Topochemical kinetic mechanism of cellulase hydrolysis on fast-growing tree species. COST Action FP1105
2016
Valchev, Ivo | Yavorov, Nikolay | Petrin, Stoyko
Optimization of the lignocellulosic bioconversion by cellulolytic enzymes requires good knowledge of reaction kinetics. In the present paper, the investigations of the kinetics have been performed on the fast-growing tree species of poplar, paulownia, willow and black locust, which were pretreated by steam explosion (SE), and bleached kraft pulp (BKP) made of a hardwood mixture. The applicability of different kinetic equations referring to diffusion, topochemical and other heterogeneous catalytic processes was examined, and it was found that the enzyme process is best described by the modified Prout-Tompkins topochemical equation. According to that kinetic model, the hydrolysis rate depends on the amount of the substrate left and the inhibition of the enzyme by the product formed and, moreover, on the combination of chemical interaction and diffusion processes. There is a compensation effect between activation energy and pre-exponential factor and there are correlations between rate constant, power factor, and wood density. The mechanisms of cellulase hydrolysis of BKP- and SE-treated fast-growing tree species are very similar. The results shows that the structural features of the lignocellulosic material are the controlling factor on the type of the kinetic mechanism. The obtained temperature-time dependence of degree of enzyme hydrolysis is useful for simulation and control of the process.
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