Abstract
In this study, two lactobacilli isolates, from dairy food and bovine rumen, were used to investigate the differences in their biochemical characteristics when exposed to low pH and bile salt stress conditions. Production of volatile compounds was analysed by gas liquid chromatography (GLC), alterations in fatty acid profiles of bacterial cells by chromatography-mass spectrophotometry (GC-MS), and changes in protein banding patterns were detected using 1D SDS PAGE. Significant differences were found in the production of acetic acid by stressed and non-stressed cells. Hexanoic acid and octanoic acid production was observed by the cells exposed to bile salt stress only. For both isolates, the saturated fatty acids (SFA) and monounsaturated fatty acids (MUFA) levels were significantly different for all treatments, except however an increased level of polyunsaturated fatty acids (PUFA) production under bile salts stress was observed. The comparison of the 1-D protein banding patterns of non-stressed and pH stressed and bile salts stressed cells revealed several protein bands were differentially expressed. Findings of this investigation suggest that lactobacilli isolates possess variation in biochemical characteristics on the basis of origin and in their response to low pH and high bile salt stress conditions.