title: Genetic engineering of Zymobacter palmae for production of ethanol from xylose.
abstract: Its metabolic characteristics suggest that Zymobacter palmae gen. nov., sp. nov. could serve as a useful new ethanol-fermenting bacterium, but its biotechnological exploitation will require certain genetic modifications. We therefore engineered Z. palmae so as to broaden the range of its fermentable sugar substrates to include the pentose sugar xylose. The Escherichia coli genes encoding the xylose catabolic enzymes xylose isomerase, xylulokinase, transaldolase, and transketolase were introduced into Z. palmae, where their expression was driven by the Zymomonas mobilis glyceraldehyde-3-phosphate dehydrogenase promoter. When cultured with 40 g/liter xylose, the recombinant Z. palmae strain was able to ferment 16.4 g/liter xylose within 5 days, producing 91% of the theoretical yield of ethanol with no accumulation of organic acids as metabolic by-products. Notably, xylose acclimation enhanced both the expression of xylose catabolic enzymes and the rate of xylose uptake into recombinant Z. palmae, which enabled the acclimated organism to completely and simultaneously ferment a mixture of 40 g/liter glucose and 40 g/liter xylose within 8 h, producing 95% of the theoretical yield of ethanol. Thus, efficient fermentation of a mixture of glucose and xylose to ethanol can be accomplished by using Z. palmae expressing E. coli xylose catabolic enzymes.
authors.affiliation: Department of Biotechnology, Faculty of Engineering, Tottori University, 4-101 Koyamacho-Minami, Tottori, Tottori, Japan. yanase@bio.tottori-u.ac.jp
authors.forename: Hideshi
authors.initials: H
authors.lastname: Yanase
authors.forename: Dai
authors.initials: D
authors.lastname: Sato
authors.forename: Keiko
authors.initials: K
authors.lastname: Yamamoto
authors.forename: Saori
authors.initials: S
authors.lastname: Matsuda
authors.forename: Sho
authors.initials: S
authors.lastname: Yamamoto
authors.forename: Kenji
authors.initials: K
authors.lastname: Okamoto
mesh_terms: D019747:Aldose-Ketose Isomerases / Q000235:genetics; D050260:Carbohydrate Metabolism / Q000235:genetics*; D002264:Carboxylic Acids / Q000378:metabolism; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics; D029968:Escherichia coli Proteins / Q000235:genetics; D000431:Ethanol / Q000378:metabolism*; D005285:Fermentation; D015870:Gene Expression; D005818:Genetic Engineering; D005947:Glucose / Q000378:metabolism; D044129:Halomonadaceae / Q000235:genetics* / Q000378:metabolism*; D053858:Metabolic Networks and Pathways / Q000235:genetics; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000235:genetics; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000235:genetics; D014153:Transaldolase / Q000235:genetics; D014174:Transketolase / Q000235:genetics; D014994:Xylose / Q000378:metabolism*; D017355:Zymomonas
chemical_list: D002264:Carboxylic Acids; D029968:Escherichia coli Proteins; D011994:Recombinant Proteins; D000431:Ethanol; D014994:Xylose; D014174:Transketolase; D014153:Transaldolase; D017853:Phosphotransferases (Alcohol Group Acceptor); C032700:xylulokinase; D019747:Aldose-Ketose Isomerases; C023298:xylose isomerase; D005947:Glucose