Antioxidant Potential and Extracellular Auxin Production by White Rot Fungi

Selective lignin degrading white rot fungi viz. Phanerochaete chrysosporium, Phlebia brevispora, and Phlebia floridensis were selected to evaluate antioxidant potential and auxin (indole acetic acid) production in complex and synthetic medium. Antioxidant potential of these fungi was tested against different free radicals including 2, 2-diphenyl-1-picrylhydrazyl (DPPH), nitric oxide, ferrous ion, and ferric ion along with total phenolic content. All the fungal strains produce phenolics ranging from 5.2 to 16.7 mg/ml and demonstrated various free radical and metal ion scavenging activity. Growth medium significantly affected all the activities. Almost similar antioxidant activity (~ 72% DPPH scavenging activity) was demonstrated by all the fungi in yeast extract glucose medium; however, the activity was lower in Czapek dox's medium (from 60 to 45%). Indole acetic acid production was maximum in P. brevispora (31 μg/ml), which was closely followed by P. chrysosporium and P. floridensis. The extracts did not show any mutagenic or cytotoxic effect. Thus, these white rot fungi highlight their significance as a new source for the prompt production of extracellular antioxidants and auxin.