Supramolecular structure modification of RuBisCO from alfalfa during removal of chloroplastic materials

Abstract

The use of alfalfa as a dietary protein source is of great interest. Membrane filtration shows potential for removal of unwanted compounds in the purification of ribulose-1,5-biphosphate carboxylase/oxygenase (RuBisCO), but fouling remains a challenge. It was hypothesized that treatments, namely centrifugation, ultracentrifugation, and heat clearing, prior to membrane processing modify the supramolecular assembly of the proteins, facilitating its filtration. The pre-treatments led to different aggregate structures. In particular, heating at 50 °C decreased the aggregate sizes by ∼500 folds relative to the raw juice, as measured by light scattering. The molar mass of RuBisCO decreased by ∼180 kDa after treatment with heat. Similarly, supernatants after ultracentrifugation also showed smaller structures. Unlike the other treatments, heating led to an efficient transmission of RuBisCO during microfiltration. These results demonstrate for the first time, the importance of controlling the supramolecular structure of RuBisCO when processing proteins from alfalfa juice. Industrial relevanceThe demand for more sustainable protein sources is continuously growing. RuBisCO is of particular interest because of its favorable amino acid composition. However, improved purification strategies are needed to extract it from green biomass. The results of this study serve as a proof-of-concept for the application of an industrially relevant process, mild heat treatment in combination with microfiltration, for the purification of RuBisCO from alfalfa green biomass.