Currently, the need to use renewable feedstocks for bioenergetic purposes is an urgent demand due to the depletion of fossil fuels. Microalgae have been utilized as a resilient and a cost-effective source for biofuel production since they can be cultivated using wastewater without the need for fertile soil and are characterized by a fast cell growth rate, and effective CO₂ sequestration. The additional benefit of microalgae includes a high yield of industrially important components such as pigments, lipids, carbohydrates, proteins, and secondary metabolites. The simultaneous production of these components during biofuel production in a biorefinery process makes microalgae a promising feedstock to be more economically feasible. This chapter discusses various cultivation conditions, harvesting, and biofuel production techniques. Furthermore, the cost of biofuel production could be reduced by different upstream processes by selecting the high producing strains as well as downstream processes through enhancing biofuel yields and advanced processes for converting biomass to biofuels. Processes for the production of biodiesel, extraction of lipids, transesterification, hydrothermal liquefaction, and pyrolysis will also be discussed. This chapter also highlights the challenges behind biofuel production based on algal biomass, as well as the future perspectives.

Intracellular hyperaccumulation of phycocyanin (PC) and its high susceptibility to degradation at higher temperatures are major challenging problems associated with its production from cyanobacteria. The present study evaluated different concentrations of organic acids (1, 2, and 3 mM) (citric acid, acetic acid, succinic acid, fumaric acid, and oxalic acid) under fed-batch mode on the biomass and phycobiliproteins’ production from Arthrospira platensis. Besides they were evaluated at 2.5–7.5 mM as preservative to stabilize PC at high temperatures. The incorporation of 3 mM of succinic acid into the cultivation medium enhanced the biomass and PC productivity to 164.05 and 26.70 mg L⁻¹ day⁻¹, which was ~ 2- and threefold higher than control, respectively. The produced PC in this treatment was food-grade with a 2.2 purity ratio. The use of organic acids also enhanced the thermal stability of PC. Citric acid (7.5 mM) markedly promoted the half-life values of PC to 189.44 min compared to 71.84 min in the control. The thermodynamic analysis confirmed higher thermostability of PC in the presence of organic acids and indicated the endothermic and non-spontaneity of the thermal denaturation process. The findings of the present study confirmed that organic acids could be utilized as cost effective and sustainable compounds for promoting not only phycobiliproteins’ production but also the thermostability of PC for potential application in food industry.