Based on the successful isolation of a bacterial strain of Lactobacillus sp. USTB-08 for producing lactic acid, the opti- mal 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 50 L automatic fermenter, the maximum biomass of Lactobacillus sp. USTB-08 （OD680nm 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. Off, respective- ly. The strategy of feeding sucrose and controlling the pH value simultaneously was firstly used in the fed-batch cultivation of Lactoba-cillus sp. , and both high cell density and high lactic acid content were obtained.
LactobaciUus sp.cultivationgrowthlactic acidpH control
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