RESUMO
The pathogenic yeast strain LIAO causing the milky disease in the Chinese mitten crab belonged to one member of Metschnikowia bicuspidate which could grow well at different temperatures from 28 to 4 °C. It was also found that the pathogenic yeast strain LIAO could grow in the extracts of the muscle, gill, heart tissues, intestinal tracts of the healthy Chinese mitten crabs by using the reducing sugars, amino acids and other nutrients in them. Massoia lactone released from liamocins produced by Aureobasidium melanogenum had high anti-fungal activity against the pathogenic yeast strain LIAO and M. bicuspidate WCY isolated from the diseased marine crabs. The minimal inhibitory concentrations (MIC) and the minimal fungicidal concentration (MFC) in the liquid culture against the pathogenic yeast strain LIAO were 0.15 mg/mL and 0.34 mg/mL, respectively. Massoia lactone as a bio-surfactant could damage the cell membrane, even break the whole cells of the pathogenic yeast strain LIAO and cause cellular necrosis of the pathogenic yeast LIAO. Therefore, Massoia lactone could be used to effectively kill the pathogenic yeast strains and as an effectitve treatment for milky disease in the Chinese mitten crab.
