Mutagenesis Of Lipase Production Strain Aspergillus Oryzae WZ007 And Optimization Of The Fermentation Condition And Application

Lipases which can catalyz ester hydrolysis, ester exchange and ester synthesis reaction are important industrial enzyme. And they are widely used in oil processing, food, medicine and chemical industry. Through different microbial mutagenesis methods to improve the enzyme activity are the common methods in microbial breeding.Three kinds of different mutation methods which includes UV mutagenesis,γray induced and microwave induced mutation were used to induce Aspergillus oryzae WZ007 conserved in our laboratory. After using rhodamine B culture plate for screening and determinating the the enzyme activity as compound sieve, we got a mutation strain with high enzyme activity which named Aspergillus oryzae FS4 based on the study on the genetic stability of zhe strains. The enzyme activity of this strain reached to 21.66U/g which was 165% of the enzyme activity to the the original strain.The enzyme activity of Aspergillus oryzae FS4 was highly increased through single factor experiments and straight-cross experiments fermentation optimization. The result of batch cultivation showed that the optimal production mediums consisted of sucrose 1%,olive oil 1%(V/V),yeast extract 2%,arabia gum 0.3%,K₂HPO₄ 0.1%,MgSO₄ 0.05% and KCl 0.05%. And the best culture conditions were at initial pH 5.5 with 180rpm of shaking speed at 30℃. After optimization, the enzyme activity of the mutagenic strain reached to 37.27U/g which was 278% of the enzyme activity to the the original strain by optimization. After optimization the two kinetic models reflect the phenomenon of the cell growth and the activity of enzyme of the strain quantitatively by fermentation.Bioconversion conditions of the methyl mandelate by using lipase from A. oryzae FS4 were investigated. The optimal conversion conditions were found to be hydrolysis with substrate concentration of 0.02 mol/L in pH 6.0 phosphate buffer solution at 30℃with shaking speed of 200rpm. In the process conditions, the conversion rate of methyl mandelate was 78.43%, with an enantiomeric excess of 71.46% in a reaction time of 20 h. The E was 2.8.