Profiling microalgal protein extraction by microwave burst heating in comparison to spark plasma exposures

Abstract

The efficient extraction of the rich amount of primary and secondary metabolites from microalgae has motivated considerable research. Besides biofuel production, microalgae are especially interesting as source for pharmaceutically and nutritionally valuable compounds. Major obstacle for economic down-streaming processes is the strong and rigid cell wall of microalgae, which impedes efficient compound extraction. Standard extraction methods suffer from several disadvantages and hence, alternative techniques are needed. Especially techniques, which do not modify components and are suitable for thermolabile compounds are required. Microwave burst exposures and submerged spark plasmas have been shown to lead to the release of higher protein yields than other methods. For comparison, Chlorella vulgaris was chosen as model organism because of its particular strong cell wall. Shotgun proteomics revealed comparable results of both methods, though several protein groups of interest showed differences in label-free quantification. Peptide modifications caused by reactive oxygen and nitrogen species (RONS) were observed after spark plasma treatment. However, spark discharges have been found more suitable for the extraction of heat sensitive compounds, such as photosystem-related proteins or histones.