Growth inhibition and morphological alterations of Aspergillus niger by essential oils from Thymus eriocalyx and Thymus x-porlock

The antifungal effects of essential oils from Thymus eriocalyx and Thymus x-porlock were studied with special reference to the mechanism of inhibition of Aspergillus niger growth at ultrastructural level. Minimal inhibitory (MIC), minimal fungicidal (MFC) concentrations, and fungicidal kinetics of the oils were determined. Transmission electron microscopy (TEM) of A. niger exposed to MIC levels of the oils showed irreversible damage to cell wall, cell membrane and cellular organelles. The oils analyzed by GC and GC/MS led to identification of 18 and 19 components in T eriocalyx and T x-porlock oils respectively. The results are compared and discussed with the data in literature. It is concluded that the essential oils could be safely used as preservatives. (C) 2005 Elsevier Ltd. All rights reserved.