PLANT BIOMASS contains considerable calorific value – but a lot of it is tied up in robust cell walls, an evolutionary advantage that has helped grasses to survive foragers and prosper for more than 60 million years.

But for anyone seeking to release that energy, this robustness is a barrier to digestibility, whether in the rumen of cows and sheep or in bioenergy refineries for ethanol fuel.

But a multinational team of researchers, from the UK, Brazil and the US, has now pinpointed a gene involved in the stiffening of cell walls which can be suppressed to increase the release of sugars by up to 60%.

“The impact is potentially global as every country uses grass crops to feed animals and several biofuel plants around the world use this feedstock,” said Rothamsted plant biologist and team leader Rowan Mitchell.

“In Brazil alone, the potential markets for this technology were valued last year at $400 million for biofuels and $61million for forage cattle,” added Hugo Molinari, principal investigator at Embrapa Agroenergy, part of the Brazilian Agricultural Research Corporation and the team’s other co-leader.

Billions of tonnes of biomass from grass crops are produced every year, noted Ms Mitchell, and a key trait is its digestibility, which determines how economic it is to produce biofuels and how nutritious it is for animals. Increased cell wall stiffening, or feruloylation, reduces digestibility.

“We identified grass-specific genes as candidates for controlling cell wall feruloylation 10 years ago, but it has proved very difficult to demonstrate this role although many labs have tried,” she said. “We now provide the first strong evidence for one of these genes.”

In the team’s genetically modified plants, a transgene suppresses the endogenous gene responsible for feruloylation to around 20% of its normal activity. In this way, the biomass produced is less feruloylated than it would otherwise be in an unmodified plant.

“The suppression has no obvious effect on the plant’s biomass production or on the appearance of the transgenic plants with lower feruloylation,” she stressed. “Scientifically, we now want to find out how the gene mediates feruloylation. In that way, we can see if we can make the process even more efficient.”

The findings are undoubtedly a boon in Brazil, where a burgeoning bioenergy industry produces ethanol from the non-food leftovers of other grass crops, such as maize stover and sugarcane residues, and from sugar cane grown as a dedicated energy crop. Increased efficiency of bioethanol production will help it to replace fossil fuel and reduce greenhouse gas emissions.

“Economically and environmentally, our livestock industry will benefit from more efficient foraging and our biofuels industry will benefit from biomass that needs fewer artificial enzymes to break it down during the hydrolysis process,” said Mr Molinari.

For John Ralph, a pioneer in the field, the discovery has been hard won and is long overdue: “Various research groups ‘had the feruloylation protein/gene imminently’, and that was some 20 years ago,” noted the Professor of Biochemistry at the University of Wisconsin-Madison and at the US Department of Energy’s Great Lakes Bioenergy Research Center.

“Our group has been interested, since the early 1990s, in ferulate cross-linking in plant cell walls and developed the NMR methods that were useful in the characterisation here. This has been a tough one to discover.”