Nutrient Effects on Biocontrol of Penicillium roqueforti by Pichia anomala J121 during Airtight Storage of Wheat

Abstract

The biocontrol yeast Pichia anomala inhibits the growth of a variety of mold species. We examined the mechanism underlying the inhibition of the grain spoilage mold Penicillium roqueforti by the biocontrol yeast P. anomala J121 during airtight storage. The biocontrol effect in a model grain silo with moist wheat (water activity of 0.96) was enhanced when complex medium, maltose, or glucose was added. Supplementation with additional nitrogen or vitamin sources did not affect the biocontrol activity of the yeast. The addition of complex medium or glucose did not significantly influence the yeast cell numbers in the silos, whether in the presence or absence of P. roqueforti. Mold growth was not influenced by the addition of nutrients, if cultivated without yeast. The products of glucose metabolism, mainly ethanol and ethyl acetate, increased after glucose addition to P. anomala-inoculated treatments. Our results suggest that neither competition for nutrients nor production of a glucose-repressible cell wall lytic enzyme is the main mode of action of biocontrol by P. anomala in this grain system. Instead, the mold-inhibiting effect probably is due to the antifungal action of metabolites, most likely a combination of ethyl acetate and ethanol, derived from glycolysis. The discovery that sugar amendments enhance the biocontrol effect of P. anomala suggests novel ways of formulating biocontrol yeasts.

Antifungal Activity of Wickerhamomyces anomalus and Lactobacillus plantarum during Sourdough Fermentation: Identification of Novel Compounds and Long-Term Effect during Storage of Wheat Bread

“…Beyond economic losses, the growth of fungi in foods causes a decrease of the nutritional value and the synthesis of allergenic spores and hazardous mycotoxins (23). Traditionally, fungicides and chemical preservatives have been used to prevent fungal growth, but concerns about environmental pollution and consumer health, along with problems of microbial resistance, favor the demand for alternative methods of control (16).…”

“…In particular, P. anomala (Wickerhamomyces anomalus, according to the latest taxonomic system) was shown to inhibit the growth of fungi in airtight-stored cereal grains (32). The biocontrol effect in a model grain silo with moist wheat (water activity of 0.96) was attributed to the antifungal action of metabolites derived from glycolysis rather than to competition for nutrients or activity of cell wall lytic enzymes (16).…”

Growth Inhibition of Various Enterobacteriaceae Species by the Yeast Hansenula anomala during Storage of Moist Cereal Grain

“…With respect to the substantial inhibition of P. agglomerans and E. coli in our earlier study, where the moisture content of the grain was only 18% (14), it seems unlikely that killer proteins are the sole mechanism, if they play any role at all. It has been suggested that the volatile ester ethyl acetate is involved in antimold activity (6,8). An antibacterial activity of ethyl acetate has been shown (2), but to our knowledge, no further studies are available.…”

Lactic Acid Bacteria in Biopreservation and the Enhancement of the Functional Quality of Bread

“…Traditionally, chemical preservatives and fungicides are used to inhibit fungal growth but concerns about environmental pollution and consumer health, along with problems of microbial resistance, favour the demand for alternative methods in controlling the growth of fungi (Druvefors et al, 2005). The shelf life of bread has been reported to be extended when certain LAB strains were added to bread formulations (Muhialdin et al, 2011a;Ogunbanwo et al, 2008;Rizzello et al, 2010;Ryan et al, 2011) (Table 2).…”