Utilisation of tris(hydroxymethyl)aminomethane as a gas carrier in microalgal cultivation to enhance CO2 utilisation and biomass production

Abstract

CO₂ supplementation is usually a limiting factor in microalgal culture systems, especially when flue gases are used as the carbon source. In this study, tris(hydroxymethyl)aminomethane (THAM) was applied as a gas carrier to increase CO₂ storage capacity in the culture medium and enhance microalgal biomass production. Abiotic experiments showed that the amount of CO₂ absorbed by the medium within the same absorption time increased with increasing THAM concentration, and the gas absorptivity maintained a higher level (>60%) under the neutral pH conditions. Cell growth in shaker flasks illustrated that the biomass productivities of Scenedesmus dimorphus were significantly improved (31 to 66%) when the medium contained 2–8 mmol L⁻¹ THAM. Meanwhile, THAM was not biodegraded during the cultivation. The biomass productivities achieved with 6 mmol L⁻¹ THAM were much higher (32 to 33%) than that with routine culture when it was applied into an open raceway reactor system (2 m²), and the CO₂ utilisation efficiency also increased by 6 to 12%. The results show that the addition of THAM as a gas carrier for enhancing CO₂ input could be an easy-to-use and cost-effective approach for mass cultivation of microalgae.