Continuous removal of ethanol from dilute ethanol-water mixtures using hot microbubbles

Joseph Calverley, William B. Zimmerman, David J. Leak, H. C. Hemaka Bandulasena

Research output: Contribution to journalArticlepeer-review

7 Citations (SciVal)


Product inhibition is a barrier to many fermentation processes, including bioethanol production, and is responsible for dilute product streams which are energy intensive to purify. The main purpose of this study was to investigate whether hot microbubble stripping could be used to remove ethanol continuously from dilute ethanol–water mixtures expected in a bioreactor and maintain ethanol concentrations below the inhibitory levels for the thermophile Parageobacillus thermoglucosidasius (TM242), that can utilize a range of sugars derived from lignocellulosic biomass. A custom-made microbubble stripping unit that produces clouds of hot microbubbles (~120 °C) by fluidic oscillation was used to remove ethanol from ~2% (v/v) ethanol–water mixtures maintained at 60 °C. Ethanol was continuously added to the unit to simulate microbial metabolism. The initial liquid height and the ethanol addition rate were varied from 10 to 50 mm and 2.1–21.2 g h−1 respectively. In all the experiments, ethanol concentration was maintained well below the inhibition threshold of the target organism (~2% [v/v]). This microbubble stripping unit has the potential to operate in conjunction with a 0.5–1.0 L fermenter to allow an ethanol productivity of 14.9–7.8 g L1h−1 continuously.

Original languageEnglish
Article number130511
JournalChemical Engineering Journal
Early online date28 May 2021
Publication statusPublished - 15 Nov 2021


  • Air stripping
  • Bioethanol recovery
  • Ethanol–water mixtures
  • Microbubbles
  • Product inhibition

ASJC Scopus subject areas

  • Chemistry(all)
  • Environmental Chemistry
  • Chemical Engineering(all)
  • Industrial and Manufacturing Engineering


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