Compatibility and formulation of diesel degrading consortia using bacteria isolated from contaminated soil

Abstract

Soil contamination with diesel spillage is an increasing environmental challenge that damages living ecosystems. Efficiency of single bacterium in degrading diesel oil pollutants is faced with slow performance limitation. Therefore, the use of consortia is shown to be better, due to synergism, multi-enzymatic activity and potential for diversified catabolic functionalities. This study is aimed at formulating effective bacterial consortia that can degrade diesel in polluted environments. Four diesel degrading bacteria as Bacillus subtilis, Staphylococcus aureus, Micrococcus roseus and Rhodococcus specie were isolated and used for consortia formulation. Purity testing was performed on the isolates prior to consortia formulation, before their compatibility was tested by cross-spreading them on nutrient agar. Consortia formulation was made using Bacteria resting cells in Phosphate Buffer Saline based on compatibility testing and mathematical permutations. For on their ability to survive diesel on Bushnell-Haas Agar (BHA), consortia 2, 9 and 11 showed the best results among which consortium 11 was chosen as the best, considering growths on the medium within a 72 hrs period. The growth of the organisms before consortia formulation and after was also evaluated, which suggest that the consortium perform better than individual strains. Analysis of Variance showed significant statistical differences (p<0.05) between constituents of consortia, and diesel degradation on 2% (v/v) BHA. The degradation performances of the various consortia on BHA were furthermore separated by Duncan’s Multiple Range Test. The colony counts obtained indicate that degradation was performed better by the consortia than individual strains. The findings of the study contribute towards illuminating inter-microbial relationships and microbial ecology especially within groups of diesel degrading bacteria. Further studies are imperative, to maximally harness the potentials of these bacteria for applications in large scale diesel biodegradation.    

Key Words: Consortia, Diesel, Bacterial Biodegradation, Haemocytometry.