Comparative Studies of Cell Growth, Total Lipid and Methyl Palmitate of Ankistrodesmus sp. In Phototrophic, Mixotrophic and Heterotrophic Cultures For Biodiesel Production

Abstract

Cultivation mode selection is considered to be an important aspect as this corresponded to the amount of lipid produced by microalgae and to be used for biodiesel production. In this study, phototrophic, mixotrophic and heterotrophic mode were used to cultivate Ankistrodesmus sp. in mon-culture for 17 days. It was found that, mixotrophic Ankistrodesmus sp. shown the highest cells number (9.77 ± 0.59 x 10⁶ cell mL^-1), cell productivity (1.23 ± 0.08 x 10⁶ cell mL^-1 day^-1), specific growth rate (0.43 ± 0.04 day^-1), biomass yield (1.61 ± 0.05 g L^-1), total lipid content (10.55 ± 0.15 % wt), methyl palmitate yield (0.142 ± 0.005 µg mL^-1) and the shortest doubling time (1.63 ± 0.15 day). This was due to effect of glucose as an external carbon source in mixotrophic culture. However, without light Ankistrodesmus sp. grew poorly under heterotrophic mode affected by the lower pH of culture. It was also observed that the mix-cultures of Ankistrodesmus sp. and Chlorella sp. cultivated under mixotrophic mode shown better cell growth of Ankistrodesmus sp. than Chlorella sp. cells. This indicates that, Ankistrodesmus sp. has a higher tolerance towards the culture condition and has better chances of survival in the presence of other microalga species.  Hence, the study shows that cultivating Ankistrodesmus sp. under mixotrophic mode will provide a better cell growth profile, enhance the lipid content and strong endurance.