In-Vivo Formation of Natural-Synthetic Diblock Copolymers

Our laboratory pioneered a new research area that we termed 'polyethylene oxide (PEG) modulated fermentation'. It was discovered that by addition of PEG to culture media during microbial polyester formation, the following occurs: i) PEG acted as an in-vivo chain terminating agent that allowed 'tailoring' of microbial polyester molecular weight, and ii) PEG enabled for changes in microbial polyester repeat unit composition and sequence distribution along chains. For the first time block copolymers that consisted of a synthetic segment (PEG) and a natural polymer was formed in vivo. This research has identified a route by which synthetic-natural block copolymers can be synthesized in-vivo by the identification of synthetic oligomers or polymers that act as terminators of microbial polymer synthesis.

Figure 24. NMR analysis of PHAs formed intracellularly shows that PEG enters cells and reacts at the PHA-synthase to terminate chains forming PHA-PEG diblocks.

References

• R. D. Ashby, F.-Y. Shi and R.A. Gross, “A Tunable Switch to Regulate the Synthesis of Low and High Molecular Weight Microbial Polyesters” Biotechnology and Bioengineering, Vol. 62 (1), (1999).(PDF)
• Richard Ashby, Feng-Ying Shi, and Richard A. Gross, “Use of poly(ethylene glycol) to control the end group structure and molecular weight of poly(3-hydroxybutyrate) formed by Alcaligenes latus DSM 1122,” Tetrahedron, Vol 53, No. 45, 15209-115223 (1997).(PDF)
• Fengying Shi, Richard D. Ashby and Richard A. Gross, “Formation by Alcaligenes species of Microbial Polyesters Containing 3-Hydroxybutyrate and 4-Hydroxybutyrate Repeat Units: Investigation of Product Homogeneity”, Macromolecules, Vol. 30, 2521-2523 (1997).(PDF)
• Feng-Ying Shi, Richard Ashby and Richard A. Gross, "Use of Poly(ethylene glycol)s to Regulate Poly(3-hydroxybutyrate) Molecular Weight during Alcaligenes eutrophus Cultivations", Macromolecules, Vol. 29, 7753-7758 (1996).(PDF)
• Feng-Ying Shi, Denise Rutherford and Richard A. Gross, "Microbial Polyester Synthesis: Effects of Poly(ethylene glycol) on Product Composition, Repeat Unit Sequence and End Group Structure", Macromolecules, Vol. 29, 10-17 (1996).(PDF)

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