Effect of precipitation, lyophilization, and organic solvent extraction on preparation of protein-rich powders from the microalgae Chlorella protothecoides.

The aim of this study was to investigate the production of protein-rich powders from liberated proteins of the heterotrophically cultivated microalgae Chlorella protothecoides by means of precipitation, lyophilization, and solvent extraction, and assess the characteristics of the obtained materials. First, microalgae dispersions (10 g/100 g) were passed up to 12 times through a high-pressure homogenizer at different pressure levels. Second, the cells were centrifuged (20,000 g , 30 min, 25 °C) to obtain soluble- and insoluble-protein fractions. Lastly, three approaches were used to obtain protein-rich powders from both fractions: (a) solvent precipitation, (b) lyophilization, and (c) solvent extraction. Results showed that cells of Chlorella protothecoides could be disrupted by high pressure homogenization, e.g. 6 passes at 150 MPa led to 99.9% cells being disrupted. For protein precipitation, solvent polarity affected precipitation efficiency in terms of protein and pigment content of the obtained powders. Precipitation with an ethanol:acetone (1:1 v /v) mixture resulted in overall high protein contents in the obtained powders of 46.3 ± 0.1 g/100 g from soluble fractions and 67.2 ± 1.0 g/100 g from insoluble fractions. Solvent extraction of lyophilized powders had only slight effects on protein and pigment content but lyophilized powders itself had a protein content of 39.1 ± 0.5 g/100 g (soluble powder) and 58.5 ± 0.5 g/100 g (insoluble powder). The three applied methods yielded in powders with different characteristics, which might allow use in different food formulations. [ABSTRACT FROM AUTHOR]