Effects of non-ionic surfactants on the interactions between cellulases and tannic acid: a model system for cellulase-poly-phenol interactions.

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.