Crude oil depletion by bacterial strains isolated from a petroleum hydrocarbon impacted solid waste management site in California

•Bioremediation case-study of a specific solid waste management site.•Serratia proteamaculans S1BD1 utilized wide spectrum of petroleum hydrocarbons.•Alcaligenes sp. OPKDS2 consumed 90% of BTEX in 15 days.•Rhodococcus erythropolis OSDS1 emulsified crude oil and removed 79% of n-alkanes.•Depletion efficiencies of the three strains ranged from 55 to 68%.

This research is part of a multidisciplinary research program to develop a bioremediation protocol for a solid waste management (SWM) site in Northern California - a site which is heavily contaminated with petroleum hydrocarbons. In this initial study, 30 bacterial strains were isolated and evaluated for their efficiencies to deplete crude oil. The 3 most efficient bacterial isolates for crude oil depletion were designated as S1BD1, OPKDS2, and OSDS1; they were identified as Serratia proteamaculans, Alcaligenes sp. and Rhodococcus erythropolis, respectively, based on partial 16S rRNA gene sequences. Determination of crude oil depletion efficiency by gas chromatography-mass spectrometry (GC-MS) revealed that Serratia proteamaculans S1BD1 was the most efficient (68.0 ± 1.78%), followed by Alcaligenes sp. OPKDS2 (63.7 ± 3.28%), and Rhodococcus erythropolis OSDS1 (54.9 ± 5.07%). S. proteamaculans S1BD1 was able to deplete a wide spectrum of carbon compounds within the individual components of crude oil. Alcaligenes sp. OPKDS2 was the most efficient at depleting BTEX (91.2 ± 1.90%), and R. erythropolis OSDS1 exhibited a substrate preference of n-alkanes. All three strains exhibited unusually high crude oil depletion efficiencies and tolerated a wide range of salinity and pH levels, which makes them excellent candidates for bioaugmentation of the SWM site.