Biological process for preparing optically active lactic acid

DETAILED DESCRIPTION OF THE INVENTION The microorganism used in the present invention is a microorganism belonging to the genus Enterobacter, Arthrobacter, Caseobacter, Brevibacterium, Aureobacterium, Escherichia, Micrococcus, Streptomyces, Flavobacterium, Aeromonas, Nocardia, Mycoplana, Cellulomonas, Erwinia, Candida, Pseudomonas, Rhodococcus, Bacillus, Alcaligenes, Corynebacterium, Microbacterium or Obsumbacterium, which is capable of stereospecifically hydrolyzing a nitrile.
Those microorganisms can be obtained, for example, by the following process.
(1) Isolation of Strains The soil collected at Yokohama-shi of Kanagawa, Japan is suspended in 15 ml of a sterilized water and allowed to stand for 30 minutes.
Then, 0.
1 to 0.
2 ml of the resulting supernatant is sprayed on an agar medium containing 2-chloropropionitrile as a nitrogen source (20 g of glycerol, 1 g of 2-chloropropionitrile, 3 g of K.
sub.
2 HPO.
sub.
4, 0.
2 g of MgCl.
sub.
2, 40 mg of CaCl.
sub.
2, 4 mg of MnSO.
sub.
4.
4H.
sub.
2 O, 0.
7 mg of FeCl.
sub.
3.
7H.
sub.
2 O; 0.
1 mg of ZnSO.
sub.
4.
7H.
sub.
2 O and 15 g of agar in 1 l of demineralized water (pH 7.
0) and then cultured at 30.
degree.
C.
for 5 to 6 days.
The colonies formed are purely isolated on the agar medium.
(2) Assay of Activity The thus-obtained strains are cultured in the same manner as in Example 1 below and reacted with a lactonitrile.
After completion of the reaction, the system is subjected to centrifugation to remove the microbial cells.
The supernatant liquor is analyzed by liquid chromatography (column: SHODEX ODS F511A, carrier: 0.
2M H.
sub.
3 PO.
sub.
4, column temp.
: 30.
degree.
C.
, monitor wavelength: 208 nm) to determine an amount of lactic acid produced.
In addition, its optical purity is determined in the same manner as in Example 1 below.
Specific examples of microorganisms which can be used in the present invention include Enterobacter sp.
SK12 (FERM No.
BP-3322), Enterobacter taylorae JCM 3943, Arthrobacter sp.
SK103 (FERM No.
P-11300), Arthrobacter sp.
HR1 (FERM No