Development of yeasts for xylose fermentation
- Univ. of Wisconsin, Madison, WI (United States)
Xylose is an abundant sugar in hardwoods and agricultural residues. Its use is essential for any economical conversion of lignocellulose to ethanol. Only a few yeasts ferment xylose effectively. Our results show that the best strains are Candida shehatae ATCC 2984 and Pichia stipitis CBS 6054. Wild type strains of C. shehatae ATCC 22984 will produce 56 g/L of ethanol from xylose within 48 h in a fed batch fermentation. We have obtained improved mutants of P.stipitis by selecting for growth on L-xylose and L-arabinose. Mutant strains produce up to 55% more ethanol than the parent and exhibit higher specific fermentation rates. We have also developed an effective transformation system that enables the introduction and expression of heterologous DNA on integrating and autonomous vectors. The transformation system for P. stipitis is based on its URA3 gene as a selectable marker and an autonomous replication sequence (ARS) which we isolated from the parent. We are using integrating and ARS vectors to metabolically engineer P. stipitis by altering the regulation and expression of key enzymes. As model systems we are examining the expression of alcohol dehydrogenase (ADH) and pyruvate decarboxylase (PDC) that are present in limiting amounts or induced only under non-growth conditions.
- Research Organization:
- National Renewable Energy Lab. (NREL), Golden, CO (United States)
- OSTI ID:
- 140217
- Report Number(s):
- NREL/CP-200-5768-Vol.2; CONF-9308106-Vol.2; ON: DE94000435; CNN: Grant 91-019-24; TRN: 93:003832-0021
- Resource Relation:
- Conference: 1. biomass conference of the Americas: energy, environment, agriculture, and industry, Burlington, VT (United States), 30 Aug - 2 Sep 1993; Other Information: PBD: [1993]; Related Information: Is Part Of First Biomass Conference of the Americas: Energy, environment, agriculture, and industry; Proceedings, Volume 2; PB: 711 p.
- Country of Publication:
- United States
- Language:
- English
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