Bioconversion and modification of lignin for the production of biopolymers

Lignin, one of the components of lignocellulosic biomass, has been traditionally viewed as a 'waste product' in paper and biofuel production. However, it offers many advantages for the production of renewable polymeric materials. Lignin can be used in the form of aromatic oligomers or monomers for substitution of petroleum-based materials. To make this possible, the lignin polymer must first be broken down and modified to become synthetic building block. A challenge is that lignin is noted for its high resistance towards chemical and biochemical degradation processes. Thus, it is desirable to develop new technologies that can bring about the successful conversion and modification of macromolecular lignin.

Currently, enzymatic methods are amongst the most promising and the aim of this study is to use different microorganisms for the conversion of lignin polymers. Although microbiological conversion of lignin is almost exclusive to fungi, more and more attention is being paid on bacterial strains which are also capable of digesting lignin-like aromatic compounds.

The main aim of this work is to identify potential enzymes and microorganisms capable of modifying organosolv lignin and any other lignin fractions generated as part of these studies. Fungal species (Trichoderma harzanium) as well as selected bacteria (Pseudomonas sp.) were grown in synthetic media containing lignin as a sole carbon and energy source and the broth was analysed for extracellular oxidative enzyme activities.  The selected enzymes were further used to study lignin functionalization in order to improve the suitability of these lignins for the synthesis of polyurethanes and resins.