Metabolic engineering for improved fermentation of pentoses by yeasts.
Appl Microbiol Biotechnol
; 63(5): 495-509, 2004 Feb.
Article
em En
| MEDLINE
| ID: mdl-14595523
ABSTRACT
The fermentation of xylose is essential for the bioconversion of lignocellulose to fuels and chemicals, but wild-type strains of Saccharomyces cerevisiae do not metabolize xylose, so researchers have engineered xylose metabolism in this yeast. Glucose transporters mediate xylose uptake, but no transporter specific for xylose has yet been identified. Over-expressing genes for aldose (xylose) reductase, xylitol dehydrogenase and moderate levels of xylulokinase enable xylose assimilation and fermentation, but a balanced supply of NAD(P) and NAD(P)H must be maintained to avoid xylitol production. Reducing production of NADPH by blocking the oxidative pentose phosphate cycle can reduce xylitol formation, but this occurs at the expense of xylose assimilation. Respiration is critical for growth on xylose by both native xylose-fermenting yeasts and recombinant S, cerevisiae. Anaerobic growth by recombinant mutants has been reported. Reducing the respiration capacity of xylose-metabolizing yeasts increases ethanol production. Recently, two routes for arabinose metabolism have been engineered in S. cerevisiae and adapted strains of Pichia stipitis have been shown to ferment hydrolysates with ethanol yields of 0.45 g g(-1) sugar consumed, so commercialization seems feasible for some applications.
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Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Pentoses
/
Leveduras
/
Organismos Geneticamente Modificados
Idioma:
En
Revista:
Appl Microbiol Biotechnol
Ano de publicação:
2004
Tipo de documento:
Article