Microalgae proteins: production, separation, isolation, quantification, and application in food and feed.

Many countries have been experienced an increase in protein consumption due to the population growth and adoption of protein-rich dietaries. Unfortunately, conventional-based protein agroindustry is associated with environmental impacts that might aggravate as the humankind increase. Thus, it is important to screen for novel protein sources that are environmentally friendly. Microalgae farming is a promising alternative to couple the anthropic emissions with the production of food and feed. Some microalgae show protein contents two times higher than conventional protein sources. The use of whole microalgae biomass as a protein source in food and feed is simple and well-established. Conversely, the production of microalgae protein supplements and isolates requires the development of feasible and robust processes able to fractionate the microalgae biomass in different value-added products. Since most of the proteins are inside the microalgae cells, several techniques of disruption have been proposed to increase the efficiency to extract them. After the disruption of the microalgae cells, the proteins can be extracted, concentrated, isolated or purified allowing the development of different products. This critical review addresses the current state of the production of microalgae proteins for multifarious applications, and possibilities to concatenate the production of proteins and advanced biofuels.

Extraction of proteins from the microalga Scenedesmus obliquus BR003 followed by lipid extraction of the wet deproteinized biomass using hexane and ethyl acetate.

A current problem of the lipid extraction from wet biomass is the formation of emulsions during the mixing of the microalgal biomass and organic solvents. It has been suggested that microalgal proteins play an important role in the formation and stability of such emulsions. Herein, the extraction of proteins of the freshwater microalga Scenedesmus obliquus BR003 was optimized for further extraction of lipids from the wet deproteinized biomass. The optimal (pH 12 at 60 °C for 3 h) and moderate (pH 10.5 at 50 °C for 2 h) conditions of protein extraction resulted in protein yields of 20.6% and 15.4%, respectively. Wet lipid extraction of deproteinized biomass resulted in a less stable emulsion that released twice the solvent than the control biomass. However, the faster separation of phases that occurred during the wet lipid extraction of the deproteinized biomass resulted in a lipid yield twice lower than the control biomass.