Bifidobacterium longum. Source: The VisualMD
Source: fscn.umn
By Sara Specht
It’s the same old story: while exploring the wilds of
a jungle, a scientist stumbles upon a miracle cure. Only this jungle is much
closer to home—the flora of the human gut. And this stunning discovery just
might bring a super-preservative to local grocery store shelves.
It all started because Daniel O’Sullivan, a researcher
in the Department of Food Science and Nutrition, wanted to know why Probiotic
bifidobacteria seem to become toothless when they are fermented for use in
foods like yogurt. Probiotics naturally reside in the flora of the human large
intestine and help fight harmful bacteria to keep the gut healthy. O’Sullivan
mapped the genome of a human-grown sample of Probiotic Bifidobacterium longum
and discovered that it was actually bigger than a lab-cultivated specimen.
“They say the lion rules the jungle, and it’s very
well suited to doing that. In evolutionary terms, if you take the lion out and
raise it in a house, it becomes a pussycat,” O’Sullivan says. “That’s what we
saw happen when we took the Bifidobacteria out of the jungle in the gut and put
it in a nice pure culture and pampered it. It lost its claws.”
In this case, the Bifidobacteria loses chunks of DNA
that it no longer needs to compete in a pure culture. One of those lost pieces
is a previously unknown anti-microbial lantibiotic called bisin. Lantibiotics naturally
combat foodborne pathogens, and some are commonly used as food preservatives.
But while other lantibiotics kill only gram-positive bacteria, bisin is the
first discovered that can protect against both those and gram-negative
bacteria, like E. coli and Salmonella: the sources of over half of the United
States’ food recalls every year. Bisin apparently fights these bacteria so
effectively that treated foods could last almost indefinitely.
As a naturally occurring peptide, bisin doesn’t pose
the health risks that chemical food preservatives can, and it has already been
characterized as safe for consumption. And since bisin is chemically related to
a lantibiotic preservative already in widespread use, nisin, O’Sullivan says
the processes are already in place to apply it to food ingredients.
Professor Dan O´Sullivan in his laboratory.
There is one last barrier to getting bisin onto the
market—getting bifidobacteria to produce it anywhere other than the intestinal jungle. O’Sullivan is back in the lab trying
to understand on a molecular level how to induce bisin production in a
laboratory or industrial fermenter. He says once they learn how to flip that
switch, it will be ready to be licensed and put on the market.
“This is a very stubborn bug,” O’Sullivan
says. “We know how to switch on production of bisin, but then it switches
itself off. If we can get rid of that stubborn off switch, bisin has a lot of
potential as an antimicrobial tool for food safety and maybe pharmaceutical
applications.”
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