Potential role of oxidative exoenzymes of the extremophilic fungus Pestalotiopsis palmarum BM‐04 in biotransformation of extra‐heavy crude oil

Abstract

Large amount of drilling waste associated with the expansion of the Orinoco Oil Belt (OOB), the biggest proven reserve of extra-heavy crude oil (EHCO) worldwide, is usually impregnated with EHCO and highly salinized water-based drilling fluids. Oxidative exoenzymes (OE) of the lignin-degrading enzyme system (LDS) of fungi catalyse the oxidation of a wide range of toxic pollutants. However, very little evidences on fungal degradation or biotransformation of EHCO have been reported, which contain high amounts of asphaltenes and its biodegradation rate is very limited. The aims of this work were to study the ability of Pestalotiopsis palmarum BM-04 to synthesize OE, its potential to biotransform EHCO and to survive in extreme environmental conditions. Enzymatic studies of the LDS showed the ability of this fungus to overproduce high amounts of laccase (LACp) in presence of wheat bran or lignin peroxidase (LIPp) with EHCO as sole carbon and energy source (1300 U mgP−1 in both cases). FT-IR spectroscopy with Attenuated Total Reflectance (ATR) analysis showed the enzymatic oxidation of carbon and sulfur atoms in both maltenes and asphaltenes fractions of biotreated EHCO catalysed by cell-free laccase-enriched OE using wheat bran as inducer. UV-visible spectrophotometry analysis revealed the oxidation of the petroporphyrins in the asphaltenes fraction of biotreated EHCO. Tolerance assays showed the ability of this fungus to grow up to 50 000 p.p.m. of EHCO and 2000 mM of NaCl. These results suggest that P. palmarum BM-04 is a hopeful alternative to be used in remediation processes in extreme environmental conditions of salinity and EHCO contamination, such as the drilling waste from the OOB.

Simultaneous valorization and biocatalytic upgrading of heavy vacuum gas oil by the biosurfactant‐producing Pseudomonas aeruginosa AK6U

“…In addition, there are some studies on crude oil. FT‐IR analysis revealed the enzymatic oxidation of carbon and sulfur atoms in both maltenes and asphaltenes from extraheavy crude oil treated with a cell‐free laccase produced by the fungus Pestalotiopsis palmarum BM‐04 (Naranjo‐Briceño et al ., ).…”

Roles of Thermophiles and Fungi in Bitumen Degradation in Mostly Cold Oil Sands Outcrops

“…Random microbial preoxidation is a necessary prerequisite comparable to the chemical preoxidation (ozonation) required for the more effective metabolism of the high diversity of naturally occurring NAs (19)(20)(21). The involvement of oxidative exoenzymes of the fungus Pestalotiopsis in the biotransformation of extra-heavy crude oil has been demonstrated (63), and this organism has also been shown to be involved in the enhanced biodegradation of asphalt (64). The split of the bioenergetic benefits of bitumen degradation between the two main consortium components, fungi and bacteria, is not yet understood.…”

Diverse Metabolic Capacities of Fungi for Bioremediation

“…Many hydrolytic enzymes which are known to show activity under extremophilic conditions have been reported to be involved in remediation processes under extreme conditions such as high salinity and extra-heavy crude oil (ECHO) contamination due to drilling waste from oil belts. Extreme acting laccases were observed to be responsible for bioremediation activity in Pestalotiopsis palmarum when wheat bran was present and lignin peroxidases were produced when extra heavy crude oil was the only carbon and energy source [48,49]. Other enzymes such as chitinases produced by a psychrophilic fungus, Lecanicillium muscarium, could be applied for enhancing the activity of insecticides owing to their ability for acting on insect chitin exoskeleton [50,51].…”