Ecophysiological characterization of common food-borne fungi in relation to pH and water activity under various atmospheric compositions

The combined effects of pH, water activity (a_w), oxygen (O₂) and carbon dioxide (CO₂) levels on growth and sporulation of 10common food-borne fungi were studied. The use of a multivariate statistical method (PLS) for the analysis of data showed that the fungi could be grouped according to their physiological response to changes in the four tested factors. Carbon dioxide, a_w and pH were found to be the most significant factors describing differences and similarities among the fungi. Maximal inhibitory effect of elevated levels of CO₂ (5–25%) and decreased a_w (0·99–0·95) varied among the 10 species from 6 to 77% and from 52 to 100%, respectively. Sporulation of the fungi was sensitive to all tested factors. Furthermore, interaction of CO₂ and a_w displayed a significant effect on sporulation. It was shown that different fungal species associated with the same ecosystem responded similarly to changes in the tested factors. Thus, fungi which are not phylogenetically related may be physiologically related or show a common strategy of life.