Selenastrum gracile

Selenastrum gracile is a species of green microalgae belonging to the family Selenastraceae. It is a microscopic, photosynthetic organism that has gained significant attention in biotechnology for its high growth rates and potential to accumulate valuable biomass under optimized industrial conditions.

Originally found in freshwater ecosystems worldwide, these algae typically inhabit ponds and lakes. Their natural range is broad, reflecting a high level of environmental plasticity. In terms of agronomy, they are classified as an industrial microbial crop, primarily grown in specialized photobioreactors or open-pond systems to maximize production efficiency.

The morphology of Selenastrum gracile is defined by its crescent-shaped cells, which frequently aggregate into colonies. These cells possess efficient photosynthetic apparatus, allowing them to rapidly convert solar energy, inorganic nitrogen, and phosphorus into protein-dense biomass. Reproduction is asexual, predominantly through the formation of autospores within the mother cell.

Climatic and soil requirements for this algae are translated into liquid medium parameters. A temperature range of 20°C to 30°C is generally optimal for growth. Agrotechnical management involves meticulous monitoring of light intensity, pH levels (ideally between 7.5 and 8.2), and nutrient availability. The culture must be kept free of competing invasive species and predators like rotifers, which can decimate a population in a short period.

The economic use of Selenastrum gracile is primarily centered in aquaculture, where it serves as a nutritious feed supplement for larval stages of fish and crustaceans. Furthermore, it is a subject of research for bioremediation, specifically for the removal of nitrogenous waste from agricultural and municipal wastewater, and it is viewed as a future feedstock for high-value lipid extraction.

Essential cultivation factors:

• Light intensity: 100–300 µmol photons m⁻²s⁻¹
• Nutrient medium: Modified Bold's Basal Medium (BBM)
• Aeration: Constant CO2 supply and agitation
• Harvesting methods: Centrifugation or flocculation