Document Type

Journal Article

Publication Date

2024

Keywords

carbon capture, cabonic anhydrase, CO₂ bio-fixation, CO₂ hydration, microalgae

Abstract

Human activities have significantly increased the global C02 level (>400 ppm) resulting in global warming and extreme climate changes. Microalgae can be used to remove C02 by its high bio-fixation rate. In this study, microalgae bio-fixation at different levels of C02 (i.e., atmospheric condition and flue gas —20%) was conducted in the presence and absence of enzyme; carbonic anhydrase (CA), which was extracted from microbial cells to catalyse the conversion process between dissolved C02 gas and HC03• ion in the growth medium, while microalgae can readily utilize the for their growth and biomass production. Growth of microalgae was measured by OD600nm, medium pH was critically monitored and bio-fixation rate was determined by dry weight of the biomass produced after the cultivation process. Results showed that growth of marine green microalgae; Tetraselmis sp. was double (OD600nm) when adding higher amount of essential nutrient NaN03 (i.e., 0.4 to 0.8 mM). On the other hand, supply of C02 without proper pH control greatly affected the bio-fixation process, since initial acidification of culture medium in the presence of high C02 content (i.e., flue gas) was observed. Furthermore, slow microalgae growth was also observed at elevated pH (> 9) when more C02 was removed from the culture medium. The bio-fixation rates were determined in 2.473 g/L/day and 1.160 g/L/day at 20% C02 with 5 mL CA (3.304 mg mL of total protein) and 0.04% C02 (atmospheric level) without CA, respectively. Optimization study on medium pH, C02 level and amount of CA would be further conducted to enhance the bio-fixation rate for achieving higher C02 removal. In summary, effective C02 removal is demonstrated by a simple microalgae cultivation process assisted with enzyme CA.

Source Publication

4th World Conference on Sustainability, Energy and Environment

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