Prevention-Control Partnership

FROM THE MARCH ISSUE: A regimen of cleaning and antibiotics is vital for success in the fight against bacterial contamination. But the industry is evolving to include the use of more natural treatment options.
By Tim Albrecht | February 14, 2018

Bacterial contamination, specifically lactic acid bacteria, is a looming concern for ethanol producers and can reduce efficiency, lower yield and prompt costly repairs. Lactic acid bacteria produce various organic acids, including lactic and acetic. If those are present in a system, it’s a clear indication of a bacterial contamination, experts say. But proper sanitation and implementation of a rotational antibacterial control strategy can prevent contamination and the emergence of resistant bacterial strains. The first line of defense is a preventative strategy through basic plant maintenance and cleaning. 

Plant Hygiene
Perhaps the most important tool in an intensive plant cleaning is a caustic solution. When cleaning with a caustic solution, it’s vital to ensure it is the proper concentration and temperature, and is flowing through the system at the appropriate pressure and duration. Time and temperature are two of the four Ts of cleaning, along with turbulence and titration, says Tera Stoughtenger, technical services manager at Lallemand Biofuels & Distilled Spirits.

Lallemand has a designated hygiene audit team that will troubleshoot lactic-level problem areas for plants. “They’ll go in with the different instruments we have available and try to determine if there are any dead legs,” Stoughtenger says. “That’s one of the key things we look for, especially with plants expanding lately. It seems some pipes get missed and could end up with mash in them, causing bacterial contamination. We will grab samples and look at what type of, or how much, bacteria are present in dead legs, and different tanks and ports.”

Bacterial contamination can be caused by inadequate cleaning or impediments to process flow—such as heat exchanger blockages—and biofilms, among other issues. Sulfamic acid is commonly used as a solvent to clean heat exchangers and for removal of biofilms.

Routine review of all cleaning practices and associated equipment is recommended. “Checking equipment, such as spray balls in the fermenters, is a good idea to ensure they’re operating correctly,” says Stacey Campbell, ethanol technical services manager for BetaTec.

Hydrite Chemical Co. classifies plants in three groups—class one being extremely clean plants and class three being more challenging plants, says Allen Ziegler, a consultant to Hydrite Chemical. “No one likes to call their plant infected, but it can be, due to engineering designs or other reasons,” he says. “Some plants, depending on how they’re managed, are always going to be antimicrobially challenged.”

Staying on top of cleaning is also important from a financial standpoint, as procrastination in fixing issues could prove costly. In the past 20 years, Ziegler has encountered many customers who ended up paying more than $1 million for fixes, he says.

Secondary to cleaning is the use of antibacterial products, developed specifically to control bacteria in fuel ethanol plants. These products, each with a different function and area of activity, don’t affect the yeast when used at recommended doses.

Introducing antimicrobials into the propagators and fermenters during ethanol production helps inhibit bacterial contaminants, such as Lactobacillus, Acetobacter, Leuconostoc and Pediococcus. This helps reduce yeast stress and increase alcohol yields.

Lallemand offers a wide range of antimicrobial products, including Lactoside V and 247, Allpen Special and several varieties of bactenix, containing commonly used antibiotics Virginiamycin, penicillin, Streptomycin and Potassium Pen G. It offers a hands-on approach to its customer service and fermentation management, focusing on tailoring products to each customer’s plant, Stoughtenger says.

“We offer a large variety of antimicrobials that are used for both the gram-positive and gram-negative bacteria,” she says. “We can go in to collect samples and send them to our lab. The lab will specify which antibiotics would be best for the plant.”

Some plants shy away from antibiotics, over the debate about whether they trickle down the food chain via distillers dried grains with solubles, says Jason Lanham, director of sales for North America for BetaTec Hop Products. “We’re looking at consumers and the end users for coproducts going all the way down to the chicken farms that are buying the distiller grains ethanol plants are producing,” he says. “In some cases, you can even get premiums for antibiotic-free distillers grains.”

BetaTec has a line of nonantibacterial hops extract products that it says controls bacteria growth, while enhancing fermentation and improving quality of the yeast and ethanol. Its flagship product, IsoStab, controls gram-positive bacteria in the fermentation stage of ethanol production. Naturally occurring acids from the hops flower used to produce IsoStab are absorbed by the bacteria cell and lower its pH, Lanham says. This inhibits the cell’s ability to transfer glucose through the cell wall. In essence, bacteria commonly found in ethanol production are starved to death and they can’t reproduce, says Campbell.

Evolution and Innovation
With recent Food Safety and Modernization Act regulations in place to ensure the amounts of antibiotics used are safe for food consumption, chemical providers are required to evolve and innovate. Hydrite introduced a unique product called Defender that can be added to the ethanol production liberally without causing a regulatory problem, Ziegler says.

“The primary advantages in Defender is it’s effective against both gram-negative and gram-positive bacteria,” he says. “It can be used at a very high rate, unlike antibiotics, which have a GRAS (generally recognized as safe) of one part per million, while ours can be used at 173 (parts per million). Because you have a natural breakdown, you don’t have any carryover into the food chain.”

The company also has a new chemical based on sodium chloride—commonly known as table salt—for stronger, more infectious problems that might occur further downstream via the heat exchangers, Ziegler says. “Those are the two primary products we offer that aren’t the traditional Virginiamycin or penicillin. We’re looking at different platforms that are nonantibiotic-based.

Hydrite isn’t the only company looking to evolve. Lallemand recently acquired a company called Lactic Solutions LLC, which was cofounded by Jim Steele, general manager of Lactic Solutions. Steele developed a technology that has the potential to reduce use of antibiotics in the ethanol industry and increase yields, he says. “We isolate bacteria from the ethanol plant environment and we simply reengineer them to make ethanol instead of lactic acid,” Steele says. “In addition, we arm them to outcompete the normal contaminants that are present. We then use those lactic acid bacteria to reduce the production of lactate and other organic acids, and increase yields by using those less common carbohydrates the yeast tends not to use.”

Rather than sugars ending up in DDGS, where they have relatively low value, Steele’s technology would convert them to ethanol. Long term, Lallemand wants to reduce, or hopefully eliminate, the use of antimicrobials in the bioethanol industry, Steele says.

The idea came about when Steele and Lactic Solutions cofounder Jeff Broadbent were trying to construct lactic acid bacteria that would compete with the yeast as the primary ethanologen in bioethanol fermentation. They overheard colleagues at a U.S. Department of Agriculture meeting discussing the difficulties with lactic acid bacteria in bioethanol fermentation and the costs on the industry, Steele says.

“We left and talked about how we could take what we knew and redirect the technology toward what we’re doing now, which is enhancing yields and reducing antibiotic use,” he says. “It was one of those rare ‘eureka’ moments, that you only hear about.”

The product is still in development and Steele hopes to have something for the marketplace by the end of 2018.

Bacteria are constantly changing and technology has adapted to combat them. New enzymes and genetically modified yeasts are causing issues such as infections that have never been seen before, Ziegler says.

“When the industry started off, there were all kinds of problems but it learned to manage them, and then they seemed to pop up again with all these new products and technologies being introduced,” he says. “With a dual strategy of both CIP and using new chemistries in propagation and fermentation, we’re seeing pretty good results. It goes a long way to helping you manage that bacterial contamination.”

Author: Tim Albrecht
Associate Editor, Ethanol Producer Magazine