Impact of temperature on growth and metabolic efficiency of Penicillium roqueforti– correlations between produced heat, ergosterol content and biomass

The influence of temperature on the growth of the mould Penicillium roqueforti growing on malt extract agar was studied by correlating the produced heat (measured by isothermal calorimetry), ergosterol content (quantified by GC-MS/MS) and biomass of the mould at 10, 15, 20, 25 and 30°C. The results were analysed with a simple metabolic model from which the metabolic efficiency was calculated. The results show that the impact of temperature on growth rate and metabolic efficiency are different: although the mould fungus had the highest growth rate (in terms of thermal power, which was continuously measured) at 25°C, the substrate carbon conversion efficiency (biomass production divided by substrate consumption, both counted as moles carbon) was the highest at 20°C. The temperature of the most rapid growth did not therefore equal the temperature of the most efficient growth.