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Marine biorefineries, based on macroalgal (seaweed) feedstocks, could provide sustainable alternative sources of food, energy, and materials. Green macroalgae, with their unique chemical composition, can contribute to marine biorefinery systems associated with a wide range of potential products. This review discusses the challenge of developing industrially relevant and environmentally-friendly green seaweed biorefineries. First, we review potential products from green seaweeds and their co-production, the key element in an integrated biorefinery. Second, we discuss large-scale cultivation, hydrothermal treatments, fermentation, anaerobic digestion, and emerging green solvents, pulsed electric field, microwave, and ultrasound processing technologies. Finally, we analyse the main polysaccharides in green seaweeds: sulfated polysaccharides, starch, and cellulose, as products of a cascading biorefinery, with emphasis on applications and technological challenges. We provide a comprehensive state-of-the-art review of green seaweed as feedstock for the biorefinery, analysing opportunities and challenges in the field.

With decreasing available land and fresh-water resources, the oceans become attractive alternatives for the production of valuable biomass, comparable to terrestrial crops. Seaweed cultivation for food, chemicals, and fuels is already under intensive development, yet efficient technologies for separation of major components are still missing. We report a food-grade process for the extraction of proteins from a green macroalga, Ulva sp., using high-voltage pulsed electric field (PEF) cell-membrane permeabilization, coupled with mechanical pressing to separate liquid and solid phases. We showed that a PEF treatment, at 247 kJ/kg fresh Ulva, delivered through 50 pulses of 50 kV, applied at a 70.3 mm electrode gap on the 140 g fresh weight of Ulva sp., resulted in an ∼7-fold increase in the total protein extraction yield compared to extraction by osmotic shock. The PEF extract of 20% protein content showed 10−20 times higher antioxidant capacity than β-Lactoglobulin (β-Lg), bovine serum albumin, and potato protein isolates. The protein concentration per dry mass in the residual biomass after PEF treatment was increased compared to the control because of the removal of additional nonprotein compounds from the biomass during the extraction process. These results provide currently missing information and technological development for the use of macroalgae as a source of protein for promoting sustainable human nutrition and health.

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