Even though sunlight energy far outweighs the energy required by human activities, its utilization is a key goal in the field of renewable energies. Microalgae have emerged as a promising new and sustainable feedstock for meeting rising food and feed demand. Because traditional methods of microalgal improvement are likely to have reached their limits, genetic engineering is expected to allow for further increases in the photosynthesis and productivity of microalgae. Understanding the mechanisms that control photosynthesis will enable researchers to identify targets for genetic engineering and, in the end, increase biomass yield, offsetting the costs of cultivation systems and downstream biomass processing. This review describes the molecular events that happen during photosynthesis and microalgal productivity through genetic engineering and discusses future strategies and the limitations of genetic engineering in microalgal productivity. We highlight the major achievements in manipulating the fundamental mechanisms of microalgal photosynthesis and biomass production, as well as promising approaches for making significant contributions to upcoming microalgal-based biotechnology.

With increasing consumer awareness of the use of natural products in pharmaceuticals and medicine, it is noted that algae can be considered an appropriate source. Algae produce many bioactive components, which have application potential in pharmaceutical industries, such as fatty acids, phycobiliprotein, polysaccharides, phenolic compounds, carotenoids, and so on. However, it is still a long way before the truly widespread application of algae in medicine, and some research and technical bottlenecks still need to be resolved for further practical use. Here, we provide an in-depth review of the current understanding of algal-based medical application, with a focus on the main pharmaceutical activity and current application stage includingin vitro, animal, and clinical studies. Furthermore, we propose some possible solutions to the obstacles that should be overcome for achieving the practical applications of algal-based medicine. Notably, animal and clinical studies on algal drugs and treatments should continue to push forward and expand for promoting the practical applications. Moreover, the developments in interdisciplinary research of algal biology and other disciplines provide new insight for driving algae-based medical application.

The phycobilisome (PBS) is the major light-harvesting apparatus in cyanobacteria and red algae. It is a large multi-subunit protein complex of several megadaltons that is found on the stromal side of thylakoid membranes in orderly arrays. Chromophore lyases catalyse the thioether bond between apoproteins and phycobilins of PBSs. Depending on the species, composition, spatial assembly, and, especially, the functional tuning of different phycobiliproteins mediated by linker proteins, PBSs can absorb light between 450 and 650 nm, making them efficient and versatile light-harvesting systems. However, basic research and technological innovations are needed, not only to understand their role in photosynthesis but also to realise the potential applications of PBSs. Crucial components including phycobiliproteins, phycobilins, and lyases together make the PBS an efficient light-harvesting system, and these provide a scheme to explore the heterologous synthesis of PBS. Focusing on these topics, this review describes the essential components needed for PBS assembly, the functional basis of PBS photosynthesis, and the applications of phycobiliproteins. Moreover, key technical challenges for heterologous biosynthesis of phycobiliproteins in chassis cells are discussed.