COMBINATION WITH PLANT EXTRACTS IMPROVES THE INHIBITORY ACTION OF DIVERGICIN M35 AGAINST LISTERIA MONOCYTOGENES

Abstract

The susceptibility of 11 strains of Listeria monocytogenes to divergicin M35, a bacteriocin produced by Carnobacterium divergens strain M35, and to aqueous extracts of garlic, onion, oregano, red chili and black pepper at 30 and 10C, was evaluated using a microdilution assay. The susceptibility of divergicin‐resistant strains to combinations of these agents was also evaluated. Three strains were resistant to divergicin M35 (>500 µg/mL) at 30C but were more susceptible at 10C. Garlic gave the most inhibitory plant extract, followed by onion, while oregano, red chili and black pepper extracts were less active at both temperatures. Garlic extract and divergicin M35 combined or with other extracts increased inhibitory activity against the divergicin‐resistant strains. The garlic/divergicin combination was the most effective at inhibiting these strains and was bactericidal at both temperatures. Log‐phase cells were the most susceptible to the garlic/divergicin combination. Stationary‐phase cells were much more resistant at both incubation temperatures. Furthermore, the effect of the garlic/divergicin combination at inhibiting divergicin‐resistant L. monocytogenes in a food system was also studied using cold‐smoked salmon as a food model. Results indicated that this combination could efficiently reduce the viability of L. monocytogenes in smoked salmon stored at 10C. PRACTICAL APPLICATIONS There is increasing popularity worldwide for chemical preservative‐free, ready‐to‐eat and minimally processed seafood with low salt, fat and sugar content. Bacteriocins produced from lactic acid bacteria can have a potential application to prolong the shelf life of cold‐smoked salmon. Also, plant and spice extracts have been shown to contain antibacterial substances with potential for application in foods. Thus, this research explores the combination of divergicin M35, a bacteriocin produced by Carnobacterium divergens strain M35, and aqueous extracts of garlic, onion, oregano, red chili and black pepper to inhibit Listeria monocytogenes and to prolong the shelf life of cold‐smoked salmon.

Synergistic antimicrobial activity of galangal (Alpinia galanga), rosemary (Rosmarinus officinalis) and lemon iron bark (Eucalyptus staigerana) extracts

“…When there are more than two chemical compounds acting together as antimicrobials, they may exert multiple modes of inhibition on microbes, resulting in a reduced potential for the development of resistance to the antimicrobials 11. The use of plant extracts in combination with bacteriocins or with low levels of chemical preservatives may achieve efficient antimicrobial activity while overcoming the organoleptic effects of plant extracts alone 11–14…”

Development of a Chemically Defined Medium for Better Yield and Purification of Enterocin Y31 fromEnterococcus faeciumY31

“…Bacteriocin produced by lactic acid bacteria (LAB) is generally regarded as safe (GRAS) and Qualified Presumption of Safety (QPS) status [3,4], and it is a desirable trait as a food additive for extending the shelf-life of the fermented food and controlling the safety of foods [5,6]. Based on their molecular structure, bacteriocins can be divided into four groups: class I bacteriocins contain posttranslational modifications (lantibiotics and molecular weight ≤ 5 kDa); class II bacteriocins are unmodified and include small, heat-stable nonlanthioninecontaining peptides [7].…”

Onion (Allium cepa L.) bioactives: Chemistry, pharmacotherapeutic functions, and industrial applications

“…Sulfur compounds also showed antimicrobial activity; however, their use is limited due to their pungent property, strong flavor, and volatile nature (Rose et al., 2005). A combination of aqueous onion extract and bacteriocin (divergicin M 35) was used to inhibit Listeria monocytogenes and this combination inhibited the bacterium completely due to the antagonist activity (Zouhir et al., 2008). Other onion metabolites, such as saponins and proteins, also exhibited antimicrobial activity (Griffiths et al., 2002).…”