Shifting the natural deep eutectic solvent based liquid lipase extraction from batch to continuous for more efficient process performance

Abstract

Natural deep eutectic solvents (NADES) have been recognised as a promising alternative to conventional aqueous media in biodiesel production because of their dual function, as lipase extractants and transesterification enhancers. To use lipase in NADES, lyophilized lipase must be dissolved in NADES or lipase must be extracted from liquid lipase formulations in NADES. The extraction processes, although efficient, is time consuming because it is highly limited by mass transfer. To enhance the extraction process and shift it from batch to continuous, the aqueous two-phase extraction (ATPS) based on NADES was tested as a possible tool for continuous extraction of lipase from raw liquid formulation to NADES in a microextractor. The fast screening of NADES was performed in a batch extractor and betaine-urea NADES-based was selected for further research. The process was then transferred to a microextractor where the influence of residence time, ultrasound, temperature and channel diameter were studied. Room temperature (T = 25 °C) and 1000 μm channel diameter were optimal for continuous microextraction. The extraction process was significantly intensified in a microextractor. The lipase extraction efficiency obtained in a batch reactor was 94.70% for 30 min, while an extraction efficiency of 98.50% was achieved for a residence time of 30 s in a microextractor. Finally, the extracted lipase was used for biodiesel synthesis in a batch reactor, obtaining a biodiesel yield of 96.11%. The reusability of the extracted lipase was also investigated, and the enzyme was successfully reused in three cycles, after which the biodiesel yield decreased.