Amino acid and lactate assimilation by Geotrichum candidum were examined in submerged culture. G candidum growth on lysine and lactate clearly showed that lactate can be assimilated as a carbon source, in addition to an energy source. Lysine was chosen since G candidum did not grow on lysine as the sole carbon and nitrogen source. On the contrary, when a convenient carbon source amino acid (glutamate) was used, lactate appeared to have no effect on G candidum growth; it was only assimilated at a low rate during the stationary state for energy supply, in agreement with previous observations recorded during growth on peptones. The assimilation of glutamate, the more convenient substrate for G candidum growth, required less energy than lysine assimilation, indicated by the lower level of CO2 released. (C) 2004 Society of Chemical Industry.