Extra-Heavy Crude Oil Degradation by Alternaria sp. Isolated from Deep-Sea Sediments of the Gulf of Mexico

Lucia Romero-Hernández,María Dolores Camacho-López,Rafael Vázquez-Duhalt,Itandehui Betanzo-Gutiérrez,Meritxell Riquelme,Patricia Velez

doi:10.3390/app11136090

Abstract

The Gulf of Mexico (GoM) is an important source of oil for the United States and Mexico. There has been growing interest, particularly after the Deepwater Horizon oil spill, in characterizing the fungal diversity of the GoM and identifying isolates for use in the bioremediation of petroleum in the event of another spill. Most studies have focused on light crude oil bioremediation processes, while heavy crude oil (HCO) and extra-heavy crude oil (EHCO) have been largely ignored. In this work, we evaluated the ability of fungal isolates obtained from deep-sea sediments of the Mexican economic exclusive zone (EEZ) of the GoM to degrade HCO (16–20° API) and EHCO (7–10° API). Alternaria sp., Penicillium spp., and Stemphylium sp. grew with HCO as the sole carbon source. Remarkably, Alternaria sp. was the only isolate able to grow with EHCO as the sole carbon source, degrading up to 25.6% of the total EHCO and 91.3% of the aromatic fraction, as demonstrated by gas chromatography analysis of the saturate, aromatic, and polar fractions. These findings proved to be significant, identifying Alternaria sp. as one of the few fungi reported so far capable of degrading untreated EHCO and as a suitable candidate for bioremediation of EHCO in future studies.

Highlights

Crude oil has become the most important source of energy for humankind
Based on the phylogenetic analysis of the sequenced internal transcribed spacer (ITS) region, 18S rRNA gene, and β-tubulin gene, we unequivocally identified Cladosporium halotolerans to the species level (≥99% beta-tubulin sequence similarity and supported by 97% bootstrap value) and four isolates to the genus level (Table S3 and Figure 3)
Following the 2010 Deepwater Horizon oil spill, fungal strains from oil-soaked sand patties collected from beaches [41] and bacteria from oiled beach sands at Pensacola Beach, FL, USA [42], both sites located in the American exclusive zone (EEZ), were identified as potential bioremediation microorganisms

Summary

Introduction

Crude oil has become the most important source of energy for humankind. It has been estimated that, by 2035, it will supply more than one-third of the total global energy demands [1,2]. Alternative green energy sources with lower carbon footprints (e.g., solar and eolic) have improved to become economically viable, but they are insufficient to supply the increasing energy demand [6]. Heavy and extra-heavy crude oil (HCO and EHCO, respectively) make up 70% of the world’s oil reserves [7] Their high content in resins and asphaltenes represents a significant challenge for its extraction, production, and refinement, in addition to the associated risk of accidental spills. Polycyclic aromatic hydrocarbons (PHAs) are present in a significant ratio in HCO and EHCO These fractions are one of the major concerns in oil spills, given their resistance to microbial degradation [8], long-term persistence in the environment [9], and ecotoxicity [10,11,12]

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Conclusion