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

Patrícia M Domingues,Vanessa Oliveira,Newton C M Gomes,Ângela Cunha,Luísa Seuanes Serafim

doi:10.3390/ijerph17051746

Patrícia M Domingues, Vanessa Oliveira + Show 3 more

Open Access

https://doi.org/10.3390/ijerph17051746

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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.

Highlights

Biosurfactants (BSFs) are amphiphilic molecules that alter the surface and interfacial tensions, promoting the dispersion of one phase into the other [1]
It is possible that the lack of accessible carbon sources in the inactive mud volcanoes (MVs), unlike the conditions at active MVs where hydrocarbons are expelled to the hydrosphere, has led to the development of bacteria with alternative strategies to use less available and accessible carbon sources
Twelve isolates belonging to Pseudomonas, Bacillus, Ochrobactrum, Brevundimonas, Psychrobacter, Staphylococcus, Marinobacter and Curtobacterium genera were isolated from selective cultures prepared with deep-sea and estuarine subaquatic sediments

Summary

Introduction

Biosurfactants (BSFs) are amphiphilic molecules that alter the surface and interfacial tensions, promoting the dispersion of one phase into the other [1]. BSFs can be produced by several microorganisms, including bacteria, and can be used for different purposes [2]. These include the increase of bioavailability of surface-bound and hydrophobic substrates, such as petroleum hydrocarbons (PHs), via direct interfacial contact and pseudo-solubilization [3,4]. BSF production is often associated with the capacity to use hydrocarbons as carbon sources [5] and this combination of traits is advantageous for PHs bioremediation strategies or microbial enhanced oil recovery (MEOR) [3,6].

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