乳酸菌分解草酸体外试验与影响因素

Test of Oxalate-Degrading Ability of Lactic Acid Bacteria in vitro Culture and Influencing Factor

目的研究乳酸菌菌种在体外培养基中的草酸分解能力和耐草酸生长能力。方法鉴定6种市售品牌酸奶所含的乳酸菌菌种。将不同品牌的酸奶分别接种在MRS培养基中,37℃、5%CO2培养48h,平板计数法分别测得乳酸菌的浓度,选择乳酸菌浓度最高的酸奶品牌作为研究对象。将各纯菌种和从选定的品牌酸奶中培养所得的混合乳酸菌分别接种在3种不同草酸浓度的MRS液体培养基中,设置空白对照组,培养72h后检测培养基中乳酸菌数量的变化,铬酸钾氧化甲基红催化光度法测量草酸浓度变化。结果市售品牌酸奶均含有3种乳酸菌(保加利亚乳杆菌、嗜酸乳杆菌、嗜热链球菌),其中味全牌酸奶所含乳酸菌数量最多。经过72h培养,所有培养基中的草酸浓度都有不同程度的下降,但乳酸菌组的降幅明显大于对照组,其中嗜酸乳杆菌组的降幅最大。环境草酸浓度越高,乳酸菌的草酸分解绝对量也越大,但相对分解率越低,乳酸菌繁殖速度减慢。结论市售酸奶中所含的乳酸菌种均具有草酸分解能力,并随着环境草酸浓度的增加而增加;但高草酸浓度使乳酸菌的生长趋缓。

Objective To investigate the oxalate-degrading and growth abilities of lactic acid bacteria coming from yoghourt in vitro culture broth. Methods The species of lactic acid bacteria obtained from 6 brands of yoghourt were identified. Different brands of yoghourt were separately cultured in broth and incubated at 37℃, 5% CO2 for 48 h, getting the concentration of lactic acid bacteria through slab counting method. The brand of yoghourt with the highest quantity of bacteria was chosen as the study subject. Three species of bacteria and the mixture bacteria obtained from the chosen brand of yoghourt were cultured separately for 72 h in MRS broth which contained three different concentrations of ammonium oxalate, and the broth without inoculating of bacterium was prepared as control. The amount of bacteria in cuhure was detected, the concentration of ammonium oxalate was detected through photometric determination of oxalic acid by its catalytic reaction of methyl red by potassium chromate. Results Three species of lactic acid bacteria （ L. bulgaria, L. acidophilus and L. thermophilus ） were detected in each brand of yoghourt. The quantity of bacteria in Weiquan yoghourt is the highest. After 72 h incubation, the concentrations of oxalate in all the broths containing bacteria were lower than those in the control. L. acidophilus showed the best degrading activity. The higher the concentration of oxalate was, the bigger the amount of oxalate degraded was, the smaller the percent of degrading was, and the less the growth ability of bacteria was. Conclusion All the species coming from yoghourt have the ability of oxalate degrading, which increases with centration of oxalate restrains the growth of bacteria. the concentration of oxalate in culture. But the high concentration of oxalate restrains the growth of bacteria.