Cloning and Expression of the PHA Synthase Gene From a Locally Isolated Chromobacterium sp. USM2

Chromobacterium sp. USM2, a locally isolated bacterium was found to synthesize poly(3-hydroxybutyrate-co-3-hydroxyvalerate), P(3HB-co-3HV) copolymer with high 3HV monomer composition. The PHA synthase gene was cloned and expressed in Cupriavidus necator PHB¯4 to investigate the possibilities of incorporating other monomer. The recombinant successfully incorporated 3-hydroxyhexanoate (3HHx) monomer when fed with crude palm kernel oil (CPKO) as the sole carbon source. Approximately 63 ± 2 wt% of P(3HB-co-3HHx) copolymer with 4 mol% of 3HHx was synthesized from 5 g/L of oil after 48 h of cultivation. In addition, P(3HB-co-3HV-co-3HHx) terpolymer with 9 mol% 3HV and 4 mol% 3HHx could be synthesized with a mixture of CPKO and sodium valerate. The presence of 3HV and 3HHx monomers in the copolymer and terpolymer was further confirmed with +H-NMR analysis. This locally isolated PHA synthase has demonstrated its ability to synthesize P(3HB-co-3HHx) copolymer from a readily available and renewable carbon source; CPKO, without the addition of 3HHx precursors

Bacterial degradation of palm olein in seawater and identification of some cultivable strains

Palm oil transported in bulk through ocean can increase pollution risks due to accidental spillage or ship collision, especially the refined, bleached and deodorized (RBD) palm olein. Bacterial degradation of RBD palm olein in seawater was investigated as a preliminary finding on palm oil degradation by marine bacteria. The degradation of RBD palm olein was evaluated in seawater in shaken-flask cultures with different oil concentrations. Biochemical oxygen demand (BOD) in the seawater was determined based on changes in dissolved oxygen (DO) values before and at end of 5-day incubation. The concentrations of major fatty acid components in RBD palm olein before and after degradation were determined using gas chromatographyflame ionization detector (GC-FID). Isolated bacteria were screened for lipolytic activity using Spirit Blue Agar before molecular identification. The DO content reduced 20% over a 5-day incubation period and BOD value was determined to be 1.24 mg O2/L based on DO values. The concentrations of fatty acids, namely palmitic acid (C16:0), stearic acid (C18:0) and oleic acid (C18:1) decreased by 53%, 31% and 37%, respectively. The bacterial count increased from 980 CFU/mL during inoculation to 1.8 x 104 CFU/mL on day 5. Five phenotypically different bacterial strains (Pseudoalteromonas gelatinolytica, Staphylococcus haemolyticus, Vibrio harveyi and Vibrio alginolyticus) showed lipolytic activity. This study indicates that marine bacteria utilizes RBD palm olein as substrate, thus degrading it over time

Optimization of growth media components for polyhydroxyalkanoate (PHA) production from organic acids by Ralstonia eutropha

We employed systematic mixture analysis to determine optimal levels of acetate, propionate, and butyrate for cell growth and polyhydroxyalkanoate (PHA) production by Ralstonia eutropha H16. Butyrate was the preferred acid for robust cell growth and high PHA production. The 3-hydroxyvalerate content in the resulting PHA depended on the proportion of propionate initially present in the growth medium. The proportion of acetate dramatically affected the final pH of the growth medium. A model was constructed using our data that predicts the effects of these acids, individually and in combination, on cell dry weight (CDW), PHA content (%CDW), PHA production, 3HV in the polymer, and final culture pH. Cell growth and PHA production improved approximately 1.5-fold over initial conditions when the proportion of butyrate was increased. Optimization of the phosphate buffer content in medium containing higher amounts of butyrate improved cell growth and PHA production more than 4-fold. The validated organic acid mixture analysis model can be used to optimize R. eutropha culture conditions, in order to meet targets for PHA production and/or polymer HV content. By modifying the growth medium made from treated industrial waste, such as palm oil mill effluent, more PHA can be produced.Malaysia. Ministry of Science, Technology and Innovation (MOSTI

Designing Novel Interfaces via Surface Functionalization of Short-Chain-Length Polyhydroxyalkanoates

Polyhydroxyalkanoates (PHA), a microbial plastic has emerged as promising biomaterial owing to the broad range of mechanical properties. However, some studies revealed that PHA is hydrophobic and has no recognition site for cell attachment and this is often a limitation in tissue engineering aspects. Owing to this, the polymer is tailored accordingly in order to enhance the biocompatibility in vivo as well as to suit the intended application. Thus far, these surface modifications have led to PHA being widely used in various biomedical and pharmaceutical applications such as cardiac patches, wound management, nerve, bone, and cartilage repair. This review addresses the surface modification on biomedical applications focusing on short-chain-length PHA such as poly(3-hydroxybutyrate) [P(3HB)], poly(3-hydroxybutyrate-co-4-hydroxybutyrate) [P(3HB-co-4HB)] and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) [P(3HB-co-3HV)]