Biorefining of Corn Brings Gelatin Production Into the 21st Century

Newswise — Scientists are reporting an advance toward turning corn plants into natural factories for producing gelatin to replace animal-sourced gelatin widely used by the pharmaceutical industry for manufacturing capsules and tablets. The advance, described today at the 234th national meeting of the American Chemical Society, may lead to a safe, inexpensive source of this protein for manufacturers who now rely on material obtained as a by-product of meat production.

Today, production of gelatin, a jelly-like substance, relies on the same fundamental methodology employed since commercial production began in the 17th century: Gelatin is derived from the break-down of collagen, which is a component of skin, tendon, bone, cartilage and connective tissue of animals. While there are no naturally occurring plant sources of gelatin, scientists have successfully modified plants, such as corn, to have a gene that results in the production of "recombinant" gelatin.

About 55,000 tons of animal-sourced gelatin are used every year to produce capsules and tablets for medicinal purposes. Plant-derived recombinant gelatin would address concerns about the possible presence of infectious agents in animal by-products and the lack of traceability of the source of the raw materials currently used to make gelatin. However, finding ways to recover and purify recombinant gelatin from plants has remained a challenge because only very low levels accumulate at the early stages of the development process.

Now, scientists at Iowa State University in Ames and FibroGen, Inc., in South San Francisco say they have developed a purification process to recover these small quantities of recombinant gelatin present in the early generations of transgenic corn. The method uses a four-step recovery system to separate the recombinant protein from other corn proteins with sufficient purity that its structure and composition can be verified, says Charles Glatz, Ph.D., a chemical engineer at Iowa State University who directed the work.

"Protein production from transgenic plants is a challenging process, with potential pitfalls all along the way," Glatz says. "It is important to develop methods in the early stages of the development program to purify gelatin to demonstrate that it can be produced properly."

The studies establish transgenic corn as a viable way to produce gelatin and potentially other products, Glatz says. In time, researchers may also be able to develop a variety of "designer" gelatins, with specific molecular weights and properties tailored to suit various needs of products containing gelatin.

"Corn is an ideal production unit, because it can handle high volumes at a low cost," he says. In addition the recombinant gelatin is free from the safety concerns of using meat byproducts.

The purification process relies on chromatographic and filtration techniques, building upon methods developed by FibroGen to recover recombinant gelatin produced in yeast.

Glatz says ultrafiltration allowed the group to take advantage of the size difference between the recombinant protein and other corn proteins.

"This step greatly reduced the process volume for later chromatographic steps, and was crucial to achieving a high purification factor."

The group is now working to refine the method and boost the overall recombinant protein yields in corn, he says. Though the procedure requires more testing, Glatz says the technique could someday be used to produce high-grade gelatin in a safe and inexpensive manner.

Overall costs could be further reduced by combining the production of gelatin in corn with the extraction of non-protein parts of the grain — such as oils and starches — that are now grown and harvested for biodiesel and ethanol production, he adds.

"Corn wouldn't be planted for its gelatin alone, but those products could help off-set the cost of biorefineries that use corn to produce other products," he says.

Cheng Zhang, a doctoral student at Iowa State University, presented details of the new purification process at the American Chemical Society meeting.

The American Chemical Society is a nonprofit organization chartered by the U.S. Congress and a global leader in providing access to chemistry-related research through its multiple databases, peer-reviewed journals and scientific conferences. Its main offices are in Washington, D.C., and Columbus, Ohio.

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ALL PAPERS ARE EMBARGOED UNTIL DATE AND TIME OF PRESENTATION, UNLESS OTHERWISE NOTED

The paper on this research, BIOT 293, will be presented at 5:30 PM, Wednesday, 22 August 2007, during the symposium, "Poster Session."

BIOT 293Purification of recombinant collagen from transgenic corn seed

Program Selection: Division of Biochemical TechnologyTopic Selection: Poster Session: Downstream Processing

Abstract

Gelatin derived from collagen is widely used as a biomaterial in pharmaceutical capsules and other medical applications. Currently, collagen is produced from animal sources leading to concerns related with the presence of infectious agents and lot-to-lot variability resulting in lack of uniformity in composition and size. We are investigating the possibility of using genetically modified corn to develop a more consistent and animal-contaminant free collagen to be used for gelatin production.

A pure protein sample is needed to determine the composition of the collagen protein expressed in corn. The low expression level (3 mg of protein/kg of seed or 3 ppm) obtained in the first generation corn seeds posed a significant challenge for the development of an effective purification process. As no effective affinity chromatography system was available, a purification process based on ultrafiltration and a three-step chromatography was developed to achieve a recombinant collagen purity of about 80-90% with a purification factor of more than 3000. Ultrafiltration was a useful early step that took advantage of the size difference between the recombinant collagen and contaminating corn seed proteins. This step not only greatly reduced the process volume for later chromatographic steps, but also achieved a purification factor of 5-10. Chromatographic resins and elution conditions (pH, ionic strength, gradient) were identified to successfully obtain samples suitable for the characterization of collagen from a low purity transgenic source.

Researcher Provided Non-Technical Summary

Briefly explain in lay language what you have done, why it is significant and what are its implications (particularly to the general public)

Our collaborators have engineered corn to produce a human collagen in corn. Collagen is a protein very plentiful in connective tissues of mammals and collagen recovered from slaughterhouse waste is used in food (gelatin), cosmetics, and medical applications. Having a plant source would avoid concerns about the safety of animal byproducts. To know whether the corn-based collagen can replace animal-based collagen requires purifying this collagen to examine its equivalence. The significance of our work is that we have designed a purification process that is capable of purifying and enriching this collagen even though it is currently only present at very low levels in the corn grain.

Since collagens that are currently used in medical applications are mainly produced from animals, the product produced from plants will be more uniform in composition and free from the safety concerns of using meat byproducts. In addition, production of this protein could be combined with use of the other components of the grain for ethanol production, providing more diversified products from much-anticipated biorefineries.

How new is this work and how does it differ from that of others who may be doing similar research?

No commercially available collagens have been produced from plants yet, so we are investigating an alternative to produce a safer product. Tobacco has been investigated for producing collagens by others. Our work focuses on corn and the design of an effective process to purify the collagens and is providing more extensive investigation of whether the plant product possesses the desired properties and, if it goes as planned, offers even better properties because of greater uniformity.