Effect of environmental factors on tenuazonic acid production by Alternaria alternata on soybean-based media

OVIEDO M.S.; RAMIREZ M.L.; BARROS G.G.; CHULZE S.N.

JOURNAL OF APPLIED MICROBIOLOGY

Blackwell

Año: 2009 vol. 107 p. 1186 - 1192

1364-5072

Aims: To determine the effects of water activity (aW; 0Æ995?0Æ90), temperature (5, 18, 25 and 30C), time of incubation (7?35 days) and their interactions on tenuazonic acid (TA) production on 2% soybean-based agar by two Alternaria alternata strains isolated from soybean in Argentina. Methods and Results: TA production by two isolates of A. alternata was examined under interacting conditions of aW, temperature and time of incubation on 2% soybean-based agar. Maximum TA production was obtained for both strains at 0Æ98 aW, but at 30 and 25C for the strains for RC 21and RC 39, respectively. The toxin concentration varied considerably depending on aW, temperature, incubation time and strain interactions. TA was produced over the temperature range from 5 to 30C and aW range from 0Æ92 to 0Æ995, however at 5 and 18C little TA was produced at aW below 0Æ94. Contour maps were developed from these data to identify areas where conditions indicate a significant risk for TA accumulation. Conclusions: The optimum and marginal conditions for TA production by A. alternata on soybean-based agar were identified. The results indicated that TA production by A. alternata is favoured by different temperatures in different strains. Significance and Impact of the Study: Data obtained provide very useful information for predicting the possible risk factors for TA contamination of soybean as the aW and temperature range used in this study simulate those occurringduring grain ripening. The knowledge of TA production under marginal or sub-optimal temperature and aW conditions for growth are relevant as improper storage conditions accompanied by elevated temperature and moisture content in the grain can favour further mycotoxin production and lead toreduction in grain quality.