title: Ethanol effect on metabolic activity of the ethalogenic fungus Fusarium oxysporum.
abstract: BACKGROUND
  Fusarium oxysporum is a filamentous fungus which has attracted a lot of scientific interest not only due to its ability to produce a variety of lignocellulolytic enzymes, but also because it is able to ferment both hexoses and pentoses to ethanol. Although this fungus has been studied a lot as a cell factory, regarding applications for the production of bioethanol and other high added value products, no systematic study has been performed concerning its ethanol tolerance levels.
  
  
  RESULTS
  In aerobic conditions it was shown that both the biomass production and the specific growth rate were affected by the presence of ethanol. The maximum allowable ethanol concentration, above which cells could not grow, was predicted to be 72 g/L. Under limited aeration conditions the ethanol-producing capability of the cells was completely inhibited at 50 g/L ethanol. The lignocellulolytic enzymatic activities were affected to a lesser extent by the presence of ethanol, while the ethanol inhibitory effect appears to be more severe at elevated temperatures. Moreover, when the produced ethanol was partially removed from the broth, it led to an increase in fermenting ability of the fungus up to 22.5%. The addition of F. oxysporum's system was shown to increase the fermentation of pretreated wheat straw by 11%, in co-fermentation with Saccharomyces cerevisiae.
  
  
  CONCLUSIONS
  The assessment of ethanol tolerance levels of F. oxysporum on aerobic growth, on lignocellulolytic activities and on fermentative performance confirmed its biotechnological potential for the production of bioethanol. The cellulolytic and xylanolytic enzymes of this fungus could be exploited within the biorefinery concept as their ethanol resistance is similar to that of the commercial enzymes broadly used in large scale fermentations and therefore, may substantially contribute to a rational design of a bioconversion process involving F. oxysporum. The SSCF experiments on liquefied wheat straw rich in hemicellulose indicated that the contribution of the metabolic system of F. oxysporum in a co-fermentation with S. cerevisiae may play a secondary role.
authors.affiliation: Biotechnology Laboratory, School of Chemical Engineering, National Technical University of Athens, 9 Iroon Polytechniou Str, Zografou Campus, Athens, 5780, Greece. tpaschos@central.ntua.gr.
authors.forename: Thomas
authors.initials: T
authors.lastname: Paschos
authors.affiliation: Industrial Biotechnology, Department of Chemical and Biological Engineering, Chalmers University of Technology, Kemivägen 10, Gothenburg, 41296, Sweden. xiros@chalmers.se.
authors.forename: Charilaos
authors.initials: C
authors.lastname: Xiros
authors.affiliation: Biochemical Process Engineering, Division of Chemical Engineering, Department of Civil, Environmental and Natural Resources Engineering, Luleå University of Technology, Luleå, SE-971 87, Sweden. paul.christakopoulos@ltu.se.
authors.forename: Paul
authors.initials: P
authors.lastname: Christakopoulos
mesh_terms: D056804:Biofuels; D001709:Biotechnology; D000431:Ethanol / Q000032:analysis / Q000302:isolation & purification / Q000378:metabolism*; D005285:Fermentation; D005670:Fusarium / Q000378:metabolism* / Q000502:physiology*
chemical_list: D056804:Biofuels; D000431:Ethanol