Antifungal agent production from a new marine Bacillus pumilusSMH101

Abstract

Twenty two (22) marine bacterial strains were isolated and tested to inhibit some plant and human pathogenic fungi; Fusarium solani, Rhizoctonia solani, Aspergillus niger, Fusarium exosporium and Candida albicans. The most potent marine bacterium was identified as Bacillus pumilusSMH101 on using 16S rRNA. The peptone water medium (PW) showed maximum antifungal activity. The PlacketBurman experimental design was applied and the optimum culture conditions were inoculum size (8.0 × 10 6 cfu/ml), temperature (25°C), incubation period (24 h) and pH value of 7.0. The trickle flow column was tested for propagating the antifungal production using luffa pulp and synthetic sponge as solid packing materials. The adsorbed B. pumilusSMH101 showed lower average fungal suppression (~ 40%) compared to the free bacterial cells (58.6%). Thin layer chromatography (TLC) was applied using a solvent system of dichloromethane: methanol: water (65:32:3 v/v). A single ultraviolet (UV) spot was obtained with a retardation factor (R f ) of 0.75. It analyzed using UV, infrared (IR) and mass spectrometry (MS) spectra and showed a molecular weight of 875 Da. Also, it showed a relatively low bio-toxicity (LC 50 = 1072 ppm) and a broad antifungal spectrum with a bioactivity of 87, 80 and 70% against F. solani, R. solani and C. albicans, respectively, compared to some commercial antifungal drugs based on the active fluconazole compound which applied in a concentration of tenfold more than the used B. pumilusSMH101 antifungal agent concentration (0.05 mg/ml).