Large scale purification of rapeseed proteins (Brassica napus L.)

Rapeseed (Brassica napus L.) cruciferin (12S globulin), napin (2S albumin) and lipid transfer proteins (LTP) were purified at a multi-g scale. The procedure developed was simple, rather fast and resolutive; it permitted the recovery of these proteins with a good yield, such as 40% for cruciferin and 18% for napin. Nanofiltration eliminated the major phenolic compounds. The remaining protein fraction was fractionated by cation exchange chromatography (CEC) on a streamline SP-XL column in alkaline conditions. The unbound neutral cruciferin was polished by size exclusion chromatography. The alkaline napin isoforms and LTP, adsorbed on the beads, were eluted as a whole fraction and further separated by an other CEC step at acidic pH. Napins were polished by hydrophobic interaction chromatography (HIC). The fractions were characterized by reverse phase HPLC, electrophoresis, N-terminal sequencing and mass spectrometry. All the fractions contained less than 5% of impurities.