Graduate Theses and Dissertations
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This collections holds all University of Saskatchewan graduate level electronic theses and dissertations (ETDs) published since 2005. More than 700 print theses published before 2005 have been digitized and added to the collection as well.
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Browsing Graduate Theses and Dissertations by Subject "1,3-Propanediol"
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Item Microbial Production and Characterization of 1,3-PDO by a Novel Lactobacillus panis Strain(2013-07-29) Grahame, Douglas; Tanaka, Takuji; Tyler, Robert T.; Korber, Darren R.; Reaney, Martin J.; Siciliano, Steven D.Interest in the aliphatic carbon compound 1,3-propanediol (1,3-PDO) has risen over the past 15 years. In part, this interest is due to the ability of 1,3-PDO to generate a variety of industrially relevant products such as the biodegradable polymer, polytrimethylene terephtalate. Our research group previously reported the identification of a novel Lactobacillus panis PM1 isolate capable of converting glycerol to 1,3-PDO. In this body of work, the effects of various process parameters and the ability of the novel L. panis isolate to produce 1,3-PDO in static and fed-batch cultures were examined. Data collected indicated that the concentrations of glycerol, and glucose, and pH, play a vital role in the optimized production of 1,3-PDO. Optimal conditions for the production of 1,3-PDO were determined to include: i) carbon-limited culture, defined as below 50 mM glucose and ii) growth at 37°C without agitation in the presence of glycerol (150 – 250 mM) at an elevated pH of 9 – 10. Factors such as inoculum size and temperature (OD600 in the range of 0.5 – 2 and a temperature range from 15° - 37°C) in a two-step fermentation showed insignificant variance in the production of 1,3-PDO. Initial fed-batch trials reflected the importance of pH on culture viability. A pH of 8 was determined to be necessary within culture parameters for the fed-batch production of 1,3-PDO. Further, the molar concentrations of 1,3-PDO produced were found to vary only slightly between fed batch culture and a static culture. The variance of 1,3-PDO production between the static and fed-batch trials was found to be 9.1 ± 4.9 mM for an average culture producing 85.3 ± 12.0 mM of 1,3-PDO. However, the mol concentrations of 1,3-PDO produced were found to be significantly higher with 22.3 ± 1.6 versus 5.3 ± 0.7 mmol 1,3-PDO produced for the fed batch versus the static cultures, respectively. The duration of 1,3-PDO production was found to be extended in the fed-batch model of production with increased levels of 1,3-PDO being produced over 120 hours. The cloning and characterization of the recombinant 1,3-PDO NAD+-dependent oxidoreductase also were explored to gain further insight into the native production of 1,3-PDO. Initial kinetic studies determined a Km value of 1.28 ± 0.57 mM for NAD+ versus 23.8 ± 1.1 mM for 1,3-PDO. The Km values demonstrated that the availability of NAD+/NADH may be a determining factor in 1,3-PDO concentration. These findings support the literature and the conclusion that the bottleneck in 1,3-PDO production lies in maintaining an available pool of NAD+/NADH while mitigating negative effects associated with the accumulation of toxic byproducts.