酸奶中传统发酵乳酸菌的分离筛选及增菌研究

Study on the Isolation,Screening and Promoting Bacteria of the Traditional Fermenting Lactic Acid Bacteria from Yoghourt

[目的]分离筛选传统发酵乳酸菌,选择最适增菌物质。[方法]以市售酸奶为试材,采用稀释涂布法和平板划线法分离纯化保加利亚乳杆菌(Lactobacillus bulgaricus)和嗜热链球菌(Streptococus thermophilus),分别采用4种培养基分离,通过菌落观察、镜检和理化特性测定,筛选优良菌株。在最适分离液态培养基中添加6种物质对菌株进行增菌培养,每隔8 h测定菌液OD值。[结果]L.bulgaricus和Str.thermophilus在改良培养基上生长良好,测定理化特性筛选出发酵性能优良的2株L.bulgaricus(L.b.2、L.b.3)和1株Str.thermophilus(S.t.3)。增菌结果显示5种天然营养物均不同程度地促进了L.bulgaricus和Str.thermophilus的生长。[结论]改良MRS培养基和改良M17培养基分别为L.bulgaricus和Str.thermophilus的最佳分离培养基;10%黄豆芽汁和12%胡萝卜汁是L.bulgaricus的最佳增菌物质。

[Objective]The research aimed to isolate and screen out the traditional fermenting lactic acid bacteria and select the optimum bacteria-prometing materials. [Method]Taking the yoghourt on sale as the tested materials, L. bulgaria＇us and Str. thermophilus were isolated and purified by using the diluted and streaked plate method. L. bulgaricus and Str. Thermophilus were isolated by using 4 kinds of media. Through the colony observation, microscopic examination and the detennination of physiological and biochemical characteristics, better strains were isolated and screened out. The purposive strains were propagated in culture medium of adding six nutritive materials and OD value in the bacteria liquid wa,s measured by every, eight hours. [ Result] L. bulgaricus and Str. thermophilus could grow well in the improved medium. 2he physiological and biochemical characteristics were deter mined. Two strains of L. bulgaricus, strains （ L. b. 2, L. b. 3 ） and one better Str. therrnophilus strain （ S. t. 3 ） with good tennentation performance were screened out. The bacteria-promoting results showed that 5 kinds of natural nutrients could promote the growth of L. bulgarieus, and Str. thermophilus to different extent. [Conelusion]The improved MRS meditan and the improved M17 medium were the optimum isolation medianl of L. bulgaricus, and Str. thermophilus respectively. 10% scybean sprout juice and 12% carrot juice were the best materials which could promete the grovel of L. bulgaricus.