乳酸菌USTB--08的高效培养和生产乳酸

在成功筛选出一株高产乳酸的乳酸菌USTB--08基础上,分别采用批量和补料发酵培养,通过改变碳源、氮源、碳氮比、温度和pH值等研究了乳酸菌USTB--08生长和产乳酸的优化控制条件.采用蔗糖和酵母膏作为唯一碳源和氮源（碳氮质量比为5∶1）、温度35℃、接种量1.0%及初始pH 6.50是提高乳酸菌生长的优化参数.进一步在50L全自控发酵罐中,采用质量分数为10%氢氧化钠和25%蔗糖混合溶液作为控制pH值和碳源补料的流加液,在pH 6.00～7.00范围内,恒定控制pH 6.50获得了最大的乳酸菌生物量（OD680nm 13.2）,而恒定控制pH 7.00则获得了最高的乳酸含量（28.0 g.L-1）.本研究首次采用控制pH值与流加蔗糖同步进行的培养方式,获得了高细胞浓度的乳酸菌和高质量浓度的乳酸.

High-density cultivation of Lactobacillus sp. USTB-08 and production of lactic acid

Based on the successful isolation of a bacterial strain of Lactobacillus sp.USTB-08 for producing lactic acid,the optimal control conditions including carbon source,nitrogen source,mass ratio between carbon and nitrogen source,temperature and pH values were investigated for the growth of Lactobacillus sp.USTB-08 and the production of lactic acid in batch cultivation and fed-batch fermentation.Sucrose as the sole carbon source,yeast extract as the sole nitrogen source,the mass ratio of carbon to nitrogen source of 5∶1,35 ℃,the inoculum amount of 1.0% and initial pH 6.50 are the optimal parameters for the growth of Lactobacillus sp.USTB-08 in batch cultivation.In fed-batch cultivation by feeding a mixture of 10% sodium hydroxide and 25% sucrose to control the pH value and supply the carbon source in a 50L automatic fermenter,the maximum biomass of Lactobacillus sp.USTB-08(OD680 nm 13.2) and the maximum content of lactic acid(28.0g·L-1) are obtained at pH 6.50 and pH 7.00 in a pH range from 6.00 to 7.00,respectively.The strategy of feeding sucrose and controlling the pH value simultaneously was firstly used in the fed-batch cultivation of Lactobacillus sp.,and both high cell density and high lactic acid content were obtained.