"Ultimately, we want to be able to take a designed E. coli off of the
shelf and drop into it the enzymes that constitute a particular
biosynthetic pathway in order to make exactly the product we want,"
said Mattheos A. G. Koffas, Ph.D., assistant professor of chemical and
biological engineering in the School of Engineering and Applied
Sciences and leader of the UB team.
The UB approach to synthetic chemistry addresses some of the major
challenges in conventional industrial production of specialty
chemicals.
Through the use of specially adapted bacteria, specialized enzymes and
natural feedstocks, microbial biosynthesis reduces or eliminates the
need for petrochemical sources, elevated temperatures, toxic heavy
metal catalysts, extremes of acidity and dangerous solvents, Koffas
said.
In addition, the natural enzymes the UB researchers are using can
facilitate chemical reactions that are difficult to accomplish through
conventional chemistry, such as chiral synthesis, glycosylations and
targeted hydroxylations, common but challenging steps in many
syntheses.
"We are finding out how we can actually 'train' microbial systems to
produce high yields of chemicals to be used as pharmaceuticals and to
make production processes more efficient, less expensive and more
environmentally friendly," Koffas said.
As with any commercial endeavor, process efficiency is a critical
concern, he noted.
In work published in Applied and Environmental Microbiology in June,
Koffas and his colleagues produced about 400 milligrams of flavonoids
per liter of cell culture, far above the next highest yield of about
20 milligrams per liter produced by other microbial synthesis efforts.
"We have done this by increasing the amount of precursor available and
re-engineering the native microbial metabolism," he explained, adding
that they have taken different approaches to identifying the pathways
that lead to the biosynthesis of precursors for desired compounds.
"Further improvement of production yields are possible and various
approaches are being pursued by our team at this time," he said.
Another major challenge for microbial biosynthesis is that the enzymes
required for certain chemical steps have special requirements that the
host cell cannot meet efficiently, Koffas said. In some cases, the
enzyme needs to be re-engineered, while in others the host cell needs
modification.
Koffas' lab recently achieved the functional expression in E. coli of
P450 monooxygenases, enzymes that are used widely in nature, but are
not readily expressed in most industrially important microorganisms.
"P450 is very important in the synthesis of natural products," said
Koffas. "For example, both Taxol, the breast cancer drug that is
currently produced from plant cultures, and artemisinin, the
anti-malaria drug, have P450 enzymes in their biosynthetic pathways."
The Koffas lab has introduced ways to modify both the P450
monooxygenase enzymes and the host cell, thereby improving their yield
of flavonoids.
Microbial biosynthesis methods also are making it easier to create
analogs of existing drugs, as well as new molecules for a broad range
of therapeutics.
The UB researchers are particularly interested in developing novel
molecules that can be used to treat chronic diseases, such as type II
diabetes and obesity.
They also are using the methods to produce specialty compounds, such
as natural pigments, that could replace chemical dyes in food.
Koffas' goal is to employ these microbial synthesis methods for a wide
variety of applications.
Flavonoids, which are of interest to pharmaceutical companies because
of their antioxidant and anti-carcinogenic properties, are difficult
to produce using currently available methods.
Microbial synthesis strategies also are being adapted by the UB
researchers for the biosynthesis of other commercially significant
classes of compounds, including vitamins, anti-cancer drugs,
anti-parasitic drugs, dyes and food supplements.
The UB group is working on boosting yields further and hopes to
achieve pilot scale production of flavonoids by the end of this year.
Koffas's research has received funding from the National Science
Foundation, UB's New York State Center of Excellence in Bioinformatics
and Life Sciences and the Independent Research and Development Fund of
the UB Office of the Vice President of Research.
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