Biomedical Engineering Reference
In-Depth Information
CHAPTER 9
BIOAUGMENTATION WITH
PSEUDOMONAS
STUTZERI
KC FOR CARBON TETRACHLORIDE
REMEDIATION
Craig S. Criddle,
1
Michael J. Dybas,
2
Gregory M. Tatara,
3
Lance B. Warnick,
4
Georgina Vidal-Gavilan,
5
A. P. Robertson
1
and Thomas A. Lewis
6
1
Stanford University, Stanford, CA 94305;
2
M. Dybas and Associates, LLC, Charlotte, MI
48813;
3
Genoa Township, Brighton, MI 48116;
4
Aspen Engineering, Nampa, ID 83686;
5
D'ENGINY BIOREM S.L., Barcelona 08006, Spain;
6
Montana State University Billings,
Billings, MT 59105
9.1 INTRODUCTION AND RATIONALE
Until the late 1980s, carbon tetrachloride (CT) was produced in large quantities for use as a
dry cleaning agent, grain silo fumigant, degreasing agent and feedstock for refrigerant
synthesis (ATDSR,
2005
). In 1987, production and consumption of CT was banned under the
terms of the Montreal protocol due to its role as an ozone-depleting agent. However CT is still
used in some industrial applications and is a regulated groundwater contaminant, present at 201
of the 1,264 National Priorities List sites in the United States (USEPA,
2009
). At high levels, CT
can damage the liver, kidneys and nervous system, and it can cause cancer in animals (ATSDR,
2005
). Its fate in the environment and within cells is a consequence of its structure; its fully
oxidized carbon atom and tetrahedral chlorine shield confer resistance to oxidation and
hydrolysis, but susceptibility to reduction (Vogel et al.,
1987
).
Many reducing agents found within living cells, including vitamin B12 (Hashsham et al.,
1995
), iron porphyrin-based proteins such as cytochromes (Picardal et al.,
1993
) and menaqui-
nones (Fu et al.,
2009
), fortuitously reduce CT through one-electron transfers producing CCl
3
free radicals. The radical is implicated in membrane lipid peroxidation (Trimble,
2000
), with
hydrogen abstraction and concomitant formation of chloroform (CF), another contaminant of
human health concern. It is tempting to speculate that indiscriminate intracellular reactivity of
CT and CCl
3
explains why no microorganism has yet been isolated that can couple growth and
oxidation of an electron donor to CT respiration. It also explains why pathway control, and in
particular avoiding the formation of CF, is a critical challenge for CT remediation.
This chapter focuses on aquifer bioremediation by bioaugmentation with denitrifying
Pseudomonas stutzeri
KC, a field-demonstrated strategy that enables pathway control and
degradation of CT to levels below the U.S. Environmental Protection Agency (USEPA) maxi-
mum contaminant level (MCL) of five parts per billion (ppb, or micrograms per liter [
m
g/L]).
Strain KC is a highly motile (chemotactic toward nitrate) facultative aerobe capable of
complete denitrification. Most denitrifying microorganisms convert CT to CF, but strain KC
mediates dechlorination through an extracellular process and pathway that does not produce CF
and does so at rates that exceed the rates at which other microbial populations can generate CF,
thus minimizing or avoiding CF formation. The key to this bioaugmentation strategy is that
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