Cost-effectively overcoming the recalcitrant lignocellulose for releasing soluble sugars is the largest challenge for the emerging biomass refineries. The root causes of recalcitrant cellulosic materials are attributed to numerous factors such as substrate accessibility, degree of polymerization, and interference from lignin or hemicelluloses. Now cellulose accessibility to cellulase (CAC) is more accepted to be the most important cellulose characteristics. But how to determine crystalline and amorphous cellulose accessibility remains in debate and challenging.
Previously we have shown quantitative measurement of CAC for pure cellulose ¹ and also differentiated CAC from non-cellulose accessibility to cellulase (NCAC) for lignocellulosic materials ². In this work, we construct a new recombinant protein containing a red fluorescent protein and a family 17 cellulose binding module. Based on different adsorption specificities of various cellulose binding module families (CBM3 and CBM17), we have quantified amorphous cellulose accessibility to cellulase (aCAC) in pure cellulose and the changes of aCAC during cellulose hydrolysis. This study will present the first evidence whether amorphous cellulose is hydrolyzed before crystalline cellulose. Later, a more complicated functionally-based mathematic model will be developed to simulate and understand cellulose hydrolysis.

References:
(1)          Hong, J.; Ye, X.; Zhang, Y.-H. P. Langmuir 2007, 23, 12535-12540.
(2)          Zhu, Z.; Sathitsuksanoh, N.; Vinzant, T.; Schell, D. J.; McMillan, J. D.; Zhang, Y.-H. P. Biotechnol. Bioeng. 2009, 103, 715-724.