Simulation of coffee beans contamination by Aspergillus species under different environmental conditions and the biocontrol effect by Saccharomyces cerevisiae

Abstract

Temperature and water activity (aw) are both responsible for the growth and production of ochratoxin A (OTA) by Aspergillus species in coffee. To prove this, we tested the effect of environmental factors combined with green coffee composition on the risk of OTA production as well as the efficiency of using Saccharomyces cerevisiae to control the growth of Aspergillus ochraceus, A. westerdijkiae, and A. carbonarius, OTA production and biosynthetic genes expression regulation levels. The results showed a higher growth rate and OTA risk index (ORI) for the three fungal isolates at 21 °C and 0.98 aw. Temperature affected the growth of the isolates negatively. The ORI was influenced synergistically by aw and antagonistically by temperature. The best condition for biological control by using S. cerevisiae CCMA 0159 was observed at 28 °C and 0.99 aw. Temperature and aw directly affected OTA production and biological control efficiency, but at different values. A. carbonarius CCDCA 10507 showed better growth and a greater risk of contamination in coffee. S. cerevisiae CCMA 0159 significantly reduced the risk of contamination by Aspergillus using substrate competition as strategies, acting on down regulation of OTA's biosynthetic gene expression, including hal and p450.