The commercial potential of Aphanizomenon flos-aquae, a nitrogen-fixing edible cyanobacterium

Abstract

Aphanizomenon flos-aquae (AFA) is a Gram-negative nitrogen-fixing freshwater filamentous cyanobacterium with a rich nutritional profile that is approved for human consumption by both the Food and Drug Administration and the European Food and Safety Authorities. It has a high protein content (60-70%) and contains numerous vitamins, minerals and trace elements together with several high-value compounds with nutraceutical properties, such as C-phycocyanin and β-phenylethylamine. 500-1000 t of AFA dry biomass are currently wild harvested from natural blooms that occur seasonally in Klamath Lake, Oregon, USA, and distributed as a nutritional supplement worldwide. The requirements and unreliability of wild harvesting, owing to the dependence of AFA growth on environmental conditions and potential contamination by microcystin toxins, threaten the availability of biomass supply and restricts commercial expansion. In this review we propose AFA cultivation in open ponds or closed photobioreactors to obtain a reliable production of unialgal biomass to resolve the supply issue and enhance AFA as a feedstock for specific high-value by-products. Furthermore, we explore potential strategies for maximising overall yield and seasonal robustness by using a synergistic combination of cultivation and wild harvesting. Controlled AFA cultivation would also facilitate the use of genetic manipulation to generate bespoke strains with improved commercial applications, such as increasing the cyanobacterium’s nitrogen-fixation rate to enhance its value as a biofertiliser. Ultimately, realising the untapped biotechnological potential of AFA requires a better understanding of its fundamental biology, robust methodologies for laboratory and large-scale cultivation, and the development of AFA-specific genetic engineering techniques.