Lactobacillus helveticus ND-01培养条件的优化及冻干发酵剂的制备

Optimization of Fermentation Conditions for Lactobacillus helveticus ND-01 and Preparation for Freeze-dried Starter

瑞士乳杆菌Lactobacillus helveticus ND-01是一株分离、筛选自新疆酸马奶中的乳酸菌,并且在发酵牛乳的过程中能产生较高的ACE-Ⅰ抑制活性和γ-氨基丁酸。实验通过对L.helveticus ND-01培养基的组分进行优化,从而得出L.helveticus ND-01优化培养基配方为:乳糖25 g/L,大豆蛋白胨14.1 g/L,酵母粉14.1 g/L,醋酸钠15.3 g/L,柠檬酸纳6.5 g/L,K2HPO42.2 g/L,MgSO4.7H2O 2 g/L,MnSO4.5H2O 25 mg/L,吐温-80 1 g/L,L-半胱氨酸盐酸盐750 mg/L,维生素B9(VB9)20 mg/L。L.helveticus ND-01在此培养基中经42℃,18 h培养,其活菌数可达到4.2×108cfu/mL,比MRS中(8.2×107cfu/mL)提高近5倍。将此优化培养基作为基础培养基,在5 L发酵罐中,经优化发酵条件,其活菌数可达到3.1×109cfu/mL,发酵液离心收集菌体,加入保护剂,冷冻干燥后活菌数可达到2.5×1010cfu/g。冻干菌粉经90 d的低温贮藏,其存活率为81.20%。

LactobaciUus helveticus ND-01 is a lactic acid bacteria isolated from Koumiss in Xinjiang. It can produce higher inhibitory activity against ACE- Ⅰ and γ-aminobutyric acid during the fermentation process. The medium components for L. helveticus ND-01 were optimized by response surface methodology, which contained lactose（25 g/L）, soy peptone（ 14.1 g/L） , yeast extract（ 14.1 g/L） , sodium acetate（ 15.3 g/L） , sodium citrate（6.5 g/L） , K2HPO4 （2.2 g/L）, MgSO4· 7H2O （2 g/L）, MnSO4· 5H2O （25 mg/L）, tween-80 （ 1 g/L）, L-cysteine （750 mg/L）, Vitamin B9 （ VB9 ） 20 mg/L. After cultivation in optimization medium for 18h at 42℃, the viable count of L. helveticus ND-01 was 4.2 × 10^8 cfu/mL, which was about 5 times higher than that in MRS（8.2 × 10^7 cfu/mL）. Fermentation conditions were optimized using this enrichment medium as the basal medium culture in the 5L fermentor, the viable count of L. helveticus ND-01 reached 3.1 × 10^9 cfu/mL. After centrifugal separation of the cell form fermentation broth and freeze drying, a viable count of 2.5 × 10^10 cfu/g was obtained. After 90 days storage, survival rate of the freeze drying starter reached 81.20%.