The objective of the present study was to investigate the effect of some semi-arid medicinal herb essential oils (EO) on Butyrivibrio fibrisol- vens SH13 growth characteristics. The liquid version of Hobson’s M2 medium (Hobson, 1969) in Hungate tubes was used to estimate sensi- tivity of Butyrivibrio fibrisolvens SH13 to semi-arid native cinnamon, thyme and coriander essential oils. Butyrivibrio fibrisolvens SH13 stock culture was grown anaerobically in M2 medium in 125-mL bot- tles for 16 h at 38.6°C before testing. Butyrivibrio fibrisolvens SH13 was obtained from the Rowett Research Institute (Aberdeen, UK) cul- ture collection. After the medium was autoclaved, each essential oil was applied to give a concentration ranging from 0.0 (as control) to 10, 20, 40, 80, 120, 180, 240, and 360 ppm (4replicates). Essential oils were previously dissolved in equal volume of ethanol. All cultures were grown anaerobically at 38.6°C using an inoculum from stationary phase of stock culture (5% of v/v) for 24 h. The concentration of a EO at which the Butyrivibrio fibrisolvens SH13 growth was half of that measured in the control (IC50) was recorded during 24 h of incubation. Butyrivibrio fibrisolvens SH13 growth was measured by hourly read- ing optical density of the medium at 650 nm (OD650). As presented in Table 1, when each EO applied to the culture medium inhibited the growth of Butyrivibrio fibrisolvens SH13 at the concentration of higher than 240 ppm. An increase in the concentration of coriander EO (UP to 240 ppm) led to increase Butyrivibrio fibrisolvens SH13 OD650 compared with those of the control (P < 0.05). Results of the present study demonstrated that the essential oils might alter growth pattern of Butyrivibrio fibrisolvens SH13.

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