A novel photoelectrochemical system to disrupt microalgae for maximizing lipid-extraction efficiency

[Display omitted] •A novel PhotoElectroChemical (PEC) system disrupts Chlorella to increase lipid extraction.•N-doped TiO2-coated photoanode captures UV–Vis light and generates electrons e-.•A palladium-phosphorus cathode receives the electrons and generates hydroxyl radicals (•OH).•The •OH attacks microalgal cell walls and membranes to enhance lipid extraction and quality.•The PEC system enables eco-friendly and low-energy disruption of microalgal cells. Microalgae biodiesel is a candidate to provide renewable, C-neutral energy. However, microalgal cells possess strong cell walls and cell membranes with high selective permeability, both of which hinder the extraction of lipids from the microalgae. Optimizing lipid extraction involves disrupting the microalgae’s cell wall and membrane. The hydroxyl free radical (•OH) can attack the cell wall and cell membrane in the microalgae, making the microalgae more susceptible to lipid extraction. Introduced here is a PhotoElectroChemical (PEC) with TiO2-based photoanode utilized UV–Vis light to produce •OH at a phosphate-palladium cathode. Until now, PEC has not been utilized to disrupt microalgal cells to improve the extraction of microalgae lipids. Here, a novel PEC system -- comprised of two nitrogen-doped TiO2 nanotube photoanodes, a bipolar membrane, and a phosphorus-palladium cathode -- was demonstrated to disrupt microalgal biomass to improve lipid extraction. PEC utilizes ultraviolet and visible light as the only input energy for the effective disruption of the microalgal cell. Pretreatment of Chlorella using the PEC system resulted in 96% oil-extraction efficiency which was approximately 10 times higher than that achieved without the pretreatment and an increases in desirable C16:0. Also explored were the mechanisms underlying •OH generation and microalgae disruption. PEC promises to be an eco-friendly and low-energy technology that can promote the development of microalgae industries.