Enhancement of dissolved inorganic carbon and carbon fixation by green alga Scenedesmus sp. in the presence of alkanolamine CO2 absorbents

The influence of alkanolamine CO2 absorbents on the CO2 fixation in photoautotrophic culture of green alga Scenedesmus sp. was investigated using monoethanolamine (MEA), 2-amino-2-methyl-1-propanol (AMP), diethanolamine (DEA) and triethanolamine (TEA). The dissolved inorganic carbon (DIC) contents increased when alkanolamine compounds existed in the medium. Utilizing the increased DIC for algal uptake, TEA exhibited a best enhancement in CO2 fixation performance compared to other absorbents, while primary ethanolamines displayed inhibition on cell growth due to the formation of relatively stable carbamate intermediate. By adding 5 mM TEA, the cell growth and CO2 fixation rate increased by 30.5% compared to the case with no TEA. TEA was supplemented when cell density was doubled, tripled and quadrupled to maintain the TEA to cells ratio constant pacing the increase of cell density. The repeated addition of TEA exhibited the enhancement of CO2 fixation rate by 39.3% and 18.5% from no-addition and one-time addition cases, respectively.

► The influence of various CO2 absorbents was compared on microalgal CO2 fixation.
► Microalgal growth rate were best enhanced by triethanolamine (TEA) among tested CO2 absorbents.
► The repeated addition of TEA enhanced CO2 fixation rate by 39.3% from no-addition case.