초록
<P><B>Abstract</B></P><P><I>Scheffersomyces stipitis</I> and the closely related yeast <I>Candida shehatae</I> assimilated the <SMALL>L</SMALL>‐amino acids glutamate, aspartate and proline as both carbon and nitrogen sole sources. We also found this rarely investigated ability in ascomycetous species such as <I>Candida glabrata, C. reukaufii, C. utilis, Debaryomyces hansenii, Kluyveromyces lactis, K. marxianus, Candida albicans, L. elongisporus, Meyerozyma guilliermondii, C.</I> <I>maltosa, Pichia capsulata</I> and <I>Yarrowia lipolytica</I> and in basidiomycetous species such as <I>Rhodotorula rubra</I> and <I>Trichosporon beigelii</I>. Glutamate was a very efficient carbon source for <I>Sc. stipitis</I>, which enabled a high biomass yield/mole, although the growth rate was lower when compared to growth on glucose medium. The cells secreted waste ammonium during growth on glutamate alone. In <I>Sc. stipitis</I> cultures grown in glucose medium containing glutamate as the nitrogen source the biomass yield was maximal, and ethanol concentration and specific ethanol formation rate were significantly higher than in glucose medium containing ammonium as the nitrogen source. Mainly C‐assimilation of glutamate but also N‐assimilation in glucose‐containing medium correlated with enhanced activity of the NAD‐dependent glutamate dehydrogenase 2 (GDH2). A Δ<I>gdh2</I> disruptant was unable to utilize glutamate as either a carbon or a nitrogen source; moreover, this disruptant was also unable to utilize aspartate as a carbon source. The mutation was complemented by retransformation of the <I>GDH2</I> ORF into the Δ<I>gdh2</I> strain. The results show that Gdh2p plays a dual role in <I>Sc. stipitis</I> as both C‐ and N‐catabolic enzyme, which indicates its role as an interface between the carbon and nitrogen metabolism of this yeast. Copyright © 2011 John Wiley & Sons, Ltd.</P>