CONDITIONS USED WITH A CONTINUOUS CULTIVATION SYSTEM TO SCREEN FOR D-HYDANTOINASE-PRODUCING MICROORGANISMS

The continuous cultivation technique has been used to screen for micro organisms producing D-hydantoinase, a biocatalyst involved in the prod uction of optically active amino acids. Pseudomonas putida strain DSM 84 was used as a model hydantoinase producer to establish selective cu lture conditions through the addition of various pyrimidines, dihydrop yrimidines, hydantoins and 5'-monosubstituted hydantoins. Thymine indu ced more activity than all cyclic amides tested. Addition of thymine a s a non-metabolised inducer at a concentration of 0.05 g l(-1) in a co ntinuous culture of P. putida stimulated hydantoinase production up to 80 times the basal level. Using continuous culture conditions establi shed with the model strain, a different strain of P. putida having hyd antoinase activity was isolated from commercial mixed cultures of micr oorganisms. DNA fingerprinting revealed that this new isolate was dist inct from strain DSM 84. When used as a probe, the D-hydantoinase gene of strain DSM 84 hybridized with the DNA of the new P. putida isolate .