Enhanced antifungal activity of chitosan-coated cinnamaldehyde-immobilized thermostable cellulose from spent mushroom substrate against phytopathogenic fungi

Phytopathogenic fungi jeopardize global food security, fueling reliance on synthetic fungicides with severe ecological impacts. Avoiding these chemicals risks a food crisis, highlighting the need for sustainable alternatives. Cinnamaldehyde (CA) is a natural but chemically unstable fungicide, hence requiring stabilization through effective immobilization. This study presents a biodegradable and sustainable alternative to synthetic anchoring materials: spent-mushroom-substrate-derived cellulose. CA immobilized cellulose was coated with chitosan which further enhanced the antifungal potential and contributed to slow release of CA. Cellulose extraction and CA encapsulation were successfully confirmed through analytical characterization. The resulting product (CeCACs) proved a promising fungicide, inhibiting key phytopathogenic fungi Fusarium oxysporum, Aspergillus flavus, and Aspergillus niger at 46. 8 μg/mL and Fusarium solani at 93.7 μg/mL concentration. The obtained minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC) values were significantly lower than commercial fungicide, tebuconazole (TB). The fungicidal mechanism involved reactive oxygen species accumulation, plasma membrane damage, and apoptosis-like cell death. Using CeCACs as a peanut seed coating enhanced seedling growth and enriched beneficial endophytic bacteria, while CeCACs fumigation effectively eradicated Fusarium oxysporum from peanut and passion fruit surfaces. This study emphasizes converting agri-waste into a green fungicide, supporting sustainable and regenerative agriculture.