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1.
Brian H. Davison Nhuan P. Nghiem Gerald L. Richardson 《Applied biochemistry and biotechnology》2004,114(1-3):653-669
More than 25 sorbents were tested for uptake of succinic acid from aqueous solutions. The best resins were then tested for
successive loading and regeneration using hotwater. The key desired properties for an ideal sorbent are high capacity, complete
stable regenerability, and specificity for the product. The best resins have a stable capacity of about 0.06 g of succinic
acid/g of resin at moderate concentrations (1–5 g/L) of succinic acid. Several sorbents were tested more exhaustively for
uptake of succinic acid and for successive loading and regeneration using hot water. One resin, XUS 40285, has a good stable
isotherm capacity, prefers succinate over glucose, and has good capacities at both acidic and neutral pH. Succinic acid was
removed from simulated media containing salts, succinic acid, acetic acid, and sugar using a packed column of sorbent resin,
XUS 40285. The fermentation byproduct, acetate, was completely separated from succinate. A simple hot water regeneration successfully
concentrated succinate from 10 g/L (inlet) to 40–110 g/L in the effluent. If successful, this would lower separation costs
by reducing the need for chemicals for the initial purification step. Despie promising initial results of good capacity (0.06
g of succinic/g of sorbent), 70% recovery using hot water, and a recovered concentration of >100 g/L, this regeneration was
not stable over 10 cycles in the column. Alternative regeneration schemes using acid and base were examined. Two (XUS 40285
and XFS-40422) showed both good stable capacities for succinic acid over 10 cycles and >95% recovery in a batch operation
using a modified extraction procedure combining acid and hot water washes. These resins showed comparable results with actual
broth. 相似文献
2.
Bharathi Avula Babu L. Tekwani Narayan D. Chaurasiya NP Dhammika Nanayakkara Yan‐Hong Wang Shabana I. Khan Vijender R. Adelli Rajnish Sahu Mahmoud A. Elsohly James D. McChesney Ikhlas A. Khan Larry A. Walker 《Journal of mass spectrometry : JMS》2013,48(2):276-285
Therapeutic efficiency and hemolytic toxicity of primaquine (PQ), the only drug available for radical cure of relapsing vivax malaria are believed to be mediated by its metabolites. However, identification of these metabolites has remained a major challenge apparently due to low quantities and their reactive nature. Drug candidates labeled with stable isotopes afford convenient tools for tracking drug‐derived metabolites in complex matrices by liquid chromatography‐tandem mass spectrometry (LC‐MS‐MS) and filtering for masses with twin peaks attributable to the label. This study was undertaken to identify metabolites of PQ from an in vitro incubation of a 1:1 w/w mixture of 13C6‐PQ/PQ with primary human hepatocytes. Acquity ultra‐performance LC (UHPLC) was integrated with QTOF‐MS to combine the efficiency of separation with high sensitivity, selectivity of detection and accurate mass determination. UHPLC retention time, twin mass peaks with difference of 6 (originating from 13C6‐PQ/PQ), and MS‐MS fragmentation pattern were used for phenotyping. Besides carboxy‐PQ (cPQ), formed by oxidative deamination of PQ to an aldehyde and subsequent oxidation, several other metabolites were identified: including PQ alcohol, predictably generated by oxidative deamination of PQ to an aldehyde and subsequent reduction, its acetate and the alcohol's glucuronide conjugate. Trace amounts of quinone‐imine metabolites of PQ and cPQ were also detected which may be generated by hydroxylation of the PQ/cPQ quinoline ring at the 5‐position and subsequent oxidation. These findings shed additional light on the human hepatic metabolism of PQ, and the method can be applied for identification of reactive PQ metabolites generated in vivo in preclinical and clinical studies. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
3.
Applied Biochemistry and Biotechnology - 相似文献
4.
Nghiem Nhuan P. Davison Brian H. Thompson James E. Suttle Bruce E. Richardson Gerald R. 《Applied biochemistry and biotechnology》1996,57(1):633-638
Applied Biochemistry and Biotechnology - The effect of biotin at 50 mg/L on the production of succinic acid byA. succiniciproducens has been studied. Biotin improved glucose consumption, cell... 相似文献
5.
Nhuan P. Nghiem Kevin B. Hicks David B. Johnston 《Applied biochemistry and biotechnology》2010,162(7):1915-1928
Production of succinic acid from glucose by Escherichia coli strain AFP184 was studied in a batch fermentor. The bases used for pH control included NaOH, KOH, NH4OH, and Na2CO3. The yield of succinic acid without and with carbon dioxide supplied by an adjacent ethanol fermentor using either corn or
barley as feedstock was examined. The carbon dioxide gas from the ethanol fermentor was sparged directly into the liquid media
in the succinic acid fermentor without any pretreatment. Without the CO2 supplement, the highest succinic acid yield was observed with Na2CO3, followed by NH4OH, and lowest with the other two bases. When the CO2 produced in the ethanol fermentation was sparged into the media in the succinic acid fermentor, no improvement of succinic
acid yield was observed with Na2CO3. However, several-fold increases in succinic acid yield were observed with the other bases, with NH4OH giving the highest yield increase. The yield of succinic acid with CO2 supplement from the ethanol fermentor when NH4OH was used for pH control was equal to that obtained when Na2CO3 was used, with or without CO2 supplementation. The benefit of sparging CO2 from ethanol fermentation on the yield of succinic acid demonstrated the feasibility of integration of succinic acid fermentation
with ethanol fermentation in a biorefinery for production of fuels and industrial chemicals. 相似文献
6.
7.
Sun May Y. Nghiem Nhuan P. Davison Brian H. Webb Oren F. Bienkowski Paul R. 《Applied biochemistry and biotechnology》1998,(1):429-439
The production of ethanol from starch was studied in a fluidized-bed reactor (FBR) using co-immobilizedZymomonas mobilis and glucoamylase. The FBR was a glass column of 2.54 cm in diameter and 120 cm in length. TheZ. mobilis and glucoamylase were co-immobilized within small uniform beads (1.2-2.5 mm diameter) of κ-carrageenan. The substrate for
ethanol production was a soluble starch. Light steep water was used as the complex nutrient source. The experiments were performed
at 35κC and pH range of 4.0-5.5. The substrate concentrations ranged from 40 to 185 g/L, and the feed rates from 10 to 37
mL/min. Under relaxed sterility conditions, the FBR was successfully operated for a period of 22 d, during which no contamination
or structural failure of the biocatalyst beads was observed. Volumetric productivity as high as 38 g ethanol/(Lh), which was
74% of the maximum expected value, was obtained. Typical ethanol volumetric productivity was in the range of 15-20 g/(Lh).
The average yield was 0.49 g ethanol/g substrate consumed, which was 90% of the theoretical yield. Very low levels of glucose
were observed in the reactor, indicating that starch hydrolysis was the rate-limiting step. 相似文献
8.
Brian H. Davison Sadie R. Drescher Gerald A. Tuskan Mark F. Davis Nhuan P. Nghiem 《Applied biochemistry and biotechnology》2006,130(1-3):427-435
Wood samples from second generation Populus cross were shown to have different lignin contents and S/G ratios (S: syringyl-like lignin structures; G: guaiacyl-like lignin
structures). The lignin contents varied from 22.7% to 25.8% and the S/G ratio from 1.8 to 2.3. Selected samples spanning these
ranges were hydrolyzed with dilute (1%) sulfuric acid to release fermentable sugars. The conditions were chosen for partial
hydrolysis of the hemicellulosic fraction to maximize the expression of variation among samples. The results indicated that
both lignin contents and S/G ratio significantly affected the yield of xylose. For example, the xylose yield of the 25.8%
lignin and 2.3 S/G (hihg lignin, high S/G) sample produced 30% of the theoretical yield, whereas the xylose yield of the 22.7%
lignin and 1.8 S/G (low lignin, low S/G) was 55% of the theoretical value. These results indicate that lignin content and
composition among genetic variants within a single species can influence the hydrolyzability of the biomass. 相似文献
9.
Quoc Dat Nghiem Chi Thanh Nguyen Dong‐Pyo Kim 《Journal of polymer science. Part A, Polymer chemistry》2008,46(13):4594-4601
High molecular weight poly(vinyl)silazane were synthesized successfully by reversible addition fragmentation chain transfer (RAFT) polymerization in toluene at 120 °C, using dithiocarbamate derivatives and 2,2′‐azobis‐isobutyrylnitrile (AIBN) as the RAFT agents and thermal initiator, respectively. The polymerization of a vinylcyclicsilazane oligomer with 82.5% conversion was readily controlled to increase the molecular weight from 1000 to 12,000 g/mol with a narrow polydispersity <1.5. The resulting polymer showed a high ceramic yield of 70 wt % at 1000 °C. Moreover, the approach was extended successfully to the synthesis of poly(vinyl)silazane‐block‐polystyrene as an inorganic–organic diblock copolymer. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 4594–4601, 2008 相似文献
10.
Krishnan Mahesh S. Blanco Maria Shattuck Christopher K. Nghiem Nhuan P. Davison Brian H. 《Applied biochemistry and biotechnology》2000,84(1-9):525-541
Fermentation of glucose-xylose mixtures to ethanol was investigated in batch and continuous experiments using immobilized
recombinant Zymomonas mobilis CP4(pZB5). This microorganism was immobilized by entrapment in κ-carrageenan beads having a diameter of 1.5–2.5 mm. Batch
experiments showed that the immobilized cells cofermented glucose and xylose to ethanol and that the presence of glucose improved
the xylose utilization rate. Batch fermentation of rice straw hydrolysate containing 76 g/L of glucose and 33.8 g/L of xylose
gave an ethanol concentration of 44.3 g/L after 24 h, corresponding to a yield of 0.46 g of ethanol/g of sugars. Comparable
results were achieved with a synthetic sugar control. Continuous fermentation experiments were performed in a laboratory-scale
fluidized-bed bioreactor (FBR). Glucose-xylose feed mixtures were pumped through the FBR at residence times of 2–4 h. Glucose
conversion to ethanol was maintained above 98% in all experiments. Xylose conversion to ethanol was highest at 91.5% for a
feed containing 50 g/L of glucose and 13 g/L of xylose at a dilution rate of 0.24/h. The xylose conversion to ethanol decreased
with increasing feed xylose concentration, dilution rate, and age of the immobilized cells. Volumetric ethanol productivities
in the range of 6.5–15.3 g/L·h were obtained. The improved productivities achieved in the FBR compared to other bioreactor
systems can help in reducing the production costs of fuel ethanol from lignocellulosic sugars.
This article has been authored by a contractor of the US go vernment under contract DE-AC05-96OR22464. Accordingly, the US
government retains a nonexclusive, royaltyfree license to publish or reproduce the published form of the contribution, or
allow others to do so, for US government purposes. 相似文献