Indigenous microbial strains as bioresource for remediation of chronically polluted Niger Delta soils

Abstract

An increase in artisanal crude oil refining within the Niger Delta Creeks has led to colossal environmental problems occasioned by spillages and subsequent ecosystem damage. Bacteria have been shown to play key role in biogeochemical cycling and degradation of pollutants from petroleum sources. The present study investigated the degradation efficiency of a bacterial consortia recovered from heavily inundated site in Bie-Ama community, having total petroleum hydrocarbons (TPH) concentration of 22,000 mg/kg, a value higher than Department of Petroleum Resources (DPR)’s 1000 mg/kg intervention limit. Soil samples were collected at 15 cm depth with soil auger while microbial isolation was done using enrichment and vapor phase transfer methods in Bushnell Haas medium. Colorimetric method using 2, 6-dichlorophenol indophenol (DCPIP) redox indicator was employed to determine biodegradation potentials of isolates. Bacterial isolates identified using 16S rRNA gene by Sanger sequencing were further screened for biosurfactant production and aromatic hydrocarbon degradation abilities. A consortium for efficient biodegradation of crude oil was constituted from individual isolates that totally decolorized DCPIP. Total culturable heterotrophic and hydrocarbon utilizing bacterial counts were 2.07 × 106 and 1.71 × 106 CFU/g soil respectively. Bacterial strains from the genera Pseudomonas, Bacillus, Klebsiella, Enterobacter produced biosurfactants while all strains utilized aromatics (benzene and naphthalene). A combination of Pseudomonas, Bacillus, Lysinibacillus and Enterobacter was the most efficient crude oil degrading consortium with significant mean difference (p = 0.05) as evidenced by GC-analysis confirming a more than 25% reduction in total petroleum hydrocarbon (TPH) concentration of 1% crude oil within 48 h. Conclusively, the extant indigenous bacterial community in the impacted site has the natural capability to degrade hydrocarbons and could be further enhanced through biostimulation for in situ remediation.