title: Metabolic evolution of non-transgenic Escherichia coli SZ420 for enhanced homoethanol fermentation from xylose.
abstract: Efficient utilization of pentose sugars (xylose and arabinose) is an essential requirement for economically viable ethanol production from cellulosic biomass. The desirable pentose-fermenting ethanologenic biocatalysts are the native microorganisms or the engineered derivatives without recruited exogenous gene(s). We have used a metabolic evolution (adaptive selection) approach to improve a non-transgenic homoethanol Escherichia coli SZ420 (ldhA pflB ackA frdBC pdhR::pflBp6-aceEF-lpd) for xylose fermentation. An improved mutant, E. coli KC01, was evolved through a 3 month metabolic evolution process. This evolved mutant increased pyruvate dehydrogenase activity by 100%, cell growth rate (h(-1)) by 23%, volumetric ethanol productivity by 65% and ethanol tolerance by 200%. These improvements enabled KC01 to complete 50 g xylose l(-1) fermentations with an ethanol titer of 23 g l(-1) and a yield of 90%. The improved cell growth and ethanol production of KC01 are likely attributed to its three fold increased ethanol tolerance.
authors.affiliation: Department of Biological Sciences, Northern Illinois University, DeKalb, IL, 60115, USA.
authors.forename: K
authors.initials: K
authors.lastname: Chen
authors.forename: A G
authors.initials: AG
authors.lastname: Iverson
authors.forename: E A
authors.initials: EA
authors.lastname: Garza
authors.forename: W S
authors.initials: WS
authors.lastname: Grayburn
authors.forename: S
authors.initials: S
authors.lastname: Zhou
mesh_terms: D000693:Anaerobiosis; D004926:Escherichia coli / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D000431:Ethanol / Q000378:metabolism*; D005285:Fermentation / Q000235:genetics / Q000502:physiology*; D007218:Industrial Microbiology / Q000379:methods*; D007658:Ketone Oxidoreductases / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D016133:Polymerase Chain Reaction; D014994:Xylose / Q000378:metabolism*
chemical_list: D029968:Escherichia coli Proteins; D000431:Ethanol; D014994:Xylose; D007658:Ketone Oxidoreductases; C053164:pyruvate dehydrogenase (NADP+)