高光学纯度乳酸菌株的筛选及发酵性能研究

Study on screening and fermentation performance of lactic acid bacteria with high optical purity

从不同地区的土壤、泡菜中分离筛选出了2株高光学纯度D-乳酸菌株和2株高光学纯度L-乳酸菌株。通过形态学观察、生理生化鉴定和16S rDNA序列分析,确定L-乳酸产生菌HA7-5菌株为屎肠球菌(Enterococcus faecium),HJ57菌株为格氏乳球菌(Lactococcus garvieae);D-乳酸产生菌HB49-2菌株为德氏乳杆菌(Lactobacillus delbrueckii),HL64-1菌株为假肠膜明串株菌(Leuconostoc pseudomesenteroides)。经摇瓶发酵产酸培养,菌株HA7-5和HJ57发酵产L-乳酸分别达71.83 g/L和31.89 g/L;菌株HB49-2和HL64-1发酵产D-乳酸分别达73.14 g/L和62.04 g/L,且菌株HL64-1发酵周期仅为24 h,产酸速率快,平均产酸速率为2.58 g/(L·h)。D体和L体光学纯度均达99.8%(ee)以上。以上菌株均为产高光学纯度L-或D-乳酸野生型菌株,可作为后期诱变育种的出发菌株,进行菌株改良及发酵性能提升的研究。

Two strains of high optical purity D-lactic acid(D-LA)bacteria and two strains of high optical purity L-lactic acid(L-LA)bacteria were isolated and screened from soils and pickles in different regions.Through morphological observation,physiological and biochemical identification,and 16S rDNA sequence analysis,it was determined that strain HA7-5 was Enterococcus faecium,strain HJ57 was Lactococcus garvieae,strain HB49-2 was Lactobacillus delbrueckii,and strain HL64-1 was Leuconostoc pseudomesenteroides.HA7-5 and HJ57 strains produced L-LA at concentrations of 71.83 g/L and 31.89 g/L,respectively,by shaking flask fermentation.HB49-2 and HL64-1 strains produced D-LA at concentrations of 73.14 g/L and 62.04 g/L,respectively.Notably,strain HL64-1 had a fermentation cycle of only 24 hours and exhibited a high acid production rate,averaging 2.58 g/(L·h).Both the D and L isomers exhibited high optical purities above 99.8%(ee).These strains,as wild-type strains producing high optically pure L-or D-lactic acid,can serve as starting strains for subsequent mutation breeding to enhance strain improvement and fermentation performance.