자외선 조사에 의해 유도된 Chlorella vulgaris 변이주 특성 및 대량 배양

Abstract

The thoughtlessness use and depletion of fossil fuels have generated major public concerns associated with the global environmental impact and the supply of alternative resources. The microalgae, Chlorella vulgaris can be considered as one of the important alternative resources for biodiesel production due to its relatively simple and fast growth characteristics, high lipid contents, the availability of mass culture technologies, and its non-competing culturable land use for food resources. In this study, we attempted to isolate economically potential high oleaginous strain of C. vulgaris for mass production via the random mutagenesis technique using UV-B irradiation. For efficient UV-B mutagenesis for C. vulgaris, the cells were exposed for various time under UV-B. In general the cell viabilities were significantly decreased as the exposure time increased. We found that four minutes UV exposure was significant enough to achieve 50% lethal effect of UV-B for C. vulgaris. After the UV mutagenesis, the cell cultures were spreaded on F/2 agar plates and further cultured for 21 days under lab conditions. Colonies appeared as relatively bigger in size on the plates were isolated and designated as UBM1-2, UBM1-3, UBM1-10, UBM1-15, and UBM1-18, respectively. After 21 day-cultivation, the resultant mutants were further determined for the cell growth, dry cell weight, pigments contents, and lipid contents based on the considering economically important parameters for biodiesel production under lab conditions. Among the mutants, in particular, UBM1-10 showed approximately 1.5-fold higher final cell Biomass and lipid content respectively than those from the wild type under lab conditions, although other strain such as UBM1-18 showed high potential for chlorphyll (13 mg/g) and cartenoid (3.18 mg/g) productions. Based on the results, UBM1-10 was selected for the mass scale cultivation in a tubular-type photobioreactor (TBPR) or open pond type reactor (OPR) under outdoor conditions. The mass cultivation results indicated that higher cell densities from both parental (1.7 × 109 cells/mL) and UBM1-10 (1.6 × 109 cells/mL) in the TBPR can be achieved rather as those cultured in the OPR type under the industrial conditions. However, UBM1-10 showed similar or a little less cell densities were produced as compared the parental strain cultured under same conditions using both type photoreactors. After the mass cultivation, the cells of UBM1-10 and the parental strain were further investigated for crude lipid contents and compositions. The results indicated that the crude lipid (0.3%) and eicosapentaenoic acid (0%) contents from UBM1-10 was higher than those (0.1%, 0.0261%, respectively) from the parent strain. Therefore, this study demonstrated that the economic potential of C. vulgaris as a biodiesel production resource can be increased with the consideration of photoreactor type as well as the strategic mutant isolation technique using UV-B.