Abstract

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Microbial bioactive compounds are biologically active microbial compounds that are synthesized from microorganisms which exhibit antimicrobial, antitumor, antiviral activities and so on. This study aimed at determining the antibacterial activity, quantification and characterisation of bioactive compounds in the methanolic extract of endophytic fungi isolated from Nipa palm (Nypa fructicans Wurmb.) leaves. Healthy leaves of Nipa palm were collected randomly from Gbalajam Mangrove Swamp in Port Harcourt, Rivers state, Nigeria. The leaves were washed, cut, surface sterilized and plated on acidified Potato dextrose agar for 5 days at 30oC. Fungal colonies were identified based on their morphological and microscopic characteristics. Bioactive compounds production was carried out by submerged fermentation of fungi at 30oC for 21days and extracted with methanol. Extracts were screened against some pathogenic bacteria using agar well diffusion assay at different concentrations. Molecular identification of isolate with maximum zone of inhibition was done using PCR (Polymerase Chain Reaction) and 18S rRNA sequencing. The bioactive compounds in its extract were characterised and quantified using GC-MS (Gas chromatography – Mass spectrometry) analysis. Seven endophytic fungi were isolated namely; Aspergillus sp., Penicillium sp., Fusarium sp., Pestalotiopsis sp., Phomopsis sp., Nigrospora sp. andRhizopus sp. Methanolic extract of Aspergillus sp. that was identified as Aspergillus fumigatus KU350620.1 exhibited maximum zones of inhibition. Eight bioactive compounds were characterised and quantified from the extract. Hexadecanoic acid, methyl ester (C17H34O) at 30.823% peak area was identified as the most active compound in the extract. The results of this study showed that Nipa palm leaves – endophytic fungal extract have antibacterial potential against pathogenic bacteria and the bioactive compounds from the extract can be used for drug development, industrial, agricultural and other biotechnological purposes

Keywords: Bioactive compounds, Endophytic fungi, Gas Chromatography, Molecular identification