Screening Of Probiotic Lactic Acid Bacteria From Pigs And Study On Fermentation Condition

Lactic acid bacteria (LAB) in this paper were isolated from the faeces of healthylocal pigs. Three of them were most effective in vitro antagonism of enteric pathogenicmicroorganisms. Physiological and biochemical tests besides the analysis of 16S rDNAroughly identified the three strains as Enterococcus faecium, Enterococcus faecalis andLactobacillus casei. They all can survival in the gastrointestinal tract, and bind toimmobilized mucus material in vitro. They all had antimicrobial activities against entericpathogenic bacteria such as Escherichia coli O139, E.coli C83905, E.coli C83524, E.coliC83529, Salmonella typhimurium O4Hi and Staphylococcus aureus. The isolates's safetytests were proformed by mice experiment. The faecal E.coli counts of mice of LABfeeding groups were significantly lower than the control group (P＜0.05). All the micewere challenged intraperitoneally with E.coli C83905, the deaths of the LAB used groupswere significantly less than the control group.The optimum carbon sources, nitrogen sources, buffer salts, growth factors,incubation, temperature, initial pH value, filling volume, inoculation amount of threestrains were studied by single factor test; Lastly the optimal prescription of fermentationmedium of E.faecalis was obtained by way of uniform design and regression analysis. Inthe result the density of E.faecalis in the liquid culture can reach 8.3×10~9 cfu/mL, whichwas as much as 3 times in MRS medium. The fermentation then took a alkali-fed waybased on the optimal fermentation medium, the density of E.faecalis reached 9.0×10~9cfu/mL after 18h.Different protector for E.faecalis was selected including of sucrose, L-cystein, milkwithout fat, sodium glutamine, lactose, glycerin, trehalose and chitin. Trehalose showedthe best protective effect of other protectors used alone, and the combined protector ofmilk without fat, sucrose and sorbitol showed better protective effect than trehalose. Thesurvival rate of E.faecalis was kept to 78% using this combined protector during freezedrying. All the survival rates of three strains were up to 65% stored at room temperaturefor five months.The three strains were fermented separately, 1:1:1 compounded and frozen-driedfor feeding piglets. In order to test for their efficacy including daily weight gain, totalweight gain, feed conversion and control of diarrhea, 64 piglets(Large×White×Landrace)were selected randomly and divided into LAB groups (High Dose Level, Nomal DoseLevel, Low Dose Level), antibiotic control group and control group received the samebasic feed but not supplemented. The results showed that average gain in high dose probiotic group was higher than the two control groups. As for the feed conversion ratio,the LAB nomal dose level group was better than control group, but lower than theantibiotic control group. Results also indicated that probiotic could improve feedingenvironment, decrease the diarrhea and mortality.