Enhancing the Shelf Life and Stress Tolerance of the Biocontrol Agent Trichoderma harzianum by Encapsulation in Green Matrices of Nanocellulose and Carboxymethyl Cellulose

Abstract

Microbial inoculants offer a promising solution for reducing the environmental impact of agrochemicals while enhancing crop productivity within a bioeconomy framework. However, extending the shelf life and enhancing the stability of these beneficial microorganisms are crucial for making these biological solutions viable alternatives to chemical fertilizers and pesticides. In this study, we developed biobased encapsulation matrices using cellulose nanocrystals (CNC) and a composite of CNC and carboxymethyl cellulose (CNC:CMC) to encapsulate spores of the biocontrol fungus Trichoderma harzianum. Our findings revealed that encapsulation significantly increased the microorganism shelf life. After 1 year, approximately 10⁸ CFU/mL of the initial 10⁹ CFU/mL encapsulated spores remained viable, while nearly all free spores were no longer viable. Encapsulation also improved the microorganism resistance to stressful conditions, such as heat, UV radiation, and chemical fungicide exposure. Specifically, the CNC and CNC:CMC matrices maintained up to 4.7 × 10⁸ CFU/mL after fungicide exposure. Furthermore, encapsulation preserved the antagonistic activity of T. harzianum against the phytopathogen Fusarium solani for up to 1 year. These results demonstrate the potential of cellulose-based matrices for developing microbial inoculant formulations that support the shift toward more sustainable agricultural practices.