Colucci, Michael Sante2006-07-282006-07-2819991999http://hdl.handle.net/10012/436The psychotrophic Pseudomonas fluorescens used in this study demonstrated the ability to grow upon and utilize ethylene glycol and propylene glycol at 25*C and 5*C. Growth at both temperatures was marginally quicker with propylene glycol; but acclimation was faster when ethylene glycol was the substrate. Propylene glycol was more persistent than ethylene glycol at both 25*C and 5*C. When both substrates were present in the same reaction system, both were utilized concurrently, however, the relative recalcitrance of propylene glycol was still observed. The ability of the microorganism to biodegrade both clean and spent Union Carbide UCAR XL-54 (a deicer) and UCAR Ultra (an anti-icer) was shown. Growth occurred at 25*C at concentrations ranging from 10,000 mg/L to 100,000 mg/L (ethylene glycol), illustrating the ability of the microorganism to withstand and grow upon high concentrations of these formulations. At the lower concentrations, the generation times were quite similar to those obtained on pure ethylene glycol, suggesting that the additives present in these formulations were not particularly inhibitory to the microorganism. Utilization of the ethylene glycol in the clean UCAR deicing/anti-icing fluids (initial glycol content of 10,000 mg/L) was slightly enhanced compared to pure ethylene glycol at both 25*C and 5*C. Spent deicing fluids collected from Pearson International Airport in Toronto, Ontario were also shown to be readily biodegraded by the psychotroph. The spent fluids were diluted to approximately 10,000 mg/L after which growth and utilization were observed at both 25*C and 5*C. The spent fluids contained a natural population of microorganisms which were capable of ethylene glycol degradation at 25*C; however, at 5*C, they were inactive. These findings indicate the importance of using psychotrophs in low temperature applications. It was also determined that to promote the utilization of the spent fluids by either the natural population or the P. fluorescens inorganic supplements were required. Physiological studies investigating enzyme induction and substrate uptake indicated that ethylene glycol utilization and uptake are susceptible to external variables. Growth of the microorganism on propylene glycol did not induce the oxidase necessary for the oxidation of ethylene glycol into glycolate. This suggests that the oxidase activity involved in the initial oxidation of propylene glycol and ethylene glycol originates in two separate enzymes. Despite this, propylene glycol-grown cells were capable of inducing ethylene glycol uptake, however, the relative uptake was less then that observed for ethylene glycol grown cells. The ethylene glycol transport mechanism was found to be induced by certain monohydric and dihydric alcohols. The ability of these alcohols to induce transport was inversely related to the chain length of the alcohols tested. It was shown that non-growth supporting monohydric and dihydric alcohols were capable of competing with ethylene glycol for the transport mechanism. Similar findings were found with diethylene glycol, also a non-growth supporting substrate. It thus appears that this transport mechanism is not exclusive for ehtylene glycol. The use of 2,4-dinitrophenol and N.N'-dicyclohexylcarbodiimide indicated that the uptake mechanism was energy dependent. This suggests that ethylene glycol transport may involve a secondary active transport process such as symport. Environmental factors such as pH and temperature influenced ehtylene glycol uptake and it was determined that maximal uptake occurred at pH 7 and 25*C. Although the uptake decreased with a drop in temperature, it was significant that ethylene glycol uptake was still occurring at 0*C. Culture age and starvation were found to affect uptake and it was shown that cells in the early exponential phase of growth as well as those which were not subjected to nutrient limitation were capable of greater rates of ethylene glycol uptake In summary, the psychotrophic P. fluorescens demonstrated the ability to utilize clean and spent UCAR deicing/anti-icing fluids and the degradation rate may be influenced by external factors through their effect upon the uptake of ethylene glycol into the cell.application/pdf5250022 bytesapplication/pdfenCopyright: 1999, Colucci, Michael Sante. All rights reserved.Harvested from Collections CanadaDoctoral Thesis