Influence of ethyl acetate production and ploidy on the anti-mould activity of Pichia anomala

Abstract

A diploid and a haploid strain of Pichia anomala were tested for their biocontrol ability against the spoilage mould Penicillium roqueforti in glass tubes filled with grain at two water activities ( a w). At a w 0.98, the two yeast strains grew and inhibited mould growth equally well and showed similar patterns of ethyl acetate production, reaching maximum values of 10–14 μg ml −1 headspace. At a w 0.95, both growth and biocontrol performance of the haploid strain were reduced. Ethyl acetate formation was also substantially reduced, with maximum headspace concentrations of 4 μg ml −1. We conclude that ethyl acetate is a major component of the anti-mould activity. The inhibitory effect of ethyl acetate was confirmed in a bioassay where the pure compound reduced biomass production of P. roqueforti.