The enzymatic hydrolysis is restricted by several factors related either to the physico-chemical structure of the lignocellulosic substrates or the efficiency of the enzymatic system. These potential bottlenecks have to be overcome in order to reduce the overall amount and costs of enzymes. Various chemical treatments and enzymes can be used to enhance the conversion of polysaccharides by hydrolyzing or modifying the residual polymers in the matrix.

To gain a better understanding on the factors structurally limiting the hydrolysis, the conversion of carbohydrate polymers was studied with the well-characterised Trichoderma reesei enzyme system. The chemical composition and the structure of the steam pretreated spruce substrate was modified with combinations of purified enzymes and analyzed with various analytical and spectroscopic methods. Especially X-ray microtomography revealed interesting morphological features of the substrate. These results will help to better understand and overcome the bottlenecks in the hydrolysis of recalcitrant plant biomass raw materials.