title: Impact of the supramolecular structure of cellulose on the efficiency of enzymatic hydrolysis.
abstract: BACKGROUND
  The efficiency of enzymatic hydrolysis is reduced by the structural properties of cellulose. Although efforts have been made to explain the mechanism of enzymatic hydrolysis of cellulose by considering the interaction of cellulolytic enzymes with cellulose or the changes in the structure of cellulose during enzymatic hydrolysis, the process of cellulose hydrolysis is not yet fully understood. We have analysed the characteristics of the complex supramolecular structure of cellulose on the nanometre scale in terms of the spatial distribution of fibrils and fibril aggregates, the accessible surface area and the crystallinity during enzymatic hydrolysis. Influence of the porosity of the substrates and the hydrolysability was also investigated. All cellulosic substrates used in this study contained more than 96% cellulose.
  
  
  RESULTS
  Conversion yields of six cellulosic substrates were as follows, in descending order: nano-crystalline cellulose produced from never-dried soda pulp (NCC-OPHS-ND) > never-dried soda pulp (OPHS-ND) > dried soda pulp (OPHS-D) > Avicel > cotton treated with sodium hydroxide (cotton + NaOH) > cotton.
  
  
  CONCLUSIONS
  No significant correlations were observed between the yield of conversion and supramolecular characteristics, such as specific surface area (SSA) and lateral fibril dimensions (LFD). A strong correlation was found between the average pore size of the starting material and the enzymatic conversion yield. The degree of crystallinity was maintained during enzymatic hydrolysis of the cellulosic substrates, contradicting previous explanations of the increasing crystallinity of cellulose during enzymatic hydrolysis. Both acid and enzymatic hydrolysis can increase the LFD, but no plausible mechanisms could be identified. The sample with the highest initial degree of crystallinity, NCC-OPHS-ND, exhibited the highest conversion yield, but this was not accompanied by any change in LFD, indicating that the hydrolysis mechanism is not based on lateral erosion.
authors: Department of Biology and Biological Engineering, Division of Industrial Biotechnology, Chalmers University of Technology, Kemivägen 10, Gothenburg, SE-412 96 Sweden.
authors: Ausra
authors: A
authors: Peciulyte
authors: Innventia AB, Drottning Kristinas väg 61, Stockholm, SE-114 86 Sweden.
authors: Katarina
authors: K
authors: Karlström
authors: Innventia AB, Drottning Kristinas väg 61, Stockholm, SE-114 86 Sweden ; Wallenberg Wood Science Center, KTH Royal Institute of Technology, Teknikringen 56-58, Stockholm, SE-100 44 Sweden.
authors: Per Tomas
authors: PT
authors: Larsson
authors: Department of Biology and Biological Engineering, Division of Industrial Biotechnology, Chalmers University of Technology, Kemivägen 10, Gothenburg, SE-412 96 Sweden ; Wallenberg Wood Science Center, Chalmers University of Technology, Kemigården 4, Gothenburg, SE-412 96 Sweden.
authors: Lisbeth
authors: L
authors: Olsson
keywords: Cellulose I; Cellulose supramolecular structure; Crystallinity; Enzymatic hydrolysis; Porosity; Solid-state cross-polarization magic angle spinning carbon-13 nuclear magnetic resonance (CP/MAS 13C-NMR)