Microwave-assisted extraction combined with enzymatic pre-treatment for Chlorella vulgaris protein solubilisation.

Abstract Microalgae are considered as a promising industrial source for the sustainable production of valuable compounds, such as high-quality protein, polyunsaturated fatty acids, dietary fibre, pigments, minerals, and vitamins useful in different industries (i.e., nutraceutical, food, animal feed and cosmetics). Cell-wall disruption plays a key role in the recovery of these valuable compounds, so it is necessary to develop specific disruptive processes for each species of microalgae that achieve a more efficient recovery of these compounds. The present work aims to evaluate the combination of different extractive methods on Chlorella vulgaris concentrated liquid biomass in order to enhance and optimise protein solubilisation. Several cell disruption approaches, including mechanical (microwave assisted extraction, MAE) and non-mechanical treatments (enzymatic assisted extraction, EAE) have been investigated. Commercial enzymes including cellulase and a blend of carbohydrases have been applied as algal cells are strong and stable due to the presence of polysaccharides such as cellulose and hemicellulose. Optimisation of independent variables, such as pH (7.3, 9) and extraction time (1–10 min) was performed by Response Surface Methodology conducted through Design Expert software. The cell wall disruption was evaluated by analysis of protein solubilization (Kjeldahl method). It was found that all independent variables had a significant and favourable influence on protein solubilisation. MAE without an EAE pre-treatment step yielded a protein solubilisation about 21–67% dw, whereas adding an enzymatic pre-treatment step using Celluclast® and Viscozyme® yielded a protein solubilisation of 22–68% dw and 43–70% dw, respectively.