Investigation of Antimicrobial Activity and Identification of Bioactive Volatile Metabolites of Jute Endophytic Fungus Aspergillus flavus

Abstract

Jute, a well-known tropical plant with high fibre quality and medicinal importance, is extensively used in south Asian region. The present study was intended to isolate, identify, and evaluate the biological properties of an endophytic fungus of jute and also to decipher the plethora of volatile organic compounds it produces. The target endophyte Aspergillus flavus was identified by morphological analysis and by sequencing the internal transcribed spacer (ITS) region. Both extracellular and intracellular fungal extract exhibited broad spectrum antibacterial activity against six opportunistic human pathogenic bacteria (Lactococcus lactis NCTC 497, Bacillus subtilis168, Staphylococcus aureus SG511, Staphylococcus carnosusTM300, Bacillus pseudomycoides DSM 12442 and Escherichia coli BL21 (DE3)). The ethyl acetate extract displayed greater antimicrobial activity against all the tested pathogens than the methanolic extract. Further, profiling of total volatile organic compounds of the fermented extract using Gas Chromatograph-Mass Spectrometry (GC-MS) confirmed the presence of a variety of bioactive components. The major compounds identified in GC-MS analysis included 4-nitrobenzoic acid, 3-chlorophenyl ester (27.23%) and (+)-salsolidine (21.82%) which are nitrobenzoate and alkaloid class of compounds respectively and are known to have antimicrobial potential. In conclusion, the endophytic A. flavus isolated from jute can be seen as a commercial and potential natural resource with varied therapeutic and biological activities. However, the features of these compounds and the mechanisms of action should be further studied to understand their specific activity.