Chitosan biocomposite as a carrier for curcumin, with a focus on its application in combating phytopathogenic bacteria.

In agriculture, polymeric particle formulations containing active ingredients have been developed to protect plants from pathogens, reducing health risks and environmental impact compared to traditional methods. Chitosan (Ch), a biodegradable, non-toxic, and readily available polymer, is utilized to produce nanoparticles with antimicrobial properties. Curcumin (CUR), a natural compound from turmeric, is known for its biocidal activity. Ch can be used in conjunction with CUR to enhance its activity against some agricultural phytopathogenic bacteria. The biocomposite, CUR-loaded Ch particles, were synthesized by ionotropic gelation methods with CUR encapsulation above 90 %. Characterization by FESEM, FT-IR, XRD and UV-Vis revealed quasi-spherical particles in Ch lamellar-like bundles with an average size of 200 nm. Antibacterial activity was evaluated against Pseudomonas syringae, Erwinia carotovora and Clavibacter michiganensis subsp. capsici. Ch did not show any statistically significant inhibitory effect compared to the CP and CP-CUR material against the bacterial species tested. P. syringae and C. michiganensis were significantly affected by CP-CUR particles, with >99 % of inhibitory effect using concentrations of 25 and 12.5 mg/mL. Test with Trichoderma atroviride, a beneficial fungus, showed that composites CP-CUR1 and CP-CUR2 did not affect conidia or sporulation. The results show that these biocomposites could be used as an alternative in the prevention of agricultural diseases caused by P. syringae and C. michiganensis without affecting beneficial microorganisms or products.