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Evaluate antimicrobial and proteolytic activity of enterococci isolated from fermented products.

Enterococci occur and grow in a variety of fermented foods. The presence of enterococci in food products has long been considered an indication of poor sanitary conditions. On the other hand, fermented foods containing enterococci have a long history of safe use. Enterococci also may play an important role in the development of the organoleptic properties of fermented foods. Furthermore, many enterococcal strains have interesting biotechnological traits, such as bacteriocin production, and functional probiotic properties.

During the last few years, however, this view has been changing because of the increasing incidence of enterococci in nosocomial infections, and the widespread occurrence of antibiotic-resistant enterococci, especially in hospital environments. Many studies have consistently found vancomycin-resistant enterococci in clinical human samples, in animal samples, as well as in foods. Their ubiquitous nature determines their frequent finding in foods as contaminants. In addition, the notable resistance of enterococci to adverse environmental conditions explains their ability to colonize different ecological niches and their ability to spread within the food chain through contaminated animals and foods.

The bacteriocin production and proteinase activity of natural isolates of enterococci may be of interest to processors of dairy and meat-fermented products. A collection of 26 enterococci isolated from dairy and meat products were tested for antimicrobial and proteolytic activity by Serbian scientists. They found that E. faecium and E. faecalis were the most frequent species among tested enterococci. Of these, 11 isolates produced antimicrobial compounds. Ten of 11 enterococci-synthesized enterocins had antimicrobial activity against foodborne pathogens, such as L. monocytogenes and S. aureus.

The broadest spectrum of antimicrobial activity was detected in E. faecalis BGPT1-10P and BGPT1-78. E. faecalis BG221 had antimicrobial activity that was not related to the production of enterocin, hydrogen peroxide or organic acid. Twenty-five enterococci showed strong or moderate proteolytic activity towards casein. Two isolates, BGPT1-10P and BGPT1-78, showed the most intense hydrolysis of some casein fractions, total casein as well as gelatin. Extracellular BGPT1-10P and BGPT1-78 proteinases have a molecular mass of about 29 kDa.

Further information. Katarina Veljovic, Laboratory for Molecular Genetics of Industrial Microorganisms, Institute of Molecular Genetics and Genetic Engineering, Vojvode Stepe 444A, P.O. Box 23, 11010 Belgrade, Serbia; phone: +381 11 3975744; fax: +381 11 3975808; email:
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Publication:Microbial Update International
Date:Oct 1, 2010
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