Development of artificial proteins for a better chemical use of wood

The biological degradation of biomass consists of a sequence of complex chemical reactions. The researchers aimed to describe this process as precisely as possible. By doing this, they wanted to identify new ways in which microbial catalysis can be used to turn wood into chemicals. This would make it possible to produce various chemical specialities without fossil oil in the long term.

More than 90 per cent of non-oceanic biomass is wood. Its potential for chemical syntheses has not been fully exploited so far because wood is not easily biodegradable.
Each year, lignified plants around the world produce approximately 100 billion tons of lignocellulose to support their structural framework. Land-based fungi and bacteria mineralise almost the same amount of biomass, thereby gaining energy and nutrients. Fungi, in particular, are able to transform hard biomass into soluble or gaseous products. However, the biochemical mechanisms of these degradation processes have not been studied closely enough and therefore cannot be used industrially so far.

Lignocellulose is not easily biologically degradable because its elements, the lignin polymers, are chemically very stable. In addition, only the surface of wood is accessible to enzymes. The project team constructed different artificial proteins and protein complexes and characterised their lignin-degrading activity. They were particularly interested in the question: How do lignin-degrading enzymes recognise the surface of a substrate? How does the behaviour of these enzymes change when they accumulate on the surface of a substrate? Can the artificial proteins help these enzymes to be more active?

The insights gained in this project should make lignocellulose a more accessible source for basic chemical substances. The development of suitable separation methods will make it possible to use wood as a comparatively cheap and renewable resource industrially in a number of new ways.

The researchers discovered a new mechanism by which enzymes activate molecular oxygen and use it to degrade strong chemical bonds such as the typical lignin bonds. They also developed a method to fix proteins to the surface of nanoscopic cellulose crystals. Such composite materials could replace fossil-based plastics in future.

Characterization and engineering of lignin: Protein interactions