Thermic and techno-functional properties of Arthrospira platensis protein fractions obtained by membrane separation process Anne Luize Lupatini Menegotto 1 & Ilizandra Aparecida Fernandes 1 & Luciane Maria Colla 2 & Jocelei Duarte 3 & Mára Zeni Andrade 3 & Cecilia Abirached 4 & Elton Franceschi 5 & Juliana Steffens 1 & Eunice Valduga 1 Received: 24 March 2020 /Revised and accepted: 27 July 2020 # Springer Nature B.V. 2020 Abstract The high protein content of Arthrospira platensis makes this cyanobacterium a great component of food. Thus, the protein obtained should guarantee the nutrient characteristic, in this case, as bioactivity and techno-functional properties. Membrane separation processes (MSPs) have been highlighted by their capacity to separate proteins and keep their properties. Therefore, MSP was used to concentrate and separate the proteins from A. platensis, which were characterized by their physicochemical and techno-functional properties. Different ultrafiltration (UF) membranes and operational conditions (10- and 50-kDa pore size, conventional and tangential flow, hollow fiber type and pressures of 1.0, 1.5, and 2.0 bar) were tested and associated with diafiltration (DF). The maximized condition of UF/DF (hollow fiber, 50 kDa, tangential flow at 1.5 bar, associated with one DF) was up scaled (pilot scale) and allowed concentrate and permeate fractions with 81.75% and 61.20% of protein, respectively, to be obtained. A protein concentrate with 142 mg L -1 of phycocyanin, 90% of antioxidant activity, with proteins more soluble at high pH (50% soluble protein at pH 7.0) and molecular weight among 5–15 and 100 kDa, was obtained. Protein thermal and emulsifying properties were maintained by the MSP, and the concentrate fraction presented results similar as A. platensis biomass, which confirms the advantage of this method in guaranteeing the protein quality. Keywords Antioxidant activity . Diafiltration . Emulsifying properties . Microalgae potential . Protein secondary structure Introduction Among microalgae composition, their high protein content is highlighted; however, the protein concentration differs be- tween species, culture media, and climate conditions (Godlewska et al. 2017). The cyanobacterium Arthrospira (Spirulina) is one of the richest natural sources of protein, corresponding to 55–77% of its dry weight (dw) (Barka and Blecker 2016). For human consumption, two species tradi- tionally used are Arthrospira platensis and A. maxima, which * Juliana Steffens julisteffens@uricer.edu.br Anne Luize Lupatini Menegotto annelupatini@yahoo.com.br Ilizandra Aparecida Fernandes ilizandrafernandes@yahoo.com.br Luciane Maria Colla lmcolla@upf.br Jocelei Duarte jduarte@ucs.br Mára Zeni Andrade mzandrad@ucs.br Cecilia Abirached abirached@fq.edu.uy Elton Franceschi franceschi.elton@gmail.com Eunice Valduga veunice@uricer.edu.br 1 Department of Food Engineering, URI Erechim, Av. Sete de Setembro 1621, Erechim, RS 99700-000, Brazil 2 Graduate Program in Environmental and Civil Engineering, University of Passo Fundo, Passo Fundo, Rio Grande do Sul, Brazil 3 Exact Sciences and Technology Centre, University of Caxias do Sul (UCS), Caxias do Sul, RS 95070-560, Brazil 4 Food Science and Technology Department, Facultad de Química, Universidad de la República, 11800 Montevideo, Uruguay 5 Center for Research on Colloidal Systems (NUESC), Institute of Research and Technology (ITP), Tiradentes University (UNITI), Aracaju, SE 49032-490, Brazil Journal of Applied Phycology https://doi.org/10.1007/s10811-020-02219-9