Exploring an in situ LED-illuminated isothermal micro-calorimetric method to investigating the thermodynamic behavior of Chlorella vulgaris during CO 2 bio-fixation

Abstract

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 (Q_T ), maximum power output (P_max) and heat generated by per algae cell (J_N/Q ) were obtained. The values for highest (74.80 g L⁻¹) and control sample (0.00 g L⁻¹) of Q_T , P_max and J_N/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 Q_T , 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 P_max 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.