Bile Salt Hydrolase Activity Screening and Resistance to the Toxicity of Bile Salt by Indigenous Lactobacillus Isolates of Pakistan; A Research Article

摘要

Objective: In this study 20 Lactobacillus strains isolated from different sources were selected for an account of their high bile-salt hydrolase (BSH) activity, bile-salt resistance, and tolerance to the toxicity of bile salts. Method: Bile salt hydrolase and resistance to toxic effects of bile salts were checked by assay for Deconjugation of bile salts and by toxicity of conjugated bile salt assay Results: A total of 20 isolates were tested for hydrolase activity of conjugated bile salts sodium salt taurocholic acid and glycocholic acid while toxicity of bile salts was in MRS broth supplemented various concentrations of bile salts. Out of 20 strains 2 strains displayed the largest precipitation zones were selected for toxicity assay. . Conclusion: The present study suggested that the finally two indigenous isolated of Lactobacillus from Pakistan has an excellent hypocholesterolemic effects. They will be used as a Probiotics to prevent hypercholesterolemia from human health while the mechanisms of regulating serum cholesterol and the effect on serum cholesterol level in vivo needs further extensive investigations. Introduction Serum cholesterol is important from the public health because higher concentrations are often associated with a greater risk to cardiovascular diseases. Elevated level of cholesterol in ruminants could possibly due to their increased synthesis to meet the requirements for fat digestion and absorption in the intestine or slower rate of cholesterol disposal (Scott and Cook, 1975). Bile salts are synthesized mainly from cholesterol, conjugated with taurine or glycine in the liver (Batta et al., 1999).Deconjugated bile acids are excreted more rapidly from the intestinal tract than are conjugated bile salts. While free bile acids are excreted more rapidly from the body, thus the synthesis of new bile salts from cholesterol can reduce the total cholesterol concentration in the body (Gilliland and Speck, 1977) while the enzyme responsible for the deconjugation activity, is bile salt hydrolase (BSH) (Grill et al. 1995). Some natural occurring microorganisms in human intestine are beneficial in terms of lowering cholesterol (Buck and Gilliland, 1994: Fernande, et al. 1987: Fukushima, et al. 1999; Mann and Spoerry, 1974).It was also reported that Lactobacillus reduces blood cholesterol by direct breakdown of cholesterol and deconjugation of bile salts (Oh and Lee, 2000). Various attempts have shown that species of Lactobacilli were capable of lowering serum cholesterol and reducing the severity of hypercholesterolemia either by lowering total elevated serum cholesterol or reducing low density lipo-proteins LDL.Therefore, in vitro strain selection for hypercholesterolemic probiotic bacteria can base on bile tolerance and deconjugation of bile salts. This study also aimed to evaluate the potential hypocholesterolemic abilities of indigenous Lactobacillus species. Material and methods Media and Chemicals MRS (Oxoid) broth and agar were used in all the experiments. Sodium salt of Taurocholate (TCA) and Glycocholic acid (GCA) and Oxgall (Ox) were obtained from Sigma.Bacterial Strains20 of Lactobacillus strains were isolated from the human faeces, dairy or other sources of Pakistan were collected in the sterilized screw capped bottles (sterilized at 121 °C for 20 minutes in the autoclaved from different areas of Karachi. The samples were brought to the Center for Molecular Genetics, University of Karachi and stored immediately under refrigeration conditions for further processing. They were grown anaerobically in MRS broth at 37 C. Stock cultures at -80 C were prepared from overnight cultures grown in MRS to which 15% glycerol was added to adjust the prior to freezing.Qualitative assay for Deconjugation of bile salts.Qualitative BSH activity of the isolated strains was evaluated using the procedure described by du Toit et al. (du Toit et al., 1998). Bile salt agar plates were prepared by adding 0.5% of sodium salt of ta