The Siege of Ligningrad

April 7, 2014 |


It’s a desperate siege, conducted in labs around the world— without overcoming the fortress known as lignin, the cost and complexity of making cellulosic biofuels rises, making profitability tough and financing tougher.

Now, a group of researchers may have found a breakthrough, in the form of a reengineering of lignin’s monomers and polymers.

It’s an axiom of revolutions that success flows from fatally weakening the regime you seek to overthrow — that the Bolshevik revolution was more fueled by breadlines and disaster on the battle fronts of WWI, than any abiding love of Bolshevism.

The axiom may well prove true in the biobased revolution as well — that success will flow from fatally weakening the bonds that bind the biomass you seek to deconstruct.

This is the premise of some remarkable work out of Michigan State and the Great Lakes Bioenergy Research Center, that appeared last Friday in Science — aimed at re-engineering lignin.

If you are late to the story of bioenergy, when I write “lignin,” you should think “Leningrad” or “Troy” or any city you can think of that has resisted a long, difficult siege. It’s a fantastically complex set of polymers that give wood and plants their structural strength, and has proven remarkably resistant to the pioneering deconstruction efforts of the bioeomomy’s leading scientists.

Ah, they’ve tried….

They’ve tried blasting it with acids, or teasing it with enzymes and ionic liquids. In most cases to date, scientists have opted to strip out the cellulose and hemicellulose and burn the lignin for process heat and energy. Others are gasifying the biomass — but that is energy-intensive.

The trouble is that lignin is built of complex set of polymers, and in turn those polymers are made of monomers with bonds that are fantastically tough to break.

So, no matter how fast a given biomass grows, how many tons per acre per year — there was the complexity of the conversion, and the cost, and the fact that aside from expensively gasifying the biomass there was no way to use up to a third of the mass, tied up as it was in lignin.

If you can’t blast it, change it.

But — why not use modern genetic techniques to insert a set of very weak bonds into a fast-growing biomass? Thereby replace a biomass tightly sewn together, with biomass fastened by a zipper.

Work was done on such a concept in the 1990s by University of Wisconsin-Madison professor and GLBRC Plants Leader John Ralph, who was then working at the U.S. Dairy Forage Research Center. According to notes from the University, “In the mid-1990s, Ralph’s group was looking for ways to reduce energy usage in the paper pulping process by more efficiently removing lignin – the polymer that gives plant cell walls their sturdiness – from trees. The group surmised that if they could introduce weak bonds into lignin, they could simply “unzip” this hardy material, making it much easier for chemical processes to break it down.”

Recently, a group of researchers at the Great Lakes Bioenergy Research Center applied the ideas to poplar — a fast-growing target feedstock for biofuels that prominently features in the partnership between ZeaChem and Greenwood Resources.

Michigan State University associate professor and GLBRC scientist, Curtis Wilkerson, said “By designing poplars for deconstruction, we can improve the degradability of a very useful biomass product. Poplars are dense, easy to store, and they flourish on marginal lands not suitable for food crops, making them a non-competing and sustainable source of biofuel.”

After Wilkerson found a gene capable of making monomers with bonds that are easier to deconstruct, University of British Columbia professor Shawn Mansfield successfully inserted the gene into poplar.

Popular with poplars

The results were a pleasant surprise. Not only did the poplars manufacture the monomers, the trees successfully incorporated them into their lignin.

“We can now move beyond tinkering with the known genes in the lignin pathway to using exotic genes to alter the lignin polymer in predesigned but plant-compatible ways, essentially ‘designing lignin for deconstruction,” Ralph says. “This approach should pave the way to generating more valuable biomass that can be processed in a more energy efficient manner for biofuels and paper products.”

The research is also noteworthy for being the direct result of a collaboration funded by the Great Lakes Bioenergy Research Center, one of three U.S. Department of Energy-funded Bioenergy Research Centers created to make transformational breakthroughs in new cellulosic biofuels technology.

This technology is also available for licensing.

“We’re excited about commercializing this breakthrough technology that will more efficiently allow biofuels and other products to be produced from poplars,” says Leigh Cagan, the chief technology commercialization officer at Wisconsin Alumni Research Foundation, available via [email protected]

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