Fermentation-based valorization of agro-industrial cereal wastes and by-products

Background: Agro-industrial cereal processing generates large volumes of nutrient-rich by-products such as bran, husks, and spent grains that remain underutilized. These residues contain proteins, fibers, phenolics, and micronutrients that can be efficiently recovered through sustainable bioprocessing. Scope and approach: This review synthesizes recent advances in fermentation-based valorization of cereal waste and by-products, focusing on solid-state and submerged systems involving bacteria, fungi, and yeasts. It uniquely integrates microbial fermentation strategies with sustainability and examines their compositional enhancement, bioactive compound release, and antinutrient reduction. It also highlights emerging developments such as AI- and ML-assisted fermentation process optimization, which aligns cereal waste valorization with SDGs and next-generation bioprocess design. Key findings and conclusions: Fermentation enhances protein digestibility, phenolic bioaccessibility, and prebiotic oligosaccharide yield, while reducing phytic acid, tannins, and mycotoxins. Pretreatment, followed by fermentation, enhances nutrient release and improves the functional properties of bran, husks, and spent grains. These improvements support industrial applications range from functional foods and nutraceuticals to biofuels and bioplastics. However, scalability remains constrained by substrate variability, process optimization challanges, and economic feasibility. Integrating multi-omics datasets, adaptive biorefinery models, and AI-based control systems could accelerate the transition toward sustainable, data-driven cereal waste valorization, establishing fermentation as a cornerstone technology linking waste reduction, functional food innovation, and the global sustainability agenda.