High-Cell Density Cultivation Of LAB By Membrane Filtration Methodology And Screening Antagonistic Strains From Pickling Vegetable

High cell density culture and cells enriching concentration are important links of lactic acid bacteria starter prepares, It’s very important to research and develop high activity concentrated starter culture for promoting the industrial process of lactic acid bacteria starter and development of pickles industry. In this paper, isolation of lactic acid bacteria from pickles、high cell density culture and cells enriching concentration are studied.(1) Seven strains of lactic acid bacteria were isolated and identified from many sorts of pickles. Their physiological, biochemical properties and 16S rRNA gene sequence were characterized. Based on their physiological and biochemical properties, homology and phylogenetic analysis of 16S rRNA gene sequence,7strains were Lactobacillus plantarum.(2) These strains were further characterized for the presence of functional traits useful for probiotic applications,such as resistance to acid and resistance to bile salts.S-2、D-1 and D-3 showed survival rates ranging from 100% to 135%,and expressed acid tolerance at pH 1.5 after 4 h incubation and the living bacteria number reached 8.4x108cfu/mk 8.3x108cfu/ml and 8.1x108 cfu/ml, respectively. Similarly, these bacteria expressed tolerance to bile salts at the concentration of 0.3%, after 4h incubation and the living bacteria number reached 8.5×108 cfu/ml、8.9×108 cfu/ml、8.4×108 cfu/ml.(3) Constant pH value cultivations were performed by using 30 L fermentor. According to uniform designed experiment, the optimal cultivation conditions for L.p found to be wort as culture medium,7% seed volume, with constant pH value at 6.5 and culture temperature of 36℃, cultivation is divided three times,the time are 15,6 and 6 hours,60% feeding cultur ratio. The final cell population get to 4.03×1010 cfu/ml(4) Flux as index,we study the concentration of hollow fiber,the optimal concentration conditions for L.p found to be pressure is 50r/min,the time is 30 min. The final cell population get to 7.48×1010cfu/ml. (5) The storage of high cell density culture is studied. At this storage conditon for thirty days, the survival rate was 50% as well as with the viable cells concentration of 3.79×1010cfu/ml similarly,the survival rate of freeze-dried 90%,which had the the viable cells concentration of 3.12×1011cfu/g.