The objective of this study was to select a concentration of CO2 absorbents to supplement Spirulina sp. LEB 18 cultivation and to evaluate the effect of these compounds on the growth and production of macromolecules. Three initial biomass concentrations (X-0), eight concentrations of monoethanolamine (MEA), and three NaOH concentrations were tested. The selected MEA concentrations did not inhibit the growth of Spirulina and doubled the dissolved inorganic carbon concentration in the assay medium in relation to the concentration of NaOH. The protein concentration in the biomass grown with MEA was, on average, 17% higher than that obtained with NaOH. Thus, it was found that MEA did not reduce the productivity of Spirulina sp. LEB 18, and its use can be further explored as a means for converting the carbon dissolved in the medium to biomolecules. (C) 2015 Elsevier Ltd. All rights reserved.