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Feature Story
reed magazine logoSeptember 2010

Ten from ’10 continued

Shreya Shrestha, biology

  • Hometown: Lalitpur, Nepal
  • Adviser: David Dalton
  • Thesis: Making the Good Plastic: Studying the Efficacy of a Novel Poly(3-hydroxybutyrate) Expression System in Poplar
  • What it’s about: Bacteria-derived biodegradable polymer, poly(3-hydroxybutyrate) (PHB), has emerged as a potential solution to the environmental challenges of synthetic thermoplastic, which never breaks down. I looked at the effects of synthesizing this polymer in transgenic poplar trees.
  • What it’s really about: Growing biodegradable plastic.
  • Cool Stuff I did: Research! Came to love dogs (they tend to be a bit fierce where I come from). House adviser. Tutored at DoJo. Model United Nations. Saw the ocean. Learned to cook. Won J.W. Hairgrove scholarship and a McGill Lawrence Internship Award to bring medical care to underserved communities in Nepal. Went to a Metallica concert—it rocked!
  • Most influential book I read: Streptomyces in Nature and Medicine, by David A. Hopwood.
  • How Reed changed me: When I got here I was anxious, naive, and struggled to adapt to American culture—we didn’t have warm showers in Nepal. I’ve become a better thinker, more curious, more open to new ideas. Thanks to my years at Reed, I know where I’m headed. I want to become a doctor and work on access to health care in developing countries and in the U.S. I know I can make a difference.
  • What’s next: Do research at the National Institutes of Health. After that, medical school.

Thesis Closeup:

Growing Biodegradable Plastic.

In 1925, a French researcher named Maurice Lemoigne discovered that certain bacteria are capable of manufacturing plastic, in particular a polymer known as poly(3-hydroxybutyrate) or PHB. This finding aroused scant interest at the time, but decades later—with the planet awash in plastic pollution—this discovery gained enormous significance, because PHB is biodegradable.

In recent years, researchers have transferred the PHB-making genes from bacteria into various crops such as peas, potatoes, sugar cane, and tobacco, searching for a practical way to produce PHB. One promising plant is the poplar tree. Poplars can be engineered to manufacture PHB in their leaves, which can be harvested without harming the trees themselves. With a biomass larger than any other PHB-making plants to date, poplars could produce a high and economically viable yield.

One drawback with using plants to make PHB is that their growth is typically impaired due to the diversion of their resources towards making the plastic. Shreya investigated the effects of inserting a novel inducible promoter—an on-off switch—into poplar saplings so that PHB production can be turned off while the tree is growing, then turned on when it has reached maturity. Raising 144 saplings in the biology department’s greenhouse, she found that within the two groups of poplars studied, PHB production using the on/off switch didn’t slow the plants’ growth. (To be economically viable, approximately 12 percent of the leaves’ dry weight should consist of PHB.)—CL

reed magazine logoSeptember 2010