Todd Cort - Academia.edu (original) (raw)

Papers by Todd Cort

Biodegradation, 2003

Biodegradation of petroleum hydrocarbon contamination is a common method for remediating soils an... more Biodegradation of petroleum hydrocarbon contamination is a common method for remediating soils and groundwater. Due to complexities with field-scale studies, biodegradation rates are typically evaluated at the bench-scale in laboratory studies. However, important field conditions can be difficult to mimic in the laboratory. This study investigates three scaling factors that can impact laboratory biodegradation rates and that are frequently unaccounted for in typical laboratory experimental procedures. These factors are soil heterogeneity, morphology of petroleum hydrocarbon non-aqueous phase liquids (NAPLs) and soil moisture distribution. The effects of these factors on the biodegradation rate of diesel NAPL is tested under a variety of experimental procedures from well-mixed batch studies to four-foot static soil columns. The results indicate that a high degree of variability results from even small-scale heterogeneities. In addition, it appears that as the experimental scale incre...

Journal of Zoology, 1995

ABSTRACT We have demonstrated that snakes and some other reptiles normally possess high plasma zi... more ABSTRACT We have demonstrated that snakes and some other reptiles normally possess high plasma zinc concentrations. These levels are similar to those measured in teleost fish. Plasma zinc levels in the range of snakes and teleosts have been shown to be toxic to crocodilians and mammals. Zinc has been shown to bind to a specific protein in albacore and winter flounder serum. Previous experiments suggested a similar protein in snake plasma. Western blot techniques were used to search for proteins capable of binding large quantities of zinc with high affinity in the plasma of a wide range of vertebrate species. These data were compared to plasma zinc concentrations measured by atomic absorption spectrophotometry. A correlation between high zinc levels and the presence of specific zinc-binding proteins different from mammalian albumin was observed. Snakes and teleost fish demonstrated both very high plasma zinc concentrations and a zinc-binding protein. Teleosts and snakes have significantly higher levels of plasma zinc than birds and mammals.

Journal of Zoology, 1995

... Most were in the same range as snakes (Table IV), but others were closer to turtle values ...... more ... Most were in the same range as snakes (Table IV), but others were closer to turtle values ... 1. (a) Mean plasma zinc concentrations (k the standard error of the mean) of snakes, lizards, turtles, crocodiles, birds and mammals ... The zinc values for the reptiles are taken from Tables ILIV ...

Journal of Environmental Engineering, 2006

Journal of Environmental Engineering, 2000

ABSTRACT The effects of temperature and surfactant concentration on the degradation of pentachlor... more ABSTRACT The effects of temperature and surfactant concentration on the degradation of pentachlorophenol (PCP) by a pure culture of Sphingomonas chlorophenolicum sp. Strain RA2 were studied. An anionic, a cationic, and two nonionic surfactants were tested at concentrations above and below their critical micellar concentrations (CMC). Each surfactant was tested at four temperatures between 10 and 25 degrees C. PCP degradation curves were modeled based on Monod growth kinetics. Degradation curves were also fit using inhibition models accounting for the effects of temperature and surfactant concentration. No PCP degradation activity was observed in the presence of the cationic surfactant. The anionic surfactant had a more inhibitory effect at lower concentrations than the nonionic surfactants, which occurred at surfactant concentrations well below the CMC at all temperatures. Nonionic surfactants showed no inhibition at sub-CMC concentrations and higher temperatures. In general, the surfactants caused more inhibition at lower temperatures. The exception was a slight enhancement of PCP degradation at 10 degrees C for low concentrations of the nonionic surfactants.

Biotechnology and Bioengineering, 2002

A kinetic model is used to describe the effect of the nonionic surfactant Tergitol NP-10 (TNP10) ... more A kinetic model is used to describe the effect of the nonionic surfactant Tergitol NP-10 (TNP10) on pentachlorophenol (PCP) biodegradation by Sphingomonas chlorophenolica sp. strain RA2. Different initial biomass to initial substrate ratios ranging from 13 to 418 were tested with 23 TNP10 concentrations ranging from 0 to 1500 mg/L. Tests were also conducted at 10°C and 20°C. No PCP biodegradation inhibition was observed at concentrations below the critical micelle concentration (CMC) of 50 mg/L. TNP10 concentrations above 100 to 200 mg/L were increasingly inhibitory to PCP biodegradation rates. This inhibition was best described by the Monod kinetic equation wherein the effect of TNP10 inhibition is re¯ected in the half-saturation constant (K s ). The value of the K s increased from between 1.5 and 13.5 mg/L with no surfactant present to 44 to 131 mg/L at 1000 mg/L TNP10. Using a standard competitive inhibition approach, the inhibition constant for TNP10 was approximately 100 mg/L at both 10°C and 20°C. ã

Biotechnology and Bioengineering, 2005

The simultaneous biodegradation of the nonionic surfactant Tween 20 (Tw20) and pentachlorophenol ... more The simultaneous biodegradation of the nonionic surfactant Tween 20 (Tw20) and pentachlorophenol (PCP) by Sphingomonas chlorophenolica sp. Strain RA2 (RA2) was measured. As a sole substrate, Tw20 biodegradation was best described by the Contois kinetic model. During concurrent biodegradation of Tw20 and PCP, the biodegradation rates of Tw20 were not significantly affected by 50 or 100 mg/L PCP, but were significantly inhibited by 500 mg/L PCP. Decreases in cell yield in the presence of PCP suggest that PCP was acting as an uncoupler. Cultures were pre-grown on PCP or Tw20 before degradation of PCP to evaluate enzyme induction effects, and long lags before PCP biodegradation after growth on Tw20 occurred. Although biokinetic models could accurately describe some of the data sets of RA2 growth and Tw20 and PCP degradation, finding a single set of kinetic parameters that predicted all dual substrate tests was not achieved. The complicating factors to modeling PCP and Tw20 interactions are described and may be more widely applicable to the biodegradation of toxic organic compounds in the presence of a biodegradable surfactant. B 2005 Wiley Periodicals, Inc.

Water Research, 2002

Several potential mechanisms of surfactant-induced inhibition of pentachlorophenol (PCP) biodegra... more Several potential mechanisms of surfactant-induced inhibition of pentachlorophenol (PCP) biodegradation were tested using a pure bacterial culture of Sphingomonas chlorophenolicum sp. Strain RA2. PCP degradation, glucose degradation, and oxygen uptake during endogenous conditions and during glucose degradation were measured for batch systems in the presence of the nonionic surfactant Tergitol NP-10 (TNP10). TNP10 did not exert toxicity on RA2 as measured by dissolved oxygen uptake rates under endogenous conditions and glucose biodegradation rates. TNP10 reduced the substrate inhibition effect of PCP at high PCP concentrations, resulting in faster PCP degradation rates at higher concentrations of TNP10. Calculations of a micelle partition coefficient (K mic ) show that PCP degradation rates in the presence of surfactant can be explained by accounting for the amount of PCP available to the cell in the aqueous solution. A model is discussed based on these results where PCP is sequestered into micelles at high TNP10 concentrations to become less available to the bacterial cell and resulting in observed inhibition. Under substrate toxicity conditions, the same mechanism serves to increase the rate of PCP biodegradation by reducing aqueous PCP concentrations to less toxic levels. r

Biodegradation, 2003

Biodegradation of petroleum hydrocarbon contamination is a common method for remediating soils an... more Biodegradation of petroleum hydrocarbon contamination is a common method for remediating soils and groundwater. Due to complexities with field-scale studies, biodegradation rates are typically evaluated at the bench-scale in laboratory studies. However, important field conditions can be difficult to mimic in the laboratory. This study investigates three scaling factors that can impact laboratory biodegradation rates and that are frequently unaccounted for in typical laboratory experimental procedures. These factors are soil heterogeneity, morphology of petroleum hydrocarbon non-aqueous phase liquids (NAPLs) and soil moisture distribution. The effects of these factors on the biodegradation rate of diesel NAPL is tested under a variety of experimental procedures from well-mixed batch studies to four-foot static soil columns. The results indicate that a high degree of variability results from even small-scale heterogeneities. In addition, it appears that as the experimental scale incre...

Journal of Zoology, 1995

ABSTRACT We have demonstrated that snakes and some other reptiles normally possess high plasma zi... more ABSTRACT We have demonstrated that snakes and some other reptiles normally possess high plasma zinc concentrations. These levels are similar to those measured in teleost fish. Plasma zinc levels in the range of snakes and teleosts have been shown to be toxic to crocodilians and mammals. Zinc has been shown to bind to a specific protein in albacore and winter flounder serum. Previous experiments suggested a similar protein in snake plasma. Western blot techniques were used to search for proteins capable of binding large quantities of zinc with high affinity in the plasma of a wide range of vertebrate species. These data were compared to plasma zinc concentrations measured by atomic absorption spectrophotometry. A correlation between high zinc levels and the presence of specific zinc-binding proteins different from mammalian albumin was observed. Snakes and teleost fish demonstrated both very high plasma zinc concentrations and a zinc-binding protein. Teleosts and snakes have significantly higher levels of plasma zinc than birds and mammals.

Journal of Zoology, 1995

... Most were in the same range as snakes (Table IV), but others were closer to turtle values ...... more ... Most were in the same range as snakes (Table IV), but others were closer to turtle values ... 1. (a) Mean plasma zinc concentrations (k the standard error of the mean) of snakes, lizards, turtles, crocodiles, birds and mammals ... The zinc values for the reptiles are taken from Tables ILIV ...

Journal of Environmental Engineering, 2006

Journal of Environmental Engineering, 2000

ABSTRACT The effects of temperature and surfactant concentration on the degradation of pentachlor... more ABSTRACT The effects of temperature and surfactant concentration on the degradation of pentachlorophenol (PCP) by a pure culture of Sphingomonas chlorophenolicum sp. Strain RA2 were studied. An anionic, a cationic, and two nonionic surfactants were tested at concentrations above and below their critical micellar concentrations (CMC). Each surfactant was tested at four temperatures between 10 and 25 degrees C. PCP degradation curves were modeled based on Monod growth kinetics. Degradation curves were also fit using inhibition models accounting for the effects of temperature and surfactant concentration. No PCP degradation activity was observed in the presence of the cationic surfactant. The anionic surfactant had a more inhibitory effect at lower concentrations than the nonionic surfactants, which occurred at surfactant concentrations well below the CMC at all temperatures. Nonionic surfactants showed no inhibition at sub-CMC concentrations and higher temperatures. In general, the surfactants caused more inhibition at lower temperatures. The exception was a slight enhancement of PCP degradation at 10 degrees C for low concentrations of the nonionic surfactants.

Biotechnology and Bioengineering, 2002

A kinetic model is used to describe the effect of the nonionic surfactant Tergitol NP-10 (TNP10) ... more A kinetic model is used to describe the effect of the nonionic surfactant Tergitol NP-10 (TNP10) on pentachlorophenol (PCP) biodegradation by Sphingomonas chlorophenolica sp. strain RA2. Different initial biomass to initial substrate ratios ranging from 13 to 418 were tested with 23 TNP10 concentrations ranging from 0 to 1500 mg/L. Tests were also conducted at 10°C and 20°C. No PCP biodegradation inhibition was observed at concentrations below the critical micelle concentration (CMC) of 50 mg/L. TNP10 concentrations above 100 to 200 mg/L were increasingly inhibitory to PCP biodegradation rates. This inhibition was best described by the Monod kinetic equation wherein the effect of TNP10 inhibition is re¯ected in the half-saturation constant (K s ). The value of the K s increased from between 1.5 and 13.5 mg/L with no surfactant present to 44 to 131 mg/L at 1000 mg/L TNP10. Using a standard competitive inhibition approach, the inhibition constant for TNP10 was approximately 100 mg/L at both 10°C and 20°C. ã

Biotechnology and Bioengineering, 2005

The simultaneous biodegradation of the nonionic surfactant Tween 20 (Tw20) and pentachlorophenol ... more The simultaneous biodegradation of the nonionic surfactant Tween 20 (Tw20) and pentachlorophenol (PCP) by Sphingomonas chlorophenolica sp. Strain RA2 (RA2) was measured. As a sole substrate, Tw20 biodegradation was best described by the Contois kinetic model. During concurrent biodegradation of Tw20 and PCP, the biodegradation rates of Tw20 were not significantly affected by 50 or 100 mg/L PCP, but were significantly inhibited by 500 mg/L PCP. Decreases in cell yield in the presence of PCP suggest that PCP was acting as an uncoupler. Cultures were pre-grown on PCP or Tw20 before degradation of PCP to evaluate enzyme induction effects, and long lags before PCP biodegradation after growth on Tw20 occurred. Although biokinetic models could accurately describe some of the data sets of RA2 growth and Tw20 and PCP degradation, finding a single set of kinetic parameters that predicted all dual substrate tests was not achieved. The complicating factors to modeling PCP and Tw20 interactions are described and may be more widely applicable to the biodegradation of toxic organic compounds in the presence of a biodegradable surfactant. B 2005 Wiley Periodicals, Inc.

Water Research, 2002

Several potential mechanisms of surfactant-induced inhibition of pentachlorophenol (PCP) biodegra... more Several potential mechanisms of surfactant-induced inhibition of pentachlorophenol (PCP) biodegradation were tested using a pure bacterial culture of Sphingomonas chlorophenolicum sp. Strain RA2. PCP degradation, glucose degradation, and oxygen uptake during endogenous conditions and during glucose degradation were measured for batch systems in the presence of the nonionic surfactant Tergitol NP-10 (TNP10). TNP10 did not exert toxicity on RA2 as measured by dissolved oxygen uptake rates under endogenous conditions and glucose biodegradation rates. TNP10 reduced the substrate inhibition effect of PCP at high PCP concentrations, resulting in faster PCP degradation rates at higher concentrations of TNP10. Calculations of a micelle partition coefficient (K mic ) show that PCP degradation rates in the presence of surfactant can be explained by accounting for the amount of PCP available to the cell in the aqueous solution. A model is discussed based on these results where PCP is sequestered into micelles at high TNP10 concentrations to become less available to the bacterial cell and resulting in observed inhibition. Under substrate toxicity conditions, the same mechanism serves to increase the rate of PCP biodegradation by reducing aqueous PCP concentrations to less toxic levels. r