关键词: 植物乳植杆菌；筛选；鉴定；胞外多糖；条件优化

Abstract: 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.

Key words: Lactiplantibacillus plantarum; screening; identification; exopolysaccharide; culture conditions optimization