Location: Bioenergy ResearchTitle: Assessment of in situ butanol recovery by vacuum during acetone butanol ethanol (ABE) fermentation Author
Submitted to: Journal of Chemical Technology & Biotechnology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/17/2011
Publication Date: 2/14/2012
Citation: Mariano, A.P., Qureshi, N., Filho, R.M., Ezeji, T.C. 2012. Assessment of in situ butanol recovery by vacuum during acetone butanol ethanol (ABE) fermentation. Journal of Chemical Technology and Biotechnology. 87:334-340. Interpretive Summary: Butanol is a liquid biofuel that can be produced from agricultural crops and residues employing a microorganism known as Clostridium beijerinckii. This biofuel packs 30% more energy than ethanol on a gallon basis. It burns cleaner as it releases less smoke thus making it an environmentally friendly biofuel. It can also be transported in existing pipelines as butanol is non-corrosive. However, one of the major problems with butanol fermentation is its cost intensive recovery from fermentation broth. In the past it was recovered using distillative recovery which is not economical. For this reason we applied a simple technique known as vacuum to remove butanol from fermentation broth. Rate of recovery of butanol employing this technology was higher than its production by the microbial culture and appears to be cost effective. Another advantage of butanol recovery using vacuum is that it can be performed at fermentation temperature and hence can be integrated with simultaneous production and recovery. The developed method on simultaneous butanol production and recovery by vacuum will benefit U.S. farmers, public, and the biofuel industry.
Technical Abstract: Butanol fermentation is product limiting due to butanol toxicity to microbial cells. Butanol (boiling point: 118 deg C) boils at a greater temperature than water (boiling point: 100 deg C) and application of vacuum technology to integrated acetone-butanol-ethanol (ABE) fermentation and recovery may have been ignored due to direct comparison of boiling points of water and butanol. This research demonstrates application of vacuum technology for simultaneous butanol fermentation and in situ butanol recovery. To facilitate ABE mass transfer and recovery under fermentation temperature, batch fermentations were conducted in a 14-l bioreactor (7.0 l reaction volume) connected in series with a condensation system and vacuum pump. Fermentations were conducted in triplicates at 35 deg C in P2 medium using Clostridium beijerinckii 8052 as biocatalyst. Vacuum was operated in two different modes: continuous and intermittent (2 h-vacuum sessions spaced by 4 h-intervals). Concentration of butanol in the recovered stream was greater than the concentration in fermentation broth (from 15.7 g l**-1 up to 55.3 g l**-1). Integration of the vacuum to the bioreactor resulted in enhanced ABE productivity by 100% and complete utilization of glucose as opposed to 17.7 g l**-1 residual glucose concentration in control batch fermentation. The mode of operation of the vacuum had effects on the concentration of solvents in the condensate. In intermittent mode, less water was recovered resulting in a more concentrated condensate.