| Probiotics regulate the intestinal ecological balance and have a healthy impact on the host.Much attention is paid to lactic acid bacteria and bifidobacteria.With the continuous development of the probiotic industry,more and more probiotics have been developed and applied.Bile salt tolerance is an important factor that must be considered in the probiotic screening process.Only strains that have bile salt tolerance can be successfully colonized in the intestine and have the healthy effect.In this paper,the biological properties of several strains of Lactobacillus were studied.The results showed that Lactobacillus plantarum Lp-115 had a strong growth ability,and it could tolerate high concentrations of bile salts,and had a strong permeability,antimicrobial capacity and gastric juice resistance,so this bacterium was chosen as a research object for further study.In order to better improve the bile salt tolerance of Lactobacillus plantarum Lp-115,six different carbohydrates were tested in this paper.Among them,maltodextrin had a significant improvement,and the optimum addition was 4.0%.In addition,the mechanisms of enhanced bile resistance were investigated from four aspects.The results showed that maltodextrin could not promote the strain growth directly,but enhance the cell hydrophobicity,shift the fatty acid composition of cell membrane,and improve the transcription level of the bile salt hydrolase gene(pva3).In order to conduct in-depth studies on the bile salt tolerance of Lactobacillus plantarum Lp-115,BSH1 was constructed in vitro and its basic enzymatic properties were determined.The optimal substrate was GDCA,the optimum temperature and pH range were 37? and 5.0 to 6.0.Mn2+ and glycerol could increase enzyme activity,while Cu2+,Co2+,and Zn2+ had strong inhibitory effects.In addition,the related kinetic parameters of this enzyme were determined.All of these experiments would advance our understanding of the properties of BSH1. |
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