干酪乳杆菌LZ183E高密度培养条件优化

为提高干酪乳杆菌LZ183E在发酵培养液中的菌体密度，首先通过在不同温度下培养菌株，测定48 h内菌液的OD600 nm值并作出生长曲线，得到菌株最适培养温度为37 ℃、接种时间为16 h及收获时间30 h。随后通过单因素试验和正交试验优化，探究不同碳源、氮源、生长因子、初始pH值以及接种量对菌株LZ183E活菌数和OD600 nm值的影响。结果表明，菌株LZ183E的最佳培养条件为葡萄糖25 g/L、酵母膏20 g/L、南瓜汁24 g/L、初始pH 6.5以及接种量2%。此优化条件下，干酪乳杆菌LZ183E的活菌数对数值达到了9.20±0.04，满足高密度培养要求，并且比原始MRS培养基活菌数对数值（8.12±0.06）高出一个数量级，为干酪乳杆菌LZ183E的冻干保护提供了足够的活菌数。

Optimization of high density culture conditions of Lactobacillus casei LZ183E

In order to increase the cell density of Lactobacillus casei LZ183E in the fermentation liquid, first, by cultivating the strains at different temperatures, the OD600 nm value of the bacterial solution within 48 h was measured and the growth curve was drawn, and the optimal culture temperature, inoculation time and harvest time of the strain was obtained, which was 37 ℃, 16 h and 30 h, respectively. Then the effects of different carbon sources, nitrogen sources, nutritional factors, initial pH value and inoculum on the viable count and OD600 nm value of strain LZ183E were explored through single factor experiments and orthogonal experiments optimization. The results showed that the optimal culture conditions of strain LZ183E were glucose 25 g/L, yeast extract 20 g/L, pumpkin juice 24 g/L, initial pH 6.5 and inoculum 2%. Under the optimal conditions, the logarithm value of viable count of L. casei LZ183E reached 9.20±0.04, which met the high-density culture requirements, and was an order of magnitude higher than the original MRS medium (8.12±0.06), which provided a sufficient viable count for lyophilization protection of L. casei LZ183E.