ProFA - Valorization of macroalgae biomass as source of proteins and formic acid

Macroalgae are promising feedstocks for the sustainable production of bioplastic films from proteins or platform chemicals such as formic acid (FA) as they are valuable sources of proteins and carbohydrates. This study explores the possibility of using macroalgae as biomass for biogenic FA production using the OxFA process in combination with the extraction of proteins from macroalgae with a focus on resource utilisation and innovation. Herein, the extraction of proteins and the utilisation of the other components of macroalgae to produce FA is linked for the first time. The aim was to find out which macroalgae is best suited to produce FA and protein-rich solids. For this purpose, three different algae were tested: The brown alga Fucus vesiculosus, the green alga Ulva fenestrata and the red alga Porphyra dioica. In addition, the most suitable catalyst for this study was selected from the two polyoxometalates H5PV2Mo10O40 (HPA-2) and H8PV5Mo7O40 (HPA-5) known for their suitability in the OxFA process. After Porphyra dioica proved to be a promising substrate, the parameters temperature (80 °C – 120 °C), reaction time (18 h – 30 h) and catalyst/substrate ratio (0.05 to 0.5) were evaluated for their statistical influence using a Box-Behnken design of experiments. The resulting model was then used to optimise the protein content and FA yield. The optimal conditions were determined to 80 °C, 30 hours and a catalystto-substrate ratio of 0.5 resulting in a protein yield of 59.5 % and a formic acid yield of 16.4 %. For protein extraction from the solid residues, three different methods such as alkaline hydrolysis, ultrasound-assisted extraction (UAE) and ionic liquid extraction (ILE) were investigated. All extraction methods resulted in a protein recovery of more than 40 %dw, with UAE yielding the highest protein recovery of 87.2 %dw (at 100 % sonication amplitude) showing 30 % higher protein recovery than alkaline hydrolysis and 40 % higher protein recovery than ILE. It turned out that the OxFA process followed by protein extraction using UAE gave a high protein recovery and a promising yield of formic acid.