Carboxymethylated β-glucan from Pichia kudriavzevii M16: structural characterization and multifunctional bioactivity

In this study, β-glucan (β-gluM16) was obtained from the cell wall of the probiotic yeast strain Pichia kudriavzevii M16 and chemically altered through carboxymethylation (CMβ-gluM16) to improve its solubility in water. Using gel permeation chromatography, the molecular weight of CMβ-gluM16 was found to be 232 kDa. Structural modification was confirmed by FTIR, with shifts linked to carboxymethyl functional groups. The 1,1-Diphenyl-2-Picrylhydrazyl (DPPH) radical, hydroxyl radical, and superoxide anion scavenging assays were used to measure antioxidant activity. DPPH activity reached 96% at 100 mg/mL, while hydroxyl radical scavenging reached 69.65% at the same concentration. At 100 mg/mL, the superoxide anion scavenging gradually reached 76%. CMβ-gluM16 effectively reduced biofilm formation in all tested pathogens. The strongest inhibition was observed for Escherichia coli (80% at 1 mg/mL), followed by Pseudomonas aeruginosa (71% at 0.5 mg/mL) and Staphylococcus aureus (67% at 10 mg/mL), depending on the applied concentration. Cytotoxicity tests showed that L929 fibroblast cells stayed alive at 500 µg/mL after 36 h (≥ 64% viability), demonstrating a nontoxic effect. However, at the same concentration and hour, HT-29 colorectal adenocarcinoma cell viability decreased in a dose- and time-dependent manner, reaching 60%. CMβ-gluM16 enhanced the adhesion of Lactiplantibacillus plantarum LP1 to intestinal epithelial cells and increased adhesion from 83% (probiotic alone) to 92% (synbiotic application) at 500 mg/mL. Cytokine levels (IL-1β, IL-6, IL-10, and TNF-α) were assessed for immunomodulatory activity; these levels changed with dose and application time. IL-1β ranged from 1341 to 3371 pg/mL, IL-6 from 169 to 280 pg/mL, IL-10 from 220 to 859 pg/mL, and TNF-α from 126 to 263 pg/mL across the tested conditions. This study is a preliminary investigation into the potential biotechnological applications of CMβ-gluM16, indicating its promise for further research.