title: Simultaneous consumption of pentose and hexose sugars: an optimal microbial phenotype for efficient fermentation of lignocellulosic biomass.
abstract: Lignocellulosic biomass is an attractive carbon source for bio-based fuel and chemical production; however, its compositional heterogeneity hinders its commercial use. Since most microbes possess carbon catabolite repression (CCR), mixed sugars derived from the lignocellulose are consumed sequentially, reducing the efficacy of the overall process. To overcome this barrier, microbes that exhibit the simultaneous consumption of mixed sugars have been isolated and/or developed and evaluated for the lignocellulosic biomass utilization. Specific strains of Escherichia coli, Saccharomyces cerevisiae, and Zymomonas mobilis have been engineered for simultaneous glucose and xylose utilization via mutagenesis or introduction of a xylose metabolic pathway. Other microbes, such as Lactobacillus brevis, Lactobacillus buchneri, and Candida shehatae possess a relaxed CCR mechanism, showing simultaneous consumption of glucose and xylose. By exploiting CCR-negative phenotypes, various integrated processes have been developed that incorporate both enzyme hydrolysis of lignocellulosic material and mixed sugar fermentation, thereby enabling greater productivity and fermentation efficacy.
authors.affiliation: Robert Mondavi Institute for Wine and Food Science, Department of Viticulture and Enology, University of California, Davis, 95616, USA.
authors.forename: Jae-Han
authors.initials: JH
authors.lastname: Kim
authors.forename: David E
authors.initials: DE
authors.lastname: Block
authors.forename: David A
authors.initials: DA
authors.lastname: Mills
mesh_terms: D001419:Bacteria / Q000235:genetics / Q000378:metabolism*; D056804:Biofuels; D018533:Biomass; D002244:Carbon; D057465:Catabolite Repression; D004734:Energy Metabolism; D005285:Fermentation / Q000235:genetics; D005658:Fungi / Q000235:genetics / Q000378:metabolism*; D005818:Genetic Engineering; D006601:Hexoses / Q000378:metabolism*; D006868:Hydrolysis; D007218:Industrial Microbiology; D008031:Lignin / Q000378:metabolism*; D053858:Metabolic Networks and Pathways / Q000235:genetics; D010429:Pentoses / Q000378:metabolism*; D013379:Substrate Specificity
chemical_list: D056804:Biofuels; D006601:Hexoses; D010429:Pentoses; C036909:lignocellulose; D002244:Carbon; D008031:Lignin