バイオエネルギー分野の研究者が、より優れたバイオ燃料処理のための遺伝子経路を発見(Bioenergy scientists discover genetic pathway for better biofuel processing)

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2022-03-09 オークリッジ国立研究所

オークリッジ国立研究所のバイオエネルギー革新センター(CBI)の研究チームは、植物におけるリグニンの形成を促進する経路を発見し、持続可能なジェット燃料などの製品用に栽培された作物の処理を容易かつ低コストにできる可能性があることを明らかにしました。

Richard Dixon is Distinguished Research Professor at the University of North Texas BioDiscovery Institute. Credit: University of North Texas

Chunlin Zhuo is a postdoctoral researcher at the University of North Texas BioDiscovery Institute. Credit: University of North Texas

A team of researchers working within the Center for Bioenergy Innovation (CBI) at Oak Ridge National Laboratory has discovered a pathway to encourage a type of lignin formation in plants that could make the processing of crops grown for products such as sustainable jet fuels easier and less costly.

The researchers focused on C-lignin, a polymer in the seed coats of certain exotic plants. Lignin, the polymer that gives plants their rigidity, is a good source of the building blocks and aromatic chemical compounds needed to produce clean bio-based fuels. But lignin is also difficult to process, particularly the more common G- and S-lignins found in most plants.

C-lignin has a chemical structure that is more linear than the other lignins, making it easier to deconstruct. The scientists working as part of CBI, a U.S. Department of Energy Bioenergy Research Center, have now identified the genetic mechanism at play in the formation of this preferred C-lignin, as detailed in Science Advances. The scientists hope to engineer bioenergy crops to form C-lignin while constraining the growth of G/S-lignins, which could lead to more affordable, higher-yield bioprocessing.

The G/S lignins form polymer structures much like a fishing net with branches and kinks in it, while C-lignin is more of a string, explained Jerry Tuskan, CBI’s chief executive officer at ORNL. “You can imagine that it would be harder to pull apart a fishing net than a string that just unravels.”

Moving forward, Tuskan said the researchers want to engineer this polymer into their primary feedstocks of poplar trees and switchgrass as a means of making their cell walls easier to break down for conversion into sustainable aviation fuels.

The University of North Texas’ BioDiscovery Institute, a CBI partner and lead institution for the project, has been studying C-lignin for some time, since university researcher Fang Cheng first discovered the polymer’s presence in the seed coats of the vanilla bean in 2011.

“How do you make C-lignin in a plant that doesn’t normally make it?” asked Richard Dixon, Distinguished Research Professor of biological sciences at UNT. “We’ve been approaching this in two ways. One of them is sort of trial and error and making some guesses — putting it in the plants that don’t naturally make it and seeing what happens. The other is trying to really understand how C-lignin is made in a plant that does naturally make it.”

Scientists observe complete switch to C-lignin

Chunliu Zhuo, a postdoctoral scholar at UNT, recently made a new discovery about how plants make C-lignin while studying the cleome, or spider plant. Cleome makes G-lignin in its seed coats for about the first 12-14 days after pollination. Then it switches to making only C-lignin.

“You would imagine if cleome is switching from G-lignin to C-lignin at some point it might make mixed GC-lignin,” Dixon said. “It doesn’t. It’s pretty remarkable. It just switches completely.”

At ORNL, a team led by Tim Tschaplinski in the Biosciences Division informed the research with an analysis of C-lignin formation at the molecular level.

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