Antimicrobial Potential of Fungal Endophytes from Moringa oleifera

The present study was aimed to isolate the endophytic fungi having antimicrobial potential from Moringa oleifera. Out of the active isolates, the endophytic fungal isolate DSE 17 obtained from the bark of the plant was selected for further studies and identified as Aspergillus fumigatus. The classical method for optimization strategy revealed inoculum size of four discs in Czapek dox's medium at a temperature of 25 °C and pH 7 with the incubation period of 6 days to be the best. Sucrose as carbon source (1%) and sodium nitrate as nitrogen source (0.2%) were found to be the best for antimicrobial activity. Response surface methodology was effective in optimizing the selected medium components in Plackett-Burman design, i.e. magnesium sulphate, dipotassium phosphate and sodium nitrate, which resulted in increase in antimicrobial activity by 1.7-fold. Chloroform was found to be the best extractant amongst different solvents. The minimum inhibitory concentration (MIC) values of the chloroformic extract ranged from 0.05 to 0.5 mg/ml, and the viable cell count studies revealed it to be bactericidal in its nature. The post-antibiotic effect (PAE) of the chloroformic extracts ranged from 2 to 20 h. Ames mutagenicity testing and MTT assay revealed the crude extract neither cytotoxic nor mutagenic, thus showing it to be biosafe. Thus, the study suggests that endophytes from this miracle plant could be potential source for the production of broad-spectrum antimicrobial compound/s.