关键词: 植物乳植杆菌, 筛选, 鉴定, 胞外多糖, 条件优化

Abstract: Exopolysaccharide (EPS) from L. plantarum exhibited a variety of biological activities such as anti-tumor and anti-oxidation, but few studies on the synthesis of EPS in skim milk and its bioactivity has been reported. The aim of the present study is to screen L. plantarum with high EPS production capability in skim milk, which might facilitate the application of L. plantarum in dairy products. L. plantarum RT-6（CGMCC No. 26778）, with high capability to synthesize exopolysaccharide was isolated from homemade yogurt collected in Guilin, Guangxi Province, China, with the colony thread-drawing method. Among the tested L. plantarum strains, RT-6 exhibited, the highest EPS yield when cultivated in 10 % (w/w) reconstituted skim milk. The cultivation condition for L. plantarum RT-6 to synthesize EPS in skimmed milk was optimized via single factor tests and Response Surface Methodology. The optimized cultivation conditions for L. plantarum RT-6 to biosynthesize EPS were fermentation time of 39 h, fermentation temperature of 32℃, skimmed milk concentration of 101 mg/mL and mixture of essential amino acids, with individual amino acids of 1.488 mmol/L. Under the optimized conditions，the EPS synthesized by L. plantarum RT-6 in the fermented milk reached 241.1 mg /L, 2.6 times higher than that before optimization.

Key words: Lactiplantibacillus plantarum, screening, identification, exopolysaccharide, cultivation conditions optimization