300 million years ago, the Earth suddenly interrupted massive production of coal. This fact determined the end of the Carboniferous, a period of the Paleozoic Era that had started 60 million years before, characterized by the successive formation of large carbon beds arising from accumulation and burial of ancient trees growing up in vast marshy forests.

An international scientific team with participation of the Spanish National Research Council (CSIC) has found out that the end of this coal age coincided with the origin of a group of highly specialized fungi. The results, published in the last number of Science, indicate that these organisms developed a system for the efficient decay of the vast extent of plant biomass that had colonized terrestrial habitats.

"These ancient organisms, basidiomycete type fungi, had developed a mechanism based on enzymes capable of degrading a barrier extremely recalcitrant until that moment: lignin. This polymer, present in wood, provides strength and rigidity to the trees and makes vessels impervious enabling distribution of water and nutrients throughout the plant", explains one of the authors, CSIC researcher Angel T. Martinez.

Researchers have made this finding after comparative analysis of 31 fungal genomes. The study has allowed determining the mechanism that was employed by these fungi to degrade lignin.

"This process is based in the production of a type of complex proteins named peroxidases, acting in synergy with other oxidative enzymes. We managed to establish the evolutive pathway and chronology of the different types of peroxidases responsible for lignin biodegradation. Moreover, the results have revealed the existence of peroxidases barely known up to date", says Martinez, working at the Biological Research Centre of CSIC.

Novel biocatalysts
The enzymes found could be used in the future development of new industrial biocatalysts. The new enzymes will be expressed in model microorganisms and further purified, characterized and modified by protein engineering techniques.

"The same biological agents responsible for coal production decrease during the Carboniferous could nowadays allow us developing biotechnology tools aimed to the sustainable production of biofuels and other products from the renewable feedstock provided by plant biomass", points out CSIC researcher.

These studies will be carried out in the frame of the European Project PEROXICATS, coordinated by CSIC with participation of researchers from the Biological Research Centre (CSIC), the Institute of Natural Resources and Agrobiology (CSIC) and the Institute of Catalysis and Petroleochemistry (CSIC), amongst others. The project counts also with collaboration from a German university and two private companies.