Screening Of A Higher-productivity α-Amylase-producing Strain And Study On It's Enzymology Properties

α-amylase is one of the most important enzymes in industry. However both of the species of a amylase and a-amylase-producing strains are lacking in our country. Although the modem biotechnology, such as translation and gene clone have already been widely applied in screening of microorganism, almost all commercial strains were meliorated from natural environment.To expand the species of a amylase and a-amylase-producing strains and find the higher-productivity a-Amylase-producing Strain, we collected some samples from Chengdu and other cities of Sichuan province.1.20 a-amylase-producing strains were screened from soil or waste water. Among these 20 strains, L-1 has the highest a-amylase activity, which is as high as 784u/mL.2 Through study the cell shape, physiological characters, Electron microscope scanning and analysis of 16S rDNA gene of L-1, we identified L-1 as B. subtilis.L-1 cell is straight bacilliform or columne and it's clony is white, roundish.With Electron microscope scanning, we found there is only one roundish spore in the centre of the cell and it's sporangium is thin.The major physiological characters of L-1 is consistant with normal B. subtilis. But it can not ultilize D- fructose and D-xylose,which is different from normal B. subtilis. To obtain accurate result, we employed 16S rDNA gene analysis.After the analysis of 16S rDNA gene, we identified L-1 as B. subtilis. We named it B. subtilis L-1.3 The optimum fermentation conditions of B. subtilis L-1 were as follows,37℃, pH5～8, the optimum carbon source is bran, nitrogen source is soybean powder4 By studying enzymology property of B. subtilis L-1, we found it's optimum reaction condition is 70℃, pH6.0～7.0. Ca²⁺ can improve the themostability of enzyme, and its effect reached maximum when Ca²⁺ was 0.02～0.04mo1/L.In conclusion, we obtained 20α-Amylase-producing Strains with higher-productivity. L-1 has the highest enzyme activity among these 20 strains. After screening of L-1, we defined L-1 as B. subtilis, and named it B. subtilis L-1. Subsequently, we optimizedthe fermentation condition of B. subtilis L-1 and studied it's enzymology property.