Screening Of Thermotolerant Lactic Acid Bacteria And Application

In the experiment, lactic acid bacteria with high thermotolerance were isolated from silage,apple pomace,milk and fresh pickles. Then the strain L1 with thermotolerance and producing more lactic acid was isolated through the primary and secondary screening .Through repeating He-Ne laser-induced breeding the strain TL1 with high thermotolerace and producing more lactic acid was screened. The number of the strain TL1 of improved 12 times than the number of the strain L1 in 70℃.The number of bacteria was 1.275×10~9u/ml. It had stable heredity.According to the criteria and description of Bergey 's manual of systematic bacteriology and classification and identification of LAB, the strain L1 was classified as the genus lactobacillus and the species Lactobacillus delbbruecki on the basis of morphological observation and physiological and biochemical tests.Through the single factor experiments and orthogonal test, the optimal cultural conditions of the strain TL1 was as follows: final pH being 3.5, culture temperature being 60℃and culture time being 24h at the enzymolysis ofα-amylase (90, 30min, 5u/g corn) and saccharifying enzyme(55℃, 2-3h, 150u/g). the optimal composition of culture medium was 16% corn flour + 5% bran.The changes of pH and bacterial population during the fermention were measured, and found that spoilage bacteria decreased fast and were zero in the end after adding into LAB. Sensory assessment and comprehensive assessment of organic acid were showed the quality of silage treated with LAB was better than the control. The results of chemical analysis indicated the content of water, crude protein, Ca, P, Ammonia-N, dry matter, acid, propionic acid, WSC, sum of bacteria of all silages treated with LAB increased significantly in contrast to control. In comparison to the control, the content of propionic acid and lactic acid increased 162% and 21.16% respectively. The content of NDF, ADF, detergent ligmin ,butyric acid decreased obviously in contrast to control .The content of detergent Ammonia-N ,ligmin and ADF decreased 36.4%,3 1.75% and 31.2% respectively.The feed trial proved that corn silage treated with the strain TL1 compared to corn silage untreated could increase the milk yiled, and the milk yiled could increased 1 kg everyday . Production raised remarkably. All of the above, corn ensilaging with the contribution of the strain TL1 could not only reduce the moldy rate, increase the taste of the silage, improve the quality of the silage but also raise the milk yiled.In the composting process pH decreased remarkably with the strain TL1. The volatile solid content decreased 50%;Seed germination percentage improved 4%. All of the above, rhe results showed: the strain TL1 could accelerate the decomposable velocity of organic matter; improve the compost quality and Seed germination percentage of the wheat.