Adhesion properties and surface hydrophobicity of Pichia manshurica strains isolated from organic wines

This study focuses on the determination of microorganisms present in spoiled bottled wines of a Montepulciano d'Abruzzo organic wine and establish the source of this contamination. The yeasts belonging to Pichia manshurica species were genetically characterized by PFGE, and tested for their resistance to potassium metabisulphite and some cleaning agents determining the minimum inhibitory concentrations (MIC) and biofilms formation in YPD and pasteurized must. PFGE analysis revealed the presence of 2 karyotypes with 3 or 4 bands. The most effective detergent was the alkaline powder one, while the less active was the peracetic acid based sanitizing agent. MIC values for potassium metabisulphite ranged from 100 to 200 ppm. Regarding adhesion properties all strains showed a certain degree of hydrophobicity, as revealed by the affinity for hexadecane and decane, and were able to form biofilm on polystyrene plates: sessile cells reached values of 7.85 log cfu/mL in YPD and 6.95 log cfu/mL in must. All strains formed MAT structures and an air-liquid biofilm. This paper shows that organic wine can be subjected to contamination driven by not very resistant strains. Moreover, membrane filters used for wine sterilization act as a vector of wine contamination.