Partial characterization and antioxidant activity of exopolysaccharides produced by Lactobacillus plantarum CNPC003

In this study, the production of exopolysaccharides (EPS) by three strains of Lactobacillus was investigated, and Lactobacillus plantarum CNPC003 was identified as the largest producer. EPS production was higher (568.4 mg/L) in MRS medium added with fructooligosaccharide (FOS) than in control MRS medium containing glucose (378 mg/L). Carbohydrate and protein content in EPS FOS were 36.95 ± 0.24 g/100g and 0.68 ± 0.08 g/100g, respectively, while EPS GLU showed 42.48 ± 0.04 g/100g carbohydrate and 0.87 ± 0.05 g/100g protein. Infrared spectroscopy analysis confirmed the polysaccharide structure of the two EPS of L. plantarum CNPC003, and thermal analyses demonstrated the suitable stability of these polymers under high temperatures that can withstand temperatures up to 210 °C. Composition of monosaccharides and heteronuclear single quantum coherence (HSQC) spectroscopy showed that these EPS are heteropolysaccharides, mainly constituted of mannose and glucose, with small amounts of galactose and it is suggested that both EPS FOS and EPS GLU are constituted of a branched glucomannan. EPS samples also showed significant in vitro antioxidant capacity, especially EPS FOS, with ABTS radical scavenging activity of 90.88 ± 0.80% at a concentration of 8 mg/mL. These results support its use as a natural antioxidant in the food industry.