Impact of interacting climate change factors on growth and ochratoxin A production byAspergillus sectionCircumdati andNigri species on coffee

The objectives of this study were to evaluate the effect of interacting climate change (CC) factors (water stress [water activity, a w ; 0.99-0.90]); temperature [30, 35 °C]; and elevated CO 2 [400 and 1000 ppm] on (1) lag phases prior to growth, (2) growth and (3) ochratoxin A (OTA) production by species of Aspergillus sections Circumdati and Nigri on coffee-based media and stored coffee beans. The lag phases, prior to growth, of all strains/species were slightly increased as a w , temperature and CO 2 were modified. The interacting CC factors showed that most strains/species examined grew well at 30 °C and slightly less so at 35 °C except for Aspergillus niger (A 1911) which could tolerate the higher temperature. In addition, the interaction of elevated CO 2 (1000 ppm) + temperature (35 °C) increased OTA production when compared with 30 °C but only for strains of Aspergillus westerdijkiae (B2), Aspergillus ochraceus (ITAL 14) and Aspergillus steynii (CBS 112814). Most of the strains had optimum growth at 0.95 a w at 35 °C, while at 30 °C the optimum was at 0.98 a w . On stored coffee beans there was only a significant stimulation of OTA production by A. westerdijkiae strains in elevated CO 2 (1000) at 0.90 a w . These results suggest differential effects of CC factors on OTA production by species in the Sections Circumdati and Nigri in stored coffee and that for most species there is a reduction in toxin production.