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  • Biochemistry and Biotechnology  (269)
  • Engineering General  (68)
  • 1
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Data reported here and previously indicate that when dextrin is hydrolyzed in the presence of immobilized glucoamylase, use of a larger average molecular weight substrate leads to lower overall rates of hydrolysis, while the maltose concentration during the bulk of the reaction and the maximum glucose concentration are lower than when the soluble form of the enzyme is employed under the same conditions. Computer simulation of the system demonstrated that all three observations were caused by pore diffusion limitation: the first by slow diffusion of substrate, the second by slow diffusion of intermediates, and the third by slow diffusion of glucose. Follow-up experiments with glucoamylase immobilized to particles of different sizes confirmed this finding, as results with the smallest beads were identical to those with soluble glucoamylase.
    Additional Material: 8 Ill.
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  • 2
    ISSN: 0268-2575
    Keywords: penicillin G ; emulsion liquid membrane ; decomposition ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: To confirm the applicability for the extraction of penicillin G by an emulsion liquid membrane (ELM), the degree of decomposition of penicillin G during extraction was theoretically calculated. Decomposition was less than 1% provided that the initial sodium carbonate concentration in the internal phase was correctly determined, which proved the applicability of the ELM process. The procedure to determine the initial carbonate concentration in the internal phase was also described in order that the pH in the internal phase should be within the relatively stable range for penicillin G at the end of the extraction.
    Additional Material: 7 Ill.
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  • 3
    ISSN: 0268-2575
    Keywords: penicillin G ; emulsion liquid membrane ; optimum extraction conditions ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Penicillin G extraction by an emulsion liquid membrane (ELM) was investigated. The effects of surfactants, diluents, and carrier mixtures, together with their combined effects on the initial extraction rate and the emulsion stability were examined. Surfactants, diluents, and carriers used were Span80 (sorbitan monooleate)/ECA4360J (nonionic polyamine), n-butyl acetate/kerosene, and DOA (dioctylamine)/Amberlite LA-2 (secondary amine), respectively. The optimum extraction conditions were found to be 20% (v/v) of Span80 in ECA4360J as a surfactant, kerosene as a diluent and Amberlite LA-2 as a carrier.
    Additional Material: 7 Ill.
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  • 4
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Glucoamylase was immobilized to porous silica and its kinetics and stability were observed with acid- and α-amylase-hydrolyzed dextrin as feed. The enzyme was found to be extremely stable in both laboratory and pilot plant operations. When the feed had been previously only lightly hydrolyzed, pore diffusion limitation caused appreciable decreases in glucose production rate. The severity of starch hydrolysis to dextrin markedly affected ultimate glucose yields. The diffusional gradients present in the carrier pores caused the immobilized enzyme to yield lower glucose concentrations than the free enzyme at similar feed conditions.
    Additional Material: 4 Ill.
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  • 5
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 5 Ill.
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  • 6
    ISSN: 0006-3592
    Keywords: poly-(3-hydroxybutyric acid) ; PHB ; Escherichia coli ; morphology ; plasmid ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A stable high-copy-number plasmid pSYL105 containing the Alcaligenes eutrophus polyhydroxyalkanoic acid (PHA) biosynthesis genes was constructed. This plasmid was transferred to seven Escherichia coli strains (K12, B, W, XL1-Blue, JM109, DH5α, and HB101), which were subsequently compared for their ability to synthesize and accumulate ploy- (3-hydroxybutyric acid) (PHB). Growth of recombinant cells and PHB synthesis were investigated in detail in Luria-Bertani (LB) medium containing 20 g/L glucose. Cell growth, the rate of PHB synthesis, the extent of PHB accumulation, the amount of glucose utilized, and the amount of acetate formed varied from one strain to another. XL1-Blue (pSYL105) and B (pSYL105) synthesized PHB at the fastest rate, which was ca. 0.2 g PHB/g true cell mass-h, and produced PHB up to 6-7 g/L. The yields of cell mass, true cell mass, and PHB varied considerably among the strains. The PHB yield of XL1-Blue (pSYL105) in LB plus 20 g/L glucose was as high as 0.369 g PHB/g glucose. Strains W (pSYL105) and K12 (pSYL105) accumulated the least amount of PHB with the lowest PHB yield at the lowest synthesis rate. JM109 (pSYL105) accumulated PHB to the highest extent (85.6%) with relatively low true cell mass (0.77 g/L). Considerable filamentation of cells accumulating PHB was observed for all strains except for K12 and W, which seemed to be due either to the overexpression of the foreign PHA biosynthesis enzymes or to the accumulation of PHB. © 1994 John Wiley & Sons, Inc.
    Additional Material: 6 Ill.
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  • 7
    ISSN: 0006-3592
    Keywords: nar promoter ; inducible promoter ; nitrate reductase ; anaerobic conditions ; Escherichia coli ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The nar promoter of Escherichia coli, which is maximally induced under anaerobic conditions in the presence of nitrate, was characterized to see whether the nar promoter cloned onto pBR322 can be used as an inducible promoter. To increase the expression level, the nar promoter was expressed in E. coli where active nitrate reductase cannot be expressed from the nar operon on the chromosome. A plasmid with the lacZ gene expressing β-galactosidase instead of the structural genes of the nar operon was used to simplify an assay of induction of the nar promoter. The following effects were investigated to find optimal conditions: methods of inducing the nar promoter, optimal nitrate and molybdate concentrations maximally inducing the nar promoter, the amount of expressed β-galactosidase, and induction ratio (specific β-galactosidase activity after maximal induction/specific β-galactosidase activity before induction.)The following results were obtained from the experiments: induction of the nar promoter was optimal when E. coli was grown in the presence of 1% nitrate at the beginning of culture; expression of β-galactosidase was not affected by molybdate; the induction ratio was maximal, approximately 300, when the overnight culture was grown in the flask for 2.5 h (OD600 is congruent to 1.3) before being transferred to the fermentor; the amount of β-galactosidase per cell and per medium volume was maximal when E. coli was grown under aerobic conditions to OD600 = 1.7; then the nar promoter was induced under microaerobic conditions made by lowering dissolved oxygen level (DO) to 1-2%. After approximately 6 h of induction, OD600 became 3.2 and specific β-galactosidase activity became 36,000 Miller units, equivalent to 35% of total cellular proteins, which was confirmed from sodium dodecyl sulfate-polyacrylamide gel electrophoresis. © 1996 John Wiley & Sons, Inc.
    Additional Material: 8 Ill.
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  • 8
    ISSN: 0173-0835
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: The factors affecting micellar electrokinetic capillary chromatographic separation of hippuric and o-, m-, p-methylhippuric acid were investigated by changing the species of micelles, and adding urea to the micellar solution. The analysis of hippurates in human urine is demonstrated under optimum conditions using 20 mM phosphate buffer (pH 8.0) containing 100 mM dodecyltrimethylammonium bromide and 4 M urea at -22 kV applied voltage. This method proved suitable for the screening of hippurates in human urine following occupational exposure to toluene and xylene.
    Additional Material: 5 Ill.
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  • 9
    ISSN: 0173-0835
    Keywords: Capillary electrophoresis ; Protein detection ; Fluorescence labeling ; Laser-induced fluorescence ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: A low-cost and highly sensitive laser-induced fluorescence detector for on-column detection systems was constructed and its applications were demonstrated in protein separation by capillary electrophoresis. The limit of detection (LOD) at a signal-to-noise ratio of 2 for Lissamine 20 was about 1.4 × 10-21 mole at 10 nL sample injection and the relative standard deviation (RSD) for 1.5 × 10-11 M of Lissamine 20 solution was about 15%. These values are comparable to or even better than those reported using a similar on-column detection system. This sensitive LIF detection was applied for the study of tryptic digestion of insulin and for urinary protein profiling.
    Additional Material: 5 Ill.
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  • 10
    ISSN: 0268-2575
    Keywords: emulsion swelling ; additives ; HLB value ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Control of the swelling of two different liquid emulsion membrane systems for separation of lactic acid was examined. The major disadvantages of swelling are dilution of the separated product and emulsion breakage. Several additives including liquid paraffin, cyclohexanone and n-decanol were investigated with respect to both emulsion swelling and lactic acid separation rate. If swelling is a function of surfactant concentration, the swelling increases with the quantity of the hydrophilic part in the surfactant. Therefore, a surfactant with a low hydrophilic/lipophilic balance (HLB) value should be used to reduce the swelling. The use of Span 85 (HLB = 1·8) as co-surfactant achieved the objective in the case of a tri-n-octylamine/Span 80 system.
    Additional Material: 9 Ill.
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