Investigations on the capacity of lactic acid bacteria to produce ace inhibitory peptides

Abstract

The individual and interactive effects of inoculum size, fermentation time and ratio of the freeze-dried Lactobacillus bulgaricus powder LB6 and the freeze-dried Streptococcus thermophilus powder ST78 on pH, optical density (OD) and Angiotensin converting enzyme (ACE) inhibitory activity were studied by Response Surface Methodology (RSM). As a result, the optimal starter culture formulations were obtained. It was shown that the optimal inoculum size and fermentation time were 0.3% and 4.5 h respectively, for an optimal LB6:ST78 ratio of 3:2. The experimental values of pH, OD and ACE inhibitory activity were 4.71±0.03, 0.962±0.031 and 85.16±0.05 %, which were very close to the predicted values 4.70, 0.963 and 85.10%.