Protease digestion from wheat stillage within a dry grind ethanol facility

Area of Science:

• Biotechnology
• Biochemical Engineering
• Sustainable Chemistry

Background:

• The expanding starch-based ethanol market generates large volumes of distiller's grains, a valuable coproduct.
• Valorizing distiller's grains by isolating protein fractions can create precursors for biochemicals and bioplastics, reducing reliance on fossil fuels.

Purpose of the Study:

• To investigate the enzymatic extraction of protein peptides from wheat heavy stillage.
• To quantify the energy savings associated with this enzymatic process compared to fossil fuel-based methods.

Main Methods:

• Utilized commercially available proteases, specifically Protex 6L (Genencor), for enzymatic protein extraction.
• Employed wet heavy stillage as the feedstock to assess protein solubility and peptide characteristics.

Main Results:

• Enzymatic extraction demonstrated energy savings of approximately 1.5 to 3.0 GJ/ton of wheat stillage.
• Protex 6L at 0.1% w/w loading rendered approximately 57% of the protein soluble within 24 hours.
• A significant portion (32%) of the protein was already soluble in wet stillage, highlighting its importance as a feedstock.
• Extracted peptides were characterized to be less than 6 kDa in size.

Conclusions:

• Enzymatic protein peptide extraction from wheat stillage is an energy-efficient and sustainable process.
• Wet heavy stillage is a preferred feedstock over dried distiller's grains for maximizing protein recovery.
• Further optimization through fed batch protease addition and improved protease cocktails can enhance protein removal efficiency.