高活性乳酸菌发酵剂培养条件优化及活性测定

Optimization of Cultural Condition and Activity Determination of Highly Active Lactobacillus Leavening Agent

采用自行分离选育的乳酸菌进行混合培养，对浓缩培养条件进行正交试验，以德氏乳杆菌保加利亚亚种和嗜热链球菌的菌数及其比值作为考察指标。结果为以改良MRS为基础培养基，以6％番茄汁、0．3％玉米浆作为生长因素，42℃培养，过程采用流加氨水作中和试剂，使培养基酸度控制在pH6．0，浓缩培养液中菌数可达9．15×10^9个／mL，球菌与杆菌比例为1．2：1；最佳菌体收集时间为7．5h；-30℃下冷冻干燥得到的乳酸菌发酵剂含活菌数达到8．2×10^10个／g，球菌与杆菌比例为1．5：1，发酵剂活性达0．435；0～4℃冷藏6个月，乳酸菌活性没有损失。产品可直接加入到灭菌奶中发酵，具有大众化特点，广泛用于各类乳品厂、饭店、食堂及家庭。

A self-isolated and bred lactobacillus strain was adopted to carry out mixed culture and orthogonal experiment on concentrated culturing condition. The cell number of Lactobacillus delbruckii subsp, bulgaricus and Streptococcus thermophilus and their ratio were set as an observation indexes. The results showed that when using improved MRS as a basic medium, added with 6% tomato juice and 0.3% com syrup as growing factors, culture at 42℃ , during the process adding aqua ammonium as neutralizer adopting flow-adding method to control the medium acidity at pH6.0, the cell number in the concentrated medium could reach up to 9.15 × 10^9/mL, and the proportion of coccus and bacillus was 1.2 ： 1, and the optimum cell collection time was 7.5h. A laetobaeillus-leavening agent was obtained with - 30℃ freeze-drying method, containing 8.2 × 10^10/mL of live cell, with 1.5 ： 1 of the ratio of coccus and bacillus, and 0. 435 of the vitality of leavening agent. After storing at 0-4℃ for six months, no vitality lost of laetobacillus was found. The performance of the laetobacillus leavening agent was the same as similar imported one. It can be directly added into sterile milk and fermente, has popular characteristics and is widely used in various dairy factory, restaurant, dining-hall and family.