title: Evaluation of hydrophobic micro-zeolite-mixed matrix membrane and integrated with acetone-butanol-ethanol fermentation for enhanced butanol production.
abstract: BACKGROUND
  Butanol is regarded as an advanced biofuel that can be derived from renewable biomass. However, the main challenge for microbial butanol production is low butanol titer, yield and productivity, leading to intensive energy consumption in product recovery. Various alternative separation technologies such as extraction, adsorption and gas stripping, etc., could be integrated with acetone-butanol-ethanol (ABE) fermentation with improving butanol productivity, but their butanol selectivities are not satisfactory. The membrane-based pervaporation technology is recently attracting increasing attention since it has potentially desirable butanol selectivity.
  
  
  RESULTS
  The performance of the zeolite-mixed polydimethylsiloxane (PDMS) membranes were evaluated to recover butanol from butanol/water binary solution as well as fermentation broth in the integrated ABE fermentation system. The separation factor and butanol titer in permeate of the zeolite-mixed PDMS membrane were up to 33.0 and 334.6 g/L at 80°C, respectively, which increased with increasing zeolite loading weight in the membrane as well as feed temperature. The enhanced butanol separation factor was attributed to the hydrophobic zeolites with large pore size providing selective routes preferable for butanol permeation. In fed-batch fermentation incorporated with pervaporation, 54.9 g/L ABE (34.5 g/L butanol, 17.0 g/L acetone and 3.4 g/L ethanol) were produced from 172.3 g/L glucose. The overall butanol productivity and yield increased by 16.0 and 11.1%, respectively, which was attributed to the alleviated butanol inhibition by pervaporation and reassimilation of acids for ABE production. The zeolite-mixed membrane produced a highly concentrated condensate containing 169.6 g/L butanol or 253.3 g/L ABE, which after phase separation easily gave the final product containing >600 g/L butanol.
  
  
  CONCLUSIONS
  Zeolite loading in the PDMS matrix was attributed to improving the pervaporative performance of the membrane, showing great potential to recover butanol with high purity. Therefore, this zeolite-mixed PDMS membrane had the potential to improve biobutanol production when integrating with ABE fermentation.
authors.affiliation: School of Life Science and Biotechnology, Dalian University of Technology, Linggong Road 2, Dalian, 116024 China.
authors.forename: Chuang
authors.initials: C
authors.lastname: Xue
authors.affiliation: School of Life Science and Biotechnology, Dalian University of Technology, Linggong Road 2, Dalian, 116024 China.
authors.forename: Decai
authors.initials: D
authors.lastname: Yang
authors.affiliation: School of Life Science and Biotechnology, Dalian University of Technology, Linggong Road 2, Dalian, 116024 China.
authors.forename: Guangqing
authors.initials: G
authors.lastname: Du
authors.affiliation: School of Life Science and Biotechnology, Dalian University of Technology, Linggong Road 2, Dalian, 116024 China.
authors.forename: Lijie
authors.initials: L
authors.lastname: Chen
authors.affiliation: School of Life Science and Biotechnology, Dalian University of Technology, Linggong Road 2, Dalian, 116024 China.
authors.forename: Jiangang
authors.initials: J
authors.lastname: Ren
authors.affiliation: School of Life Science and Biotechnology, Dalian University of Technology, Linggong Road 2, Dalian, 116024 China ; School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai, 200240 China.
authors.forename: Fengwu
authors.initials: F
authors.lastname: Bai
keywords: ABE fermentation; Butanol recovery; Pervaporation; Zeolite-mixed membrane