Fermentation as a Functionalization Tool: Unlocking Agro-Food Residue Carbohydrates for Future Food Matrices.

Agro-food industrial residues (AFIRs) represent an underutilized source of recalcitrant carbohydrates, with food applications limited by poor hydration and sensory properties. Current physical or chemical processing strategies, however, are insufficient to achieve precise modulation, thereby creating a critical gap between residue availability and food applicability. This review reconceptualizes fermentation as a functionalization tool to transform these residues into high-value ingredients within a circular bioeconomy, specifically to address this gap. Their physicochemical targets can be categorized into carbohydrate biotransformation: structural deconstruction of insoluble fibers, molecular tailoring of soluble fibers, and nutritional modification of starches. Integrating process engineering with enzymatic mechanisms demonstrates the use of microbial systems for targeted modulation of rheology, porosity, and bioactivity. This review further examines how these functionalized carbohydrates can serve as texturizers in plant-based foods and as components in cellular agriculture, including alternative carbon sources and edible scaffolds for cultivated meat. While scalability and regulatory challenges persist, synthetic microbial consortia combined with precision bioprocessing enable strategic carbohydrate engineering that transforms agricultural side-streams into sustainable inputs for food production, thereby offering a practical route toward a circular bioeconomy.