The effect of fumarate (C4-dicarboxylic acid, a gluconeogenesis precursor) and citrate (a lipid synthesis regulator) on the production of surfactants by Acinetobacter calcoaceticus K-4 grown on ethanol has been studied. Simultaneous addition of fumarate and citrate to concentrations of 0.01-0.02% at the end of the log phase of K-4 growth in a medium with 2 vol% ethanol increases the nominal surfactant concentration by 45-55% in comparison with a culture without organic acids. The increased level of surfactant production in the presence of fumarate and citrate is determined by the increase in the activities of enzymes involved in the production of glycolipids (phosphoenolpyruvate synthase and trehalose phosphate synthase) and aminolipids (NADP(+)-dependent glutamate dehydrogenase) by factors of 1.7-7, as well as by the simultaneous operation of two anaplerotic pathways: the glyoxylate cycle and the reaction catalyzed by phosphoenolpyruvate carboxylase.
