Pyrene Biodegradation Potential of an Actinomycete, Microbacterium Esteraromaticum Isolated from Tropical Hydrocarbon-Contaminated Soi

Abstract

A novel pyrene-degrading actinomycete, phylogenetically identified as Microbacterium esteraromaticum strain SL9 was isolated from a polluted hydrocarbon-contaminated soil in Lagos, Nigeria. Growth of the isolate on pyrene was assayed using total viable counts, pyrene degradation was monitored using gas chromatography (GC-FID) while UV-Vis spectrophotometry was used to detect metabolites of pyrene degradation. The isolate tolerated salt concentration of up to 6%, grew luxuriantly on crude oil and exhibited weak utilization of fluorene, acenaphthene and engine oil. It resisted cefotaxime, ciprofloxacin and amoxicilin, but was susceptible to meropenem, linezolid and vancomycin. It also resisted elevated concentrations of heavy metals such as 1-5 mM lead and nickel. On pyrene, the isolate exhibited growth rate and doubling time of 0.023 h-1 and 1.25 h, respectively. It degraded 55.16 (27.58 mg L-1) and 89.28% (44.64 mg L-1) of pyrene (50 mg L-1) within 12 and 21 days respectively, while the rate of pyrene utilization was 0.09 mg L-1h-1. Catechol dioxygenase assay using UV-Vis spectrophotometry revealed the detection of meta cleavage compound, 2-hydroxymuconic semialdehyde in the crude cell lysate. The results of this study showed the catabolic versatility of Microbacterium species on hydrocarbon substrates and their potential as seeds for bioremediation of environments co-contaminated with polycyclic aromatic hydrocarbons and heavy metals.