MINIMIZING OPTIMAL CO2 FEED TO ALGAL CULTURES UTLIZING MICROFLUIDIC DEVICES GENERATING MICRON-SIZED BUBBLES

microalgae;KLa;mass transfer;microfluidics;bubbles;biofuels;sustainability;Chemical & Biomolecular Engineering

Baker, Jordan J.Betenbaugh, Michael J. ;

Johns Hopkins University

关键词: microalgae;    KLa;    mass transfer;    microfluidics;    bubbles;    biofuels;    sustainability;    Chemical & Biomolecular Engineering;   

Others  :  https://jscholarship.library.jhu.edu/bitstream/handle/1774.2/39256/BAKER-THESIS-2015.pdf?sequence=1&isAllowed=y

瑞士|英语

来源: JOHNS HOPKINS DSpace Repository

【 摘 要 】

With amplified environmental damage caused by increased carbon dioxide levels in the atmosphere and the rising cost of energy, algae offer solutions to both world issues as well as many others. Microalgae naturally produce lipids (biofuels), carotenoids (antioxidant health supplements/nutraceuticals), proteins (pharmaceuticals), as well as many other products while removing carbon dioxide from the atmosphere through photosynthesis. The optimal carbon dioxide feed conditions were tested in a microalgae strain, Chlorella vulgaris, to fix the largest amount of carbon dioxide, provide the fastest growth, and produce the greatest concentration of desired components. Feeding 10% carbon dioxide led to the highest growth rate and had the greatest productivity of biomass, total protein, lipids, and lutein (carotenoid) in terms of time, volume of reactor, and cost. In addition to finding the optimal carbon dioxide feed concentrations, a microfluidic device (channels <70 µm) was utilized to create micro-scale bubbles to significantly increase mass transfer at low flow rates. The convergence of one gas and two liquid channels at a Y-junction generated bubbles via cyclic changes in pressure. At low flow rates, the bubbles had an average diameter of 114 µm, corresponding to a volumetric mass transfer rate (KLa) of 1.43 hr-1. Normalized KLa values demonstrated that the microbubbler had a 100-fold increase in mass transfer per flow rate compared to four other commonly used bubblers. The calculated percentage of oxygen transferred was 90%, which was consistent with a separate off-gas analysis. The improved mass transfer was also tested in an algae bioreactor in which the microbubbler culture absorbed approximately 90% of the CO2 feed compared to 2% in the culture with an alternative needle bubbling method. The microbubbler yielded a cell density only 82% of the cell density for the needle tip, but with an 800 fold lower flow rate (0.5mL/min versus 400 mL/min) and a 700 fold higher ratio of biomass to fed gas. The application of the microfluidics may transform interfacial processing in order to increase efficiencies, minimize gas feeding, and provide for more sustainable multiphase processes.Finding the ideal carbon dioxide feed of 10% CO2 to vulgaris cultures allows for fast, efficient production of biofuels, nutraceuticals, pharmaceuticals, and many other products while helping the environment by fixing carbon dioxide. Through an exceptional improvement in mass transfer from a gas to a liquid, the microfluidic bubbler improved the carbon dioxide fixation and growth rate for microalgae, decreasing costs for bioreactors. This microbubbler can also be used to improve gas sequestration, bioreactors, chemical reactions, and many other industrial processes.