# Microalgal Proteins and Bioactives for Food, Feed, and Other Applications
## 1 Introduction  
According to the United Nations, the world population will be 9.7 billion people by 2050, and to meet its needs, the amount of food produced must be doubled [1]. Nowadays, more than 3.5 million deaths are caused by maternal and child malnutrition annually. According to the World Health Organization (WHO), around 45% of child mortalities are caused by malnutrition, and over one billion people have inadequate protein intake [2]. For these reasons, there is a need to find new, nutrient-rich protein sources [3]. Microalgae are a diverse group of microorganisms known as phytoplankton and their classification is under constant revision due to new genetic evidence [4]. Nevertheless, the majority of microalgae are unicellular, photosynthetic microorganisms producing oxygen and assimilating carbon dioxide by obtaining macro- and micronutrients from aquatic environments. The term'microalgae' applies to both eukaryotic microalgae and prokaryotic cyanobacteria [5] and they play an important role in the marine food chain as the primary source of omega-3 fatty acids [6]. Microalgae can survive in wastewater, ocean water and brine water; they have a high growth rate and productivity, they do not compete with agricultural land and they have high CO\({}_{2}\)-fixing efficiency [7, 8]. Although the number of microalgae species was estimated to be 200,000 (according to AlgaeBase, current number of known species is about 160,000, www.algaebase.org (accessed on 11 December 2021), only 30,000 species are studied currently. A few microalgae species are known to have been consumed since ancient times--these include _Arthospira platensis_ (Lake Chad) [9], _Arthospira maxima_ (Lake Texcoco) [10], _Nostoc commune_ (China) [11], _Nostoc flagelliforme_ (China) [12] and _Aphanothece_sacrum_ (Japan) [13]. The first large-scale production of _Chlorella vulgaris_ started at Massachusetts Institute of Technology in 1951 [14], followed by the production of _Arthospira_ sp. initiated in 1973 by Sosa-Texocco Ltd. in Mexico [15]. Microalgae species currently cultivated in large volumes include _Arthrospira_ spp. (world annual production 5000 tons of DW), _Chlorella_ spp. (world annual production 2000 tons of DW), _Nannochloropsis_ spp. and _Haematococcus pluvialis_[16; 17]. Asia and Australia produce the largest volumes of microalgae for the food and feed sectors, and production by European companies is currently estimated at around 5% of the global market [16]. According to [PERSON] and colleagues, annual microalgae production in Europe is estimated at 182 tons of microalga dry mass produced by 167 companies and 142 tons of dry mass _Arthrospira_ spp. produced by 222 companies. The largest producers of microalgae in Europe are Germany, France, Italy, Spain and Portugal. In the last decade, an increase of 150% in growth was observed for the number of new algae producing companies in existence [17]. However, several factors limit the potential of the European microalgae market, including insufficient domestic demand for microalgae-based products and difficulties in achieving the commercial authorization of microalgae production in the EU. The market value of microalgae biomass depends on the production system and production costs, place of origin, certifications (e.g., organic production) and step in the value chain (Business to Business (B2B) or Business to consumer (B2C) segment). The business to consumer (B2C) value for some microalgae such as _Chlorella_ sp. and _Spirulina_ spp. was estimated at 150 and 280 EUR/kg of DW, respectively, and for _Nannochloropsis_ sp. (the most relevant species for feed) the B2C market value can go to 1000 EUR/kg microalgae DW [17]. Microalgae are often produced and used in feeds and foods due to their high lipid content; however, they are also a rich source of sustainable protein that may be suitable for human and animal consumption.