豆粕的坚强芽孢杆菌(Bacillus firmus)发酵工艺优化及其营养成分分析

摘要

坚强芽孢杆菌(Bacillus firmus) PC024是一株分离自中国明对虾(Fenneropenaeus chinensis)养殖环境,且能够提高对虾免疫力和抗病力的益生菌.本研究优化其发酵豆粕的工艺条件,单因素优化结果:最佳接种量为2× 106 CFU/g,最佳料水比为1∶0.8,最佳发酵时间为90 h,最佳发酵温度为37℃.在单因素实验结果的基础上,采用响应面法对4个因素进行了优化,最终确定最佳发酵条件:发酵温度为39.0℃,发酵时间为100 h 18 min,料水比为1∶0.96,接种量为3.84× 106 CFU/g.经此条件发酵后,发酵产物中的菌浓度可达1.23×1010 CFU/g,验证值与预测值相差5.13％,优化模型可靠.豆粕经发酵后发生感官变化,豆粕发酵的得率为(93.89±0.01)％,可溶性蛋白含量由发酵前的(39.16±0.01)％增加到(58.80±4.54)％,豆粕粗蛋白质由发酵前的50.71％增加到55.03％,15种氨基酸的总含量增加到原来的132.30％,增加比例最大的5种为精氨酸(168.60％)、赖氨酸(157.20％)、丝氨酸(152.50％)、苏氨酸(139.04％)和甘氨酸(138.40％).经SDS-PAGE显示,蛋白大分子得到有效降解.本研究可为益生菌的利用和对虾疾病防控提供新思路.%Bacillusfirmus strain PC024,isolated from Chinese shrimp (Fenneropenaeus chinensis) rearing environment,has demonstrated its ability to increase shrimp resistance to white spot syndrome virus (WSSV) infection and to ferment dietary soybean meal.The purpose of this current study is to optimize the processing conditions for the fermentation of soybean meal using B.firmus.Considering single factor trials,results indicated that the optimum bacterial concentration for inoculation,water ratio,fermentation time and temperature were 2× 106 CFU/g,1∶0.8,90 h,and 37℃,respectively.However,on the basis of univariate tests,the response surface methodology (RSM) was applied to optimize four fermentation factors when they were combined,including temperature,time,water ratio,and amount of bacteria required for inoculation.The optimum fermentation conditions were as follow:fermentation temperature,39.0℃;fermentation time,100 h 18 min;water ratio,1∶0.96;and amount of bacteria for inoculation,3.84×106 CFU/g.Under the optimized conditions,the bacterial concentration reached 1.23× 1010 CFU/g after fermentation and it was 5.13％ deviated from the predicted value using the RSM model.The quality of soybean meal improved significantly after fermentation.Firstly,the yield of the fermented soybean meal reached (93.89±0.01)％.Secondly,after fermentation,the soluble protein content in the soybean meal increased from (39.16±0.01)％ to (58.80±4.54)％,and crude protein content in the soybean meal increased from 50.71％ to 55.03％.Finally,the total amount of amino acids (15 types) had 132.30％ increase compared to the original content;the most significant increases in the proportion amino acids were arginine (168.60％),lysine (157.20％),serine (152.50％),threonine (139.04％) and glycine (138.40％).It showed that the protein molecules were effectively degraded in SDS-PAGE.This study provides theoretical support for the application of probiotics in shrimp plant-basis diet and disease control in aquatic animals.