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Shah Alam, Malaysia

Riedel S.L.,Massachusetts Institute of Technology | Bader J.,Massachusetts Institute of Technology | Bader J.,TU Berlin | Brigham C.J.,Massachusetts Institute of Technology | And 5 more authors.
Biotechnology and Bioengineering | Year: 2012

Improved production costs will accelerate commercialization of polyhydroxyalkanoate (PHA) polymer and PHA-based products. Plant oils are considered favorable feedstocks, due to their high carbon content and relatively low price compared to sugars and other refined carbon feedstocks. Different PHA production strategies were compared using a recombinant strain of Ralstonia eutropha that produces high amounts of P(HB-co-HHx) when grown on plant oils. This R. eutropha strain was grown to high cell densities using batch, extended batch, and fed batch fermentation strategies, in which PHA accumulation was triggered by nitrogen limitation. While extended batch culture produced more biomass and PHA than batch culture, fed batch cultivation was shown to produce the highest levels of biomass and PHA. The highest titer achieved was over 139g/L cell dry weight (CDW) of biomass with 74% of CDW as PHA containing 19mol% HHx. Our data suggest that the fermentation process is scalable with a space time yield (STY) better than 1 g PHA/L/h. The achieved biomass concentration and PHA yield are among the highest reported for the fermentation of recombinant R. eutropha strains producing P(HB-co-HHx). © 2011 Wiley Periodicals, Inc. Source


Yang Y.-H.,Massachusetts Institute of Technology | Yang Y.-H.,Konkuk University | Brigham C.J.,Massachusetts Institute of Technology | Budde C.F.,Massachusetts Institute of Technology | And 7 more authors.
Applied Microbiology and Biotechnology | Year: 2010

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. © 2010 Springer-Verlag. Source


Kim P.,Kyungpook National University | Kim J.,Kyungpook National University | Jung W.,Kyungpook National University | Bu S.,Research and Technology Division
Journal of Computational Physics | Year: 2016

In this paper, we develop an error embedded method based on generalized Chebyshev polynomials for solving stiff initial value problems. The solution and the error at each integration step are calculated by generalized Chebyshev polynomials of two consecutive degrees having overlapping zeros, which enables us to minimize overall computational costs. Further the errors at each integration step are embedded in the algorithm itself. In terms of concrete convergence and stability analysis, the constructed algorithm turns out to have the 6th order convergence and an almost L-stability. We assess the proposed method with several numerical results, showing that it uses larger time step sizes and is numerically more efficient. © 2015 Elsevier Inc.. Source


Koch J.D.,Marquette University | Carney J.R.,Research and Technology Division | Lightstone J.M.,Research and Technology Division | Piecuch S.R.,Research and Technology Division
AIP Conference Proceedings | Year: 2012

We demonstrate the use of a fast InGaAs array and spectrometer to measure properties related to near-infrared absorption and emission (750 nm -1500 nm) following a high explosive detonation. Using a broadband light source and a rigid absorption gauge, gas temperatures are measured at a rate of 20 kHz for a period of several milliseconds behind the blast wave from a PETN, PBXN-5, and PBXN-113 detonations. The temperature and concentration of water vapor is determined by fitting experimental transmission spectra to a simulated database. Strong emission signatures obtained during the PETN breakout event (integrated over approximately the first 20 microseconds) indicate the presence of high energy nitrogen and oxygen atoms. Measurements from water absorption at a distance of 23 cm from the PETN charge indicate temperatures decaying from 1600 K to 600 K during the first few milliseconds, and measurements of non-ideal explosives with optically thick postdetonation environments are also demonstrated. These measurements are intended to aid the development of detonation and explosive simulations. © 2012 American Institute of Physics. Source


Roberts C.W.,Research and Technology Division | Hira S.M.,Florida State University | Mason B.P.,Research and Technology Division | Strouse G.F.,Florida State University | Stoltz C.A.,Research and Technology Division
CrystEngComm | Year: 2011

Uniform crystallite morphology, narrow particle size distribution, and tailored inclusion content have been achieved for cyclotrimethylene trinitramine (RDX) explosive recrystallization by a combination of simple ultrasonic agitation and solvent evaporation, as characterized by optical imaging and confocal microscopy. © The Royal Society of Chemistry 2011. Source

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