bluuebunny/crossref_metadata_2025 huggingface dataset:
Enzymatic C‐C Bond Formation, Asymmetric
Authors: Kara Selin , Liese Andreas
Published: April 2010

The environmental awareness has grown during the past years focusing on efficient utilization of energy, elimination of waste and avoidance of toxic and/or hazardous reagents.Biocatalysis fulfills the requirement of “green chemistry”; since enzymes are biodegradable catalysts which can effectively catalyze the reactions under mild conditions(ambient temperature, no need for high pressure, no extreme pH, no toxic solvents and no heavy metal catalysts).C–C bond formation reactions are fundamental to all of organic chemistry, and enzymes show promise for use in this field. A variety of versatile building blocks in organic and pharmaceutical chemistry can be synthesized by biocatalysts. In comparison to available chemical routes enzymes also provide chemo‐, regio‐, and stereoselective catalysis. Different enzyme classes are applied in the field of C–C bond formation to synthesize complex, aldol reactions, and cyanohydrin formations. Few applications are also found in ketol‐ and aldol transfer reactions. Furthermore, promiscuous activity of lipases can be applied in C–C bond formation reactions.
Enzyme Immobilization, Biocatalyst Featured with Nanoscale Structure
Authors: Fei Gao , Ma Guang‐Hui , Wang Ping , Su Zhi‐Guo
Published: April 2010

Since the industrialization of heterogeneous biocatalysts in the 1960s, substantial research efforts have been taken to construct feasible biocatalyses. The surprising progresses of nanotechnology in the 1990s were soon closely followed by the rapid development of nano‐biotechnology. Quite a number of advanced nanomaterials have shown great potential in revolutionizing the preparation of biocatalysts. Mesoporous carriers, one of the most recent, intensively studied materials, could provide a highly ordered internal space with size comparable to enzyme molecules, a considerable loading capacity, and enzyme stability. The large curvature of nanoparticles would benefit the conformational stability, and the Brownian motion of nanobiocatalysts such as the solution behavior nanoparticles, tethered and gel‐armored enzymes, would improve the mass transportation when compared to the traditional heterogeneous catalysis. Some other nanomaterials, such as nanofibers and nanotubes have shown potential for revolutionizing the enzyme support and industrial bioprocesses. More sophisticated hierarchical structure based on nanobiocatalysts is also discussed in this article; this was developed to overcome the drawbacks and ensure sustainable development of nanobiocatalysts.
Freeze‐Drying, Pharmaceuticals
Authors: Liu Jinsong
Published: April 2010

This article provides an overview of the fundamental aspects for pharmaceutical freeze‐drying, including the rationale for freeze‐drying process design and control, the basics of formulation development for freeze‐drying, the importance of the container‐closure system, and a general description of pharmaceutical freeze‐dryers. In the second part of this article, the challenges in freeze‐drying scale‐up and transfer, freezing control, use of cosolvent, freeze‐drying in syringes, process analytical technology, and quality‐by‐design in freeze‐drying have been discussed, and some new advancements related to these aspects are also highlighted.
Glyoxylate Bypass ofEscherichia Coli, Regulation
Authors: Laporte David
Published: April 2010

The glyocylate bypass of E. coli has served as a model system for the regulation of metabolism. This pathway, which is essential for growth on acetate, is regulated my multiple mechanism, including protein phosphorylation, allosteric interactions and transcriptional regulation. By studying this system, the fundamental principles of metabolic regulation can be elucidated.
Inoculum Expansion Methods, Recombinant Mammalian Cell Lines
Authors: Kloth Claudia , Maclsaac Glenn , Ghebremariam Haile , Arunakumari Alahari
Published: April 2010

This article reviews general practices and state‐of‐the‐art inoculum expansion methods for recombinant mammalian cell lines. Suspension cell lines are the main focus due to their predominant current and anticipated future usage in large scale biomanufacturing. Conventional inoculum expansion methods are discussed including small scale flasks and seed bioreactors. Disposable technologies and approaches for time reduction during this incoulum expansion step are reviewed, as it is typically a time consuming phase of large scale manufacturing. Technology transfer and the influence of cell bank quality on successful vial thaw and expansion are alo addressed.
Laccase
Authors: Claus Harald , Strong Peter J.
Published: April 2010

Laccases [EC 1.10.3.2, para‐bezenediol:dioxygen oxidoreductases] are multi‐copper proteins that oxidize various aromatic and non‐aromatic compounds by a radical‐catalyzed reaction mechanism using molecular oxygen as the secondary substrate. Laccase has a number of biological roles that include lignification, delignification, turnover of humic substances in soil and aquatic environments, pathogenicity, detoxification, morphogenesis, sporulation, growth and development of rhizomorphs, polymerization of melanin precursors and spore coat resistance. The ability of laccase to catalyze oxidation with only oxygen as a secondary substrate, its broad substrate range, and high catalytic constants have made it an appealing enzyme for a variety of remediative applications. These include bioremediation of phenolic‐rich wastewaters generated by paper and pulp, textile and dye, food and distillery industries as well as bioremediation of soils contaminated with recalcitrant xenobiotics such as chlorinated phenolic compounds, polycyclic aromatic hydrocarbons, explosives, endocrine‐disrupting chemicals, insecticides, fungicides, and herbicides. The enzyme's broad substrate spectrum, the use of readily available oxygen as the final electron acceptor, and no requirement for cofactors or peroxide have made it appealing for a variety of industrial applications in fields ranging from textile dyes, pulp and paper, biosensors, biofuel cells, chemical synthesis, beverage stabilisation, food products, and ethanol production. The advantages of laccase compared to other enzymes include relatively high yields, uncomplicated isolation from bulk fungal cultures, easy screening for specific producers with a broad substrate spectrum, a high degree of stability and activity especially after immobilization, and heterologous expression systems that have already been established. The characteristics of laccase allow for its potential utilization across a number of research areas, which will result in continued intensive investigations to better understand the enzyme and apply it forthe benefit of both humans and the environment.
Lipases
Authors: Kanwar Shamsher S. , Verma Madan Lal
Published: April 2010

Bioengineering is seen as a promising technique for yielding products by exploiting the concept of green chemistry. Amongst various enzymes available from diverse microbial and other sources, lipase is most versatile as it is endowed with the property of performing biochemical reaction in aqueous as well as organic/water‐restricted solvents. Microbial lipases have been expressed in efficient expression vectors to enhance their yields for commercial applications. However, to perform productive and efficient catalysis, involvement of principles of structural engineering of the biocatalyst, reaction conditions and choice of solvents is essential to achieve a higher rate of catalysis. The review revolves around the use of principles of bioengineering to subtly exploit inherent properties of lipases.
Amino Acids, Branched Chain,L‐Isoleucine
Authors: Jojima Toru , Inui Masayuki , Yukawa Hideaki
Published: April 2010

This article is an overview of the biosynthetic pathway ofL‐isoleucine and its regulation inEscherichia coli, and also describes evolution ofL‐isoleucine‐hyperproducing strains of microorganisms.L‐isoleucine is one of threebranched‐chain amino acids(BCAAs). They are synthesizedde novoby bacteria, fungi and plants, but are nutritionally essential for vertebrates. The importance ofL‐isoleucine in nutrition has stimulated intensive researches for development of microorganisms capable of overproducingL‐isoleucine for industrial production by fermentation from sugar. BCAAs are synthesized via parallel biosynthetic pathways. Four enzymes,acetohydroxyacid synthase(AHAS),acetohydroxyacid isomeroreductase(AHAIR),dihydroxy acid dehydrase(DH), andtransaminase B(TrB), are shared in bothL‐isoleucine andL‐valine synthesis. The first enzyme AHAS catalyzes the condensation of pyruvate and 2‐ketobutyrate forL‐isoleucine synthesis or the condensation of two molecules of pyruvate forL‐valine synthesis. Biosynthesis ofL‐isoleucine as well as other BCAAs is tightly controlled by complex regulation mechanisms that include multivalent regulation of both gene expression and feed back inhibition of enzyme activities by end product BCAAs. A variety of microbial strains with high productivity ofL‐isoleucine have been developed by screening mutants that can grow in the presence of BCAA analogs and by genetic engineering. In these mutants, the regulation ofL‐isoleucine synthesis including repression of gene expression and feed back inhibition are released. This article also describes a novel bioprocess,living cell reaction(LCR) process, that has potential to address the disadvantages of existing fermentation processes including low yield and by‐product formation.
Luminescent Materials, Biological Applications
Authors: Ronda Cees , Bachmann P. K. , Hummel H. , Juestel T. , Meriikhi J.
Published: April 2010

This chapter deals with inorganic luminescent materials and consists of two parts. It starts with a general description of luminescence‐ and excitation mechanisms, by giving a description of the way they operate in well‐known devices, like lamps or medical imaging equipment. In the second part, we concentrate on emerging medical applications. The focus is on the interplay between the performance of the luminophores required by the application and material properties of the luminescent compounds.
Protein Chromatography, Manufacturing Scale
Authors: Bertolini Joseph
Published: April 2010

Chromatographic procedures are an important part of many biopharmaceutical manufacturing processes for the purification of therapeutic proteins. The scale‐up of developed chromatographic processes from laboratory to pilot scale and finally. manufacturing scale can be achieved technically via well‐recognized principles involving increasing column surface area, while maintaining constant bed height, linear flow, and proportionally increasing the volume of solutions used in the process. Alternatively, one can ensure that the residence time of the protein during passage through the chromatographic resin is maintained during scale‐up. The integrity of the column packing at all scales is confirmed by the determination of the height equivalent to a theoretical plate (HETP) and the asymmetry factor from test chromatograms.
Microalgae, Mass Culture Methods
Authors: Grima Emilio Molina , Fernández Sevilla Jose María , Acién Fernández Francisco Gabriel
Published: April 2010

This chapter reviews the major factors governing the production of microalgae. Special emphasis is given to the impact of light availability, and its modification as a consequence of fluid‐dynamics within the photobioreactor (PBR), the mass‐liquid‐mass transfer and the heat‐transfer capacity of the PBR. The major types of bioreactors used for mass culture of microalgae, not only on the basis of a commercial application but also from an engineering point of view, are also reviewed. Equations for designing PBRs as a function of the operational variables are given. The biomass productivities obtained during an annual cycle in an industrial size tubular PBR built according to the proposed methodology are presented, both as experimental measurements and as model predictions. The solar efficiency of microalgal cultures is also analyzed, and the phenomena limiting it are discussed. Finally, some considerations about the management and operation of industrial scale cultures of microalgae are given.
Microbial Metabolite Export
Authors: Eggeling Lothar
Published: April 2010

Microbial metabolite export is an essential issue in industrial biotechnology. The reason is simple: otherwise, the development of advanced engineered strains might fail. Export belongs to the entire reaction sequence of substrate uptake and conversion to the valuable product finally accumulating in the medium. The relevance of export is probably best studied in the case of amino acid production withEscherichia coliorCorynebacterium glutamicumwhere specific exporters, when deleted, prevent amino acid production, or when overexpressed, increase amino acid production. However, antibiotic production also relies on exporters as the final step in cellular synthesis of these important metabolites. Another area where the importance of exporters is assessed is the use of whole cells for bioconversions occurring in organic solvents. This review covers these areas, gives a tabular overview on exporters recognized in biotechnology and describes also the varied methodology of exporter identification.
Cell Disruption, Microbial, Micromechanical Properties
Authors: Kampen Ingo , Kwade Arno
Published: April 2010

In the production of intracellular products, a cell disruption step in the downstream processing is necessary for product release. While in the past, cell disruption behavior was simply measured with different devices, today the microprocess within these devices is the focus of interest. This contribution summarizes current results of microbial micromechanical properties and briefly discusses the methods used for measurements. The industrially relevant cell disruption devices in a high pressure homogenizer, stirred media mill and ultrasonic homogenizer are introduced, their cell disruption mechanisms are discussed and their different applications compared. The impact of the results of micromechanical measurements on cell disruption devices will be discussed.
Halophiles, Industrial Applications
Authors: DasSarma Priya , Coker James A. , Huse Valerie , DasSarma Shiladitya
Published: April 2010

Halophilic (salt‐loving) microorganisms have evolved physiological and genetic characteristics for success in their harsh saline environments. These characteristics include internal compatible solutes, efficient ion pumps, UV absorbing pigments, and acidic proteins, which help them to resist osmotic stress and the denaturing effects of salts, as well as the accompanying intense solar radiation. Many of the same characteristics which help them to counteract the deleterious effects of their environment also constitute valuable resources for biotechnology and nanotechnology. Although currently established applications of halophiles are limited primarily to compatible solutes in the cosmetic industry, and β‐carotene and hydrolases in the nutritional and food industries, many other novel applications are under development. They include specialized applications for films of bacteriorhodopsin from halophiles for a variety of optical nanodevices, including high‐capacity computer storage, and for stable enzymes from halophiles for use as industrial catalysts, some capable of functioning in organic solvents. Metabolic activities of halophiles are also being tapped for a variety of environmental applications, such as bioremediation of pollutants in saline wastewaters. Some subcellular components, such as polyhydroxyalkanoate granules, gas vesicles, and phospholipid vesicles, and bioactive compounds like halocins are being developed for medical applications. Applications of halophilic microorganisms are varied and represent significant commercial opportunities in the chemical, environmental, biofuel, medical, and educational industries.
Mixed Culture Processes
Authors: Shioya Suteaki
Published: April 2010

In this article, some of the mixed culture systems are introduced to show their potential for effective bioproduction, their application in nisin and kefiran production processes and utilization of ligno‐cellulosic biomass. Nisin is an antimicrobial peptide produced byLactococcus lactis. Nisin production was growth‐associative but the growth of lactic acid bacteria was inhibited by the decrease in pH and lactate accumulation. To prevent decrease in pH as well as accumulation of lactate, a yeast,Kluyveromyces marxianus, isolated from a type of yogurt, kefir, was co‐cultured. This yeast can assimilate the excess lactate. Since lactate concentration in the medium could be maintained at a low level and pH level could be kept optimal by a pH control system developed here,L. lactisgrew with a high specific growth rate. By applying this strategy, a high accumulation of nisin was obtained.

In the kefiran production process,Lactobacillus kefiranofaciensand Saccharomyces cerevisiae, are co‐cultured for enhancement of productivity.L. kefiranofaciensproduces an exopolysaccharide called kefiran, which contains approximately equal amounts of glucose and galactose. Bacterial polysaccharides are usually associated with the outer surface of the bacterium. They may either form an amorphous layer of polysaccharides called capsular kefiran in the form of a capsule surrounding the cell, or be excreted into the medium as extracellular kefiran. Co‐culture with S.cerevisiaeenhanced the capsular kefiran production, which resulted in increased production of total kefiran.

From the composting of an aquatic plant, a cellulose‐degrading microorganism was isolated and identified asThermobifida fusca. This strain was applied to reconstruct the composting as a responsible microorganism was not successful. The aid of another microorganism,Ureibacillus thermosphaericus, was found to be necessary. The role of the strain has been revealed in this article and the microorganisms will be useful for pretreatment of ligno‐cellulosic biomass for further applications such as bio‐ethanol production.

Now mixed culture systems should be re‐reviewed as a potential system for effective bioproduction.
Monocots, Tissue Culture
Authors: Neelwarne Bhagyalakshmi , Brettell Richard
Published: April 2010

Monocots (monocotyledonous plants) are one of the two major divisions of flowering plants, and are characterized by having parallel‐veined leaves and an embryo with a single cotyledon. Techniques of tissue and cell culture have been successfully applied to a wide range of monocot species, which include cereals and other grasses, lilies, orchids, and palms. The techniques described in this article include callus culture, cell suspension culture, regeneration of plants, protoplast culture, anther and pollen culture, and shoot tip and meristem culture. The article also covers practical applications that use technologies based on tissue and cell cultures. Examples are the rapid propagation of clonal plants, and the production of doubled haploid plants for plant breeding. Genetic transformation has also been achieved through application of tissue and cell culture techniques to grasses and cereals, bananas, pineapples, onions, garlic, and duckweeds. A further application under development is the industrial production of secondary metabolites.
Monooxygenases,Baeyer–Villiger Applications in Organic Synthesis
Authors: Rehdorf Jessica , Bornscheuer Uwe T.
Published: April 2010

In this article the occurrence and biochemical properties of Baeyer–Villiger monooxygenases is reviewed. The main emphasis is on their application in organic synthesis for the production of optically pure compounds by desymmetrization processes, kinetic resolutions, and regiodivergent reactions. Furthermore, recent advances in technical approaches for efficient cofactor regeneration are covered. Finally, industrial applications of selected examples with BVMOs (Baeyer–Villiger monooxygenases) as well as improvements in large‐scale production are provided, followed by an overview about recent directed evolution and rational protein design approaches.
Optical Resolution, Biocatalysis
Authors: Omata Tetsuo , Senda Shuji , Ninomiya Yasuo
Published: April 2010

Introduction

Optical Resolution with Lipase‐Catalyzed Transesterification

Optical Resolution with Lipase‐Catalyzing Hydrolysis

Optical Resolution by Lipase‐Catalyzing Esterification

Optical Resolution by Hydantoinase‐Catalyzing Hydrolysis

Optical Resolution by Oxidoreductase‐Catalyzing Oxidation and Reduction

Conclusion

References
Secondary Alcohols, Optically Active, Micorbial Production
Authors: Yamada‐Onodera Keiko
Published: April 2010

The usefulness of optically active substances has been recognized in various fields, and recently the differences between enantiomers are becoming clear especially in medical supplies. The necessity for the enantioselective synthesis has been increasing. The advantages of biocatalysis over chemical synthesis are that enzyme‐catalyzed reactions are highly enantioselective and that they can be performed at ambient temperature and atmospheric pressure, thus avoiding the harsh conditions which cause isomerization, racemization, epimerization, and rearrangement. A lipase has been used to produce optically active secondary alcohols because it has the ability to catalyze hydrolysis of ester bonds with high enantioselectivity. The enantioselective ketone‐reduction and alcohol‐oxidation by secondary alcohol dehydrogenase have been also of interest for the production of various chiral alcohols. Many Alcohol dehydrogenases (ADH) used for this purpose are nicotinamide adenine dinucleotide (NAD) or nicotinamide adenine dinucleotide phosphate (NADP) dependent. Several trials have been achieved for improvement of efficiency mainly in coenzyme recycling. Whole cell reaction is advantageous with respect to saving expensive purification of the desired enzymes. Desired enzymes can be expressed in transformants to make biocatalytic processes economically efficient. Preparative application for industrial purpose will be demonstrated.
Oxygen Transfer Rate Determination: Chemical, Physical and Biological Methods
Authors: Garcia‐Ochoa Felix , Gomez Emilio
Published: April 2010

A proper mechanical design of the bioreactor is aimed at maintaining the environmental and nutritional conditions for optimal growth and/or product formation. Among the various environmental and nutritional factors that influence the aerobic bioprocess, oxygen is a critical parameter since it is the only nutrient that has to be provided continuously, even in batch cultures.

The oxygen transfer rate (OTR) determination is essential in order to establish aeration efficiency and to quantify the effects of the operation variables on the requirement of oxygen since dissolved oxygen concentration is dependent on transport processes. Under these conditions OTR (andKLa) is one of the key parameters involved in the design, operation, and scale‐up of bioreactors

There are several approaches to determine OTR. The most common measuring methods applied can be classified depending on whether the determination is realized in the absence of microorganisms or with dead cells (chemical and physical methods), or in the presence of biomass that consumes oxygen at the same time that the measurement is carried out (biological methods).

Sometimes when OTR from a physical method is determined, it must take into account the enhancement factor,E. In recent literature predictive methods have been proposed to calculatekLaandE, and thus find the value of OTR. This approach is much more reliable than those based on the use of empirical equations.

In this chapter, OTR description is discussed and the main experimental methods forkLadetermination are described; recent predictive methods forkLaandEare also presented.
Pantothenic Acid and Related Compounds
Authors: Shimizu Sakayu , Kataoka Michihiko
Published: April 2010

Chemistry and biochemistry of D‐pantothenic acid and related compounds are described. Several biocatalytic reactions were successfully applied to the production of D‐pantothenate and coenzyme A.
Peptides
Authors: Von Döhren Hans
Published: April 2010

Peptides are oligomers and defined polymers of amino acids, and key players in life processes. Tailoring reactions lead to diverse structural types with various bioactivities. Properties range from antibiotics and other pharmaceuticals to hormones and nanomaterials. Biotechnical manufacturing involves complex ribosomal and enzymatic processes.
Plant Cell Culture, Secondary Product Accumulation
Authors: Zhou Xin , Zhong Jian‐Jiang
Published: April 2010

Plant cell culture is an effective technology for the production of valuable plant‐derived secondary metabolites which can be used as pharmaceuticals, food additives, nutraceuticals, etc. The biosynthesis of secondary metabolites by cell culture is safe, controllable, and economical in contrast to field cultivation of their parent plants; but it is also affected by many internal and external factors. In this chapter, the background of secondary product accumulation by plant cell culture is overviewed at first. The progress in recent years toward manipulation of environmental factors, bioprocessing strategies, and elicitation and signal transduction engineering are summarized with typical examples for each case. Furthermore, advances in modulation of secondary metabolite accumulation including heterogeneity engineering, metabolic engineering, and omics study of secondary metabolite biosynthesis, are also reviewed. Further developments in rational bioprocessing and in systems biotechnology of plant cells for metabolite production are expected in the future.
PlasmidDNAReplication
Authors: Tolmasky Marcelo E. , Actis Luis A. , Crosa Jorge H.
Published: April 2010

Plasmids are extrachromosomal replicons found in gram‐negative and gram‐positive bacteria as well as in some lower eukaryotic organisms. They are present in bacterial cells replicating at a specific number of copies per cell. Their size varies from a few to several hundred kilobase pairs and bacterial cells can harbor more than one plasmid species. The medical importance of plasmids that code for antibiotic resistance and those that contribute directly to microbial pathogenicity is well‐documented, is the role played by plasmids in bacteria of importance in agriculture and industry. These extrachromosomal elements are of equal importance, however, for the study of the structure and function of DNA. Plasmids utilize a wide variety of strategies to initiate and regulate their replication. In this chapter we examine the replication of plasmids ColE1, whose replication system is part of most plasmids vectors; R6K, an iteron‐containing plasmid that possesses three replica origins; plasmids belonging to the RepABC family found in a‐proteobacteria; and of pT181, a group of plasmids found in gram‐positive bacteria. In addition,we also discuss linear plasmids.
Bioprocess Monitoring
Authors: Carloni A. , Turner Anthony P.F.
Published: April 2010

Bioprocess monitoring is required in order to develop, optimize and maintain biological process at optimum efficiency. This contribution briefly overviews the main technologies in current use and under development to measure the physical and chemical parameters critical to optimum production. The types of devices currently available are described together with their operating principles. New sensing technologies that could revolutionize the industry by facilitating the production of new products or by radically improving yields of high‐value added materials are also reviewed.
L
‐Amino Acids Production by Aminoacylase
Authors: Sato Tadashi , Tosa Tetsuya
Published: April 2010

Optical resolution of racemic amino acids can be carried out by physicochemical, enzymatic, and biological methods. Chemically synthesized acyl‐
DL
‐amino acid is asymmetrically hydrolyzed by aminoacylase to give
L
‐amino acid and the unhydrolyzed acyl
D
‐amino acid.
Protein Glycosylation
Authors: Brooks Susan A.
Published: April 2010

More than half of the proteins synthesized by humans are glycosylated. That is, the proteins have one or moreN‐orO‐linked glycan chains attached to them. Proteins are naturally synthesized in a range of glycoforms, and their glycosylation profile influences their activity, stability, immunogenicity, serum half life, and other biological properties. While the general mechanisms of human protein glycosylation are well established, what influences the fine control of glycosylation patterns is not well understood. Furthermore, the cells of organisms other than humans glycosylate their proteins differently. This is of interest to the biotechnology industry, which commonly uses nonhuman cells for protein expression. Proteins expressed in cells of nonhuman species are glycosylated differently to how they would be by human cells and this is of particular relevance to expression of glycoproteins destined for potential administration to humans. Inappropriate glycosylation profiles result in altered and undesirable pharmokinetic properties. In this chapter, the mechanisms of human protein glycosylation are explained. Glycosylation in cells of nonhuman species, including prokaryotes, fungi and yeasts, insects, plants, and mammals other than humans are introduced, with an emphasis on glycosylation differences of importance to the biotechnology industry. Important advances in engineering glycosylation in nonhuman cell expression systems are highlighted.
Pullulan, Microbial Production Methods
Authors: Lin Yun , Thibault Jules , Leduy Anh
Published: April 2010

Pullulan is a water‐soluble polysaccharide produced through fermentation withAureobasidium pullulans. Pullulan has been used as specialty food for decades in Japan. Owing to its relatively high price, recent developments on pullulan are mainly focused on its application in biomedical engineering and pharmaceutical industry. Both laboratory and commercial pullulan production methods are reviewed. Among several problems associated with pullulan fermentation, the highly viscous fermentation broth remains the biggest challenge. The viscous non‐Newtonian broth creates major difficulties in mixing, oxygenation, process monitoring, sampling, and downstream product recovery. Many approaches to improve the fermentation efficiency have been attempted. One promising method is to use close clearance impellers, such as reciprocating plate mixer, instead of standard Rushton turbines in order to achieve more uniform mixing. Other unconventional techniques, such as cell immobilization, hyperbaric fermentation, and nonsterile fermentation, have also been discussed. However, these technologies need more research and investigation before they can be implemented at an industrial scale.
Rheology of Filamentous Microorganisms, Submerged Culture
Authors: Papagianni Maria
Published: April 2010

The article discusses the factors that affect the rheological behavior of filamentous fermentation broths, rheological measurements, rheological models, control of the rheological properties of filamentous fermentations, and instrumentation. The rheological characteristics of a fermentation broth affect directly its mixing behavior and all forms of mass and heat transfer. This can have a profound influence not only on the course and outcome of fermentation but also on the response of sensors used for monitoring and control. Beyond fermentation, the rheological properties of the final culture broth make a major determinant of the ease or difficulty of downstream processing. Rheological properties are determined mainly by the concentration of biomass and fungal morphology. The filamentous growth form is the dominal morphological form in most processes. Long, thin, branched filaments create a network that gives very viscous fermentation broths with a pronounced non‐Newtonian character. Although the influence on the rheological properties of the broth on bioreactor performance is widely recognized, systematic studies of the rheological properties and the use of rheometry in fermentation processes are still limited. On‐line rheometry and image analysis applications in morphological studies have been valuable tools and provided a better understanding of the relationship between rheology and morphology. However, comparisons of data from different sources are rather problematic because of the different applied methods and instruments and the different morphological parameters evaluated. A wide variety of rheometers is available in the market today and it is expected that the area of fermentation broth rheology will be benefited in the future from advances in micro‐ and nanofluidics applications. Such applications are expected to provide precise control over experimental conditions and in‐depth rheological information on the studied systems.
Scale‐Up, Stirred Tank Reactors
Authors: Nienow Alvin W.
Published: April 2010

Scale‐up is best approached by considering the need to provide the optimum environment for the cell. It is inevitably a compromise and needs appropriate small‐scale data as discussed here. However, arbitrary and inflexible “scale‐up rules” are not useful. The most critical aspects of scale‐up are oxygen and carbon dioxide mass transfer and their concentration in the broth, all of which depend on the air sparge rate and power input from the selected impeller(s). The Rushton turbine is discussed followed by the now‐preferred hollow‐blade and up‐pumping, high solidity ratio hydrofoils. Bulk blending/homogeneity (especially at the high aspect ratios found on the commercial scale), holdup, and foaming and heat transfer in turbulent conditions as found with small‐sized microorganisms are considered, followed by the additional complexity that arises with these parameters when dealing with high viscosity, rheologically complex broths with mycelial and biopolymer fermentations. The impact of scale‐up on two aspects of bioperformance is considered, namely, mechanical stress from agitation and stresses from the inevitable poorer homogeneity. It is concluded that mechanical stresses are only important with mycelial fermentations and the impact depends on the organism. Stresses due to spatial differences in dO2and in pH batch fermentations, as well as nutrients in fed batch, cause a poorer performance at the commercial scale. Such information is vital for enabling a realistic appreciation beforehand of the likely large‐scale bioperformance, and for guiding design. Finally, with the present understanding of the physical and biological aspects of bioprocesses, computational fluid dynamics (CFD) is unlikely to be able to significantly improve it.
Suspension Culture, Animal Cells
Authors: Birch John R.
Published: April 2010

Suspension culture has become the method of choice for the production of a wide range of therapeutic proteins and a number of vaccines. Some recombinant proteins, particularly antibodies, are required in quantities of hundreds of kilograms and even tons per annum. To meet these demands, industrial processes up to 20,000‐L scale have been developed based on stirred reactors, typically operated in batch or fed‐batch mode. For antibodies, optimization of fed‐batch processes has led to very high productivity, and yields of grams per liter are frequently reported. Continuous, perfused systems are also used. Several types of cells are used in these suspension processes, the most common being CHO. It is now possible to grow CHO and other cell types in large‐scale suspension culture using chemically defined media that contain no proteins or animal‐derived materials.
Transcription, Translation, and the Control of Gene Expression in Mammalian Cells
Authors: Mullick Alaka , Massie Bernard
Published: April 2010

The last few years have seen rapid progress in the field of gene expression, and at least part of the motivation has come from the domain of biotechnology, wherein, recombinant proteins have become important players in therapeutics. Depending upon the stage of development, there may be a need for small quantities of several related proteins or extremely large quantities of a restricted number of proteins. In either case, protein expression systems are essential. It has been possible to develop efficient expression systems because of the phenomenal increase in our understanding of the molecular mechanism that are involved in gene expression. Of interest is the fact that recent findings are not limited to defining further details of known processes, certain advances, such as the role of chromatin in DNA biochemistry and RNA silencing, have revolutionized the way we think about gene expression.
Vent Gas Analysis
Authors: Pollard David , Christensen Jens
Published: April 2010

The monitoring of exhaust gas provides a universal method for fermentation characterization as most biological processes involve exchange or consumption of gases and volatile compounds. The monitoring of gas concentrations, such as carbon dioxide and oxygen, in the entry inlet and outlet gas streams and incorporation into liquid and gas balances makes it possible to quantify rates of gas utilization on production and respiratory quotient. This allows online real time monitoring of the physiological state of the fermentation, including growth kinetics and substrate consumption. A range of measuring methods for vent gas analysis are described including industrial application examples.
Viral Vaccine Production in Cell Culture
Authors: Auniņš John G.
Published: April 2010

Cell culture for the purposes of viral vaccine cultivation is reviewed from the perspective of the industrial practitioner. This article covers the mechanics of virus production, followed by a discussion of the steps in virus replication, process affectors of virus cultivation. It concludes with a series of examples of virus vaccine processes, emphasizing the principles discussed in the previous sections as they translate to industrial practice.
Baculovirus Kinetics, Insect Cell Culture
Authors: Chan Leslie , Reid Steve , Keld Nielsen Lars
Published: April 2010

Viral‐based processes continue to represent an important class of cell culture processes. Indeed, the number of viral‐based cell culture processes is increasing with (a) viral vaccine production moving from primary cells to continuous cell lines, (b) increased use of viral biopesticides, (c) increased use of viral expression systems, and (d) the use of viral gene therapy vectors. The inherent complexity combined with the problems of working with human or animal pathogens has meant that the academic treatment of viral production kinetics has lagged behind that of other cell culture systems. The emergence of the baculovirus (an innocuous insect virus) for protein expression changed this situation and the baculovirus is used throughout this article to illustrate how to handle complex viral kinetics. Emphasis is placed on the development of mathematical models, which are essential tools when studying viral production kinetics.
Water and Wastewater Treatment, Automation
Authors: Olsson Gustaf
Published: April 2010

Advanced control is increasingly in demand in water and wastewater treatment systems. Various case studies have shown significant savings in operating costs, including energy costs, and remarkably short pay back times. It has been demonstrated that instrumentation, control, and automation (ICA) may increase the capacity of biological nutrient removing wastewater treatment plants by 10–30%. With further understanding and exploitation of the mechanisms involved in biological nutrient removal, the improvements due to ICA may reach another 20–50% of the total system investments within the next 10–20 years.
Carbonyl Reductase
Authors: Hiroaki Yamamoto
Published: April 2010

Optically active alcohols are very useful as building blocks and intermediates for the syntheses of fragrances, agricultural chemicals and, especially, pharmaceuticals. The synthesis of chiral alcohols by enzymatic asymmetric reduction is a powerful and versatile method. Chiral Alcohols are catalyzed by enantioselective alcohol dehydrogenases, carbonyl reductases, and microorganisms containing responsible enzymes. In this review, a variety of the enzymes, their applications, and regeneration methods of coenzymes, NAD(P)H, are summarized.
Enzymatic Synthesis of Chiral Drug Intermediates
Authors: Patel Ramesh N.
Published: April 2010

Chirality is a key factor for the safety and efficacy of many drug products, and thus the production of single enantiomers of drug intermediates has become increasingly important in the pharmaceutical industry. There has been an enormous potential of microorganisms and enzymes derived therefrom for the transformation of synthetic chemicals with high chemo‐, regio‐, and enatioselectivities. In this article, chemoenzymatic processes, are described, for the synthesis of chiral intermediates for development of pharmaceuticals.
Fluorescence Techniques for Bioprocess Monitoring
Authors: Anton Fabienne , Lindemann Carsten , Hitzmann Bernd , Reardon Kenneth F. , Scheper Thomas
Published: April 2010

Modern bioprocess control requires instantaneous data acquisition and in‐time evaluation of bioprocess variables. Optical sensor systems are of increasing interest in bioprocess monitoring because they are very sensitive and offer the possibility of on‐line,in situ, and noninvasive process monitoring. In this regard, on‐line fluorescence spectroscopy is a useful tool in the development of methods for bioprocess monitoring because many cellular substances and media components are biogenic fluorophors. This technique and the application of chemometric methods offer a deeper insight into biological processes and thus process monitoring, optimization, and control is accessible. In this review, an overview of the developments and applications of on‐line fluorescence techniques for bioprocess monitoring over the last 25 years is given with emphasis on 2D fluorescence spectroscopy.
Impeller Selection for Animal Cell Culture
Authors: Nienow Alvin W.
Published: April 2010

Impellers in animal (mammalian and insect) cell culture bioreactors essentially have to meet the same tasks as impellers in other bioreactors. However, there are special features of both free suspension and microcarrier cell culture that lead to particular agitation conditions compared to the others. Even at

, the oxygen transfer requirements are very modest and hence so are the specific power input and aeration rate. Because they lack a cell wall, the cells are also perceived to be easily damaged by agitation, which also encourages low levels of these parameters and the selection of “low shear” impellers. Here, it is shown that the concept of “low shear” impellers is misleading and that in free suspension, animal cells are quite robust. Thus, almost any impeller can be chosen. However, if all the tasks, especially homogenization, that impeller(s) have to achieve are considered, certain impeller/vessel characteristics emerge, namely, dual axial flow impellers in a baffled vessel of aspect ratio between about 1 and 1.3, with subsurface feeding. In addition, an open pipe or ring sparger plus variable speed, and moderately overpowered motor are recommended. For microcarriers, the sparse literature suggests that mechanical damage to the cells is significant and related literature on abrasion involving similar particles supports this conclusion. A suitable impeller/vessel configuration to ensure efficient microcarrier suspension is recommended but at this agitation intensity, inhomogeneity, mass transfer, other mixing issues are likely to arise. It is suggested that more work is required on such systems.
Bioreactors, Cell Culture, Commercial Production
Authors: Zhou Tan‐Che , Zhou Wen‐Wen , Hu Weiwei , Zhong Jian‐Jiang
Published: April 2010

Various recombinant proteins expressed by animal cells and secondary metabolites produced by plant cells have significantly increased the demand for high‐value‐added (mainly biopharmaceutical) products in recent years. Without doubt, large‐scale efficient production of these compounds is very important to meet market requirements. As animal cells and plant cells are more sensitive to culture conditions than microorganisms, their bioreactor culture technique is critical to reduce the production cost. In order to favor the desired functions of the cells and achieve cost‐effective large‐scale manufacture, it is necessary to optimize and control the bioreactor environment via operating variables. In this article, the characteristics of various types of cell culture bioreactors including stirred‐tank bioreactors, pneumatically agitated bioreactors, membrane bioreactors, packed and fluidized‐bed bioreactors, and wave bioreactors are discussed. Details of basic bioreactor design principles such as shear force, oxygen supply, and mixing are introduced. The effects of process variables including oxygen and mass transfer, fluid mixing, temperature, pH, and light irradiation on cell cultures are described. Bioreactor operation strategies for cell cultures are compared. For commercial production scale‐up, different criteria are considered and industrial large‐scale examples are also illustrated.
Expanded Bed Chromatography, Surface Energetics of Biomass Deposition
Authors: Fernández Lahore Marcelo , Aguilar Oscar , Reddy Vennapusa Rami , Aasim Muhammad
Published: April 2010

The introduction of Expanded Bed Adsorption (EBA) system has made biochemical engineers face the challenge of operating a “chromatography” in the presence of biomass and other particulate components which are normally present in a crude, unclarified, feedstock. This situation can lead to detrimental consequences in terms of increased adsorbent fouling, decreased adsorbent binding capacity, and poor bed hydrodynamics. Biomass and other suspended biological material can be very sticky, depending on the type of adsorbent employed and the solution chemistry involved and thus, can create severe limitations during processing.

A better local understanding of biomass deposition, including the two separate cell‐to‐bead (“interaction”) and cell‐to‐cell (“aggregation”) phenomena has been developed to allow for safer EBA operations. To this end, we propose a surface energetics‐based approach. As per the XDLVO theory, free interfacial energy versus distance profiles were calculated for a large combination of model biomass and adsorbent bead types. The energy minima values (absolute value/U) obtained for each of the analyzed cases were correlated with the corresponding deposition coefficient values (α). A positive correlation was obtained. It was concluded that total interaction energyU ≤ − 25 to  − 50 kT and biomass deposition parameter α ≤ 0.15 would be a safe region for EBA operation; for example, biomass interference can be neglected. Deviation in the correlation was found in such cases where moderate or high cell‐to‐cell aggregation occurs, for example, in hydrophobic interaction systems. In the later cases, laser diffraction studies were necessary to fully characterize the system.

These novel tools will help in alleviating the current EBA technical constraints and will guide the design of more efficient adsorbent types.