Bacteria combating bacteria for food preservation

Brazilian and Argentinian researchers are seeking ways to enhance the nutritional value and safety of food products using microorganisms derived from the products themselves.

By Heitor Shimizu, in Buenos Aires

Agência FAPESP – Increasing the nutritional value of food products and enhancing food security using compounds produced by microorganisms present in the food itself are objectives of a group of researchers in São Paulo State. They are collaborating with colleagues in Argentina in order to broaden the results of their studies. The São Paulo group comprises scientists from the Food Research Center (FoRC), one of FAPESP’s Research, Innovation and Dissemination Centers (RIDCs). The researchers in Argentina are affiliated with the Reference Center for Lactobacilli (CERELA).

One of the results of the research has been successful utilization of bacteriocins to enhance the safety of queijo Minas, a mild white cheese enjoyed all over Brazil and very easy to make, said Bernadette Gombossy de Melo Franco, coordinator of FoRC and Full Professor at the Food & Experimental Nutrition Department of the University of São Paulo’s School of Pharmaceutical Sciences.

“Minas cheese is made by small producers throughout the country and there are many cases of contamination by Listeria monocytogenes. Our goal was to use bacteria already present in milk and select those that produce bacteriocins. We isolated these and put them back in the milk with the specific purpose of inhibiting multiplication of the pathogen in order to enhance the safety of this cheese. We achieved a similar effect in the production of goat’s milk,” Franco said in a presentation delivered at FAPESP Week Buenos Aires as part of a panel session on functional foods.

But what are these bacteriocins, which have attracted the attention of researchers and the food industry? “They’re polypeptides synthesized in the ribosomes of lactic acid bacteria. And they’re bactericidal or bacteriostatic, meaning they either kill microorganisms or inhibit their multiplication without killing them,” explained Franco, who is also Pro-Rector for Graduate Studies at the University of São Paulo (USP).

Lactic acid bacteria are microorganisms found in various environments and capable of converting sugars (carbohydrates) into lactic acid.

“This property can be exploited in various technological ways to increase the nutritional value or safety of food products. Lactic acid bacteria can have many other uses, too. For therapeutic purposes, for example, they can be used as vectors for a number of genes responsible for the production of many medically or chemically important compounds,” Franco said.

“Lactic acid bacteria are a very large group, comprising more than 200 different types of microorganism. They produce various compounds that can perform functional activities, meaning they add benefits to the food products that contain them. They may be enzymes, vitamins, exopolysaccharides, sweeteners, probiotics, or antimicrobial compounds.”

This antimicrobial activity is what interests researchers at FoRC and CERELA. “These antimicrobial agents, which can be used in both medicine and food preservation, are also numerous and varied. They range from organic acids to diacetyl, hydrogen peroxide, carbon dioxide, low molecular weight compounds, and above all bacteriocins,” said Franco, who is a member of FAPESP’s Engineering Committee and São Paulo State Science, Technology & Innovation Master Plan Steering Committee. She explained that lactic acid bacteria have been used as biological preservatives in food for millennia (since about 6,000 BCE) without identification of the chemical compound responsible for food preservation.

“An example of the practical application of bacteriocins in food preservation is control of the bacterium Listeria monocytogenes, a pathogen that causes various diseases, some less severe but others that can even lead to the death of an infected individual. It’s a psychrotrophic microorganism, meaning it can grow and multiply at low temperatures such as those found in refrigerators. It’s resistant to salt and disinfectant, and it can adhere to the surface of the equipment typically used by the food industry, forming biofilm and surviving for long periods in such environments,” Franco said.

New definition

According to the scientific definition of bacteriocins used since 1994, Franco explained, their activity is important only against other bacteria to which they are genetically related. This is where another contribution of the research done at FoRC comes in.

“We’re contributing information to show that this classification needs to be revised,” she said. “In an article published by our group with our Argentinian partners we show that bacteriocins are also active against viruses and yeasts.”

“We’ve also produced important results by encapsulating bacteriocins in lipid nanovesicles, which protects the bacteriocins from the action of the food matrix.” Their discoveries highlight the importance of research on bacteriocins and other compounds with functional activities. The potential applications are so numerous that interest is steadily increasing.

“There has been substantial growth in research on bacteriocins in recent years,” Franco said. “The number of scientific publications on the subject has increased sharply in Brazil and worldwide. However, we need more studies to extend our knowledge of the possible applications of bacteriocins in food preservation.”

“Of course, bacteriocins aren’t a panacea that will solve all food contamination problems. They’re one more tool that can be used together with other methods of food preservation. For example, their activity depends on the bacterial strain, on the food matrix they’re part of, and on environmental factors.”

In her presentation to FAPESP Week Buenos Aires, Franco also addressed the topic of a project conducted in partnership with researchers at Tucumán National University and CERELA.

In this project, selected in a call for proposals issued by FAPESP in partnership with CONICET, researchers are prospecting for lactic acid bacteria that synthesize vitamins in artisanal dairy products in Argentina and in Brazil for the development of functional foods enriched with folate and riboflavin.

Gluten-free bread

The panel session on functional foods, which was chaired by Maria Cristina Añon, a professor at La Plata National University, also included a presentation on the use of lactic probiotics in functional foods by Maria Taranto, a researcher affiliated with CERELA’s Department of Food Biotechnology.

Vanessa Dias Capriles, a professor at the Federal University of São Paulo (UNIFESP), spoke about the technological and nutritional challenges of making gluten-free bread. In a research project supported by FAPESP via the Young Investigators in Emerging Centers Program, she is endeavoring to develop gluten-free bread of high technological, nutritional and sensory quality “as a contribution to better diet, health and quality of life for people with celiac disease”.

Capriles said celiac disease is the most prevalent food intolerance worldwide and is driving demand for gluten-free products. “However,” she stressed, “gluten is an essential structural protein for baked products, so making bread without gluten is a technological challenge.”

The last speaker in the session was Daniel Barrio, a professor at the Rio Negro National University who delivered a presentation on bioactive peptides derived from food protein.

For more information about FAPESP Week Buenos Aires, go to: www.fapesp.br/week2015/buenosaires.