| Lactobacillus as one of probiotics can effectively inhibit the growth of harmful bacteria such as Escherichia coli and Staphylococcus aureus,and it can also effectively inhibit the normal growth of harmful fungi such as Fusarium and Aspergillus.Therefore,it can be used as a substitute for antibiotics in animal husbandry.It is widely used in the industry.At the same time,Lactobacillus are also widely used in feed and food industries because they are rich in organic acids,bacteriocins,short-chain fatty acids and protein macromolecules and other substances,and have rich nutritional value.Lactobacillus can effectively improve the nutritional value of food and feed or the body’s disease resistance,balance the intestinal environment,and promote growth or development.Therefore,in this experiment,fermented products were used as raw materials to screen lactic acid bacteria with good acid-producing effects,to explore whether they could successfully reach colonization in the intestines through the action of gastric acid,and to explore their effects as a fermentation inoculant on feed nutrition.In this experiment,8 strains of Lactobacillus of different species were screened from different fermentation products（Lactobacillus antarctica BC1,Lactobacillus Heilongjiang BC5,Lactobacillus pentosus BP1,Lactobacillus plantarum DB1,Enterococcus faecalis DB3,Lactobacillus thermophilus RF2,Lactobacillus acidophilus RF3,Lactobacillus rhamnosus SN）.Existing lactic acid bacteria in the laboratory（Lactobacillus plantarum NJ,Lactobacillus paracasei G1,Lactobacillus curvy G2）.The acid production of 11 strains of lactobacillus was preliminarily determined,and 4 strains of lactobacillus with good acid production effect were obtained:BC1,BP1,NJ and SN.The acid tolerance test of the lactobacillus found that the survival rate of the live bacteria of the 4 strains of lactobacillus was about 95%when they were exposed to pH 2.5 for 2 hours,and the survival rate of the 4 strains of live lactobacillus was more than 90%after the treatment for 4 hours.After 4 strains of lactobacillus were exposed to pH 1.5 for 2 hours,the survival rate of BC1 strain was about 10%,the survival rate of BP1 strain was about 25%,and the survival rate of NJ and SN strains was about 40%.The survival rate of the NJ strain was about 10%and the survival rate of the SN strain was about 20%after acting at pH 1.5for 4 hours.As pig gastric acid fluctuates in the range of pH 2-3,and the gastric emptying time is about 2-3 hours,lactobacillus can smoothly pass through the stomach to reach the inner surface of the intestine.The lactobacillus were tested for bile salt tolerance and found that when the bile salt concentration was 0.1%,the OD600 of the BC1,BP1,and NJ strains was 2.2 after 72 hours of culture,and the OD600 of the SN strain was 1.3.When the bile salt concentration is 0.2%,the OD600 of the BC1,BP1,and NJ strains is 0.6 after 72 hours of culture,and the OD600 of the SN strain is 0.2.When the bile salt concentration is 0.3%,the OD600 of BP1 strain is 0.6 after 72 hours of culture,the OD600of BC1 strain and NJ strain is0.3,and the OD600 of SN strain is 0.2.Because the fluctuation range of bile salt in animal intestines is between 0-0.3%,as the concentration of bile salt increases,the growth of lactic acid bacteria becomes slower.At high bile salt concentration,the 4 strains of lactic acid bacteria still have a certain growth ability,so all of them Can be colonized in the intestine.Based on the results of the preliminary screening of lactobacillus,the composite fermentation inoculum was screened and obtained:Lactobacillus plantarum,Lactobacillus pentosus,Lactobacillus campylobacter,Lactobacillus rhamnosus and auxiliary bacteria yeast,Bacillus subtilis.The ratio of lactobacillus and auxiliary bacteria is 3:1:1.In the preliminary application of the compound fermentation inoculants,the crude protein of the feed for 3,6,and 9 days of fermentation increased by 13.49%,20.03%,and 24.84%compared with the raw materials,and the acid-soluble protein increased by 36.33%,44.73%,66.71%compared with the raw materials.Compared with the raw materials,the crude protein of the feed for 3,6,and 9 days of bacterial fermentation in the factory increased by 14.71%,15.49%,and17.85%,and the acid-soluble protein increased by 24.71%,36.76%,and 47.27%compared with the raw materials.In this experiment,lactic acid bacteria with different functions were obtained by screening different materials.The screening of compound microbial agents for feed fermentation resulted in a combination of compound microbial preparations with preliminary application value.The results of this experiment have certain technical parameter support for the feed industry. |
