In order to explain why the enzymatic hydrolysis will be promoted by the exogenous addition of soluble lignin, a layer of immobilized cellulase on QCM and SPR sensors was constructed and then used as a sensor to probe the interactions between cellulase and soluble lignin. Initially, a layer of cellulase molecules was immobilized on QCM and SPR sensors in situ and in real time. The process was monitored and therefore the information about the immobilized cellulase film could be extracted from these data. According to the Sauerbrey equation, the adsorption capacity of cellulase on the gold chip is about 8 mg/m2, which is equivalent to the thickness of the film about 5 nm, whereas this thickness of cellulase on gold sensors of SPR was assessed to be above 15 nm. Then, soluble lignin solution was injected in the system and the interactions between cellulase and soluble lignin were recorded. In the course of lignin injection, the frequency of QCM monitoring did not change much, but the energy dissipation value rose sharply from -55×10<sup>-6</sup> to about -40×10<sup>-6</sup>. It can be seen from the signal that the adsorbed lignin membrane is very soft and cannot meet the calculation requirements of the Sauerbrey equation at all. As comparison, the SPR angle was shifted by about 0.3° due to the adsorption of lignin. That is to say, according to the equation, the thickness of the layer of lignin is about 5.5 nm. The results showed that soluble lignin could interact strongly with the immobilized cellulase. At last, buffer solution was injected to the system and part of immobilized cellulase was released since the signals of either QCM or SPR was even lower than those before soluble lignin loading. This cellulase liberation effect due to the soluble lignin addition may take part of the responsibilities of the enzymatic hydrolysis promotion by the exogenous addition of soluble lignin.

To understand the enzymatic hydrolysis efficiency promotion by exogenous addition of soluble lignin through the interactions between cellulase and lignin unveiled by QCM and SPR

2019 Spring National Meeting

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