Biocontrole in vitro de bolores deteriorantes por toxina killer de levedura antagonista

Abstract

Brazil is one of the world leaders in fruit production, however, it faces post-harvest losses of up to 40%, caused by mechanical damages that result in contamination by deteriorating filamentous fungi. Biocontrol by yeast killer toxins has shown to be promissing in the combat of deteriorating microorganisms. The objective of this work was to evaluate the antifungal activity of the Hansenula wingei killer toxin on the fungi Aspergillus ochraceus and Penicillium expansum, by obtaining crude extract, followed by partial purification by ultrafiltration and in vitro antifungal assay, where the percentage inhibition of spore germination and mycelial development was determined. The crude extract inhibited the germination of A. ochraceus and P. expansum spores in 98.91% and 96.49%, respectively, as well as inhibition of the mycelial development of both fungi was greater than 78%. Ultrafiltration was not efficient in the partial purification of H. wingei killer toxin, since it was detected in the last fraction (<1 kDa). In addition, the antifungal effect of ultrafiltered killer toxin was lower than Crude extract. The susceptibility of both fungi tested showed a broad spectrum characteristic of the toxin, even in the ultrafiltered form, where inhibition of mycelial development remained greater than 70%. The killer toxin maintained its antifungal activity after the heat treatment of 90ºC for 30 min. From the cultivation of the antagonistic yeast, it is possible to obtain a natural antifungal compound with antifungal properties, aiming application in edible coatings for post-harvest fruits.