Exopolysaccharides (EPS) from Lactiplantibacillus plantarum have been found to possess a variety of biological activities such as antitumor and antioxidant, but few studies on the synthesis of EPS by L. plantarum in skim milk have been reported. The aim of the present study was to screen L. plantarum with high EPS production capability in skim milk, which will be great significance to the application of L. plantarum in dairy products. L. plantarum RT-6 (CGMCC No. 26778), with a high capability of producing EPS, was isolated from homemade yogurt collected in Guilin, Guangxi, China by the colony thread-drawing method. Its EPS producing capability was compared with that of other L. plantarum strains. The culture conditions for EPS production by L. plantarum RT-6 were optimized using one-factor-at-a-time (OFAT) method and response surface methodology (RSM). It was found that among all tested L. plantarum strains, RT-6 exhibited the highest EPS yield when cultured in reconstituted skim milk, whereas most other strains grew slowly or even could not grow. The optimal culture conditions were determined as 39 h, 32 ℃, 101 mg/mL and 1.488 mmol/L for fermentation time, fermentation temperature, skim milk concentration and concentration of mixed essential amino acids, respectively. Under the optimized conditions, the yield of EPS was 241.1 mg/L, 2.6 times higher than that before optimization.

The in vitro hypoglycemic effect of the supernatant of fermented milk with Paenibacillus bovis BD3526 (CGMCC No.8333) was evaluated, and the supernatant was used to prepare hypoglycemic beverage, whey powder and milk powder. The storage stability of the hypoglycemic products was investigated. The results showed that the supernatant had strong (which inhibited about 90% of α-glucosidase activity) and stable hypoglycemic activity in vitro. The beverage, whey powder and milk powder inhibited 57%, 48% and 37% of α-glucosidase in vitro, and their microbial properties conformed to the national standard requirements. After storage for six months at different temperatures (8, 25 and 60 ℃), their hypoglycemic activity remained substantially unchanged, and their microbial indexes were significantly superior to those of the control group.

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.

Milk fermented by Leuconostoc mesenteroides Leuco4 or yoghurt starter culture YO-MIX465 (consisting of Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophilus) and their mixture at a mass ratio of 1:4 were evaluated for viscosity, syneresis, texture properties and sensory quality. Compared with YO-MIX465-fermented milk, fermented milk containing Leuconostoc mesenteroides Leuco4 had better water-holding capacity and viscosity and desired viscosity, taste and stability and could meet the requirement of clean-label products due to not containing any food additives.