Tequila isn’t good for you, but the derivatives of this byproduct might be
Zinc-oxide nanoparticles are a ‘promising’ antibiotic with a waste-reducing source
Photo by Stan Shebs via Wikimedia Commons
Scientists at the Tecnológico de Monterrey in Mexico have found a surprising new use for tequila’s main ingredient: manufacturing zinc-oxide antibiotics.
In a paper published last May, the researchers heated, evaporated, and ground up a mixture of a zinc-based salt, water, and agave, the primary ingredient in tequila. The result was a grayish powder full of zinc oxide (ZnO) nanoparticles that were deadly to bacteria, confirming other scientists’ findings about the antimicrobial potential of plant-synthesized ZnO.
Now, the team is partnering with tequila companies to produce ZnO nanoparticles out of the shreds of pulp left from the tequila production process.
“We’re trying to show that there could be green methods that can be used to synthesize zinc oxide nanoparticles that keep these types of antibacterial properties,” explained Tecnológico de Monterrey Professor Marcelo Lozano, an author of the paper. By re-using agave pulp that would otherwise be discarded, Lozano hopes his project will give “some value to this waste” from tequila production.
Though scientists don’t know exactly how ZnO kills bacteria, one hypothesis is that the oxygen atoms in ZnO pull on the electrons of nearby atoms, wreaking havoc on lipids, proteins, and sugars inside bacterial cell walls. The other main hypothesis focuses on the potential toxicity of zinc to bacteria. Because of their positive charge, zinc ions create a charge imbalance on either side of a bacterial membrane, damaging the bacteria by disrupting their uptake of useful molecules and expulsion of harmful ones.
Size and shape are especially critical to implementing ZnO nanoparticle technology. “If you have enough surface in the particle, you can obtain better results because it’s exposed,” explained Tecnológico de Monterrey Professor Jackeline Iturbe-Ek, the second author of the paper.
Think of a bar of soap: the bigger and rounder it is, the more times you can wash your hands with the bar before it disintegrates. That’s because of the bar’s low surface-area-to-volume ratio: a lot of the soap molecules aren’t on the outside, so they can’t come off the bar when you wash your hands.
The equivalent idea is true for zinc-oxide nanoparticles: a smaller, more rod-like shape will allow a larger fraction of the atoms to split into ions and terrorize the bacteria. Agave, one of the three fruits that the Tecnológico de Monterrey team worked with in their original paper, produced some of the smallest ZnO nanoparticles known in the literature. This experiment alone, however, isn’t a strong enough reason for researchers to produce all ZnO nanoparticle antibiotics out of agave: according to some of the nanomedicine researchers consulted by The Tech, the size of the nanoparticles isn’t necessarily dependent on the source of the material.
Still, the research offers a potentially cheaper technique for manufacturing something that Iturbe-Ek described as “promising for new applications.”
In addition to its antimicrobial uses, ZnO nanoparticles with other shapes are a common active ingredient in sunscreen, reflecting UV rays to protect people’s skin. Scientists are also exploring how to use ZnO to purify water, produce clean energy, and even make cancer cells less resistant to medication.
Despite getting to purchase fresh tequila while visiting production facilities to collect agave samples, Lozano’s favorite part of the project was the opportunity to make ZnO production more affordable. “I try to have fun in the laboratory, [..] in the measurements, in the characterization,” he said. “[But] when you realize a potential application, you smile and you say, ‘I probably discovered particles and solved a problem for society.”