Browsing by Author "Moll, Karen Margaret"

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Alkaline microalgae from Yellowstone National Park: physiological and genomic characterization for biofuel production
(Montana State University - Bozeman, College of Agriculture, 2021) Moll, Karen Margaret; Chairperson, Graduate Committee: Brent M. Peyton; This is a manuscript style paper that includes co-authored chapters.
Alternatives are needed to avoid future economic and environmental impacts from continued exploration, harvesting transport, and combustion of conventional hydrocarbons resulting in a rise of atmospheric CO 2. Microalgae, including diatoms, are eukaryotic photoautotrophs that can utilize inorganic carbon (e.g., CO 2) as a carbon source and sunlight as an energy source, and many microalgae can store carbon and energy in the form of neutral lipids. In addition to accumulating useful precursors for biofuels and chemical feed-stocks, the use of autotrophic microorganisms can further contribute to reduced CO 2 emissions through utilization of atmospheric CO 2. Most microalgal biofuel research has focused on green algae. However, there are good reasons to consider diatoms for biofuel research. Diatoms are responsible for approximately 40% of marine primary productivity, are important in freshwater systems, and are known to assimilate 20% of global CO 2. Identification and implementation of factors that can contribute to rapid growth will minimize inputs and production costs, thus improving algal biofuel viability. Nine green algae strains that were isolated from Witch Creek, Yellowstone National Park, were compared to two culture collection strains (PC-3 and UTEX395) for growth rates, dry cell weights and lipid accumulation. The strains exhibiting the fastest growth rates were WC-5, WC-1 and WC-2b. The culture collection strain was the best biomass producer and WC-5 and UTEX395 were the most productive for lipid. Based on the growth rates and lipid content, the best strains for biodiesel production were WC-1 and WC-5. In addition to the green algae strains, diatom strain, RGd-1 has previously been found to accumulate 30-40% (w/w) triacylglycerol and 70-80% (w/w) fatty acid methyl esters that can be transesterified into biodiesel. The RGd-1 was sequenced via Illumina 2x50 and PacBio RSII reads and genome comparisons revealed that the RGd-1 genome is significantly divergent from other publicly available genome sequences. RGd-1 was found to have nearly complete metabolic pathways for fatty acid elongation using acetyl-CoA in the mitochondrion or malonyl-CoA in the cytoplasm. The ability to switch between two different starting substrates may confer an advantage for fatty acid and neutral lipid biosynthesis. Further, RGd-1 was found to use the glyoxylate shunt as part of its central carbon metabolism. This carbon conservation pathway may potentially explain why RGd-1 is able to produce high concentrations of lipids. Using Illumina R MiSeq sequencing it was possible to obtain thorough community analysis of bacteria associated with RGd-1 in culture. Nine primary taxa were identified and further research will elucidate their roles as potential phycosphere bacteria that may have specific functional roles that contribute to RGd-1 health. With long-range PacBio reads, RGd-1 was found to have a potential bacterial symbiont, Brevundimonas sp.
Diatom biofuels : optimizing nutrient requirements for growth and lipid accumulation in YNP isolate RGd-1
(Montana State University - Bozeman, College of Letters & Science, 2012) Moll, Karen Margaret; Chairperson, Graduate Committee: Brent M. Peyton
The world's crude oil supply is decreasing at an alarming rate and no longer represents a long-term solution to meet energy needs. Development of renewable energy sources is required to meet transport fuel demands. Algal biofuels represent a potentially viable option. Diatom strain, RGd-1, isolated from Yellowstone National Park, produces high concentrations of lipids that can be used for biodiesel production. To increase cell numbers, RGd-1 was grown in six silica concentrations: without added silica, four silica concentrations within the soluble range (0.5-2mM), and one just above the soluble range (2.5 mM). Increasing the silica concentration resulted in an increase in total cell numbers and dry cell weight (DCW) with R ²=0.965. Silica depletion was verified by inductively coupled plasma mass spectrometry (ICP-MS). When grown in higher silica concentrations the medium reached a higher pH, which remained elevated. Nile Red fluorescence can be used as measurement of triacylglycerol (TAG). Once silica was depleted, Nile Red fluorescence increased. Unlike green algae and other diatoms, nitrate was never depleted when using the standard Bolds Basal Medium concentration (2.94 mM). RGd-1 never depleted nitrate from the growth medium and utilized only 1/3 of the original nitrate concentration (1 mM) by the time cells reached stationary phase. Therefore, the nitrate concentration was decreased to 1mM to induce a dual nitrate and silica stress. To increase the lipid content further, sodium bicarbonate was added to cells grown with each nitrate concentration (2.94 and 1 mM NO ₃-). Coupling nitrate limitation with sodium bicarbonate addition resulted in higher Nile Red fluorescence. RGd-1 fatty acids were primarily observed as C16:0, C16:1, C18:1-3 and C20:5, averaging at approximately 35, 30, 16 and 10%, respectively of the total lipid content. With exception of cells grown without added silica, the percent lipid content was approximately the same (30-40% (w/w) TAG (Triacylglycerol) and 70-80% (w/w) fatty acid methyl ester (FAME) grown under all conditions within the soluble range. However, when factoring in the dry cell weight from each system, it was observed that the TAG and FAME yields increased with silica concentration when normalized to DCW.