Evaluation and model-based assessment of environmental factors affecting Desmodesmus abundans productivity

The microalga Desmodesmus abundans holds promise as a feedstock for diverse applications; however, optimizing its cultivation requires understanding key physicochemical parameters. This study investigated the impact of nitrogen availability, pH, inoculum density, harvesting frequency, temperature, and geographical orientation on D. abundans growth and lipid production. Indoor experiments revealed optimal biomass and chlorophyll accumulation at 1.5 g L⁻¹ NaNO₃ and pH 9.5. Harvesting intensity demonstrated a trade‑off: higher rates (50-70%) promoted rapid regrowth but extended recovery periods, whereas moderate harvesting (30%) maximized biomass retention. Thermal tolerance assessment showed cell viability declined sharply at temperatures exceeding 40 °C, indicating greater susceptibility to heat than cold. Outdoor cultivation was conducted in July and December to capture the two extremes of natural light conditions: July represents peak summer with high light irradiance and the highest solar angles of the year, while December corresponds to winter conditions with low light irradiance and the lowest solar angles of the year. South‑facing orientation produced the highest biomass, chlorophyll, and lipid content (32.0% in July), while north orientation yielded the lowest productivity. Partial least squares modeling confirmed that daylight exposure and geographical orientation were primary drivers of growth (R² = 0.881) and lipid content (R² = 0.846), with seasonal variation exerting a strong negative effect on lipid accumulation. These findings provide crucial data for optimizing D. abundans cultivation under controlled and outdoor conditions for sustainable biomass and lipid production.