Making Biofuels Cheaper Through Genetically-Enhanced Enzymes

Enzymes that are genetically engineered to avoid sticking to the surfaces of biomass may lower costs in production of biofuels. Source: Rutgers University In the U.S., gasoline typically contains up to 10 percent ethanol. Corn grain is the primary feedstock of ethanol, which results in a market that produces 15 billion gallons of ethanol a year.

In order to make biofuels like ethanol cheaper, researchers at Rutgers University and Michigan State University have demonstrated how to design and genetically engineer enzyme surfaces so they bind less to corn stalks and other cellulosic biomass, reducing enzyme costs in biofuels production.

"The bottom line is we can cut down the cost of converting biomass into biofuels," said Shishir P. S. Chundawat, an assistant professor in the Department of Chemical and Biochemical Engineering at Rutgers University-New Brunswick.

Enzymes typically help turn switchgrass, corn stover and poplar into biofuels at about 20 percent of production costs. They cost about 50 cents per gallon of ethanol, so recycling or using fewer enzymes would make biofuels cheaper.

"The challenge is breaking down cellulose (plant) material, using enzymes, into sugars that can be fermented into ethanol," Chundawat said. "So any advances on making the enzyme processing step cheaper will make the cost of biofuel cheaper. This is a fairly intractable problem that requires you to attack it from various perspectives, so it does take time."

Biomass contains lignin — an organic polymer that binds to and strengthens plant fibers — which activates enzymes that bind to it, hindering efforts to reduce enzyme use and cost. Researchers showed how specifically designed enzymes can limit lignin binding and inactivation -- ultimately lowering enzyme use and making it feasible for biorefineries to recycle used enzymes.

The full research can be found in the journal ACS Sustainable Chemistry & Engineering.