| HSAA(short for Thermostableα-Amylase),one of the most important enzyme productions in China, is a kind of endo-hydrolases accumulated by Bacilus Licheniformis,which is widely used in foodstuff & fermentation industry and textile industy.The production and export quality has increasaing steadily for six years in China,while the cost getting higher and the profit getting poor. In addition,its production of China BBCA Group can meet for only 50% of annual requirement,therefore,Researching and developing new technology of impoving it's activity not only can contribute to the development of the industy but also fill the output gap of China BBCA Group.This thesis described the methods of selecting a high yield strain through adopting mutagenesis together with protolast fusion technology.It is indicated by the experiments that a high yield strain can be selected out by using protoplast preparation and mutagenic treatment with 100μg/ml N-methyl-N'-nitrosoguanidine(NTG). Fermention conditions can be optimized through purposeful experiments in shaking flask,pilot-scale fermentor,large-scale fermentor. The optimum conditions for pilot–scale fermention were indentified as follows through above experimentes: white dextrin 12%,(NH4)2SO4 0.5%,bean cake 2%,Glu1%,phosphate (K2HPO4)0.8%, DE20-30,initial pH 6.0-6.5. Part of optimum conditions for large–scale fermention were as follows :corn starch 24%, bean cake 2%,corn soak 1.5%, phosphate (K2HPO4)0.8%, DE 30.Results showed that:The performance of strain selected is superior and its property is stable. 4100u/ml of HASS was accumulated in shaking flask more than 45% compared with the origin. 14900u/ml of thermostableα-Amylase was accumulated in 50litres full automatic pot more than 16% compared with the orignal and 12000 u/ml of HASS was accumulated in 50M3 fermentor more than 31% compared with the orignal,so 30% of cost of production have been saved. The activity has been improved to 12000 u/ml,which is higher than other inrernal reports .
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