Patent Description:
In the recent years people's lifestyle and the growing consumption of food products with high sugar content has resulted in a tremendous rise of blood glucose related diseases and disorders, such as diabetes mellitus type <NUM> (DMT2). Nowadays, a low-glycaemic nutrition and the avoidance of excessive peaks in blood glucose level is considered to reduce the risk for developing certain chronic diseases and to be beneficial for maintenance and improvement of health and for the treatment and/or prevention of a large number of blood glucose related diseases and disorders.

Erythritol is a naturally occurring four-carbon sugar alcohol gaining increasing importance in the food industry due to its specific properties and its manifold fields of application. It can be found in several fruits, such as pears, grapes and melons, mushrooms, alcoholic drinks (beer, wine, sake) and fermented food products, such as soy sauce and miso bean paste, but naturally also occurs in biofluids of humans and animals such as eye lens tissue, serum, plasma, fetal fluid and urine. Due to its small molecular weight, erythritol is easily absorbed already in the upper intestine and therefore causes less digestive distress than other sugar alcohols used in the food industry. The majority of ingested erythritol is not metabolized in the human body and is excreted unmodified into the urine without changing blood glucose and insulin levels (<NPL>). Furthermore, erythritol is non-cariogenic, thermally stable, crystalizes well and is less hygroscopic than sucrose. Due to the negative enthalpy of dissolution, the consumption of erythritol causes a cooling sensation in the oral cavity. A <NUM>% (w/v) solution of erythritol has <NUM>-<NUM>% of the sweetness of sucrose at the same concentration.

However, in contrast to other sugar alcohols, such as sorbitol, xylitol, mannitol, lactitol, and maltitol, which are well-established as sugar alternatives for many years, so far erythritol cannot be chemically produced in a commercially worthwhile way. The production of erythritol from dialdehyde starch using a nickel catalyst at high temperatures results in unsatisfying low yields (<NPL>).

In yeast and fungus species, erythritol is produced via the so-called pentose phosphate pathway. It is synthesized from D-erythrose-<NUM>-phosphate through dephosphorylation and subsequent reduction of erythrose. Based thereon, the suitability of osmophilic yeast, such as Aureobasidium sp. , Trichosporonoides sp. and Candida magnoliae, for the biotechnological production of erythritol has been investigated in several studies (<NPL>); <CIT>; <CIT>; <NPL>; <NPL>; <NPL>). More recent studies examined the potential of filamentous fungi to produce erythritol (Jovanovic et al. <NPL>) describes the generation and selection of mutant strains derived from the erythritol producer strain Penicillium sp. KJ81 as well as the optimization of the conditions used for cultivation with the purpose of improving erythritol productivity. <NPL>) discloses the production of erythritol from wheat straw using Trichoderma reesei. <CIT> teaches processing of biomass feedstock materials, in particular cellulosic and lignocellulosic materials, using microorganisms to produce erythritol. <CIT> discloses the use of erythrose reductase which can be derived from Hypocrea, Gibberella, Aspergillus and Penicillium for the conversion of erythrose to erythritol. <NPL>) investigated the metabolic fluxes and the erythritol production of Aspergillus nidulans using CreA mutant strains. <CIT> is directed to a method for the isolation of highly pure erythritol produced by the bacterial strain Aureobasidium SN-G42. However, the yields of erythritol obtained from the different strains was unsatisfactory for industrial scale production.

Accordingly, there is a need for a biotechnological method for the production of erythritol with increased yield. The present invention overcomes the disadvantages of the methods in the prior art by the subject-matter of the independent claims, in particular by the method for the production of erythritol according to the present invention.

The present invention in particular pertains to a method for the production of erythritol, comprising the steps:.

wherein the carbon source is a monomeric or oligomeric C-<NUM> sugar or a mixture thereof, wherein the C-<NUM> sugar is selected from the group consisting of glucose and fructose.

In a preferred embodiment of the present invention, the culture medium comprises the carbon source in a concentration of at least <NUM>/L.

In a further preferred embodiment of the present invention, the culture medium comprises the carbon source in a concentration of at most <NUM>/L, preferably at most <NUM>/L.

According to a preferred embodiment of the present invention, the culture medium comprises the carbon source in a concentration of <NUM> to <NUM>/L, preferably <NUM> to <NUM>/L.

In a further preferred embodiment of the present invention, the culture medium comprises the nitrogen source in a concentration of at least <NUM>, preferably at least <NUM>, preferably at least <NUM>, preferably at least <NUM>, preferably at least <NUM>.

Preferably, the culture medium comprises the nitrogen source in a concentration of at most <NUM>, preferably at most <NUM>, preferably at most <NUM>, preferably at most <NUM>, preferably at most <NUM>, preferably at most <NUM>.

Particularly preferred, the culture medium comprises the nitrogen source in a concentration of <NUM> to <NUM>, preferably <NUM> to <NUM>, preferably <NUM> to <NUM>, preferably <NUM> to <NUM>, preferably <NUM> to <NUM>.

According to preferred embodiment of the present invention, the culture medium is a synthetic medium. Preferably, the culture medium is not a synthetic medium.

In a further preferred embodiment of the present invention, the culture medium comprises a hydrolysate obtained by hydrothermal treatment of a cellulose-, and/or starch-comprising raw material.

Particularly preferred, the culture medium comprises a lignocellulose-comprising hydrolysate.

In a further preferred embodiment of the present invention, the hydrolysate, preferably the hydrolysate obtained by hydrothermal treatment of a cellulose-, and/or starch-comprising raw material, in particular the lignocellulose-comprising hydrolysate, is derived from agro-industrial residues.

According to preferred embodiment of the present invention, the culture medium comprises a hydrolysate of straw, in particular a hydrolysate of wheat straw. In a further preferred embodiment, the culture medium comprises a hydrolysate of wheat bran. Preferably, the culture medium comprises a hydrolysate of potato pulp.

According to the present invention, the carbon source is a monomeric or oligomeric C-<NUM> sugar or a mixture thereof, wherein the monomeric or oligomeric C-<NUM> sugar is selected from glucose and fructose. According to a preferred embodiment, the carbon source is a mixture of monomeric and oligomeric C-<NUM> sugars selected from glucose and fructose.

In a further preferred embodiment, the carbon source is glucose.

According to a preferred option, the C-<NUM> sugar content in the culture medium amounts to at least <NUM> %, preferably at least <NUM> %, preferably at least <NUM> %, preferably at least <NUM> %, preferably at least <NUM> %, preferably at least <NUM> %, preferably at least <NUM> %, preferably at least <NUM> %, preferably at least <NUM> %, preferably at least <NUM> %, preferably at least <NUM> %, preferably at least <NUM> %, preferably at least <NUM> %, preferably at least <NUM> % (based on total carbohydrates in the culture medium).

Preferably, the C-<NUM> sugar content in the culture medium amounts to at least <NUM> %, preferably at least <NUM> %, preferably at least <NUM> %, preferably at least <NUM> %, preferably at least <NUM> %, preferably at least <NUM> %, preferably at least <NUM> %, preferably at least <NUM> %, preferably at least <NUM> %, preferably at least <NUM> %, preferably at least <NUM> %, preferably at least <NUM> %, preferably at least <NUM> % (based on total carbohydrates in the culture medium).

According to a preferred option, the glucose content in the culture medium amounts to at least <NUM> %, preferably at least <NUM> %, preferably at least <NUM> %, preferably at least <NUM> %, preferably at least <NUM> %, preferably at least <NUM> %, preferably at least <NUM> %, preferably at least <NUM> %, preferably at least <NUM> %, preferably at least <NUM> %, preferably at least <NUM> %, preferably at least <NUM> %, preferably at least <NUM> % (based on total carbohydrates in the culture medium).

According to another preferred option, the xylose content in the culture medium amounts to at least <NUM> %, preferably at least <NUM> %, preferably at least <NUM> %, preferably at least <NUM> %, preferably at least <NUM> %, preferably at least <NUM> %, preferably at least <NUM> %, preferably at least <NUM> %, preferably at least <NUM> %, preferably at least <NUM> %, preferably at least <NUM> %, preferably at least <NUM> %, preferably at least <NUM> % (based on total carbohydrates in the culture medium).

Preferably, the content of monomeric C-<NUM> and C-<NUM> sugars in the culture medium amounts to at least <NUM> %, preferably at least <NUM> %, preferably at least <NUM> %, preferably <NUM> %, preferably at least <NUM> %, preferably at least <NUM> %, preferably at least <NUM> %, preferably at least <NUM> %, preferably at least <NUM> %, preferably at least <NUM> %, preferably at least <NUM> %, preferably at least <NUM> %, preferably at least <NUM> %, preferably at least <NUM> %, preferably at least <NUM> %, preferably at least <NUM> %, preferably at least <NUM> %, preferably at least <NUM> %, preferably at least <NUM> %, preferably at least <NUM> %, preferably at least <NUM> %, preferably at least <NUM> %, preferably at least <NUM> %, preferably at least <NUM> %, preferably at least <NUM> % (based on total carbohydrates in the culture medium).

According to a preferred option, the content of oligomeric C-<NUM> and C-<NUM> sugars in the culture medium amounts to at least <NUM> %, preferably at least <NUM> %, preferably at least <NUM> %, preferably at least <NUM> %, preferably at least <NUM> %, preferably at least <NUM> %, preferably at least <NUM> %, preferably at least <NUM> %, preferably at least <NUM> %, preferably at least <NUM> %, preferably at least <NUM> %, preferably at least <NUM> %, preferably at least <NUM> %, preferably at least <NUM> %, preferably at least <NUM> %, preferably at least <NUM> % (based on total carbohydrates in the culture medium).

In a preferred embodiment of the present invention, the nitrogen source is urea.

According to the present invention, the at least one saprotroph is a filamentous fungus selected from the genera Hypocrea and Trichoderma.

In a preferred embodiment, the saprotroph is Hypocrea jecorina (Trichoderma reesei).

According a preferred option, the at least one saprotroph is a naturally occurring saprotroph, in particular is not a genetically modified saprotroph.

According to another preferred option, the at least one saprotroph is genetically modified.

In a particularly preferred option, the genetically modified saprotroph is Hypocrea jecorina (Trichoderma reesei). Preferably, the genetically modified saprotroph is based on the Trichoderma reesei strain QM6aΔtmus53.

Preferably, the at least one genetically modified saprotroph comprises at least one gene encoding at least one membrane-bound alditol transporter, at least one gene encoding at least one erythrose reductase and at least one inactivated gene encoding mannitol <NUM>-phosphate <NUM>-dehydrogenase.

Preferably, the at least one gene of the genetically modified saprotroph encoding at least one membrane-bound alditol transporter is fps1, in particular codon-optimized fps1. Preferably, the at least one gene of the genetically modified saprotroph encoding at least one membrane-bound alditol transporter is fps1 from Saccharomyces cerevisiae, in particular is codon-optimized fps1 from Saccharomyces cerevisiae.

Preferably, the at least one gene of the genetically modified saprotroph encoding at least one membrane-bound alditol transporter comprises the nucleotide sequence of SEQ ID No. <NUM>, in particular consists of the nucleotide sequence of SEQ ID No. <NUM>.

Preferably, the at least one gene of the genetically modified saprotroph encoding at least one membrane-bound alditol transporter comprises a nucleotide sequence having at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, sequence identity to SEQ ID No. <NUM>. Preferably, the at least one gene of the genetically modified saprotroph encoding at least one membrane-bound alditol transporter consists of a nucleotide sequence having at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, sequence identity to SEQ ID No. <NUM>.

Preferably, the membrane-bound alditol transporter of the genetically modified saprotroph comprises the amino acid sequence of SEQ ID No. <NUM>, in particular consists of the amino acid sequence of SEQ ID No. <NUM>.

Preferably, the membrane-bound alditol transporter of the genetically modified saprotroph comprises an amino acid sequence having at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, sequence identity to SEQ ID No. <NUM>. According to another preferred option, the membrane-bound alditol transporter of the genetically modified saprotroph consists of an amino acid sequence having at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, sequence identity to SEQ ID No. <NUM>.

According to another preferred option, the membrane-bound alditol transporter of the genetically modified saprotroph comprises an amino acid sequence as defined in SEQ ID No. <NUM>, in which one, preferably two, preferably three, preferably five, preferably six, preferably seven, preferably eight, preferably nine, preferably ten, amino acids are exchanged by other naturally occurring amino acids. Particularly preferred, the membrane-bound alditol transporter of the genetically modified saprotroph comprises an amino acid sequence as defined in SEQ ID No. <NUM>, in which at most ten, preferably at most nine, preferably at most eight, preferably at most seven, preferably at most six, preferably at most five, preferably at most four, preferably at most three, preferably at most two, preferably at most one, amino acids are exchanged by other naturally occurring amino acids.

Preferably, the at least one gene of the genetically modified saprotroph encoding at least one erythrose reductase is err1, in particular is codon-optimized err1. Preferably, the at least one gene of the genetically modified saprotroph encoding at least one erythrose reductase is err1, in particular is codon-optimized err1, from Trichoderma reesei, Aspergillus niger or Fusarium graminearum.

Preferably, the at least one gene of the genetically modified saprotroph encoding at least one erythrose reductase comprises the nucleotide sequence of SEQ ID No. <NUM>, in particular consist of the nucleotide sequence of SEQ ID No. <NUM>.

Preferably, the at least one gene of the genetically modified saprotroph encoding at least one erythrose reductase comprises a nucleotide sequence having at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, sequence identity to SEQ ID No. <NUM> According to another preferred option, the at least one gene of the genetically modified saprotroph encoding at least one gene encoding at least one erythrose reductase consists of a nucleotide sequence having at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, sequence identity to SEQ ID No. <NUM>.

Preferably, the erythrose reductase of the genetically modified saprotroph comprises the amino acid sequence of SEQ ID No. <NUM>, in particular consists of the amino acid sequence of SEQ ID No. <NUM>.

Preferably, the erythrose reductase of the genetically modified saprotroph comprises an amino acid sequence having at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, sequence identity to SEQ ID No. <NUM>. Particularly preferred, the erythrose reductase of the genetically modified saprotroph consists of an amino acid sequence having at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, sequence identity to SEQ ID No. <NUM>.

Preferably, the erythrose reductase of the genetically modified saprotroph comprises an amino acid sequence as defined in SEQ ID No. <NUM>, in which one, preferably two, preferably three, preferably five, preferably six, preferably seven, preferably eight, preferably nine, preferably ten, amino acids are exchanged by other naturally occurring amino acids. Preferably, the erythrose reductase of the genetically modified saprotroph comprises an amino acid sequence as defined in SEQ ID No. <NUM>, in which at most ten, preferably at most nine, preferably at most eight, preferably at most seven, preferably at most six, preferably at most five, preferably at most four, preferably at most three, preferably at most two, preferably at most one, amino acids are exchanged by other naturally occurring amino acids.

According to a preferred option, the at least one inactivated gene encoding mannitol <NUM>-phosphate <NUM>-dehydrogenase of the genetically modified saprotroph is mpdh. Preferably, the at least one gene encoding mannitol <NUM>-phosphate <NUM>-dehydrogenase of the genetically modified saprotroph comprised the nucleotide sequence of SEQ ID No. <NUM> before inactivation, in particular consisted of the nucleotide sequence of SEQ ID No. <NUM> before inactivation.

Preferably, the at least one gene encoding mannitol <NUM>-phosphate <NUM>-dehydrogenase of the genetically modified saprotroph comprised a nucleotide sequence having at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, sequence identity to SEQ ID No. <NUM> before inactivation. According to another preferred option, the at least one gene encoding mannitol <NUM>-phosphate <NUM>-dehydrogenase of the genetically modified saprotroph consisted of a nucleotide sequence having at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, sequence identity to SEQ ID No. <NUM> before inactivation.

Preferably, the mannitol <NUM>-phosphate <NUM>-dehydrogenase encoded by the nucleotide sequence of SEQ ID No. <NUM> before inactivation comprises the amino acid sequence of SEQ ID No. <NUM>, in particular consists of the amino acid sequence of SEQ ID No. <NUM>.

According to another preferred option, the mannitol <NUM>-phosphate <NUM>-dehydrogenase encoded by the nucleotide sequence of SEQ ID No. <NUM> before inactivation comprises an amino acid sequence having at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, sequence identity to SEQ ID No. <NUM>. Particularly preferred, the mannitol <NUM>-phosphate <NUM>-dehydrogenase encoded by the nucleotide sequence of SEQ ID No. <NUM> before inactivation consists of an amino acid sequence having at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, sequence identity to SEQ ID No. <NUM>.

Preferably, the mannitol <NUM>-phosphate <NUM>-dehydrogenase encoded by the nucleotide sequence of SEQ ID No. <NUM> before inactivation comprises an amino acid sequence as defined in SEQ ID No. <NUM>, in which one, preferably two, preferably three, preferably five, preferably six, preferably seven, preferably eight, preferably nine, preferably ten, amino acids are exchanged by other naturally occurring amino acids. Preferably, the mannitol <NUM>-phosphate <NUM>-dehydrogenase encoded by the nucleotide sequence of SEQ ID No. <NUM> before inactivation comprises an amino acid sequence as defined in SEQ ID No. <NUM>, in which at most ten, preferably at most nine, preferably at most eight, preferably at most seven, preferably at most six, preferably at most five, preferably at most four, preferably at most three, preferably at most two, preferably at most one, amino acids are exchanged by other naturally occurring amino acids.

According to a further preferred option, the at least one inactivated gene encoding mannitol <NUM>-phosphate <NUM>-dehydrogenase of the genetically modified saprotroph is deleted.

Preferably, the at least one inactivated gene encoding mannitol <NUM>-phosphate <NUM>-dehydrogenase of the genetically modified saprotroph is non-functional.

Particularly preferred, the at least one inactivated gene encoding mannitol <NUM>-phosphate <NUM>-dehydrogenase of the genetically modified saprotroph is inactivated by gene knock-out, in particular gene replacement. Preferably, the at least one inactivated gene encoding mannitol <NUM>-phosphate <NUM>-dehydrogenase of the genetically modified saprotroph is inactivated by gene replacement using a deletion cassette.

Preferably, the at least one gene encoding mannitol <NUM>-phosphate <NUM>-dehydrogenase of the genetically modified saprotroph is inactivated, in particular made non-functional, by genome editing, in particular by meganucleases, zinc-finger nucleases (ZFNs), transcription activator-like effector nucleases (TALENs) or by the clustered regularly interspaced short palindromic repeats (CRISPR) system.

Particularly preferred, the genetically modified saprotroph comprises at least one, preferably at least two, preferably at least three, preferably at least four, preferably at least five, further inactivated genes. Preferably, the at least one further inactivated gene of the genetically modified saprotroph is selected from the group consisting of a gene encoding phospho-<NUM>-dehydro-<NUM>-deoxyheptonate aldolase <NUM> (Dhaps-<NUM>), a gene encoding erythritol utilization factor (EUF), a gene encoding erythrulose kinase (EYK1), a gene encoding erythritol dehydrogenase (EYD1), a gene encoding erythritol isomerase <NUM> (EYI1) and a gene encoding erythritol isomerase <NUM> (EYI2).

Preferably, the at least one further inactivated gene of the genetically modified saprotroph is a gene encoding phospho-<NUM>-dehydro-<NUM>-deoxyheptonate aldolase <NUM> (Dhaps-<NUM>). Preferably, the at least one gene encoding phospho-<NUM>-dehydro-<NUM>-deoxyheptonate aldolase <NUM> (Dhaps1) of the genetically modified saprotroph comprised the nucleotide sequence of SEQ ID No. <NUM> before inactivation, in particular consisted of the nucleotide sequence of SEQ ID No. <NUM> before inactivation.

Preferably, the at least one gene encoding phospho-<NUM>-dehydro-<NUM>-deoxyheptonate aldolase <NUM> (Dhaps1) of the genetically modified saprotroph comprised a nucleotide sequence having at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, sequence identity to SEQ ID No. <NUM> before inactivation. Further preferably, the at least one gene encoding phospho-<NUM>-dehydro-<NUM>-deoxyheptonate aldolase <NUM> (Dhaps1) of the genetically modified saprotroph consisted of a nucleotide sequence having at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, sequence identity to SEQ ID No. <NUM> before inactivation.

Preferably, the phospho-<NUM>-dehydro-<NUM>-deoxyheptonate aldolase <NUM> (Dhaps1) encoded by the nucleotide sequence of SEQ ID No. <NUM> before inactivation comprises the amino acid sequence of SEQ ID No. <NUM>, in particular consists of the amino acid sequence of SEQ ID No. <NUM>.

Preferably, the phospho-<NUM>-dehydro-<NUM>-deoxyheptonate aldolase <NUM> (Dhaps1) encoded by the nucleotide sequence of SEQ ID No. <NUM> before inactivation comprises an amino acid sequence having at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, sequence identity to SEQ ID No. <NUM>. Particularly preferred, the phospho-<NUM>-dehydro-<NUM>-deoxyheptonate aldolase <NUM> (Dhaps1) encoded by the nucleotide sequence of SEQ ID No. <NUM> before inactivation consists of an amino acid sequence having at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, sequence identity to SEQ ID No. <NUM>.

Preferably, the phospho-<NUM>-dehydro-<NUM>-deoxyheptonate aldolase <NUM> (Dhaps1) encoded by the nucleotide sequence of SEQ ID No. <NUM> before inactivation comprises an amino acid sequence as defined in SEQ ID No. <NUM>, in which one, preferably two, preferably three, preferably five, preferably six, preferably seven, preferably eight, preferably nine, preferably ten, amino acids are exchanged by other naturally occurring amino acids. Preferably, the phospho-<NUM>-dehydro-<NUM>-deoxyheptonate aldolase <NUM> (Dhaps1) encoded by the nucleotide sequence of SEQ ID No. <NUM> before inactivation comprises an amino acid sequence as defined in SEQ ID No. <NUM>, in which at most ten, preferably at most nine, preferably at most eight, preferably at most seven, preferably at most six, preferably at most five, preferably at most four, preferably at most three, preferably at most two, preferably at most one, amino acids are exchanged by other naturally occurring amino acids.

According to another option, the at least one further inactivated gene of the genetically modified saprotroph is a gene encoding erythritol utilization factor (EUF). Preferably, the at least one gene encoding erythritol utilization factor (Eufl) of the genetically modified saprotroph comprised the nucleotide sequence of SEQ ID No. <NUM> before inactivation, in particular consisted of the nucleotide sequence of SEQ ID No. <NUM> before inactivation.

Preferably, the at least one gene encoding erythritol utilization factor (Eufl) of the genetically modified saprotroph comprised a nucleotide sequence having at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, sequence identity to SEQ ID No. <NUM> before inactivation. Particularly preferred, the at least one gene encoding erythritol utilization factor (Eufl) of the genetically modified saprotroph consisted of a nucleotide sequence having at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, sequence identity to SEQ ID No. <NUM> before inactivation.

Preferably, the erythritol utilization factor (Eufl) encoded by the nucleotide sequence of SEQ ID No. <NUM> before inactivation comprises the amino acid sequence of SEQ ID No. <NUM>, in particular consists of the amino acid sequence of SEQ ID No. <NUM>.

Preferably, the erythritol utilization factor (Eufl) encoded by the nucleotide sequence of SEQ ID No. <NUM> before inactivation comprises an amino acid sequence having at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, sequence identity to SEQ ID No. <NUM>. Particularly preferred, the erythritol utilization factor (Eufl) encoded by the nucleotide sequence of SEQ ID No. <NUM> before inactivation consists of an amino acid sequence having at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, sequence identity to SEQ ID No. <NUM>.

Preferably, the erythritol utilization factor (Eufl) encoded by the nucleotide sequence of SEQ ID No. <NUM> before inactivation comprises an amino acid sequence as defined in SEQ ID No. <NUM>, in which one, preferably two, preferably three, preferably five, preferably six, preferably seven, preferably eight, preferably nine, preferably ten, amino acids are exchanged by other naturally occurring amino acids. Preferably, the erythritol utilization factor (Euf1) encoded by the nucleotide sequence of SEQ ID No. <NUM> before inactivation comprises an amino acid sequence as defined in SEQ ID No. <NUM>, in which at most ten, preferably at most nine, preferably at most eight, preferably at most seven, preferably at most six, preferably at most five, preferably at most four, preferably at most three, preferably at most two, preferably at most one, amino acids are exchanged by other naturally occurring amino acids.

In a particularly preferred embodiment of the present invention, the at least one further inactivated gene of the genetically modified saprotroph is a gene encoding erythrulose kinase (EYK1). Preferably, the at least one gene encoding erythrulose kinase (Eyk1) of the genetically modified saprotroph comprised the nucleotide sequence of SEQ ID No. <NUM> before inactivation, in particular consisted of the nucleotide sequence of SEQ ID No. <NUM> before inactivation.

According to another preferred option, the at least one gene encoding erythrulose kinase (Eyk1) of the genetically modified saprotroph comprised a nucleotide sequence having at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, sequence identity to SEQ ID No. <NUM> before inactivation. Particularly preferred, the at least one gene encoding erythrulose kinase (Eyk1) of the genetically modified saprotroph consisted of a nucleotide sequence having at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, sequence identity to SEQ ID No. <NUM> before inactivation.

Preferably, the erythrulose kinase (Eyk1) encoded by the nucleotide sequence of SEQ ID No. <NUM> before inactivation comprises the amino acid sequence of SEQ ID No. <NUM>, in particular consists of the amino acid sequence of SEQ ID No. <NUM>.

Preferably, the erythrulose kinase (Eyk1) encoded by the nucleotide sequence of SEQ ID No. <NUM> before inactivation comprises an amino acid sequence having at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, sequence identity to SEQ ID No. <NUM>. Particularly preferred, the erythrulose kinase (Eyk1) encoded by the nucleotide sequence of SEQ ID No. <NUM> before inactivation consists of an amino acid sequence having at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, sequence identity to SEQ ID No. <NUM>.

Preferably, the erythrulose kinase (Eyk1) encoded by the nucleotide sequence of SEQ ID No. <NUM> before inactivation comprises an amino acid sequence as defined in SEQ ID No. <NUM>, in which one, preferably two, preferably three, preferably five, preferably six, preferably seven, preferably eight, preferably nine, preferably ten, amino acids are exchanged by other naturally occurring amino acids. Preferably, the erythrulose kinase (Eyk1) encoded by the nucleotide sequence of SEQ ID No. <NUM> before inactivation comprises an amino acid sequence as defined in SEQ ID No. <NUM>, in which at most ten, preferably at most nine, preferably at most eight, preferably at most seven, preferably at most six, preferably at most five, preferably at most four, preferably at most three, preferably at most two, preferably at most one, amino acids are exchanged by other naturally occurring amino acids.

Preferably, the at least one further inactivated gene of the genetically modified saprotroph is a gene encoding erythritol dehydrogenase (EYD1). Preferably, the at least one gene encoding erythritol dehydrogenase (Eyd1) of the genetically modified saprotroph comprised the nucleotide sequence of SEQ ID No. <NUM> before inactivation, in particular consisted of the nucleotide sequence of SEQ ID No. <NUM> before inactivation.

Preferably, the at least one gene encoding erythritol dehydrogenase (Eyd1) of the genetically modified saprotroph comprised a nucleotide sequence having at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, sequence identity to SEQ ID No. <NUM> before inactivation. According to another preferred option, the at least one gene encoding erythritol dehydrogenase (Eyd1) of the genetically modified saprotroph consisted of a nucleotide sequence having at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, sequence identity to SEQ ID No. <NUM> before inactivation.

Preferably, the erythritol dehydrogenase (Eyd1) encoded by the nucleotide sequence of SEQ ID No. <NUM> before inactivation comprises the amino acid sequence of SEQ ID No. <NUM>, in particular consists of the amino acid sequence of SEQ ID No. <NUM>.

Preferably, the erythritol dehydrogenase (Eyd1) encoded by the nucleotide sequence of SEQ ID No. <NUM> before inactivation comprises an amino acid sequence having at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, sequence identity to SEQ ID No. <NUM>. Particularly preferred, the erythritol dehydrogenase (Eyd1) encoded by the nucleotide sequence of SEQ ID No. <NUM> before inactivation consists of an amino acid sequence having at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, sequence identity to SEQ ID No. <NUM>.

Preferably, the erythritol dehydrogenase (Eyd1) encoded by the nucleotide sequence of SEQ ID No. <NUM> before inactivation comprises an amino acid sequence as defined in SEQ ID No. <NUM>, in which one, preferably two, preferably three, preferably five, preferably six, preferably seven, preferably eight, preferably nine, preferably ten, amino acids are exchanged by other naturally occurring amino acids. Preferably, the erythritol dehydrogenase (Eyd1) encoded by the nucleotide sequence of SEQ ID No. <NUM> before inactivation comprises an amino acid sequence as defined in SEQ ID No. <NUM>, in which at most ten, preferably at most nine, preferably at most eight, preferably at most seven, preferably at most six, preferably at most five, preferably at most four, preferably at most three, preferably at most two, preferably at most one, amino acids are exchanged by other naturally occurring amino acids.

Preferably, the at least one further inactivated gene of the genetically modified saprotroph is a gene encoding erythritol isomerase <NUM> (EYI1). Preferably, the at least one gene encoding erythritol isomerase <NUM> (Eyi1) of the genetically modified saprotroph comprised the nucleotide sequence of SEQ ID No. <NUM> before inactivation, in particular consisted of the nucleotide sequence of SEQ ID No. <NUM> before inactivation.

Particularly preferred, the at least one gene encoding erythritol isomerase <NUM> (Eyi1) of the genetically modified saprotroph comprised a nucleotide sequence having at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, sequence identity to SEQ ID No. <NUM> before inactivation. According to another preferred option, the at least one gene encoding erythritol isomerase <NUM> (Eyi1) of the genetically modified saprotroph consisted of a nucleotide sequence having at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, sequence identity to SEQ ID No. <NUM> before inactivation.

Preferably, the erythritol isomerase <NUM> (Eyi1) encoded by the nucleotide sequence of SEQ ID No. <NUM> before inactivation comprises the amino acid sequence of SEQ ID No. <NUM>, in particular consists of the amino acid sequence of SEQ ID No. <NUM>.

Preferably, the erythritol isomerase <NUM> (Eyi1) encoded by the nucleotide sequence of SEQ ID No. <NUM> before inactivation comprises an amino acid sequence having at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, sequence identity to SEQ ID No. <NUM>. Particularly preferred, the erythritol isomerase <NUM> (Eyi1) encoded by the nucleotide sequence of SEQ ID No. <NUM> before inactivation consists of an amino acid sequence having at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, sequence identity to SEQ ID No. <NUM>.

Preferably, the erythritol isomerase <NUM> (Eyi1) encoded by the nucleotide sequence of SEQ ID No. <NUM> before inactivation comprises an amino acid sequence as defined in SEQ ID No. <NUM>, in which one, preferably two, preferably three, preferably five, preferably six, preferably seven, preferably eight, preferably nine, preferably ten, amino acids are exchanged by other naturally occurring amino acids. Preferably, the erythritol isomerase <NUM> (Eyi1) encoded by the nucleotide sequence of SEQ ID No. <NUM> before inactivation comprises an amino acid sequence as defined in SEQ ID No. <NUM>, in which at most ten, preferably at most nine, preferably at most eight, preferably at most seven, preferably at most six, preferably at most five, preferably at most four, preferably at most three, preferably at most two, preferably at most one, amino acids are exchanged by other naturally occurring amino acids.

According to another preferred option, the at least one further inactivated gene of the genetically modified saprotroph is a gene encoding erythritol isomerase <NUM> (EYI2). Preferably, the at least one gene encoding erythritol isomerase <NUM> (Eyi2) of the genetically modified saprotroph comprised the nucleotide sequence of SEQ ID No. <NUM> before inactivation, in particular consisted of the nucleotide sequence of SEQ ID No. <NUM> before inactivation.

Preferably, the at least one gene encoding erythritol isomerase <NUM> (Eyi2) of the genetically modified saprotroph comprised a nucleotide sequence having at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, sequence identity to SEQ ID No. <NUM> before inactivation. Preferably, the at least one gene encoding erythritol isomerase <NUM> (Eyi2) of the genetically modified saprotroph consisted of a nucleotide sequence having at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, sequence identity to SEQ ID No. <NUM> before inactivation.

Preferably, the erythritol isomerase <NUM> (Eyi2) encoded by the nucleotide sequence of SEQ ID No. <NUM> before inactivation comprises the amino acid sequence of SEQ ID No. <NUM>, in particular consists of the amino acid sequence of SEQ ID No. <NUM>.

Preferably, the erythritol isomerase <NUM> (Eyi2) encoded by the nucleotide sequence of SEQ ID No. <NUM> before inactivation comprises an amino acid sequence having at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, sequence identity to SEQ ID No. <NUM>. Particularly preferred, the erythritol isomerase <NUM> (Eyi2) encoded by the nucleotide sequence of SEQ ID No. <NUM> before inactivation consists of an amino acid sequence having at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, sequence identity to SEQ ID No. <NUM>.

Preferably, the erythritol isomerase <NUM> (Eyi2) encoded by the nucleotide sequence of SEQ ID No. <NUM> before inactivation comprises an amino acid sequence as defined in SEQ ID No. <NUM>, in which one, preferably two, preferably three, preferably five, preferably six, preferably seven, preferably eight, preferably nine, preferably ten, amino acids are exchanged by other naturally occurring amino acids. Preferably, the erythritol isomerase <NUM> (Eyi2) encoded by the nucleotide sequence of SEQ ID No. <NUM> before inactivation comprises an amino acid sequence as defined in SEQ ID No. <NUM>, in which at most ten, preferably at most nine, preferably at most eight, preferably at most seven, preferably at most six, preferably at most five, preferably at most four, preferably at most three, preferably at most two, preferably at most one, amino acids are exchanged by other naturally occurring amino acids.

According to another preferred option, the at least one further inactivated gene selected from the group consisting of a gene encoding phospho-<NUM>-dehydro-<NUM>-deoxyheptonate aldolase <NUM> (Dhaps-<NUM>), a gene encoding erythritol utilization factor (EUF), a gene encoding erythrulose kinase (EYK1), a gene encoding erythritol dehydrogenase (EYD1), a gene encoding erythritol isomerase (EYI1) and a gene encoding erythritol isomerase (EYI2) of the genetically modified saprotroph is deleted.

Preferably, the at least one further inactivated gene selected from the group consisting of a gene encoding phospho-<NUM>-dehydro-<NUM>-deoxyheptonate aldolase <NUM> (Dhaps-<NUM>), a gene encoding erythritol utilization factor (EUF), a gene encoding erythrulose kinase (EYK1), a gene encoding erythritol dehydrogenase (EYD1), a gene encoding erythritol isomerase (EYI1) and a gene encoding erythritol isomerase (EYI2) of the genetically modified saprotroph is non-functional.

Particularly preferred, the at least one further inactivated gene selected from the group consisting of a gene encoding phospho-<NUM>-dehydro-<NUM>-deoxyheptonate aldolase <NUM> (Dhaps-<NUM>), a gene encoding erythritol utilization factor (EUF), a gene encoding erythrulose kinase (EYK1), a gene encoding erythritol dehydrogenase (EYD1), a gene encoding erythritol isomerase (EYI1) and a gene encoding erythritol isomerase (EYI2) of the genetically modified saprotroph is inactivated by gene knock-out, in particular gene replacement. Preferably, the at least one further inactivated gene selected from the group consisting of a gene encoding phospho-<NUM>-dehydro-<NUM>-deoxyheptonate aldolase <NUM> (Dhaps-<NUM>), a gene encoding erythritol utilization factor (EUF), a gene encoding erythrulose kinase (EYK1), a gene encoding erythritol dehydrogenase (EYD1), a gene encoding erythritol isomerase (EYI1) and a gene encoding erythritol isomerase (EYI2) of the genetically modified saprotroph is inactivated by gene replacement using a deletion cassette.

Preferably, the at least one further inactivated gene selected from the group consisting of a gene encoding phospho-<NUM>-dehydro-<NUM>-deoxyheptonate aldolase <NUM> (Dhaps-<NUM>), a gene encoding erythritol utilization factor (EUF), a gene encoding erythrulose kinase (EYK1), a gene encoding erythritol dehydrogenase (EYD1), a gene encoding erythritol isomerase (EYI1) and a gene encoding erythritol isomerase (EYI2) of the genetically modified saprotroph is inactivated, in particular made non-functional, by genome editing, in particular by meganucleases, zinc-finger nucleases (ZFNs), transcription activator-like effector nucleases (TALENs) or by the clustered regularly interspaced short palindromic repeats (CRISPR) system.

Preferably, the genetically modified saprotroph further comprises at least one gene encoding at least one transketolase. Preferably, the at least one gene encoding at least one transketolase is tkl1, in particular is codon-optimized tkl1. Preferably, the genetically modified saprotroph further comprises at least one gene encoding tkl1 from T. reesei, in particular codon-optimized tkl1 from T. Preferably, the at least one gene encoding at least one transketolase comprises the nucleotide sequence of SEQ ID No. <NUM>, in particular consists of the nucleotide sequence of SEQ ID No. <NUM>.

Further preferably, the at least one gene encoding at least one transketolase comprises a nucleotide sequence having at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, sequence identity to SEQ ID No. <NUM>. Preferably, the at least one gene encoding at least one transketolase consists of a nucleotide sequence having at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, sequence identity to SEQ ID No. <NUM>.

Preferably, the at least one transketolase comprises the amino acid sequence of SEQ ID No. <NUM>, in particular consists of the amino acid sequence of SEQ ID No. <NUM>.

According to another preferred option, the at least one transketolase comprises an amino acid sequence having at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, sequence identity to SEQ ID No. <NUM>. Particularly preferred, the at least one transketolase consists of an amino acid sequence having at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, sequence identity to SEQ ID No. <NUM>.

Further preferably, the at least one transketolase comprises an amino acid sequence as defined in SEQ ID No. <NUM>, in which one, preferably two, preferably three, preferably five, preferably six, preferably seven, preferably eight, preferably nine, preferably ten, amino acids are exchanged by other naturally occurring amino acids. Particularly preferred, the at least one transketolase comprises an amino acid sequence as defined in SEQ ID No. <NUM>, in which at most ten, preferably at most nine, preferably at most eight, preferably at most seven, preferably at most six, preferably at most five, preferably at most four, preferably at most three, preferably at most two, preferably at most one, amino acids are exchanged by other naturally occurring amino acids.

Preferably, the genetically modified saprotroph further comprises at least one gene encoding at least one transaldolase. Preferably, the at least one gene encoding at least one transaldolase is tall, in particular is codon-optimized tall. Preferably, the genetically modified saprotroph further comprises at least one gene encoding tall from T. reesei, in particular codon-optimized tall from T. Preferably, the at least one gene encoding at least one transaldolase comprises the nucleotide sequence of SEQ ID No. <NUM>, in particular consist of the nucleotide sequence of SEQ ID No. <NUM>.

Preferably, the at least one gene encoding at least one transaldolase comprises a nucleotide sequence having at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, sequence identity to SEQ ID No. <NUM>. Preferably, the at least one gene encoding at least one transaldolase consists of a nucleotide sequence having at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, sequence identity to SEQ ID No. <NUM>.

Preferably, the at least one transaldolase comprises the amino acid sequence of SEQ ID No. <NUM>, in particular consists of the amino acid sequence of SEQ ID No. <NUM>.

Particularly preferred, the at least one transaldolase comprises an amino acid sequence having at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, sequence identity to SEQ ID No. <NUM>. Preferably, the at least one transaldolase consists of an amino acid sequence having at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, sequence identity to SEQ ID No. <NUM>.

According to another preferred option, the at least one transaldolase comprises an amino acid sequence as defined in SEQ ID No. <NUM>, in which one, preferably two, preferably three, preferably five, preferably six, preferably seven, preferably eight, preferably nine, preferably ten, amino acids are exchanged by other naturally occurring amino acids. Particularly preferred, the at least one transaldolase comprises an amino acid sequence as defined in SEQ ID No. <NUM>, in which at most ten, preferably at most nine, preferably at most eight, preferably at most seven, preferably at most six, preferably at most five, preferably at most four, preferably at most three, preferably at most two, preferably at most one, amino acids are exchanged by other naturally occurring amino acids.

Further preferably, the genetically modified saprotroph further comprises at least one gene encoding at least one erythritol utilization factor (EUF). Preferably, the at least one gene encoding at least one erythritol utilization factor, is euf1, in particular is codon-optimized euf1. Preferably, the genetically modified saprotroph further comprises at least one gene encoding euf1 from T. reesei, in particular codon-optimized euf1 from T. Preferably, the at least one gene encoding at least one erythritol utilization factor (EUF) comprises the nucleotide sequence of SEQ ID No. <NUM>, in particular consist of the nucleotide sequence of SEQ ID No. <NUM>.

Preferably, the at least one gene encoding at least one erythritol utilization factor of the genetically modified saprotroph comprises a nucleotide sequence having at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, sequence identity to SEQ ID No. <NUM>. Preferably, the at least one gene encoding at least one erythritol utilization factor consists of a nucleotide sequence having at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, sequence identity to SEQ ID No. <NUM>.

Preferably, the at least one erythritol utilization factor (EUF) comprises the amino acid sequence of SEQ ID No. <NUM>, in particular consists of the amino acid sequence of SEQ ID No. <NUM>.

Further preferably, the at least one erythritol utilization factor comprises an amino acid sequence having at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, sequence identity to SEQ ID No. <NUM>. Preferably, the at least one erythritol utilization factor consists of an amino acid sequence having at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, sequence identity to SEQ ID No. <NUM>.

Further preferably, the at least one erythritol utilization factor comprises an amino acid sequence as defined in SEQ ID No. <NUM>, in which one, preferably two, preferably three, preferably five, preferably six, preferably seven, preferably eight, preferably nine, preferably ten, amino acids are exchanged by other naturally occurring amino acids. Particularly preferred, the at least one erythritol utilization factor comprises an amino acid sequence as defined in SEQ ID No. <NUM>, in which at most ten, preferably at most nine, preferably at most eight, preferably at most seven, preferably at most six, preferably at most five, preferably at most four, preferably at most three, preferably at most two, preferably at most one, amino acids are exchanged by other naturally occurring amino acids.

According to a preferred option, the at least one gene encoding at least one membrane-bound alditol transporter, the at least one gene encoding at least one erythrose reductase, the at least one gene encoding at least one transketolase, the at least one gene encoding at least one transaldolase and/or the at least one gene encoding at least one erythritol utilization factor (EUF) of the genetically modified saprotroph is an exogenous polynucleotide sequence.

Preferably, the at least one gene encoding at least one membrane-bound alditol transporter, the at least one gene encoding at least one erythrose reductase, the at least one gene encoding at least one transketolase, the at least one gene encoding at least one transaldolase and/or the at least one gene encoding at least one erythritol utilization factor (EUF) of the genetically modified saprotroph is an endogenous polynucleotide sequence.

Further preferably, the genetically modified saprotroph comprises at least one exogenous gene encoding at least one membrane-bound alditol transporter. Preferably, genetically modified saprotroph comprises at least one endogenous gene encoding at least one membrane-bound alditol transporter.

Preferably, the genetically modified saprotroph comprises at least one exogenous gene encoding at least one erythrose reductase. According to another preferred option, the genetically modified saprotroph comprises at least one endogenous gene encoding at least one erythrose reductase.

Further preferred, the genetically modified saprotroph comprises at least one exogenous gene encoding at least one transketolase. In a preferred embodiment of the present invention, the genetically modified saprotroph comprises at least one endogenous gene encoding at least one transketolase.

Preferably, the genetically modified saprotroph comprises at least one exogenous gene encoding at least one transaldolase. Preferably, the genetically modified saprotroph comprises at least one endogenous gene encoding at least one transaldolase.

Preferably, the genetically modified saprotroph comprises at least one exogenous gene encoding at least one erythritol utilization factor (EUF). Preferably, the genetically modified saprotroph comprises at least one endogenous gene encoding at least one erythritol utilization factor (EUF).

According to a preferred option, the at least one gene encoding at least one membrane-bound alditol transporter, the at least one gene encoding at least one erythrose reductase, the at least one gene encoding at least one transketolase, the at least one gene encoding at least one transaldolase and/or the at least one gene encoding at least one erythritol utilization factor (EUF) is stably or transiently introduced into the genome of the genetically modified saprotroph.

Particularly preferred, the at least one gene encoding at least one membrane-bound alditol transporter, the at least one gene encoding at least one erythrose reductase, the at least one gene encoding at least one transketolase, the at least one gene encoding at least one transaldolase and/or the at least one gene encoding at least one erythritol utilization factor (EUF), is overexpressed.

Preferably, the at least one gene encoding at least one membrane-bound alditol transporter, in particular the at least one exogenous or endogenous gene encoding at least one membrane-bound alditol transporter, of the genetically modified saprotroph is overexpressed. Further preferred, the at least one gene encoding at least one erythrose reductase, in particular the at least one exogenous or endogenous gene encoding at least one erythrose reductase, of the genetically modified saprotroph is overexpressed. Preferably, the at least one gene encoding at least one transketolase, in particular the at least one exogenous or endogenous gene encoding at least one transketolase, of the genetically modified saprotroph is overexpressed. Further preferred, the at least one gene encoding at least one transaldolase, in particular the at least one exogenous or endogenous gene encoding at least one transaldolase, of the genetically modified saprotroph is overexpressed. Preferably, the at least one gene encoding at least one erythritol utilization factor (EUF), in particular the at least one exogenous or endogenous gene encoding at least one erythritol utilization factor (EUF), of the genetically modified saprotroph is overexpressed.

According to a further preferred option, the at least one gene encoding at least one membrane-bound alditol transporter, the at least one gene encoding at least one erythrose reductase, the at least one gene encoding at least one transketolase, the at least one gene encoding at least one transaldolase and/or the at least one gene encoding at least one erythritol utilization factor (EUF) of the genetically modified saprotroph is under the control of a constitutive or inducible promoter. Preferably, the constitutive or inducible promoter is a naturally occurring promoter. In a further preferred embodiment, the constitutive or inducible promoter is a synthetic promoter. Preferably, the constitutive promoter is selected from pki, tef, gpd. The inducible promoter is preferably selected from bga1, bxl1, cbh1, cbh2, xyn1, xyn2.

Preferably, the at least one gene of the genetically modified saprotroph encoding at least one membrane-bound alditol transporter is under the control of a promoter selected from pki, tef, gpd, preferably under control of a pki promoter. Preferably, the at least one gene of the genetically modified saprotroph encoding at least one erythrose reductase is under the control of a promoter selected from pki, tef, gpd, preferably under control of a tef promoter. Preferably, the at least one gene of the genetically modified saprotroph encoding at least one transketolase is under the control of a promoter selected from pki, tef, gpd, preferably under control of a tef promoter. Preferably, the at least one gene of the genetically modified saprotroph encoding at least one transaldolase is under the control of a promoter selected from pki, tef, gpd, preferably under control of a tef promoter. Preferably, the at least one gene of the genetically modified saprotroph encoding at least one erythritol utilization factor (EUF) is under the control of a promoter selected from pki, tef, gpd, preferably under control of a tef promoter.

According to a further preferred option, the at least one gene of the genetically modified saprotroph encoding at least one membrane-bound alditol transporter, the at least one gene of the genetically modified saprotroph encoding at least one erythrose reductase, the at least one gene of the genetically modified saprotroph encoding at least one transketolase, the at least one gene of the genetically modified saprotroph encoding at least one transaldolase and/or the at least one gene of the genetically modified saprotroph encoding at least one erythritol utilization factor (EUF) is present on a plasmid. Preferably, each of the at least one gene of the genetically modified saprotroph encoding at least one membrane-bound alditol transporter, the at least one gene of the genetically modified saprotroph encoding at least one erythrose reductase, the at least one gene of the genetically modified saprotroph encoding at least one transketolase, the at least one gene of the genetically modified saprotroph encoding at least one transaldolase and/or the at least one gene of the genetically modified saprotroph encoding at least one erythritol utilization factor (EUF) is present on a separate plasmid.

Particularly preferred, the genetically modified saprotroph is the Trichoderma reesei strain deposited at the Westerdijk Fungal Biodiversity Institute under CBS number <NUM>.

According to a preferred option, the at least one saprotroph is cultivated in step a) in a volume of at least <NUM>, preferably at least <NUM>, preferably, at least <NUM>, preferably at least <NUM>, preferably at least <NUM>, preferably at least <NUM>, preferably at least <NUM>, preferably at least <NUM>, preferably at least <NUM>, preferably at least <NUM>, preferably at least <NUM>, preferably at least <NUM>, preferably at least <NUM>, preferably at least <NUM>, preferably at least <NUM>.

In a further preferred embodiment of the present invention, the at least one saprotroph is cultivated in step a) in the culture medium until the culture medium contains erythritol in a concentration of at least <NUM>/L, preferably at least <NUM>/L, preferably at least <NUM>/L, preferably at least <NUM>/L, preferably at least <NUM>/L, preferably at least <NUM>/L, preferably at least <NUM>/L, preferably at least <NUM>/L, preferably at least <NUM>/L, preferably at least <NUM>/L, preferably at least <NUM>/L, preferably at least <NUM>/L, preferably at least <NUM>/L, preferably at least <NUM>/L, preferably at least <NUM>/L, preferably at least <NUM>/L, preferably at least <NUM>/L, preferably at least <NUM>/L, preferably at least <NUM>/L, preferably at least <NUM>/L, preferably at least <NUM>/L, preferably at least <NUM>/L, preferably at least <NUM>/L, preferably at least <NUM>/L, preferably at least <NUM>/L, preferably at least <NUM>/L.

Particularly preferred, the at least one saprotroph is cultivated in the culture medium until the culture medium contains erythritol in the concentration of <NUM>/L to <NUM>/L, preferably <NUM>/L to <NUM>/L, preferably <NUM>/L to <NUM>/L, preferably <NUM>/L to <NUM>/L.

According to a further preferred option, the at least one saprotroph is cultivated in the culture medium until the culture medium contains erythritol in the concentration of <NUM>/L to <NUM>/L, preferably <NUM>/L to <NUM>/L, preferably <NUM>/L to <NUM>/L, preferably <NUM>/L to <NUM>/L, preferably <NUM>/L to <NUM>/L, preferably <NUM>/L to <NUM>//L.

In a particularly preferred embodiment of the present invention, the at least one saprotroph is cultivated in step a) in the culture medium at a pH in the range of <NUM> to <NUM>, preferably <NUM> to <NUM>, preferably <NUM> to <NUM>, preferably <NUM> to <NUM>. Particularly preferred the at least one saprotroph is cultivated in the culture medium at a pH of at most <NUM>, preferably at most <NUM>, preferably at most <NUM>, preferably at most <NUM>, preferably at most <NUM>.

According to a preferred option, the at least one saprotroph is cultivated in step a) in the culture medium at a temperature of <NUM> to <NUM>, preferably <NUM> to <NUM>, preferably <NUM> to <NUM>, preferably <NUM> to <NUM>, preferably <NUM> to <NUM>, preferably <NUM>.

Preferably, the at least one saprotroph is cultivated in step a) in the culture medium at a temperature of at least <NUM>, preferably at least <NUM>, preferably at least <NUM>, preferably at least <NUM>, preferably at least <NUM>, preferably at least <NUM>.

According to a further preferred option, the at least one saprotroph is cultivated in step a) in the culture medium at a temperature of at most <NUM>, preferably at most <NUM>, preferably at most <NUM>, preferably at most <NUM>, preferably at most <NUM>.

Preferably, the at least one saprotroph is cultivated in the culture medium in step a) for at least <NUM> hours, preferably at least <NUM> hours, preferably at least <NUM> hours, preferably at least <NUM> hours, preferably at least <NUM> hours, preferably at least <NUM> hours, preferably at least <NUM> hours, preferably at least <NUM> hours, preferably at least <NUM> hours, preferably at least <NUM> hours, preferably at least <NUM> hours, preferably at least <NUM> hours, preferably at least <NUM> hours.

According to a further preferred option, the at least one saprotroph is cultivated in the culture medium in step a) for at most <NUM> hours, preferably at most <NUM> hours, preferably at most <NUM> hours, preferably at most <NUM> hours, preferably at most <NUM> hours, preferably at most <NUM> hours, preferably at most <NUM> hours, preferably at most <NUM> hours, preferably at most <NUM> hours, preferably at most <NUM> hours, preferably at most <NUM> hours, preferably at most <NUM> hours, preferably at most <NUM> hours.

According to a preferred option, the cultivation of the at least one saprotroph in step a) is conducted without the addition of osmotically effective agents during cultivation, in particular without the addition of at least one salt during cultivation. Particularly preferred, the cultivation of the at least one saprotroph in step a) is conducted without the addition of sodium chloride (NaCl) during cultivation.

Preferably, the cultivation of the at least one saprotroph in step a) is conducted in batch-mode. Preferably, the cultivation of the at least one saprotroph in step a) is conducted in fed-batch mode. In another preferred embodiment, cultivation of the at least one saprotroph in step a) is conducted in continuous mode.

In a further preferred embodiment of the present invention the erythritol is recovered in step c) by crystallisation.

In a particularly preferred embodiment of the present invention, the recovery of erythritol in step b) comprises the steps:.

According to a preferred embodiment of the present invention, a heat denaturing step is conducted prior to, during or after step i). Preferably, a heat denaturing step is conducted prior to step i). In a further preferred embodiment, a heat denaturing step is conducted during step i). Preferably, a heat denaturing step is conducted after step i).

Particularly preferred, the heat denaturing step includes heating the culture medium to a temperature of at least <NUM>, preferably at least <NUM>, preferably at least <NUM>, preferably at least <NUM>, preferably at least <NUM>, preferably at least <NUM>, preferably <NUM>, preferably at least <NUM>, preferably at least <NUM>, preferably at least <NUM>, preferably at least <NUM>.

According to a preferred option, the culture medium is subjected to heat denaturation for at least <NUM> seconds, preferably at least <NUM> seconds, preferably at least <NUM> seconds, preferably at least <NUM> seconds, preferably at least <NUM> seconds, preferably at least <NUM>, preferably at least <NUM>, preferably at least <NUM>, preferably at least <NUM>, preferably at least <NUM>, preferably at least <NUM>, preferably at least <NUM>, preferably at least <NUM>, preferably at least <NUM>, preferably at least <NUM>.

The heat denaturing step primarily serves to heat-inactivate proteins and enzymes in the culture medium before conducting further recovery steps.

According to a particularly preferred option, the erythritol recovered in step b), in particular the erythritol obtained in step v), has a purity of at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>%, preferably at least <NUM>,<NUM>%, preferably at least <NUM>%, preferably at least <NUM>,<NUM>%, preferably at least <NUM>%, preferably at least <NUM>,<NUM>%.

The term "genetically modified" and its grammatical equivalents as used herein refer to one or more alterations of a nucleic acid, e.g. the nucleic acid within the genome of an organism, in particular within the genome of a saprotroph. A "genetically modified" saprotroph can refer to a saprotroph with an added, deleted and/or altered, in particular inactivated, gene.

In the context of the present invention, the term "erythrose reductase" pertains to any enzyme that catalyses reversibly the reduction of an aldose to an alditol, wherein the enzyme has predominant specific activity for the reduction of erythrose to erythritol. Thus, an "erythrose reductase" according to the present invention exhibits a high specificity and affinity for the substrate erythrose. Particularly, the "erythrose reductase" has a higher specificity for erythrose than for any other substrate, such as glycerol.

The term "membrane-bound alditol transporter" as used herein designates a membrane protein suitable to reversibly transport alditols across the outer membrane, in particular to transport intracellularly produced alditols to the culture medium. According to the present invention, a "membrane-bound alditol transporter" is suitable to transport intracellularly produced erythritol across the membrane to the culture medium.

In the context of the present invention, the term "transketolase" refers to an enzyme of the pentose phosphate pathway catalysing the thiamine-dependent reversible transfer of a C-<NUM> unit from a ketose donor to an acceptor aldopentose. In particular, the "transketolase" catalyses the transfer of a C-<NUM> unit from xylulose-<NUM>-phosphate to ribose-<NUM>-phosphate forming seduheptulose-<NUM>-phosphate and glyceraldehyde-<NUM>-phosphate.

The term "transaldolase" designates an enzyme of the non-oxidative branch of the pentose phosphate pathway catalysing the reversible transfer of a C-<NUM> unit from a ketose donor to an acceptor aldose. In particular, the "transketolase" catalyses the transfer of a C-<NUM> unit from sedoheptulose-<NUM>-phosphate to glyceraldehyde-<NUM>-phosphate forming erythrose-<NUM>-phosphate and fructose-<NUM>-phosphate.

In the context of the present invention, an "inactivated" gene is a gene which can temporarily or permanently not be transcribed or can be transcribed but the transcript is not accessible for gene translation. According to the present invention, the inactivation of a gene includes but is not limited to inactivation by partial or complete gene deletion, partial or complete gene replacement, gene repression, gene insertion, and gene mutation. "Inactivation" in the context of the present invention further includes any post-transcriptional gene regulation, in particular by RNAi or siRNA, resulting in inhibition of translation of the transcript into the gene product.

In the context of the present invention, a "non-functional" gene is a gene that is present in the genome of an organism or a plasmid in an organism which gene is either not transcribed or is transcribed but the transcript is not translated to the gene product.

In the context of the present invention, a "deleted" gene is a gene that has previously been present in the genome of an organism or a plasmid in an organism but has been completely removed from the genome of the organism or the plasmid in the organism.

In the context of the present invention, the verb "to overexpress" refers to the artificial expression of a gene in increased quantity. This includes the inducible overexpression of a gene which can be regulated using an inducible promoter and the constant overexpression of a gene using a constitutive promoter.

The term "oligomeric sugars" or "oligomeric C-<NUM> and C-<NUM> sugars" is used herein for di-, oligo-, and polysaccharides which are composed of at least two monomers, preferably composed of at least two monomers selected from C-<NUM> and C-<NUM> sugars.

In the context of the present invention, the term "a" is meant to include the meaning of "one" or "one or more".

In the context of the present invention, the term "comprising" preferably has the meaning of "containing" or "including", meaning including the specifically identified elements without excluding the presence of further elements. However, in a preferred embodiment, the term "comprising" is also understood to have the meaning of "consisting essentially of" and in a further preferred embodiment the meaning of "consisting of".

The terms "and/or" is used herein to express the disclosure of any combination of individual elements connected within a listing. Solely for illustrative purposes, the expression "A, B, and/or C" can mean A individually, B individually, C individually, (A and B), (B and C), (A and C), and (A, B and C).

Further preferred embodiments of the invention are subject of the subclaims.

The invention is further described by way of the following example and accompanying figures.

Trichoderma reesei was cultivated in <NUM> flasks each comprising <NUM> culture medium containing either <NUM>/L, <NUM>/L or <NUM>/L glucose as carbon source and <NUM> urea as nitrogen source.

After <NUM> hours of cultivation, the erythritol concentration was measured in the culture medium of the samples. The average concentration of erythritol in the samples was <NUM>/L (<NUM>/L glucose), <NUM>/L (<NUM>/L glucose), and <NUM>/L (<NUM>/L glucose) (see <FIG>).

In a similar experiment, Trichoderma reesei was cultivated in <NUM> flasks each comprising <NUM> culture medium containing <NUM>/L glucose as carbon source and either <NUM>, <NUM> or <NUM> urea as nitrogen source.

Claim 1:
A method for the production of erythritol, comprising the steps:
a) cultivating at least one saprotroph selected from the genera Hypocrea and Trichoderma in a culture medium comprising a carbon source in a concentration of <NUM> to <NUM>/L and a nitrogen source, so as to obtain erythritol in the culture medium, and
b) recovering erythritol from the culture medium,
wherein the carbon source is a monomeric or oligomeric C-<NUM> sugar or a mixture thereof, wherein the C-<NUM> sugar is selected from the group consisting of glucose and fructose.