Spindle pole body duplication defective yeast cells are more prone to membrane damage

Citrus essential oil: would it be feasible as antimicrobial in the bioethanol industry?

Essential oils (EOs) extracted from Citrus peels contain 85%-99% volatile components (a mixture of monoterpenes, sesquiterpenes, and their oxygenated derivatives) and 1%-15% non-volatile compounds. Citrus EOs have been long known for their antimicrobial properties, owing to which these EOs have a diverse range of applications. However, no studies have reported the applicability of Citrus EOs for the control of bacterial and yeast contaminants in the bioethanol industry. In this regard, the present review aimed to explore the feasibility of Citrus EOs in this industry. The Web of Science database was searched for reports that described the association of Citrus EOs with the most common microorganisms in the bioethanol industry to evaluate the efficacy of these EOs as antimicrobial agents in this context. The objective of the review was to suggest a novel antimicrobial that could replace sulfuric acid and antibiotics as the commonly used antimicrobial agents in the bioethanol industry. Citrus EOs exhibit antibacterial activity against Lactobacillus, which is the main bacterial genus that contaminates this fermentation process. The present report also confirms the selective action of these EOs on the contaminating yeasts and not/less on ethanol-producing yeast Saccharomyces cerevisiae, however further studies should be conducted to investigate the effects of Citrus EOs in yeast-bacterium co-culture.

Phenolic -OH group is crucial for the antifungal activity of terpenoids via disruption of cell membrane integrity

Terpenoids, one of the major components of essential oils, are known to exert potent antifungal activity against yeast Saccharomyces cerevisiae. They have been the subject of a considerable number of investigations that uncovered extensive pharmacological properties, including antifungal and antibacterial effects. However, their mechanism of action remains elusive. In order to use terpenoids as the antimicrobial and antifungal agents in food preservation in a rational way, a good knowledge of their mode of action is required. We hypothesized that the cellular membrane is the main target site for the antifungal agents, and that structural properties of these agents are key to penetrate and act upon phospholipid bilayers. In this study, we thus aimed to study the effect of terpenoids on the cell membrane integrity, with the focus on both their structural properties, such as the presence of aromatic ring or hydroxyl group; and their hydrophobicity, as a consequence of these structural features. We first uncovered the antifungal properties of phenolic terpenoids thymol, carvacrol and eugenol, cyclic terpenes limonene, carveol, and α-pinene, in addition to the closely related compounds of different chemical structures. We then examined the cell membrane deterioration upon the addition of these reagents. Our results demonstrate that the presence of a phenolic -OH moiety is crucial, and hydrophobicity gained by the aromatic ring structure contributes to the ability of penetration and damaging yeast plasma membrane to achieve high antifungal activity.