the capacity could not be promoted to these non-dominant strains of organic acid accumulation. 
     Example 12 Overexpression of Mae and Pyc in Thermophilic Fungi  Myceliophthora heterothallica  Enables the Strain have the Ability to Produce Malic Acid 
     This example showed that when pyruvate carboxylase and C4-dicarboxylic acid transporter were expressed in  M. heterothallica , the obtained recombinant microorganisms could significantly increase malic acid-producing capacity. 
     The vector pAN52-mar-pyc expressing mae and pyc (the construction of which was described in Step 1 of Example 1) was screened to obtain several positive transformants in the protoplast transformed strain  M. heterothallica  CBS202.75 with hygromycin gene hph as the selective marker. The positive transformants were subjected to malic acid fermentation with 7.5% microcrystalline cellulose Avicel as the substrate and the medium composition was found in Example 1, Step 3. With  M. heterothallica  CBS202.75 as a reference, the yield of malic acid on the eighth day of the fermentation had been increased up to 47.4 g/L. 
     This experiment showed that the modification through metabolic engineering could significantly improve the ability to synthesize malic acid in  Trichoderma harzianum. Compared with Examples  9 and 10 of the present invention, it could be found that the modified  Myceliophthora  strains could significantly improve the organic acid (malic acid) synthesis, however, which was not predictable. 
     Example 13 Establishment of Fermentation Process to Produce Malic Acid in Recombinant  Myceliophthora thermophila    
     1. Culturing the spore: The recombinant  Myceliophthora thermophila  JG207 was fermented in 5 L fermentor (BIOTECH-5JG, Shanghai Baoxing Biological Equipment Engineering Co., Ltd.) as follows: recombinant  Myceliophthora thermophila  JG207 was inoculated into MM plate medium and the plates were placed in an incubator at 45° C. for 8 days, and spores were washed with 0.8% NaCl and 0.1% Tween-80 and counted. 
     2. Culturing the seed liquid: 2.5×10 7  spores were transferred to a 250 mL triangle flask containing 100 mL of seed medium, which was cultured at 45° C. in 150 rpm for 24 h and then the obtained liquid was taken as the seed for fermentation. The seeds were fermented using a synthetic medium. In a 5 L fermentation tank was loaded with 3.3 L fermentation medium and 400 mL seed liquid. 
     The composition of MM solid medium (per liter) was 20 g sucrose, 20 mL 50× Vogel&#39;s salt, and 15 g agar. The composition of 50× Vogel&#39;s salt (g/L) was: 125 g Na 3 citrate. 2H 2 O, 250 g KH 2 PO 4 , 100 g NH 4 NO 3 , 10 g MgSO 4 .7H 2 O, 0.1 g CaCl 2 . 2H 2 O, 5 mL trace element solution, 2.5 mL Biotin, and 755 mL water. 
     The composition of seed medium (per liter) was 10 g glucose, 0.15 g K 2 HPO 4 , 0.15 g KH 2 PO 4 , 0.1 g MgSO 4 .7H 2 O, 0.1 g CaC12, 6 g Bacto, peptone, 1 mL trace element solution. The composition of trace element solutions (g/L) was: 5 g, Citric acid. 1H 2 O, 5 g ZnSO 4 .7H 2 O, 1 g Fe(NH 4 ) 2 (SO 4 ) 2 .6H 2 O, 0.25 g CuSO 4 .5H 2 O, 0.05 g MnSO 4 .1H 2 O, 0.05 g, H 3 BO 3 , and 0.05 g Na 2 MoO 4 .2H 2 O. 
     The composition of fermentation medium (per liter) was: 75 g carbon source, 80 g CaCO 3 , 0.15 g K 2 HPO 4 , 0.15 g KH 2 PO 4 , 0.1 g MgSO 4 .7H 2 O, 0.1 g CaCl 2 , 6 g Bacto peptone, 0.5 mL Biotin, and 1 mL trace element solution. 
     The composition of feeding medium (per liter) was 0.45 g K 2 HPO 4 , 0.45 g KH 2 PO 4 , 0.3 g MgSO 4 .7H 2 O, 0.3 g CaCl 2 , 18 g Bacto peptone, 1.5 mL Biotin, and 3 mL trace element solutions. 
     3. Fermentation process: fermentation temperature 45° C., air flow rate 4 L/min, and the dissolved oxygen was control at 30%. In order to control the dissolved oxygen at 30%, the speed needed to be coupled with the dissolved oxygen, and kept at 200-800 rpm. During the fermentation process calcium carbonate was added to control pH at more than 6. 
     In the 48th hour during fermentation the feeding medium was fed through simulated exponential feeding method with an average feeding rate of 8 mL/h. In the 72 h, 96 h, 120 h, 144 h, 168 h, 192 h, 216 h, and 240 h during the fermentation, 60 g of carbon source was supplemented respectively. 
     After being fermented for 48 h, every 24 h 1 mL of bacteria liquid was taken and 1 mL of 2M H 2 SO 4  was added, the mixture was mixed and then treated at high temperature of 80 for 25 min, then to the mixture was add 1 mL of sterile water. The mixture was centrifuged in 14000 rpm for 10 min. The supernatant was tested to determine the content of malic acid using HPLC (Waters e2695 HPLC). 
     The fermentation cycle is 240 h-264 h and the yield of malic acid can be increased continuously. 
     The method for producing malic acid by fermentation in recombinant  Myceliophthora thermophila  strains can be conducted with a variety of carbon sources as substrate and was consistent with the above methods. The yield of malic acid was 230 g/L with glucose as the carbon source. The yield of malic acid was 168 g/L with Avicel as the carbon source. The yield of malic acid was 95 g/L with corn stalk as the carbon source. 
     Example 14 Separation and Preparation of Malic Acid 
     The separation and preparation of malic acid was generally divided into three steps: extraction of crude malic acid, refinement, and crystallization. 
     1. Extraction of crude malic acid: the fermentation broth was processed by six steps such as acid hydrolysis, filtration, neutralization, filtration, acid hydrolysis and filtration, so as to obtain the crude malic acid solution. The fermentation broth was put in the acid hydrolysis tank, and then adjusted to pH1.6 using sulfuric acid, and the acid hydrolysis should be carried out with stirring. After the acid hydrolysis was completed, the gypsum slag, bacteria and other precipitates were filtered by plate-and-frame filter press. The filtrate was put in the neutralization tank, and adjusted to pH 7.5 by adding CaCO 3  solid and lime milk. The neutralization liquid was placed in the settling tank for 7 h to allow the calcium malate in the solution crystallize sufficiently. After the above calcium salt system was clear, the supernatant was removed. Then theremain was filtered by releasing the filter tank bottom, and the cake was washed with a small amount of cold water to remove most of the soluble impurities. The calcium malate was transferred into the acid hydrolysis tank, to which was added 2 times the weight of warm water. The mixture was stirred into a suspension, adjusted to pH 1.6 by adding sulfuric acid, stirred sequentially for about half an hour, and then stood for several hours, so that the precipitation of gypsum slag was fully precipitated. The gypsum slag in the above system was filtered by the pressure filter. The filtrate was crude malic acid solution containing trace succinic acid and other organic acids, as well as Ca 2+ , Mg 2+  and other metal ions and pigments, and would be refined in the next step. 
     2. The refinement of malic acid: ion exchange and activated carbon were combined used for the treatment. The mother liquid of malic acid was successively purified by 5-column purification system comprising CAL granular activated carbon decolorization column, cation exchange resin 732, anion exchange resin D315, BPL column activated carbon adsorption column and cation exchange resin. During the processing, the crude malic acid solution passed through the 5 column system in sequence, and the liquid flew top-down with a flow rate of 7 to 8 L/min. The effluent was tested to monitor the unsaturated fatty acid content by an ultraviolet absorption analyzer. If there was unsaturated fatty acid in the effluent, it should be reprocessed to the anion exchange resin D315 column. The CAL granular activated carbon decolorization column was used for decoloration and removing some unsaturated fatty acids. Cation exchange resin 732 was used to remove metal ions. Anion exchange resin D315 was used to remove succinic acid and other anions. 
     The malic acid solution with high purity was reduced and concentrated at 70° C. Then it was cooled down to 20° C., and some crystal seeds were added and crystallization was conducted with slow stirring. After 3 h, malic acid was crystallized. 
     The malic acid crystals was dried under vacuum at a temperature controlled between 40˜50° C. 
     Example 15 the Transformation of Wild Strains with Organic Acid Accumulation Ability and the Detection of their Capacity for Producing Organic Acid 
     In this study, vectors overexpressing malate dehydrogenase, aspartate aminotransferase and glutamic acid-aspartate transporter were constructed respectively and were used to transfer  Aspergillus  (including  Aspergillus niger, Aspergillus sojae, Aspergillus oryzae ) possessing capacity for accumulating organic acid to obtain multiple transformants and glucose was used as the reaction substrate. The method was shown as the method for the combination of construction of each transformant described in the above examples. Their products and yields were identified. Among them, the numbers of the engineered strains upon transformation and the products were shown in table 3: 
     
       
         
           
               
               
               
             
               
                 TABLE 3 
               
               
                   
               
               
                 Name of the 
                   
                 original 
               
               
                 engineered strain 
                 Characteristics of the engineered strain 
                 strain 
               
               
                   
               
             
            
               
                 PM101 
                 overexpression of malate dehydrogenase 
                 
                   Aspergillus 
                 
               
               
                   
                   
                 
                   oryzae 
                 
               
               
                 PM102 
                 Overexpression of malate 
                 
                   Aspergillus 
                 
               
               
                   
                 dehydrogenase + aspartate aminotransferase 
                 
                   oryzae 
                 
               
               
                 PJ103 
                 overexpression of malate dehydrogenase 
                 
                   aspergillus 
                 
               
               
                   
                   
                 
                   sojae 
                 
               
               
                 TJ104 
                 Overexpression of aspartate 
                 
                   aspergillus 
                 
               
               
                   
                 aminotransferase 
                 
                   sojae 
                 
               
               
                 GJ105 
                 Overexpression of glutamic acid-aspartate 
                 
                   aspergillus 
                 
               
               
                   
                 transporter 
                 
                   sojae 
                 
               
               
                 GM106 
                 Overexpression of glutamic acid-aspartate 
                 
                   Aspergillus 
                 
               
               
                   
                 transporter 
                 
                   oryzae 
                 
               
               
                   
               
            
           
         
       
     
     The identification results showed that after the corresponding genes were transformed, the capacity for producing malic acid in  Aspergillus sojae  and  Aspergillus oryzae  had been significantly improved, reaching more than 20-60 g/L respectively, wherein the PM102 strain with two genes transformed provided better performance. 
     Therefore, the gene modification of the invention could significantly improve the acid-producing capacity of the strain which had an accumulation effect for dibasic acid in its original strain. 
     Discussion 
     For the fermentation of organic acids such as malic acid, the traditional dominant strains are  Aspergillus  strains (preferably  Aspergillus niger -citric acid, itaconic acid- Aspergillus terreus , malic acid- Aspergillus flavus, Aspergillus oryzae ) and  Rhizopus  strains ( Rhizopus oryzae -lactic acid), while  Trichoderma  and  Neurospora  strains do not belong to the strains that commonly accumulating organic acid. The test has showed that for these strains without significant accumulation of organic acids under the natural conditions, it usually can not effectively improve the production to an industrial level (10 g/L or more) by modifying their organic acid (such as malic acid) synthetic pathway. It has showed that this conclusion can not be applied to the entire filamentous fungi although the modification of synthetic pathway of organic acids in  Aspergillus  has significantly improved the synthesis of organic acids, especially for those non-organic acid accumulation strains, including  Myceliophthora . it can not be speculated if they have the capacity to synthesize the organic acid at an industrial level. More specific experimental researches are needed. It was unexpected that the inventors of the present invention had firstly demonstrated that  Myceliophthora  strain did not accumulate organic acids in a large amount (usually no more than grams/liter) in the culture medium under natural conditions but can provide industrialized malic acid fermentation ability (10-100 g/I and above) after transformation. Therefore, the present invention has great contingency and innovativeness. 
     Meanwhile, the inventors have found that not only the malic acid (and even organic acid) fermentation in  Myceliophthora  can be enhanced through regulating multiple new genes, but also the organic acid-producing capacity of strains including  Aspergillus  (preferably  Aspergillus oryzae, Aspergillus sojae ) and so on (beside  Myceliophthora  with accumulation ability of the organic acid) can be improved by genetic modification. 
     In addition, the inventors have established and optimized the high temperature fermentation process of  Myceliophthora thermophila , including the fermentation feeding process by using solid biomass such as glucose and other soluble sugar fermentation process and cellulose and the like as the carbon source. 
     All documents mentioned in the present invention are incorporated herein by reference, as if each document were individually recited for reference. It should be understood that those skilled in the art will be able to make various changes or modifications to the present invention after reading the teachings of the present invention, which also fall within the scope of the claims appended hereto.