Analytical study and comparison of the production of alkaloids and the bioactivity of five Aspergillus isolates on two mediums of agricultural waste and malt

Abstract

The content of the growth medium contributes to directing the fungus towards producing metabolites with specific properties that can be used in industrial or pharmaceutical fields. The research aims to formulate fungal growth medium from agricultural wastes (AW) and cultivate the Aspergillus species on them, and estimate their impact on the production of alkaloid compounds and their comparison with commercial malt extract media, where the alkaloids extracted and estimated in three types of extracts: Aqueous, methanol, and ethyl acetate for five isolates grown on the two previous media and then tested on a group of pathogenic microorganisms to determine their minimum inhibitory concentration (MIC), the SPSS 22 was used to statistically process and analyze the data. The results showed that the solvent ethyl acetate was superior in extracting alkaloids, followed by methanol and water. In general, each isolate gave a concentration of alkaloids depending on the medium it preferred, as the isolate was more capable of producing alkaloids on the agricultural waste medium and malt extract medium, belonged to the type A. niger1, 30.73 ± 0.5 µg /mg, and the type A. carbonarius, 14.09 ± 0.2 µg /mg, respectively.

The total amount of alkaloids in the extracts matched the biological activity, as

the ethyl acetate extract gave the best results on all pathogenic microorganisms, followed by methanol and water. The best ethyl acetate extract was for the A. niger1 isolate, with an MIC value of 1.9 mg/ml, and for the methanol for the A. avenaceus isolate grown on malt extract medium with an MIC value of 3.1 mg/ml, water for A. avenaceus isolated on agricultural waste media had an MIC value of 5.3 mg/ml. The greatest effect was for ethyl acetate and methanol extracts on Escherichia coli bacteria, where the MIC value reached 1.4 – 3.1 mg/ml, respectively.

The greatest inhibitory effect of the water extract was on Staphylococcus aureus bacteria with an MIC value of 4.3 mg/ml, and the best antifungal extract against C. albicans was for the A. niger1 isolate with an MIC value of 2.9 mg/ml. We recommend an agricultural waste medium as a stimulating medium for the production of fungal alkaloids and the Aspergillus genus as a miniature biofactory that produces many promising compounds against pathogenic microorganisms.