As a counter to climate change, energy crises, and global warming, microalgal biomass has gained a lot of interest as a sustainable and environmentally favorable biofuel feedstock. Microalgal carbohydrate is considered one of the promising feedstocks for biofuel produced via the bioconversion route under a biorefinery system. However, the present culture technique, which uses a commercial medium, has poor biomass and carbohydrate productivity, creating a bottleneck for long-term microalgal-carbohydrate-based biofuel generation. This current investigation aims toward the simultaneous increase in biomass and carbohydrate accumulation of Spirulina platensis by formulating an optimal growth condition under different concentrations of nitrogen and phosphorous in flasks and a bubble photobioreactor. For this purpose, the lack of nitrogen (NaNO₃) and phosphorous (K₂HPO₄) in the culture medium resulted in an enhanced Spirulina platensis biomass and total carbohydrate 0.93 ± 0.00 g/L and 74.44% (w/w), respectively. This research is a significant step in defining culture conditions that might be used to tune the carbohydrate content of Spirulina.

Micro-macro algal biomass contains important components such as pigments, carbohydrates, lipids and protein, and these aquatic biomasses are gaining wide attention as an alternative in the production of high added value compounds with specific properties for applications in the food, medical and energy industries according to the concept of biorefineries. These high added value compounds must be extracted from algal biomass using innovative extraction methods. Furthermore, the biorefinery concept requires processes that allow efficient utilization of all components of the biomass. The extraction step in a biorefinery is often based on microwave, or ultrasound. Therefore, in this chapter, a review on the main advances in the extraction processes of compounds from aquatic biomass is presented.