Characterization of a Tacky Poly(3-Hydroxyalkanoate) Produced by Pseudomonas chlororaphis HS21 from Palm Kernel Oil

Pseudomonas chlororaphis HS21 was isolated from a soil sample and found to produce medium-chain-length polyhydroxyalkanoates (MCL-PHAs) using palm kernel oil (PKO) as the sole carbon source. Up to 3.3 g/1 dry cell weight containing $45\%$ MCL-PHA was produced, when the strain was grown for 21 h in a jar fermentor culture containing 5 g/1 PKO. The polymer produced from PKO consisted of unsaturated monomers of $7.3\%$ 3-hydroxy-5-cis-tetradecenoate and $2.3\%$ 3-hydroxy-5,8,-cis, cis-tetradecadienoate as well as saturated even-carbon number monomers ranging from $C_6\;to\;C_14$, as determined by GC and El GC/MS The PHA was a transparent, sticky material at room temperature. A differential scanning calorimetric analysis revealed that the polymer was amorphous with a $-44^{\circ}C$ glass transition temperature. The number average molecular weight and polydispersity index of the PHA were 83,000 and 1.53, respectively. Although the PHA was practically biodegradable, its degradability was lower than that of poly(3-hydroxyoctanoate) based on a comp:trison of the clear zones formed by growing PHA depolymerase-producing bacteria on an agar plate containing the respective polymers.