Tuesday, April 20, 2010
8-69

Effects of liquid-ammonia treatment on crystalline cellulose: Changes in crystallinity index and enzymatic digestibility

Ashutosh Mittal1, Rui Katahira2, Michael E. Himmel1, and David K. Johnson1. (1) Biosciences Center, National Renewable Energy Laboratory, 1617 Cole Blvd., Golden, CO 80401, (2) National Bioenergy Center, National Renewable Energy Laboratory, 1617 Cole Blvd., Golden, CO 80401

Three cellulose samples with different degrees of polymerization (DP) and crystallinity indexes (CI) were treated with liquid ammonia under various conditions. From the X-ray diffractograms it was revealed that even under very mild treatment conditions (30 minutes of treatment time at a final temperature of 25°C) cellulose I was completely converted to cellulose IIII with no peak intensity at a 2θ value of 23. It was further observed that regardless of the liquid ammonia treatment conditions used and the cellulose used, the treatment produced very similar NMR spectra. Treatment at a final temperature of 140°C appeared to produce a slightly purer cellulose IIII material by decreasing amorphous content. The enzymatic hydrolysis results showed that the cellulose IIII samples obtained after liquid ammonia treatment were consistently more digestible than the starting celluloses which indicates that the liquid ammonia treatment of cellulose is able to convert cellulose into a more accessible and reactive form that is amenable to enzymatic hydrolysis.

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