利用L.casei及L.lactis发酵乳清渗透液生产高纯度L-乳酸

L-lactic acid production by batch fermentation of whey permeate using L.casei and L.lactis

以乳清渗透液为底物,补充其他营养成分,分批发酵生产L-乳酸。通过对8种乳酸菌的筛选,确定最佳发酵乳酸菌组合为L.casei和L.lactis(1︰1)。初始乳糖质量浓度为96 g/L时,乳酸生产效率最高且达到6.05 g/(L.h)。经过对发酵条件的优化,确立了最佳发酵条件:25%氢氧化钾溶液作为中和剂,发酵液pH值为6.0,在37℃进行厌氧发酵(通入100%氮气)。优化的发酵液组成:初始乳糖200 g/L,酵母提取物10 g/L,K2HPO4 1 g/L,MgSO4.7H2O 0.5 g/L,MnSO4.H2O 0.05 g/L。最高乳酸产量为192 g/L,L-乳酸纯度达95%,乳糖利用率达96%。

A nutrient supplementary batch fermentation was developed for production of L-lactic acid production from whey permeate using lactic bacteria cultures. Among screening from eight lactic acid bacteria, the best lactic acid-producing strains were the mixture of L. casei and L. lactis （1：1）. The maximum lactic acid production rate reached 6.05 g/（L. h） with the initial lactose concentration of 96 g/L. After optimization of media and fermentation conditions for L-lactic acid production by the mixed cultures, the optimum fermentation conditions were in anaerobic environment using 25% KOH solution as the neutralization agent at pH 6.0 and 37℃. The best fermentation media under those fermentation conditions consisted of lactose 200 g/L, yeast extract 10 g/L, K2HPO4 1.0 g/L, MgSO4.7H2O 0.5 g/L, MnSO4.H2O 0.05g/L. The highest production of lactic acid reached 192 g/L and the purity of L-lactic acid was 95% and lactose utilization rate was 96%.