Evaluation of pilot scale in-vitro and ex-situ hydrocarbon bioremediation potential of two novel indigenous strains of Bacillus vallismortis

Abstract

Two novel indigenous strains of Bacillus vallismortis viz., DU12 (GenBank accession: MK177189) and DU14 (GenBank accession: MN011811) were isolated from oil impacted soil samples collected from automobile garages located in Dibrugarh town of Assam, India and were identified based on 16S rDNA gene sequencing. The two strains could successfully degrade 26.34% and 53.85% of used engine oil under in-vitro conditions in liquid culture after 28 days of treatment. The extracted biosurfactant from B. vallismortis strain DU12 showed E 24 index of 15%, 18%, and 15%, respectively, against used engine oil, diesel, and kerosene whereas, isolate DU14 showed 35% against both used engine oil and diesel and 20% against kerosene. FTIR spectra of the extracted biosurfactants from the bacterial isolates confirmed the presence of ʋC–H (stretch), ʋCH2, and ʋC–H (bend) in common. Pilot scale ex-situ bioremediation assay on used engine oil and diesel-contaminated soil samples by both the isolates showed similar germination rate of Vigna radiata and Cicer arietium seeds, respectively, just after 20 days of treatment. Both V. radiata and C. arietium seedlings showed significant growth after bioremediation as compared to the respective controls which also advocates their future potential scope in treatment of petroleum contaminated sites.