Evaluation of Plant Origin Essential Oils as Herbal Biocides for the Protection of Caves Belonging to Natural and Cultural Heritage Sites

Abstract

The present study concerns the serious issue of biodeterioration of the caves belonging to natural and cultural heritage sites due to the development of various microorganisms. Thus, a series of 18 essential oils (EOs) extracted from various Greek plants were evaluated in vitro (concentrations of 0.1, 0.2, 0.5, 1.0 and 5.0% v/v) against 35 bacterial and 31 fungi isolates (isolated from a Greek cave) and the antimicrobial activity was evident through the changes in optical density of microbial suspensions. In continuance, eight (8) representative bacterial and fungal isolates were further used to evaluate the minimum inhibitory concentration (MIC) and non-inhibitory concentration (NIC) values of the most effective EOs. According to the results, two EOs of Origanum vulgare were the most effective by inhibiting the growth of all the tested microorganisms at 0.1% (v/v), followed by that of Satureja thymbra which inhibited all bacterial isolates at 0.1% (v/v) and fungal isolates at 0.1, 0.2 and 0.5% (v/v) (depending on the isolate). The MIC ranged between 0.015–0.157 and 0.013–0.156 (v/v) for the bacterial and fungal isolates respectively, depending on the case. The current study demonstrated that conventional biocides may be replaced by herbal biocides with significant prospects for commercial exploitation.

Evaluation of the Cleaning Effect of Natural-Based Biocides: Application on Different Phototropic Biofilms Colonizing the Same Granite Wall

“…This result is in agreement with other studies [69] that already demonstrated the broad biocidal action spectrum of such compound towards several microorganisms, such as fungi, bacteria, cyanobacteria and algae, found on various cultural heritage materials [54,[72][73][74]. As an example, a study of Argyri et al (2021) [75] tested eighteen high-quality essential oils from Greece, including extracts from Salvia sp., Foeniculum sp., Satureja sp, Juniperus sp., Citrus sp., Laurus sp. and Origanum sp., against 35 bacterial and 31 fungi isolated from a Greek cave, and the better results were obtained for both the EOs from O. vulgare, which inhibited the growth of all the strains at very low concentrations (0.1% v/v).…”

Antibacterial activity of plant essential oils against indigenously characterized methicillin-resistant Staphylococcus aureus (MRSA)

“…Bacterial suspension of 100μL (0.5 MacFarland) was pipetted from 1 st to 11 th wells each then optical density of micro-titration plate was taken at 630nm at 0 time and 24 hours after the incubation at 37°C. After this, the same MIC procedure was repeated for E. globulus fractions in n-hexane, chloroform, n-hexane + chloroform and ethyl-acetate organic solvents (Argyri et al, 2021).…”

16S and 18S rDNA Amplicon Sequencing Analysis of Aesthetically Problematic Microbial Mats on the Walls of the Petralona Cave: The Use of Essential Oils as a Cleaning Method

“…Therefore, the potential antibacterial and antifungal properties of these oils are of great importance in many different applications [12]. It was recently established that certain EOs are effective antimicrobials against bacterial and fungal isolates from the Petralona Cave [13]. This cave is a karst formation found on the Chalkidiki peninsula in Greece, 300 m above sea level, one mile east of the settlement of Petralona, and 55 km from Thessaloniki [14,15].…”