Effects of water activity and culture age on the glycerol accumulation patterns of five fungi

Abstract

One non-xerophilic fungus, Penicillium digitatum, and four xerophilic fungi, Penicillium janczewskii, Eurotium chevalieri, Wallemia sebi and Polypaecilum pisce, were grown at six different water activities (a(w)) on media containing various concentrations of sodium chloride. Each species was sampled as soon as visible growth appeared and up to six times thereafter during various stages of the growth cycle. The fungal mycelium was extracted and assayed for glycerol using a specific enzymic method. At the highest a(w), 0.997, only small amounts of glycerol were present in the fungi. At lower a(w) values, glycerol concentrations rose rapidly at first, then declined as the cultures aged. There appeared to be a correlation between the amount of glycerol accumulated, and the complexity of the spore-bearing structures. Glycerol depletion appeared to be related to the formation of spores and their maturation.