Recent Advances in the Valorization of Algae Polysaccharides for Food and Nutraceutical Applications: a Review on the Role of Green Processing Technologies

Recently, there are two main movements gaining public attention: a “green revolution” focused on the use of sustainable processes and the increasing concerns with health-promoting diets and the recognition of the gut microbiota and its effects on the treatment and prevention of several diseases. Microalgae and macroalgae arise as an interesting alternative to obtain these nutraceutical compounds in a sustainable way, due to their extensive list of possible applications (mainly due to their tremendous variation in composition), advantages over terrestrial biomasses and other nutritional sources, and ancestral food consumption history. Nevertheless, available literature has been more focused on the lipidic and protein-rich fraction of microalgae and the texturizing aspects of the carbohydrate-fraction from macroalgae, overlooking their use as prebiotic or nutraceutical ingredients. Furthermore, when these uses are studied, it is with a focus on the action mechanisms of the carbohydrate-rich fractions on gut microbiota and on conventional or, at most, enzyme-assisted ways of obtaining such bioactive fractions. The present review aims at providing an integrated overview of the current knowledge regarding the link between green extraction technologies and the bioactive properties of obtained fractions. In here, the composition of most common algae polysaccharides as well as strategies to increase their relative content in the biomass is discussed. Furthermore, the influence of several environmentally friendly technologies (enzymes, microwaves, ultrasounds, sub and supercritical fluids) and their influence on the polysaccharides’ structure and bioactivity are reviewed. Despite the emphasis on prebiotic potential and carbohydrate valorization, several examples of other bioactive fractions are explored.