Role of supramolecular cellulose structures in enzymatic hydrolysis of plant cell walls

Abstract

The study of biomass deconstruction by enzymatic hydrolysis has hitherto not focussed on the importance of supramolecular structures of cellulose. In lignocellulose fibres, regions with a different organisation of the microfibrils are present. These regions are called dislocations or slip planes and they are known to be more susceptible to various forms of degradation such as acid hydrolysis. Traditionally the cellulose within these regions has been assumed to be amorphous, but in this study it is shown by use of polarized light microscopy that dislocations are birefringent. This indicates that they have a crystalline organisation. Dislocations may be entry points for endoglucanases. Using a fluorescent labelled endoglucanase combined with confocal fluorescence microscopy, it is shown that the enzyme selectively binds to dislocations during the initial phase of the hydrolysis. Using a commercial cellulase mixture on hydrothermally treated wheat straw, it was found that the fibres were cut into segments corresponding to the sections between the dislocations initially present, as has previously been observed for acid hydrolysis of softwood pulps. The results indicate that dislocations are important during the initial part of enzymatic hydrolysis of cellulose. The implications of this phenomenon have not yet been recognized or explored within cellulosic biofuels.

Visualization of structural changes in cellulosic substrates during enzymatic hydrolysis using multimodal nonlinear microscopy

“…2). It has been shown in a previous study that during enzymatic hydrolysis pulp fibres preferably scission at dislocations, which have a typical distance of about 20 lm along the fibre (Thygesen et al 2011). It has been concluded from some studies that fibres derived from various sources were more hydrolysable at dislocations (BuschleDiller et al 1994;Clarke et al 2011;Gourlay et al 2015;Gurnagul et al 1992).…”

The Use of Carbohydrate Binding Modules (CBMs) to Monitor Changes in Fragmentation and Cellulose Fiber Surface Morphology during Cellulase- and Swollenin-induced Deconstruction of Lignocellulosic Substrates

“…It is possible that Swollenin targets the dislocations within lignocellulosic fibers, as these regions have been shown to be enriched in disordered/amorphous cellulose (21). Fiber dislocations (also called kinks, micro-compressions, irregularities, and slip planes (22)) have been observed in a range of plant species, including softwood, hemp, flax, and wheat (21,23,24).…”

“…Fiber dislocations (also called kinks, micro-compressions, irregularities, and slip planes (22)) have been observed in a range of plant species, including softwood, hemp, flax, and wheat (21,23,24). These dislocations are present in untreated biomass fibers and can also be induced during processing steps (25).…”

“…Dislocations have also been shown to contain more amorphous cellulose with less order than the surrounding fiber, likely due to the distortion of the crystalline cellulose microfibrils (26), although other work has suggested that microfibrils continue through these dislocations (27). Earlier work has suggested that these dislocations within the fibers make up weak points that are rapidly hydrolyzed by cellulases (21).…”

Development and testing of surface-based and water-based-diffusion kinetic models for studying hydrolysis and biogas production from cow manure

“…The diameter or particle size was assumed to be 162 reduced following first order kinetics. This assumption was based on reports suggesting that fiber 163 length in cellulose and ligno-cellulosic biomass initially undergoing rapid reduction before any 164 production of reducing sugars was observed during enzymatic hydrolysis ligno-cellulosic 165 biomass [5,6].…”