Screening Of Strains Producing D-aminoacylase

D-amino acids are widely used for the production of some semisynthetic antibiotics, hormones, bioactive peptides and chemical pesticides. Their widespread occurrence among different microbes, plants and animals has also been confirmedand their physiological roles emphasised. Development and utilization of D-amino acids is a new hotspot in the field.It is economical to produce D-amino acids in large scale by chemical synthesis and chiral resolution. And resolution by aminoacylase is one of the best methods in the resolution of amino acids. It is a high efficient, green and safe method.D-aminoacylase (EC.3.5.1.81, N-D-AAase) with strict stereospecificity, which catalyses the hydrolysis of N-acyl-D-amino acids, should be a promising tool for the manufactvire of D-amino acids. We conducted a screening program for D-aminoacylase producing microorganisms from soil by using the isolation medium, which was composed of 1% N-acetyl-D-methionine. L-aminoacylase activity was estimated by using N-acetyl-L-methionine as the substract. One microbial strain B'3 with relatively high D-aminoacylase activity and stereospecificity was selected. Factors affecting the enzymatic activity were studied. Under the following conditions: temperature 37°C, pH 7.8, strain age 36h, the activity was up to 15U/ml.A high D-aminoacylase producing strain was selected from mutants after UV and NTG mutation, and the production of the enzyme increased from 15U/ml to 29.8U/ml. The medium composition for the mutants was optimized, and the activity was up to 74U/ml.Some Properties of the crude D-aminoacylase was studied. The optimal pH and temperature of D-aminoacylase was 7.8 and 37°C, the Zn²⁺ in low concentration activated aminoacylase.