TOWARDS GREENER PROCESSING OF LIGNIN

Following two recent publications in Organic and Biomolecular Chemistry and Sustainable Chemistry, PhD student Daniel Miles-Barrett summarises his research on sustainable processing of lignin.

Following two recent publications in Organic and Biomolecular Chemistry and Sustainable Chemistry, PhD student Daniel Miles-Barrett summarises his research on sustainable processing of lignin.

Lignin, the second most abundant biopolymer on the planet, may soon become a highly reliable source of aromatic platform chemicals. To achieve this, the move away from old pulping processes to new lignocellulosic biomass biorefineries is already underway, aiming to utilise all components of the product and waste streams effectively. 

An important aspect to this move is the detailed understanding of the impact these new processes have on the molecular structure of the lignin from the lignin product streams. Work within the Westwood group (St Andrews) has focussed heavily on the characterisation of these new ‘technical lignins’ derived from whole biomass (Douglas fir and beech woods) using acidic-aqueous extraction techniques. We have developed an understanding of the structure of these lignins and shown how small variations in operating conditions can highly affect their downstream applications.

With detailed analyses in hand, our attention turned to strategies to utilise these new lignin streams. A strong held belief towards this effort is the usage of enzymatic processes to provide cheaper and safer alternatives to current chemical methods. The core issue is the lack of solubility of lignin as a substrate in an appropriate medium. Towards this, we have developed a highly selective method of functionalising technical lignins with water solubilising groups enabling very high solubility in water to be achieved (see Figure 1). Evidence has also been generated supporting the use of chemical transformations on this water-soluble lignin in water showcasing its potential applications in enzymatic reactions. Future work involves using these water-soluble lignin streams in enzyme-mediated processes to produce aromatic platform chemicals.

The research was published in RSC Organic and Biomolecular Chemistry - and ACS Sustainable Chemistry.

IB Impact : our method of processing sustainable feedstocks (lignocellulosic biomass) is one of many new reported ways that may prove vital in the shift from a fossil fuel based economy to a bio-based one. Our strategies have also included an outlook at downstream products derivable from our lignin streams and current plans are leading to incorporation of biocatalysts to integrate all areas of IB.