培养基pH调控法高密度发酵唾液乳杆菌XH4B研究

High Cell Density Fermentation of Lactobacillus salivarius XH4B Via pH Adjustment

摘要:

本研究以MRS培养基为基础，通过优化碳、氮源及无机盐的配方和用量，再结合补料发酵，最终实现唾液乳杆菌XH4B高密度培养的目的。以乳酸菌的生物量为指标，同时考查发酵液pH值、乳酸含量等，最终确定酵母粉和蔗糖为最佳氮、碳源，同时增加乙酸钠用量至2%、磷酸二氢钠0.6%，可以对发酵液酸化时提供一定的缓冲作用。采用优化的PY-Suc培养基，唾液乳杆菌XH4B的生物量最高能达到6.91 g/L，明显高于MRS培养基的5.01~6.30 g/L（P<0.05）。等量补料培养并且采用NaOH中和发酵液pH值时，乳酸最高积累速度可以达到5.958 g/(L?h，但是随着培养时间延长，积累速度迅速下降。发酵酸化较严重时（乳酸含量9~10 g/L），唾液乳杆菌XH4B的生物量积累变缓。结论：优化MRS培养基，并加大乙酸钠、磷酸二氢钠等能够缓冲发酵液的无机盐用量，结合补料发酵，可以实现唾液乳杆菌XH4B的高密度培养。

Abstract:

Culture medium ingredients of nitrogen, carbohydrate and inorganic salts were optimized based on MRS for high cell density fermentation of Lactobacillus salivarius XH4B, including the adjustment of pH value as well as culture medium fed-batch. According to the biomass of L. salivarius XH4B, the best nitrogen and carbon sources were yeast extract and sucrose, respectively. Addition of sodium acetate (2%) and monosodium orthophosphate (0.6%) provided buffer effect for the pH value during incubation, these salts also contributed to LAB growth. By using the optimized PY-Suc culture medium, the biomass of L. salivarius XH4B reached 6.36~6.91 g/L, higher than that in MRS culture medium which was 5.01~6.30 g/L (P < 0.05). When lactic acid concentration exceeded 10 g/L, the accumulation of biomass ceased which meant the acid inhibited L. salivarius XH4B growth. Therefore, the optimization of MRS culture medium with sodium acetate and monosodium orthophosphate could buffer the pH value of culture medium, and new culture medium combined with fed-batch fermentation resulted in high cell density of L. salivarius XH4B.