Submitted to: Bio Environmental Polymer Society
Publication Type: Abstract only
Publication Acceptance Date: 6/1/2003
Publication Date: 8/1/2003
Citation: Ashby, R.D., Solaiman, D., Foglia, T.A. 2003. Coproducts of biodiesel production as a source of bacterial poly(hydroxyalkanoates) [abstract]. BioEnvironmental Polymer Society. Abstract No. 2. Interpretive Summary:
Technical Abstract: Poly(hydroxyalkanoates) (PHAs) are biodegradable bacterial polyesters that have been classified as either short-chain- (scl-PHA) or medium-chain- (mcl-PHA) depending on the length of their side-chain constituents. Because of their wide-ranging properties (thermoplastics to elastomers), PHAs are currently being studied as potential replacements for many petroleum-based polymers. At present, the major drawback to commercialization of these polymers is their cost of production. In our ongoing attempt to lower PHA production costs, we have turned to the use of coproducts as substrates for the bacterial production of PHA. Biodiesel is an alternative fuel that burns cleaner than petrodiesel. It is synthesized through the chemical or enzymatic conversion of triacylglycerols to fatty acid methyl esters. This conversion results in large amounts of glycerol, which is a potential low cost substrate for PHA production. In this study, a biodiesel coproduct stream was analyzed and determined to contain 40% glycerol, 34% unreacted free fatty acids or unrecovered fatty acid methyl esters, and 26% water. By using this material as substrate for PHA production, we successfully synthesized scl-PHA (poly 3-hydroxybutyrate; PHB) and mcl-PHA from Pseudomonas oleovorans NRRL B-14682 and P. corrugata 388, respectively. In shake flask culture, the maximum cell productivities were 20±5% of the cell dry weight (CDW) for the PHB produced by P. oleovorans and 28±2% of the CDW for the mcl-PHA synthesized by P. corrugata. The mcl-PHA from P. corrugata was primarily composed of 3-hydroxyoctanoic acid (C8:0, 38%), 3-hydroxydecanoic acid (C10:0, 27%), and 3-hydroxytetradecadienoic acid (C14:2, 16%). The large amount of C14:2 reflected the fact that the biodiesel coproduct stream was the result of biodiesel synthesis from soybean oil which is high in linoleic acid. The ability to produce both scl-PHA and mcl-PHA from the biodiesel coproduct stream may help in providing an outlet for these materials as well as lowering the cost of PHA production.