类植物乳杆菌L-ZS9培养基及培养条件的优化

类植物乳杆菌L-ZS9分离自发酵肉类食品，作为益生菌制剂和发酵剂在乳品行业具有良好的应用潜力。为实现类植物乳杆菌L-ZS9的高密度培养，以MRS培养基为基础进行培养基的优化，并优化培养条件。以单因素试验初步确定培养基中所用的碳源和氮源，通过Plackett-Burman试验确定出培养基成分与培养条件中影响较大的因素，经最陡爬坡试验确定各因素的水平，再通过响应面旋转中心组合试验拟合出菌体密度与因素水平间的方程，从而确定优化后的培养条件。结果表明：培养基中所用的碳源为蔗糖，氮源为酵母粉；经过验证实验得到的优化

Optimization of Medium Composition and Culture Conditions for Lactobacillus paraplantarum L-ZS9

Lactobacillus paraplantarum L-ZS9, isolated from fermented meat foods, as a probiotic strain and a fermentation starter has a great application potential in the dairy industry. In order to achieve high-density culture of strain L-ZS9, the modified MRS medium and culture conditions were optimized. The optimal carbon and nitrogen sources were selected by one-factor-at-a-time method. The Plackett-Burman experimental design was used to recognize the most significant medium components and culture conditions. The steepest ascent method was used to determine the levels for these variables. A central composite rotary design (CCRD) was used to fit cell density as a function of the independent variables and response surface methodology was employed to determine optimal culture conditions. The results showed that sucrose and yeast powder were used as carbon and nitrogen sources, respectively. The optimized medium formulation consisted of sucrose 3%, yeast extract 7.26%, sodium acetate 0.5%, dipotassium phosphate 0.2%, magnesium sulfate 0.02%, triammonium citrate 0.2%, and Tween-80 0.1%; the optimized culture conditions were as follows: the initial pH value of the medium was 9.53, the volume of inoculum was 1.74%, and the culture temperature was 37 ℃. It was verified that after 14 hours of cultivation under the optimized conditions, the optical density at wavelength of 600 nm of the broth was 1.214, and the viable count was 4.53 × 109 CFU/mL at this time, which was 6 times higher than that before optimization.