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& Staff > Dr. Brent Peyton
Microbial Activity and Alkaline Hydrolysis in Thermal Environments
Biotransformation Kinetics of Thermophilic Hydrocarbon Degraders: Biodegradation
rates of polycyclic aromatic hydrocarbons (PAHs) are typically low at mesophilic
conditions and it is believed that the kinetics of degradation is controlled
by PAH solubility and mass transfer rates. My group has focused on the interplay
between mass transport and microbial reaction rates in thermal systems. Three
thermophilic Geobacilli were isolated that grew on phenanthrene at
60°C and degraded the PAH more rapidly than other reported mesophiles.
Our results show that while solubilization rates of PAHs are significantly
enhanced at elevated temperatures, the biodegradation of PAHs under thermophilic
conditions is still mass transfer limited due to enhanced degradation rates. Solubility
tests were performed on phenanthrene, fluorene and fluoranthene at 20°C,
40°C and 60°C and, as expected, a significant increase in the equilibrium
solubility concentration and of the rate of dissolution of these PAHs was observed
with increasing temperature. A first order model was used to describe the PAH
dissolution kinetics and the thermodynamic property changes associated with
the dissolution process (enthalpy, entropy and Gibb’s free energy of
solution) were evaluated. Further, other relevant thermodynamic properties
for these PAHs, including the activity coefficients at infinite dilution, Henry’s
law constants and octanol-water partition coefficients, were calculated in
the temperature range 20-60°C. These studies are currently being
extended to high pH conditions to take advantage of synergistic effects of
hydrolytic chemical reactions that occur under alkaline conditions.
Microbial Activity in Thermoalkaline Springs: Alkaline hydrolysis
is the degradation of organic compounds at high temperature and pH values of
8 and higher. Many compounds of military, national security, agricultural,
and environmental significance can be destroyed by this reaction, including
natural organic matter, explosives, propellants, nerve gasses, pesticides,
renewable biomass, and chlorinated organics. Typically, microorganisms
are not active at the high pH and temperature used in alkaline hydrolysis,
but naturally occurring organisms exist in Yellowstone National Park that are
highly adapted to these extreme conditions. Microorganisms known as
alkaliphiles (interpreted literally as alkali loving) thrive and grow in high
pH solutions (pH 9 to 11). In addition, thermophilic (heat loving) bacteria
are active at temperatures ranging from 50°C to boiling. Organisms that
flourish at both high pH and high temperature are called thermoalkaliphiles.
Through the use of these unique bacteria, a combined chemical and biological
system could be used to quickly degrade hazardous compounds, even high explosives
(e.g., TNT) and nerve gas agents. The thermoalkaliphilic system could
be used for on-site treatment of a variety of compounds that are currently
difficult to dispose. An example of a potential application envisioned
includes a mobile, small-scale reactor for destruction of military explosives
in the field. For domestic use, a reliable on-site treatment for
farm pesticides would discourage the release of unused herbicides and insecticides. Further,
studies on the unique capabilities of thermoalkaliphilic organisms will also
help improve our understanding of the role of naturally occurring organic matter
in thermoalkaline environments.
 Dr.
Brent Peyton Sampling
at a pH 10 hot spring near
Witch Creek in the Heart
Lake Geyser Basin, YNP.
Current Laboratory Personnel:
Catherine Albaugh, Ph.D. Student
John Aston, Ph.D. Student
James Moberly, Ph.D. Student
Abbie Richards, Ph.D. Student
Storm Shirley, Ph.D. Student
Michael VanEngelen, Ph.D. Student
Sutapa Barua, M.S. Student
Sarah Mullowney, Undergraduate Student
Joe Sibbert, Undergraduate Student
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