Blacksburg, Virginia
August 11, 2004
Recovery, purification of therapeutic proteins an economic and
scientific challenge
The economics of producing
biopharmaceuticals from transgenic plants such as tobacco is
still a roadblock to producing large quantities of urgently
needed medicines, especially for people in underdeveloped
nations.
Chenming (Mike) Zhang is
testing a variety of ways to economically recover recombinant
proteins from transgenic tobacco using different protein
separation techniques.
Zhang, an assistant professor
in the Department of Biological Systems Engineering (BSE) in the
College of Engineering at Virginia
Tech, is working with a team of three Ph.D. students to
develop transgenic tobacco plants able to express recombinant
proteins economically. Recombinant proteins are potential
therapeutic agents for treating human and animal diseases and
creating new vaccines. Plant-made vaccines are especially
beneficial because plants are free of human diseases, reducing
the cost to screen for viruses and bacterial toxins.
"Recombinant protein production
from transgenic plants is challenging, not just from the
molecular biology aspect of creating high expression plant
lines, but also from the engineering aspect of recovering and
purifying the proteins economically -- the importance of which
cannot be overlooked," Zhang said.
Recombinant proteins are
proteins expressed by a host other than their native hosts. For
example, if the gene for human growth hormone is inserted into
the genetic code of yeast (gene recombination), then the
corresponding protein expressed in the yeast is called
recombinant human growth hormone.
Zhang's research starts with
introducing the genes of interest into tobacco plants and then
developing economical processes for recovering and purifying the
expressed proteins. Relaxin, one of the proteins his team is
studying, could potentially benefit patients with asthma, hay
fever, and even cardiovascular disease.
Because most recombinant
proteins are for therapeutic uses, they need to be highly
purified to be safe for human use. Thus, once a protein is
expressed, whether by transgenic tobacco or bacteria, the
protein first needs to be recovered into liquid solutions before
purification.
"Because of the high purity
required, the purification is rigorous and not surprisingly,
very expensive. Therefore, development of more economical
techniques for protein purification is always an engineering
challenge in order to lower the cost of therapeutic proteins or
biopharmaceuticals," Zhang said.
Zhang uses tobacco in his
research because it is a non-food crop and is well suited as a
"factory" for recombinant protein production. The leafy green
tobacco plant is relatively easy to alter genetically and
produces thousands of seeds and a great deal of biomass. As a
non-food crop, genetically manipulated tobacco will not pose a
safety threat to products consumed by humans. "Since tobacco is
neither a food nor a feed-crop, transgenic tobacco will not
enter our food chain," Zhang said.
The research is funded by the
Jeffress Memorial Trust and the Tobacco Initiative.
Zhang is the director of both
the Protein Separation Laboratory and the Unit Operations
Laboratory at Virginia Tech. The Protein Separation Laboratory
supports research in protein expression and purification process
development from transgenic plants and other expression systems.
The Unit Operations Laboratory supports a course by the same
name taught by Zhang in biological systems engineering. He is
also affiliated with the Virginia Tech-Wake Forest University
School of Biomedical Engineering and Sciences.
The College of Engineering
Dean's Award for Outstanding Assistant Professor was presented
to Zhang in 2004. His nomination was based on his extraordinary
level of activities and accomplishments in curriculum
development and teaching, development of a viable research
program, and his cooperative efforts with colleagues at Virginia
Tech and around the nation.
Before coming to Virginia Tech
in 2001, Zhang was a research and development scientist for two
years at Covance Biotechnology Services (now Diosynth RTP) in
Cary, N. C.
Zhang received his bachelor's
and master's degrees in metallurgical physical chemistry from
the University of Science and Technology in Beijing, China, in
1986 and 1991, respectively. He received a second master's
degree in physical and analytical chemistry in 1996 from Iowa
State University as well as his Ph.D. in chemical engineering in
1999.
The College of Engineering
at Virginia Tech is internationally recognized for its
excellence in 14 engineering disciplines and computer science.
The college's 5,600 undergraduates benefit from an innovative
curriculum that provides a "hands-on, minds-on" approach to
engineering education, complementing classroom instruction with
two unique design-and-build facilities and a strong Cooperative
Education Program. With more than 50 research centers and
numerous laboratories, the college offers its 2,000 graduate
students opportunities in advanced fields of study such as
biomedical engineering, state-of-the-art microelectronics, and
nanotechnology.
Learn more about Dr. Zhang
at
http://www.bse.vt.edu/BSE_Dept/Faculty.php#Zhang or
http://www.sbes.vt.edu/faculty/zhang.htm |