Enhancing lipid productivity with novel SiO2-modified polytetrafluoroethylene (PTFE) membranes in a membrane photobioreactor

In this study, silica (SiO2)-modified PTFE membrane was first used to investigate the biomass growth and cellular lipid accumulation of algal cells. SiO2 nanoparticles obtained via a simple sol-gel method were modified on the PTFE membrane to change the water contact angle (WCA) of the membrane surface. The PTFE membrane modified by SiO2 with a WCA of 128.5 degrees resulted in a high biomass yield of 4.29 g/m(2)/day, which was increased by approximately 40% compared with the control. Then, the maximal lipid productivity, 1.97 g/m(2)/day, was obtained at an inlet CO2 concentration of 5% (v/v), a light intensity of 4 mW/cm(2) and a gas flow rate of 40 mL/min. It was increased 0.91-fold than that of the control (1.03 g/m(2)/day). The biodiesel quality of the cellular lipids of algal biofilm was significantly improved. The work demonstrates that the adsorption of algal cells in a gas-liquid separator bioreactor could be enhanced by changing the hydrophobicity of the substrate membrane, resulting in an increase in the biomass and lipid productivities of the microalgal biofilm.