Mixotrophic Cultivation of Dunaliella salina on Crude Glycerol Obtained from Calcinated Fatty Acid Production Process

Enhanced β-carotene and Biomass Production by Induced Mixotrophy in Dunaliella salina across a Combined Strategy of Glycerol, Salinity, and Light

“…In the optimized conditions of this work, chlorophyll a level (4.58 pg. cell −1 ) was lower than the level of 11 pg cell −1 obtained from D. salina cultures with glycerol [20]. However, initial β-carotene levels (4.43 pg.…”

“…The proper growth of D. salina under low doses of glycerol is indicative of the efficient diffusion, active transport, or both of this substrate through the cell membranes. At higher concentrations, the glycerol could have an inhibitory effect on the growth and productivity of D. salina as reported [20]. Even high levels of glycerol may change the chloroplast ultrastructure, which reduces the excitation energy in PSII and decreases the photosynthetic activity and chlorophyll content [31].…”

“…In comparison to the straightforward mixotrophic production of biomass and βcarotene with different organic carbon substrates (glucose, acetate, and glycerol), our optimized cultivation condition with glycerol enhances suitable and productive balance between growth and carotenoids in this halophilic microalga (Table 4). In most initiatives on mixotrophic cultures [12,13,20], only microalgal growth is enhanced, but β-carotene concentration remains low. Unlike our work, most of the reported microalgal cultures with higher growth or pigment levels [10,12,13,20] are due to additional environmental and nutritional conditions that different authors carry out (e.g., higher substrate concentration, inoculum size, and high light intensity, longer cultivation periods, addition of other nutrients, and agitation or aeration systems), which affect microalgal production costs.…”

“…Due to the heterogeneity of both the salinities and glycerol levels, and the cell growth reported from previous studies [14,20,28], the effect of glycerol concentration on the culture of D. salina under better growth isosmotic conditions (1.5 M NaCl) [29] was evaluated. This saline condition and 12.5 mM glycerol promoted the best growth of this microalga (1.19 × 10 6 cells mL −1 ) (p < 0.05), even exceeding cell density obtained in photoautotrophic cultures (IM) (Figure 1).…”

“…Acetate can be toxic in high concentrations for various microorganisms [17] and sometimes is an inadequate substrate for β-carotene synthesis in microalgae [13]. In recent years, the use of glycerol for the mixotrophic production of biomass and carotenoids from microalgae, including D. salina, has been an important initiative by some groups of research [18][19][20][21]. Glycerol can be assimilated properly under respiratory conditions by photosynthetic microorganisms [22].…”