New Isolated Metschnikowia pulcherrima Strains from Apples for Postharvest Biocontrol of Penicillium expansum and Patulin Accumulation.

Laura Settier-Ramírez,Gracia López-Carballo,Pilar Hernández-Muñoz,Sabine Schorr-Galindo,Caroline Strub,Angélique Fontana

doi:10.3390/toxins13060397

Abstract

Wild yeasts isolated from the surface of apples were screened for antagonistic activity against Penicillium expansum, the main producer of the mycotoxin patulin. Three antagonistic yeasts (Y33, Y29 and Y24) from a total of 90 were found to inhibit P. expansum growth. Identification by ITS region sequence and characterization showed that three selected isolates of yeast should be different strains of Metschnikowia pulcherrima. Several concentrations of the selected yeasts were used to study their in vitro antifungal effectivity against P. expansum on Petri dishes (plates with 63.6 cm2 surface) whereas their potential activity on patulin reduction was studied in liquid medium. Finally, the BCA that had the best in vitro antifungal capacity against P. and the best patulin degradation capacity was selected to be assessed directly on apples. All the selected strains demonstrated antifungal activity in vitro but the most efficient was the strain Y29. Isolated strains were able to reduce patulin content in liquid medium, Y29 being the only strain that completely reduced patulin levels within 120 h. The application of Y29 as biocontrol agent on the surface of apples inoculated with P. expansum, inhibited fungal growth and patulin production during storage. Therefore, the results shown that this yeast strain could be used for the reduction of P. expansum and its mycotoxin in apples or apple-based products by adapting the procedure application.

Highlights

P. expansum infect a wide range of food products including pome and stone fruits which are the primary targets for this toxigenic fungus
Ninety yeast strains were isolated from the skin of apples as soon as they were harvested in the orchard
The results of this study provide evidence of the high potential of M. pulcherrima isolated strains from apples as biocontrol agent that reduced P. expansum incidence and have the ability to biodegrade patulin into less toxic metabolites

Summary

Introduction

More than 30% of fruit and vegetables produced worldwide is discarded every year [1] These losses occur throughout all the supply chain from cultivation to household consumption most of them happen during the postharvest stage, processing, transportation or storage. P. expansum infect a wide range of food products including pome and stone fruits (such as apples, pears, cherries, or peaches) which are the primary targets for this toxigenic fungus. It has been isolated worldwide from vegetables [5], grains and even in dairy products [6] and sea food [7,8]. This common fungus is responsible for the blue mold decay of fruits (blue mold rot disease called soft rot), where damaged and bruised fruits soften and brown [9]

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