ARS | Publication request: Utilizing Protein-lean Co-products from Corn Containing Recombinant Pharmaceutical Proteins for Ethanol Production

Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 31, 2010
Publication Date: September 1, 2010
Citation: Paraman, I., Moeller, L., Scott, M.P., Wang, K., Glatz, C., Johnson, L. 2010. Utilizing protein-lean co-products from corn containing recombinant pharmaceutical proteins for ethanol production. Journal of Agricultural and Food Chemistry. 58(19):10419-10425.

Interpretive Summary: Production of high value proteins in recombinant corn grain can be economically advantagous in certain situations. The economic advantages would be increased if the co-products remaining after extraction of the recombinant protein could put to use as well. The potential for contamination of co-products with traces of the recombinant protein rules out their use in food and feed products. We examined the possibility of using these co-products for ethanol production and found that extraction of the recombinant protein did not negatively impact the suitability of grain for use as an ethanol feedstock. Moreover, the process of ethanol production, with a slight modification, inactivated or eliminated the recombinant protein from the ethanol co-products. These results demonstrate the feasibility of producing ethanol safely from spent recombinant protein co-products. Doing this will increase the economic benefit of producing recombinant proteins in corn. This adds value to corn enabling it to be used for recombinant protein production while still serving as a feedstock to meet our liquid fuel needs. This will benefit the public by decreasing production costs of biofuels and high value proteins.

Technical Abstract: Protein-lean fractions of corn (maize) containing recombinant (r) pharmaceutical proteins were used to produce fuel ethanol and residual r-proteins in the co-product, distillers dry grains with solubles (DDGS), were determined. Transgenic corn lines containing recombinant green fluorescence protein (r-GFP) and a recombinant subunit vaccine of E. coli enterotoxin (r-LTB) primarily expressed in endosperm, and another two corn lines containing recombinant human collagen (r-CIa1) and r-GFP primarily expressed in germ were used as model systems. The kernels were either ground and used directly or dry fractionated to recover germ-rich fractions prior to grinding for fermentation. The finished beers contained 127-139 g/L ethanol and ethanol levels did not differ among transgenic and normal corn feedstocks, indicating the residual r-proteins did not negatively affect ethanol production. r-Protein extraction and germ removal did not negatively affect fermentation of the remaining mass. Most r-proteins were inactivated during the mashing process used to prepare corn for fermentation. No functionally active r-GFP or r-LTB proteins were found after fermenting the r-protein-spent solids; however, a small quantity of residual r-CIa1 was detected in DDGS. Protease treatment during fermentation completely hydrolyzed the residual r-CIa1 and no residual r-proteins were detectable in DDGS.