P103: Microbial preprocessing of different size fractions of switch grass using Phanerochaete chrysosporium

Plant biomass is heterogeneous in nature and requires processing to closely homogeneous fractions for use in the production of biofuels. Fractionation based on anatomical differences such as cobs, leaves and stems is known to show differences in sugar yields during enzyme hydrolysis. However, fractionation of switch grass into homogeneous portions is challenging due to its anatomy. Size partitioning is a potential process for obtaining homogeneous fractions of switch grass based on Glucan/( Lignin+Xylan) ratio. Switch grass, initially ground to 2’’ mesh size is partitioned into 3 fractions, with mesh sizes of >2 mm, 1-2 mm and <1 mm. Among the three fractions, >2 mm and 1-2 mm have similar Glucan/(Lignin+Xylan) ratios (1.3-1.5), while <1 mm size fraction have significantly (p<0.05) different Glucan/(Lignin+Xylan) ratio (0.9-1.1). Therefore, 2’’ size material was partitioned into two fractions, >1 mm and <1 mm mesh size and subjected to microbial preprocessing using Phanerochaete chrysosporium. The two fractions and the un-partitioned switch grass were subjected to preprocessing for 12 days and measured for enzyme activities, phenoloxidase, peroxidase, beta glucosidase, beta xylosidase and cellobiohydrolase every 3 days starting from the initial day. The two fractions and the un-partitioned switch grass did not possess phenoloxidase and peroxidase activity throughout the 15 day period. Beta glucosidase, beta xylosidase and cellobiohydrolase activities peaked on the 6^th day for >1 mm and are significantly higher than those of <1 mm fraction and un-partitioned switch grass. Therefore, fractions with significant difference in Glucan/(Lignin+Xylan) ratio have different enzyme activities during microbial preprocessing.