An α-1,3-, α-1,4- and α-1,6-linked glucan synthesized by Limosilactobacillus reuteri PFAMO29 glucansucrase for enhancing curcumin dispersion and prebiotic potential

Bacterial glucansucrases (Glycoside Hydrolase family 70, GH70) represent a highly diverse enzyme family whose structural variability strongly influences the architecture and functionality of their glucan products. In this study, a glucansucrase, designated GTF-PM29, was cloned from the genomic DNA of Limosilactobacillus reuteri PFAMO29. Sequence analysis revealed 95.0% identity to GTF180, a well-characterized glucansucrase that synthesizes α-1,3/ α-1,6-linked glucans. Furthermore, negative-stain transmission electron microscopy revealed both compact and relaxed conformations of the full-length GTF-PM29, providing evidence of conformational flexibility within the GH70 family. Interestingly, product analysis demonstrated that GTF-PM29 produces glucan products containing α -1,3, α -1,4 and α -1,6 linkages. Kinetic characterization showed that the enzyme exhibited a lower transglycosylation rate relative to its hydrolytic activity. Notably, the GTF-PM29-derived glucan self-assembled into nano-colloids and demonstrated association with curcumin. Additionally, the oligosaccharides generated during polymerization stimulated the growth response of Lacticaseibacillus rhamnosus ATCC 7469, suggesting a preliminary, strain-dependent in vitro growth-stimulation response consistent with potential prebiotic activity. Collectively, these findings elucidate the structure-function relationships of GTF-PM29 and highlight its potential for producing functional, carbohydrate-based materials.