Can Soy Be an Effective Antimicrobial Agent?

Antimicrobial properties, biocompatibility, and biodegradability of soy peptides could possibly make them an alternative to ineffective antimicrobials and antibiotics currently in use, according to a new study.

Current antibiotics in the gut kill bacteria indiscriminately, whether they’re pathogenic or beneficial, said study author Suresh Neethirajan, PhD, PEng, assistant professor in the School of Engineering, University of Guelph.

“You need beneficial bacteria in your intestines to be able to properly process food,” he said. “This is why a lot of antibiotics have digestive side effects like stomach cramps, diarrhea, bloating, gas, etc. Using soy isoflavones and soy-based peptides as food preservatives and antibacterial agents would reduce the amount of antibiotic compounds in the intestines, thus eliminating some of the health-issues associated with current antibiotics. In addition, soy-based peptides and soy isoflavones offer selective inhibition of bacteria, and being natural and biocompatible, there are no health implications.”

The researchers tested synthesized PGTAVFK and IKAFKEATKVDKVVVLWTA soy peptides against Pseudomonas aeruginosa and Listeria monocytogenes using a microdilution assay. They used microfluidic technology in combination with Surface Enhanced RAMAN Spectroscopy (SERS) and optical microscopy for rapid screening of soy peptides, pathogen identification, and to visualize the impact of selected peptides.

The PGTAVFK peptide didn’t significantly affect P. aeruginosa, although it had an inhibitory effect on L. monocytogenes above a concentration of 625 µM. IKAFKEATKVDKVVVLWTA was effective against both P. aeruginosa and L. monocytogenes above a concentration of 37.2 µM. High-throughput drug screening assays reduced the screening and bacterial detection time to 4 hours. They used SERS spectra to distinguish the two bacterial species.

"Current chemical antibiotics are not 100% effective, and there is a suspicion that they may not be competely safe for long-term human consuption or exposure," the researchers wrote.

"Extracting isoflavones and peptides from soy flour has the potential for creating a new, inexpensive, and safer method for antimicrobial use in food supplies."

-Mike Bederka

Reference:

Dhayakaran R, Neethirajan S, Weng X. Investigation of the antimicrobial activity of soy peptides by developing a high throughput drug screening assay [published online April 7, 2016]. Biochem Biophys Rep. doi:10.1016/j.bbrep.2016.04.001.