The goal of this thesis was to study the suitability of different laccase enzyme variants for lignin modification and to survey the possibilities for commercial utilization of lignin. The client was Metgen Oy which produces tailored solutions for companies for biomass utilization in processed high value products.

In the experimental part different enzyme prototypes from various sources were studied by comparing the activity level of two model substrates to determine whether the activity of the model substrates correlates with the activity in lignin modification. The subjects of investigation comprised lignin radicalization, demethylation, depolymerization and repolymerization. As variables, process temperature, enzyme dosage and the amount of dissolved oxygen in the solution were deployed. Additionally, the suitability of the analysis methods selected for measuring the effects of the laccase enzymes was reviewed.

The experiments were made at laboratory scale in 125 ml Erlenmeyer flasks, from which the samples were collected at certain intervals for analysis. The samples were analyzed spectroscopically for the determination of demethylation and activity, and chromatographically for the detection of de- and repolymerization.

Information about the suitability of different enzyme variants for lignin modification was gathered as well as the effects of different process parameters on the structure, activity and particle size of the lignin in solution. In the literature survey also the properties of different lignin types were studied, and present and future possibilities for commercial utilization of lignin were surveyed.