Comparison and optimization of antioxidant compounds produced by autochthonous and allochthonous Aspergillus strains

Antioxidants reduce the risk of cardiovascular diseases, and stroke and prevent the development of cancer by neutralizing free radicals. The present study aimed to produce and optimize the production of antioxidant compounds by Aspergillus strains.

Fungi samples were collected from different regions of Isfahan province or obtained from the Persian Type Culture Collection. Purified fungi samples were inoculated to the Czapek medium to produce antioxidant compounds. Screening and comparison of antioxidant properties of the selected strains were carried out using four assays including free DPPH (Diphenyl pycryle-Hydrazyl) radical reduction, iron radical recovery, and total phenol content and flavonoid content assays. Fungi antioxidant activity was optimized in terms of pH, temperature, and type of carbon and nitrogen sources by single factor and detailed factorial (Taguchi) designed experiments.

The highest antioxidant activity was observed in Aspergillus niger isolated from the soil of the Iron melting factory and the highest amount of flavonoid content was shown by Aspergillus fumigatus isolated from greenhouse soil. DPPH radical reduction rate by Aspergillus niger was 89.9% in the optimum condition (pH 6, the temperature of 25°C, sucrose as carbon source and potassium nitrate as nitrogen source). Optimization by Taguchi designed experiments resulted in a 10-15 percent increase in antioxidant compounds production.

Autochthonous isolated fungi had high potential to produce antioxidant compounds and can be proposed to related industries.