Hydrolysis of crystalline cellulose is a crucial step in utilization of cellulosic biomass and is generally the bottleneck in the biochemical process. The combination of pre-treatment and the use of suitable enzymes is the key to effective saccharification, and ammonia pretreatment is a promising technique to enhance the velocity and yield in saccharification of crystalline cellulose. In the present study, we heterologously expressed recombinant cellobiohydrolase II from
Phanerochaete chrysosporium (
PcCel6A) in
Pichia pastoris. We then employed surface density analysis to compare the velocities of degradation of crystalline cellulose III
I, which was prepared from algal cellulose I by supercritical ammonia treatment, by the recombinant enzyme and
Trichoderma reesei cellobiohydrolase I (
TrCel7A). The hydrolytic velocity of crystalline cellulose III
I by
PcCel6A was approximately 4 times faster than that by
TrCel7A, though velocity of cellulose I degradation by
PcCel6A was almost half of that by
TrCel7A. Since adsorption of both enzymes on cellulose III
I is no more than twice that on cellulose I, we speculate that the enhanced hydrolysis of cellulose III
I by
PcCel6A than
TrCel7A is not simply due to the increased surface area, but also reflects higher accessibility of cellulose III
I to
PcCel6A.
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