EVALUATION OF THE SYNERGISTIC EFFECT OF ETHANOL AND LEMONGRASS OIL AGAINST Aspergillus niger

Abstract

The aim of this work was to evaluate the antifungal efficiency of ethanol and lemongrass oil at the different concentrations, alone and in combination both against Aspergillus niger by agar disk diffusion method, mycelial growth inhibition and broth dilution method to determine MIC and MFC. The ultraviolet (UV) absorption and electrical conductivity of the culture supernatant were used to determine membrane integrity. Scanning electron microscopy (SEM) performed to observe A. niger spore morphology. The results showed that the MIC and MFC values of lemongrass oil (in tween 20 0.3% v/v) was 5 μL/mL and 250 ppm which were 100 and 200 times respectively lower than ethanol. The combination of lemongrass oil in tween 20 with ethanol (20% v/v) show the best result with the inhibition zone and MGI (%) was observed at 2.5 μL/mL and 100% respectively. The UV absorption and electrical conductivity values increased quickly after 16h incubated in the antimicrobial agents whereas there were almost unchanged in the control at the point of time. The SEM results show that, the morphological changes of the A. niger spores due to significant wrinkles and distortion in the samples treated by lemongrass oil or lemongrass oil combining with ethanol while the A. niger spores in ethanol show slight wrinkles. These suggest that ethanol has a synergic effect which enhances the antifungal activity of lemongrass oil. This combination is necessary to ensure the antimicrobial effect as well as reduce the amount of used essential oil.