Utilizing protein-lean coproducts from corn containing recombinant pharmaceutical proteins for ethanol production

Area of Science:

• Biotechnology
• Agricultural Science
• Biofuel Production

Background:

• Corn (maize) is a primary feedstock for fuel ethanol production.
• Transgenic crops offer potential for producing valuable recombinant proteins.
• Assessing the impact of recombinant proteins on ethanol production and coproduct safety is crucial.

Purpose of the Study:

• To evaluate protein-lean corn fractions with recombinant proteins as a feedstock for fuel ethanol.
• To determine residual recombinant protein levels in distillers dry grains with solubles (DDGS).
• To assess the impact of recombinant proteins on ethanol yield and the safety of DDGS.

Main Methods:

• Utilized transgenic corn lines expressing recombinant green fluorescence protein (r-GFP), recombinant Escherichia coli enterotoxin subunit vaccine (r-LTB), and recombinant human collagen (r-CIα1).
• Fermented whole ground kernels and fractionated corn (germ-removed) for ethanol production.
• Analyzed residual r-proteins in DDGS using biochemical assays and fermentation inactivation studies.

Main Results:

• Ethanol concentrations were comparable between transgenic and normal corn feedstocks (127-155 g/L).
• Recombinant protein extraction and germ removal did not negatively affect fermentation efficiency.
• Most r-proteins were inactivated during mashing; residual r-CIα1 was detected but fully hydrolyzed by protease treatment.

Conclusions:

• Transgenic corn containing recombinant proteins can be effectively used for fuel ethanol production without compromising yield.
• The mashing process significantly inactivates most recombinant proteins, enhancing the safety of the DDGS coproduct.
• Specific event-based safety evaluations are necessary for DDGS intended for applications where residual proteins are a concern, though protease treatment ensures complete hydrolysis.