LUCAN, MINN. - Ethanol companies are looking back to the monasteries of ancient Europe for one possible solution to a troublesome production issue.

They have to control bacteria to make good ethanol. The most common weapon, antibiotics, works well enough, but it's becoming a public relations headache.

This year, the Food and Drug Administration said it was finding antibiotic residue in an ethanol byproduct. That byproduct is sold as feed for cattle and other livestock, which is a problem. For the ethanol industry, the findings raised the threat of both bad publicity and government regulation.

That prompted ethanol producers to hunt for other ways to control the bacteria that impair ethanol production. Kerry Nixon, who manages an ethanol plant in central Minnesota, said industry insiders he talks with believe many plants have already started using hops, one of two main alternatives to antibiotics. The other method involves adding chlorine.

"They figure about 30 percent of the plants are either trying [hops] now or are already on it," Nixon said.

The hops alternative dates back more than a thousand years and is still very much in use today.

Hops have long been a staple ingredient for the beer industry. Beer maker Dustin Brau and his brothers have planted more than a thousand hops vines near their brewery in the small southern Minnesota town of Lucan.

Brau said hops -- which look like small, green pine cones -- do add flavor to beer, but he said they also have another benefit.

"The unique characteristic of hops is, it has antibacterial qualities," Brau said.

Brau said by reducing bacteria, hops is helpful in any sort of alcohol fermentation. Hops block bacteria that consume sugars in the mash. Left alone, the bacteria would turn the sugars into acid instead of what's really desired, alcohol. Legend has it that the monks of Europe's Middle Ages were the first to notice the value of hops.

And now, the ethanol industry is giving it a try.

"We've been extremely busy," said William Popa, national sales manager for a company that sells hops to the ethanol industry. "Since the first of the year we've had a lot of interest in our product."

Popa, who works for the BetaTec company, spends most weeks traveling interstate highways to different ethanol plants interested in trying hops.

"Most of the ethanol plants that we talk to are being very proactive and curious," he said. "The industry as a whole is changing, and anything that can help with production or efficiency they'll give it a shot."