Abstract: The present study was designed to screen 77 probiotic strains based on α-glucosidase inhibitory activity of cell-free excretory supernatants (CFS) and cell-free extracts (CFE). Meanwhile, probiotic properties such as tolerance to low pH, simulated saliva (SS), simulated gastric juice (SGJ), simulated intestinal juice (SIJ), and bile salts as well as adhesion to HT-29 cells were also examined. Comprehensive evaluation was carried out by principal component analysis. Most cell-free excretory supernatants (CFS) showed α-glucosidase inhibition, ranging from 2.53% to 15.76%, but all cell-free extracts (CFE) had no α-glucosidase inhibitory activity. Strains ST-2, 1.1881, GS-3 and BLP12 showed strong ability to inhibit α-glucosidase. Strain ST-2 showed a 75.97% survival rate after 3 h of incubation at pH 2.0, and exhibited strong acid tolerance and adhesion to HT-29 cells; GS-3 showed a survival rate of 89.49% after the complete gastrointestinal transit and three strains differed in their survival rate. Principal component analysis (PCA) showed that overall, BLP12 displayed the best probiotic characteristics: its α-glucosidase inhibition rate was 15.10%; the survival rate was 71.04% after incubation at pH 2.0, 0.70% in the presence of bile salts (2.0%) for 24 h, and 88.27% after sequential digestion with SS, SGJ and SIJ; but the rate of adhesion to HT-29 cell was only 1.93%. In general, BLP12 displays strong adaptability to simulated environment. Strain BLP12 was identified as Lactobacillus plantarum by 16S rDNA sequencing. It could be used as a potential anti-diabetic probiotic strain for the development of functional foods.

Key words: α-glucosidase, probiotics, inhibition, probiotic properties, screening