Isolation And Identification Of The Strains Producing Nitrile-Degrading Enzyme

Nitriles are an economically important class of chemical industrymaterials. Biotransformation of nitrile compounds to corresponding acidand amide could provide key intermediates for pharmacy, food,agrochemical and fine industry. This dissertation is aimed to isolate somemicroorganisms with such capacity and do some identification researchwhich is valuable for future enzyme study and industry applications.Twenty-two microorganisms were isolated with high nitrile degradi-ng enzyme activity against p-hydroxybenzylcyanide, 2,2-dimethylcyclo-propanecarboxnitrile or 2,2-dimethylcyclopropanecarboxamide. And themorphology of these microorganisms were also studied which will beuseful for its further study. According to the morphology, physiologicaltest, ATB system and the 16S rDNA gene sequence analysis. Strain 12,H136f and ZJB-05174 were respectively identified as Bacillu scereus,Arthrobacter nitroguajaclicus and Delftia tsuruhatensis .And strain N595and F79 are both identified as Nocardia sp. Optimum culture conditions for the production of S-amidase byBacillus scereus 12 were studied. The acyl transfer reaction catalyzed byamidase was employed to determine the correspondence hydrolysisactivity. The optimum culture conditions were as follows（g/L）: glucose12.5, yeast extract 3, peptone 4, KH₂PO₄1, K₂HPO₄ 1, NaCl 1,MgSO₄·7H₂O 0.2, FeSO₄·7H₂O 0.01,ε-caprolactam 2. When Bacilluscereus 12 was cultivated for 60h at 30℃in the optimum cultureconditions, the specific enzyme activity was 4.612 U/ml of culture broth,which was 1.98 times higher than when cultured under initial conditions.And it showed that Bacillus cereus 12 amidase was a inducible enzymeand the metal ions such as iron and magnesium are essential.