Use of lactic acid bacteria for the control of the level of ochratoxin A in coffee beans. – ANGELICA

Green coffee beans are contaminated by molds of the genus Aspergillus, an ochratoxin (OTA) producer. Cereals, wine and coffee are the foods that contribute the most to OTA human ingestion: respectively 50, 13 and 10% in Europe. European legislation has set a maximum level for OTA in roasted coffee (5 µg.kg-1) and instant coffee (10 µg.kg-1) (Regulation of the European Commission, 1881/2006) but there is no limit yet for green coffee. According to FAO (2006) this norm on roasted coffee could lead an average rejection rate around 7% of shipments, and up to 18% in some cases.
When the ochratoxin A is produced on cherries coffee, there is a partial degradation during the roasting processes. It may induce serious health problems in humans, affecting the liver, been an immune suppressant, or acting like a potent teratogen and carcinogen (very long half-life).
Preliminary studies by our consortium have highlighted the inhibition of ochratoxinogenic fungi spore germination of by a lactic acid bacterial adhesion phenomenon around the spores.
The aim of the project is to propose a sustainable development alternative, a biocontrol process, through the application of lactic acid bacteria isolated from coffee pulp silage before and during the coffee cherries drying process, by the inhibition of germination, low growth and poor sporulation of the OTA producer fungus. We expect a deeper understanding of the inhibition mechanisms performed by lactic bacteria like preventing mold germination, decreasing sporulation, preventing the production of OTA. This will allow us to make recommendations on the use of lactic acid bacteria isolated from coffee plantations on the control of OTA production in green coffee beans.
In the first stage of the project we realize the isolation of lactic acid bacteria and ochratoxinogenic fungi from coffee cherries in Ivory Coast and Mexico (Robusta and Arabica variety) which will be genetically and biochemically identified. By selecting among the bacteria, a collection of microorganisms having different antifungal activities will be established. A second stage focuses on the study of inhibitory mechanisms of development of ochratoxinogenic fungi by lactic bacteria: the effect of antifungal metabolites produced during the lactic fermentation and especially the effect of the presence of bacterial cells on the germination of fungi spores and therefore on OTA production. In the third stage, we established the inoculum formulation, the implementation of a field distribution protocol and the final product evaluation.
A Next Generation Sequencing approach will allow the estimation of a and ß diversity as well as of microbial networks and inter-taxa relationships and the acquisition of a more integrated understanding of microbial community structure. A cytomorphological approach will be use to complement the study the inhibitory effect of lactic bacteria on ochratoxinogenic fungi germination, using scanning electron microscopy, transmission electron microscopy and confocal microscopy.
Collaborations between participants of the Franco-Mexican consortium involved in the project (UMR Imbe-IRD; Qualisud UMR-CIRAD; UAM Department of Biotechnology) have existed for 25 years, we have conducted several research programs focused on the coffee agroindustry, exploring the potential of lactic acid bacteria and on the issue of secondary metabolites of filamentous fungi. We have jointly trained many students, made many publications, organized several conferences.