Synergistic antimicrobial activity of two binary combinations of marjoram,lavender, and wild thyme essential oils

The combination of essential oils (EOs) is a novel alternative to improve their preservative effects and to reduce their organoleptic impact in food. In this context, this work aims to investigate the antibacterial combined effect of two EOs combinations through the calculation of the fractional inhibitory concentration index. The combinations tested consists of Lavandula dentata/Origanum majorana EOs and Thymus serpyllum/Origanum majorana EOs. Their chemical compositions were identified by CG/MS analyses. The main compounds of O. majorana EO were (-) - terpinene-4-ol and trans-4-thujanol. Those of L. dentata EO were β-pinene and 1,8-cineole, and those of T. serpyllum EO were p-cymene and γ-terpinene. Regarding the outcomes, results highlighted partial synergistic and additive interactions. Two combinations of marjoram and thyme EOs had antibacterial activities against S. aureus. The first one corresponded to the quarter of the minimum inhibitory concentration of marjoram and half that of thyme. The second one was the mix of half and quarter of the minimum inhibitory concentration of respectively marjoram and thyme EOs. This last combination also showed an antibacterial effect against E. coli. The quarter and the half of their minimum inhibitory concentration of marjoram and lavender combination, respectively, gave a partial synergy against both strains. Henceforth, these findings could be largely exploited in food preservation through the use of minimal doses of these plant products without affecting the antibacterial and the organoleptic properties in foods.     

Impact of enzymatic treatment on wood surface free energy: contact angle analysis

The aim of this study was to investigate the effect of cellulase treatment on wood surface physicochemical characteristics. The cedar wood samples were treated by cellulase for 30 min at different concentrations: 0.2, 0.4, 0.6, 0.8, 1, and 1.2 mg/ml. Then the physicochemical properties (the wetting behavior and interfacial free energy) of the cedar samples surfaces were characterized by the sessile drop technique. The obtained results showed that the untreated cedar wood samples exhibited a hydrophobic character with a high water contact angle (θ_w = 71.9°) and a negative value of the interfacial free energy (?Giwi = ?59.3 mJ/m²). Thereafter, the wood hydrophobicity decreased continuously until it reached the hydrophilicity qualitatively (at the first concentration of cellulase (0.2 mg/ml)) and quantitatively (at 0.8 mg/ml of cellulase). The cedar wood surface treatment with cellulase also revealed a significant evolution of the acid-base parameters. Moreover, a linear relationship between the degree of hydrophobicity and the cellulase concentration has been found. This study clearly shows the impact that could have the produced enzyme by micro-organisms involved in wood biodegradation and especially their consequences on the physicochemical surface properties of the wooden materials.