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 as
Bacillus subtilis
and
Pseudomonas
spp. exhibited flocculation activity exceeding 90% after 3 days of cultivation. They were identified by 16 S rDNA
sequence analysis as
Bacillus subtilis and
Pseudomonas sp. Spectroscopic analysis of the polymers by nuclear magnetic
resonance and fourier-transform infrared 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
Bacillus subtilis and
Pseudomonas) 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 CaCl
2. 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 reached
its maximum in the stationary phase (at 72 h). Their efficient flocculation capabilities suggest potential applications in
industries.
