Antifungal efficacy of thermostable I168L chitinase-ZnONPs encapsulated in alginate for postharvest fruit storage.

This study developed a novel biocontrol strategy using an alginate-encapsulated thermostable mutant chitinase (I168L) combined with zinc oxide nanoparticles (ZnONPs) to enhance enzyme stability and antifungal efficacy against Colletotrichum spp. DH31.1. The primary objective was to improve the enzyme's activity and extend its storage life. The Alg-I168L-ZnONPs complex and free I168L enzyme were synthesized and characterized, then evaluated for stability and antifungal activity after one-month storage at 4 °C. Results showed that encapsulation significantly enhanced the enzyme's thermal and storage stability, maintaining over 89 % relative activity even after 30 days at room temperature and over 90 % after one month at 4 °C. Furthermore, the Alg-I168L-ZnONPs complex consistently exhibited higher chitinase activity in phosphate buffer compared to water. Crucially, in postharvest trials on dragon fruits, the Alg-I168L-ZnONPs complex demonstrated superior antifungal efficacy, effectively preventing and treating Colletotrichum spp. DH31.1 infection at both 28 °C and 35 °C, with disease lesions being almost negligible. These findings highlight the significant potential of this stable and highly effective enzyme nanocomplex as an environmentally friendly alternative for preventing postharvest fungal diseases.