Effects of Sodium Nitrate and Mixotrophic Culture on Biomass and Lipid Production in Hypersaline Microalgae Dunaliella Viridis Teod

ABSTRACT

To access the potential application of Dunaliella viridis Teod. for biofuel production, the effects of culture media composition on biomass and lipid content of this microalgae were investigated. Measured at the 20 th day, sodium nitrate at 5.0 mM augmented biomass production by 26.5 percent compared to control (1 mM sodium nitrate). Total lipids expressed as µg mL-1 of culture also increased with increase in nitrate concentration up to 5.0 mM sodium nitrate, whereas when expressed on the per cell basis, total lipids stayed relatively constant at most of the tested nitrate concentrations except at 0.5 mM which was 31.4 percent higher compared to 1.0 mM nitrate. At 5.0 mM sodium nitrate, by using 20 g L-1 of glucose in mixotrophic culture of D. viridis, cell number augmented by 36.4 percent compared to the cultures with no added glucose. Llipid content per cell and per mL of culture was increased by 71.4 and 135.1 percent, respectively. Among plant hormones, 10-9 M indole-3- acetic acid (IAA) plus 10 -8 M trans-zeatin riboside led to 22.8 percent higher biomass relative to control (without hormone and at 1.0 mM sodium nitrate). It is concluded that altering the growth conditions of D. viridis can lead to higher cell densities and higher lipids content which can be exploited for biofuel production.