Screening Mucor Of High-yielding Protease And Fermentation Technology Research On Direct Fermented Bean Curd

Fermented bean curd is a traditional fermented soybean products with national characteristics in our country, has a special status in the world. There are varieties of microbes and enzymes involved in the production process of fermented bean curd and they work together to create the unique flavor of fermented bean curd, and some special nutrition health care function. Actinomucor elegans and Wutungkiao Mucor were used as experimental materials and the optimization of fermentation medium and culture conditions were studied. The fermented strains of high activity protease were got by UV mutagenesis screening strains to shorten the fermented bean curd fermentation period. The research results was helpful to solve the problem that the fermented bean curd production was restricted by season, to improve the production efficiency of fermented bean curd and to meet the market demand.1. The results of the fermentation medium and culture conditions optimization of two kinds mould to creat neutral protease by single factor test and orthogonal test were as follows:(1) The results showed that the optimal fermentation medium composition for neutral protease of Actinomucor elegans was:sucrose content10.0%, soybean flour3.0%, KH2PO40.40%, CaCl20.09%, the neutral protease activity was1335.32U/mL; The optimal condition of culture for production neutral protease of Actinomucor elegans was:incubation time was3d, incubation temperature was30℃, pH6.5and the amount of mucor inoculated spores was10.0%, the neutral protease activity was1978.32U/mL; The improve percentage of neutral protease activity is133.22percent.(2) The optimal fermentation medium composition for neutral protease of Wutungkiao Mucor was:sucrose content10.0%, soybean flour3.0%, KH2PO40.35%, CaCl20.08%, the last neutral protease activity was1328.13U/mL. the optimal condition of culture for production neutral protease of Wutungkiao Mucor was:culture temperature was26℃, incubation time was3.0d, pH6.5, the amount of mucor inoculated spores was8.0%, the last neutral protease activity was1908.53U/mL. The improve percentage of neutral protease activity is131.68percent.2. This article adopted UV mutagenesis method. The optimal mutation condition for neutral protease of Actinomucor elegans was:150seconds. Under the mutagenic dose, the two better strainswere got, named UV-8and UV-29and the improve percentage of neutral protease activity of them were27.00and25.16percent respectively. The optimal mutation condition for neutral protease of Wutungkiao Mucor was:140seconds. Under the mutagenic dose, a better strains was got, named UV-17and the improve percentage of neutral protease activity was37.35percent. UV-17had better genetic stability.3. This chapter mainly studied the impact factors for enzyme activity of the mucor UV-17: (1) The optimal temperature was45℃, fine thermal stability for the range of temperature40℃-50℃.(2) Fine range of pH6.5-7.5, the range of protease can keep high activity.(3) Fine range of ethanol within20.0%, under the low environment, protease activity is stability.(4) Fine range of salt within9.0%, under the low environment, protease activity almost not be affected.(5) The metal ions influence on protease activity, Na+、K+、Ca+for protease; While Zn2+、Fe2+showed to inhibit the action of the enzyme activity.4. The best process parameters for the binders of high-yielding protease was:the rice saccharification liquid amount was25.0%, soya-bean milk content was10.0%, salt content was7%. Direct fermentation parameters of fermented bean curd were identified that the protease fluid amount was30.0mL. Wutungkiao Mucor UV-17was used in fermented bean curd process. The fermented bean curd needed60d to reach maturity level. Compared with the traditional fermented bean curd, fermentation period of direct fermentation was shortened about50%.