Ethanol Production, Plagued by Yogurt Bacteria, Getting Viral Cure

by Elizabeth Summer (livescience.com/Phage Biocontrol, Inc.) The beneficial microbes that convert milk into yogurt and act in people's guts to promote digestive health cause big problems in ethanol fermentation tanks. When fermenting corn to create ethanol, lactic acid bacteria can contaminate the tanks and proliferate, inhibiting the growth of ethanol-producing yeast. The result is slowed fermentation and a reduced biofuel yields of as much as 20 percent per pound of input material, potentially shutting production.
The most common control measures- chemical antimicrobials such as antibiotics — do not eliminate the lactic acid bacteria. Additionally, the potential antibiotic residue left on the grains after fermentation turns away customers who would otherwise use the material as animal feed.
With support from the U.S. National Science Foundation (NSF), our company — Ecolyse Inc., based in College Station, Texas — is working to address this issue by developing products to treat bacterial contamination.
...
Over the years, yogurt manufacturers have experienced episodes of wide-spread lactic acid bacteria-culture death due to the activity of a virus that attacks the bacteria. The virus injects their DNA into bacterial cells, replicating inside, and then causing bacterial cell lysis (i.e., bursting) to release progeny phages (viruses).
...
Each type of virus, or phage, kills only one type of bacteria. This specificity makes the phages safe enough for human consumption; indeed, phages are present in many foods and natural environments. But this specificity also makes it challenging to find a suitable phage for a given situation.
...To identify the bacteria of concern, DNA is isolated from the raw material of interest (corn mash, in the case of ethanol production), and then a molecular screening technique, such as polymerase chain reaction (PCR) or DNA sequencing, identifies the bacteria.
The bacteria are grown in the lab, and then used as bait in what are known as "phage hunts." In a phage hunt, a culture of the bacteria is spiked with an environmental sample thought to contain phages. If any phage specific for that host bacteria are present, they will grow and multiply in the sample, increasing in concentration from about one particle per milliliter to over 10,000 particles per milliliter after a day or so. Once enough different kinds of phage are isolated, they can be grown in liquid cultures of host bacteria to make the large volumes needed for industrial treatment.
Ecolyse produces the phage as liquid lysates, the liquid "soup" consisting of cellular debris and phage particles that is created when a phage lyses (ruptures) a bacterial cell. They are best applied at the beginning of the fermentation cycle; like antibiotics, there is a window of opportunity for treatment.
A 10- or 100-fold reduction in lactic acid bacteria increases ethanol yields. An additional plus is that replacing antibiotics with phages during the fermentation process increases the marketability of the dried distillers-grain byproduct (the potential animal feed), which can be labeled as antibiotic free.
Developing phage products to control such bacteria during ethanol fermentation represents an attractive phage application in the larger picture of industrial microbiology...
...
This technology was funded through the NFS small business Innovation Research Program. This article was provided to CEP by the National Science Foundation. READ MORE