# _Arthrospira platensis_ Cultivation in a Bench-Scale Helical Tubular Photobioreactor  
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1 Department of Civil, Chemical and Environmental Engineering, University of Genoa, Via Opera Via 15, 16145 Genoa, Italy; [EMAIL_ADDRESS] (A.A.C.) [EMAIL_ADDRESS] (C.S.) [PERSON]  
2 Biochemical and Pharmaceutical Technology Department, Faculty of Pharmaceutical Sciences, Sio Paulo University, Av. [PERSON], 580, Bl 16, Sao Paulo 05508-900, Brazil; [EMAIL_ADDRESS]  
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3 Northeast Strategic Technologies Center (CETETEN), Cidade Universitaria, Av. [PERSON], 1, 50740-545, Brazil; [EMAIL_ADDRESS]  
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1 Department of Civil, Chemical and Environmental Engineering, University of Genoa, Via Opera Via 15, 16145 Genoa, Italy; [EMAIL_ADDRESS] (A.A.C.) [EMAIL_ADDRESS] (C.S.) [PERSON]  
4 Rede Nordstede de Biotecnologia (RENORBIG), Federal Rural University of Pernambuco (UFRPE), [PERSON], \(s/n\), Dois Irmaos, Recife 52171-900, Brazil; [EMAIL_ADDRESS]  
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5 Escola UNICAP Icam Tech, Universidade Catolica de Pernambuco (UNICAP), Rua do Principe, 526, Boa Vista, Recife 50050-900, Brazil; [EMAIL_ADDRESS]  
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1 Department of Civil, Chemical and Environmental Engineering, University of Genoa, Via Opera Via 15, 16145 Genoa, Italy; [EMAIL_ADDRESS] (A.A.C.) [EMAIL_ADDRESS] (C.S.) fact, fundamental to reduce the cost of valuable products and to broaden the commercial utilization of microalgae [6]. Microalgal cultivation technology has gained widespread attention because microalgae combine the renewable energy-capturing ability of photosynthesis with the high production rates of controlled microbial cultivation, which makes them potentially valuable organisms for cheap industrial production processes [5; 7]. They represent the main natural source of useful and valuable molecules with numerous practical applications, for the majority of which the market is still developing; furthermore, the biotechnological use of microalgae is likely to extend to new areas. As for the application sectors, microalgae are nowadays used from human and animal nutrition [8] to aquaculture [9], pharmaceuticals [10], cosmetics [11], soil fertilization [12], environmental protection [13] including carbon dioxide fixation from industrial waste gases [14], biosorption of heavy metals [15], wastewater treatment [16], and production of biofuels [17]. Currently, the industrial priority is the development of pharmaceutical chemicals and biofuels [18]. Microalgae can, therefore, provide vast contributions on the future welfare of the planet by addressing the pressing issues of human health, food security, renewable energy sources, and global warming. Among the numerous high-quality products from biotechnology of microalgae, the most important regarding production amount and economic value is still the microalgal biomass itself. The worldwide yearly production of microalgal biomass is estimated to achieve 27,500 tons in 2024, with a turnover generation of about 1.1 \(\times\) 10\({}^{9}\) US $ per year [19]. Among the tens of thousands of species that are believed to exist, just a handful are cultivated in industrial quantities (i.e., in tons per year) [20]. Due to their global presence, microalgae are generally used for human and animal nutrition. The commercial applications are restricted to four species, among which is the cyanobacterium _Arthrospira (Spirulina) platensis_, the object of this study. More than 70% of the overall production of _Arthrospira_ sp. biomass is addressed to human nutrition, mainly as a nutraceuticaltial, owing to its high protein content and its excellent nutritional value [21; 22; 23; 24]. In addition, over 50% of the current world production of _Arthrospira_ sp. is used as feed supplement for many types of animals [25]. To grow and exploit the potential of _Arthrospira_ sp., efficient photobioreactors are required [26]. Currently, the commercial production of _A. platensis_ is mainly performed in open systems [27], which are cheap and easy to operate, as they use solar radiation as a free source of energy [4].