Biotransformation whole cell based

Bacteria, Aberdeen, UK), was found to have a highly active nitrile hydratase/amidase enzyme system, based on whole-cell biotransformation experiments. Subsequently, individual enzymes (nitrile hydratase and amidase) from this strain were cloned and expressed separately in E. coli However, distribution of some strains or other materials from these public collections may be limited, usually as a result of the restrictions on their commercial use imposed by intellectual property rights. 

As whole cell catalyst, Pseudomonas putida, which accepts a wide range of substrates, is applied. Subsequent to the biotransformation, benzaldehyde is added, resulting in precipitation of the D-amide Schiff base, which can be easily isolated by filtration. An acidification step leads to the D-amino acid. The L-amino acid can be reused after racemization so that a theoretical yield of 100% D-amino acid is possible. 

Acrylamide is the first bulk chemical manufactured using an industrial biotransformation. Acrylamide which is produced 200000 t/a is an important industrial chemical that is mainly processed into water-soluble polymers and copolymers, which find applications as flocculants, paper-making aids, thickening agents, surface coatings, and additives for enhanced oil recovery. The chemical manufacture of acrylamide has been established for a long time, it is based on Cu-catalysis. The production of acrylamide using immobilized whole cells of Rhodococcus rhodochrous is a remarkable example of a lyase-catalyzed commercial process. The enzyme responsible for water addition to the double bond of acrylonitrile is nitrile hydratase (Eq. 4-17) ... 

Compounds for biotransformation that are water-soluble, with ionizable and/or hydrophilic functional groups, are relatively easy to handle and can be added directly to the various types of whole-cell preparations, since they are located in aqueous-based environments. Some problems may arise above a threshold concentration with particular hydrophilic compounds, however, resulting either from the toxidty to srane micro-organisms... 

To overcome this obstacle, two different approaches have been exploited, both possessing benefits and disadvantages. For the isolated enzyme, a closed-loop system has been developed, where an auxiliary substrate has been added to regenerate NAD(P)H. The second approach is based on whole-cell-mediated biotransformations. 

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