The world has encountered a food and energy crisis due to accelerated population growth and the depletion of finite fossil fuels. Currently, fossil fuel resources are not regarded as sustainable and their continued consumption is raising severe ecological, economic and environmental questions. Microalgae have recently attracted considerable interest worldwide due to their extensive application potential in the renewable energy, biopharmaceutical, and nutraceutical industries. Actually, microalgae are biorefineries where biomass is converted into a variety of products like biofuels, food and feed supplements, fertilizer, pharmaceuticals, and other products.
Microalgae are ubiquitous, unicellular or simple multicellular, prokaryotic or eukaryotic, photosynthetic microscopic organisms. Even though there are more than 50,000 species exist, only a limited number, of around 30,000, have been studied and analyzed. They may be autotrophic, heterotrophic, or both. Prokaryotes like Cyanobacteria and eukaryotes including Green algae and Diatoms are some examples for microalgae. Dense accumulations of microscopic algal or cyanobacterial cells in water bodies resulting from high nutrient contents are known as algal blooms.
Microalgae are the missing solution to fight climate change mainly occurred due to anthropogenic CO2 and other greenhouse gas emissions. Biological CO2 fixation will be the economical and environmentally viable technology of the future. Compared to terrestrial plants, microalgae have faster growth rates and their CO2 fixation efficiency is also between 10 and 50 times higher. When using microalgae for CO2 mitigation, no additional CO2 is created, while nutrient utilization is achieved in a continuous fashion leading to the production of biofuels and other secondary metabolites. Therefore, it can be coupled with biofuel production and wastewater treatment. Routinely used microalgal and cyanobacterial species for CO2 mitigation are Anabaena sp., Chlamydomonas reinhardtii, Chlorella sp., Scenedesmus sp., Spirulina sp., and Euglena sp.

Microalgae biomass is considered to be a suitable feedstock for biofuel production including biodiesel, butanol, bioethanol, biogas, bio-oil, and jet fuel. Microalgal biofuels overcome a number of the shortcomings of first- and second-generation biofuels, as they produce considerably higher biomass yields (20-30 times) with lower resource inputs than other feedstocks and they are able to grow under conditions unsuitable for crop plants. Bioelectricity also can be generated from microalgae. Algal Fuel Cells are bioelectric devices that use photosynthetic organisms to turn light and biochemical energy into electrical energy.
Microalgae can be used to treat industrial, agricultural and domestic wastewater. They can remove the pollutants simultaneously while utilizing solar energy for their growth and they are able to grow in the arid environment and highly saline water. Cultivation of microalgae in wastewater does not require oxygen supply. Harvested biomass also can be used to produce high-value pigments, fish and animal feed, biofertilizers, and bioplastics. Microalgae can be used in agriculture as biofertilizers, a promising strategy to reduce dependency on agrochemicals, biostimulants, biocontrol agents, soil conditioners, and organic fertilizers.
Microalgae possess high nutritional value. They contain high concentrations of proteins, lipids, polyunsaturated fatty acids, and bioactive carbohydrates such as polysaccharides. Also, they are especially valuable for their high content of essential omega-3 fatty acids. So, they are used as food and feed additives and supplements. Also, they contain antioxidants including pigments such as carotenes, chlorophylls, and phycobiliproteins important for health and cosmetic applications. Spirulina, Chlorella, Dunaliella, and Haematococcus are some microalgae widely used as food supplements, feed, and nutraceuticals. There are microalgal bio-based materials such as microalgal bioplastics and algae carbon fiber.
So, do you still think of microalgae as pond scum? How will you embrace algae in the future?

References:
Khan, M.I., Shin, J.H. & Kim, J.D. The promising future of microalgae: current status, challenges, and optimization of a sustainable and renewable industry for biofuels, feed, and other products. Microb Cell Fact 17, 36 (2018). https://doi.org/10.1186/s12934-018-0879-x

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