Bioremediation of petroleum-contaminated soils using Streptomyces sp. Hlh1

Abstract

Purpose Bioremediation using microorganisms is a promising strategy to remediate soil with petroleum hydrocarbons.Streptomycessp. Hlh1, an endophytic strain, has previously demonstrated the ability to degrade crude petroleum in liquid culture.To apply this strain at field scale, it is necessary to test its ability to colonize the soil, compete with native microbiota, and removethe petroleum hydrocarbons under unfavorable conditions. Herein, a study was conducted to evaluate the performance ofStreptomyces sp. Hlh1 to remove crude petroleum from contaminated sterilized and non-sterilized soils.Materials and methods Soils samples, contaminated with 2%, 5%, and 10% of petroleum, were inoculated with Streptomycessp.Hlh1, and incubated at 30 °C for 4 weeks. At the end of bioremediation assays, the pollutant concentrations were determined byGas chromatography flame ionization detector and the degradation rates were also calculated. The survival of the strain in the soilwas estimated and the toxicity of metabolites was evaluated on Lactuca sativa.Results and discussion Streptomyces sp. Hlh1 was able to grow and remove total petroleum hydrocarbons (TPH), n-alkanes, andaromatic hydrocarbons found in soil samples. In sterilized soil samples, Streptomyces sp. Hlh1 removed up to 40% of TPH at aninitial concentration of 10%. Whereas, the maximum TPH removal reached was 55% in non-sterilized soil at an initial concentration of 2%. In addition, it was observed that the degradation of aromatic hydrocarbons was more active than n-alkanes. Thestrain grew well and produced high biomass in contaminated soil. Lettuce seedling was found to be the adequate bioindicator toassess the toxicity of petroleum end products. Streptomyces sp. Hlh1 performed a successful bioremediation, which was confirmed through the phytotoxicity test.Conclusions The study shows the first insight of the contribution of free endophytic actinobacterial strain in the bioremediation ofpetroleum-contaminated soil; therefore, it suggests that Streptomyces sp. Hl1 can be usefully exploited at field scale.