Screening and identification of liver lipid-lowering probiotic bacteria for fish
To obtain probiotics that can prevent and alleviate fatty liver disease in fish,13 strains of aquatic animal gut bacteria screened from Gynoglossus semilaevis Gunther were used as experimental strains.The strains with strong bile salt hydrolase production were obtained through the detection of bile salt hydrolase production in vitro.The feeding and bathing experiments of zebrafish were carried out with 13 strains.The body mass and liver triglyceride content of zebrafish were determined,and the liver sections were stained with oil red O for observation.Molecular identification and phylogenetic tree construction were car-ried out for the strains which could degrade zebrafish liver fat efficiently.The results showed that strains ND-1 and U3 had the highest bile salt hydrolase activity,followed by strains SC-03 and YA6.The cholesterol removal rates of strains ND-1 and YA6 were 89.76%and 89.69%,and those of strains M4 and U3 were 80.26%and 76.39%,respectively.Strains YZ-02,U2,SC-04 and ND-1 could reduce the body mass of zebrafish,strains SC-01,YZ-02,U3 and SH-1 reduced the triglyceride content in ze-brafish liver,and strains YZ-01,ND-1 and U3 could effectively alleviate lipid droplets deposition in zebrafish liver.Overall,strains U3 and ND-1 had the best effect on reducing lipid in fatty liver of zebrafish.The results of molecular identification and construction of phylogenetic tree showed that ND-1 could combine with Staphylococcus equiorum strain Y15(JX134628)with confidence of 100%,and strain U3 could combine with Lactobacillus rhamnosus strain 5681(MT463591)with confidence of 98%.