Phytochemical screening and antioxidative property evaluation of lipid-producing fungi.

The increased demands for natural bioactive compounds have induced the search for unusual sources. Microorganisms, especially fungi are a potent source of secondary metabolites, which could act mainly as antioxidant compounds to prevent oxidative stress. In the present study three soil-isolated fungi Aspergillus niger, Aspergillus heteromorphus and Aspergillus fumigatus, were screened for their oleaginous property as well as their potential for the production of bioactive compounds. Fungal biomasses were freeze dried and extracted with methanol using a cold percolation process for the production of intracellular metabolites and the fungal culture media after fermentation were examined for extracellular metabolites. Intracellular and extracellular extracts of the isolated fungi along with the single-cell oils extracted from those fungi were screened for phytochemicals, which showed the presence of alkaloids, flavonoides, glycosides, phenols, saponins and terpenoids. All strains showed potent antioxidant activity, determined using 1,1-diphenyl-2-picrylhydrazyl (DPPH), 2,2-azino-bis-3-ethylbenzthiazoline-6-sulfonic acid (ABTS) and ferric reducing antioxidant power (FRAP) activity. Extracellular extract and single-cell oil of A. heteromorphus showed the highest antioxidant activity with maximum ABTS radical scavenging activity and reducing potential. Highest content of phenolic and flavonoid compounds within the isolated fungi was found to be 37.58 mg gallic acid equivalent (GAE)/g and 62.07 mg catechine equivalent (CE)/g, respectively. Chromatographic analysis of the intracellular and extracellular extracts of the fungi showed the presence of gallic acid, di-hydroxy benzoic acid, ferulic acid, quercetin, epigerin, kampferol, trans cinnamic acid, chlorogenic acid and rutin, which made them biologically important and beneficial for human health.

Effect of Fungal Fermentation on Enhancement of Nutritional Value and Antioxidant Activity of Defatted Oilseed Meals.

Agro-industrial residues contain high nutritive value. Nowadays, various advanced researches have been done for the production of various value-added products, using these wastes as substrates in the fermentation media. Flaxseed, mustard, and rice bran meal, residues of oil industry, were used as substrates for fermentation. Submerged fermentation with soil-isolated fungal species of the genus Aspergillus sp. was done for oil production by using these substrates in the fermentation media. Effect of fermentation by the oleaginous species of Aspergillus on the nutritive value and functional properties of flaxseed, mustard, and rice bran meal has been discussed for the first time in the present study. After fermentation, the seed meals showed substantial increase in the protein and ash content. The fungal strains utilized the carbohydrate present in the seed meals for the production of highly nutritional metabolites, which decrease the sugar contents of the meals. The fungi also showed extracellular amylase and cellulase activities which helped to hydrolyze the carbohydrates present in these meals, to utilize them for their metabolism. The enhancement was also observed in terms of antioxidant activity of the meals. Increase in the total phenolic and flavonoid contents was observed after fermentation along with radical scavenging activity of 1,1-diphenyl-2-picrylhydrazyl and 2,2-azino-bis-3-ethylbenzthiazoline-6-sulfonic acid reagents and ferric reduction potential. These effects of fermentation modify these cheap waste materials into nutrient dense substrates, which could be further used in the formulation of value-added products.