Past research on biomass conversion has focused on acid pretreatment technologies that remove lignin and hemicellulose in the pretreatment step itself. With increasing focus on Ammonia Fiber Expansion (AFEX) pretreatment the need to optimize enzyme systems that hydrolyze cellulose and hemicellulose becomes critical. Modifications in the ammonia recovery and pretreatment reactor systems that utilize low concentrations of aqueous ammonia allow significant cost reductions. However, with reducing severity of pretreatment it becomes important to re-optimize the enzyme cocktail to hydrolyze the pretreated biomass.

The automated 96-well microplate method is a rapid hydrolytic assay technique (scaled down version of NREL LAP-009 protocol) developed at our laboratory to screen optimum enzyme cocktails for hydrolyzing lignocellulosic biomass. Limited work in the past has been directed towards understanding the nature of synergy between cellulases, hemicellulases and other accessory enzymes on lignocellulosic substrates. Recent research has shown that choice of an appropriate enzyme preparation depends more on the characteristics of the substrate rather than on standard enzyme-activities measured.

We have screened commercially available cellulases, xylanases and other accessory enzymes under a wide range of total enzyme concentrations for the hydrolysis of AFEX pretreated corn stover and poplar.