Abstract
The effects of water activity on colony radial growth rate, specific growth rate, growth yield and blastospore production of Paecilomyces farinosus were studied. The compound (PEG 200) used to adjust water activity was not used for growth either when it was the sole carbon source in the medium or when the medium also contained glucose. Daily additions of water were made to cultures ‘compensated’ cultures) to compensate for evaporation; when this was not done the water activity of the medium decreased during incubation and a water activity at which growth ceased was eventually attained. A correlation was observed between the inhibitory effects of water activity on specific growth rate (µ) in ‘compensated’ shake flask cultures and on colony radial growth rate (K r) on solid medium. Thus, K r can be used to assess the effects of water activity on mould growth. Growth yield decreased linearly with decrease in water activity, and a decrease in water activity from 0·985 to 0·958 caused an approximately sixfold increase in the yield of blastospores per unit biomass dry weight.
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