Abstract
Growth and bile salt hydrolase (BSH) activity of the isogenic Lactobacillus plantarum 80 (LP80) strains were studied in vitro. In pure culture experiments viability and growth performance of the BSH- LP80 strain was negatively affected by the presence of conjugated bile salts. The LP80 wild type (WT) and BSH overproducing LP80 (pCBH1) strains did not show a die-off upon supplementation of bile salts. The latter strains hydrolysed glyco-conjugated deoxycholate (GDCA) more readily than tauro-conjugated deoxycholate (TDCA), indicating substrate specificity of the enzyme. BSH activities towards TDCA of LP80 WT and LP80 (pCBH1) stationary phase cells were 017 and 1.02 μmol/mg CDW.h respectively; activities towards GDCA of the respective strains were 3.52 and 54.80 μmol/mg CDW.h respectively. The study of BSH activity as a function of growth revealed a marked difference in behaviour between LP80 WT and LP80 (pCBH1) with LP80 WT hydrolysing GDCA when reaching the exponential phase, whereas LP80 (pCBH1) immediately started to hydrolyse GDCA. TDCA hydrolysis increased after GDCA hydrolysis was completed. BSH activity of LP80 (pCBH1) in a mixed microbial association, resembling that of the small intestine, was comparable to that determined under pure culture conditions, indicating that BSH activity will probably not be influenced by the presence of the normal intestinal microbiota. Based on the BSH activity of LP80 (pCBHl) and on physiological data on the bile salt-cholesterol metabolism interrelationship, it was calculated that a daily intake of a realistic amount of highly BSH active Lactobacillus cells, e.g. in the form of yoghurt, might lead to a significant reduction of cholesterol. Hence, this in vitro study indicates that altering BSH activity can be a valid (micro) biological alternative treatment for patients with severe hypercholesterolaemia.