Optimization and chemical modification of exopolysaccharides from lactic acid bacteria: multi-functional...

This study isolated two exopolysaccharide (EPS)-producing lactic acid bacteria (LAB), Lactobacillus plantarum Y-18 and Lactobacillus fermentum Y-29, from fermented bamboo shoots. Fermentation conditions were optimized using response surface methodology, increasing EPS yield by 2.78-fold and 2.41-fold, respectively. Crude EPS were fractionated by ion-exchange chromatography and subsequently modified via acetylation, sulfation, and carboxymethylation. All native and modified EPS fractions were characterized and evaluated for antioxidant activity (DPPH, hydroxyl radical scavenging, FRAP), and inhibition of α-glucosidase and xanthine oxidase. Their in vitro effects on the proliferation, migration, and invasion of A549 and LLC lung cancer cells were also assessed. Several modified fractions, notably acetylated and sulfated forms such as Y-18-0.1 M-Ac and Y-29-2 M-S, exhibited significantly higher functionality than their unmodified counterparts, with α-glucosidase inhibition reaching 90.29% and DPPH scavenging up to 99.88%. In cell-based assays, these derivatives also showed inhibitory effects on cancer cell migration and invasion at 1 mg/mL, although responses varied by cell line and EPS type.This research provided comparative data on the functional characteristics of LAB EPS from fermented bamboo shoots and their chemically modified forms, suggesting that both fermentation optimization and structural modification significantly influence EPS functionality, informing their potential application in food and related fields.