Screening and characterization of lactic acid bacteria with antifungal activity against Penicillium digitatum on citrus

With the appearance of superbug and environment pollution, it is urgent to find a viable alternative to synthetic fungicide for controlling postharvest disease on citrus, especially for the control of the main pathogen Penicillium digitatum. The aim of this study was to isolate lactic acid bacteria (LAB) with antifungal activity against P. digitatum and investigate their antifungal characteristics. Sixty-eight LAB were isolated from surface of citrus fruit, leaves of citrus and peanuts, and soil in citrus orchards. Ten strains which belonging to three species (Lactobacillus sucicola, Weissella paramesenteroides, Pediococcus acidilactici) had strong inhibitory effects in vitro. After neutralization and catalase treatment, the cell-free supernatants of the L. sucicola JT03, W. paramesenteroides JT13 and P. acidilactici JY03 still exhibited partial inhibitory effect. However, their antifungal activities were partially lost after treated by proteinases. Moreover, they were especially sensitive to trypsin that antifungal activity of cell-free supernatants of the three LAB strains was totally lost. This result indicated that proteinaceous compounds might play an important role in antifungal activity for the LAB strains.