Enhancement of l -amino acid oxidase production by Bacillus subtilis HLZ-68 with oxygen-vector and asymmetric degradation of dl -arginine to d -arginine

摘要

Bacillus subtilis HLZ-68 can produce l -amino acid oxidase ( l -AAO), and dl -arginine can be degraded asymmetrically by suspending the wet bacterial biomass in the degradation liquid. By adding oxygen-vectors to the fermentation medium, the collected amount of wet bacterial biomass can be increased. Taking n-dodecane, n-hexadecane, oleic acid, paraffin and n-hexane as oxygen-vectors, the optimal oxygen-vector was 1.2% ( v/v ) oleic acid. The wet weight biomass increased by 66.83% and the activity of l -AAO in the fermentation broth increased by 38.88% compared with those before the addition of oxygen-vector. The standard sample dl -arginine was derivatized by phenyl isothiocyanate, and then subjected to high-performance liquid chromatography (HPLC), and the obtained peak area and arginine content were used as standard curves to measure the dl -arginine. The content of d -arginine and l -arginine in the initial degradation solution was 50% each, and the bacterial cells were added to the initial degradation solution of dl -arginine. After 21?h of reaction, l -arginine was completely degraded, leaving 47% of d -arginine. d -alanine was easily extracted from the reaction solution using cation-exchange resin, after centrifugation, decolourization, concentration and vacuum drying, and the chemical and optical purity of the extracted d -arginine were 92.68% and 97.46%, respectively.