[Chemical composition and antibacterial effects of rosmarinus officinalis L essential oil with lysozyme on listeria monocytogenes]

Rosmarinus officinalis L. as a member of the Lamiaceae family and lysozyme as a natural antibacterial agent is important in food microbiology, because of its characteristics. The aim of the present study was to determine the chemical composition and anti-listerial activity of Rosmarinus officinalis essential oil [REO] alone and in combination with lysozyme for enhancement of anti-listerial activity of both substances. Rosmarinus officinalis L. was purchased from a local grocery store at Shahrekord and was identified by the Institute of Medicinal Plants, ACECR. The air-dried aerial parts were subjected to hydrodistillation using a Clevenger apparatus to obtain essential oil and yielded oil was analyzed by GC/MS. Antibacterial activity [on basis of Minimum Inhibitory Concentration [MIC] of REO was studied separately and in combination with unheated lysozyme [L] and heat-treated lysozyme [HTL] on Listeria monocytogenes at different pH [5, 6 and 7] by a micro-broth dilution assay. The collected data were analyzed by SPSS software. In the current study, 98.05% of constituents of the essential oil were identified. The major components were alpha-pinene [14.06%], 1, 8-cineole [13.62%], verbenone [11.2%], camphor [10.51%], borneol [7.3%], 3-octanone [7.02%], camphene [5.46%] and linalool [5.07%]. The inhibitory action of REO was stronger at lower pH especially 5 [MIC=225 micro g/mL]. Inhibition by L at pH 5 was 640 micro g/mL but no inhibition was seen at pH 7. HTL resulted in more effective inhibition than L, especially at pH 5 and heat-treatment 80°C [MIC: 160 micro g/mL]. Combination of L + REO and particularly HTL + REO was led to enhancement of bacterial inhibition. It was concluded that REQ by the identified chemical composition was effective alone or in combination with L or HTL on Listeria monocytogenes as a food-borne pathogen