Antifungal effect of thyme essential oils and thymol on fungal species aspergillus flavus and aspergillus oryzae

Vrsta Aspergillus flavus se, još uvijek, smatra najznačajnijom vrstom plijesni koja razgrađuje namirnice. Pored brzog rasta, proizvodnja mikotoksina ju čini jednom od najpoznatijih i najlakše prepoznatljivih vrsta. Aspergillus oryzae, vrsta koja joj je vrlo slična, se koristi u fermentacijama u Kini, Japanu i ostalim Daleko istočnim zemljama. U ovom radu, ispitan je antifungalni učinak eteričnog ulja majčine dušice i njegovog najzastupljenijeg sastojka – timola na A. flavus (3.2758) i A. oryzae u in vitro i in situ uvjetima. A. flavus 3.2758 se pokazao najosjetljivijom vrstom (MIK > 1000 ppm) dok je A. oryzae inhibirala koncentracija ulja > 2000 ppm. Učinak timola je bio značajno snaţniji, na obje ispitane vrste (250 ppm). U in situ eksperimentu, jabuke sorata Granny Smith I Zlatni Delišes su tretirane različitim koncentracijama eteričnog ulja (250, 500 I 750 ppm) ili timolom (100, 150 I 200 ppm) i čuvane pri 20 ili 25°C. Više koncentracije analiziranih tvari i niža temperatura su djelovale sinergistički i produžile lag fazu rasta kolonije plijesni. Rast plijesni na ploškama Granny Smith jabukama je, u većoj mjeri, inhibiran u usporedbi s rastom na ploškama Zlatni Delišes.Among many fungal species, Aspergillus flavus is still one of the most important food deteriorating species. Besides rapid growth on different substrates, production of mycotoxins makes it one of the best-known and easily recognized fungal species. Aspergillus oryzae, very similar species is used in food fermentation in China, Japan and other Far East countries. In this work, antifungal effect of thyme essential oil and its main component – thymol was tested on A. flavus (3.2758) and A. oryzae in in vitro and in situ conditions. A. flavus 3.2758 was the most sensitive strain to thyme oil (MIC > 1000 ppm) while A. oryzae was inhibited by > 2000 ppm. Thymol activity was considerably stronger since minimal inhibitory concentration, for tested species, was 250 ppm. In in situ experiments, apples of Granny Smith and Golden Delicious were treated with different concentrations of thyme essential oil (250, 500 and 750 ppm) or thymol (100, 150 and 200 ppm) and incubated at 20 or 25°C. Higher concentrations of tested compounds and lower temperature acted synergistically and increased lag phase of colony growth. Fungal growth on Granny Smith apple was retarded compared to growth on Golden Delicious apple slices