Screening And Preparation Technology For High-active Microbial Starter Of Bacillus Coagulans

Lactic acid bacteria are a kind of probiotics that can improve the health level of the host and improve the flavor of the fermented products.They have a great scale of application in the market of functional foods,fermented feeds and medical and health products.However,the activities of traditional lactic acid bacteria such as Bifidobacterium and Lactobacillus casei decrease due to environmental changes in the production,transportation and preservation process,so that the use effect of the products is affected.Therefore,it’s urgent to seek edible alternative strains and improve the activity of related preparations.Bacillus coagulans,as the new spore-producing lactic acid bacteria,not only has the probiotic effect of traditional lactic acid bacteria,but also has high resistance to environmental changes.In recent years,Bacillus coagulans has attracted the attention of food and other industries.However,most studies only focus on its biological characteristics and the number of viable bacteria,and there are still insufficient studies on improving its spore production and the preparation technology of highly active agents.In this study,22strains of Bacillus coagulans were isolated from the feces of Luhua Chicken,and the Bacillus coagulans NCUBCG014 with the best comprehensive performance was screened out through the test of probiotic properties and spore yield.The key parameters such as medium composition,culture control conditions,protective agent composition and spray drying process were optimized by single factor,orthogonal and response surface center combination methods to prepare the Bacillus coagulans living preparation with high activity.This study will provide a theoretical basis for the industrial application of Bacillus coagulans and is of great significance to the research and application of Bacillus coagulans.The main research results of this paper are as follows:1)Screening and identification of Bacillus coagulans:104 potential target strains with acid-producing ability were preliminarily screened from 300 feces of Luhua chicken by high temperature pretreatment,and 22 strains of Bacillus coagulans were screened out according to morphological characteristics,physiological and biochemical experiments and molecular biology identification.2)Probiotic performance evaluation and spore production ability test of Bacillus coagulans:Through high temperature and simulated gastrointestinal tolerance experiments,combined with various tests such as acid production ability,cholesterol degradation ability,antioxidant ability,protease production ability and amylase ability,three Bacillus coagulans with excellent performance were screened out,which were NCUBCG003,NCUBCG004 and NCUBCG014,respectively.Among them,the spore formation ability of NCUBCG014 under conventional culture conditions was significantly higher than that of other strains.NCUBCG014 was selected for further study after synthesis.3)High-density culture technology of Bacillus coagulans NCUBCG014:Based on LB medium,through single factor experiment,orthogonal experiment and response surface central composite experiment,the optimal medium components for Bacillus coagulans NCUBCG014 spore growth were determined as follows:soybean meal 1.74%,sodium chloride 1%,manganese sulfate 0.06%,and the highest number of spores was 2.77×10⁸ CFU/mL.According to the single factor experiment,the culture conditions and the process parameters in the fermentation tank were optimized.The optimal culture conditions were as follows:inoculum 5%,culture temperature 43℃,initial pH 6.5,and the corresponding spore number was 3.0×10⁸CFU/mL.The optimal fermentation tank culture control parameters were as follows:rotation speed of 150 rpm,aeration rate of 75 NI/h,and constant pH value of 6.5.The final spore number could reach 4.46×10⁸ CFU/mL,which was 33.83 times that of LB medium under conventional culture conditions.4)Preparation technology of Bacillus coagulans NCUBCG014:Bacillus coagulans NCUBCG014 was prepared by spray drying technology.The survival rate,powder collection rate and moisture content were used as indicators.The optimal protective agent was 1%soy protein isolate and 0.1%lactose through single factor experiment and response surface central composite experiment.The optimal process parameters were inlet air temperature of 135.33℃,feed rate of 483.11 mL/h,and gas flow rate of 407.25 L/h.The number of viable Bacillus coagulans in the final optimized bacterial agent reached 1.68×10¹¹ CFU/g.