Comparative Evaluation of Crude oil Degradability Efficiency of Bacillus amyloliquefaciens and Comamonas testosteroni in Soil
Authors: Akani N. P. , Ogbonna D. N. , Douglas S. I. , Awari V. G. 
Published: April 2020

Comparative evaluation of crude oil degradability efficiency of Bacillus amyloliquefaciens and Comamonas testosteroni with nutrient amendment were investigated in Crude oil Contaminated Soil. The bacteria species used in this study were isolated from the soil collected from Rivers state university research farm using standard microbiological methods. Evaluation and monitoring of bioremediation were done for a period of 56 days while analyses were carried at a constant interval of seven (7) days. Seven (7) experimental set-ups were employed using black polythene bag, The bags were perforated to enhance aeration,  each containing 5 kg of agricultural soil and left to fallow for 6 days, on the seventh day each of the experimental set-ups (5kg of soil) except the control (CTRL) were contaminated with crude oil (COCS) giving initial Total Petroleum Hydrocarbon (TPH) value of 10328.03 mg/kg; after which it was allowed for 21 days to ensure even distribution and soil-oil bonding to mimic crude oil spill site before application of augmenting bacteria; Bacillus amyloliquefaciens (BC) and Comamonas testosteroni (CM) and the stimulant; Goat manure (GM). Soil profile before and after contamination were analyzed while parameters like Sulphate, pH, Nitrate and Total Petroleum Hydrocarbon (TPH), as well as microbial analyses such as Total Heterotrophic Bacteria (THB), Total Heterotrophic Fungi (THF), Hydrocarbon Utilizing Bacteria (HUB) and Hydrocarbon Utilizing Fungi (HUF) were monitored and evaluated throughout the experimental period. Bioremediation efficiency was estimated from percentage (%) reduction of Total Petroleum Hydrocarbon (TPH) from day 1 to the residual hydrocarbon at day 56 of bioaugmented/biostimulation set-ups with the control. The microbiological result of the soil before and after contamination revealed that Bacillus sp had the highest percentage for bacterial isolates while Mucor sp. had the highest percentage for fungal isolates in both uncontaminated and contaminated soil. Colonial count of uncontaminated soil ranged from 5 x104 (HUB) <7 x 104 (HUF) <1.6 x 105 (THF) to 2.58 x 108 (THB) while contaminated soil colonial count ranged from 8 x 104 (HUB) < 9 x 104 (HUF) <2.0 x105 (THF) to 2.10x108 (THB). Microbial evaluation of the bioremediation set-ups showed increased colonial values with increase in time but slightly decreased on the last day. Results of total petroleum hydrocarbon revealed the actual amount of hydrocarbon reduction after the experiment and its percentage hydrocarbon remediated from the initial concentration in the various treatment setups  in the following  decreasing order;(CTRL) 125.71 mg/kg; 1.21% < (COCS + BC) 1855.74 mg/kg; 17.96% < (COCS + CM) 2261.01 mg/kg; 21.89% < (COCS + CM+ BC) 3321.23 mg/kg; 32.15% < (COCS + GM + BC) 4983.81 mg/kg; 48.25 < (COCS + GM + CM) 7313.47 mg/kg; 70.81%. Conclusively, the results obtained indicate that Comamonas testosteroni with nutrient amendment had the more degradability efficiency compared to Bacillus amyloliquefaciens. It is therefore recommended that bioremediation crude oil polluted soil using bioaugmentation technique should be amended with organic nutrient to enhance efficiency.