Aspergillus fumigatus AR04 obeys Arrhenius' rule in cultivation temperature shifts from 30 to 40°C

Carbon dioxide release rate increased from 0.37 per hour to 0.69 per hour when batch cultures of the ascomycete Aspergillus fumigatus AR04 were compared at 30 and 40° C. This rate increase indicates an approximation to unlimited growth in a stirred vessel. Summary To set a benchmark in fungal growth rate, a differential analysis of prototrophic Aspergillus fumigatus AR04 with three ascomycetes applied in > 103 t year‐1 scale was performed, i.e. Ashbya gosspyii (riboflavin), Aspergillus niger (citric acid) and Aspergillus oryzae (food‐processing). While radial colony growth decreased 0.5‐fold when A. gossypii was cultivated at 40°C instead of 28°C, A. fumigatus AR04 responded with 1.7‐fold faster hyphal growth. A. niger and A. oryzae formed colonies at 40°C, but not at 43°C. Moreover, all A. fumigatus strains tested grew even at 49°C. In chemostat experiments, A. fumigatus AR04 reached steady state at a dilution rate of 0.7 h‐1 at 40°C, 120% more than reported for A. gossypii at 28°C. To study mycelial growth rates under unlimited conditions, carbon dioxide increase rates were calculated from concentrations detected online in the exhaust of batch fermentations for 3 h only. All rates calculated suggest that A. fumigatus AR04 approximates Arrhenius’ rule when comparing short cultivations at 30°C with those at 40°C. Linearization of the exponential phase and comparison of the slopes revealed an increase to 192% by the 10°C up‐shift.