Contents lists available at ScienceDirect Bioresource Technology journal homepage: www.elsevier.com/locate/biortech Embedding photosynthetic biorefineries with circular economies: Exploring the waste recycling potential of Arthrospira sp. to produce high quality by- products Neha Sachdeva, Cyril Mascolo, Ruddy Wattiez, Baptiste Leroy ⁎ Department of Proteomic and Microbiology, Research Institute for Biosciences, University of Mons, Mons 7000, Belgium GRAPHICAL ABSTRACT ARTICLE INFO Keywords: Biorefinery Circular economy Nitrogen recycle Arthrospira Photobioreactor ABSTRACT This study was conducted with the aim of embedding circular economies (waste recycling) with photosynthetic biorefineries, for production of commercially viable by-products. Since nitrogen source constitute the major input costs for commercial Arthrospira sp. production, the use of nitrogen rich wastewater for Arthrospira sp. cultivation could significantly reduce their production costs. This study evaluated the effects of high con- centrations (8.5–120 mM) of alternative nitrogen sources (urea, ammonium and nitrite) on the biochemical, pigment and proteomic profile of Arthrospira sp., under batch and continuous conditions. Arthrospira sp. cells fed with urea were quantified with modified biochemical and proteomic profile compared to the nitrate fed cells. No inhibitory effect of urea was observed on the biomass even at 120 mM. Nitrite fed cells exhibited comparable biochemical and proteomic profiles as nitrate fed cells. These results clearly indicated at the possibility of using urea rich wastewater streams for profitable cultivation of Arthrospira sp. 1. Introduction The photosynthetic cyanobacteria Arthrospira sp., have played an important role in the evolution of human civilization. From being a major food source for ancient civilizations (Spolaore et al., 2006) to their current roles in synthesis of high-value nutraceuticals/pigments (Zhou et al., 2017; Leema et al., 2010), bioplastics (Zeller et al., 2013), biofuels (Shirazi et al., 2017) and wastewater treatment (Jiang et al., 2015), have truly brought this photosynthetic cyanobacterium at the forefronts of curating environmentally sustainable living for humans. The rise in human population increased the water pollution and depletion of natural resources, making it a necessity to recycle and https://doi.org/10.1016/j.biortech.2018.07.101 Received 15 June 2018; Received in revised form 18 July 2018; Accepted 19 July 2018 ⁎ Corresponding author. E-mail address: baptiste.leroy@umons.ac.be (B. Leroy). Bioresource Technology 268 (2018) 237–246 Available online 21 July 2018 0960-8524/ © 2018 Elsevier Ltd. All rights reserved. T