Plants provide potent antimicrobial extracts

Chemists and food scientists at Rutgers University in the US leveraged the antimicrobial ingredients found in a variety of plants to prevent the formation of difficult to remove biofilms of pathogens. Biofilms are a major problem at food manufacturing sites. Typically, a variety of bacteria will congregate on a surface to form a bacterial community that exists as a slime-like matrix biofilm. These colonies of pathogens form a tough surface skin that resist conventional commercial washing and sanitising methods and lead to food contamination and spoilage. This kind of bacterial community is often described as being polymicrobial, harbouring multiple versions of infectious, disease-causing bacteria, such as Salmonella and E. coli, the scientist stated in a preview of their research. The researchers studied natural antimicrobial agents derived from sources such as cloves, oregano, thyme and paprika to create new biodegradable polymers to potentially block the formation of bacterial biofilms on food surfaces and packaging. The researchers mated the natural substances with controlled-release, biodegradable polymers that could inhibit or prevent the formation of bacterial biofilms. The approach's main advantage was the ability of the materials to deal with diversity of the polymicrobial biofilms, a factor which makes them difficult to defeat. Each type of microbe presents a unique challenge to health and hygiene, said Kathryn Uhrich, professor of chemistry and chemical biology and an adviser to one of the researchers. "The natural substances we chose have general antimicrobial activities against many different kinds of microorganisms,"​ Uhrich said. "Therefore, the polymers into which we incorporated these natural substances have the potential to affect a much broader spectrum of microorganisms than organism-specific drugs." ​ Another advantage comes out of the decision to focus on the biofilms, rather than attempting to attack the individual bacteria, Uhrich said. The strategy avoids the potential of increasing the antimicrobial resistance of specific bacteria, an emerging problem in medical circles brought on by the overprescription of antibiotics An additional positive feature stems from the use of polymer "backbones" to which the natural agents were incorporated. The polymers are biodegradable due to their specific chemical composition and the nature of the bonds that hold them together, Uhrich said. As they degrade in the presence of water or enzymes, they slowly release their active antimicrobials. A slow and controlled release of the food-based antimicrobial would offer great advantages in the food industry, providing protection over an extended time and extending the shelf-life of the food product, the researchers stated. They suggest that shoppers may be more attracted to products containing natural antimicrobial ingredients rather than the synthetic chemical additives currently in use to protect against contamination and spoilage. "If consumers buy products containing our natural bioactives, they will benefit from all the positive factors that come along with our new strategy for food safety,"​ said Michael Chikindas, associate professor of food science at Rutgers and a co-investigator on the project. "They will be eating foods that are safer for longer periods of time; they will not be expanding antibiotic resistance; and they will not be adding to their bodies' synthetic chemical load."​ As a bonus, some of the antimicrobials carry some of the flavors and aromas of the sources from which they were derived. "The food people eat might even smell and taste better,"​ Chikindas said. The results of the Rutgers research will be presented at the American Chemical Society's meeting in Boston on 22 August.