Killer toxin of Kluyveromyces phaffii DBVPG 6076 as a biopreservative agent to control apiculate wine Yeasts.

The use of Kluyveromyces phaffii DBVPG 6076 killer toxin against apiculate wine yeasts has been investigated. The killer toxin of K. phaffii DBVPG 6076 showed extensive anti-Hanseniaspora activity against strains isolated from grape samples. The proteinaceous killer toxin was found to be active in the pH range of 3 to 5 and at temperatures lower than 40 degrees C. These biochemical properties would allow the use of K. phaffii killer toxin in wine making. Fungicidal or fungistatic effects depend on the toxin concentration. Toxin concentrations present in the supernatant during optimal conditions of production (14.3 arbitrary units) exerted a fungicidal effect on a sensitive strain of Hanseniaspora uvarum. At subcritical concentrations (fungistatic effect) the saturation kinetics observed with the increased ratio of killer toxin to H. uvarum cells suggest the presence of a toxin receptor. The inhibitory activity exerted by the killer toxin present in grape juice was comparable to that of sulfur dioxide. The findings presented suggest that the K. phaffii DBVPG 6076 killer toxin has potential as a biopreservative agent in wine making.