混合菌群发酵秸秆合成菌体蛋白及其动力学分析

混合菌群发酵秸秆可有效提高秸秆纤维的降解率及菌体蛋白的转化率,对拓广蛋白饲料来源、减少环境污染起到积极的作用。本研究以小麦秸秆为原料,在纤维素酶水解预处理的基础上,以米曲霉作为先导菌,进一步分解残留的粗纤维,为后期发酵提供充足的碳源。根据不同微生物的代谢特征和协同机理,试验确定了发酵阶段混合菌群的组成为:米曲霉、产朊假丝酵母和枯草芽胞杆菌;接种顺序为:先接种米曲霉,再接种产朊假丝酵母,最后接种枯草芽胞杆菌。正交试验表明,影响发酵主要因素的主次顺序为:秸秆与麸皮配比>接种比例>发酵时间>接种量>发酵温度;发酵的最适条件为:米曲霉的接种量2.5%,发酵12h后接入5%的产朊假丝酵母,继续发酵8h后接入2.5%的枯草芽胞杆菌,发酵温度为28℃,秸秆与麸皮的配比为4∶1,尿素添加量为1.2%;结合动力学分析,将混合菌群的发酵时间优化为35h,发酵产物中粗蛋白含量由原来的5.47%提高到25%左右。对最适发酵条件下的动力学过程进行了探讨,建立了以Logistic方程为基础的数学模型和动力学方程。本研究表明,混合菌群发酵秸秆提高了发酵产物中的粗蛋白含量。动力学分析对于了解发酵机理、掌握整个发酵过程中混合菌群生长的动态变化、优化发酵工艺具有重要的指导意义。

Synthesis and dynamics analysis of mycoprotein by fermentation of straw using mixed microbes

Fermentation of straw using mixed microbes can improve the degradation rate of straw and increase the conversion rate of mycoprotein,which could help broadening the sources of protein feed and alleviating the environment pollution.The raw material,wheat straw,was pretreated via method of cellulose enzyme hydrolysis.Residue of crude fibre was decomposed firstly by Aspergillus oryzae to provide sufficient carbon source and energy for the next process.According to metabolic characteristics and coordination mechanisms of different microbial systems,the composition of mixed microbial flora at the fermentation stage was determined,including Aspergillus oryzae,Candida utilis and Bacillus subtilis.Orthogonal experiments were conducted to analyze and optimize the influence factors,which showed that the order of main influencing factors of the fermentation was ratio of straw and bran＞inoculation ratio＞fermentation time＞fermentation temperature.Detailed optimal fermentation conditions were as the following:the inoculation amount ofA.oryzae at 2.5％;after 12h fermentation,5％ C.utilis was inoculated and 2.5％ B.subtilis was inoculated 8 h later at fermentation temperature of 28 ℃;the ratio of wheat straw powder and bran was 4 ∶1 and the amount of urea was 1.2％.Furthermore,dynamic study showed that the optimized fermentation time was 35 h,and the protein content increased from 5.47％ to 25％.On the basis of Logistic equation,dynamic model and kinetic equation were established for optimum fermentation conditions.The results revealed that the fermentation of straw using mixed microbes improved the protein content,and dynamics analysis played a dominant role in analyzing the fermentation mechanism,dynamic changes and optimizing fermentation.