Achievements and perspectives to overcome the poor solvent resistance in acetone and butanol-producing microorganisms

Thaddeus Ezeji, Caroline Milne, Nathan D. Price, Hans P. Blaschek

Research output: Contribution to journalShort surveypeer-review


Anaerobic bacteria such as the solventogenic clostridia can ferment a wide range of carbon sources (e.g., glucose, galactose, cellobiose, mannose, xylose, and arabinose) to produce carboxylic acids (acetic and butyric) and solvents such as acetone, butanol, and ethanol (ABE). The fermentation process typically proceeds in two phases (acidogenic and solventogenic) in a batch mode. Poor solvent resistance by the solventogenic clostridia and other fermenting microorganisms is a major limiting factor in the profitability of ABE production by fermentation. The toxic effect of solvents, especially butanol, limits the concentration of these solvents in the fermentation broth, limiting solvent yields and adding to the cost of solvent recovery from dilute solutions. The accepted dogma is that toxicity in the ABE fermentation is due to chaotropic effects of butanol on the cell membranes of the fermenting microorganisms, which poses a challenge for the biotechnological whole-cell bio-production of butanol. This mini-review is focused on (1) the effects of solvents on inhibition of cell metabolism (nutrient transport, ion transport, and energy metabolism); (2) cell membrane fluidity, death, and solvent tolerance associated with the ability of cells to tolerate high concentrations of solvents without significant loss of cell function; and (3) strategies for overcoming poor solvent resistance in acetone and butanol-producing microorganisms.

Original languageEnglish (US)
Pages (from-to)1697-1712
Number of pages16
JournalApplied Microbiology and Biotechnology
Issue number6
StatePublished - Feb 2010


  • Acetone
  • Butanol toxicity
  • Clostridium
  • Solvents
  • Tolerance

ASJC Scopus subject areas

  • Biotechnology
  • Applied Microbiology and Biotechnology


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