Characterization and Optimization of Amylase Production in Strains LZ-10 and LZ-11 Belonging to Bacillus subtilis

In order to obtain pure enzyme with high activity,two amylase producing strains were isolated from soil samples,and named as the strains LZ-10 and LZ-11.According to morphologic observation,physiology and biochemistry experiments,16S rRNA and gyrB gene analysis,the strains LZ-10 and LZ-11 were identified as Bacillus subtilis.Adopted the method of ammonium sulfate,DEAE-52 anion purify enzyme,finally used polyacrylamide gel electrophoresis （SDS-PAGE） to detect molecular weight.The strain LZ-10 had an amylase activity of 123.3 U·mL^-1,a purification factor of 6.8,a recovery rate of 69.5% and an optimal temperature of 50℃.The amylase activity of the strain LZ-11 was 59.91 U·mL^-1,the purification factor was 4.5,the recovery rate was 60.5%,and the optimum temperature was 55℃.The commodity enzyme derived from Bacillus subtilis was 37.5 U·mL^-1.The relative molecular weight of amylase activity from the two strains was 55 ku.Both thermal stability and pH stability were higher than those of commercialized amylase.