Popa, senior vice president of new business development for BetaTec Hop Products in North America, tells EPM that many of the active compounds found in hops—more specifically, the same organic acids that make beer bitter—are known to have antimicrobial qualities. “It’s why breweries don’t have biological outbreaks,” explains Popa, who helped BetaTec introduce its flagship hop extract for ethanol production, a liquid product trademarked IsoStab, at the 2005 International Fuel Ethanol Workshop & Expo in Kansas City, Mo.
Now, after a period of extensive research and development, and a successful introduction of IsoStab in the U.S. market, BetaTec, a subsidiary of German-owned Barth-Haas Group, is working closely with its global ethanol industry customers to develop new and improved all-natural ethanol fermentation products. As Popa explains, controlling the formation of gram-positive bacteria is the name of the game for BetaTec—and doing it with natural products has big-time appeal for its new target customers.
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Natural bacteria buster
While most U.S. producers have learned how to effectively control bacterial contamination, it’s still one of the industry’s leading causes of ethanol yield reductions. It’s also a big drain on product quality. To be able to operate cost-effectively, it’s vital to control bacteria in ethanol fermentation. For some producers, this is commonly achieved by adding antibiotics as a processing aid during fermentation. However, rising concerns about the role of antibiotics for agricultural and technical applications—especially after the emergence of antibiotic-resistant bacteria—is creating a strong demand for safe, natural alternatives. “More and more ethanol producers are seeking to produce distillers grains that can be labeled ‘antibiotic free,’” explains Lilith Ruckle, BetaTec’s European ethanol project manager. “In the European Union, for example, if fermentation coproducts are used as animal feed, they must not contain residues of antibiotics. This law became effective at the end of 2005. Other nations have implemented similar laws and some believe the United States could eventually follow suit.”
In addition, Popa says more and more U.S. ethanol producers are trying to get away from drying distillers grains in order to cut costs. “With wet cake, the fear is that the product still might have antibiotics in it—particularly amoxicillin or virginiamycin—which goes right into the cattle feed,” Popa says. “Our product is an all-natural, kosher-certified, food-grade additive. … It’s very safe.”
During the manufacturing of fuel ethanol, bacteria contamination can occur in nearly every step of the process where water and starch are present at temperatures below 104 degrees Fahrenheit, Ruckle says. Since corn and other grain often pick up bacteria in the field, contamination generally originates from the starch material. Washing the grain helps lower the bacteria count, but bacteria contamination is essentially unavoidable. Ruckle says bacteria contamination is often found in yeast propagators, steep tanks, fermentors and heat exchangers, where the temperature, pH and glucose levels are ideal for bacteria growth. “Bacteria can grow nearly 10 times faster than yeast, so contamination in these areas becomes inevitable,” Ruckle explains.
To minimize bacteria contamination, most ethanol plants clean this equipment on a regular basis and run their processes at low pH levels. Many plants also try to perform their steeping, mashing and fermentation as quickly as possible to minimize lactic acid formation. Unfortunately, even low levels of bacteria reduce ethanol yield and, if severe enough, can slow or stop fermentation. Many batch ethanol plants use antibiotics daily to avoid bacteria problems; others use antibiotics when bacteria problems get severe. Continuous fermentation plants rarely use antibiotics, but they will if bacteria contaminations are high. If no antibiotics are used, it is common for a plant to experience a 1 percent to 5 percent loss in yield. For example, a 50 MMgy ethanol plant operating with a lactic acid level of 0.3 percent (weight-by-weight) is losing approximately 570,000 gallons of ethanol annually due to bacteria, according to Ruckle.
If it works for making beer …
Historically, six hops have been used in brewing, and over the past 40 years, the hops industry has developed into a high-tech ingredients supplier to the world’s leading beer makers. Hop companies like the former John I. Haas Inc., essentially the U.S. half of Barth-Haas Group (see pullout box), have come up with better, more effective hop extracts for brewing, identifying alpha and beta resins in hop cones. Hops are extracted with carbon dioxide, and much of the resulting carbon dioxide extract is further processed to separate the alpha acid fraction from the remainder of the hop extract. The alpha acids are then thermally isomerized into isoalpha acids formulated to exact specifications for ease of use and precise addition to beer. “From there, we have been able to get specific characteristics,” Popa says. “The brewers are getting so sophisticated now. For example, if they want a foam, we’ll add a specific entity. What this has done is, instead of using large amounts of hops, they’re concentrating on using lower amounts of hops to make the same amounts of beer.”
That’s good news for brewers, but not for growers and sellers of hops, Popa explains. So about five years ago, John I. Haas started looking at other industries to sell its hops products to. “The ethanol industry was a natural fit because what brewers do to make beer—or in the spirits industry, what they do to make rye-blend whisky—is basically what ethanol producers are doing,” Popa says. “We just had to be a little bit more creative in how we applied the product.”
Of course, there are key differences between beverage production and fuel ethanol production, so to determine which hop acids were the most effective at inhibiting the growth of bacteria common to fuel ethanol production, BetaTec tested all six acids extensively. The hop acids tested were alpha acid, beta acid, isoalpha acids, rho-isoalpha acids, tetrahydro-isoalpha acids and hexahydro-isoalpha acids. Lactobacillus brevis and Lactobacillus fermentum were the two bacteria BetaTec used for its testing and are the most common contaminants in fuel ethanol production.
The testing results are extensive and too detailed for the scope of this article, but what BetaTec essentially discovered is that by introducing minimum inhibitory concentrations of the right hop acids—the acids contained in IsoStab—into the ethanol production process, gram-positive bacteria growth can be stopped, leading to increased ethanol yields and, in some cases, allowing ethanol plants to avoid the use of antibiotics altogether. “IsoStab is very good at controlling gram-positive bacteria,” Popa says. “Most of your lactic acid bacteria is gram-positive. At the levels that we see our product in the plant, we’re usually not trying to get a total kill, or sterilize the bacteria. We are just trying to feed enough to control it. What we have found is that by feeding just enough to control the gram-positive bacteria, we can then set up a better environment for the yeast to grow faster, be more vital and actually produce alcohol faster. We control bacteria, so yeast can dominate.”
Producers pleased with results
In the past six months, BetaTec has had good commercial success with IsoStab in the U.S. ethanol industry, Popa says. The company is coming out with customer proof statements detailing how the product has been effective for a number of plants. “We’re seeing that where this product is working best is in corn mash that is resistant to virginiamycin,” Popa says.
In fact, experts say new antibiotic-resistant bacteria are emerging, something Popa and others are experiencing first-hand. “A year ago, we didn’t know about the resistance issue,” Popa says. “We’re just now collecting data on it, and it has been very interesting. Just about every mash sample I’ve pulled in the last six or seven months has a viginiamycin-, penicillin- or amoxicillin-resistant organism in it.”
Several U.S. ethanol producers are now using IsoStab daily and reportedly benefiting from it. “The producers we are working with are seeing an increase in alcohol production with less corn usage,” Popa says, adding that producers using IsoStab are also seeing fluctuations in ethanol yield tightening up. “Scientifically, we can’t say exactly why this is happening, but we have done yeast vitality studies, and it does seem that the yeast grow better in the hops material than they do in mash by itself or in mash with antibiotics. For lack of a better way to describe it, the yeast are simply happier.”
While IsoStab can replace the use of antibiotics altogether, Popa says it is generally used as part of a control regiment that might include antibiotics. “We’ve seen good results with that, where the bacteria won’t adjust to any one environment,” he says. “Every week or so, you change that environment so [bacteria] can’t adapt.”
Even though BetaTec’s introduction of IsoStab is still relatively novel, the company is wasting no time developing its next line of all-natural fermentation products. “I think IsoStab is an excellent product—certainly a great first product to have on the ethanol market—but we’re going to develop several new products and introduce them over the next 12 to 18 months,” Popa says. “We’d like to have a couple of all-natural products besides the hops-based materials that can be used in ethanol production.” EP
Tom Bryan is editorial director of Ethanol Producer Magazine. Reach him at tbryan@bbibiofuels.com or at (701) 746-8385.
