ABSTRACT
Objective: Marine fungi play an important role in human and animal health, leading compounds to new drug discoveries and prospects for their bioactivity potential. Materials and Methods: Paecilomyces WE3-F was isolated from marine sediment (Red Sea, Shalateen, Egypt). Fungal isolate was screened for their antagonistic activity against four Gram-positive (Bacillus cereus, Lesteria monocytogenes, Micrococcus luteus and Staphylococcu aureus) and four Gram-negative (Aeromonas hydrophila, Flavobacteruim sp, Pseudomonas aeruginosa and Vibrio cholera,) pathogenic bacteria. Paecilomyces WE3-F was identified using 18S rRNA technology. Seven factors were chosen to be screened for bioactivity using the Placket Burman experimental design: sucrose, yeast extract, Na NO3, temperature, initial pH, inoculum size, and incubation period. Results: Among conditional factors, acidic pH and 1.5 ml inoculum size favored the bioactive metabolites. Furthermore, a number of solvents have been experimented for the extraction of the bioactive metabolite(s). Dichloromethane (DCM) crude extract from the fermentation broth of a marine Paecilomyces WE3-F showed the highest activity with averages of 26 and 24 mm against G-ve and G+ve, respectively. Under optimal culture conditions, the maximum extractable compound concentration in a 10-L culture medium reached 83.4 mg/L. Based on data obtained by thin layer chromatogram (TLC), gas chromatography - mass spectrum (GC-MS) and Fourier Transform Infrared (FTIR) the major compound, betulin was structurally identified. Conclusions: The isolated marine Paecilomyces WE3-F, therefore, showed the ability to produce a betulin yield after optimal operating conditions for antibacterial potential.