Tuesday, May 3, 2011
Several groups have been looking to develop cellulolytic enzyme cocktails for specifically pretreated lignocellulosic biomass using high-throughput microplate based assays (Gao et al. 2010, Bioresour Technol 101(8):2770-2781). However, one of the major limitations of screening enzyme combinations using microplate assays is that these are typically carried out using finely milled biomass (<500 µm) at low solids loading (<3%, w/v). Both biomass particle size and overall solids loading are thought to influence the optimal combination of enzymes necessary for efficient hydrolysis to fermentable sugars. But this has not been precisely determined for low severity pretreated biomass (e.g., AFEX corn stover). In this study, three different harvest varieties of AFEX pretreated corn stover were hydrolyzed at 0.6-18% solids loading using multiple combinations of cellulases, hemicellulases and other accessory enzymes for extended hydrolysis time periods. Three particle size ranges were tested (<100 µm, <500 µm, >1 mm). We find that both particle size and solids loading can seriously impact the optimal combination of hydrolytic enzymes necessary for efficient hydrolysis.