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

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。

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

In this paper,effects of adding different nutriment in wort medium on the growth of Streptococcus thermophilus(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 K_2HPO_4,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% K_2HPO_4 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.