1,720,977 research outputs found
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
GAS 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
Application of a Coagulant for Recovery of Poly(3-Hydroxybutyric Acid) Synthesized in Alcaligenes eutrophus
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Recovery of poly(3-hydroxybutyrate) from coagulated Ralstonia eutropha using a chemical digestion method
No full textFor economic recovery of poly(3-hydroxybutyrate) (PHB) from culture broths of Ralstonia eutropha containing PHB, Al-based and Fe-based coagulants were used in the pretreatment step. The coagulated cells were then separated by centrifugation, and PHB was extracted by chemical digestion with a sodium hypochlorite/chloroform dispersion solution. The practical upper limits of dosage were found to be 1,500 mg-Al/L and 1,000 mg-Fe/L, respectively, for Al- and Fe-based coagulants. When the harvested cells were treated with a 50% sodium hypochlorite/chloroform dispersion solution, PHB recovery and purity were 90-94% and 98-99%, respectively. The influence of the use of coagulants on the PHB recovery process was found to be insignificant. Despite the residual Al and Fe in the recovered PHB (less than 450 mg-Al/kg-PHB and 750 mg-Fe/kg-PHB, respectively), no detectable amounts of Al and Fe were leached from films made of the recovered PHB under acidic conditions. The use of Fe-based coagulants is less recommended because the Fe impurity can cause an unwanted colorization problem in the final product
Separation of Alcaligenes eutrophus cells containing poly(3-hydroxybutyrate) from fermentation broth with pretreatment using Al- and Fe-based coagulants
No full textAlcaligenes eutrophus containing intracellular poly(3-hydroxybutyrate) was recovered from fermentation broth by centrifugation and filtration after pretreatment with Aland Fe-based coagulants. Coagulation efficiency was largely affected by pH, and the optimum pH's for cell recovery were about 4.6-5.6 for the Al-based coagulants and about 5-8 for the Fe-based coagulants. Ammonium ions that combined with metals to form complex compounds increased the coagulant requirement, and the additional requirement of coagulant was found to be proportional to the ammonium concentration. In addition, various ligands in addition to ammonium lolls contained in the culture medium interfered with the coagulation reaction and increased the coagulant requirement also. The coagulant requirement increased with the cell concentration regardless of coagulant type. The polymeric coagulants such as PACS, Hi-PAX and Ferix-3 were more effective than nonpolymeric coagulants of aluminum sulfate and ferrous sulfate. The optimum dosages of the coagulants tested were determined over a broad range of cell concentration of 20.5-210 g/L. It was observed that the energy requirement for centrifugation could be greatly reduced with cell coagulation
Development of an optimal medium for continuous ferrous iron oxidation by immobilized Acidothiobacillus ferrooxidans cells
No full textThis study was aimed at developing an immobilized bioreactor system in which long-term continuous ferrous iron oxidation can be realized with no formation of jarosite, which causes clogging of support pores and reactor lines. For this purpose, a medium with no jarosite formation was developed first by selecting optimal nitrogen and phosphate sources and their concentrations. Then with the developed medium containing ammonium phosphate instead of ammonium sulfate and potassium phosphate, repeated batch and continuous operations of ferrous iron oxidation by Acidothiobacillus ferrooxidans cells immobilized in a depth filter were successfully performed for an extended period of time. For about 510 h of operation including 450 h of continuous operation at dilution rates of 0.1, 0.2, and 0.3 h(-1), no formation of jarosite and thus no clogging of the reactor system were observed. The maximum ferrous iron oxidation rate was as high as 2.6 g/(L(.)h) at a dilution rate of 0.3 h(-1)
Enhancement of phase separation by the addition of de-emulsifiers to three-phase (diesel oil/biocatalyst/aqueous phase) emulsion in diesel biodesulfurization
No full textEthanol, added as a de-emulsifier to separate oil and biocatalyst (or bacterial cells) from a three-phase (oil/biocatalyst/aqueous phase) emulsion, formed in diesel biodesulfurization employing Gordonia nitida, improved oil recovery by centrifugation from about 50% in its absence to almost 100% at 3% (v/v). The biocatalyst recovered with ethanol addition showed similar specific growth rates (0.03 h(-1)) and dibenzothiophene desulfurization rates (6-7.2 mol l(-1) h(-1)) to those (0.03 h(-1) and 7.1 mol l(1,) respectively) of the biocatalyst recovered with no ethanol addition. The desulfurization activity significantly increased as the number of the repeated recovery and reuse of the biocatalyst
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