Investigation Of TP-Loaded CS-PAA Nanoparticles For Inhibiting Pathogens Fungi During The Postharvest Of Loquat Fruits

Chitosan is a polycationic polysaccharide with excellent properties including biocompatibility, biodegradability, non-toxicity, film-forming properties and antimicrobial activities. Nanoparticles based chitosan and other things to improve its antimicrobial activity has been becoming an research hotspot in recent years since the relatively low activities of chitosan limit its application as antimicrobial agents.In the present study, tea polyphenol was loaded in chitosan nanoparticles which prepared by ionic crosslinking between chitosan and ploy-aspartic acid. We investigated the ability of the teapolyphenols (TP-loaded nanoparticles on reduceing or preventing the spread of the pathogenic fungi which casused the decay of the loquat fruit(Eriobotrya japonica).(1) The effects of the weight ratio of CS to PAA, the reaction time and the concentration of tea polyphenols on the properties of the TP-loaded nanoparticles were studied. All three factors significantly influenced the particle size, the ξ-potential, and the entrapment efficiency of tea polyphenols. The best of the TP-loaded nanoparticles was obtained with the reaction time 75 min; a ratio of 4 CS:PAA (w/w),4; and a concentration of tea polyphenols 4 mg/mL. The mean particle size of the TP-loaded nanoparticles was 167.1 nm, and the zeta potential is 47.8 mV. The entrapment efficiency of the TP-loaded nanoparticles was 24.73%.(2) Pathogens from rotting loquat fruits were identificated by the assays of morphological and molecular biology. Six pathogens including Colletotrichum acutatum, Fusarium tricinctum, Alternaria alternate, Penicillium crustosum, Lasiodiplodia theobromae, Botryosphaeria dothidea were obtained.(3) The antifungal activity of the TP-loaded nanoparticles against the six pathogens fungi isolating from rotting loquat fruits was tested by mycelia radial growth rate and the spore germination inhibition rate. The results showed that the TP-loaded nanoparticles could effectively inhibit mycelia growth and spore germination of all the six pathogens fungi with a concentration effect. At the same concentration, the antifungal activity of the TP-loaded nanoparticles was better than the mixture of CS-TP-PAA, the mixture of CS-TP, CS and TP. Significant changes of microstructural of C. acutatum and F. tricinctum treated with TP-nanoparticles at a CS concentration of 6 mg/mL were obsvered by a scanning electron microscope (SEM).(4) TP-loaded nanoparticles of CS concentrations of 3 and 6 mg/mL could significantly reduce the natural incidence of disease of loquat fruits. Besides, the incidence of disease and the lesion area of apricots inoculated with C. acutatum and F. tricinctum were also reduced efficiently. The control efficacy of TP-loaded nanoparticles was better than the mixture of CS-TP-PAA.