Tuesday, May 3, 2011
The degree of polymerization (DP) of cellulose is considered to be one of the important properties affecting the enzymatic hydrolysis of cellulose. However, there are few studies investigating the effect of pretreatment on cellulose DP and the relationship between DP and enzymatic hydrolysis. Various pure cellulose materials have been used in a study of the effect of acid treatment on cellulose DP. A substantial reduction in DP was found for all celluloses studied even at relatively mild pretreatment conditions. Celluloses with substantially different initial DPs decreased to a similar DP on acid treatment. These results agree with the fringe micellar model of cellulose microfibril structure that consists of sections of highly crystalline cellulose of approximately the same size separated by disordered regions. The effect of enzyme hydrolysis on cellulose DP was also studied. The digestibilities of various acid treated and untreated cellulose samples of differing DP were tested with a cellulase complex Genecor GC 220. In addition, other cellulose properties such as particle size and crystallinity were also monitored during digestions. There was little difference in the rates of cellulose conversion for the treated and untreated celluloses despite the very large differences in DP. The largest differences in cellulose conversion rates occurred at the start of the digestions, which is also when the most significant changes in cellulose properties occurred. From this study it does not appear that cellulose DP is a main factor affecting the rate of cellulose saccharification.