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Cutting the cost of ethanol

Researchers devise a way to reduce the amount of enzymes needed to convert biomass into biofuels

Biofuels like ethanol could get cheaper if new research from Rutgers and Michigan State universities holds up.

Scientists there have demonstrated how to design and genetically engineer enzyme surfaces so they bind less to cornstalks and other cellulosic biomass, reducing enzyme costs in biofuels production, according to a study published in the journal ACS Sustainable Chemistry & Engineering.

“The bottom line is we can cut down the cost of converting biomass into biofuels,” said Shishir P.S. Chundawat, senior author of the study and an assistant professor in the department of chemical and biochemical engineering at Rutgers University.

Typically, the enzymes tapped to help turn switchgrass, corn stover and poplar into biofuels amount to about 20 per cent of production costs, said Chundawat. Enzymes cost about 50 cents per gallon of ethanol, so recycling or using fewer enzymes would make biofuels more inexpensive.

“The challenge is breaking down cellulose (plant) material, using enzymes, into sugars that can be fermented into ethanol,” he 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 fibres. But lignin inactivates enzymes that bind to it, hampering efforts to reduce enzyme use and costs, according to Chundawat.

The researchers showed how specially designed enzymes can limit their binding to and inactivation by lignin.

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