Essential Oil of Greek <i>Citrus sinensis</i> cv New Hall - <i>Citrus aurantium</i> Pericarp: Effect upon Cellular Lipid Composition and Growth of <i>Saccharomyces cerevisiae</i> and Antimicrobial Activity against Bacteria, Fungi, and Human Pathogenic Microorganisms

In this study, the essential oil (EO) from the peel of the Greek citrus hybrid Citrus sinensis cv New Hall - Citrus aurantium was studied in terms of its antimicrobial properties as well as its effect on Saccharomyces cerevisiae. According to the analysis of the EO, 48 compounds are contained in it, with the main compounds being limonene, β-pinene, myrcene, α-pinene, valencene, and α-terpineol. As regards its antimicrobial properties, the EO was evaluated against nine human pathogenic microorganisms, six bacteria, and three fungi. Taking the results into account, it was apparent that Gram-negative bacteria were the most susceptible to the addition of the EO, followed by the Gram-positive bacteria, and finally the examined yeasts. The minimum inhibitory concentrations were found to be lower compared to other studies. Finally, the effect of the EO on the biochemical behavior of the yeast Saccharomyces cerevisiae LMBF Y-16 was investigated. As the concentration of the EO increased, the more the exponential phase of the microbial growth decreased; furthermore, the biomass yield on the glucose consumed significantly decreased with the addition of the oil on the medium. The addition of the EO in small concentrations (e.g., 0.3 mL/L) did not present a remarkable negative effect on both the final biomass concentration and maximum ethanol quantity produced. In contrast, utilization of the extract in higher concentrations (e.g., 1.2 mL/L) noticeably inhibited microbial growth as the highest biomass concentration achieved, maximum ethanol production, and yield of ethanol produced per glucose consumed drastically declined. Concerning the composition of cellular lipids, the addition of the EO induced an increment in the concentration of cellular palmitic, stearic, and linoleic acids, with a concomitant decrease in the cellular palmitoleic acid and oleic acids