(482f) Effects of Dilute Acid Pretreatment On Cellulose DP and Factors Related to Cellulose Digestibility

Several chemical and physical factors have been proposed to be related to biomass recalcitrance. The degree of polymerization (DP) of cellulose has been considered to be one of the most important properties affecting the enzymatic hydrolysis of cellulose. However, there are few studies investigating the effect of pretreatment on cellulose DP in biomass and the relationship between cellulose DP and enzymatic hydrolysis. This study of the effect of dilute acid treatment on cellulose DP was first started with various pure cellulose materials. A substantial reduction in DP was found for all cellulosic materials studied even at conditions that would be considered relatively mild for the pretreatment.  Different cellulosic materials decreased to a similar DP upon treatment with acid regardless of the significant differences in the starting DP of the celluloses. The effect of dilute acid pretreatment on cellulose DP in biomass samples was also investigated. The cellulose DP in corn stover was also found to decrease greatly on acid pretreatment, however not to the extent observed with pure cellulosic samples. Acid pretreated corn stover was found to contain cellulose with DPw of 1600 - 3500, significantly higher than the DPw found with acid treated pure celluloses (150 – 300). The digestibilities of various acid-treated and untreated cellulosic and biomass samples with differing cellulose DP were tested with a cellulase complex (Genencor GC 220). Other cellulose properties, such as particle size and crystallinity were also monitored during digestions. There was little difference in the cellulose conversion for the treated and untreated celluloses despite their very large differences in DP. From this study it does not appear that cellulose DP is a main factor affecting cellulose saccharification. Other properties including particle size, xylan removal, pore volume etc., were also measured for the pretreated biomass samples. A statistical analysis was performed on all these factors to determine which were the most significant in determining cellulose digestibility.