Characterization of bioflocculants produced by bacteria isolated from crude petroleum oil

ABSTRACT

The aim of this study was to look for high efficient bioflocculant-producing microorganisms. Among 36 bacterial colonies isolated from a crude petroleum oil sample, three of them CPO8, CPO13 and CPO14 exhibited flocculation activity exceeding 90% after 3 days of cultivation. They were identified by 16S rDNA sequence analysis as Bacillus subtilis [CPO8, CPO13] and Pseudomonas sp. [CPO14]. Spectroscopic analysis of the polymers by nuclear magnetic resonance [1H NMR] and Fourier-transform infrared [FT-IR] revealed that the polymers were glycoproteins. These polymers were soluble in water and insoluble in any organic solvents tested. The effects of bioflocculant dosage, temperature, and pH on the flocculation activity were evaluated. The maximum bioflocculation activities were observed at an optimum bioflocculant dosage of 3.5 mg/l [strains CPO8 and CPO13] and 5.0 mg/l [strain CPO14], respectively. In addition, these biopolymers were able to flocculate kaolin suspension [5 g/l] over a wide range of pH [pH 3-9] and temperature [5-50 °C] tested in the presence of CaCl2. The highest flocculation activities of strains CPO8, CPO13 and CPO14 were 96.03%, 92.17% and 97.59%, respectively in the early stationary phase [at 24 h], while the cell production reach its maximum in the stationary phase [at 72 h]. Their efficient flocculation capabilities suggest potential applications in industries