title: A whole cell biocatalyst for cellulosic ethanol production from dilute acid-pretreated corn stover hydrolyzates.
abstract: In this research, a recombinant whole cell biocatalyst was developed by expressing three cellulases from Clostridium cellulolyticum--endoglucanase (Cel5A), exoglucanase (Cel9E), and β-glucosidase--on the surface of the Escherichia coli LY01. The modified strain is identified as LY01/pRE1H-AEB. The cellulases were displayed on the surface of the cell by fusing with an anchor protein, PgsA. The developed whole cell biocatalyst was used for single-step ethanol fermentation using the phosphoric acid-swollen cellulose (PASC) and the dilute acid-pretreated corn stover. Ethanol production was 3.59 ± 0.15 g/L using 10 g/L of PASC, which corresponds to a theoretical yield of 95.4 ± 0.15%. Ethanol production was 0.30 ± 0.02 g/L when 1 g/L equivalent of glucose in the cellulosic fraction of the dilute sulfuric acid-pretreated corn stover (PCS) was fermented for 84 h. A total of 0.71 ± 0.12 g/L ethanol was produced in 48 h when the PCS was fermented in the simultaneous saccharification and co-fermentation mode using the hemicellulosic (1 g/L of total soluble sugar) and as well as the cellulosic (1 g/L of glucose equivalent) parts of PCS. In a control experiment, 0.48 g/L ethanol was obtained from 1 g/L of hemicellulosic PCS. It was concluded that the whole cell biocatalyst could convert both cellulosic and hemicellulosic substrates into ethanol in a single reactor. The developed C. cellulolyticum-E. coli whole cell biocatalyst also overcame the incompatible temperature problem of the frequently reported fungal-yeast systems.
authors.affiliation: Department of Chemical Engineering, Texas Tech University, 6th and Canton St., Lubbock, TX 79409, USA.
authors.forename: Seunghyun
authors.initials: S
authors.lastname: Ryu
authors.forename: Muhammad Nazmul
authors.initials: MN
authors.lastname: Karim
mesh_terms: D055162:Biocatalysis; D057005:Bioengineering / Q000379:methods; D002480:Cellulase / Q000378:metabolism; D002482:Cellulose / Q000378:metabolism*; D046973:Ruminiclostridium cellulolyticum / Q000235:genetics / Q000378:metabolism*; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism*; D000431:Ethanol / Q000378:metabolism*; D005285:Fermentation; D005818:Genetic Engineering / Q000379:methods; D006026:Glycoside Hydrolases / Q000378:metabolism; D015202:Protein Engineering / Q000379:methods; D017855:Transferases (Other Substituted Phosphate Groups) / Q000378:metabolism; D003313:Zea mays / Q000378:metabolism*; D001617:beta-Glucosidase / Q000378:metabolism
chemical_list: D000431:Ethanol; D002482:Cellulose; D017855:Transferases (Other Substituted Phosphate Groups); C020676:CDP-diacylglycerol-glycerol-3-phosphate 3-phosphatidyltransferase; D006026:Glycoside Hydrolases; D001617:beta-Glucosidase; D002480:Cellulase