title: Continuous production of ethanol from hexoses and pentoses using immobilized mixed cultures of Escherichia coli strains.
abstract: We have developed highly efficient ethanologenic Escherichia coli strains that selectively consume pentoses and/or hexoses. Mixed cultures of these strains can be used to selectively adjust the sugar utilization kinetics in ethanol fermentations. Based on the kinetics of sugar utilization, we have designed and implemented an immobilized cell system for the optimized continuous conversion of sugars into ethanol. The results confirm that immobilized mixed cultures support a simultaneous conversion of hexoses and pentoses into ethanol at high yield and at a faster rate than immobilized homogenous cells. Continuous ethanol production has been maintained for several weeks at high productivity with near complete sugar utilization. The control of sugar utilization using immobilized mixed cultures can be adapted to any composition of hexoses and pentoses by adjusting the strain distribution of immobilized cells. The approach, therefore, holds promise for ethanol fermentation from lignocellulosic hydrolysates where the feedstock varies in sugar composition.
authors.affiliation: Department of Chemical Engineering and Materials Science, and BioTechnology Institute, University of Minnesota, 240 Gortner Laboratory, 1479 Gortner Ave, St. Paul, MN 55108, USA.
authors.forename: Pornkamol
authors.initials: P
authors.lastname: Unrean
authors.forename: Friedrich
authors.initials: F
authors.lastname: Srienc
mesh_terms: D000465:Algorithms; D019149:Bioreactors / Q000382:microbiology; D018929:Cell Culture Techniques; D018914:Cells, Immobilized / Q000737:chemistry / Q000378:metabolism*; D004926:Escherichia coli / Q000737:chemistry / Q000378:metabolism*; D000431:Ethanol / Q000378:metabolism*; D005285:Fermentation; D006601:Hexoses / Q000378:metabolism*; D007700:Kinetics; D010429:Pentoses / Q000378:metabolism*
chemical_list: D006601:Hexoses; D010429:Pentoses; D000431:Ethanol