title: Biosynthesis of novel thermoplastic polythioesters by engineered Escherichia coli.
abstract: The development of non-petrochemical sources for the plastics industry continues to progress as large multinationals focus on renewable resources to replace fossil carbon. Many bacteria are known to accumulate polyoxoesters as water-insoluble granules in the cytoplasm. The thermoplastic and/or elastomeric behaviour of these biodegradable polymers holds promise for the development of various technological applications. Here, we report the synthesis and characterization of microbial polythioesters (PTEs), a novel class of biopolymers of general technological relevance. Biosynthesis of PTE homopolymers was achieved using a recombinant strain of Escherichia coli that expressed a non-natural pathway consisting of a butyrate kinase, a phosphotransbutyrylase, and a PHA synthase. Different homopolymers were produced, consisting of either 3-mercaptopropionate, 3-mercaptobutyrate, or 3-mercaptovalerate repeating units, if the respective mercaptoalkanoic acids were provided as precursor substrates to the fermentative process. The PTEs contributed up to 30% (w/w) of the cellular dry weight and were identified as hydrophobic inclusions in the cytoplasm. The chemical and stereochemical homogeneity of the purified PTEs were identified by different methods, and the estimated physical properties were compared to the oxypolyester equivalents, revealing low crystalline order and, for the poly(3-mercaptopropionate) improved thermal stability. The ability to produce PTEs through a biosynthetic route opens up new avenues in the field of biomaterials.
authors.affiliation: Institut für Mikrobiologie, Westfälische Wilhelms-Universität Münster, Corrensstrasse 3, D 48149 Münster, Germany.
authors.forename: Tina
authors.initials: T
authors.lastname: Lütke-Eversloh
authors.forename: Andreas
authors.initials: A
authors.lastname: Fischer
authors.forename: Uwe
authors.initials: U
authors.lastname: Remminghorst
authors.forename: Jumpei
authors.initials: J
authors.lastname: Kawada
authors.forename: Robert H
authors.initials: RH
authors.lastname: Marchessault
authors.forename: Ansgar
authors.initials: A
authors.lastname: Bögershausen
authors.forename: Martin
authors.initials: M
authors.lastname: Kalwei
authors.forename: Hellmut
authors.initials: H
authors.lastname: Eckert
authors.forename: Rudolf
authors.initials: R
authors.lastname: Reichelt
authors.forename: Shuang-Jiang
authors.initials: SJ
authors.lastname: Liu
authors.forename: Alexander
authors.initials: A
authors.lastname: Steinbüchel
mesh_terms: D001704:Biopolymers / Q000096:biosynthesis*; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure; D004952:Esters; D005818:Genetic Engineering; D009682:Magnetic Resonance Spectroscopy; D008854:Microscopy, Electron
chemical_list: D001704:Biopolymers; D004952:Esters