Enzymatic Potential and Antifungal Susceptibility Profile of Aspergillus terreus Against Essential Oils

Aspergillus terreus is a pathogen as well as an industrial organism. Current study deals with in vitro evaluation of A. terreus as a potential candidate for starch-based industries and susceptibility of toxigenic isolates to plant essential oils. Conventionally identified A. terreus soil isolates (n=25) were screened for mycotoxin production by TLC. Non- toxigenic isolates were selected for starch hydrolysis using starch agar. Toxigenic A. terreus were selected for antifungal activity of plant-derived essential oils (Nigella sativa, Elettaria cardamomum, Eucalyptus globulus, Cinnamomum verum Cuminum cyminum, and Syzygium aromaticum) by agar well diffusion and micro-broth dilution method. The lowest minimum inhibitory concentration (MIC ≥ 0.65±0.22µL/mL) was observed for Cuminum cyminum. So, it was used for inhibitory effect on growth and toxin production in broken grains. Cuminum cyminum EO inhibited the growth of A. terreus (0.00±0.00 cfu/g) in inoculated group and OTA production was also close to uninoculated group. Starch hydrolysis to colony diameter ratio helped for selection of isolates for further experiments. In starch hydrolysis, two isolates AST-01 and AST-02 produced highest ratios, which were 2.25±.08 and 1.76±.04 respectively. Influence of maize flour, wheat bran and rice husk with varying concentration, incubation temperature and pH were evaluated on starch hydrolysis potential. The hydrolytic potential quantified by dinitorosalisylic acid (DNS) method. A. terreus AST-02 had the highest hydrolytic potential (102.96±2.61IU) under incubation of 3% wheat bran at 37 °C and pH 6.0. It is concluded that A. terreus is a potential candidate for starch-based industries and further crop contamination by toxigenic species could be curtailed using essential oil as a feed preservative.