Plant Protein Purification

Environment and sustainability concerns pushes to develop production of plant-based proteins to complement traditional animal source.

Within the plant-based protein world, the protein ingredients represent high added value products due to their functional properties.

In order to preserve natural functionalities, production process must minimize potential denaturation effects (thermal, chemical or mechanical) and prevent carrying natural contamination (suspended solids, bioburden, fat, antinutritional factors, etc.) through protein purification methods. 

Current wet purification process usually includes at least one step of chemical and/or thermal precipitation (at iso-electric point) followed by centrifugation. Also this solution is well sprayed, it creates partial protein denaturation and loss of soluble proteins.

Crossflow microfiltration is used as a protein purification technique used on the raw solution to produce a very clean solution of native proteins (essentially free from suspended solids, bioburden, fat, etc.).  This can be further purified with other membranes (UF/NF/RO) and/or chromatography.

Crossflow microfiltration is used for decades in dairy industry to purify the milk (selective removal of bioburden and residual fat) and to fractionate the milk (separating casein from whey proteins) while maintaining native properties of each type of proteins. Same solutions are also used to purify other type of protein solutions (animal-based, plant-based or produced by microorganisms).

Crossflow filtration is a physical barrier achieving high purification yield, significantly better than centrifugation.

The crossflow systems are fully enclosed, automatized, regularly cleaned and sanitized in place (minimum manpower).

In production, they operate at temperatures low enough to prevent any thermal denaturation of the proteins

To produce functional proteins, we can use different membranes grades (separately or in combination):

• “Open” Microfiltration to remove undissolved solids and produce a “clean” protein solution
• “Tight” Microfiltration to fractionate proteins according to their size (e.g.: separate globulins from albumins)
• “Open” Ultrafiltration to concentrate large proteins 
• “Tight” Ultrafiltration to concentrate small proteins before final evaporation/ drying 

In each case we can “wash” / purify the protein concentrate (Diafiltration) to remove residual sugars, salts, etc.

Crossflow filtration contributes to produce protein concentrates with:

• Native quality and functionality,
• Very low bacterial/spore counts,
• Very low-fat content,
• No suspended solids.

Membrane based processes allow also to recover added value from side streams thus turning a “waste” into valuable products.

For example, when we filter the centrifuge overflow after pH precipitation of the globulins, we can recover:

• native dissolved albumins (valuable product with interesting properties)
• unsettled globulin fines (globulin yield increase)

In both cases, we can wash the concentrate to improve product purity by eliminating sugars, salts, antinutritional factors, etc.