GC-MS Analysis, Antifungal, and Antioxidant Activity of Rice Straw-Based Extract Produced by Aspergillus tubingensis AUMC 15759 in Solid State Fermentation

Black aspergilli are excellent candidates for a variety of secondary metabolites.In this investigation, Aspergillus tubingensis AUMC 15759 produced certain bioactive compounds in solid-state fermentation (SSF) utilizing some agricultural wastes, namely bagasse, barley bran, bean hay, date palm leaves, flax seeds, orange peels, rice straw, soybean, and wheat bran.Rice straw extract yielded the highest inhibition zones of 14.1±0.2,13.6±0.85,12.0±0.9,and 15.0±0.9mm, against Candida albicans, Candida glabrata, Candida krusei, and Saccharomyces cerevisiae.The rice straw extract demonstrated impressive antioxidant activity (%DPPH) that was nearly similar to that of ascorbic acid exhibiting IC50 of 1.2±0.2mg/ml.The liquid/liquid fractionation approach of the rice straw crude extract's liquid yielded five fractions, with the dichloromethane fraction being the most effective.GC-MS analysis disclosed the identification of nine substances linked to phenolic chemicals (3,4,5-trimethoxy phenol, 4-((1E)-3-Hydroxy-1-propenyl)-2-methoxyphenol, Phi.-Aspidinol, m-Aminophenylacetylene, and 1-Phenyl-2-propene), fatty acids (Palamitic acid and cis,cis-Linoleic acid), quinone derivative (2,6-Dimethyl-3-(methoxymethyl)-p-benzoquinone), and alkaloid (N-Didehydrohexacarboxyl-2,4,5-trimethylpiperazine).The dichloromethane fraction displayed potent antifungal activity.The MIC was 6.25 mg/ml, with inhibition zones of 14.0±0.4,15.5±0.7,14.0±0.4,and 14.2±0.2mm against the investigated fungi, respectively.It also had the lowest IC50 (1.4±0.2) when compared to the remaining fractions of n-butanol (1.8±0.4),ethyl acetate (1.5±0.6), n-hexane (11.5±0.2), and water (13.5±1.1), or ascorbic acid (10.64±0.84)mg/ml.Finally, this fungus displayed antifungal and antioxidant activities when grown on agricultural wastes.It can be concluded that the tested strain of A. tubingensis displayed antifungal and antioxidant activities when grown on agricultural wastes, particularly rice straw.