Whole-cell catalysts nitriles

In recent years, the enantioselective hydrolysis of nitriles has been studied in more detail. Whereas in the past only whole cell catalysts had been investigated, it is now possible to assign the activities to specific enzymes occurring in the cell. These enzymes are nitrilases, nitrile hydratases and/or amidases. 

The same whole cell catalyst can be used in the hydration of 3-cyanopyridine to nicotinamide (Scheme 12.1-17). This vitamin, broadly applied in animal feeding, is currently produced biocatalytically on an industrial scale (> 3000 t/a) by the Lonza AG. For this substrate Yamada and Kobayashi showed that the whole cell catalyst of Rhodococcus rhodocrous Jl, containing a nitrile hydratase induced with crotonamide, can even tolerate substrate concentrations up to 12 m 121 (see Fig. 12.1-3). 

Various nitrile hydratases are continued to be developed and compared to the existing wdld-type whole-cell catalysts (R. rhodochrous Jl) presently used in the commercial production of acrylamide from acrylonitrile. Mitsubishi Rayon has produced mutant enzymes of R. rhodochrous Jl with significantly improved thermal stabilities and ca ytic activities at 50-70°C [233,234]. Saint-Etierme France has licensed and commercialized the mamrfacture of acrylamide using Mitsubishi Rayon s immobilized R. rhodochrous ]l [235] and has independently developed a Rhodococcus pyridinovorans whole cell catalyst for this process [236]. 

Another example in which a biocatalytic transformation has replaced a chemo-catalytic one, in a very simple reaction, is the Mitsubishi Rayon process for the production of acrylamide by hydration of acrylonitrile (Fig. 1.42). Whole cells of Rhodococcus rhodocrous, containing a nitrile hydratase, produced acrylamide in >99.9% purity at >99.9% conversion, and in high volumetric and space time yields [121]. The process (Fig. 1.42) currently accounts for more than 100000 tons annual production of acrylamide and replaced an existing process which employed a copper catalyst. A major advantage of the biocatalytic process is the high product purity, which is important for the main application of acrylamide as a specialty monomer. 

During our longstanding interest in the biohydrolysis of nitriles, we found that whole cell preparations of certain Rhodococci, such as R. erythropolis A4 (formerly R. equi A4), R. sp. R312, and R. erythropolis NCIMB 11540, containing the nitrile hydratase/amidase enzyme system, are efficient catalysts for stereoselective microbial hydrolysis of N-protected carbocyclic P-amino nitriles ( )-la-( )-4a, to P-amino acids lc-4c and amides lb-4b, respectively (Scheme 15.1) [33, 34]. 

Catalyst A copper salt the enzyme nitrile hydratase in whole cells of Rhodococcus rhodochrous, immobilized on polyfpropenamide) gel... 

DuPont practices biocatalytic hydrolysis of nitriles using immobilized whole cells of P. chloioiaphis B23. The catalyst consumption is 0.006 kg/kg product. The conversion is higher and so... 

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