Oil & Natural Gas Projects
Exploration and Production Technologies
Bioupgrading of Heavy Crudes Using Temperature- and Oil-Tolerant Biocatalysts
This project was funded through DOE's Natural Gas and Oil Technology Partnership
Program. The program establishes alliances that combine the resources and experience
of the nation's petroleum industry with the capabilities of the national laboratories
to expedite research, development, and demonstration of advanced technologies
for improved natural gas and oil recovery.
The goal of the project is to develop enzymatic biocatalysts that are active
in the oil phase and functional at moderate temperatures of 50-80° C.
Oak Ridge National Laboratory
Oak Ridge, TN
The biocatalyst developed in this project is expected to improve the efficiency
of refining heavy crude oils.
The work conducted in this project will allow more-efficient refining of heavy
Heavy crudes are commonly recalcitrant for conventional methods of refining.
This recalcitrance is imparted largely by polyaromatic linkages composed of
polyaromatic hydrocarbons (PAHs) and sulfur and nitrogen heterocycles. Polyaromatic
structures stabilize asphaltenic groups and protect metals from thermochemical
and biological removal. The same structures are substrates for oxidase enzymes.
Previous work has shown the capability of these oxidative enzymes to attack
polyaromatic compounds. This transformation may be the first step in the carbon-carbon
bond cleavage reactions; it thus may lead to a decrease in the molecular weight
of the oil and render sulfur, nitrogen, nickel, and vanadium groups more susceptible
to further biological or conventional treatment. It is a common practice to
use elevated temperatures during recovery of heavy oils. A combination of thermal
tolerance and resistance to inactivation in oil can be ideal properties for
an oil processing biocatalyst. This project will investigate development of
a catalyst to carry out the initial oxidation of PAH molecules and evolve it
to be operational at 50-80° C. while remaining active in the organic media.
A thermophilic peroxidase from an archaea/bacteria with optimum activity at
50-90°C will be used as a starting point for the development of enzymatic
The objective is to evolve the functionality (allowing conversion of oil compounds)
of the enzyme while improving temperature stability (temperature tolerance).
In the researcher's previous work, it was shown that the reactions of interest
cease to occur in a predominantly organic media such as oil. To activate the
enzymes in the oil phase, the enzymes have been modified via molecular genetic
techniques called Directed Evolution, resulting in catalysts that are stable
and functional in oil. In order to allow conversion using enzymes as catalysts,
it is important to know the partitioning of the enzyme between the oil and the
aqueous phase. This was investigated using the oxidase enzyme peroxidase. The
capability to operate at higher temperatures is useful in thermal recovery and
reduces the need for heat exchange equipment in the refining process. Oxidative
transformation of the polyaromatics were investigated as a strategy for biorefining
heavy crudes, with particular emphasis on lowering molecular weight, decreasing
viscosity, and rendering increased availability of sulfur, nitrogen, nickel,
and vanadium to further refining technologies.
The enzyme P450 from P. putida is known to have some activity for PAH conversion.
Another P450 enzyme-from Sulfolobus solftaricus, a thermophilic organism-is
capable of operation at elevated temperatures (80° C.); however, it does
not oxidize PAH compounds. In order to produce a thermostable PAH-oxidizing
enzyme, a hybrid of these two enzymes was produced.
Current Status (October 2005)
The project is complete.
Project Start: March 28, 2002
Project End: March 27, 2004
Anticipated DOE Contribution: $300,000
Performer Contribution: $30,000 (9% of total)
NETL - Kathleen Stirling (firstname.lastname@example.org or 918-699-2008)
ORNL - Abhijeet Borole (email@example.com or 865-576-7421)