Tuesday, April 20, 2010
10-35

Quantitative analysis of enzyme adsorption during the hydrolysis of pretreated spruce

Anikó Várnai1, Liisa Viikari1, and Matti Siika-aho2. (1) Department of Applied Chemistry and Microbiology, University of Helsinki, P.O. Box 27, Helsinki, FI-00014, Finland, (2) Biotechnology, VTT Technical Research Centre of Finland, P.O. Box 1000, FIN-02044 VTT, Espoo, Finland

Lignocellulose is a promising raw material for biofuels. However, the production of lignocellulosic biofuels still needs improvement in order to be competitive with existing technologies. Enzyme costs may still make up one third of the total costs, which could be reduced by applying more efficient enzymes or by recycling of enzymes, both options leading to lower enzyme loadings.

To make the recycling process economically feasible, the enzyme adsorption should be reduced. After the hydrolysis, 60-80% of the enzymes remain bound to the residual substrate. The surface properties of the lignocellulosic substrate play an important role in the enzymatic hydrolysis. Due to the non-productive and irreversible adsorption of the enzymes to the lignin in the feedstock a decrease occurs in the overall enzyme activity. Diminishing the irreversible enzyme adsorption could reduce the amount of enzymes needed in the hydrolysis.

This work focused on the adsorption of Trichoderma reesei enzyme monocomponents on spruce samples with varying lignin content. Spruce samples were hydrolysed with a combination of purified enzyme preparations (i.e. Cel7A, Cel6A, Cel5A and Xyn11) complemented with purified Aspergillus niger β-glucosidase. The binding of individual enzymes was qualitatively and quantitatively followed during the hydrolysis to reveal the most critical enzyme components and to evaluate the effect of substrate characteristics on the adsorption of individual enzyme proteins.


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