Enzyme discovery could boost biofuel production
EU-funded researchers have discovered a new family of enzymes able to break down wood into its chemical components. The findings may lead to more efficient production of biofuels and other valuable chemicals derived from biomass.
© mrmrsmarcha1 #176120693, 2018 fotolia.com
Wood is regarded as a promising source of raw materials that could one day replace oil not only for fuels but also for other petroleum-based products such as plastics. Glucose extracted from woody biomass is already used to produce advanced biofuels but the current processes are inefficient and make use of only part of the complex network of polymers that make up wood.
By studying a particular fungus, scientists in the EU-funded ZYBIOM project have discovered a family of enzymes that can double the amount of glucose extracted from wood. Although biofuels are the most immediate application, as their production from glucose is already well understood, the new enzymes could also have a part to play in the biorefining sector, which aims to replace oil-based products with materials derived from biomass.
In the case of biofuels, you want to target cellulose and some of it is quite easily accessible with enzymes, says investigator Marie Couturier. But some fractions are embedded in the complex lignocellulose matrix and you cant access those fractions. So the final yields are not very good. You need lots of different enzymes with complementary activities to target the recalcitrant fractions of wood. If you dont have all the enzymes in your cocktail then you wont be able to access all the fractions you want.
During the three-year project, Couturier and her colleagues, based at the National Institute of Agricultural Research (INRA) at Aix Marseille University in France, discovered a new class of enzymes that can break down more of the wood. They investigated a white-rot wood fungus known as Pycnoporus coccineus. This particular fungus is interesting because in nature we know that it grows on wood so it means that from wood it can recover everything it needs for its growth, Couturier explains.
The ZYBIOM scientists cultured the fungus in the presence of wood and analysed the enzymes that appeared in the culture medium. Out of the large range of well-known enzymes, some proteins without any predicted function attracted their attention.
We werent even looking for them, Couturier says. We were studying the enzyme cocktail from the fungus and then we identified this new sequence that matched nothing we knew.
Further investigation showed that the enzymes belong to a new family known as AA14 LPMOs. They target a particularly resistant constituent of wood known as xylan, which is related to cellulose. When the team added these AA14 LPMOs to a standard industrial cocktail of enzymes they found they could double the amount of glucose extracted from the wood.
Scaling up for industry
Couturier hopes they will be included in the next generation of enzyme cocktails for the production of biofuels from wood. This work is a key step towards using wood for biofuel and other products and will benefit biorefinery processes in the coming years, she says.
The laboratory results have yet to be scaled up to an industrial process but investigators have taken out patents on the new enzymes and negotiations are in progress on their commercialisation.
As a postdoctoral researcher at INRA, Couturier was supported by the EUs Marie Skłodowska-Curie fellowship programme to spend two years working on the project at the University of Toronto before returning to France for a further year. She is now a research scientist at the Centre National de la Recherche Scientifique in Grenoble.