7-07: Availability of plant cell wall polysaccharides during sequential breakdown of wheat straw (Triticum aestivum L.).

Efficient utilization of wheat straw (Triticum aestivumL.) biomass requires thorough breakdown of the plant cell wall polysaccharides prior to fermentation. Normally this deconstruction is performed by hydrothermal pre-treatment and enzymatic hydrolysis. Cellulolytic enzymes are water soluble and require accessibility through open cell wall architecture and water sorption between the cellulose chains. Polysaccharide availability, cleavage, chain length and solubility all play crucial roles during enzymatic conversion.

In this study, the sequential breakdown and enzymatic availability of polysaccharides have been investigated in raw, hydrothermally pretreated, and enzymatically hydrolysed wheat straw.

The wheat straw material was divided into stem and leaf fractions before undergoing hydrothermal pre-treatment and subsequent enzymatic hydrolysis with Cellic CTec2 (Novozymes A/S) for 24 or 72 hours. The availability of various polysaccharides was investigated using the Comprehensive Microarray Polymer Profiling (CoMPP) technique. A novel five step sequential extraction series was employed to elucidate which polysaccharides become enzymatically accessible during the progressive degradation of the plant material.

The results indicate that hydrothermal pre-treatment releases significantly more xylooligomers from the cell wall matrix of leaves as opposed to stems where none were detected. During enzymatic hydrolysis, the available polysaccharides were digested in all the samples except for the raw leaves. An increase in xylooligomers was unexpectedly detected here. Structural features and possible mechanisms for the different dynamics during degradation will be discussed in this study.