Novel enzymes can convert plant waste into fuel

Scientists have discovered a new family of enzymes which can make it possible to convert plant waste into sustainable goods and high value products such as nylon, plastics, chemicals and fuels.

The study, published in the journal Nature Communications, illuminates the way to reduce carbon dioxide emissions by providing an eco-friendly alternative to fossil fuels.

This new family of enzymes is active on the building blocks of lignin-one of the main components of plants- which scientists have been trying to break down since decades. Lignin acts as scaffolding in plants and is central to water-delivery. Lignin also provides strength and defence against pathogens.

"Enzymes are biological catalysts that can perform incredible reactions, breaking down some of our toughest natural and man-made polymers," said John McGeehan at the University of Portsmouth in the UK.

"To protect their sugar-containing cellulose, plants have evolved a fascinatingly complicated material called lignin that only a small selection of fungi and bacteria can tackle," McGeehan said.

"However, lignin represents a vast potential source of sustainable chemicals, so if we can find a way to extract and use those building blocks, we can create great things," he said.

The research team, which includes scientists from University of California in the US, has discovered a way of releasing a key bottleneck in the process of breaking down lignin to its basic chemicals.

The results provide a route to making new materials and chemicals such as nylon, bioplastics, and even carbon fibre, from what has previously been a waste product and reduces our reliance on oil.

"Using advanced techniques, from X-ray crystallography to advanced computer modelling; we have been able to understand the detailed workings of a brand new enzyme system," Sam Mallinson, a PhD student at University of Portsmouth.

The enzyme is a new class of cytochrome P450, and it is promiscuous, meaning that it's able to work on a wide range of molecules.

"This new cytochrome P450 enzyme can degrade a lot of different lignin-based substrates. That's good because it means it can then be engineered to be a specialist for a specific molecule and we can evolve it further to push it in a certain direction," said Gregg Beckham at the US Department Energy's National Renewable Energy Laboratory (NREL).

"We now have one of the most well-known, versatile, engineerable and evolvable classes of enzymes ready to go as a foothold for biotechnology to move forward and make the enzyme better," he said.