Study On Conditions Optimization Of Producing Proteases By Micrococcus And Fermentation Technology Of Fermented Bean Curd In The Bottle

Protease activity of micrococcus was researched systematically in the paper. Micrococcus was treated by UV induced mutation,screening a bacterial strain that produced a large number of proteases,and discussing the cultivate compositions and condition of producing proteases. Protease enzyme properties were studied including the optimum reaction temperature,the stability,the optimal pH and metal ions. The changes of chemical composition and enzyme activity were analyzed during the production of KeDong Fermented Soybean Curds, which provided theory standard for the research on fermented bean curd in the bottle. Reasonable ratio of fermented bean curd soup and protease fermented liquid content were confirmed,getting the basic process parameters. The results are as follows:Screening a bacterial strain that produced a large number of proteases by UV induced mutation, and the protease activity is1.54times than that of the starting strain. Through single factor and orthogonal experiments, the results show that sucrose is the optimum carbon source, peptone is the optimal nitrogen source.Soybean milk is beneficial as nitrogen source,and the enzyme activity is higher.According to the actual production needs,using soybean milk is appropriate. KH2PO4, ZnCl2, NaCl has promoting effects in different degrees on strain producing protease, and the influence of MgSO4and CaCl2was not significant. The best fermentation conditions of micrococcus producing protease were determined:sucrose content1.0%;soybean milk content8.0%;NaCl0.4%;KH2PO40.06%;ZnCl20.08%;bacterial load6%;pH value7.5;culture temperature35℃; culture time36h.The results of protease enzyme properties are as follows:the optimal pH value is8.0;because alkaline protease is its advantage protease in the crude enzyme fluid; the optimal temperature is50℃; the stability of the enzyme is good. Zn2+and Na+have promoting effects on enzyme activity;Ca2+,Fe2+and Fe3+have inhibition effects in different degrees.The changes of chemical Composition and enzyme activity were analyzed during the production of KeDong Fermented Soybean Curds. Crude protein of sofu pieces showed a declining trend meaningfully; Crude protein of the sofu soup showed a increasing trend significantly; free amino acid nitrogen and total acid of sofu continued to increase significantly; pH of the sofu showed a declining trend significantly; crude fat content of sofu pieces showed a declining trend significantly; free fatty acid content is increasing; reducing sugar continued to increase:salt content remained stabilization.The enzyme activity of alkaline and neutral protease and glutaminase were increasing gradually in the pre-fermentation process. Alkaline protease activity is on the decline.and neutral protease and glutaminase were increasing during the later fermentation process Reasonable ratio of bottling fermented bean curd soup:Salt8%, wine4%, sugar10%, Red yeast rice2%, flour yeast6%, spices0.3%;the fermentation time is60d, protease fermented liquid content is30ml. The basic process parameters of fermented bean curd in the bottle were getted, providing certain theoretical basis for the development of fermented bean curd industry.