Towards plant protein refinery: Review on protein extraction using alkali and potential enzymatic assistance

The globally increasing protein demands require additional resources to those currently available. Furthermore, the optimal usage of protein fractions from both traditional and new protein resources, such as algae and leaves, is essential. Here, we present an overview on alkaline plant protein extraction including the potentials of enzyme addition in the form of proteases and/or carbohydrolases. Strategic biomass selection, combined with the appropriate process conditions can increase protein yields after extraction. Enzyme addition, especially of proteases, can be useful when alkaline protein extraction yields are low. These additions can also be used to enable processing at a pH closer to 7 to avoid the otherwise severe conditions that denature proteins. Finally, a protein biorefinery concept is presented that aims to upcycle residual biomass by separating essential amino acids to be used for food and feed, and non-essential amino acids for production of bulk chemicals.