Food-industry-effluent-grown microalgal bacterial flocs as a bioresource for high-value phycochemicals and biogas

Microalgal bacterial floc (MaB-floc) raceway ponds are a novel sunlight-based technology to grow biomass on food-industry effluent and flue gas (33.9 kg volatile solids (VS) hapond− 1 d− 1). The MaB-floc biorefinery concept of high-value phycochemicals and biogas was screened to find a suitable valorization strategy for this novel biomass. Freezing and aqueous extraction of MaB-flocs followed by size exclusion chromatography yielded 22.4 g C-phycocyanin (C-PC) kg− 1 VS with a purity of 1.32 (24.5% recovery) and 9.5 g C-phycoerythrin (C-PE) kg− 1 VS with a purity of 1.06 (20.9% recovery). Anaerobic digestion of the extracted MaB-flocs resulted in 272 NL CH4 g− 1 VS. Moreover, increasing the suspended solid (SS) loading of food industry effluent for one day, significantly reduced the biochemical methane yield by 13.6%, and the C-PC and C-PE yield of total crude extracts by 74.5% and 65.5%, respectively. In contrast, it increased the neophytadiene yield by 45.1%. This study highlights the large potential of these MaB-flocs as a bioresource for production of phycobiliproteins, biogas and neophytadiene. Further research is needed to improve the phycochemical extraction and purification processes, and to confirm a huge economic potential.