Screening of D-Hydantoinase-Producing Microorganism and Its Catalytic Properties

Abstract:

Hydantoinases are important enzymes with industrial potential in producing D-amino acids. In this study，6 strains with hydantoinase activity were selected from 23 wildtype microbial strains using 5'-monosubstituted hydantoin derivatives as induce substrates. Four 5'-monosubstituted hydantoins were chemically synthesized and verified with 1H-NMR. From 6 hydantoinase-producing strains，strain Pseudomonas fluorescenswas successfully identified with the highest enantioselectivity，desired substrate specificity and high activity in the hydrolysis of 5'-monosubstituted hydantoins andwas selected for further study. After induction with hydantoin substrates at 30 ℃ for 12 h，the D-hydantoinase activity could reach 92.1 U/L. The reaction condition was optimized to be 60 ℃ and pH 8.5，which was in favor of the spontaneous racemization of substrate. In a 50 mL whole-cell biocatalytic system，20 mmol/L D，L-p-hydroxyphenyl hydantoin was enantioselectively hydrolyzed by 0.25 g dry cells with a conversion ratioof 98% within 3 hours.