Conversion of a cyanhydrin compound into S-(-)-3-phenyllactic acid by enantioselective hydrolytic activity of Pseudomonas sp BC-18

A Pseudomonas strain, named BC-18, which can convert racemic phenylacetaldehyde-cyanhydrin (3-phenyllactonitrile) enantioselectively to S-(-)3-phenyllactic acid (S-PLA), was isolated from soil. Although PLA produced with intact cells contained the S enantiomers of approximately 75% enantiomeric excess (% e.e.), repeated crystallization gave a higher purity (99.8% e.e.) of the S configuration product. Production of S-PLA was significantly increased when 2.0% (w/v) of calcium chloride were added to the reaction mixture for precipitation of S-PLA. Chemical mutagenesis yielded a mutant strain, named BC348-9, with 16 times higher activity (40 mU/OD630), compared with that of the parent strain (2.5 mU/OD630), When the mutant strain BC348-9 was used, approximately 18 g/OD630 was produced, which is 12 times higher than that of the parent strain. The final accumulation of PLA exceeded 6.0%, 1.2 times higher than that of the parent strain.