Alginate from seaweed and microbes: Sources, green extraction, functional properties, and food applications

Abstract Alginate, a renewable polysaccharide produced by brown seaweeds and selected bacterial species, has gained significant attention due to its tunable gelation behavior, biocompatibility, and wide utility in food, biomedical, and packaging applications. This review systematically explores the biological origins of alginate, emphasizing commercially important seaweed genera and emerging microbial producers, while evaluating how species variability, environmental conditions, and extraction parameters influence alginate yield, molecular composition, and techno‐functional attributes. The review provides the first integrated comparison of marine‐ and microbially derived alginates, offering a multidisciplinary assessment of traditional versus green extraction technologies and their impact on structure–function relationships. Alginate's characteristic calcium‐induced gelation supports its effective use in encapsulating probiotics, micronutrients, and polyphenols, as well as in advanced applications such as 3D food printing and bio‐composite development. Despite its versatile functionality, major gaps persist, including the absence of standardized extraction protocols, limited structural benchmarking across biological sources, and inadequate optimization of chemical and physical modification strategies, all of which hinder industrial reproducibility and sustainable scalability. Future perspectives underscore the need for environmentally benign extraction approaches, improved microbial fermentation systems, and targeted alginate engineering to meet emerging technological and regulatory demands, thereby enabling high‐performance, sustainable alginate systems for next‐generation food and nutraceutical applications.