Digestibility, bioaccessibility and bioactivity of compounds from algae

Algae are aquatic organisms rich in several biocompounds, and major ones are proteins and amino acids, carbohydrates and polysaccharides, lipids and fatty acids, pigments like chlorophyll, carotenoid, and phycocyanin, vitamins, minerals, and polyphenols that exhibit multiple beneficial effects on human health. These compounds are present in high concentrations in raw algal biomass, but some of them may not be available to exert their biological function in the human body, due to the inherent composition of algae cell wall. This review provides an overview of existing information of ongoing studies on the digestibility and bioavailability of algae derived compounds, while giving a glimpse of the studies that examine in vivo digestibility and bioaccessibility of microalgal biomass as feed supplementation for animals. Special attention is also given to the influence of cell wall disruption techniques on the bioaccessibility of algal bioactive compounds, showcasing carefully the in vitro bioaccessible nutrients of foods enriched with algal biomass. Digestibility and bioaccessibility of major compounds varied greatly between algal species. Polysaccharides and fibers are undigestible by humans, binding carbohydrates assimilation. Combined disruption methods like bead milling or high pressure homogenization with enzymatic pretreatment, using cellulases prior to algal compound extraction, may help to increase the extractability and bioavailability of lipid and fatty acids, pigments and minerals, as well as enhancing even further protein and amino acid absorptions. Studies on in vivo dietary supplementation of algae in animals (sheep, chicken, mice, and fishes) showed good acceptability and digestibility of proteins and lipids. Traditional foods such as cookies, snack, bread, and yogurt enriched with maximum 5% of algal biomass allowed to carry on natural bioactive compounds of algae, extending the bioaccessibility and enlightening the positive impact of consuming algae-based food for human health promotion.