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Biotechnol J. 2012 Mar;7(3):361-73. doi: 10.1002/biot.201100209.

An evaluation of cellulose saccharification and fermentation with an engineered Saccharomyces cerevisiae capable of cellobiose and xylose utilization.

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  • 1Energy Biosciences Institute University of California, Berkeley, CA 94720-1462, USA.

Abstract

Commercial-scale cellulosic ethanol production has been hindered by high costs associated with cellulose-to-glucose conversion and hexose and pentose co-fermentation. Simultaneous saccharification and fermentation (SSF) with a yeast strain capable of xylose and cellobiose co-utilization has been proposed as a possible avenue to reduce these costs. The recently developed DA24-16 strain of Saccharomyces cerevisiae incorporates a xylose assimilation pathway and a cellodextrin transporter (CDT) that permit rapid growth on xylose and cellobiose. In the current work, a mechanistic kinetic model of cellulase-catalyzed hydrolysis of cellulose was combined with a multi-substrate model of microbial growth to investigate the ability of DA24-16 and improved cellobiose-consuming strains to obviate the need for exogenously added β-glucosidase and to assess the impact of cellobiose utilization on SSF and separate hydrolysis and fermentation (SHF). Results indicate that improved CDT-containing strains capable of growing on cellobiose as rapidly as on glucose produced ethanol nearly as rapidly as non-CDT-containing yeast supplemented with β-glucosidase. In producing 75 g/L ethanol, SSF with any strain did not result in shorter residence times than SHF with a 12 h saccharification step. Strains with improved cellobiose utilization are therefore unlikely to allow higher titers to be reached more quickly in SSF than in SHF.

Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

[PubMed - indexed for MEDLINE]
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