Biocatalysts in organic chemical synthesis are many different types of microbes, each with unique nutritional and ological features, which may be desirable for process development; collectively, micro-organisms have a broad complement of enzymes capable of a of chemical production plants involving micro-organisms are generally independent of climatic conditions and require little space( compared to crop plant production) for some microbes, such as Escherichia coli, the genome is well known and relatively easy to manipulate genetically many microbes are single celled organisms that grow well in stirred tank bioreactors ]though it is possible to obtain cells from whole animals or plants and to cultivate them in suitable nutrient solutions, in general they are not as easy to handle as microbes Nevertheless, plant and animal cells are a valuable genetic resource for biotechnology and many newly developed bioprocesses rely on transfer of their genes to micro-organisms Microbial enzymes can be applied as catalysts for chemical synthesis in biosynthetic processes or in biotransformations(bioconversions). In a biosynthetic process the tion product is formed de novo by the microbial cell from substrates, such as monosaccharides, molasses, soybean and corn steep liquor. In a biotransformation, however, a precursor that is usually chemically synthesised is converted in one or several enzyme catalysed steps into the desired chemical. This chemical may be the end product or may serve as a precursor for further chemical modification 2. 3 Enzyme preparations versus whole cell processes In designing a process we have the choice of using the whole organism or specific enzymes isolated from it. As always both options have pros and cons. Broadly speaking we could say that biosynthetic processes mostly rely on whole cells, whereas biotransformations can be catalysed by whole cells and by enzyme preparations ydrolytic Hydrolytic enzymes such as proteases, esterases and lipases(Table 2.1)account for nzymes more than half of all reported biotransformations. These enzymes are particularly easy to use because: they are available in large amounts from industrial sources they are stable in non-aqueous solvent they do not have cofactor requirements Why do you think many processes based on redox reactions involving dehydrogenase enzymes are still carried out using whole cells? dehydrogenases Dehydrogenase enzymes generally require NADH or NADPH, and although methods for recycling these cofactors are now available on a laboratory scale, little progress has been made in the scale-up to industrial levelBiocatalysts in organic chemical synthesis 13 there are many different types of microbes, each with unique nutritional and physiological features, which may be desirable for process development; 0 collectively, micro-organisms have a broad complement of enzymes capable of a wide variety of chemical reactions; production plants involving micro-organisms are generally independent of climatic conditions and require little space (compared to crop plant produdion); 0 for some microbes, such as Esc/~m-ichia coli, the genome is well known and relatively easy to manipulate genetically; 0 many microbes are single celled organisms that grow well in stirred tank bioreactors (fermentors). Although it is possible to obtain cells from whole animals or plants and to cultivate them in suitable nutrient solutions, in general they are not as easy to handle as microbes. Nevertheless, plant and animal cells are a valuable genetic resource for biotechnology and many newly developed bioprocesses rely on transfer of their genes to micro-organisms. Microbial enzymes can be applied as catalysts for chemical synthesis in biosynthetic processes or in biotransformations (bioconversions). In a biosynthetic process the product is formed de novo by the microbial cell from substrates, such as monosaccharides, molasses, soybean and corn steep liquor. In a biotransformation, however, a precursor that is usually chemically synthesised is converted in one or several enzyme catalysed steps into the desired chemical. This chemical may be the end product or may serve as a pmrsor for further chemical modification. biosynthetic Pr-wsand bornsforin￾ation 2.3 Enzyme preparations versus whole cell processes In designing a process we have the choice of using the whole organism or specific enzymes isolated from it. As always both options have pro's and cons. Broadly speaking we could say that biosynthetic processes mostly rely on whole cells, whereas biotransformations can be catalysed by whole cells and by enzyme preparations. Hydrolytic enzymes such as proteases, esterases and lipases (Table 2.1) account for more than half of all reported biotransformations. These enzymes are particularly easy to use because: hydrolytic 0 they are available in large amounts from industrial sources; they are stable in non-aqueous solvent; they do not have cofactor requirements. Why do you think many processes based on redox reactions involving n dehydrogenase enzymes are still carried out using whole cells? Dehydrogenase enzymes generally require NADH or NADPH, and although methods for recycling these cofactors are now available on a laboratory scale, little progress has been made in the scale-up to industrial level. dehydrogenases