Open AccessMetabolic engineering of a xylose‐isomerase‐expressing Saccharomyces cerevisiae strain for rapid anaerobic xylose fermentation
Author(s) -
Kuyper Marko,
Hartog Miranda M.P.,
Toirkens Maurice J.,
Almering Marinka J.H.,
Winkler Aaron A.,
Dijken Johannes P.,
Pronk Jack T.
Publication year - 2005
Publication title -
fems yeast research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.991
H-Index - 92
eISSN - 1567-1364
pISSN - 1567-1356
DOI - 10.1016/j.femsyr.2004.09.010
Subject(s) - xylose isomerase , xylose , biochemistry , isomerase , xylose metabolism , xylitol , transketolase , transaldolase , biology , fermentation , metabolic engineering , enzyme , pentose phosphate pathway , glycolysis
After an extensive selection procedure, Saccharomyces cerevisiae strains that express the xylose isomerase gene from the fungus Piromyces sp. E2 can grow anaerobically on xylose with a μ max of 0.03 h −1 . In order to investigate whether reactions downstream of the isomerase control the rate of xylose consumption, we overexpressed structural genes for all enzymes involved in the conversion of xylulose to glycolytic intermediates, in a xylose‐isomerase‐expressing S. cerevisiae strain. The overexpressed enzymes were xylulokinase (EC 2.7.1.17), ribulose 5‐phosphate isomerase (EC 5.3.1.6), ribulose 5‐phosphate epimerase (EC 5.3.1.1), transketolase (EC 2.2.1.1) and transaldolase (EC 2.2.1.2). In addition, the GRE3 gene encoding aldose reductase was deleted to further minimise xylitol production. Surprisingly the resulting strain grew anaerobically on xylose in synthetic media with a μ max as high as 0.09 h −1 without any non‐defined mutagenesis or selection. During growth on xylose, xylulose formation was absent and xylitol production was negligible. The specific xylose consumption rate in anaerobic xylose cultures was 1.1 g xylose (g biomass) −1 h −1 . Mixtures of glucose and xylose were sequentially but completely consumed by anaerobic batch cultures, with glucose as the preferred substrate.