Combined in-situ immobilization system of Chlorella sp. in photobioreactor

Abstract

This case study presents a pioneering approach for in-situ immobilization of Chlorella sp. microalgae in photobioreactors, achieved through the synergistic combination of immobilization within a polymeric gel and adsorption on a Nylon mesh, termed the CIPGA system. By applying Buckingham's Pi theorem, correlations among governing variables of the CIPGA were established, and a comprehensive full factorial experimental design assessed the significance of light intensity, reactor diameter, and volumetric airflow. Optimal immobilization conditions for Chlorella sp. were determined: light intensity of 71 μmolm−2s−1, photobioreactor diameter of 0.15 m, and aeration air flow rate of 6.7 × 10−6 m3 s−1. A non-linear three-dimensional model utilizing dimensionless parameters was formulated, exhibiting strong accuracy in predicting scaling-up conditions. The CIPGA system demonstrated remarkable efficacy, forming extensive microalgal strands and a biofilm within a complex three-dimensional architecture. Characterization through FTIR spectra analysis revealed significant attributes, including proteins, polysaccharides, and lipid substances. Notably, the presence of exopolysaccharides emerged as a key factor driving microalgal adhesion to hydrophobic surfaces. The versatile applications of this innovative immobilization approach encompass various bioprocesses, including high-value product generation (biohydrogen, biodiesel, photopigments), nutrient and heavy metal ion removal, biosensors, and wastewater treatment processes.

Keywords

• Combined immobilization
• Polymeric gel
• Microalgae
• CIPGA
• Design of experiments
• Dimensionless groups