Biosurfactant Production in Sub-Oxic Conditions Detected in Hydrocarbon-Degrading Isolates from Marine and Estuarine Sediments

abstract

Hydrocarbon bioremediation in anoxic sediment layers is still challenging not only because it involves metabolic pathways with lower energy yields but also because the production of biosurfactants that contribute to the dispersion of the pollutant is limited by oxygen availability. This work aims at screening populations of culturable hydrocarbonoclastic and biosurfactant (BSF) producing bacteria from deep sub-seafloor sediments (mud volcanos from Gulf of Cadiz) and estuarine sub-surface sediments (Ria de Aveiro) for strains with potential to operate in sub-oxic conditions. Isolates were retrieved from anaerobic selective cultures in which crude oil was provided as sole carbon source and different supplements were provided as electron acceptors. Twelve representative isolates were obtained from selective cultures with deep-sea and estuary sediments, six from each. These were identified by sequencing of 16S rRNA gene fragments belonging to Pseudomonas, Bacillus, Ochrobactrum, Brevundimonas, Psychrobacter, Staphylococcus, Marinobacter and Curtobacterium genera. BSF production by the isolates was tested by atomized oil assay, surface tension measurement and determination of the emulsification index. All isolates were able to produce BSFs under aerobic and anaerobic conditions, except for isolate DS27 which only produced BSF under aerobic conditions. These isolates presented potential to be applied in bioremediation or microbial enhanced oil recovery strategies under conditions of oxygen limitation. For the first time, members of Ochrobactrum, Brevundimonas, Psychrobacter, Staphylococcus, Marinobacter and Curtobacterium genera are described as anaerobic producers of BSFs.

keywords

POLYCYCLIC AROMATIC-HYDROCARBONS; COLD SEEP SEDIMENTS; DEEP-SEA SEDIMENTS; BACTERIAL COMMUNITIES; OIL-RECOVERY; PSEUDOMONAS-AERUGINOSA; REDUCING BACTERIA; SP NOV.; DIVERSITY; BIODEGRADATION

subject category

Environmental Sciences & Ecology; Public, Environmental & Occupational Health

authors

Domingues, PM; Oliveira, V; Serafim, LS; Gomes, NCM; Cunha, A

our authors

acknowledgements

This research was funded by University of Aveiro and FCT/MEC through the financial support to the research units CESAM (UIDB/50017/2020 and UIDP/50017/2020) and CICECO-Aveiro Institute of Materials (UIDB/50011/2020 and UIDP/50011/2020). Further funding was provided by the Portuguese Foundation for Science and Technology (FCT) in the form of a PhD grant to P. M. Domingues (SFRH/BD/88162/2012) and Post-Doc grant to V. Oliveira (SFRH/BPD/101919/2014).

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