Biodegradation of Total Petroleum Hydrocarbons (TPHs) by Bacillus Cereus, Myroides species and Enterobacter species under different environmental conditions”

Abstract

The marine environment may be contaminated due to various activities of the petroleum industry with crude petroleum oil. In order to protect living organisms in this environment and for the protection of human health, this polluted marine environment must be bioremediated and detoxified. Although physiochemical methods are still used in various developing countries, biological treatments are the alternative because they are cheap, causing no harm to the environment. Different types of bacteria are able to clean up the polluted sites. In the present work, three bacterial species were used separately and in combination (a consortium) to biodegrade crude oil polluting marine water. Identification of the 3 bacteria was done using gene sequencing of 16s rRNA and they were recognized as Bacillus cereus MSA 6M, Myroides odoratimimus MSA 185 and Enterobacter cloacae MSA 47. Screening of the three bacterial strains was done for the production of biosurfactants and bio-emulsifiers using different media, different NaCl concentrations and different pH values. The results obtained showed that the 3 bacterial strains were able to produce active biosurfactants (155.5 – 176.6 cm2 ODA) when WFO was used as substrate, while when glycerol was used, the three bacteria behaved as weak biosurfactant producers (1.0 – 17.0 cm2 ODA). On the other hand, the two culture media were promising for the production of bio-emulsifiers. The results also show that 2% and 3% NaCl were promising for the production of biosurfactants and bio-emulsifiers. As for the effect of pH values, it can be seen that different results were obtained. Optimum pH values for B. cereus are 6-7 pH, for M. odoratimimus are 8-9 pH and for E. cloacae are 7-9 pH. These results indicate that the 3 bacteria work well in different ranges of pH values. On the other hand, the same trend of results were also observed