EVALUATION OF CARBON DIOXIDE BIO-SEQUESTRATION CAPACITY, BIOMASS PRODUCTIVITY, AND PROXIMATE COMPOSITION OF SELECTED MICROALGAL SPECIES IN TOTAL DISSOLVED CO2 LEVELS

Abstract

Increased atmospheric CO2 from human activities is fueling global warming. Among all the carbon mitigating approaches, microalgae represent a ground breaking solution for lowering carbon dioxide through sequestration, a recognized method for balancing CO2 via photosynthesis. The microalgal strains Gonyostomum sp. and Tetraselmis sp. are examined in this study to assess their capacity to capture CO2. Protein, lipid, and carbohydrates were then produced from a total dissolved CO2 supply that ranges from 55 mgL-1 (control) to 1000 mgL-1 in increments of 200 mgL-1, all while maintaining constant temperatures and light intensities. The current study focuses on not only capturing CO2 but also the utilization of gas through value addition. Maximum carbon fixation rate found at 2.75 ± 0.155 and 2.04 ± 0.13 gL-1day-1 for Tetraselmis sp. and Gonyostomum sp., at 400 mgL-1 dissolved CO2, respectively. It was found that Tetraselmis sp. was affected by CO2 concentration by lowering its productivity from 11.58 ± 0.67 mg L-1day-1 to 2.88 ± 0.54 mg L-1day-1 at 1000 mgL-1 total dissolved CO2. On the other hand, Gonyostomum sp. exhibited significantly higher (p<0.05) carbon content and a constant sequestration rate of up to 1000 mgL-1 of total dissolved carbon dioxide in the cultivation media. Growth parameters, including biomass productivity and specific growth rate, as well as proximate compositions such as protein, lipid, and carbohydrate content, and chlorophyll content, were measured and discussed. Dissolved carbon dioxide in the cultivation conditions affected the biochemical composition of both species. Gonyostomum sp. showed better protein and carbohydrate content at 800 mgL-1, lipid content at 600 mgL-1 dissolved carbon dioxide. The carbon content was higher in 800 mgL-1 for Gonyostomum sp. and for Tetraselmis sp. the higher carbon content was in 600 mgL-1 dissolved carbon dioxide. Although the maximum protein, lipid, and carbohydrate content of Tetraselmis sp. varied according to the cultivation conditions.