Effects of air discharge on surface charges and cell walls of Fusarium oxysporum

Air discharge showed significant inhibition on mycelial growth and spore germination of Fusarium oxysporum, one of the main spoilage fungi in post-harvest lotus roots which is an important economic aquatic vegetable in China. However, the antimicrobial mechanism of air discharge is not clear yet. In the present study, the effects of air discharge on F. oxysporum separated from post-harvest rotten lotus roots were characterized by analyzing surface charges, cell wall permeability, and changes in chitin and chitosan including surface morphology, functional groups, degree of deacetylation, crystallinity, and C/N ratio. After air discharge treatments, alkaline phosphatase leak assay revealed that cell wall permeability of F. oxysporum was magnified. What's more, zeta potentials of F. oxysporum increased and negative charges on cell surfaces decreased. The ordered and compact molecular arrangements of chitin and chitosan in cell walls of F. oxysporum were reduced. The deacetylation degree of chitin and chitosan increased, and the C/N ratios of chitin and chitosan decreased. It was concluded from these results that air discharge caused the transformation in structures of chitin and chitosan, resulting in the exposure of positively charged amino groups and decrease of negative charges on cell surfaces which brought damage to the structure and function of F. oxysporum's cell walls.