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Industrial microalgal characterization and enhancement for a sustainable future
LaPanse, Alaina Joan
LaPanse, Alaina Joan
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2024
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2025-05-26
Abstract
Microalgae are compelling renewable resources because of their rich biomass composition, with applications including biofuels, bioplastics, and nutraceuticals. However, economically viable industrial algal cultivation requires improved biomass productivity, stress tolerance, and product yield. This work addresses the need for better industrial microalgal strains. First, adaptive laboratory evolution (ALE) of Nitzschia inconspicua was utilized to increase high temperature tolerance. Second, biomass characterization and genetic engineering of Picochlorum celeri were deployed to better understand composition and carbon usage.
Nitzschia inconspicua is a diatomic microalga with high relative lipid content, making it a promising platform for sustainable aviation fuel (SAF). ALE was conducted to increase the temperature tolerance of N. inconspicua to 37.5 °C, a lethal temperature to the parent (WT) strain. Clonal isolation of the adapted strain resulted in two unique clones with increased cell size (~20 μm) relative to adapted strain prior to clonal isolation, indicative that a sexual cycle occurred. Preliminary outdoor pond data showed increased productivity of adapted clones compared to WT, enabling more viable SAF production from this strain.
Picochlorum celeri TG2 is a green microalga with rapid growth in high light, high CO2, and seawater. To characterize potential applications, a detailed biomass analysis was conducted. Nutrient-replete P. celeri contained protein-rich biomass. Gradual nitrogen restriction shifted biomass from primarily proteins to carbohydrates as cells transitioned into storage metabolite production. Hyper saline (2X) cultivation resulted in increased levels of the amino acid proline, which putatively acts as an osmolyte. This identification of biomass components yields critical information that informs how this strain might be utilized for renewable product production.
While P. celeri shows high biomass productivity with high CO2 supplementation, growth is slow in air. To understand carbon usage in P. celeri, eight carbonic anhydrases were identified through BLAST investigation and four of these characterized through transformation of fluorescently-tagged carbonic anhydrase constructs. By using confocal imaging, carbonic anhydrases were experimentally localized throughout the cell. Targeted CRISPR/Cas9 knock-out of several carbonic anhydrases revealed unique stationary phase functionalities for these enzymes. This work enables future engineering of more efficient P. celeri carbon usage, facilitating more economically viable algal bioproducts.
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