The aim of this study was the optimization of the fermentation conditions for the production of α-glucosidase inhibitors (AGIs) by Paenibacillus polymyxa BD3736 from skim milk. Using one-factor-at-a-time method, we investigated the effect of inoculum size, fermentation temperature, skim milk concentration and fermenation time on the activity of AGIs and and identified the main factors for optimization by response surface methodology with a three-factor and threelevel Box-Behnken design. The optimized fermentation conditions were determined as follows: fermentation temperature 31.5 ℃, inoculum amount 3.5% and 4 days of incubation time. The half maximal inhibitory concentration (IC50) of the fermentation supernatant obtained under these conditions against α-glucosidase was 30.5 mg/mL.

Based on their distinctive colonial morphology when co-cultured in MRS agar containing different carbon sources, two selective enumeration methods, namely difference method and chromatic aberration method, were established for Lactobacillus plantarum ST-Ⅲ and Leuconostoc mesenteroides BD1710 in co-culture. The reliability of these two methods could meet the requirements for selective counting of individual strains. The difference method was more suitable for research with high precision requirement owing to its higher average detection rate (97.2％ vs 95.4％ for ST-Ⅲ, 96.4％ vs 94.0％ for BD1710) compared with the chromatic aberration method, whilst the chromatic aberration method was superior in operability and cost and could provide factories with a fast way to determine viable bacterial counts in related products.

Researchers have been making significant efforts to reveal the relationships between the gut microbiota and diabetes mellitus. As a special bacterial population in the intestinal tract, probiotics have unique advantages in delaying and controlling the occurrence of diabetes. In this article, the mechanisms of action and superiorities of probiotics in the prevention and control of diabetes are reviewed and some future development trends are also predicted.