Nanoparticle Boosts Antimicrobial Against Listeria

(The Busy Brain/Wikimedia Commons)

A researcher at Purdue University in West Lafayette, Indiana developed a nanoparticle that can hold and release an antimicrobial agent to extend the shelf life of foods susceptible to Listeria monocytogenes bacteria.

Listeria is a food-borne pathogen found in meats, dairy and vegetables. In mild cases, Listeria can cause diarrhea, but can advance to gastroenteritis or meningitis. Pregnant women, elderly, and those with weakened immune systems are particularly vulnerable.

Yuan Yao, a food science professor at Purdue, altered the surface of a carbohydrate found in sweet corn called phytoglycogen, which led to the creation of several forms of a nanoparticle that could attract and stabilize nisin, a food-based antimicrobial peptide. The nanoparticle can then preserve nisin for up to three weeks.

Nisin alone is only effective at inhibiting Listeria for a short periods in many foods, but many commercial environments have opportunities for contamination that require longer effective periods. At deli counters, for example, controlling Listeria is difficult because meat is continually being opened, cut, and stored, giving Listeria many chances to contaminate the food.

Yao used two strategies to attract nisin to the phytoglycogen nanopoarticles. First, he was able to negatively charge the surface of the nanoparticle and use electrostatic activity to attract the positively charged nisin molecules. Second, he created a partially hydrophobic or water-repellent condition on the surface of the nanoparticle, causing it to interact with partially hydrophobic nisin molecules. When the particles are hydrophobic, or repel water, they become attracted to each other.

A solution containing the nanoparticles and free nisin could be sprayed onto foods or included in packaging. The solution requires a balance of free nisin and nisin on the nanoparticles. Yao says reducing the amount of free nisin will trigger a release of more nisin from the nanoparticles to re-establish the equilibrium that preserves a substantial amount of nisin to counteract the Listeria.

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