title: Disassembly and reassembly of polyhydroxyalkanoates: recycling through abiotic depolymerization and biotic repolymerization.
abstract: An abiotic-biotic strategy for recycling of polyhydroxyalkanoates (PHAs) is evaluated. Base-catalyzed PHA depolymerization yields hydroxyacids, such as 3-hydroxybutyrate (3HB), and alkenoates, such as crotonate; catalytic thermal depolymerization yields alkenoates. Cyclic pulse addition of 3HB to triplicate bioreactors selected for an enrichment of Comamonas, Brachymonas and Acinetobacter. After each pulse, poly(3-hydroxybutyrate) (P3HB) transiently appeared: accumulation of P3HB correlated with hydrolysis of polyphosphate; consumption of P3HB correlated with polyphosphate synthesis. Cells removed from the cyclic regime and incubated with 3HB under nitrogen-limited conditions produced P3HB (molecular weight>1,000,000Da) at 50% of the cell dry weight (<8h). P3HB also resulted from incubation with acetate, crotonate, or a mixture of hydrolytic depolymerization products. Poly(3-hydroxybutyric acid-co-3-hydroxyvaleric acid) (PHBV) resulted from incubation with valerate or 2-pentenoate. A recycling strategy where abiotic depolymerization of waste PHAs yields feedstock for customized PHA re-synthesis appears feasible, without the need for energy-intensive feedstock purification.
authors.affiliation: Department of Civil and Environmental Engineering, Stanford University, Stanford, CA 94305-4020, USA.
authors.forename: Jaewook
authors.initials: J
authors.lastname: Myung
authors.affiliation: Department of Civil and Environmental Engineering, Stanford University, Stanford, CA 94305-4020, USA.
authors.forename: Nathaniel I
authors.initials: NI
authors.lastname: Strong
authors.affiliation: Department of Civil and Environmental Engineering, Stanford University, Stanford, CA 94305-4020, USA.
authors.forename: Wakuna M
authors.initials: WM
authors.lastname: Galega
authors.affiliation: Department of Civil and Environmental Engineering, Stanford University, Stanford, CA 94305-4020, USA.
authors.forename: Eric R
authors.initials: ER
authors.lastname: Sundstrom
authors.affiliation: Department of Chemistry, Stanford University, Stanford, CA 94305-4401, USA.
authors.forename: James C A
authors.initials: JCA
authors.lastname: Flanagan
authors.affiliation: Department of Civil and Environmental Engineering, Stanford University, Stanford, CA 94305-4020, USA.
authors.forename: Sung-Geun
authors.initials: SG
authors.lastname: Woo
authors.affiliation: Department of Chemistry, Stanford University, Stanford, CA 94305-4401, USA.
authors.forename: Robert M
authors.initials: RM
authors.lastname: Waymouth
authors.affiliation: Department of Civil and Environmental Engineering, Stanford University, Stanford, CA 94305-4020, USA; Woods Institute for the Environment at Stanford, USA; William and Cloy Codiga Resource Recovery Center at Stanford, USA. Electronic address: ccriddle@stanford.edu.
authors.forename: Craig S
authors.initials: CS
authors.lastname: Criddle
mesh_terms: D020155:3-Hydroxybutyric Acid / Q000096:biosynthesis / Q000737:chemistry; D019149:Bioreactors; D001709:Biotechnology / Q000379:methods; D003437:Crotonates / Q000737:chemistry; D008401:Gas Chromatography-Mass Spectrometry; D006358:Hot Temperature; D008954:Models, Biological; D015394:Molecular Structure; D054813:Polyhydroxyalkanoates / Q000096:biosynthesis / Q000138:chemical synthesis / Q000737:chemistry*; D058105:Polymerization; D011122:Polyphosphates / Q000737:chemistry; D059027:Recycling / Q000379:methods*
chemical_list: D003437:Crotonates; D054813:Polyhydroxyalkanoates; D011122:Polyphosphates; D020155:3-Hydroxybutyric Acid
keywords: PHB; PHBV; Polyhydroxyalkanoate; Polyphosphate; Recycling