Tuning inorganic carbon and nutrient concentration ratio for biomass, lipid, and protein production from microalgae cultivation

This study investigated how carbon and nutrient inputs influence lipid yield and biomass production in two model freshwater microalgae, Scenedesmus and C. vulgaris . Cultures were cultivated in two mediums (MaxiGro and Cell Hi HP) and a range of inorganic carbon content to obtain protein and FAME for further characterisation. Microalgae biomass production, cell morphology, zeta potential, and biochemical composition were systematically characterised. Results show that nutrient demand decreased with increasing carbon input at the same growth rate. However, excessive carbon or nutrients can negatively impact microalgae morphology and surface charge, eventually leading to Scenedesmus dispersion from the coenobium formation. Lipid and protein production were dependent on the carbon to nutrient ratio. MaxiGro, with threefold higher magnesium content, resulted in higher lipid production, whereas Cell Hi HP, with twofold higher potassium and iron content, led to increasing protein production. These results highlight the importance of tuning the growth conditions, particularly inorganic carbon and nutrient concentrations, to achieve the desired microalgae biomass composition for metabolite production. • Nutrient and carbon concentration impacted on cell growth and lipid/protein content • Increasing carbon input led to a reduction in nutrient demand for the same growth rate • Scenedesmus cells detach from the coenobium formation at high NaHCO 3 concentration • Growth medium has a higher influence on cell surface charge development than carbon • Methyl decanoate synthesis is governed by inorganic carbon availability