益生菌的筛选及其发酵特性研究

为获得性能优良的益生菌生产菌株，通过乳酸菌的溶钙圈筛选，耐酸、耐胆盐检测及体外抗氧化和分解胆固醇能力测试进行了菌株的选育；对筛选菌株进行16S rRNA基因测序及生理生化特性鉴定；采用正交试验优化培养基配方和发酵条件。结果表明，从牛奶储罐中分离、筛选到一株各项性能优良的菌株，编号为SX68，经鉴定其为植物乳杆菌（Lactobacillus plantarum）。优化培养基配方为：蛋白胨10 g/L，牛肉膏10 g/L，酵母提取物5 g/L，磷酸氢二钾3 g/L，柠檬酸氢二胺4 g/L，乙酸钠5 g/L，葡萄糖30 g/L，吐温-80 1 mL/L，MgSO4·7H2O 0.58 g/L，MnSO4·4H2O 0.25 g/L，pH 6.4；最佳发酵条件为：起始pH 6.5，发酵温度35 ℃，接种量20 mL/L，溶氧量＜100 mL/L，搅拌转速50 r/min，罐压0.03 MPa。在此优化条件下，菌株SX68最高发酵生物量（OD600 nm值）为15.68，活菌数为9.6×1012 CFU/mL，可为其用于益生菌生产奠定基础。

Screening and fermentation characteristics of probiotics

In order to obtain superior probiotics production strains, the strains were screened by the calcium dissolving zone of lactic acid bacteria, acid and bile salt resistance tests, the in vitro anti-oxidation ability and cholesterol decomposing tests. The isolated strain was identified by 16S rRNA gene sequencing and physiological and biochemical characteristics. The medium formulation and fermentation conditions were optimized by orthogonal experiments. The results showed that a strain with excellent performance was isolated and screened from the milk tank, numbered SX68, and identified as Lactobacillus plantarum. The optimized medium formula was as follows: peptone 10 g/L, beef extract 10 g/L, yeast extract 5 g/L, dipotassium hydrogen phosphate 3 g/L, diamine hydrogen citrate 4 g/L, sodium acetate 5 g/L, glucose 30 g/L, Tween-80 1 ml/L, MgSO4·7H2O 0.58 g/L, MnSO4·4H2O 0.25 g/L, pH 6.4. The optimal fermentation conditions were as follows: initial pH 6.5, fermentation temperature 35 ℃, inoculum 20 ml/L, dissolved oxygen＜100 ml/L, stirring speed 50 r/min, tank pressure 0.03 MPa. Under these optimized conditions, the maximum fermentation biomass (OD600 nm value) of strain SX68 was 15.68, and viable bacteria count was 9.6×1012 CFU/ml, which could lay a foundation for its application in probiotics production.