FERMENTATION-DERIVED RESIDUES AS METABOLITE RICH FUNCTIONAL BIOFERTILIZERS: MECHANISMS, SOIL HEALTH IMPACTS, AND CIRCULAR BIOECONOMY APPLICATIONS

Abstract

Fermentation-derived residues (FDRs) are gaining attention as metabolite-rich functional biofertilizers for sus tainable agriculture and circular bioeconomy applications. The conventional biofertilizers that rely primarily on the survival and colonization of live micro-organisms, FDRs function through stable bioactive metabolites includ ing organic acids, amino acids, peptides, phytohormones, exopolysaccharides, phenolics, enzymes, volatile or ganic compounds, and microbial biomass components. This review comprehensively examines the origins, bio chemical composition, mechanisms of action, soil health impacts, agronomic performance, formulation strategies, and sustainability implications of FDRs. Fermentation-derived metabolites enhance nutrient solubilization, rhizo sphere microbial interactions, soil enzymatic activity, plant growth promotion, and stress resilience while improv ing soil physical, chemical, and biological properties. Applications across cereals, millets, and horticultural crops demonstrate significant improvements in germination, nutrient uptake efficiency, biomass accumulation, yield stability, and soil fertility. The usage of FDRs contributes to waste valorization, reduction in chemical fertilizer dependency, carbon footprint mitigation, and climate-smart agriculture through circular nutrient recycling sys tems. Advanced formulation approaches such as encapsulation, controlled-release technologies, and hydrogel based stabilization improve shelf life and field performance. Despite their strong translational potential, challenges related to metabolite standardization, large-scale production, regulatory frameworks, and techno-economic feasi bility remain. Overall, FDRs represent a promising strategy for developing resilient, regenerative, and low-carbon agricultural systems.