Resilience ofAspergillus westerdijkiaeStrains to Interacting Climate-Related Abiotic Factors: Effects on Growth and Ochratoxin A Production on Coffee-Based Medium and in Stored Coffee

We examined the resilience of strains ofAspergillus westerdijkiaein terms of growth and ochratoxin A (OTA) production in relation to: (a) two-way interacting climate-related abiotic factors of water activity (a(w), 0.99-0.90) x temperature (25-37 degrees C) on green coffee and roasted coffee-based media; (b) three-way climate-related abiotic factors (temperature, 30 vs. 35 degrees C; water stress, 0.98-0.90 a(w); CO2, 400 vs. 1000 ppm) on growth and OTA production on a 6% green coffee extract-based matrix; and (c) the effect of three-way climate-related abiotic factors on OTA production in stored green coffee beans. Four strains ofA. westerdijkiaegrew equally well on green or roasted coffee-based media with optimum 0.98 a(w)and 25-30 degrees C. Growth was significantly slower on roasted than green coffee-based media at 35 degrees C, regardless of a(w)level. Interestingly, on green coffee-based media OTA production was optimum at 0.98-0.95 a(w)and 30 degrees C. However, on roasted coffee-based media very little OTA was produced. Three-way climate-related abiotic factors were examined on two of these strains. These interacting factors significantly reduced growth of theA. westerdijkiaestrains, especially at 35 degrees C x 1000 ppm CO(2)and all a(w)levels when compared to 30 degrees C. At 35 degrees C x 1000 ppm CO(2)there was some stimulation of OTA production by the twoA. westerdijkiaestrains, especially under water stress. In stored green coffee beans optimum OTA was produced at 0.95-0.97 a(w)/30 degrees C. In elevated CO(2)and 35 degrees C, OTA production was stimulated at 0.95-0.90 a(w).