Analysis Of Microfora Composition For Keiir Grains And Preparation Of Lactobacillus Plantarum Starter

This paper mainly studied the microfora composition and distribution in Tibet Kefir grains by PCR-DGGE technique. And the changes of microfora composition during the fermentation of Kefir were dynamically monitored. Molecular biology techniques and the isolation and identification of traditional Kefir at earlier of our lab were utilized to analysis dynamic changes of Lactobacillus plantarum MA2 during fermentation. The cholesterol-lowering effect of MA2 was studied. And optimized the conditions of spray dying and protectants used in spray dying, then probiotic starter was prepared by spray dying. The main results were as follows:There were 9 types of bacterium and 4 types of fungi in Kefir grains in the advantage position by the PCR-DGGE analysis. During the fermentation of Kefir, bacterium composition and distribution was change significantly, and from 12 h to 16 h, bacterium species and population reached the maximum value, bacterium species has reached 9, in which 3 species has accompanied the whole fermentation. Similarity of bacterium population structure was 70%-83%; in comparison, fungi were stable during fermentation. There were 3 types of fungi in the advantage position and similarity of fungi population structure was 80%-87%.The DGGE electrophoresis of MA2 revealed that, it was in the advantage position during fermentation. The cholesterol-lowering effect of MA2 was studied in this experiment. The results depicted that the manner of cholesterol removal corresponded to the manner of cell density. When cholesterol concentration reached 30 mg/100mL in the MRS-CHOL, the percentage of cholesterol removed was 46.8%.The protectants used in spray dying were optimized by Orthogonal Test. and the optimum properties of protectants were as follows:sodium glutamate 2%, trehalose 5%, and skim milk 10%. The conditions of spray dying were optimized by response surface analysis, and the best conditions were as follows:inlet air temperature was 152?. inner-speed of mixture was 62 mL/h, and proportion of protectant to cell was 3.4:1. Bacterium powder has prepared by spray dying. And its living bacteria amount is 2.11× 109cfu/g, the time of milk-solidfying was 12 h, and the percentage of cholesterol removed was 40.6%. After cold storage at 4? for six months, the living bacteria amount of Bacterium powder is 1.02×10 cfu/g, the time of milk-solidfying was 14 h, and the percentage of cholesterol removed was 32.0%. The spray dying starter cost only 65% that freeze dying need. So spray dying is more suitable for large scale production.