## 3 Results and Discussion
### Agar Disc Diffusion Method  
This method is a classical microbiological technique to test pharmaceutical antimicrobial agents such as antibiotics and antifungals in many clinical laboratories [27]. In this method, the antimicrobial agent, which is placed on a disk in the surface of an inoculatedagar, diffuses into the agar and inhibits the growth of the test microorganism. The inhibition creates a clear zone around the impregnated discs, which represents \"no growth\" areas, and the diameter of inhibition growth zones is an indication of the susceptibility of the microorganism to the specific antimicrobial agent (the greater the inhibition zone, the greater the susceptibility). It was observed (Figure 1) that the natural extracts showed negligible inhibition zones (<10 mm) or no inhibition zones (6 mm), except for the rosmary extract, which showed an inhibition zone (>10 mm) higher than that of fluconazole in the case of beer yeast. Indeed, rosmary has been extensively studied, and there is significant evidence of its antimicrobial activity against both Gram-negative and Gram-positive bacteria [28]. These properties make rosmary of particular interest as a natural food preservative [29]. The EU approved rosmary extract as a food preservative after extensive toxicity studies and determining that the observed adverse effect level (NOAEL) range was wide enough to not pose any safety concerns [30]. However, when an extract exerts low fungal growth inhibition, there may be no results in the disc diffusion method, and it would be worth-while assessing the extract's antimicrobial activity using alternative methods. Moreover, it should be noted that the carrier oils of the natural extracts, caprylic triglyceride and sunflower oil, were also tested for antifungal activity with the agar disc diffusion method and showed negligible inhibition activity (<10 mm) (Figure 1), although there are studies indicating antifungal activity of caprylic acid [31]. Pharmaceutical antifungals are categorized as fungicidal if they kill the fungus (such as amphotericin B) or fungistatic if they inhibit the growth of fungi [32]. Many known antifungals that are used for medical treatments such as azoles (e.g., fluconazole, clotrimazole, itraconazole, ketoconazole) can have either fungistatic or fungicidal activity depending on the dose and the species of microorganism [33; 34]. In this study, six pharmaceutical antifungal compounds were tested against the three _S. cerevisiae_ strains (Figure 1). It was  
Figure 1: Antifungal activity of the natural extracts (hypericum (_H. perforatum_), 10% \(w/w\), liquid maskic extract (_Pistacia lentiiscus var. Chia_, 20% \(w/w\)), and rosmary (_Rosmarinus officinalis_, 6% \(w/w\))) and various pharmaceutical compounds expressed in mm of inhibition zones in the disc agar diffusion method. Zero inhibition is considered when the diameter is 6 mm (the diameter of the disk, indicated by a red line). The average values and SD were compared with ANOVA followed by Duncan post hoc test. observed that the three strains of the same species \(S\). _cerevisiae_ demonstrated different susceptibilities to the various pharmaceuticals. All three strains exhibited susceptibility to amphotericin B, nystatin, ketoconazole, and clotrimazole, which clearly exerted fungicidal activity (diameter of inhibition zone > 20 mm). However, the beer and baker \(S\). _cerevisiae_ strains showed resistance to intraconazole (no inhibition zone), and the beer strain had low susceptibility to fluconazole (diameter of inhibition zone < 14 mm), which are known pharmaceutical agents used to treat fungal diseases. It is known that industrial yeasts have adapted to tolerate various environmental stresses such as high osmotic pressure, oxidative stress, temperature shifts, as well as chemical compounds; for example, wine yeasts have adapted to sulfite compounds and copper-based pesticides used in wineries [35; 36].