, Volume 49, Issue 4, pp 431-437

Poly(hydroxyalkanoate) biosynthesis from triglyceride substrates

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Abstract

The biosynthesis of poly(hydroxyalkanoates) (PHA) by Pseudomonas resinovorans from triglyceride substrates was investigated. Each triglyceride, whether animal fat or vegetable oil, supported cellular growth to relatively high average cell yields (3.3 ± 0.2 g/l). PHA yields ranged from 1.1 g/l to 2.1 g/l, representing approximately 45% of the bacterial cell dry weight. The repeat-unit composition of the polymers was determined by gas chromatography (GC) and GC/mass spectrometry of the β-hydroxyalkanoate methyl esters from the hydrolyzed polymers. With the exception of PHA from soybean oil (PHA-soy), each polyester was composed of β-hydroxyacyl moieties with chain lengths ranging from C4 to C14, with C8 and C10 being the predominant species. PHA-soy contained an additional fraction (2%) of C16 monomers. The alkyl side-chains of the PHA contained varying degrees of unsaturation. PHA from coconut oil was composed entirely of saturated side-chains, whereas PHA-soy contained 4.2 mol% olefinic groups in its side-chains. The increase in the degree of side-chain unsaturation caused decreased melting temperatures, enthalpies of fusion, and glass transition temperatures. The molar masses of the polymers were relatively constant and ranged from 6.5 × 104 to 10.1 × 104 g/mol.

Received: 2 September 1997 / Received revision: 21 November 1997 / Accepted: 2 January 1998