Harnessing enzyme and microbial biotechnology for macroalgae valorization: A circular economy approach with...

Macroalgae are a sustainable, non-terrestrial biomass resource critical for the emerging blue economy. They play a crucial role in marine ecosystems, including the natural sequestration of carbon, which grounds the entire value chain in sustainable CO₂ removal. This review presents how enzyme and microbial biotechnology drive the techno-economic feasibility of macroalgal processing within a circular biorefinery framework. We detail how tailored enzymatic cocktails enable the selective, mild-condition extraction and modification of high-value, mainstream products, such as hydrocolloids and nutraceuticals like omega-3 lipids, from the three major macroalgal groups. Concurrently, microbial bioconversion is crucial for transforming macroalgal components, including polysaccharides, proteins, and lipids, into byproducts such as biofuels and biofertilizers, thereby ensuring resource efficiency and minimizing waste. The application of molecular omics technologies (genomics, transcriptomics, proteomics, and metabolomics) is shown to underpin the macroalgal biology and optimize bioprocesses by identifying novel microbial strains, enzymes and engineering metabolic pathways of microbial strains to enhance yields and specificity. The study addresses technological, economic, and environmental difficulties. This integrated, cascading approach is necessary to transition macroalgae valorization from single-product extraction to a profitable, multi-product industry, balancing economic growth with environmental preservation. Critical assessment of the framework's overall environmental viability relies on life cycle analysis (LCA). This review contributes an essential methodological synthesis to guide future studies, ensuring consistent sustainability assessment of the macroalgal biorefinery.