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Aziz N.A.,Universiti Sains Malaysia | Sipaut C.S.,Universiti Malaysia Sabah | Abdullah A.A.-A.,Universiti Sains Malaysia | Abdullah A.A.-A.,MOSTI Inc
Journal of Chemical Technology and Biotechnology | Year: 2012

BACKGROUND: The aim of this work is to enhance the production of terpolyester poly(3-hydroxybutyrate-co-3-hydroxyvalerate-co-4-hydroxybutyrate) (P(3HB-co-3HV-co-4HB)) produced by a locally isolated bacterium, Cupriavidus sp. USMAA2-4. The monomer composition was varied by supplementing different carbon precursors and by manipulating the culture condition through one-stage cultivation. The effect of C/N ratio and different concentrations of carbon source and precursors were investigated in order to produce higher content of this terpolyester. Although research on this biodegradable polyester is abundant, studies on terpolyester P(3HB-co-3HV-co-4HB) are still limited. RESULTS: Supplementation of oleic acid in accumulation medium increased the bacterial growth and polyhydroxyalkanoate (PHA) accumulation. It was also shown that medium consisting of assorted carbon precursors at C/N 20 gave relatively high dry cell weight and P(3HB-co-3HV-co-4HB) content. Various compositions of terpolyester were obtained when the concentration of oleic acid and 4HB precursors were manipulated. The combination of oleic acid with γ-butyrolactone and 1-pentanol was found to be the best combination to produce high PHA content (81 wt%). The composition of monomer in P(3HB-co-3HV-co-4HB) was produced in the range 8-13 mol% for 3HV and 9-24 mol% for 4HB, respectively. CONCLUSIONS: The production of P(3HB-co-3HV-co-4HB) in shake-flasks successfully produced 81 wt% of PHA content. This manipulated culture condition can be used at larger scale to provide modeling for the production of terpolyester in a bioreactor. © 2012 Society of Chemical Industry.

Maskin M.,Malaysian Nuclear Agency | Tom P.P.,Malaysian Nuclear Agency | Lanyau T.A.,Malaysian Nuclear Agency | Brayon F.C.M.,MOSTI Inc | And 4 more authors.
AIP Conference Proceedings | Year: 2014

As a consequence of the accident at the Fukushima Dai-ichi Nuclear Power Plant in Japan, the safety aspects of the one and only research reactor (31 years old) in Malaysia need be reviewed. Based on this decision, Malaysian Nuclear Agency in collaboration with Atomic Energy Licensing Board and Universiti Kebangsaan Malaysia develop a Level-1 Probability Safety Assessment on this research reactor. This work is aimed to evaluate the potential risks of incidents in RTP and at the same time to identify internal and external hazard that may cause any extreme initiating events. This report documents the methodology in developing a Level 1 PSA performed for the RTP as a complementary approach to deterministic safety analysis both in neutronics and thermal hydraulics. This Level-1 PSA work has been performed according to the procedures suggested in relevant IAEA publications and at the same time numbers of procedures has been developed as part of an Integrated Management System programme implemented in Nuclear Malaysia. © 2014 AIP Publishing LLC.

Ansari N.F.,Universiti Sains Malaysia | Amirul A.A.,Universiti Sains Malaysia | Amirul A.A.,MOSTI Inc
Applied Biochemistry and Biotechnology | Year: 2013

Polyhydroxyalkanoates (PHAs) are hydrophobic biodegradable thermoplastics that have received considerable attention in biomedical applications due to their biocompatibility, mechanical properties, and biodegradability. In this study, the degradation rate was regulated by optimizing the interaction of parameters that influence the enzymatic degradation of P(3HB) film using response surface methodology (RSM). The RSM model was experimentally validated yielding a maximum 21 % weight loss, which represents onefold increment in percentage weight loss in comparison with the conventional method. By using the optimized condition, the enzymatic degradation by an extracellular PHA depolymerase from Acidovorax sp. DP5 was studied at 37 C and pH 9.0 on different types of PHA films with various monomer compositions. Surface modification of scaffold was employed using enzymatic technique to create highly porous scaffold with a large surface to volume ratio, which makes them attractive as potential tissue scaffold in biomedical field. Scanning electron microscopy revealed that the surface of salt-leached films was more porous compared with the solvent-cast films, and hence, increased the degradation rate of salt-leached films. Apparently, enzymatic degradation behaviors of PHA films were determined by several factors such as monomer composition, crystallinity, molecular weight, porosity, and roughness of the surface. The hydrophilicity and water uptake of degraded salt-leached film of P(3HB-co-70%4HB) were enhanced by incorporating chitosan or alginate. Salt-leached technique followed by partial enzymatic degradation would enhance the cell attachment and suitable for biomedical as a scaffold. © 2013 Springer Science+Business Media New York.

Muzaiyanah A.R.,Universiti Sains Malaysia | Amirul A.A.,Universiti Sains Malaysia | Amirul A.A.,MOSTI Inc
Applied Biochemistry and Biotechnology | Year: 2013

In this study, the ability of Cupriavidus sp. USMAA2-4 to synthesize polyhydroxyalkanoates (PHA) containing 4-hydroxyvalerate monomer (4HV) was studied through one-stage cultivation using γ-valerolactone as the carbon precursor. The presence of 4HV monomer unit in the polymer was detected through gas chromatography analysis, proving the capability of this wild strain bacterium to produce poly(3-hydrxybutyrate-co-3-hydroxyvalerate-co-4- hydroxyvalerate) [P(3HB-co-3HV-co-4HV)] terpolymer. Existence of a 4HV monomer unit in the PHA produced was further confirmed through 13C and 1H NMR analysis. P(3HB-co-88 % 3HV-co-1 % 4HV) terpolymer with the highest PHA content of 63 wt% was obtained through combination of 0.14 wt% C of γ-valerolactone with 0.42 wt% C of oleic acid. Various compositions of P(3HB-co-3HV-co-4HV) terpolymer with 3HV and 4HV compositions ranging from 11 to 94 mol% and from 1 to 4 mol%, respectively, were acquired by manipulating γ-valerolactone and oleic acid concentrations. The molecular weight and the thermal and mechanical properties of four different compositions of terpolymers - P(3HB-co-91 % 3HV-co-1 % 4HV), P(3HB-co-55 % 3HV-co-2 % 4HV), P(3HB-co-27 % 3HV-co-2 % 4HV), and P(3HB-co-9 % 3HV-co-1 % 4HV) - were characterized. Among these terpolymers, P(3HB-co-27 % 3HV-co-2 % 4HV) terpolymer with a molecular weight of 5.7 (105 Da) exhibited the highest elongation to break (264 %). The monomer unit compositional distributions of these terpolymers were investigated through acetone-water fractionation analysis. The results suggested that these produced terpolymers had broad 3HV compositional distribution and narrow 4HV compositional distribution. © 2013 Springer Science+Business Media New York.

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