Protein-enriched tobacco-derived composition

A method for obtaining a protein-enriched material from a plant or portion thereof, comprising:

• receiving a plant material biomass;
• contacting the plant material biomass with a solvent comprising a buffer solution for a time and under conditions sufficient to extract one or more proteins from the plant material biomass into the solvent and form a liquid protein-containing extract;
• separating a solid extracted plant material from the liquid protein-containing extract;
• clarifying the liquid protein-containing extract to form a clarified protein-containing extract and a solids fraction, wherein clarifying the liquid protein-containing extract comprises multiple steps including treating the liquid protein-containing extract with at least one centrifugation step, thereafter adjusting the pH of the liquid protein-containing extract within the range of about 4 to about 7, and filtering the pH-adjusted, liquid protein-containing extract;
• and
• separating the clarified protein-containing extract by contacting the clarified protein-containing extract with at least one filter or membrane to give a retentate comprising RuBisCO-enriched protein material and a permeate comprising a second protein-enriched material.