title: Co-fermentation of carbon sources by Enterobacter aerogenes ATCC 29007 to enhance the production of bioethanol.
abstract: We investigated the enhancement of bioethanol production in Enterobacter aerogenes ATCC 29007 by co-fermentation of carbon sources such as glycerol, glucose, galactose, sucrose, fructose, xylose, starch, mannitol and citric acid. Biofuel production increases with increasing growth rate of microorganisms; that is why we investigated the optimal growth rate of E. aerogenes ATCC 29007, using mixtures of different carbon sources with glycerol. E. aerogenes ATCC 29007 was incubated in media containing each carbon source and glycerol; growth rate and bioethanol production improved in all cases compared to those in medium containing glycerol alone. The growth rate and bioethanol production were highest with mannitol. Fermentation was carried out at 37 °C for 18 h, pH 7, using 50 mL defined production medium in 100 mL serum bottles at 200 rpm. Bioethanol production under optimized conditions in medium containing 16 g/L mannitol and 20 g/L glycerol increased sixfold (32.10 g/L) than that containing glycerol alone (5.23 g/L) as the carbon source in anaerobic conditions. Similarly, bioethanol production using free cells in continuous co-fermentation also improved (27.28 g/L) when 90.37 % of 16 g/L mannitol and 67.15 % of 20 g/L glycerol were used. Although naturally existing or engineered microorganisms can ferment mixed sugars sequentially, the preferential utilization of glucose to non-glucose sugars often results in lower overall yield and productivity of ethanol. Here, we present new findings in E. aerogenes ATCC 29007 that can be used to improve bioethanol production by simultaneous co-fermentation of glycerol and mannitol.
authors.affiliation: Department of Chemical and Biological Engineering, Korea University, 1, Anam-Dong, Seongbuk-Gu, Seoul, 136-701, Republic of Korea.
authors.forename: Laxmi Prasad
authors.initials: LP
authors.lastname: Thapa
authors.forename: Sang Jun
authors.initials: SJ
authors.lastname: Lee
authors.forename: Xiao Guang
authors.initials: XG
authors.lastname: Yang
authors.forename: Hah Young
authors.initials: HY
authors.lastname: Yoo
authors.forename: Sung Bong
authors.initials: SB
authors.lastname: Kim
authors.forename: Chulhwan
authors.initials: C
authors.lastname: Park
authors.forename: Seung Wook
authors.initials: SW
authors.lastname: Kim
mesh_terms: D056804:Biofuels; D002241:Carbohydrates / Q000494:pharmacology*; D003451:Cryoprotective Agents / Q000378:metabolism / Q000494:pharmacology*; D021902:Enterobacter aerogenes / Q000254:growth & development*; D000431:Ethanol / Q000378:metabolism*; D005990:Glycerol / Q000378:metabolism / Q000494:pharmacology*
chemical_list: D056804:Biofuels; D002241:Carbohydrates; D003451:Cryoprotective Agents; D000431:Ethanol; D005990:Glycerol