Carbohydrate-binding modules of fungal cellulases: Occurrence in nature, function, and relevance in industrial biomass conversion

Anikó Várnai, Miia R. Mäkelä, Demi T. Djajadi, Jenni Rahikainen, Annele Hatakka, Liisa Viikari (Corresponding author)

Research output: Chapter in Book/Report/Conference proceedingChapter or book articleProfessional

69 Citations (Scopus)

Abstract

In this review, the present knowledge on the occurrence of cellulases, with a special emphasis on the presence of carbohydrate-binding modules (CBMs) in various fungal strains, has been summarized. The importance of efficient fungal cellulases is growing due to their potential uses in biorefinery processes where lignocellulosic biomasses are converted to platform sugars and further to biofuels and chemicals. Most secreted cellulases studied in detail have a bimodular structure containing an active core domain attached to a CBM. CBMs are traditionally been considered as essential parts in cellulases, especially in cellobiohydrolases. However, presently available genome data indicate that many cellulases lack the binding domains in cellulose-degrading organisms. Recent data also demonstrate that CBMs are not necessary for the action of cellulases and they solely increase the concentration of enzymes on the substrate surfaces. On the other hand, in practical industrial processes where high substrate concentrations with low amounts of water are employed, the enzymes have been shown to act equally efficiently with and without CBM. Furthermore, available kinetic data show that enzymes without CBMs can desorb more readily from the often lignaceous substrates, that is, they are not stuck on the substrates and are thus available for new actions. In this review, the available data on the natural habitats of different wood-degrading organisms (with emphasis on the amount of water present during wood degradation) and occurrence of cellulose-binding domains in their genome have been assessed in order to identify evolutionary advantages for the development of CBM-less cellulases in nature.
Original languageEnglish
Title of host publicationAdvances in Applied Microbiology
EditorsSima Sariaslani, Geoffrey Michael Gadd
PublisherElsevier
Chapter4
Pages103-165
ISBN (Print)978-0-12-800260-5
DOIs
Publication statusPublished - 2014
MoE publication typeD2 Article in professional manuals or guides or professional information systems or text book material

Publication series

SeriesAdvances in Applied Microbiology
Volume88
ISSN0065-2164

Keywords

  • fungi
  • basidiomycetes
  • ascomycetes
  • brown rot
  • white rot
  • lignocellulose/biomass conversion
  • cellulases
  • carbohydrate-binding modules
  • adsorption
  • desorption
  • high substrate concentration

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    Várnai, A., Mäkelä, M. R., Djajadi, D. T., Rahikainen, J., Hatakka, A., & Viikari, L. (2014). Carbohydrate-binding modules of fungal cellulases: Occurrence in nature, function, and relevance in industrial biomass conversion. In S. Sariaslani, & G. M. Gadd (Eds.), Advances in Applied Microbiology (pp. 103-165). Elsevier. Advances in Applied Microbiology, Vol.. 88 https://doi.org/10.1016/B978-0-12-800260-5.00004-8