Enhancement of the carbohydrate content in Spirulina by applying CO2, thermoelectric fly ashes and reduced nitrogen supply

Abstract

This study focused on evaluating whether the injection of CO₂, which is associated with the use of thermoelectric fly ashes and a reduced supply of nitrogen, affects the production of intracellular carbohydrates from Spirulina. For this purpose, the addition of 0.25 g L^-1 of NaNO₃, along with a 10% (v v^-1) of CO₂ injection, a flow rate of 0.3 vvm for 1 or 5 min, as well as 0, 120 and 160 ppm of fly ashes, was studied. The assays with 120 ppm of fly ashes presented the best kinetic parameters and CO₂ biofixation rate, regardless of the CO₂ injection time. Meanwhile, the experiments with 120 and 160 ppm of fly ash and CO₂ injection for 1 min presented 63.3 and 61.0% (w w^-1) of carbohydrates, respectively. Thus, this study represents an important strategy to increase the accumulation of carbohydrates in Spirulina, with potential application in the production of bioethanol.

Keywords: Carbohydrates; Cyanobacteria; Industrial waste.