Applied Microbiology and Biotechnology

, Volume 57, Issue 5, pp 631–638

Potential inhibitors from wet oxidation of wheat straw and their effect on growth and ethanol production by Thermoanaerobacter mathranii

  •  H. Klinke
  •  A. Thomsen
  •  B. Ahring
Original Paper

DOI: 10.1007/s002530100825

Cite this article as:
Klinke, H., Thomsen, A. & Ahring, B. Appl Microbiol Biotechnol (2001) 57: 631. doi:10.1007/s002530100825

Abstract.

Alkaline wet oxidation (WO) (using water, 6.5 g/l sodium carbonate, and 12 bar oxygen at 195 °C) was used for pre-treating wheat straw (60 g/l), resulting in a hemicellulose-rich hydrolysate and a cellulose-rich solid fraction. The hydrolysate consisted of soluble hemicellulose (9 g/l), aliphatic carboxylic acids (6 g/l), phenols (0.27 g/l or 1.7 mM), and 2-furoic acid (0.007 g/l). The wet-oxidized wheat straw hydrolysate caused no inhibition of ethanol yield by the anaerobic thermophilic bacterium Thermoanaerobacter mathranii. Nine phenols and 2-furoic acid, identified to be present in the hydrolysate, were each tested in concentrations of 10–100× the concentration found in the hydrolysate for their effect on fermentation by T. mathranii. At 2 mM, these aromatic compounds were not inhibitory to growth or ethanol yield in T. mathranii. When the concentration of aromatics was increased to 10 mM, the fermentation was severely inhibited by the phenol aldehydes and to a lesser extent by the phenol ketones. By adding the same aromatic compounds to WO hydrolysate (10 mM), synergistic inhibitory effects of all tested compounds with hydrolysate components were shown. When the hydrolysate was concentrated three- and six-fold, growth and fermentation with T. mathranii were inhibited. At a six-fold hydrolysate concentration, the total concentration of phenolic monomers was 17 mM; hence aromatic monomers are an important co-factor in hydrolysate inhibition.

Copyright information

© Springer-Verlag 2001

Authors and Affiliations

  •  H. Klinke
    • 1
  •  A. Thomsen
    • 1
  •  B. Ahring
    • 2
  1. 1.Plant Research Department Risø National Laboratory, PO Box 49, 4000 Roskilde, Denmark
  2. 2.BioCentrum-DTU, Technical University of Denmark, 2800 Lyngby, Denmark
  3. 3.Henri Samuli School of Engineering and Applied Science, Civil and Environmental Engineering Dept., Box 951593, Los Angeles, California 90095-1593, USA