Study On The Screening And Fermentation Basic Condition Of Acid-resistant α-amylase Producing Strain

Lees was used for screening wild strain which secreted acid-resistantα-amylase, the mutational character of the strain and the acid-resistant a-amylase fermentation in shaking flask and 10L ventilating fermenter were studied, respectively. The main result as follows:The objective strain was selected by trypan-blue method, it produced acid resistant a-amylase and its activity of enzyme was 63.4 U/g, named strain AS-Y. After UV+EMS treatment, the activity of enzyme got to 198.8 U/g, and the optimal mutational time was 2 min for UV and 50 min for EMS, the strain had great stabilization in heredity.The effects of content of culture medium, temperature, pH value, the containing water amount, inoculation volume on solid-state fermentation were investigated by using determining the enzyme amount.The optimal conditions for fermentation also determined through single factor and orthogonal test.The results showed the optimum conditions were bran 15 g, ammonium sulfate 1.025 g, inoculation volume 4 mL, initial containing water 50%, calcium chloride 0.03 g, pH value normal and temperature 30～32℃.Its activity of enzyme increased a lot, reaching 286.3 U/g. According to above, we stopped the solid-state fermentation during 60～72 h.The effects of all kinds of conditions on liquid-state fermentation were researched through single factor and orthogonal experiment.the optimal results were starch 1.5%, peptone and ammonium sulfate 3.2%, inoculation volume 10%, calcium chloride 0.2%, pH value 4.0～4.2, temperature 28～30℃and its fermentation time is 72 h. The strain secreted acid-resistant a-amylase production was 6.4 U/mL.We studied the enlarged liquid fermentation using 10L ventilating fermenter and established its model, including growth dynamics model,production dynamics model and substrate consuming dynamics model. The results showed that these model were growth dynamics model dX/dt=0.1358(1-X/9.1684)X,production dynamics model dP/dt=0.1027dX/dt+0.0255X and substrate consuming dynamics model -ds/dt=0.3815dx/dt+0.4239dP/dt.According to the linear fitting which was above 95%, the liquid-state fermentation parameter could be well described through the three fermentation dynamics model.As discussed above, the enzyme activity of the objective strain which was screened by mutation treatment much higher than the wild strain. So it could be wildly put into service in the fields of alcohol, food, feedstuff, medicine and so on.