Antioxidant and antimicrobial activity of extracellular polymeric substances isolated from endophytic fungus (Debaromyces hansenii)

Abstract

Fungal endophytes are microorganisms dwelling in coalition with their host plant without causing any harm. Infact endophytes protect their host plant from diseases and make the plant tolerant to undesired environmental conditions. Till date many vascular plants have been reported as the reservoir of endophytes. Endophytes produce many bioactive compounds having wide applications in pharmaceutical, agricultural and industrial areas. In the present study, endophytic fungus (IN2) isolated from Camellia sinensis leaves, procured from Palampur, is identified and characterized for the production of extracellular polymeric substances exhibiting antioxidant activity. The PDB broth inoculated with endophytic fungus for 14 days was concentrated using lyophilization and purified by membrane dialysis. The extract so obtained was used for the estimation of exopolysaccharide (EPS). The dry weight of mycelium is 42 mg. The 258 μg/ml glucose concentration was obtained from 300 μg/ml extract. The protein concentration was estimated to be 20 μg/ml. The free radical scavenging activity of the EPS extract was calculated by DPPH antioxidant assay. The maximum DPPH scavenged was 53.2% at 500 μg/ml concentration. This clearly depicts the antioxidant activity of extracellular polysaccharides produced by IN2 endophytic fungus. Also the antimicrobial activity of the extract was evaluated using 96 well plate antimicrobial assay and agar well diffusion method. The extract showed little activity (8%) against Bacillus megaterium at 500 μg/ml concentration but no antimicrobial activity was observed against Pseudomonas aeruginosa and Staphylococcus aureus even at 2000 μg/ml. This shows that the IN2 endophytic fungus produced very little antimicrobial components. Further the IN2 endophytic fungus was identified by both morphological analysis and by molecular biology techniques. The morphological studies identified IN2 as Debaryomyces. The genomic DNA was isolated and amplified by ITS1 and ITS4 primers. The amplified product was sequenced and its homologous sequences were retrieved by BLASTn analysis. The phylogenetic analysis revealed that the isolated endophytic fungus clustered with Debaryomyces hansenii. Present study results suggest that Debaryomyces hansenii produce high level of extracellular polysaccharides having antioxidant activity.