Optimization CO2 utilization for biomass and favorable physiological factors for production of value added products

Abstract

As increasing concentration of CO2 (greenhouse gas) impacting differentially on environment as changing the temperature and with respect to growth rate, biomass, photosynthetic carbon fixation and subsist of biological systems. Huge availability and biological CO2 mitigation using microalgae is of the current interest for utility optimization with green photosynthetic energy fixers to achieve high biomass and productivity of value added products. The present study focused on effect of carbon dioxide (CO2) on growth rate, biomass, chlorophyll concentration, oxygen evolution rate, and lipid production in Dunaliella sp. Various CO2 concentration from 0.03-12% studied to determine effect and their productivity in Dunaliella sp. The cell growth on different CO2 air bubbling conditions displayed different growth pattern. The highest growth culture condition was 5% CO2 air bubbling. The maximum number of cells was 2.5 x 107 cells/ml. This is the 25 times higher than initial number of cells (1.0 x 106 cells/ml). The maximum concentration of lipid was 310mg/ml at 9th day. The maximum productivity of lipid was 57.5mg per day at 10% CO2 air bubbling condition. And the samples at 5% CO2 condition had the highest chlorophyll concentration (13.14 x 10-9mol/ml), and chlorophyll per cell was highest at 12% CO2 condition (2.24 x 10-15mol/cell). The Chlorophyll a/b ratio at 5% and 10% CO2 condition was lower than others. Oxygen evolution rate was also measured by increasing light intensity at 3 rd. and 6 th. day after inoculation to determine efficiency of photosynthetic rate. The highest oxygen evolution rate was 149 mmol O2(mol Chl)-1s-1 at 10% CO2 condition. The expression of several photosynthetic genes from different culture condition was also analyzed by Northern blot.