%0 Journal Article %A Gallmetzer, Martin %A Burgstaller, Wolfgang %T Efflux of organic acids in Penicillium simplicissimum is an energy-spilling process, adjusting the catabolic carbon flow to the nutrient supply and the activity of catabolic pathways %D 2002 %J Microbiology, %V 148 %N 4 %P 1143-1149 %@ 1465-2080 %R https://doi.org/10.1099/00221287-148-4-1143 %K continuous culture %K YO2X, biomass yield on oxygen (g mol−1) %K μ, specific growth rate (h−1) %K qCO2, rate of carbon dioxide production (mmol g−1 h−1) %K chemostat %K TCA, tricarboxylic acid %K overflow metabolism %K biomass yield %K nutrient limitation %K SHAM, salicylhydroxamic acid %K mCO2X, maintenance coefficient for carbon dioxide (mol g−1 h−1) %K qGlc, rate of glucose consumption (mmol g−1 h−1) %K qO2, rate of oxygen consumption (mmol g−1 h−1) %K YGlcX, biomass yield on glucose (g g−1) %K YCO2X, biomass yield on carbon dioxide (g mol−1) %K RQ, respiratory quotient (CO2/O2) %K mGlcX, maintenance coefficient for glucose (g g−1 h−1) %K mO2X, maintenance coefficient for oxygen (mol g−1 h−1) %I Microbiology Society, %X Continuous cultivation was used to study the effect of glucose, ammonium, nitrate or phosphate limitation on the excretion of tricarboxylic acid (TCA) cycle intermediates by Penicillium simplicissimum. Additionally, the effect of benzoic acid, salicylhydroxamic acid (SHAM) and 2,4-dinitrophenol on TCA cycle intermediates was studied. The physiological state of the fungus was characterized by its glucose and O2 consumption, its CO2 production, its intra- and extracellular concentrations of TCA cycle intermediates, as well as by its biomass yield, its maintenance coefficient and its respiratory quotient. The excretion of TCA cycle intermediates was observed during ammonium-, nitrate- and phosphate-limited growth. The highest productivity was found with phosphate-limited growth. The respiratory quotient was 1·3 under ammonium limitation and 0·7 under phosphate limitation. Citrate was always the main excreted intermediate. This justifies calling this excretion an energy-spilling process, because citrate excretion avoids the synthesis of too much NADH. The addition of benzoic acid further increased the excretion of TCA cycle intermediates by ammonium-limited hyphae. A SHAM-sensitive respiration was constitutively present during ammonium-limited growth of the fungus. The sum of the excreted organic acids was negatively correlated with the biomass yield (Y GlcX). %U https://www.microbiologyresearch.org/content/journal/micro/10.1099/00221287-148-4-1143