Effect of Temperature, Water Activity, and pH on Growth and Production of Ochratoxin A by Aspergillus niger and Aspergillus carbonarius from Brazilian Grapes

Abstract

The growth of ochratoxigenic fungus and the presence of ochratoxin A (OTA) in grapes and their derivatives can be caused by a wide range of physical, chemical, and biological factors. The determination of interactions between these factors and fungal species from different climatic regions is important in designing models for minimizing the risk of OTA in wine and grape juice. This study evaluated the influence of temperature, water activity (aw), and pH on the development and production of OTA in a semisynthetic grape culture medium by Aspergillus carbonarius and Aspergillus niger strains. To analyze the growth conditions and production of OTA, an experimental design was conducted using response surface methodology as a tool to assess the effects of these abiotic variables on fungal behavior. A. carbonarius showed the highest growth at temperatures from 20 to 33°C, aw between 0.95 and 0.98, and pH levels between 5 and 6.5. Similarly, for A. niger, temperatures between 24 and 37°C, aw greater than 0.95, and pH levels between 4 and 6.5 were optimal. The greatest toxin concentrations for A. carbonarius and A. niger (10 μg/g and 7.0 μg/g, respectively) were found at 15°C, aw 0.99, and pH 5.35. The lowest pH was found to contribute to greater OTA production. These results show that the evaluated fungi are able to grow and produce OTA in a wide range of temperature, aw, and pH. However, the optimal conditions for toxin production are generally different from those optimal for fungal growth. The knowledge of optimal conditions for fungal growth and production of OTA, and of the stages of cultivation in which these conditions are optimal, allows a more precise assessment of the potential risk to health from consumption of products derived from grapes.

Effect of pH and temperature in production of mycotoxins and antibiotics by phytopathogenic moulds for Persian lime (Citrus latifolia T.) in a complex lime pericarp-base medium

“…The effect of pH and temperature in mycotoxin and antibiotics production for all moulds in this study was similar to those obtained by Passamani et al (2014). They evaluated the influence of temperature, pH and a w on the growth and mycotoxin production on A. carbonarius and A. niger on a grape-based medium, finding that optimal values of A. carbonarius ranged from 20 to 33° C and pH levels from 5 to 6.5 (0.96 -0.98 a w ).…”

“…Our results showed that moulds analyzed synthesize more than one mycotoxin mainly at 20° C, whereas A. niger synthesizes FB 1 at 25° C. This indicates that the risk of contamination increases on cool and temperate citrus production zones (Passamani et al, 2014).…”

Ochratoxin A in black pepper, white pepper and clove sold in Yaoundé (Cameroon) markets: contamination levels and consumers’ practices increasing health risk

“…Another critical consumers' practice identified which may increase the risk of mycotoxin contamination of spices is during storage. In fact, storage at room temperature in tropical climates and for prolonged periods is suitable for the growth of ochratoxinogenic fungi and subsequent OTA production (Esteban et al 2004;Pardo et al 2004;Ribeiro et al 2006;Passamani et al 2014). Besides, OTA is a thermally stable compound up to 180°C (Raters and Matissek 2008), which is slightly soluble in water (El Khoury et al, 2010).…”

<b>Use of wild yeasts as a biocontrol agent against toxigenic fungi and OTA production

“…a w may be one of the most important factors influencing the growth, germination and establishment of fungi in substrates rich in nutrients (Bouras, Kim, & Strelkov, 2009;Passamani et al, 2014). The fungal strains used as treatment control for OTA evaluation did not produce OTA in lower a w , and in a general way, the best environmental condition for OTA production is the same for growth (Bellí, Ramos, Coronas, Sanchis, & Marín, 2005).…”