Effect of changes in Temperature Moisture and Carbon dioxide Concentrations on Aspergillus niger Growth and Ochratoxin Production in Agricultural Commodities

Abstract

Climate change impacts to various ecological systems, including contaminated microorganism in agricultural system. Aspergillus niger is an important problem of damaged stored agricultural products and can produce ochratoxin, which is classified as a human carcinogen and harmful for consumption. Therefore, impacts of changing temperature, mosisture and carbon dioxide (CO2) levels by A. niger were studied for advantageous information to predict growth and mycotoxin production. Mycelium growth of A. niger was tested by grown on yeast extract sucrose agar (YES agar) for 10 days. The optimum conditions for A. niger growth were 17-38oC, water activity (aw) 0.87-0.99 and CO2 300-1,000 mg/kg. Temperature at 25oC, CO2 600 mg/kg and aw 0.93, 0.95, 0.99 and 0.90 resulted to the highest growth rates of A. niger in 0.85, 0.79, 0.57 and 0.36 cm/day, respectively. Moreover, ochratoxin production was tested by Enzyme-Linked Immunosorbent Assay. Aspergillus niger at 27-36oC, CO2 800-1,000 mg/kg and aw 0.90-0.99 were produced ochratoxin higher than 2 μ μg/kg whereas at 30oC, CO2 600 mg/kg and aw 0.95, 0.93, 0.99 and 0.90 showed the highest ochratoxin production at 4.1, 3.5, 3.0 and 1.3 μμg/kg, respectively. This fungus could not be grown on YES agar with aw at 0.75-0.85. In addition, ochratoxin production in green coffee beans was tested in the different conditions. At 15oC, CO2 300, 600 and 1,000 mg/kg with 60% RH, A. niger produced low level of ochratoxin at the amount ranging from 0.8 to 1.8 μμg/kg in green coffee beans.