Microalgal pigments potential as byproducts in lipid production

As an alternative biomass for producing biofuel, microalgae have many advantages over land biomass. For example, they are not a food source, they are fast-growing and have a high oil content, and they can reduce CO2. However, the high costs of cultivation and harvesting using existing technology make microalgal-based biofuels uncompetitive with fossil fuels. This study investigates the feasibility of producing high-value microalgal pigments, including chlorophyll and carotenoid for apportioning the high cost of cultivation and harvest. Five microalgae were tested to determine their pigment and lipid production in a feed-batch bioreactor under light conditions of 167 μmol photon/(m2 s) for 12 h daily. Among them, Dunaliella primolecta and Isochrysis aff. galbana achieved the highest chlorophyll yields of 5.3% and 5.6%, respectively, with the optimal carotenoid yields of 2.6% and 2.0%, and lipids yields of 23% and 24%, respectively. The feasibility of simultaneously extracting both lipids and pigments was investigated. Two solvents, methanol and hexane, were used in the extraction of pigments and lipids. The extraction yields of pigments and lipids using methanol and hexane reached 98% and 90%, respectively. Therefore, we expect that the simultaneous production and extraction of high-value pigments accompanied by the lipids can potentially offset the high cultivation and harvesting costs, and may make microalgal biomass economically competitive for biofuel production.