Bacterial fructan-metabolizing enzymes: modular architecture and biotechnological potential

Bacterial fructan-metabolizing enzymes exhibit substantial structural and mechanistic diversity to support their biotechnological uses. Recent findings on glycoside hydrolase (GH) families 32 and 68 emphasize the conserved catalytic triads, calcium-binding motifs, and domain architectures that define their reaction frameworks. Differences in carbohydrate-binding modules (CBMs), extended loops, and accessory domains contribute to variations in substrate affinity, polymer length, and the balance between polymerization and hydrolysis. Aggregated data shows that GH68 enzymes generally exhibit higher catalytic efficiencies on sucrose, while GH32 hydrolases display stronger preferences for inulin and short-chain fructooligosaccharides (ScFOS). In gut commensals, distinct fructan utilization operons provide the basis for substrate-driven cross-feeding interactions, with ScFOS typically exhibiting shorter fermentation times compared to high molecular-weight levans. Rapid progress in artificial intelligence for structural predictions, molecular dynamics simulations, and CRISPR-enabled pathway engineering now supports the rational redesign of fructan-active enzymes, enabling the generation of catalysts with customized product profiles, enhanced stability, or altered chain-length distributions. This review provides a comprehensive overview of bacterial fructan-metabolizing enzymes, integrating structural, biochemical, and ecological perspectives to establish a foundation for applying fructan-modifying enzymes to prebiotic production, food texturization, microbiome modulation, and emerging oral enzyme therapeutics.