A Saccharomyces cerevisiae wine strain inhibits growth and decreases Ochratoxin A biosynthesis by Aspergillus carbonarius and Aspergillus ochraceus.

Loredana Cubaiu,Hamid Abbas,Alan D W Dobson,Marilena Budroni,Quirico Migheli

doi:10.3390/toxins4121468

Loredana Cubaiu, Hamid Abbas + Show 3 more

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https://doi.org/10.3390/toxins4121468

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Journal: Toxins	Publication Date: Dec 10, 2012
Citations: 72	License type: CC BY 3.0

Affiliation: University of Sassari, University College Cork

Abstract

The aim of this study was to select wine yeast strains as biocontrol agents against fungal contaminants responsible for the accumulation of ochratoxin A (OTA) in grape and wine and to dissect the mechanism of OTA detoxification by a Saccharomyces cerevisiae strain (DISAABA1182), which had previously been reported to reduce OTA in a synthetic must. All of the yeast strains tested displayed an ability to inhibit the growth of Aspergillus carbonarius both in vivo and in vitro and addition of culture filtrates from the tested isolates led to complete inhibition of OTA production. S. cerevisiae DISAABA1182 was selected and further tested for its capacity to inhibit OTA production and pks (polyketide synthase) transcription in A. carbonarius and Aspergillus ochraceus in vitro. In order to dissect the mechanism of OTA detoxification, each of these two fungi was co-cultured with living yeast cells exposed to yeast crude or to autoclaved supernatant: S. cerevisiae DISAABA1182 was found to inhibit mycelial growth and OTA production in both Aspergilli when co-cultured in the OTA-inducing YES medium. Moreover, a decrease in pks transcription was observed in the presence of living cells of S. cerevisiae DISAABA1182 or its supernatant, while no effects were observed on transcription of either of the constitutively expressed calmodulin and β-tubulin genes. This suggests that transcriptional regulation of OTA biosynthetic genes takes place during the interaction between DISAABA1182 and OTA-producing Aspergilli.

Highlights

Ochratoxin A (OTA) is a pentaketide mycotoxin which is produced by several fungal species from the Aspergillus and Penicillium genera
During the wine making process, OTA levels are known to decrease, an effect which is believed to be mediated by the activity of the resident microbial flora, of lactic acid bacteria and yeasts [10,16,17,18]
We report here for the first time on the biocontrol activity observed in the wine strain S. cerevisiae (DISAABA1182) that decreases growth, OTA production, and pks expression in two ochratoxigenic strains of A. carbonarius and A. ochraceus

Summary

Introduction

Ochratoxin A (OTA) is a pentaketide mycotoxin which is produced by several fungal species from the Aspergillus and Penicillium genera. OTA was first detected in wine by Zimmerli and Dick [2], where its presence is commonly ascribed to infection of wine grapes by Aspergillus carbonarius and some strains of Aspergilli section nigri. Maximum permitted levels of 2 μg·kg−1 have been established for OTA in wines and grape must-based drinks in the European Union (Commission regulation No 123/2005 amending Regulation No 446/2001). Infection by Aspergillus spp. immediately prior to or during harvesting, transportation and storage of grapes is considered to be a critical point in OTA contamination of wine [3]. Fungicide treatments at either the pre-harvest or post-harvest stage are not practical, due to the risk of contamination of the wine by toxic residues [4]

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