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Wastewater from the potato processing industry called protamylasse is rich in proteins and carbohydrates that potentially can be valorized through cultivation of microalgae by mixotrophic metabolism. However, the complex organic compounds are a challenge, as algae grow best on simple compounds such as volatile fatty acids (VFA). This study demonstrates a new two-stage system. First, VFA production was achieved by testing mesophilic and thermophilic anaerobic acidification (AA) at a short hydraulic retention time (HRT; 3.3 and 5 days) resulting in the release of ammonium and phosphate. HRT of 5 days and thermophilic conditions was optimal considering the high acetate yield of 0.23 g and 22 ml CH4 per g volatile solids (VS). Then, Chlorella sorokiniana was chosen based on the obtained growth rate, and better adaption in ammonium-rich AA effluent after screening several tested microalgae (Chlorella sorokiniana, Chlorella vulgaris, Scenedesmus obliquus, and Haematococcus pluvialis). It was cultivated for valorization of nutrients and organics and successfully upscaled to 25 L photobioreactor (PBR) scale under both batch and continuous operation with high dosage of 25% (8.2 g L−1 of VS) of AA effluent at an HRT of 5 days in the PBR. Chlorella sorokiniana removed more than 99% of the chemical oxygen demand (COD) and the VFA during continuous flow PBR operation. This approach contributed to the final removal efficiency of 71%, 91%, and 78% for phosphorus, nitrate, and ammonia, respectively, and production of microalgae biomass with more than 73% protein. Thus, a promising process for simultaneous treatment of high strength wastewater for microalgal protein production.

Major transitions can be expected within the next few decades aiming at the reduction of pollution and global warming and at energy saving measures. For these purposes, new sustainable biorefinery concepts will be needed that will replace the traditional mineral oil-based synthesis of specialty and bulk chemicals. An important group of these chemicals are those that comprise N-functionalities. Many plant components contained in biomass rest or waste stream fractions contain these N-functionalities in proteins and free amino acids that can be used as starting materials for the synthesis of biopolymers and chemicals. This paper describes the economic and technological feasibility for cyanophycin production by fermentation of the potato waste stream Protamylasse[trade mark sign] or directly in plants and its subsequent conversion to a number of N-containing bulk chemicals.