Research Article
Claude P Champagne, Tony Savar
Abstract
A total of 11 killer yeasts were studied with the aim of finding a yeast strain that could be added to a lactic starter for the production of fermented vegetables. Growth and production of toxins by the killer yeasts were first analyzed in Yeast and Mold broth (YM) at two pH levels and in the presence or absence of organic acids. All killer yeasts were sensitive to those acids in acidified media (pH 3.5). Two of them were selected for further analysis in a vegetable juice medium (VJM). Killer activities against two target yeasts (Saccharomyces unisporus Y-42 and Saccharomyces bayanus Y-43) previously isolated from spoiled fermented vegetables were then determined using well diffusion assay. Killer yeasts were grown on VJM using variable conditions; 3 temperatures, 5 salt concentrations and 5 pH levels. Fungicidal properties and synthesis of killer factors are strongly dependant on growth conditions as well as on the killer yeast strain used. Production of killer toxins by Hansenula anomala ATCC 36903 was optimal when incubated at 20°C to 30°C in VJM having a pH range between 3.5 to 4.5 and supplemented with sodium chloride at concentration of 2 to 4%. Those results suggest that Hansenula anomala ATCC 36903 could be a suitable addition to a lactic starter to help control secondary fermentation in fermented vegetables.