Enhanced cofermentation of glucose and xylose by recombinantSaccharomyces yeast strains in batch and
June 27th, 2008 | by admin |Enhanced cofermentation of glucose and xylose by recombinantSaccharomyces yeast strains in batch and continuous operating modes.
Agricultural residues, such as grain by-products, are rich in the hydrolyzable carbohydrate polymers hemicellulose and cellulose; hence, they represent a readily available source of the fermentable sugars xylose and glucose. The biomass-to-ethanol technology is now a step closer to commercialization because a stable recombinant yeast strain has been developed that can efficiently ferment glucose and xylose simultaneously (coferment) to ethanol. This strain, LNH-ST, is a derivative ofSaccharomyces yeast strain 1400 that carries the xylose-catabolism encoding genes ofPichia stipitis in its chromosome. Continuous pure sugar cofermentation studies with this organism resulted in promising steady-state ethanol yields (70.4% of theoretical based on available sugars) at a residence time of 48 h. Further studies with corn biomass pretreated at the pilot scale confirmed the performance characteristics of the organism in a simultaneous saccharification and cofermentation (SSCF) process: LNH-ST converted 78.4% of the available glucose and 56.1% of the available xylose within 4 d, despite the presence of high levels of metabolic inhibitors. These SSCF data were reproducible at the bench scale and verified in a 9000-L pilot scale bioreactor.
Toon ST, Philippidis GP, Ho NW, Chen Z, Brainard A, Lumpkin RE, Riley CJ.
Biotechnology Center for Fuels and Chemicals, National Renewable Energy Laboratory (NREL), 1617 Cole Boulevard, 80401, Golden, CO.