HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via CrossRef Citing Articles via Google Scholar Google Scholar Articles by Gallmetzer, M. Articles by Burgstaller, W. Search for Related Content PubMed PubMed Citation Articles by Gallmetzer, M. Articles by Burgstaller, W. Agricola Articles by Gallmetzer, M. Articles by Burgstaller, W.

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

Institute of Microbiology, Leopold-Franzens-University of Innsbruck, Technikerstrasse 25, 6020 Innsbruck, Austria¹

Author for correspondence: Martin Gallmetzer. Tel: +43 512 507 6015. Fax: +43 512 507 2929. e-mail: martin.gallmetzer{at}uibk.ac.at

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).

Keywords: overflow metabolism, continuous culture, chemostat, nutrient limitation, biomass yield

Abbreviations: µ, specific growth rate (h^-1); m_CO2X, maintenance coefficient for carbon dioxide (molg^-1 h^-1); m_GlcX, maintenance coefficient for glucose (gg^-1 h^-1); m_O2X, maintenance coefficient for oxygen (molg^-1 h^-1); q_CO2, rate of carbon dioxide production (mmolg^-1 h^-1); q_Glc, rate of glucose consumption (mmolg^-1 h^-1); q_O2, rate of oxygen consumption (mmolg^-1 h^-1); RQ, respiratory quotient (CO₂/O₂); SHAM, salicylhydroxamic acid; TCA, tricarboxylic acid; Y_CO2X, biomass yield on carbon dioxide (gmol^-1); Y_GlcX, biomass yield on glucose (gg^-1); Y_O2X, biomass yield on oxygen (gmol^-1)