Biocontrol activity of Starmerella bacillaris yeast against blue mold disease on apple fruit and its effect on cider fermentation

The reduction of chemical fungicides in agriculture has led to the use of microorganisms as biocontrol agents. Starmerella bacillaris is a non-Saccharomyces yeast associated with overripe and botrytized grape berries microbiota. Its use has been proposed for wine fermentation because of yeast fructophilic character and high glycerol production. Recently, S. bacillaris has been demonstrated to possess antifungal activity against Botrytis cinerea on the grape. Penicillium expansum is the pathogen responsible for the blue mold rot, the most important postharvest disease of apples. These fruits are the raw material of the cider, an alcoholic beverage commonly produced using S. cerevisiae starter cultures. In this study 14 S. bacillaris strains have been studied to evaluate their postharvest antifungal activity against P. expansum on apples. Moreover, the fermentation performances in apple juice of these non-Saccharomyces strains were tested, both in single-strain fermentation and in sequential fermentation, together with S. cerevisiae. Four S. bacillaris strains, able to significantly decrease blue mold rot symptoms and to increase glycerol content during fermentation have been selected to improve apple and cider quality.