Calcium Carbonate Mineralization of Microalgae

Area of Science:

• Biomineralization
• Materials Science
• Environmental Science

Background:

• Biological substrates influence sparingly soluble salt formation, but mechanisms remain unclear.
• Microalgae, like Acutodesmus obliquus (AO), are potential nucleation sites for mineral precipitation.
• Understanding these interactions is crucial for biomimetic materials and environmental applications.

Purpose of the Study:

• To investigate the mechanism of calcium carbonate (CaCO3) growth on Acutodesmus obliquus (AO) microalgae.
• To quantify the effect of microalgae concentration, medium, illumination, and temperature on CaCO3 precipitation.
• To compare CaCO3 precipitation rates on active vs. dried AO and composite substrates.

Main Methods:

• Investigating CaCO3 precipitation on AO microalgae across varying supersaturation levels (SRcalcite).
• Measuring calcite crystal growth rates as a function of AO cell concentration.
• Assessing the impact of microalgae cultivation medium, illumination, and temperature (25 °C and 70 °C) on precipitation.
• Comparing precipitation rates on active AO, air-dried AO, and pre-precipitated calcite on dried AO.

Main Results:

• Acutodesmus obliquus (AO) microalgae promoted calcite growth within a wide supersaturation range (7.94 < SRcalcite < 104.71).
• Calcite precipitation occurred without measurable induction times, with rates increasing with AO concentration.
• Microalgae medium and illumination accelerated CaCO3 precipitation by 75%; air-dried AO showed higher rates than active cultures.
• Precipitation rates on calcite/dried-AO composites were double those on individual components; high temperatures (70 °C) suppressed growth.

Conclusions:

• Acutodesmus obliquus microalgae effectively catalyze calcium carbonate nucleation and growth, particularly in dried forms.
• Environmental factors like medium composition, illumination, and temperature significantly modulate CaCO3 precipitation kinetics on microalgae.
• The findings suggest microalgae can be utilized as efficient bio-templates for controlled calcium carbonate formation.