Submitted to: Bio Environmental Polymer Society
Publication Type: Abstract Only
Publication Acceptance Date: 3/1/2002
Publication Date: 5/1/2002
Citation: Ashby, R.D., Solaiman, D., Foglia, T.A. 2002. Molar mass regulation of poly(3-hydroxybutyrate) and medium-chain-length poly(hydroxyalkanoates) through variation in glycerol media concentration [abstract]. Bio Environmental Polymer Society. Poster 10.
Technical Abstract: Poly(hydroxyalkanoates) (PHAs) are biological polyesters that have been classified as either short-chain-length PHA (scl-PHA; crystalline thermoplastics) or medium-chain-length PHA (mcl-PHA; amorphous elastomers) depending on the length of their side-chain constituents. Altering the physical properties (either composition or molar mass) of these PHA polymers provides a means by which their material properties can be manipulated to suit certain applications. Molar mass control of both scl- and mcl-PHA has been established by addition of poly(ethylene glycol) (PEG) to fermentation media prior to inoculation. In this study, we determined that the molar masses of both scl-PHA and mcl-PHA derived from 2 different species of Pseudomonas could be controlled by glycerol media concentration while having no effect on the compositions of the polymers. In fact, the molar mass of PHB produced by P. oleovorans NRRL B-14682 decreased by 59% and 62% at 48 hours and 72 hours incubation time, respectively between 1% and 5% glycerol media concentration. In contrast, the mcl-PHA from P. corrugata 388 decreased by 55% at 48 hours incubation time between 1% and 3% glycerol media concentration, while at 72 hours incubation time the molar mass decreased by 73% between 1% and 5% glycerol media concentrations. In addition, it was found that glycerol was utilized by each bacterial strain at a relatively constant rate regardless of the initial glycerol media concentration. In fact P. oleovorans NRRL B-14682 utilized glycerol at an average rate of 9.1 mg/dL/h up to 48 hours after which that rate increased to an average of 17.3 mg/dL/h between 48 and 72 hours. In contrast, P. corrugata 388 utilized glycerol twice as fast initially (21.0 mg/dL/h) up to 48 hours after which the rate of glycerol utilization dropped slightly to 19.7 mg/dL/h to 72 hours. The ability to control the PHA molar masses simply by varying carbon source concentration provides a less expensive means by which the physical and mechanical properties of the polymers can be controlled.