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  • Biochemistry and Biotechnology  (8)
  • tacticity  (4)
  • Wiley-Blackwell  (12)
  • American Chemical Society (ACS)
  • 1
    Electronic Resource
    Electronic Resource
    Bioleaching of zinc sulfide concentrate by Thiobacillus ferrooxidans (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 39 (1992), S. 66-74 
    Details
    ISSN: 0006-3592
    Keywords: bioleaching ; adsorption ; growth kinetics ; Thiobacillus ferrooxidans ; zinc sulfide ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The kinetics of the bioleaching of ZnS concentrate by Thiobacillus ferrooxidans was studied in a well-mixed batch reactor. Experimental studies were made at 30°C and pH 2.2 on adsorption of the bacteria to the mineral, ferric iron leaching, and bacterial leaching. The adsorption rate of the bacteria was fairly rapid in comparison with the bioleaching rate, indicating that the bacterial adsorption is at equilibrium during the leaching process. The adsorption equilibrium data were correlated by the Langmuir isotherm, which is a useful means for predicting the number of bacteria adsorbed on the mineral surface. The rate of chemical leaching varied with the concentration of ferric iron, and the first-order reaction rate constant was determined. Bioleaching in an iron-containing medium was found to take place by both direct bacterial attack on the sulfide mineral and indirect attack via ferric iron. In this case, the ferric iron was formed from the reaction product (ferrous iron) through the biological oxidation reaction. To develop rate expressions for the kinetics of bacterial growth and zinc leaching, the two bacterial actions were considered. The key parameters appearing in the rate equations, the growth yield and specific growth rate of adsorbed bacteria, were evaluated by curve fitting using the experimental data. This kinetic model allowed us to predict the liquid-phase concentrations of the leached zinc and free cells during the batch bioleaching process.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260390111
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  • 2
    Electronic Resource
    Electronic Resource
    Kinetics of growth and elemental sulfur oxidation in batch culture of thiobacillus ferrooxidans (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 44 (1994), S. 667-673 
    Details
    ISSN: 0006-3592
    Keywords: growth kinetics ; solid substrate ; bacterial adsorption ; Thiobacillus ferrooxidans ; sulfur ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The kinetics of oxidation of elemental sulfur by Thiobacillus ferrooxidans in a batch reactor was followed by measuring the concentration of adsorbed cells on the sulfur surface, the concentration of free cells in liquid medium, and the amount of sulfur oxidized. As the elemental sulfur was oxidized to sulfate, the liquid-phase concentration of free cells continued to increase with time, whereas the surface concentration of adsorbed cells per unit weight of sulfur approached a limiting value, i.e., the maximum adsorption capacity. During sulfur oxidation, there was a close correlation between the concentrations of adsorbed and free cells, and these data were well correlated with the Langmuir isotherm. The observed rates of batch growth and sulfur oxidation were consistent with a kinetic model, assuming that the growth rate of batch growth and sulfur oxidation were consistent with a kinetic model. Assuming that the growth rate of adsorbed bacteria is proportional to the product of the concentration of adsorbed cells and the fraction of adsorption sites unoccupied by cells. The kinetic and stoichiometric parameters appearing in the model were evaluated using the experimental data and were compared with parameters determined previously for a few metal sulfides. © 1994 John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260440602
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  • 3
    Electronic Resource
    Electronic Resource
    Maximum virginiamycin production by optimization of cultivation conditions in batch culture with autoregulator addition (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 49 (1996), S. 437-444 
    Details
    ISSN: 0006-3592
    Keywords: Streptomyces virginiae ; autoregulator ; virginiae butanolide ; virginiamycin fermentation ; optimization ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A strategy for optimization of non-growth-associated production in batch culture employing an empirical approach was developed through the study of virginiamycin production. The strategy is formulated with two aims: attaining a high cell concentration at the beginning of the production phase without decrease in production activity; and enhancing the production activity during the production phase. As a practical example, the goal of a maximum virginiamycin (M and S) production in the batch culture of Streptomyces virginiae was set. To attain a high cell concentration in the production phase of the batch culture, that is, to extend the growth phase for as long as possible, the optimum composition and concentration of the complex medium, especially the yeast extract (YE) concentration, were first investigated. Dissolved oxygen (DO) concentration control was also a parameter considered in maintaining the production activity during the production phase. In addition, to enhance the production activity, an optimum addition strategy of an autoregulator, virginiae butanolide-C (VB-C), was investigated. Combining these measures, the optimum cultivation conditions were found to be an initial YE concentration in the complex medium of 45 g/L, the shot addition of 300 μg/L of VB-C 11.5 h after the start of the batch culture, and a DO concentration maintained above 2 mg/L. The maximum concentrations of virginiamycin M and S were about ninefold those obtained under nonoptimum cultivation conditions. Nonoptimum cultivation conditions consisted of an initial YE concentration one sixth (7.5 g/L) that of the optimum cultivation conditions, and no VB-C addition. These conditions were used as representative of the standard cultivation of virginiamycin in this study. The strategy developed here will be applicable to the production of other antibiotics, especially to the cultivation of Streptomyces species, in which a hormonelike signal material (an autoregulator) plays an important role in antibiotic production. © 1996 John Wiley & Sons, Inc.
    Additional Material: 8 Ill.
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  • 4
    Electronic Resource
    Electronic Resource
    Bioleaching of pyrite by acidophilic thermophile Acidianus brierleyi (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 48 (1995), S. 592-600 
    Details
    ISSN: 0006-3592
    Keywords: Acidianus brierleyi ; pyrite ; bioleaching ; acidophilic thermophile ; metal recovery ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The kinetics of bioleaching of pyrite (FeS2) by the acidophilic thermophilic bacterium Acidianus brierleyi was studied in a well-mixed batch reactor. Experiments were done at 65°C and pH 1.5 on adsorption of A. brierleyi onto pyrite particles, liquid-phase oxidation of ferrous iron by A. brierleyi, and microbial leaching of pyrite. The adsorption of A. brierleyi was a fast process; equilibrium was attained within the first 30 min of exposure to pyrite. The adsorption equilibrium data were well correlated with the Langmuir isotherm. The oxidation of ferrous iron was markedly accelerated in the presence of A. brierleyi, and the growth yield on ferrous iron was determined. The bioleaching of pyrite by A. brierleyi was found to take place with a direct attack by adsorbed cells on the surface of pyrite, the chemical leaching of pyrite by ferric iron being insignificant. Rate data collected under a wide variety of operating variables were analyzed to determine kinetic and stoichiometric parameters for the microbial pyrite leaching. The specific growth rate on pyrite for A. brierleyi was about four times that for the mesophilic bacterium, Thiobacillus ferrooxidans, whereas the growth yields on pyrite for the two microbes were approximately equal to one another in magnitude. A comparison of A. brierleyi with T. ferrooxidans for pyrite leachability demonstrated the thermophile to be much more effective. © 1995 John Wiley & Sons, Inc.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260480606
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  • 5
    Electronic Resource
    Electronic Resource
    Optimum autoregulator addition strategy for maximum virginiamycin production in batch culture of Streptomyces virginiae (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 46 (1995), S. 437-442 
    Details
    ISSN: 0006-3592
    Keywords: Streptomyces virginiae ; autoregulator ; virginiae butanolide ; virginiamycin fermentation ; optimization ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Virginiae butanolides (VBs) are autoregulators of Streptomyces virginiae, which induce virginiamycin biosynthesis. Generally, autoregulators are synthesized by the microorganism itself during culture. Addition of chemically synthesized virginiae butanolide-C (VB-C), which is one of the VBs, can also control the induction time and the amount of virginiamycin production. The optimum concentration and shot-feeding time of VB-C for the maximum production of virginiamycins M and S were investigated in flasks and jar-fermentor batch cultures. VB-C addition later than 8 h from the start of culture induced not only virginiamycin M and S synthesis but also VB synthesis. Virginiamycin M and S production increased with the decrease of total VBs (produced VBs and added VB-C) concentration. That is, although VBs are needed to induce virginiamycin M and S synthesis, the amount of VB-C added should be such that as small an amount as possible of VBs is synthesized to achieve the maximum production of virginiamycins M and S. However, the VB-C addition earlier than 8 h from the start of culture showed no clear relationship between the amounts of VBs and virginiamycins M and S produced. In conclusion, the maximum production of virginiamycins M and S was attained by the shot addition of 5 μg/L VB-C at 8 h from the start of culture. The maximum value was about twofold that without VB-C addition. The optimum addition strategy of VB-C was confirmed by the jar-fermentor experiments. © 1995 John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260460507
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  • 6
    Electronic Resource
    Electronic Resource
    Cell cycle dependency of rice α-amylase production in a recombinant yeast (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 54 (1997), S. 262-271 
    Details
    ISSN: 0006-3592
    Keywords: cell cycle dependency ; recombinant yeast ; rice α-amylase ; synchronous culture ; arrested culture ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The cell cycle dependency of rice α-amylase production in Saccharomyces cerevisiae was investigated using synchronous and arrested cultures. The results of two separate synchronous cultures, using α-mating factor and a cdc28 mutant, indicated that the rice α-amylase-specific production rate is not constant during the cell cycle. The specific production rates during G1, S, and M phases were then ascertained by inhibiting the progression of the cell cycle using α-mating factor, hydroxyurea, and nocodazole, respectively. The specific production rate was found to be maximal during the M phase. The increase in the specific production rate during the M phase was confirmed from the accumulation of M-phase cells using a cdc15 mutant. The intracellular content of rice α-amylase was also measured during the cell cycle. Like the specific production rate, the intracellular content was found to fluctuate throughout the cell cycle, and to reach a maximum during M phase. © 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 54: 262-271, 1997.
    Additional Material: 10 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    Highly isotactic polyacrylonitriles prepared using dialkylmagnesium/water systems as initiators (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Polymer International 35 (1994), S. 249-255 
    Details
    ISSN: 0959-8103
    Keywords: stereospecific polymerization ; polyacrylonitrile ; tacticity ; dialkylmagnesium ; alkylaluminum ; water ; high molecular weight ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: An attempt was made to synthesize stereoregular polyacrylonitrile (PAN) with high molecular weight (e.g. viscosity-average molecular weight (M̄v) 〉 1 × 105) by anionic polymerization. The triad tacticities (i.e. the content of mm, mr and rr (m, meso; r, racemo)) of the polymers obtained were analyzed by 13C NMR and their M̄v was determined by viscometry in dimethylsulfoxide at 25°C using Kamide et al.'s Mark-Houwink-Sakurada equation. Highly isotactic and high molecular weight PAN with M̄v 〉 2.5 × 105 ((mm) ∼ 0.57) was synthesized in anisole at 130°C when the reaction product of di-n-hexylmagnesium with water supplied by heating sulfate hydrates (Na2SO4 10H2O, CuSO4 5H2O, and MgSO4 7H2O) was used as a polymerization catalyst. The M̄v of PAN was increased significantly by using the catalyst combined with triethylaluminum (Et3Al). Maximum M̄v attained was 9.7 × 105 ((mm) = 0.64). The main role of Et3Al added is explained as the reduction of OH groups in the catalyst and of residual H2O in the catalyst solution.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pi.1994.210350306
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  • 8
    Electronic Resource
    Electronic Resource
    Synthesis of ultra-high molecular weight polyacrylonitrile with highly isotactic content (mm 〉 0.60) using dialkylmagnesium/polyhydric alcohol system as catalyst (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Polymer International 36 (1995), S. 87-99 
    Details
    ISSN: 0959-8103
    Keywords: stereospecific polymerization ; polyacrylonitrile ; tacticity ; anionic polymerization ; dialkylmagnesium ; polyhydric alcohol ; ultra-high molecular weight ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: An attempt was made to synthesize a catalyst having high activity for synthesis of highly isotactic polyacrylonitrile (PAN) with high molecular weight by anionic polymerization. The reaction products of di-n-hexylmagnesium [(n-C6H13)2Mg] with alicyclic alcohols such as 1,4-cyclohexanediol or 1,5-decalindiol were found to be effective as polymerization catalysts for preparation of PAN samples whose triad isotacticity [the content of mm (m, meso configuration)] is about 0.64 and viscosity-average molecular weight (Mv) exceeds 1 × 105. The triad tacticities [mm, mr, and rr contents (r, racemo configuration)] of the polymers obtained were analysed by 13C NMR and their Mvs were determined by viscometry in dimethylsulphoxide at 25°C using Kamide et al.'s Mark-Houwink-Sakurada equation.Mv of PAN increased significantly by after-treatment of the catalysts, prepared from (n-C6H13)2Mg and alicyclic alcohols, with triethylalyminium (Et3Al). Ultra-high molecular weight PAN samples ranging in Mv from 2 × 106 to 6 × 106 [(mm) = 0.57-0.66] were obtained in anisole at 135°C by using the above catalyst system. A main role of Et3Al in these catalyst systems is considered to reduce, in advance, OH groups on the catalyst, resulting in a significant suppression of termination reactions of propagating PAN chains during the polymerization.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pi.1995.210360112
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  • 9
    Electronic Resource
    Electronic Resource
    Effect of addition of organoaluminum and organoboron compounds in the stereospecific polymerization of acrylonitrile using dialkylmagnesium as catalyst (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Polymer International 34 (1994), S. 397-405 
    Details
    ISSN: 0959-8103
    Keywords: stereospecific polymerization ; polyacrylonitrile ; tacticity ; dialkylmagnesium ; alkylaluminum ; additive ; anionic polymerization ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: An attempt was made to clarify the effect of addition of organoaluminum and organoboron compounds in the stereospecific polymerization of acrylonitrile (AN) initiated by dialkylmagnesium (R2Mg) above 100°C. The triad isotacticity (i.e. the content of mm (m: meso)) as well as the viscosity-average molecular weight (M̄v) of polyacrylonitrile (PAN) increased when trialkylaluminum (R3Al) and trialkylboron (R3B) were used as additives. Diisobutylaluminum hydride [(i-C4H9)2AlH] was found to be the best additive. in the stereospecific polymerization of AN, giving PAN with higher (mm) content (0.63), higher M̄v value (5.2 × 104), and a yield approximately double that obtained using (n-C6H13)2Mg alone. When the (n-C6H13)2Mg/(i-C4H9)2AlH system was used, the yield, (mm), and M̄v of PAN increased with polymerization temperature (Tp); maximum values of yield, (mm), and M̄v were obtained at c. 130°C. The optimum amount of additives was approximately equimolar to R2Mg as initiator. The 13C chemical shift of α-carbon in R2Mg at 90°C shifted by mixing with R3Al and R3B, respectively, indicating the existence of interaction between R2Mg and the additives. The main role of the additives is considered to be suppression of the self-association of R2Mg by strong interaction with R2Mg.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pi.1994.210340408
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  • 10
    Electronic Resource
    Electronic Resource
    Synthesis of highly isotactic (mm 〉 0.70) polyacrylonitrile by anionic polymerization using diethylberyllium as a main initiator (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Polymer International 35 (1994), S. 207-213 
    Details
    ISSN: 0959-8103
    Keywords: stereospecific polymerization ; polyacrylonitrile ; tacticity ; diethylberyllium ; additive ; anionic polymerization ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: An attempt was made to synthesize steroregular polyacrylonitrile (PAN) with a high triad isotacticity (i.e. the content of mm (m, meso)) exceeding 0.70 by the anionic polymerization method. In the stereospecific polymerization of acrylonitrile (AN) initiated by diethylberyllium (Et2Be) in xylene at 130°C, the (mm) content as well as the viscosity-average molecular weight (MÞv) of PAN increased by addition of diisobutylaluminum hydride (i-C4H9)2AlH) as an additive to the polymerization system. Maximum (mm) content, attained in the molar ratio region of (i-C4H9)2AlH/Et2Be 〉 1.0, was about 0.73. The stereospecific polymerization of AN was also initiated using a mixture of Et2Be and di-n-hexylamagnesium ((Et2Be/(n-C6H13)2 Mg system), where both Et2Be and (n-C6H13)2 Mg can induce the stereospecific polymerization of AN at 130°C. The (mm) content of the PAN sample prepared using the Et2Be/(n-C6H13)2 Mg system ((mm) = 0.64) was higher than that of PAN samples synthesized using Et2Be alone ((mm) = 0.56) and (n-C6H13)2Mg alone ((mm) = 0.51) under the same conditions except initiator. A significant difference in 13C chemical shifts of α-carbons between Et2Be (1.35 ppm) and (n-C6H13)2Mg (10.72 ppm) dissolved in hydrocarbon solvent at 110°C leads us to the conclusion that when Et2Be induces the stereospecific polymerization in the Et2Be/(n-C6H13)2Mg system as initiator, the main role of (n-C6H13)2Mg is considered to be the suppression of the association of Et2Be (active site) itself.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pi.1994.210350211
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