이산화탄소 포집 및 활용을 위한 Dunaliella와 탄산무수화효소의 분자생리학적 연구

Abstract

As the amount of CO2 in the atmosphere has been increased, many technologies for carbon capture and utilization (CCU) have been proposed. Conventional methods such as chemical and geological conversion of CO2 have problems of additional energy input and expensive operating costs, thus there is a requirement of biological and bio-inspired CCU. In addition, technologies developed till date for CCU have a disadvantage that it can be utilized only at the region of near the point source. Because of this reason, development of CCU technology at non-point source region using biological system is potentially required. This dissertation describes the studies of biological and bio-inspired CCU using microalgal Dunaliella system and its carbonic anhydrase (CA) gene. In biological CCU at point source, Dunaliella sp. was cultivated in various concentration of CO2 to optimize its culture condition and showed that it has highest productivity of biomass (521 mg L-1 d-1) and total lipid (40 mg L-1 d-1) at 5% CO2 aeration during the logarithmic growth phase. Further study concentrates on carbonic anhydrase which is a carbon concentrating enzyme used to develop the CCU technology in the area of CO2 fixation at non-point sources. Bio-catalytic conversion system was developed using microalgal CA and phosphoenolpyruvate carboxylase (PEPCase), and showed enhanced production of oxaloacetate. Therefore, the CA-PEPCase system can be used not only to capture CO2 but also to produce value-added C4 platform chemicals as a new technology. In addition, magnetically-separable enzyme precipitate coating (Mag-EPC) was directly added to Dunaliella culture. The addition of Mag-EPC accelerated the growth of Dunaliella. Furthermore, to enhance in vitro/in vivo availability of CA, Dunaliella salina CA genes (DsCAs) were identified and characterized. This result showed that D. salina has five alpha-type CAs and three gamma-type CAs. A hypothesized localization map of DsCAs in D. salina was proposed using several in silico analysis programs. The activity of truncated recombinant DsCA1 was induced by salt. Finally, to enhance the capacity of microalgal system based CCU, genetic engineering system of Dunaliella was successfully developed by using antisense RNA of carotenoid biosynthesis related gene (CBR). Results of this dissertation provide the biological feasibility of Dunaliella in biological CCU in the area of point sources of CO2. This study also suggest potential biochemical usefulness of microalgal CA in bio-inspired CCU in the area of non-point sources of CO2.