Exploring an in situ LED-illuminated isothermal micro-calorimetric method to investigating the thermodynamic behavior of Chlorella vulgaris during CO2 bio-fixation.

Much endeavor has been dispensed recently to evaluate the potential of CO2 mitigation by microalgae. We introduce an alternative, novel, LED-illumination isothermal microcalorimetric method to assess the thermodynamic behaviors of microalgae for better understanding of their carbon sequestration capacity. Microalgae thermodynamic behaviors were recorded as power-time curves, and their indices such as total heat evolution (QT), maximum power output (Pmax) and heat generated by per algae cell (JN/Q) were obtained. The values for highest (74.80 g L-1) and control sample (0.00 g L-1) of QT, Pmax and JN/Q were 20.85 and 2.32 J; 252.17 and 57.67 μW; 7.91 × -06 and 8.80 × -07 J cell-1, respectively. According to the values of QT, a general order to promote the CO2 sequestration was found at 74.8 g L-1 > 29.92 g L-1 > 14.96 g L-1 > 7.48 g L-1 > 0 g L-1 of C sources, which directly corresponded to carbon availability in the growth medium. Chlorella vulgaris GIEC-179 showed the highest peak Pmax at 74.8 g L-1 concentration which was directly transformed to their biomass during bio-fixation of CO2 process. This study is applicable for better understanding of CO2 fixation performance of algae.