Screening and Probiotic Properties of Lactic Acid Bacteria Inhibiting α-Amylase and α-Glucosidase Activities in Camel Dairy Products

Objective: In this study, camel dairy products from the Altay region of Xinjiang were used to screen for excellent lactic acid bacteria with inhibitory activity against α-amylase and α-glucosidase. Methods: The strains were isolated and purified by dilution coating method, screened by DNS and pNPG methods for their inhibitory activity against α-amylase and α-glucosidase, and evaluated for their probiotic properties by acid tolerance, bile salt tolerance, tolerance to simulated gastrointestinal environment and bacterial inhibition assays. Results: A total of 34 strains were obtained from camel dairy products, six of which showed inhibitory activity against α-amylase and α-glucosidase. After morphological analysis and 16S rRNA molecular identification, four strains were identified as Lactobacillus plantarum and two as Lactobacillus paracasei. The inhibitory activity of six strains of Lactobacillus plantarum reached more than 50% against α-amylase, with one strain of Lactobacillus paracasei X34 showing the highest inhibition rate of 88.59% against α-amylase; the inhibitory activity against α-glucosidase ranged from 11% to 16%, with one strain of Lactobacillus plantarum X31 showing the highest inhibition rate of 15.43%. Six strains of Lactobacillus survived at different pH (1.0, 2.0, 3.0) and in different concentrations of bile salts (1, 2 and 3 g/L) in the medium. The survival rate of 6 strains of lactic acid bacteria in simulated gastric juice and intestinal juice was 83% and 90%, respectively. The scavenging rate of hydroxyl radicals and superoxide anion radicals exceeded 90%, among which X29 had the highest scavenging rate of 92.43% for hydroxyl radicals and the strongest scavenging rate of 94.04%. Six strains of lactic acid bacteria inhibited Escherichia coli, Salmonella and Staphylococcus aureus, with X31 having a maximum inhibition circle diameter of 19.63 mm against Escherichia coli, X23 having a maximum inhibition circle of 19.85 mm against Salmonella and X33 having a maximum inhibition circle diameter of 19.17 mm against Staphylococcus aureus. Conclusion: Six strains of lactic acid bacteria with potential hypoglycaemic activity, tolerance to strong acids, bile salts and gastrointestinal fluids, high antioxidant effect and inhibition of pathogenic bacteria were screened from camel dairy products to provide probiotic strains for later development of functional hypoglycaemic drinks.