MIT researchers develop a method to make biofuels from nonfood feedstocks

One alternative biofuel that's been around for a long time is ethanol. It is often made from corn and is mixed into gasoline in most gas stations all around the country. The problem with using ethanol to make fuel is that corn is a feedstock. Researchers at MIT have now discovered a way of boosting the production of biofuels like ethanol using nonfood feedstocks.

Feedstocks like straw and woody plants are difficult to use for biofuel production because they must first be broken down to fermentable sugars. That process produces numerous byproducts toxic to yeast, which is the microbe most commonly used to produce biofuel. The team at MIT developed a way to circumvent that toxicity making it feasible to use alternative sources that are much more plentiful for producing biofuels.

The researchers were also able to show that the tolerance can be engineered into strains of yeast used to manufacture other chemicals. This opens the door to using "cellulosic" woody plant materials as a source for producing biodiesel or bioplastics. About 40 percent of all corn grown in the US goes into ethanol production, but corn is a primary food crop.

Growing corn also requires a great deal of water and fertilizer to produce. Due to that fact, plant material known as cellulosic biomass is viewed as an attractive and noncompeting source for innumerable fuels and chemicals. That type of biomass includes many types of straw, and parts of the corn plant typically go unused. MIT says that could amount to more than 1 million tons of material per year which is enough to substitute for between 30 and 50 percent of the petroleum used for transportation.

To overcome the generation of compounds called aldehydes that are very reactive and kill yeast cells, MIT built on a technique previously developed to improve the tolerance of yeast cells to a range of alcohols which are typically toxic to the yeast in large quantities. Researchers engineered yeast to convert the cellulosic byproduct aldehydes into alcohols, which allows them to take advantage of the alcohol tolerance strategy developed previously. When the team expressly top-performing enzyme and spiked the reactor with a membrane-strengthening additive, the strain more than tripled its cellulosic ethanol production levels matching traditional corn ethanol.