Muller hilton agar

To identify the microbial strains responsible for biodeterioration, fifteen samples were collected before the spray treatment. Particularly, five cotton swabs (Boettger, Paul Boettger GmbH & Co. KG, Bodenmais, Germany) and five fungi-tapes (Scientific Device, Glenview, IL, USA) were collected on the back of the artwork (Figure 2b), while only five cotton swabs were collected on the front. All samples were picked up in correspondence with the area potentially characterised by biodeteriogens’ attack (Figure 2c) and were sent to the microbiology laboratory. Afterwards, samples were seeded on the following nutrient agar: Muller Hilton agar, Malt Extract agar, and PDA (all by Oxoid, Basingstoke, UK) and incubated for 7 days at 30 °C. At the end of the incubation time, the recognition of the fungal strains was carried out using matrix-assisted laser desorption ionisation time-of-flight mass spectrometry (MALDI-TOF MS) Bruker Daltonics (Bruker, Bremen, Germany).

Antibacterial activity of the volatile oils was tested by means of the agar well diffusion method as described by Collin [23 ]. The microbial cultures used in this study were inoculated in nutrient broth (Oxoid) and incubated for 24 h at 37 ± 0.1 °C. Sufficient amount of Muller Hilton Agar (Oxoid) were poured into sterile petri dishes and permitted to solidify under aseptic situation. Using a sterilized cork borer, five 6 mm diameter wells were evenly distributed in freshly prepared and solidified Mueller Hilton agar (Oxoid) in petri dishes. The bacterial culture was adjusted to 0.5 Mc Farland turbidity standard and the test microbes (0.1 mL) were inoculated with a germ-free swab on the exterior of the appropriate solid medium in each of the petri dishes. Varying concentrations of the volatile oil made from the stock ranging from 0.04 to 0.025mgmL⁻¹ were prepared and introduced into each of the wells and labelled appropriately. The inoculated petri dishes were incubated at 37 °C for 24 h. All the petri dishes were then examined for zones of growth inhibition surrounding the individual wells and the average diameter of these zones was measured in millimeters. All tests were performed under hygienic conditions.