Abstract
The aim of this study was to investigate the antibacterial activity of black pepper essential oil (BPEO) on Escherichia coli, further evaluate the potential mechanism of action. Results showed that the minimum inhibition concentration (MIC) of BPEO was 1.0 μL/mL. The diameter of inhibition zone values were with range from 17.12 to 26.13 mm. 2 × MIC treatments had lower membrane potential and shorter kill-time than 1 × MIC, while control had the highest values. E. coli treated with BPEO became deformed, pitted, shriveled, adhesive, and broken. 2 × MIC exhibited the greatest electric conductivity at 1, 3, 5, 7, 9, 11, and 13 h, leaked DNA materials at 4, 8, 12, 16, 20, 24, and 28 h, proteins at 4, 6, 8, 10, 12, 14, and 16 h, potassium ion at 0, 0.5, 1, 1.5, and 2 h, phosphate ion at 0.5, 1, 1.5, and 2 h and ATP (P < 0.05); 1 × MIC had higher values than control. BPEO led to the leakage, disorder and death by breaking cell membrane. This study suggested that the BPEO has potential as the natural antibacterial agent in meat industry.
Highlights
Herbs and spices have been applied due to the well-documented sensory properties, special pharmacological functions, and antimicrobial activity (Mata et al, 2007; Park, 2011), where the essential oil (EO) was extracted for meat preserving (Al-Reza et al, 2010; Tajkarimi et al, 2010)
The results in this study showed that the relative electric conductivity of E. coli increased rapidly with the increasing treatment time and concentration of black pepper essential oil (BPEO), which meant that the permeability of bacteria membrane would increase correspondingly, cause the leakage of electrolytes and lead to cell death
Our results showed that the exposure of E. coli to BPEO caused the rapid loss of 260-nm absorbing materials and proteins, indicating an irreversible damage to the cytoplasmic membranes, which was supported by the results of the permeability of cell membrane, Scanning Electron Microscope (SEM) and Transmission Electron Microscope (TEM)
Summary
Herbs and spices have been applied due to the well-documented sensory properties, special pharmacological functions, and antimicrobial activity (Mata et al, 2007; Park, 2011), where the essential oil (EO) was extracted for meat preserving (Al-Reza et al, 2010; Tajkarimi et al, 2010). The majority of the EOs has been classified as Generally Recognized As Safe (GRAS) by EU standards (Smith and Navilliat, 1997) They are liquid, volatile, and rarely colored, containing a complex mixture of compounds (Bakkali et al, 2008). A large number of biological activities of EOs have been reported, such as antimicrobial, antiviral, antioxidant, antimycotic, antiparasitic, antidiabetic, and anticancer (Reichling et al, 2009)
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