Method of preparing plant-derived proteins

A method of preparing plant derived antibodies, the method comprising:

• a. obtaining a Nicotiana benthamiana plant or plant matter comprising apoplast-localized antibodies, wherein a nucleic acid comprising a nucleotide sequence encoding the antibodies has been introduced into the Nicotiana benthamiana plant in a transient manner, and wherein the Nicotiana benthamiana plant matter consists of plant leaves, leaf pieces, shredded leaves, or a combination thereof;
• b. producing a digested fraction, wherein the digested fraction comprises an apoplast fraction, a protoplast fraction and plant debris, by extraction from the plant or plant matter, wherein the extraction consists of an enzymatic extraction, with a cell wall degrading enzyme mixture, wherein the cell wall degrading enzyme mixture comprises one or more than one cellulase and one or more than one pectinase, wherein a concentration of the one or more than one pectinase is about 1% (v/v) and a concentration of the one or more than one cellulase is about 1% (v/v), about 600 mM mannitol, about 75 mM citrate, and a buffer or buffer system which maintains a pH of about 6.9, at room temperature—with agitation for about 16 hours, wherein substantially all of the protoplasts in the protoplast fraction are disrupted protoplasts;
• and
• c. separating the plant debris from the digested fraction using filtration with a mesh size of more than 250 μm, centrifuging at about 5,000 g for about 15 minutes at room temperature to remove organelles, and to produce a supernatant, and recovering the plant-derived antibodies from the supernatant.