Biocontrol activities of yeasts or lactic acid bacteria isolated from Robusta coffee against Aspergillus carbonarius growth and ochratoxin A production in vitro.

Biocontrol Agents (BCAs) can be an eco-friendly alternative to fungicides to reduce the contamination with mycotoxigenic fungi on coffee. In the present study, different strains of bacteria and yeasts were isolated from Ivorian Robusta coffee. Their ability to reduce fungal growth and Ochratoxin A (OTA) production during their confrontation against Aspergillus carbonarius was screened on solid media. Some strains were able to reduce growth and OTA production by 85 % and 90 % and were molecularly identified as two yeasts, Rhodosporidiobolus ruineniae and Meyerozyma caribbica. Subsequent tests on liquid media with A. carbonarius or solely with OTA revealed adhesion of R. ruineniae to the mycelium of A. carbonarius through Scanning Electron Microscopy, and an OTA adsorption efficiency of 50 %. For M. caribbica potential degradation of OTA after 24 h incubation was observed. Both yeasts could be potential BCAs good candidates for Ivorian Robusta coffee protection against A. carbonarius and OTA contamination.

Effect of the post-harvest processing procedure on OTA occurrence in artificially contaminated coffee.

The purpose of this work was to study how the type of post-harvest process, i.e. natural preparation known as the dry method, and two wet processes, affected contamination and toxin production up to the green coffee stage. Batches were contaminated with ochratoxin A or with OTA-producing strains of Aspergillus ochraceus and Aspergillus niger. For OTA artificial contamination, hulling or husk removal caused a reduction of OTA. When A. ochraceus was inoculated at low level, its growth was hampered by indigenous mould flora contrary that observed with A. niger. The fungal counts and OTA assays showed that the best way of limiting the development and impact of contaminating toxigenic flora "from the field" was the physical wet method.