Cell enumeration and visualisation by transmission electron microscopy of Lactobacillus rhamnosus treated with cinnamon (Cinnamomum zeylanicum B.) essential oil

Abstract

The use of essential oils (EOs) in functional foods containing probiotic microorganisms must consider the antimicrobial activity of these oils against beneficial bacteria such as Lactobacillus rhamnosus. This study aimed to evaluate the sensitivity of L. rhamnosus cultures treated with cinnamon EO through viable cell counts and visualisation by transmission electron microscopy. Cinnamon EO at a concentration of 0.04% had a bacteriostatic activity after 2 h of incubation. Although slight alterations were detected in the cell structure, this concentration was considered to be bactericidal, since it led to a significant reduction in cell numbers after 24 h. On the other hand, cinnamon EO at a 1.00% concentration decreased cell counts by 3 log units after 2 h incubation and no viable cell count was detected after 24 h. Transmission electron microscopy indicated that cells treated with 1.00% cinnamon EO were severely damaged and presented cell membrane disruption and cytoplasmic leakage.

Short communication: Inhibitory activities of the lantibiotic nisin combined with phenolic compounds against Staphylococcus aureus and Listeria monocytogenes in cow milk

“…The characteristic phenolic compounds in essential oils are normally responsible for antimicrobial activity by acting on cell sites, causing the loss of cellular constituents, collapse of the bacterial cytoplasmatic membrane, and subsequent cell death (Burt, 2004;Sacchetti et al, 2004;Sartoratto et al, 2004;Barbosa et al, 2009;Al-Reza et al, 2010). Among phenolic compounds, carvacrol from oregano (Origanum vulgare; Lukas et al, 2013), cinnamaldehyde from cinnamon (Cinnamomum zeylanicum; Feniman et al, 2012), eugenol from clove (Syzygium aromaticus; Moritz et al, 2012), and thymol from thyme (Thymus vulgaris; Nikoli et al, 2014) have been studied, among others.…”

<i>In vitro</i> Antibacterial and Chemical Properties of Essential Oils Including Native Plants from Brazil against Pathogenic and Resistant Bacteria

“…Cinnamomum zeylanicum Blume Lauraceae cinnamon has been used throughout history against several diseases including antifungal, anti-parasitic, antibacterial and larvicidal properties 15,16 and its main compound is cinnamaldehyde 17 .…”

Characterization of the Biological Activities of a New Polyphenol-Rich Extract from Cinnamon Bark on a Probiotic Consortium and Its Action after Enzymatic and Microbial Fermentation on Colorectal Cell Lines

“…Indeed, the use of concentrated natural extracts and the registered antimicrobial effect against Gram-positive bacteria could antagonize the beneficial properties of the probiotic strains. As regards, Feniman et al [ 49 ] noted that a cinnamon extract tested at 1% concentration had detrimental effects on Lactobacillus and Bifidobacterium strains, leading to the disruption of the cell wall and the cytoplasmic membrane, causing the leakage of the cells. Interestingly, at the same polyphenol-rich cinnamon extract concentration of 1% w / v , our probiotic strains did not suffer considerably, reaching the same growth values as the negative control.…”