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C‐ and N‐catabolic utilization of tricarboxylic acid cycle‐related amino acids by Scheffersomyces stipitis and other yeasts
Author(s) -
Freese Stefan,
Vogts Tanja,
Speer Falk,
Schäfer Bernd,
Passoth Volkmar,
Klinner Ulrich
Publication year - 2011
Publication title -
yeast
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.923
H-Index - 102
eISSN - 1097-0061
pISSN - 0749-503X
DOI - 10.1002/yea.1845
Subject(s) - pichia stipitis , biology , yarrowia , biochemistry , kluyveromyces marxianus , xylose , yeast , fermentation , kluyveromyces lactis , saccharomyces cerevisiae
Scheffersomyces stipitis and the closely related yeast Candida shehatae assimilated the L ‐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 Candida glabrata, C. reukaufii, C. utilis, Debaryomyces hansenii, Kluyveromyces lactis, K. marxianus, Candida albicans, L. elongisporus, Meyerozyma guilliermondii, C. maltosa, Pichia capsulata and Yarrowia lipolytica and in basidiomycetous species such as Rhodotorula rubra and Trichosporon beigelii . Glutamate was a very efficient carbon source for Sc. stipitis , 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 Sc. stipitis 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 gdh2 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 GDH2 ORF into the Δ gdh2 strain. The results show that Gdh2p plays a dual role in Sc. stipitis 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.