Biocatalysis strain

A strain of Pseudomonas aeruginosa has been recently described, which shows the opposite enantioselectivity, converting racemic arylaminonitriles efficientiy into the D-amino acids. Again, whole-cell biocatalysis worked well, the cells being entrapped in alginate beads. It is unclear whether this biotransformation involves an amide intermediate. 

Molecular cloning is now a standard procedure to overproduce specific enzymes of use in biocatalysis in a host microorganism that is suited for the process. The host strain should fulfil the objectives of downstream processing, which are high recovery, high purity, reproducibility and low cost scale-up. 

Whole-cell based biocatalysis utilizes an entire microorganism for the production of the desired product. One of the oldest examples for industrial applications of whole-cell biocatalysis is the production of acetic acid from ethanol with an immobilized Acetobacter strain, which was developed nearly 200 yr ago. The key advantage of whole-cell biocatalysis is the ability to use cheap and abundant raw materials and catalyze multistep reactions. Recent advances in metabolic engineering have brought a renaissance to whole-cell biocatalysis. In the following sections, two novel industrial processes that utilize whole-cell biocatalysis are discussed with emphasis on the important role played by metabolic engineering. 

Shu-Jen C. Strain improvement for fermentation and biocatalysis processes by genetic engineering technology.J Ind Microbiol Biotechnol 2004 31 99-108. 

Multistep biocatalysis for the preparation of optically pure epoxides was applied by Sello and coworkers [24, 25]. The commercially available 3-vinyl benzaldehyde was the substrate of choice for the synthesis of 3-(oxiran-2-yl) benzoic acid in high yields and optical purity by solely employing enzyme catalysis (Scheme 3.6). This goal was achieved by applying a mixed culture approach with different recombinant E. coli strains expressing, individually, both oxidizing biocatalysts. One strain contained a native ADH and a SMO from Pseudomonas Jiuorescens ST, while a second one expressed a naphthalene dihydrodiol dehydrogenase (NDDH) from P. Jiuorescens N3. 

The most commonly used hydrolase for biocatalysis is lipase B from C. antarctica (CAL-B). The commercial material is usually Novozym 435, which is protein immobilized noncovalently on an acrylic resin. This immobilization is suitable for use in organic solvents, but in water, the lipase desorbs from the support. CAL-B is a recombinant protein from the yeast C. antarctica produced in a strain of the fungus Aspergillus oryzae [5]. CAL-B shows little or no interfacial activation and hydrolyzes long chain triglycerides only slowly. For this reason, it may be better classified as an esterase It shows high activity and enantioselertivity toward a... 

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