Enzyme Mixtures & Synergistic Additives for Hydrolysis of ΑFΕΧ Treated Lignocellulosics Using Rapid Microplate Screening Method
Shishir Chundawat, Bruce E. Dale, and Venkatesh Balan. Chemical Engineering and Materials Science, Michigan State University, 2527 Engineering Building, East Lansing, MI 48824
Limited work in the past has been directed towards understanding the nature of synergy between cellulases, hemicellulases and other accessory enzymes on lignocellulosic substrates. This is partly due to the fact that much previous research has focused on acidic pretreatment technologies that remove hemicellulose in the pretreatment step itself. With increasing focus on alkaline or neutral pretreatments (i.e. AFEX-Ammonia Fiber Explosion Technology, ARP-Ammonia Recycle Percolation, LHW-Liquid Hot Water) the need to optimize enzyme systems that hydrolyze the glucans and xylans becomes critical. The microplate method is a rapid hydrolytic assay technique (essentially a scaled down version of the NREL LAP 009 procedure) developed at our laboratory to screen hydrolysis of lignocellulosic biomass using multi-enzyme systems. The microplate assay of lignocellulosic biomass is a more realistic assessment of enzymatic activity compared with conventional standard assays (i.e. filter paper activity) for biomass conversion. 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 are screening commercially available cellulases, xylanases and beta-glucosidases under a wide range of total enzyme concentrations for the hydrolysis of AFEX pretreated corn stover, poplar and switchgrass. Various additives such as surfactants (i.e Tweens, Triton-X) and extracted plant proteins (i.e. DDG and switch grass protein extract) are studied to enhance synergistic hydrolysis and prevent lignin terminal inhibition.