Screening And Microcapsulation Of Lactobacillus Acidophilus With Multi-Resistance

As one kind of probiotic bacteria,Lactobacillus acidophilus has its important function on the host for its health benefit and prophylaxis disease,and it has become a hot subject in the field of dairy science. its probiotic effects related to their survival number in the intestinal, but it is sensitive to external factors such as acid, bile salts, and antibiotics, it is hard for them to reach to the intestinal tract with sufficient viable cells,so establishment of the research projects to screening resistance strains, and preparation microcapsules of high amount of viable, then researched the characters of microcapsules.According to characteristic of the probiotics in production, choiceness mutant La4-5-2 were obtained from known strain by complex mutation.At the same time, they were identified about individual, colony and physiological and biochemical test. The tests showed that mutant were coincidental to the indentification characteristics of its species.According to the nutritional needs of Lactobacillus acidophilus Single-factor test to determine enriching effect of substances of the MRS medium,as well as enriching effects of five growth-promoting factors, and then selected four of clear enriching effects material, basis culture medium and growth promoting factors were optimized by quadratic design, The optimum culture medium composition was as following:1.5% yeast extract,1.5% beef extract, 15% tomato juice,20% cucumber juice, and determineing the best ferment conditions by Single-factor test,The optimum ferment conditions were as follows:elementary pH of ferment medium is 6.0;temperature is 37℃; inoculum concentration is 3%;liquid volume is 55ml/250ml.Growth curve was mensurated at optimum ferment medium and ferment condition. Optimum ingathering time was confirmed from the curve, which was 14 hours.Finally, cryoprotective agents was gained by experiment,which were skim milk 10%, sucrose 6%, trehalose 3%,sodium glutamate 1%, the survival rate of La4-5-2 can reach 73.45%, the number of viable cells reached 3.48 1012 cfu/g after microcapsules, the survival rate of La4-5-2 in microcapsules was determined after in a simulated gastric juice 3h,and it was still 70.11%,The tests showed that microcapsules can resistance the damage of gastric juice;and the survival rate of La4-5-2 in microcapsules can reach 61.21% after treatment with 0.3% bile salt solution for 3h. indicating microencapsulation of La4-5-2 can withstand the destruction of bile salt; After enteric determination, microencapsulated bacteria can release in 50min, indicating that this method for the preparation of microcapsules was enteric, and able to bring benefits to the human, complying microencapsules technical indicators.