title: Improved efficiency of butanol production by absorbent fermentation with a renewable carrier.
abstract: BACKGROUND
  Biobutanol production is still not economically competitive because of some principal drawbacks including high cost in feedstock consumption, low butanol concentration in the fermentation broth caused by severe product inhibition. An alternative fermentation mode is becoming an urgent requirement to solve these problems. Biobutanol production by absorbent fermentation with a renewable carrier, i.e. pretreated straw materials, is studied in this paper.
  
  
  RESULTS
  Compared with other types of porous media, alkali-treated steam-exploded straw was proved to be a suitable carrier for absorbent fermentation of butanol. The Acetone-Butanol-Ethanol (ABE) concentration increased by 52% compared with submerged culture at an initial glucose concentration of 65 g/L. The adsorption of ABE solvent on substrate and increased bacterial concentration alleviated the end product inhibition and partly explained this positive effect. The steam pretreatment conditions, solid-liquid ratio, substrate types and substrate concentration were also investigated. Steam-explosion at 1.1 MPa for 4 min and solid-liquid ratio of 1:10 was shown to be the optimum. Glucose showed a great advantage over xylose, and higher glucose content was more conducive to biobutanol production. However, the yield of solvent decreased with the increased initial sugar concentration. Considering comprehensively, 100 g/L initial glucose was considered to be the optimum.
  
  
  CONCLUSIONS
  This work demonstrated an effective approach of improved butanol fermentation and its probable mechanisms of this positive effect, i.e. the adsorption of ABE solvent and the adhesion of bacteria on porous substrate accounted for the production improvement and the proportional variation of solvent constituents.
authors: National Key Laboratory of Biochemical Engineering, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190, People's Republic of China. hzchen@home.ipe.ac.cn.
authors: Qin
authors: Q
authors: He
authors: Hongzhang
authors: H
authors: Chen
references: Biotechnol Bioeng. 2009 Feb 15;102(3):811-21
references: 18831001
references: Lett Appl Microbiol. 2007 Jun;44(6):582-7
references: 17576217
references: Trends Biotechnol. 2000 Aug;18(8):356-60
references: 10899817
references: Biotechnol Bioeng. 1999 Nov 20;65(4):447-58
references: 10506420
references: Biotechnol Adv. 2009 Nov-Dec;27(6):849-856
references: 19577627
references: Biotechnol Bioeng. 2008 Oct 1;101(2):209-28
references: 18727018
references: Crit Rev Biotechnol. 2005 Jan-Jun;25(1-2):1-30
references: 15999850
references: Bioresour Technol. 2012 Feb;106:110-6
references: 22197332
references: J Biosci Bioeng. 2009 Aug;108(2):105-10
references: 19619855
references: Biotechnol Lett. 2011 Aug;33(8):1587-91
references: 21424838
references: Chem Rec. 2004;4(5):305-14
references: 15543610
references: Bioresour Technol. 2013 May;135:396-402
references: 22939598
references: J Biosci Bioeng. 2013 Mar;115(3):298-302
references: 23085417
references: Biotechnol Bioeng. 1993 Nov 5;42(9):1053-60
references: 18613233
references: Mol Microbiol. 2006 Apr;60(1):5-15
references: 16556216
references: Bioresour Technol. 2009 Feb;100(3):1315-8
references: 18799308
references: Appl Biochem Biotechnol. 2010 Dec;162(8):2244-58
references: 20526822
references: Appl Environ Microbiol. 1985 Apr;49(4):874-8
references: 4004220