In situ monitoring of HCO3−, CO32− and NO3− dynamics during microalgae culture by UV resonance raman spectroscopy

Microalgae can convert inorganic carbon (CO₂) and nitrogen (NO_x) into biomass products. However, detection of the concentration of inorganic carbon or nitrogen sources under in-situ culture condition is difficult. In this work, taking Dunaliella salina as a model, the concentration of carbon and nitrogen source in microalgae culture systems are real-time and in-situ detected using UV resonance Raman spectroscopy directly without pretreatment. Due to the resonance Raman effect, the detection limit of inorganic components in the culture medium, HCO₃⁻, CO₃⁻ and NO₃⁻ can reach 10 mM, 2.5 mM, and 0.05 mM respectively. To further indicate the potential of UV Raman spectroscopy, the nitrogen concentration of microalgae culture is monitored using a UV Raman spectrometer at 450 m below the sea. These results demonstrate that the UV resonance Raman spectroscopy is a powerful technique for monitoring the carbon and nitrogen sources for microalgae growth.