Role of hemoglobin in hemoglobin-based remediation of the crude oil-contaminated soil Jin-Kyung Hong, Eun Hea Jho ⁎, Hyo Sub Choi, Guyoung Kang Department of Environmental Science, Hankuk University of Foreign Studies, 81 Oedae-ro, Mohyeon-myeon, Cheoin-gu, Youngin-si, Gyeonggi-do 17035, Republic of Korea HIGHLIGHTS • Hemoglobin (Hb) imposed a selective force on surfactant-producing bacterial species. • Hb application promoted TPH removal in the aged crude oil-contaminated soil. • Hb-based biocatalytic reaction removed TPH from the crude oil-contaminated soil. • Bacterial community structure recovered better after the biocatalytic reaction. • Hb-based remediation can be a viable option for crude oil-contaminated soils. GRAPHICAL ABSTRACT abstract article info Article history: Received 18 September 2017 Received in revised form 24 January 2018 Accepted 24 January 2018 Available online xxxx Editor: Simon Pollard This study investigated the changes in the indigenous microbial community structure with hemoglobin (Hb) ap- plication to determine the role of Hb in Hb-based remediation of crude oil-contaminated soil. The phylogenetic diversity of the bacterial community showed that the Hb addition selected surfactants-producing species, thereby, promoting TPH degradation. The significant increase in the CO 2 generation, which can be related to the increase in the bacterial abundance inferred from the 16S rRNA gene copy number, supports the enhanced TPH degradation with Hb application. The similar residual TPH concentrations in the presence of only hydrogen peroxide (H 2 O 2 ) and both Hb and H 2 O 2 suggested that the role of Hb as a catalyst was not as significant as the role of Hb as a nutrient. Also, in the presence of H 2 O 2 , a greater recovery of the microbial community structure was observed with the double Hb injection than the single Hb injection. Overall, this study shows that the Hb- based remediation strategies via microbial metabolism can be successfully applied to remediate the crude-oil contaminated Kuwaiti soil. © 2018 Elsevier B.V. All rights reserved. Keywords: Hemoglobin Microbial community Crude oil-contaminated soil TPH Biocatalytic reaction 1. Introduction Soils contaminated with crude oil or total petroleum hydrocarbons (TPH) have been largely treated by using biological processes; however, there are many conditions that can limit remediation efficiency of bio- logical treatments such as nutrient availability (i.e., C/N ratio) and con- taminant availability, which can be affected by crude oil concentrations, sorption to soil, and changing chemical composition of crude oil with weathering (Leahy and Colwell, 1990; Saeed et al., 1998). After weathering, loss of volatiles and easily biodegradable compounds results in soils having compounds that are more resistant to biodegradation. Chemical oxidation processes have widely been combined with bio- logical treatments as a pre-treatment or post-treatment to enhance the remediation efficiency of contaminated soils (Goi et al., 2006). The major disadvantage of using chemical oxidation processes as a pre- treatment is possible negative effects on TPH-degrading bacteria after exposure to chemical oxidation that could lead to loss of the degradabil- ity of bacteria (Jho et al., 2014; Lu et al., 2010). Conditioning of the Science of the Total Environment 627 (2018) 1174–1181 ⁎ Corresponding author. E-mail address: ehjho@hufs.ac.kr (E.H. Jho). https://doi.org/10.1016/j.scitotenv.2018.01.243 0048-9697/© 2018 Elsevier B.V. All rights reserved. Contents lists available at ScienceDirect Science of the Total Environment journal homepage: www.elsevier.com/locate/scitotenv