Response Surface Methodology Based Optimization of a New Isolate Bacillus pumilus ZR LS S2 with Fibrinolytic Activity

Aim: To achieve bioremediation of hydrocarbon impacted mangrove soil using organic (sterile and non-sterile poultry wastes) and inorganic nutrient (NPK).

Study Design: Three treatments and the control designs were setup in three replicates and kept in the laboratory at room temperature (28±2°C) throughout the investigation period (6 weeks). Three of the set-ups designated Treatments (SPW, NSPW and NPK) were treated with sterile poultry wastes, non-sterile poultry wastes, nitrogen – phosphorus- potassium, respectively, while the fourth set – up with no treatment were designated control (CTRL). Set ups SPW, NSPW and NPK were designed to determine the effects of sterile poultry wastes, non-sterile poultry wastes and NPK in bioremediation of hydrocarbon polluted soil, respectively. However, the control (CTRL) was designed to determine the contribution made by indigenous (autochthonous) microorganisms and natural attenuation to the soil.

Place and Duration of Study: Department of Microbiology, Faculty of Biological Sciences, University of Port Harcourt, Rivers State, Nigeria, between August, 2012 and June, 2013.

Methodology: A laboratory-scale study was carried out using organic (sterile and non-sterile poultry wastes) and inorganic nutrient (NPK) to achieve bioremediation of hydrocarbon impacted mangrove soil.

Results: In a 42 day study, the sterile poultry wastes (SPW) treated option had an increase in total logarithmic heterotrophic bacterial count from 5.19±0.01 to 7.64±0.08 while non-sterile poultry wastes (NSPW) increased from 5.22±0.11 to 7.65±0.06. The logarithmic heterotrophic bacterial population of the NPK set-up increased from 5.23±0.11 to 7.90±0.10. The untreated set up had its total logarithmic heterotrophic bacterial count increased from 5.14±0.07 to 6.63±0.08. The total logarithmic hydrocarbon utilizing bacteria in SPW, NSPW and NPK treated options increased from 3.70±0.10 to 7.11±0.10, 3.82±0.10 to 7.20±0.10 and 3.93±0.08 to 7.73±0.07, respectively, at which time the corresponding value obtained for untreated increased from 3.63±0.06 to 5.56±0.06. Statistical analyses showed significant difference at p<0.05 level for the four conditions. Several genera of bacteria were isolated as hydrocarbon utilizing bacteria. They include Bacillus sp., Citrobacter sp., Corynebacterium, Escherichia sp., Flavobacterium, Micrococcus, Pseudomonas sp., Salmonella sp. and Vibrio sp. The conductivity values nitrate and phosphate concentrations in SPW, NSPW, and NPK options decreased progressively with slight decrease in the untreated. At day 42, the changes in total petroleum hydrocarbon (TPH) decreased to 498.14±0.01 ppm, 389.42±0.01 ppm, 285.38±0.01 ppm and 1087.00±0.01 ppm in SPW, NSPW, NPK and untreated, respectively.

Conclusion: The use of organic sources such as poultry wastes (sterile and non-sterile) and inorganic nutrient (NPK) has shown good promises in the bioremediation of hydrocarbon impacted mangrove soil.