Diversa says that because its enzyme is derived from a heat-loving microbe, ethanol factories can operate at higher temperatures and under more acidic conditions, improving efficiency.

Some people in the biofuel industry question what the advantage is of having the enzyme in the corn rather than just buying the very similar amylase that Diversa is already selling.

Image Richard W. Hamilton and Richard Flavell of Ceres with switch grass plants. Credit... Ceres Inc.

While Syngenta’s corn is meant for industrial use in the United States, it is almost inevitable that some of it will get into human and animal food supplies, including exports, because of cross-pollination or seed intermingling. That is what happened in 2000 with Aventis CropScience’s StarLink corn, which was approved only for animal use, yet ended up in human food, forcing recalls and disrupting exports.

To prevent such liability, Syngenta is seeking approval of the corn for human and animal food use, not only in the United States but in Europe, South Africa and elsewhere. Syngenta says the amylase enzyme is safe, noting that these enzymes are found in saliva.

But Bill Freese of the Center for Food Safety, an advocacy group in Washington opposed to biotechnology crops, said that this particular amylase is from a little-studied exotic microbe and that some amylase induces allergy.

The Agriculture Department has asked Syngenta for more information on its application.

Regardless of what is done to corn, some experts say that starch alone will not provide enough ethanol. The new frontier is to produce ethanol from cellulose, the fibrous material in all plants. Cellulose is made of complex carbohydrates that can be broken down by enzymes into simpler sugars for fermenting into ethanol.