Investigation on naphthalene biodegradation ability in a Bacillus sp. consortium isolated from soil samples

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous contaminants in the environment with potential mutagenicity and carcinogenicity. PAH bioremediation is considered as an effective and environmentally benign cleanup technology. In this study we isolated Bacillus sp. in soil samples with potential of naphthalene degradation and compared Bacillus spp. consortium and pure cultures biodegradation rate of naphthalene. Ten soil samples were collected from Tehran and around Tehran and Bacillus strains were isolated and identified by biochemical and molecular methods. After that, the amount of biosurfactant production was measured and emulsification test was conducted. Eventually, GC analysis was conducted on the consortium for naphthalene biodegradation investigation. Optimized growth conditions were also determined involved in degradation (nah genes). At the end, catabolic genes were identified. The isolates contained Bacillus cereus, Paenibacillus lactis, Bacillus fusiformis and Bacillus subtilis. All of the isolates had surface tension amount less than 40(mN/m) and growth in blood agar medium. It shows that all of them can produce biosurfactant, effectively. The surface tension amount for consortium was lower than pure cultures. In addition, the consortium showed the ability to tolerate 1000 ppm naphthalene concentration in medium and the maximum growth amount was in pH=6, 200 ppm naphthalene concentration, 150 rpm of shaker speed and yeast extract as an additional nitrogen source. The obtained results revealed that consortium of four isolates had more ability in naphthalene degradation as shown in other studies.