Research On Function And Safety Of Two Lactic Acid Bacteria With High Antioxidant Ability

Probiotics are living microorganisms that,when ingested in sufficient quantities,provide health benefits.However,to be incorporated into medicine or as a functional food in the diet,probiotics require detailed studies to prove their safety and benefits.This study was designed to assess the function and safety of two Lactobacillus plantarum strains(L12 and L20)isolated from traditional fermented foods of northeast China(spicy cabbage and hot sauce),which have high antioxidant ability.The study was subdivided into three stages;initially,various functional characteristics of the strains were evaluated including nitrate degradation ability,cholesterol degradation ability,lactose decomposition ability,cell adhesion ability.In the second stage,various chemical and biological indicators of the strains were analyzed in vitro,such as sensitivity to antibiotics,hydrolysis activity of bile salts,D-lactic acid content,hemolytic activity,and an experiment to detect harmful metabolites.Then,a short-term in vivo oral toxicity study was conducted in Kunming mice,which received 0.2 m L(10~9 CFU/m L)of experimental bacterial solutions(L12 and L20)orally for 30days during which various body indices were measured.After the sacrifice,blood samples were taken to determine the concentration of glutathione,eyeballs were used to determine the serum concentration of malondialdehyde,and the weights of the kidney,heart,spleen and liver were checked as well as the histopathology of these organs.The results obtained were processed with ANOVA,Tukey,and Duncan(p<0.05),using the SPSS statistical package.The results showed that the two strains tested have good probiotic properties,in particular good adhesion ability,a higher capacity to remove cholesterol from media,good lactose degradation rates,a higher ability to degrade nitrates,high sensitivity to antibiotics,high hydrolase activity of bile salts and low content of D-lactic acid.No drug-resistant plasmid was extracted from the two experimental strains.The amino decarboxylase,nitrate reductase,and indole tests of the experimental strains(L12 and L20)were all negative.Furthermore,all strains were non-hemolytic.The administration of the two strains to mice has no adverse effects on the general condition,growth,behavior,food intake,organ weight,or histopathological analysis of the treated mice.Compared with control mice,the serum malondialdehyde concentration and liver glutathione content of probiotic-treated mice were statistically different.No bacterial translocation was found in each group of mice.These results suggest that Lactobacillus strains(L12 and L20)are nonpathogenic and likely to be safe for human consumptions,hence could be used as potential pharmaceutical probiotic strains for food industry and human nutrition.