嗜热链球菌与保加利亚乳杆菌麦芽复合汁增菌培养基的优化筛选

Screening and Optimizing of Lactobacillus bulgaricus and Streptococcus thermophilus Wort Enrichment Medium

研究了在麦芽汁中添加不同的营养因子对嗜热链球菌S.t-3的细胞生长量的影响,进一步采用正交试验优化筛选出S.t-3的麦芽复合汁增菌培养基,并对保加利亚乳杆菌L.b-DR和L.b-S1进行了验证性增菌试验。结果表明,S.t-3、L.b-DR和L.b-S1在麦芽汁中能进行正常的产酸代谢,大豆蛋白胨、牛肉膏、酵母膏可显著促进S.t-3的细胞生长(P<0.05);K2HPO4不仅可以促进菌体增殖,而且还可缓冲基质pH值的变化,避免了低pH值对乳酸菌的伤害;利用L9(33)正交试验,筛选出S.t-3的麦芽复合汁增菌培养基最佳配比为:在10%的麦芽汁中添加0.5%大豆蛋白胨、0.5%酵母膏、1%牛肉膏、0.2%K2HPO4;在麦芽复合汁增菌培养基中,S.t-3、L.b-DR和L.b-S1,37℃恒温培养16 h,活菌数分别为2.42×109cfu/mL、2.85×109cfu/mL和4.81×109cfu/mL,与液体MRS培养基的活菌数相当,成本较MRS培养基降低1 000元人民币/t。

In this paper, effects of adding different nutriment in wort medium on the growth of Streptococcus therrnophilus （S. t-3） were studied. Furthermore, the optimum enrichment medium of S. t-3 were screened by orthogonality test, then the growth situation of Lactobacillus bulgaricus （L. b-DR, L. b-S1 ） in the optimum medium was tested. The results showed that S. t-3,L, b-DR, L. b-S1 grew well in wort medium. Soya peptone, Beef Extract, Yeast Extract could promote the growth of S. t-3 significantly. For K2HPO4, it could not only promote bacteria＇ s growth, but also protect lactobacillus from being damaged by low pH of medium. The optimum enrichment medium obtained by orthogonality test consist of adding 0.5 % Soya peptone,0.5 % Yeast Extract, 1% Beef Extract,0.2 % K2HPO4 in the 10 % wort medium. The living number of S. t-3, L. b-DR, L. b-S1 cultivated for 16 hours in the optimum enrichment medium at 37℃ were 2.42 ×10^9 cfu/mL,2.85 ×10^9 cfu/mL,4.81 ×10^9 cfu/mL which was the same with the living number in the MRS used in lab, but the production cost was decreased 1 000 yuan/t compared with using MRS medium.