title: Glucose/lipid mixed substrates as a means of controlling the properties of medium chain length poly(hydroxyalkanoates).
abstract: Glucose-triacylglycerol (TAG) mixed substrates were used to modulate the physical and mechanical properties of medium-chain-length poly(hydroxyalkanoates) (mcl-PHAs). Pseudomonas resinovorans NRRL B-2649 grew and produced mcl-PHAs on glucose and TAGs (coconut oil, C; soybean oil, S) after 24 h in a shake flask culture. However, with the exception of coconut oil, maximum cell productivity was not reached in any of the cultures until 72 h post-inoculation. Here, 50:50 mixtures of glucose and coconut oil (glc/C) or glucose and soybean oil (glc/S) resulted in intermediate cell productivities with a maximum of 57% and 48% of the CDW at 72 h, respectively. In addition, mixed substrates resulted in mcl-PHAs with compositions that varied slightly over time. PHA-glc/C and PHA-glc/S were composed of 7 mol % and 8 mol % 3-hydroxydodecenoic acid (C(12:1)), respectively at 72 h. These concentrations were intermediate to the C(12:1) concentration of PHA-glc and respective PHA-TAG. Also, significant amounts of 3-hydroxytetradecanoic acid (C(14:0)), 3-hydroxytetradecenoic acid (C(14:1)), and 3-hydroxytetradecadienoic acid (C(14:2)) were present in PHA-glc/C and PHA-glc/S, which were derived from the respective TAG, as glucose resulted in almost no C(14:)(X) monomers. The molar masses of each of the polymers remained relatively constant between 24 and 96 h. At 72 h, the number-average molar masses (M(n)) of PHA-glc/C and PHA-glc/S were 178,000 and 163,000 g/mol, respectively, which were also intermediate to the M(n) of PHA-glc (225,000 g/mol) and the respective PHA-TAG (PHA-C = 153,000 g/mol; PHA-S = 75,000 g/mol). These physical differences caused variations in the mechanical properties of mcl-PHA films, thus providing a new and effective method of modifying their properties.
authors.affiliation: United States Department of Agriculture, Agricultural Research Service, Eastern Regional Research Center, 600 E. Mermaid Lane, Wyndmoor, Pennsylvania 19038, USA. rashby@arserrc.gov
authors.forename: R D
authors.initials: RD
authors.lastname: Ashby
authors.forename: D K
authors.initials: DK
authors.lastname: Solaiman
authors.forename: T A
authors.initials: TA
authors.lastname: Foglia
authors.forename: C K
authors.initials: CK
authors.lastname: Liu
mesh_terms: D000074263:Coconut Oil; D005947:Glucose / Q000378:metabolism*; D008970:Molecular Weight; D010938:Plant Oils / Q000378:metabolism*; D011091:Polyesters / Q000737:chemistry* / Q000378:metabolism*; D011549:Pseudomonas / Q000201:enzymology / Q000378:metabolism*; D013024:Soybean Oil / Q000378:metabolism*; D013696:Temperature; D013997:Time Factors
chemical_list: D010938:Plant Oils; D011091:Polyesters; D013024:Soybean Oil; D005947:Glucose; D000074263:Coconut Oil