德氏乳杆菌DMLD-H1的生物学特性研究及发酵培养基优化

Study on Biological Characteristics of Lactobacillus delbrueckii DMLD-H1 and Optimization of Fermentation Medium

从内蒙古家庭自制酸奶中筛选出一株乳杆菌,经生理生化与形态学鉴定,并结合16S rDNA同源性分析可知,该菌株为德氏乳杆菌(Lactobacillus delbrueckii DMLD-H1)。对菌株的生物学特性进行研究,阐明菌株的胃肠道耐受性、抑菌效果及益生特性,通过溶血性实验和急性毒理学实验对菌株进行安全性评估,采用响应面法优化菌株发酵培养基。结果表明,DMLD-H1菌株适合在37℃与pH 3.0~7.0的条件下快速生长。血平板研究表明该菌株不具有溶血活性,急性毒理学实验证明德氏乳杆菌DMLD-H1对小鼠经口无急性毒性,具有食用安全菌的特性。在pH 3.0~4.0的人工胃肠液条件下孵育3 h后,菌株存活率大于85%,具有良好的耐受性,菌发酵产物对大肠杆菌和金黄色葡萄球菌均有抑制效果,表明德氏乳杆菌DMLD-H1具有潜在的益生特性。当发酵培养基最佳组分优化为20.2 g/L低聚果糖、19.7 g/L细菌学蛋白胨及0.596 g/L硫酸镁时,多元回归模型预测德氏乳杆菌DMLD-H1的活菌浓度为1.32×10^(9)CFU/mL,在此条件下与实测值的拟合率为98.48%,表明多元回归模型能较好地预测培养基优化后的菌体生长特性。

A strain of Lactobacillus was isolated from the homemade yogurt in Inner Mongolia.Through physiological,biochemical and morphological identifications and 16S rDNA homology analysis,the strain was known to be Lactobacillus delbrueckii DMLD-H1.The biological characteristics of the strain were studied to clarify its gastrointestinal tolerance,antibacterial effect and probiotic characteristics.The safety of the strain was evaluated through hemolytic experiment and acute toxicity test.The fermentation medium of the strain was optimized by response surface methodology.The results show that Lactobacillus delbrueckii DMLD-H1 grow rapidly at the optimum temperature of 37℃and pH value ranging from 3.0~7.0.The blood agar plate study shows that the strain has no hemolytic acti-vity.The acute toxicity test indicates that Lactobacillus delbrueckii DMLD-H1 has no acute oral toxicity to mice.Thus the strain has the characteristics of edible bacteria.After incubation for 3 h in artificial gastric and intestinal juice whose pH value is 3.0~4.0,the survival rate of the strain is above 85%,with good tolerance.Its fermentation products have inhibitory effects on both Escherichia coli and Staphylococcus aureus,indicating that Lactobacillus delbrueckii DMLD-H1 has potential probiotic properties.When the best components of the fermentation medium are optimized as follows:oligo-fructose content 20.2 g/L,bacteriological peptone content 19.7 g/L and magnesium sulfate content 0.596 g/L,the concentration of viable bacteria of Lactobacillus delbrueckii DMLD-H1 is 1.32×10^(9)CFU/mL.Under this condition,the fitting rate between the above-mentioned concentration and the measured value is 98.48%,indicating that after the optimization of the medium,the model can well predict the bacteria s growth characteristics.