ASYMMETRIC HYDROLYSIS OF R-(-),S(-2-METHYLBUTYRONITRILE BY RHODOCOCCUS-RHODOCHROUS NCIMB-11216())

Whole cells and cell-free extracts derived from Rhodococcus rhodochrou s NCIMB 11216 were shown to hydrolyse both aliphatic and aromatic nitr iles, when the organism had been grown on either propionitrile or benz onitrile as the source of carbon and nitrogen. Whole cell suspensions and cell-free extracts derived from bacteria grown on either substrate were able to biotransform R-(-),S-(+)-2-methylbutyronitrile. The S-() enantiomer was biotransformed more rapidly than the the R-(-) enanti omer. For whole cell biotransformations at 30 degrees C, the maximum e nantiomeric excess (ee) of the remaining R-(-)-2-methylbutyronitrile w as 93% when 70% of the R-(-) enantiomer had been converted to the prod uct, 2-methylbutyric acid. For the corresponding biotransformation at 4 degrees C, there was an ee of 93% for the residual R-(-) enantiomer of the substrate when only 60% of it had been converted to product. Fo r biotransformations by cell-free extracts at 30 degrees C the 2-methy lbutyric acid product had an ee of 17% for the S-(+) enantiomer at the time of optimal ee for the remaining R-(-) enantiomer of the substrat e. In contrast, when the reaction was carried out by whole cells, the ee for the product acid was 0.36%. This was probably due to further, n on-selective metabolism of the acid, which was especially significant at the beginning of the reaction. At both temperatures, the ee for the S-(+) enantiomer of 2-methylbutyric acid was at a maximum in the earl y stage of the biotransformation; for example, at 4 degrees C the maxi mum detectable ee was 100% when the yield was 11%.