17-09: Effect of steam explosion pre-treatment on lignin structure and non-specific enzyme adsorption to lignin

Lignin is an inhibitory compound for the enzymatic hydrolysis of lignocellulosic biomass and a major underlying inhibitory mechanism is enzyme adsorption on the lignin-rich cell wall components. Biomass pre-treatment and the botanical origin of lignin give rise to differences in lignin structure and the impact of these differences for enzyme-lignin interaction was studied. Lignin was isolated from steam explosion (SE) pre-treated and non-treated spruce and wheat straw, it was chemically characterized and used for the preparation of ultrathin lignin model surfaces. Lignin-binding of Trichoderma reesei cellulases was monitored on-line using quartz crystal microbalance (QCM) technique. SE pre-treatment was found to alter the lignin structure and increased enzyme binding was observed on lignin films that had undergone the SE pre-treatment. Furthermore, the presence of SE pre-treated lignins resulted in stronger inhibition in hydrolysis studies compared to the non-treated lignins. Thus, we suggest that the positive matrix-opening effect of the SE pre-treatment may be compromised by chemical changes in lignin that lead to increased unspecific enzyme binding.