Effect of solute and matric potential on growth rate of fungal species isolated from cheese

The effect of water potential (Ψw) on the growth of 15 fungal species isolated from cheeses was analysed. The species, identified mainly by analysis of DNA sequences, belonged to genera Penicillium, Geotrichum, Mucor, Aspergillus, Microascus and Talaromyces. Particularly, the effect of matric potential (Ψm), and ionic (NaCl) and non-ionic (glycerol) solute potentials (Ψs) on growth rate was studied. The response of strains was highly dependent on the type of Ψw. For Ψs, clear profiles for optimal, permissive and marginal conditions for growth were obtained, and differences in growth rate were achieved comparing NaCl and glycerol for most of the species. Conversely, a sustained growth was obtained for Ψm in all the strains, with the exception of Aspergillus pseudoglaucus, whose growth increased proportionally to the level of water stress. Our results might help to understand the impact of environmental factors on the ecophysiology and dynamics of fungal populations associated to cheeses.