Test of Oxalate-Degrading Ability of Lactic Acid Bacteria in vitro Culture and Influencing Factor / 上海第二医科大学学报

ABSTRACT

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 culture 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 the concentration of oxalate in culture.But the high concentration of oxalate restrains the growth of bacteria.