Improved exopolysaccharide production by Lactiplantibacillus plantarum Z-1 under hydrogen peroxide stress and its physicochemical properties

Abstract

In this study, a strain with good exopolysaccharide (EPS)-producing ability was isolated from the fermented Benincasa hispida and identified as Lactiplantibacillus plantarum Z-1. Its EPS production was further improved by H2O2 stress under optimized culture conditions, increasing from 180 ± 0.45 mg/L to 409.52 ± 2.16 mg/L. Purification of EPS with DEAE-52 and subsequent Sephadex G-100 column chromatography provided three fractions, namely, EPS-0, EPS-1 and EPS-3, respectively. The molecular weight of EPS, EPS-0, EPS-1 and EPS-3 were 85.4, 25.7, 131.88 and 93.2 kDa, respectively. EPS, EPS-1 and EPS-3 were mainly composed of glucose, rhamnose, arabinose and galactose with molar ratios of 1:0.544:0.211:0.281, 1:1.279:0.807:0.704, and 1:1.459:0.759:0.75, respectively, along with small proportions of fucose, mannose and xylose. EPS-0 was composed of glucose, arabinose, galactose and xylose, with molar ratios of 1:0.618:0.206:0.275. The structural analysis indicated that EPS-3 was mainly consisted of (1,2,4)-β-Rhap, (1,2,3)-β-Araf, (1,4)-β-Galp, T-α-Glcp units. The three purified fractions showed typical characteristics of non-Newtonian fluids and good viscoelasticity. Congo red test revealed that irregular triple-helical conformation existed in EPS and EPS-3. These physicochemical properties of EPSs make them a potential candidate for the use as a health-beneficial food additive in the food processing industry.