Conditions affecting biomass productivity, lipid production, and harvesting of the microalga Monoraphidium sp. Dek19 grown in wastewater
Holbrook, Gabriel P.
M.S. (Master of Science)
Department of Biological Sciences
Microalgae--Control--Illinois--De Kalb; Sewage--Purification--Illinois--De Kalb; Sewage disposal--Illinois--De Kalb; Sewage--Management
The objective of this thesis was to investigate the culture conditions necessary to promote high cell densities, lipid productivities, and harvesting yields from the locally endemic microalgae Monoraphidium sp. Dek19 in a wastewater environment. The alga was inoculated in final effluent acquired from a local wastewater treatment facility in DeKalb, Illinois. The alga was cultivated in 1L Erlenmeyer flasks at 10°C, 70 μmol m⁻² s⁻¹ light, 14:10 light:dark cycle. Culture agitation was found to be an important condition for algal growth and nutrient removal. Increased culture turbulence through aeration correlated with improved phycoremediation and biomass production. Cultures in stagnant conditions failed to achieve high cell densities or desirable nutrient removal. The introduction of periodic aeration at 1L/min for 8 hours per day produced similar biomass productivity and nitrate reduction to the 24 hour per day control. The presence of supplemented carbon sources could be utilized to promote neutral lipid content in microalgae but not biomass growth in Monoraphidium sp. Dek19. Glucose, fructose, analytically pure glycerol, and crude glycerol by-product from biodiesel production were evaluated for their suitability as a substrate for Monoraphidium sp. Dek19. Algal cells stained with BODIPY^(505/515) green fluorescent dye displayed higher lipid content when grown in carbon supplemented wastewater. Biomass production of Monoraphidium sp. Dek19 was inhibited in the presence of these carbon sources as overall cell densities were diminished. Alkaline flocculation was an effective strategy for isolation of the microalgal biomass from its liquid growth medium for harvesting. Monoraphidium sp. Dek19 showed rapid aggregation and subsequent settling when flocculated with KOH after only 20 minutes. This method of harvesting is more favorable in terms of cost and timeframe to filtration, centrifugation, and gravity sedimentation. A modified acid-catalyzed transesterification of the algal lipids produced biodiesel high in desirable saturated and monounsaturated fatty acid methyl esters (FAMEs) and low in undesirable polyunsaturated FAMEs. The biodiesel generated from Monoraphidium sp. Dek19 may be suitable for use in a modern diesel engine. Monoraphidium sp. Dek19 is capable of attaining high biomass and lipid levels when grown in wastewater media. These lipids can be transesterified to produce biodiesel. Additionally, Monoraphidium is able to phycoremediate wastewater by removing nitrate and phosphate from solution to near-zero levels. Monoraphidium is a green microalga acclimated to low light and low temperatures making it suitable for consideration as a biodiesel feedstock in an outdoor wastewater treatment facility.
Hage, Adam Ralph, "Conditions affecting biomass productivity, lipid production, and harvesting of the microalga Monoraphidium sp. Dek19 grown in wastewater" (2016). Graduate Research Theses & Dissertations. 1907.
ix, 113 pages
Northern Illinois University
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Advisors: Gabriel P. Holbrook.||Committee members: W. Scott Grayburn; Wesley Swingley.||Includes bibliographical references.||Includes illustrations.