Antimicrobial Effect of <i>Picea abies</i> Extracts on <i>E. coli</i> Growth

• Main Authors: Nabil Haman, Ksenia Morozova, Giustino Tonon, Matteo Scampicchio, Giovanna Ferrentino
• Format: Article
• Language: English
• Published: MDPI AG 2019-11-01
• Series: Molecules
• Subjects: <i>picea abies</i>; supercritical fluid extraction; isothermal calorimetry; antimicrobials
• Online Access: https://www.mdpi.com/1420-3049/24/22/4053

This study aims to investigate the effect of essential oils extracted from wood residues of <i>Picea abies</i> on the growth of <i>Escherichia coli</i>. The essential oils were extracted by supercritical carbon dioxide, leading to a yield of 3.4 &#177; 0.5% (<i>w</i>/<i>w</i>) in 120 min. The antimicrobial effect was tested at 37 &#176;C by isothermal calorimetry. The heat-flow (dq/dt vs. time) was integrated to give a fractional reaction curve (&#945; vs. time). Such curves were fitted by a modified Gompertz function to give the lag-time (&#955;) and the maximum growth rate (&#181;max) parameters. The results showed that &#955; was linearly correlated with <i>E. coli</i> concentration (&#955; = 1.4 h/log (CFU/mL), R² = 0.997), whereas &#181;max was invariant. Moreover, the overall heat was nearly constant to all the dilutions of <i>E. coli</i>. Instead, when the essential oil was added (with concentrations ranging from 1 to 5 mg/L) to a culture of <i>E. coli</i> (10⁴ CFU/mL), the lag-time increased from 14.1 to 33.7 h, and the overall heat decreased from 2120 to 2.37 J. The results obtained by the plate count technique were linear with the lag-time (&#955;), where (&#955; = &#8722;7.3 &#215; log (CFU/mL) + 38.3, R² = 0.9878). This suggested a lower capacity of <i>E. coli</i> to metabolize the substrate in the presence of the essential oils. The results obtained in this study promote the use of essential oils from wood residues and their use as antimicrobial products.