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Kazuyuki Shimizu,Nor Aini Abdul Rahman,Yoshihito Shirai,Mohd Ali Hassan 한국생물공학회 2002 Biotechnology and Bioprocess Engineering Vol.7 No.5
Recombinant Escherichia coli strain harboring the lpR-pL promotor and heterologus poly-b-hydroxybutyrate (PHB) biosynthesis genes was used to investigate the effect of culture conditions on the efficient PHB production. The expression of phb genes was induced by a temperature upshift from 33°C to 38°C. The protein expression levels were measured by using two-dimensional electrophoresis, and the enzyme activities were also measured to understand the effect of culture temperature, carbon sources, and the dissolved oxygen (DO) concentration on the metabolic regulations. AcetylCoA is an important branch point for PHB production. The decrease in DO concentration lowers the citrate synthase activity, thus limit the flux toward the TCA cycle, and increase the flux for PHB production. Since NADPH is required for PHB production, the PHB production does not continue leading the overproduction of acetate and lactate. Based on these observations, a new operation was considered where DO concentration was changed periodically, and it was verified its usefulness for the efficient PHB production by experiments.
( Isamu Maeda ),( Hirokazu Sakurai ),( Kazuyuki Yoshida ),( Mohammad Shohel Rana Siddiki ),( Tokuo Shimizu ),( Motohiro Fukami ),( Shunsaku Ueda ) 한국미생물 · 생명공학회 2011 Journal of microbiology and biotechnology Vol.21 No.12
Recombinant Rhodopseudomonas palustris, harboring the carotenoid-metabolizing gene crtI (CrtIBS), and whose color changes from greenish yellow to red in response to inorganic As(III), was cultured in transparent microplate wells illuminated with a light emitting diode (LED) array. The cells were seen to grow better under near-infrared light, when compared with cells illuminated with blue or green LEDs. The absorbance ratio of 525 to 425 nm after cultivation for 24 h, which reflects red carotenoid accumulation, increased with an increase in As(III) concentrations. The detection limit of cultures illuminated with near-infrared LED was 5 μg/l, which was equivalent to that of cultures in test tubes illuminated with an incandescent lamp. A near-infrared LED array, in combination with a microplate, enabled the simultaneous handling of multiple cultures, including CrtIBS and a control strain, for normalization by the illumination of those with equal photon flux densities. Thus, the introduction of a near-infrared LED array to the assay is advantageous for the monitoring of arsenic in natural water samples that may contain a number of unknown factors and, therefore, need normalization of the reporter event.
Abdul Rahman, Nor Aini,Shirai, Yoshihito,Shimizu, Kazuyuki,Hassan, Mohd Ali The Korean Society for Biotechnology and Bioengine 2002 Biotechnology and Bioprocess Engineering Vol.7 No.5
Recombinant Escherichia coli strain harboring the ${\lambda}$pR-pL promotor and heterologus poly-${\beta}$-hydroxybutyrate (PHB) biosynthesis genes was used to investigate the effect of culture conditions on the efficient PHB production. The expression of phb genes was induced by a temperature upshift from $33^{\circ}C\;to\;38^{\circ}C$. The protein expression levels were measured by using two-dimensional electrophoresis, and the enzyme activities were also measured to understand the effect of culture temperature, carbon sources, and the dissolved oxygen (DO) concentration on the metabolic regulations. AcetylCoA is an important branch point for PHB production. The decrease in DO concentration lowers the citrate synthase activity, thus limit the flux toward the TCA cycle, and increase the flux for PHB production. Since NADPH is required for PHB production, the PHB production does not continue leading the overproduction of acetate and lac-tate. Based on these observations, a new operation was considered where DO concentration was changed periodically, and it was verified its usefulness for the efficient PHB production by experiments.
Masahito Taya,Motomu Nishioka,Hajime Nishiuma,Masato Miyake,Yasuo Asada,Kazuyuki Shimizu 한국생물공학회 2002 Biotechnology and Bioprocess Engineering Vol.7 No.5
To understand the utilization property of light energy, Synechococcus sp. MA19, a poly-b-hydroxybutyrate (PHB) producer, was cultivated at the different incident light intensities of 15.3, 50.0 and 78.2 W/m2 using media with and without phosphate. From the results of metabolic flux analysis, it was found that the cell yield based on ATP synthesis was estimated as 3.5×10-3 kg-biomass/mol-ATP in these cultures. Under the examined conditions, there were no significant differences in the efficiency of light energy conversion to chemical energies estimated as ATP synthesis and reducing potential (NADH + NADPH) formation whether the PHB synthesis took place or not. The energy converted from light to ATP was kept relatively high around the energy absorbed by the cells of 2.5-3.0 x 106 J h-1 kg-1, whereas the energy of reducing potential was hardly changed in the examined range of the energy absorbed by the cells.
Nishioka, Motomu,Nishiuma, Hajime,Miyake, Masato,Asada, Yasuo,Shimizu, Kazuyuki,Taya, Masahito The Korean Society for Biotechnology and Bioengine 2002 Biotechnology and Bioprocess Engineering Vol.7 No.5
To understand the utilization property of light energy, Synechococcus sp. MA19, a poly-${\beta}$-hydroxybutyrate (PHB) producer, was cultivated at the different incident light intensities of 15.3, 50.0 and 78.2 W/$m^2$ using media with and without phosphate. From the results of metabolic flux analysis, it was found that the cell yield based on ATP synthesis was estimated as $3.5{\times}10^{-3}$ kg-biomass/mol-ATP in these cultures. Under the examined conditions, there were no significant differences in the efficiency of light energy conversion to chemical energies estimated as ATP synthesis and reducing potential (NADH + NADPH) formation whether the PHB synthesis took place or not. The energy converted from light to ATP was kept relatively high around the energy absorbed by the cells of $2.5-3.0{\times}10^{6} J\;h^{-1}\;kg^{-1}$, whereas the energy of reducing potential was hardly changed in the examined range of the energy absorbed by the cells.