title: Biobutanol production in a Clostridium acetobutylicum biofilm reactor integrated with simultaneous product recovery by adsorption.
abstract: BACKGROUND
  Clostridium acetobutylicum can propagate on fibrous matrices and form biofilms that have improved butanol tolerance and a high fermentation rate and can be repeatedly used. Previously, a novel macroporous resin, KA-I, was synthesized in our laboratory and was demonstrated to be a good adsorbent with high selectivity and capacity for butanol recovery from a model solution. Based on these results, we aimed to develop a process integrating a biofilm reactor with simultaneous product recovery using the KA-I resin to maximize the production efficiency of biobutanol.
  
  
  RESULTS
  KA-I showed great affinity for butanol and butyrate and could selectively enhance acetoin production at the expense of acetone during the fermentation. The biofilm reactor exhibited high productivity with considerably low broth turbidity during repeated batch fermentations. By maintaining the butanol level above 6.5 g/L in the biofilm reactor, butyrate adsorption by the KA-I resin was effectively reduced. Co-adsorption of acetone by the resin improved the fermentation performance. By redox modulation with methyl viologen (MV), the butanol-acetone ratio and the total product yield increased. An equivalent solvent titer of 96.5 to 130.7 g/L was achieved with a productivity of 1.0 to 1.5 g · L-1 · h-1. The solvent concentration and productivity increased by 4 to 6-fold and 3 to 5-fold, respectively, compared to traditional batch fermentation using planktonic culture.
  
  
  CONCLUSIONS
  Compared to the conventional process, the integrated process dramatically improved the productivity and reduced the energy consumption as well as water usage in biobutanol production. While genetic engineering focuses on strain improvement to enhance butanol production, process development can fully exploit the productivity of a strain and maximize the production efficiency.
authors.affiliation: State Key Laboratory of Materials-Oriented Chemical Engineering, College of Biotechnology and Pharmaceutical Engineering, Nanjing University of Technology, No. 30, Puzhu South Road, Nanjing 211816, China.
authors.forename: Dong
authors.initials: D
authors.lastname: Liu
authors.affiliation: State Key Laboratory of Materials-Oriented Chemical Engineering, College of Biotechnology and Pharmaceutical Engineering, Nanjing University of Technology, No. 30, Puzhu South Road, Nanjing 211816, China.
authors.forename: Yong
authors.initials: Y
authors.lastname: Chen
authors.affiliation: State Key Laboratory of Materials-Oriented Chemical Engineering, College of Biotechnology and Pharmaceutical Engineering, Nanjing University of Technology, No. 30, Puzhu South Road, Nanjing 211816, China.
authors.forename: Feng-Ying
authors.initials: FY
authors.lastname: Ding
authors.affiliation: State Key Laboratory of Materials-Oriented Chemical Engineering, College of Biotechnology and Pharmaceutical Engineering, Nanjing University of Technology, No. 30, Puzhu South Road, Nanjing 211816, China.
authors.forename: Ting
authors.initials: T
authors.lastname: Zhao
authors.affiliation: State Key Laboratory of Materials-Oriented Chemical Engineering, College of Biotechnology and Pharmaceutical Engineering, Nanjing University of Technology, No. 30, Puzhu South Road, Nanjing 211816, China.
authors.forename: Jing-Lan
authors.initials: JL
authors.lastname: Wu
authors.affiliation: State Key Laboratory of Materials-Oriented Chemical Engineering, College of Biotechnology and Pharmaceutical Engineering, Nanjing University of Technology, No. 30, Puzhu South Road, Nanjing 211816, China.
authors.forename: Ting
authors.initials: T
authors.lastname: Guo
authors.affiliation: State Key Laboratory of Materials-Oriented Chemical Engineering, College of Biotechnology and Pharmaceutical Engineering, Nanjing University of Technology, No. 30, Puzhu South Road, Nanjing 211816, China.
authors.forename: Heng-Fei
authors.initials: HF
authors.lastname: Ren
authors.affiliation: State Key Laboratory of Materials-Oriented Chemical Engineering, College of Biotechnology and Pharmaceutical Engineering, Nanjing University of Technology, No. 30, Puzhu South Road, Nanjing 211816, China.
authors.forename: Bing-Bing
authors.initials: BB
authors.lastname: Li
authors.affiliation: State Key Laboratory of Materials-Oriented Chemical Engineering, College of Biotechnology and Pharmaceutical Engineering, Nanjing University of Technology, No. 30, Puzhu South Road, Nanjing 211816, China.
authors.forename: Huan-Qing
authors.initials: HQ
authors.lastname: Niu
authors.affiliation: State Key Laboratory of Materials-Oriented Chemical Engineering, College of Biotechnology and Pharmaceutical Engineering, Nanjing University of Technology, No. 30, Puzhu South Road, Nanjing 211816, China.
authors.forename: Zhi
authors.initials: Z
authors.lastname: Cao
authors.affiliation: State Key Laboratory of Materials-Oriented Chemical Engineering, College of Biotechnology and Pharmaceutical Engineering, Nanjing University of Technology, No. 30, Puzhu South Road, Nanjing 211816, China.
authors.forename: Xiao-Qing
authors.initials: XQ
authors.lastname: Lin
authors.affiliation: State Key Laboratory of Materials-Oriented Chemical Engineering, College of Biotechnology and Pharmaceutical Engineering, Nanjing University of Technology, No. 30, Puzhu South Road, Nanjing 211816, China.
authors.forename: Jing-Jing
authors.initials: JJ
authors.lastname: Xie
authors.affiliation: State Key Laboratory of Materials-Oriented Chemical Engineering, College of Biotechnology and Pharmaceutical Engineering, Nanjing University of Technology, No. 30, Puzhu South Road, Nanjing 211816, China.
authors.forename: Xue-Jun
authors.initials: XJ
authors.lastname: He
authors.affiliation: State Key Laboratory of Materials-Oriented Chemical Engineering, College of Biotechnology and Pharmaceutical Engineering, Nanjing University of Technology, No. 30, Puzhu South Road, Nanjing 211816, China.
authors.forename: Han-Jie
authors.initials: HJ
authors.lastname: Ying