The strengths and weaknesses of methods used to characterize the rate and extent of deconstruction of pretreated biomass substrates

Pretreatments for bioconversion must maximize the ease of enzymatic hydrolysis of cellulose while at the same time enabling the effective recovery and fractionation of hemicelluloses and lignin in a usable form.  To achieve these often contradictory goals, it is important to also be able to assess the “specific surface area” (SSA) of the cellulose at levels ranging from the macroscopic, cellular structure to the microfibril, nano-scale.  However, due to the heterogeneous nature of biomass those substrate characteristics which most influence changes in the SSA at various biomass/substrate structural levels still need to be fully elucidated. Past work which tried to determine the SSA of cellulose typically used techniques such as gas adsorption or solute exclusion. However, these methods are tedious, are generally performed on pure cellulose and in many cases involve drying the substrate. In the work that will be presented we will describe the development and application of SSA measurement methods ranging from those that have been adapted from the pulp and paper sector (i.e. fiber quality analysis, water retention value, Simons staining) to more recently developed methods employing cellulose binding domains specific for the crystalline and amorphous regions of cellulose. Steam and organosolv pretreated substrates will be used to illustrate how good hemicellulose and lignin recovery can be achieved while showing how the cascading influence of macroscopic changes in the biomass’s structural organization influences fibre characteristics which in turn effect cellulose accessibility.