Managing the interactions of illumination, nitrogen, and sodium bicarbonate for autotrophic biomass production and macromolecules accumulation in the microalga Chlorella sorokiniana

Abstract

Understanding how cultivation variables holistically impact microalgal biomass production and macromolecule accumulation is essential toward sustainable scaling-up in open ponds. Efficient, non-wasteful resource utilization is imperative. This study examines the effects of three factors —illumination intensity, nitrogen loading, and inorganic carbon loading (as NaHCO3)—on Chlorella sorokiniana autotrophic cultures. By employing a Taguchi L9 design, these factors were evaluated, while let varying across three levels each. Illumination has the most significant effect on biomass production, while nitrogen loading inversely affected protein and carbohydrate content. No factor appeared significant for lipid accumulation, hinting that carbohydrate biosynthesis might overshadow lipid production. Using the derived statistical model, optimal conditions for maximizing biomass were determined: 7500 lx illumination, 250 mg NaNO3 L−1, and 750 mg NaHCO3 L−1, resulting in a biomass yield of 1105 mg L−1 in 16 days, with a robust R-squared (pred) value of 95.85 %. The obtained insight supports sustainable microalgal biomass production.