2,733 research outputs found
Desulfurization of light gas oil in immobilized-cell systems of Gordona sp CYKS1 and Nocardia sp CYKS2
No full textDesulfurizations of a model oil (hexadecane containing dibenzothiophene (DBT)) and a diesel oil by immobilized DBT-desulfurizing bacterial strains, Gordona sp. CYKS1 and Nocardia sp. CYKS2, were carried out. Celite bead was used as a biosupport for cell immobilization. Seven-eight cycles of repeated-batch desulfurization were conducted for each strain. Each batch reaction was carried out for 24 h. In the case of model oil treatment with strain CYKS1, about 4.0 mM of DBT in hexadecane (0.13 g sulfur l(oil)(-1)) was desulfurized during the first batch, while 0.25 g sulfur l(oil)(-1) during the final eighth batch. The mean desulfurization rate increased from 0.24 for the first batch to 0.48 mg sulfur l(dispersion)(-1) h(-1) for the final batch. The sulfur content in the light gas oil was decreased from 3 to 2.1 g l(oil)(-1) by strain CYKS1 in the first batch. The mean desulfurization rate was 1.81 mg sulfur l(dispersion)(-1) h(-1), which decreased slightly when the batch reaction was repealed. No significant changes in desulfurization rate were observed with strain CYKS2 when the batch reaction was repeated. When the immobilized cells were stored at 4 degrees C in 0.1 M phosphate buffer (pH 7.0) for 10 days, the residual desulfurization activity was about 50 similar to 70% of the initial value. (C) 2000 Published by Elsevier Science B.V. All rights reserved
Comparison and optimization of poly(3-hydroxybutyrate) recovery from Alcaligenes eutrophus and recombinant Escherichia coli
No full textThe recovery of poly(3-hydroxybutyrate) [PHB] from Alcaligenes eutrophus and a recombinant Escherichia coli strain harboring the A. eutrophus poly(3-hydroxyalkanoates) biosynthesis genes was studied. When PHB was recovered using sodium hypochlorite or sodium dodecyl sulfate (SDS), non-PHB cell materials (NPCM) of the recombinant E. coil seemed to be more easily digested than those of A. eutrophus. Furthermore, viscosity increase caused by cell lysis during SDS treatment was negligible for the recombinant E. coli, whereas a very viscous suspension was formed for A. eutrophus. These results, together with our previous finding that PHB in the recombinant E. coli is far less susceptible to molecular degradation by sodium hypochlorite, suggested that the recombinant E. coli was more beneficial than A. eutrophus in terms of PHB recovery. In order to develop an easy and efficient recovery process, we adopted and optimized the SDS treatment since, with the hypochlorite treatment, we could not handle high biomass concentrations effectively. We could obtain a PHB of 95 % purity with 96 % recovery under the optimal condition of a biomass concentration of 5 %, a ratio of SDS to biomass of 0.6, a treatment time of 60 minutes, and a treatment temperature of 30 degrees C
Application of a Coagulant for Recovery of Poly(3-Hydroxybutyric Acid) Synthesized in Alcaligenes eutrophus
No full textAssessments of chronodispersion and tacheodispersion of F-waves in patients with spinal cord injury.
No full textGAS HOLDUP AND MASS-TRANSFER CHARACTERISTICS OF CARBOXYMETHYL CELLULOSE SOLUTIONS IN A BUBBLE COLUMN WITH A RADIAL GAS SPARGER
No full textThe gas phase holdup and mass transfer characteristics of carboxymethyl cellulose (CMC) solutions in a bubble column having a radial gas sparger have been determined and a new flow regime map has been proposed. The gas holdup increases with gas velocity in the bubbly flow regime, decreases in the churn-turbulent flow regime, and increases again in the slug flow regime. The volumetric mass transfer coefficient (k(L)a) significantly decreases with increasing liquid viscosity. The gas holdup and k(L)a values in the present bubble column of CMC solutions are found to be much higher than those in bubble columns or external-loop airlift columns with a plate-type sparger. The obtained gas phase holdup (epsilon(g)) and k(L)a data have been correlated with pertinent dimensionless groups in both the bubbly and the chum-turbulent flow regimes.Ministry of Science and Technology of Korea, Bioprocess Engineering Research Cente
Spatial control of cellular adhesion using photo-crosslinked micropatterned polyelectrolyte multilayer films
No full textThe entrapment syndrome of the intermediate dorsal cutaneous branch of the superficial peroneal nerve:
No full textA physiological study on growth and dibenzothiophene (DBT) desulfurization characteristics of Gordonia sp CYKS1
No full textPhysiological characteristics of DBT desulfurization and cell growth of Gordonia sp. CYKS1 were investigated. It exhibited a preference to ethanol in a medium containing two carbon sources, ethanol and one of the carbohydrates used, glucose, sucrose, maltose, and galactose although it consumed both carbon sources simultaneously. Cell growth on ethanol or glucose followed the Monod kinetics. The optimal range of pH for the desulfurization of DBT and the cell growth was 7 to 8. The desulfurization rate decreased about 30% at pH 6, and no significant desulfurization or cell growth was observed at pH 5. As the initial DBT concentration increased up to 1.5 mM, the desulfurization rate also increased while no significant changes in the growth rate were observed. The maximum desulfurization rate was 12.50 mumol L-1 h(-1) at an initial DBT concentration of 1.5 mM. Cell growth and desulfurization activity were severely inhibited by the presence of 2-hydroxybiphenyl (2-HBP). When 0.05 mM of 2-HBP was added at the beginning, both of the desulfurization rate and cell growth rate decreased about 20%. It was found that cell growth and desulfurization were completely inhibited in the presence of 2-HBP at 0.15 mM or a higher concentration. The inhibition by 2,2'-dihydroxybiphenyl (DHBP) was less severe than 2-HBP. About 80% of desulfurization activity was retained in the presence of 2,2'-DHBP at 0.4 mM
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