Rapid photocatalytic disruption of Chlorella vulgaris cells for extraction of triacylgricides using Ag3PO4–TiO2 nanocomposite

Abstract

Freshwater green microalgae are a source of valuable industrial products. Owing to the lipid accumulating nature of these organisms, it is among the most promising solutions to meet carbon neutral hydrocarbon fuel needs for future transportation. However, there are many technical hurdles that need to be overcome before their commercial viability. One of the challenges is getting cellular lipids out from the cell because of the sturdy algal cell wall. Several chemical, physical, thermal, and biological techniques have been tested and reported so far, but all the methods are either energy intensive, not scalable, product damaging, slow or less effective. Photocatalysis is a promising field with emerging green solutions to many environmental problems and has only scarcely been studied so far for algal cell disruption. In this study Ag3PO4–TiO2 photocatalyst was used for pre-treatment of Chlorella vulgaris (UTEX-26) cells in the presence of UV and visible light. Results showed an increase of ∼8% in lipid quantity compared to raw cells with 5 and 30 min of UV and visible light pre-treatment, respectively at a catalyst dose of 500 mg L−1 at pH 3. The Attenuated Total Reflection - Infra Red (ATR-IR) analysis of bio-oil revealed that no significant change in lipid quality occurred due to photocatalytic pre-treatment. The pre-treatment experiments also resulted in simultaneous harvesting of the cells, thus further reducing the energy needs of the process. The technique for algal cell wall disruption using Ag3PO4–Titania composites for lipid yield enhancement has not been reported to date.