Holbrook, Gabriel P.
M.S. (Master of Science)
Department of Biological Sciences
Microalgae||Waste products as fuel||Renewable energy sources
The purpose of this thesis was to investigate the growth of the green microalga Monoraphidium sp. Dek19 in the context of phycoremediation under conditions representative of wastewater media of a Midwest wastewater treatment facility. Microalgae were grown in effluent collected from four different wastewater streams at the DeKalb Sanitary District (DSD), DeKalb, Illinois, USA in volumes from 1 L to 380 L. It was determined through preliminary modeling of public data that Monoraphidium sp. Dek19 will likely outcompete local heterospecifics in final effluent wastewaters at the DSD 51.8% of the year. It was also determined that neither nitrogen nor phosphorus should become a limiting nutrient throughout the year. Study of the response of Monoraphidium sp. Dek19 to salinity stress was also completed. Salt stress caused a significant increase in lipid accumulation in salt stressed cultures compared to control cultures (37.0-50.5% increase) with a reduction in biomass productivity. Increases in photosynthetic pigments per cell were seen under salt stress, though the ratio of chlorophyll a and b remained constant. Finally, nitrate uptake was not greatly affected by salinity stress except when biomass accumulation became a corollary for uptake (nitrogen saturation). Luxury uptake of phosphate was significantly affected by wastewater salinity (p<0.001). High sodium potentially interrupts phosphate stress response proteins, slowing internalization of phosphate. Phosphate removal was still possible as some protein binding proteins appear to operate independent of sodium. The effect of indole-3-acetic acid on regulation of cell division in Monoraphidium sp. Dek19 was evaluated at a range of concentrations and no significant differences were observed. A comparison of Monoraphidium sp. Dek19 growth in activated sludge, post-primary filtration, and two final wastewater streams revealed a minimum effect of biotic stressors. The microalgae also grew readily in all wastewaters, though initial population density demands are likely different for each effluent type. Monoraphidium sp. Dek19 grown at large scale revealed light availability as more important than other factors even when compared to large temperature changes (10-25°C). Low-light growth tanks (380 L) showed significantly reduced specific growth rate though microalgae population tripled after three weeks. Dried algal tissue from 380 L tanks was extracted and used to determine neutral lipid accumulation at 6.64+/-0.08%. Fatty acid content was analyzed by GC-FID and found high amounts of unsaturated 18 carbon chains (18:2-18:4), more than previously shown. A comparison of oil from cells growing in 380 L and 1 L cultures showed culturing condition affected fatty acid profile. It was concluded from these data that Monoraphidium sp. Dek19 could be a useful phycoremediation tool of municipal wastewater in the upper Midwest.
Kephart, Anthony Robert, "Use of the green microalga Monoraphidium sp. Dek19 to remediate wastewater : salinity stress and scaling to mesocosm cultures" (2016). Graduate Research Theses & Dissertations. 6583.
ix, 125 pages
Northern Illinois University
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