A new chitosan sub-micron and encapsulated Iturin A with enhanced antifungal activity against Ceratocystis fimbriata and Rhizopus strolonifer.

Abstract Iturin A is a natural antifungal agent that is widely used in the agriculture and food industries. In the present study, a new modified chitosan sub-micron, succinaldehydic acid (SAC) - chitosan (CS) system was synthesised by microwave irradiation and then as a carrier for capsulation of Iturin A (SAC-CS-IA). The structures of SAC-CS and SAC-CS-IA were characterised by SEM, NMR and FTIR. The size distribution suggested that the average size of SAC-CS and SAC-CS-IA was from 1.5 to 2.5 μm. An encapsulation efficiency of 92.02% under an adaptive pH (pH = 5) and time (5.5 h) was used. The study of release kinetics shows that about 80% of Iturin A was released in 25 days. An antifungal activity assay indicated that SAC-CS-IA exhibited higher antifungal activity against Ceratocystis fimbriata and Rhizopus strolonifer with 75.05 ± 3.24% and 80.54 ± 2.65%, respectively. The results indicate that the SAC-CS can improve the stability of IA on heat and pH with a wide range and tolerance most of enzymes. Actual tuber storage suggested that SAC-CS-IA can significantly inhibit pathogen fungal infection and reduce toxin product. Meanwhile, SAC-CS-IA could retain the water, starch, and soluble sugar contents. Low residue assay indicated that SAC-CS-IA could be used as an antifungal and anti-rotting agent in agriculture and food applications.