title: Poly(ethylene glycol)-mediated molar mass control of short-chain- and medium-chain-length poly(hydroxyalkanoates) from Pseudomonas oleovorans.
abstract: Three strains of Pseudomonas oleovorans, a well known poly(hydroxyalkanoate) (PHA) producer, were tested for the ability to control PHA molar mass and end group structure by addition of poly(ethylene glycol) (PEG) to the fermentation medium. Each strain of P. oleovorans - NRRL B-14682 (B-14682), NRRL B-14683 (B-14683), and NRRL B-778 (B-778) - synthesized a different type of PHA from oleic acid when cultured under identical growth conditions. Strain B-14682 produced poly(3-hydroxybutyrate) (PHB), while B-14683 synthesized a medium-chain-length PHA ( mcl-PHA) with a repeat unit composition ranging from C4 to C14 and some mono-unsaturation in the C14 alkyl side chains. Strain B-778 synthesized a mixture of PHB (95 mol%) and mcl-PHA (5 mol%). The addition of 0.5% (v/v) PEG (M(n) =200 g/mol, PEG-200) to the fermentation broth of strains B-14682 and B-778 resulted in chain termination through esterification at the carboxyl terminus of the PHB with PEG chain segments, thus reducing the molar mass by 54% and 23%, respectively. The molar mass of the mcl-PHA produced by strains B-14683 and B-778 also showed a 34% and 47% reduction in the presence of PEG-200, respectively, but no evidence of esterification was present. PEG-400 (M(n) =400 g/mol) had a reduced effect on PHA molar mass. In fact, the molar masses of the mcl-PHA derived from strain B-14683 and both the PHB and mcl-PHA from B-778 were unchanged by PEG-400. In contrast, the PHB produced by B-14682 showed a 35% reduction in molar mass in the presence of PEG-400.
authors.affiliation: United States Department of Agriculture, Agricultural Research Service, Eastern Regional Research Center, 600 E. Mermaid Lane, Wyndmoor, PA 19038 USA. rashby@arserrc.gov
authors.forename: R D
authors.initials: RD
authors.lastname: Ashby
authors.forename: D K Y
authors.initials: DK
authors.lastname: Solaiman
authors.forename: T A
authors.initials: TA
authors.lastname: Foglia
mesh_terms: D000473:Alkanes / Q000378:metabolism; D001704:Biopolymers / Q000378:metabolism*; D002850:Chromatography, Gel; D003470:Culture Media; D005285:Fermentation; D006880:Hydroxy Acids / Q000378:metabolism*; D011092:Polyethylene Glycols / Q000494:pharmacology*; D011108:Polymers / Q000378:metabolism; D011549:Pseudomonas / Q000254:growth & development / Q000378:metabolism*
chemical_list: D000473:Alkanes; D001704:Biopolymers; D003470:Culture Media; D006880:Hydroxy Acids; D011108:Polymers; D011092:Polyethylene Glycols