Isolation And Identification Of Super Lactic Acid Bacteria And Study On The Preparation Technology Of Complex Probotics Product

Lactic acid bacteria were isolated from corn silage contains and 17 single colonies were selected for further training. The strains identification of selected bacteria was performed with the surface morphology, physiological and biochemical tests, 16 s r RNA gene sequencing analysis and phylogenetic trees. Excellent trait strains were screened out by measuring the acid production rate and growth rate.The the tolerance ability of eight lactic acid bacteria was studied, which affirmed three strains as the primary fermentative species. Taking p H value and living cell count as indexes in the process of fermentation,the experiment had studied the best strain ratios.The single-factor-experiment and orthogonal experiment were used to determine the best fermentation condition. Lactic acid bacteria powder preparation was obtained by freeze-drying.(1) 17 lactic acid bacteria were isolated and purified from natural silage. The results indicated that eight strains were Lactobacillus plantarum(3, 5, 6, 8, 11, 13, 15, 16); three strains were Lactobacillus zeae(1, 4, 10); three strains were Pediococcus acidilactici(7, 4, 17); the other three are Lactobacillus farciminis, Lactobacillus casei and Lactobacillus paracasei(2, 9, 12). Through measuring the rate of lactic acid production and the growth curve, strain 3, 5, 6, 7, 9, 11, 15, 16 were selected as eximious strain due to its rapid acid-production and growth speed.(2) Strain 3, 7, 9 were inhibitory to Escherichia coli, Salmonella and Staphyloccocus aureus Rosenbach. And they also show good resistance to low p H and bile salt. Three strains(3,7 and 9) showed good mutual fermentation character and when the ratio of the three strains’ amount was 3:2:1,acid content and living cell count were higher than other strain ratio.(3) The optional environmental condition is as following: temperature 37℃, initial pH7.0 and inoculation amount 3%. And the optimal nutritional condition is as following: lactose 30g/L, soy peptides powder-whey power(1:1)40g/L, sodium acetate7g/L, tween-80 4mL/L, magnesium sulfate 0.5g/L, manganese 0.25g/L. Under the above condition, the biomass could reach to 5.51×109cfu/m L, 3.7 times more than the original medium, meanwhile the screened source reduce the cost of media.(4) Compound lactic acid bacteria powder produced by freeze-drying display good physical characteristics and survival of lactic acid bacteria is 80.62%, it was demonstrated freeze-drying is efficient processing produce compound lactic acid bacteria powder.