Optimized Co-fermentation of Horse Milk by Yeast and Lactic Acid Bacteria to Produce Angiotensin-converting Enzyme-Inhibiting Peptides

This study aims to obtain biologically active peptides with angiotensin-converting enzyme (ACE)-inhibiting activity by co-fermenting horse milk with lactic acid bacteria and yeasts isolated from traditional Koumiss. Lactococcus lactis L8 and Yarrowia lipolytica Y7, fermented milk with which inhibited ACE activity by 38.67% and 51.33%, were used for mixed-strain fermentation of horse milk. Horse milk fermented under optimum conditions determined using one-fact-at-a-time method and response surface methodology inhibited ACE activity by as high as 80.67%. The ACE-inhibiting activity significantly increased compared with that obtained with single-strain fermentation. An active fraction with ACE-inhibiting rate of 86% was separated from the co-fermented product. In conclusion, fermented horse milk is a potential source of ACE-inhibiting peptides.