Extracting Water-Soluble Proteins from the Red Macroalgae Gracilaria sp. with Pulsed Electric Field in a Continuous Process

Marine macroalgae are an emerging sustainable source of protein; however, protein extraction from macroalgae is challenging. In this work we report a novel, screw-press-based device for continuous high-voltage pulsed-electric-field (PEF) processing of fresh biomass to extract water-soluble protein from the red seaweed Gracilaria sp. The water extracts from the PEF-treated biomass showed higher protein yield (37.82 ± 7.96 to 47.56 ± 10.54 mg/g initial dry weight (DW) of biomass, depending on PEF conditions) compared to extracts without PEF (33.82 ± 6.01 mg/g initial DW of biomass). PEF followed by aqueous extraction removed 69.11% of the ash from the Gracilaria sp. biomass. The in vitro digestibility of the proteins in the water-soluble extract from the PEF process was 70% compared to that of casein, but it was only 25% for the juice protein extracted with a screw press alone. The energy consumption for PEF was 2.94 ± 0.91 kJ/(kg fresh weight (FW)) - 4.06 ± 0.48 kJ/kgFW, depending on the applied voltage. This study is the first report of processing Gracilaria sp. biomass using a continuous PEF system and successfully demonstrates the protein extraction with relatively lower energy inputs.