Prebiotic and Functional Fibers from Micro- and Macroalgae: Gut Microbiota Modulation, Health Benefits, and Food Applications.

Micro- and macro-algae are natural resources that attract attention in terms of their prebiotic potential and functional food applications due to their rich polysaccharide diversity. In this review, the regulatory effects of dietary fibers and polysaccharides from algae on gut microbiota, their health benefits and their potential functions in foods are discussed in detail. Compounds such as fucoidan, laminarin, alginate, porphyran, agar, carrageenan and exopolysaccharides are examined for their interactions with the microbiota and how they support digestive health, immunity and metabolic balance through the production of short chain fatty acids. In contrast to earlier reviews, this paper offers a comprehensive comparison between sulfated and non-sulfated algal polysaccharides, incorporates updated insights on their regulatory status and safety, and highlights emerging direction for developing next-generation prebiotic formulation. The review also examines their applications in functional foods, nutraceutical effects and protective roles, and includes preclinical and clinical studies. However, some limitations such as safety of consumption, risk of heavy metal accumulation, bioavailability issues and regulatory restrictions are also addressed. New nutritional approaches, next generation prebiotic formulations and biotechnological studies are included. This review aims to comprehensively highlight the versatile potential of algal polysaccharides as functional fibers and prebiotics. While numerous studies have examined algal polysaccharides, their heterogeneous structures and safety. This review emphasized these critical gaps and proposed a rational evaluation framework for future research and functional food development.