Effects of non-ionic surfactants on the interactions between cellulases and tannic acid: a model system for cellulase-poly-phenol interactions |
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Authors: | Olsen S N Bohlin C Murphy L Borch K McFarland K C Sweeny M D Westh P |
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Institution: | a Roskilde University, NSM, Biomaterials, Universitetsvej 1, DK-4000, Roskilde, Denmark b Novozymes A/S, Krogshøjvej 36, DK-2880, Bagsværd, Denmark c Novozymes INC, 1445 Drew Avenue, Davis, CA 95618, USA |
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Abstract: | Addition of non-ionic surfactants (NIS) is known to accelerate enzymatic lignocellulose hydrolysis. The mechanism behind this accelerating effect is still not elucidated but has been hypothesized to originate from favorable NIS-lignin interactions which alleviate non-productive adsorption of cellulases to lignin. In the current work we address this hypothesis using tannic acid (TAN) as a general poly-phenolic model compound (for lignin and soluble phenolics) and measure the mutual interactions of cellulases (CBHI, CBHII, EGI, EGII and BG), TAN and NIS (Triton X-100) using isothermal titration calorimetry (ITC). The experimental results suggest rather strong enzyme-specific interactions with TAN in reasonable agreement with enzyme specific lignin inhibition found in the literature. Enzyme-TAN interactions were disrupted by the presence of NIS by a mechanism of strong TAN-NIS interaction. The presence of NIS also alleviated the inhibitory effect of TAN on cellulase activity. All together the current work provides strong indications that favorable NIS-poly-phenol interactions alleviate non-productive cellulase-poly-phenol interactions and hence may provide a mechanism for the accelerating effect of NIS on lignocellulose hydrolysis. |
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Keywords: | NIS non-ionic surfactants TAN tannic acid PCS pretreated corn stover CBHI cellobiohydrolase I CBHII cellobiohydrolase II EGI endoglycosidase I EGII endoglycosidase II BG beta-glycosidase PEG poly-ethyleneglycol CMC critical micelle concentration ITC isothermal titration calorimetry |
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