This beetle’s gut may hide clues to making better biofuels

Decaying wood doesn't make the most nutritious food, but the long-horned passalid beetle has evolved to make the best of it. The guts of this forest-dwelling insect are adapted to take tough plant materials, like lignin and cellulose, and transform them into hydrogen, ethanol, methane and other energy-rich biofuels.

In a new study, researchers at UC Berkeley and Berkeley Lab describe how the architecture of the beetle's gut — and the beneficial microbes that inhabit it — help the beetle carry out such a transformation. This knowledge could help scientists engineer more efficient systems for producing bioproducts in the lab.

“We brought together a team of experts and used advanced molecular biology tools, together with spectrometry and tiny sensors, to discover that the beetle's gut is made of up specialized compartments — each with a distinct microbiome — that work together almost like a factory production line, using unique biochemistry to turn the wood into food and fuel,” said Eoin Brodie, assistant adjunct professor of environmental science, policy and management at UC Berkeley and senior author of the paper, which appears Monday, March 11, in the journal Nature Microbiology.

“The key innovation that nature has provided here is a way to combine biochemical processes that are otherwise incompatible,” Brodie said. For example, some of the compartments are optimized to carry out reactions that require lots of oxygen, while others carry out reactions inhibited by oxygen.

“It turns out that the beetle's gut architecture, such as the length and thickness of its gut walls, has evolved to suit its microbiome so that specific metabolic processes are favored in different gut regions,” said Javier Ceja-Navarro, a Berkeley Lab research scientist and lead author of the paper.

The shape of the gut also prevents certain compounds, like hydrogen, from escaping. These compounds help propel the production of products like acetate, which is a critical energy source, not only for the beetle itself, but also for its offspring.

“This beetle and its microbes have worked out what scientists around the world are hurrying to optimize – how to efficiently turn woody plant biomass into biofuels and bioproducts,” Ceja-Navarro said.