Screening of ACE-inhibiting Peptide Producing Strains and Their Activity Analysis in Simulated Digestive Tract Environment

The acid production capacity, protein hydrolysis activity, ACE inhibition activity, simulated gastrointestinal digestion and acid, bile salt and salt tolerance of 27 strains of lactic acid bacteria kept in the laboratory were determined in order to screen for those with high angiotensin-converting enzyme (ACE) inhibition activity and high acid, bile salt and salt tolerance. The results showed that the ACE inhibition rate of strain M3 could reach 71.94%±1.39%, with good protein hydrolysis activity and acid production ability, the protein hydrolysis activity was (86.66±3.51) μg/mL leucine, and the titration acidity was (71.67±2.86) °T. The ACE inhibition rate of strain M3 was 74.96%±1.73% after 3 h of treatment with artificial gastrointestinal fluid, respectively. It was treated for 3 h in pH3 broth medium and the survival rate was 14.34%±1.21% and the viable count could reach more than 7 lg CFU mL⁻¹. It was treated for 3 h in broth medium containing 0.3% bile salts and the survival rate was 37.50%±2.47%. It was treated for 24 h in broth medium containing 4% NaCl and the survival rate was 37.32%±1.84%. The bacterium was identified by 16S rDNA as Lactobacillus (Lb.) paracasei subsp. paracasei M3. Thus, Lb. paracasei subsp. paracasei M3 can be used as an ACE-inhibiting peptide-rich strain for fermenting cow’s milk and tolerating the digestive environment with probiotic potential.