Growth characteristics and molecular identification of indigenous Limnospira strains from Ethiopian soda lakes as a protein source

Malnutrition poses a significant global challenge in regions such as Ethiopia, particularly in children with limited dietary diversity. Arthrospira, a protein-rich cyanobacterium known for its rapid growth even under extreme conditions, is a promising solution for biomass production. This study addresses knowledge gaps in the morphological characterization and taxonomic classification of Arthrospira by focusing on precise species identification and strategic strain selection for optimal biomass production. Cyanobacterial strains were cultivated in a modified Spirulina Ogawa Terui medium at 35 °C under the photosynthetically active radiation of 160 μmol photons m⁻² s⁻¹ with a 12/12 h light/dark period in laboratory conditions. One hundred Arthrospira-like strains were isolated and characterized based on their morphological attributes according to accepted criteria, from Ethiopian soda lakes. Systematic evaluation of the growth rate comparison test identified four exceptionally fast-growing strains, with LC-30 exhibiting the highest dry weight (3.27 ± 0.51 g L^˗1) and specific growth rate (1.63 ± 0.05 d^˗1) among them. DNA analysis confirmed that all four examined strains belong to the Limnospira genus, specifically identified as Limnospira fusiformis. LC-30 and LA-08 demonstrated protein and phycocyanin levels (582.80 ± 0.07 and 557.90 ± 0.09 mg g^˗1, respectively) comparable to those reported for Arthrospira platensis, and surpassing conventional protein sources, thus suggesting their potential for nutritional supplementation. The study highlights the importance of bioprospecting indigenous strains from soda lakes, revealing promising candidates for large-scale biomass production.