How to transform seaweed into biofuel
Scientists at the University of Illinois have developed a variety of yeast that significantly accelerates the transformation of seaweed into biofuel. It’s a welcome development in an industry that wasn’t seeing much progress.
The new yeast assisted biofuel process is important to those outside of the Corn Belt said Yong-Su Jin, a University of Illinois assistant professor of microbial genomics and a faculty member in its Institute for Genomic Biology.
"The key is the strain's ability to ferment cellobiose and galactose simultaneously, which makes the process much more efficient," Jin explained.
Red seaweed is hydrolyzed for its fermentable sugars because it produces glucose and galactose.
However, yeast has a preference for glucose and it won’t consume galactose until the glucose is gone, which adds a substantial amount of time to the process.
The new technique hydrolyzes cellulose into cellobiose, a dimeric form of glucose; it then uses a newly engineered strain of Saccharomyces cerevisiae capable of fermenting cellobiose and galactose at the same time.
The team also brought a new sugar transporter and enzyme into the equation that breaks down cellobiose at the intracellular level. The outcome is a yeast that eats cellobiose and galactose in equivalent amounts at the same time, reducing the production time of biofuel from marine biomass in half.
The research was conducted with project funding from the Energy Biosciences Institute, and included team members Suk-Jin Ha, Qiaosi Wei, and Soo Rin Kim of the University of Illinois, Urbana-Champaign, and Jonathan M. Galazka and Jamie Cate of the University of California, Berkeley.
Jin had an interesting comparison for the discovery; he likened the previous process to a person taking first a bite of a cheeseburger, then a bite of pickle. The process that uses the new strain puts the pickle in the cheeseburger sandwich so both foods are eaten at the same time. Of course, fermenting both sugars at the same time also makes for a healthier yeast cell.
"It's a faster, superior process. Our view is that this discovery greatly enhances the economic viability of marine biofuels and gives us a better product," he added.
Biofuel skeptics wonder: Is seaweed a viable biofuel?
Well, Jin and his partners are utilizing a red variety (Gelidium amansii) that is very plentiful on the coast of Southeast Asia. In island or peninsular countries that don't have space to grow other biofuel crops (like corn), using seaweed as a basis for biofuels just makes good sense, he noted.
And biofuels made from marine biomass have a few advantages over fuels made from other biomass crops.
"Producers of terrestrial biofuels have had difficulty breaking down recalcitrant fibers and extracting fermentable sugars. The harsh pretreatment processes used to release the sugars also result in toxic byproducts, inhibiting subsequent microbial fermentation..."
Jin also gave two more reasons why seaweed should be used for biofuels. Marine biomass yields more biomass per unit area compared to terrestrial biomass. And the rate of carbon dioxide fixation is a lot higher in marine biomass, which makes it an attractive option for appropriation and recycling of carbon dioxide.