Biofilm beer research

Darla Goeres, a research professor in the Center for Biofilm Engineering at Montana State University, helps assistant Lindsey Lorenz drain a beer draught line on June 1 in preparation to test the tubing for biofilm build up.

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In Darla Goeres’ lab on the third floor of Barnard Hall at Montana State University, the beer on tap is Sierra Nevada Pale Ale.

But when it comes out of the keg with a frosty head, it’s not for drinking.

Instead, Goeres and her collaborators in MSU’s Center for Biofilm Engineering use the brew to study how to improve the taste of beer by finding ways to better remove taste-altering biofilms from the plastic lines that carry beer from keg to tap.

“When you get a beer and have a sip and think ‘that doesn’t taste right,’ it’s probably because of biofilm,” said Goeres, an associate research professor in the Department of Chemical and Biological Engineering.

The biofilm forms when harmless bacteria, brewing yeast and other residue form a coating on the inside of draught lines, she said.

The Colorado-based Brewers Association recommends beer distributors clean draught lines biweekly by flushing them with disinfectant and water, Goeres said. But knowing how often to clean the lines, and judging the results, can be a challenge.

“(The brewing community) wants actual data to support their recommendations and ultimately to improve the cleaning regimen,” she said. “The goal is to provide their customers with the highest quality beer possible.”

To study the biofilm, Goeres and her team partnered with local beer distributors to construct a lab system that mimics the draught systems commonly found in bars, complete with long sections of tubing.

“They helped us get all the parts and ensured we assembled the laboratory system properly,” she said. “They have also been great in troubleshooting any problems.”

The researchers then added specific strains of bacteria — ones that commonly cause the beer biofilm to form — into the draught lines coming out of the keg of pale ale, which was donated by Sierra Nevada Brewing Company. In a bar or brewery, the bacteria are introduced when couplers or other equipment aren’t totally clean when switching out kegs or tap handles, Goeres said.

The researchers flushed the beer through plastic lines of different sizes and materials. Then they closed the tap, unhooked the tubing and cut samples from each of the different tubing segments.

Lindsey Lorenz, who graduated from MSU in 2004 with a bachelor’s in microbiology and now works with Goeres as a research assistant, applies a stain to the tubing samples that causes the bacteria and yeast to light up under a laser microscope, allowing her to observe the structure of the biofilm’s components.

“Using the microscope allows us to see how the bacteria and yeast are interacting and forming biofilm in the tubing,” she said.

Kelli Buckingham-Meyer, a research assistant who earned her bachelor’s in microbiology from MSU in 1997, washes the other tubing samples in a sterile solution to remove the biofilm, then cultivates the biofilm bacteria on small plates by feeding them a beer-based food. When the bacteria grow and form colonies visible to the naked eye, she counts them.

“We can back-calculate the amount of biofilm in the tubing from that,” she said.

Lorenz and Buckingham-Meyer will present the research at the Montana Biofilm Science and Technology Meeting, to be held in Bozeman on July 18-20. The annual conference, hosted by the Center for Biofilm Engineering, brings members from the Center’s Industrial Associates program together with MSU faculty and speakers to discuss the latest biofilm research.

Goeres’ research is funded by the Brewers Association and is being conducted in partnership with NSF International, which specializes in public health standards and certification programs.

Within a year, Goeres and her team hope to publish their results, which could help in the development of new products or methods for cleaning draught lines.

“We’re able to take something that’s more complex than most people realize, bring it into the lab to understand what’s going on, and develop tools so that companies can come up with solutions,” she said.

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