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  • Life Sciences  (8)
  • Chromatographic data  (1)
  • 1
    Digitale Medien
    Digitale Medien
    Ensuring both normality and homocedasticity of chromatographic data-ratios for internal-standard least-squares calibration (1998)
    Springer
    Chromatographia 47 (1998), S. 550-556 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Chromatographic data ; Internal-standard calibration ; Least-squares regression ; Ratio-data homocedasticity ; Ratio-data normality
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary Because the quotient of two normal variables does not fit a normal distribution and tends to be heterocedastic, the use of internal-standard least-squares regression on data obtained from such ratios gives a calibration function which can result in inaccurate determination of the concentration of analyte in a sample. In this work we have studied simulated situations in which area-ratios are fitted to a normal distribution. It is shown that the least-squares model is inappropriate when the ordinate data-ratios are not normally distributed, and some recommendations are proposed to ensure both normality and homocedasticity of the quotient of analyte/internal-standard signals. Finally, GC-MS separation and quantification of nine fatty acids by use of an internal standard are used for experimental verification of the conclusions reached.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02467494
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  • 2
    Digitale Medien
    Digitale Medien
    Invertase secretion in Hansenula polymorpha under the AOX1 promoter from Pichia pastoris (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Yeast 12 (1996), S. 815-822 
    Details
    ISSN: 0749-503X
    Schlagwort(e): HARS, Hansenula autonomously replicating sequence ; SUC2, sucrose invertase ; AOX1, alcohol oxidase ; Pollk, polymerase I, fragment klenow ; Life Sciences ; Life Sciences (general)
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie
    Notizen: A DNA fragment containing a transcription regulating region of the alcohol oxidase (AOX1) gene from the methylotrophic yeast Pichia pastoris was used in the construction of a vector for the expression of heterologous proteins in the methylotrophic yeast Hansenula polymorpha. We used this vector to clone the SUC2 gene from Saccharomyces cerevisiae into H. polymorpha yeast.The culture conditions for invertase production using a fed-batch culture were studied. More than 1·5×103 U/ml of biologically active invertase (1 g/l) were secreted to the cellular periplasmic space. The fermentative process was scaled up to 50 l.Invertase produced from H. polymorpha was glycosylated, but it contained significantly less carbohydrate than protein produced by S. cerevisiae. Using the Western-blot technique, it was observed that invertase secreted from H. polymorpha and invertase secreted from S. cerevisiae showed common antigenic determinants.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
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  • 3
    Digitale Medien
    Digitale Medien
    Determination of the best nutrient medium for the production of L-lactic acid from beet molasses a statistical approach (1993)
    Berlin : Wiley-Blackwell
    Acta Biotechnologica 13 (1993), S. 103-110 
    Details
    ISSN: 0138-4988
    Schlagwort(e): Life Sciences ; Life Sciences (general)
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Optimization studies have been carried out for the production of L-lactic acid from the fermentation of beet molasses by Lactobacillus delbrueckii. A PLACKETT-BURMAN Design and a Central Composite Design have been used to determine the most suitable nutrient medium for obtaining a maximum cell concentration. A second-order polynomial empirical model relating both the cell and nutrient concentrations was formulated. The variables selected for the study were Yeast Extract, Peptone, Tween 80 (antifoam), MgSO4 · 7H2O, MnSO4·4H2O, FeSO4 · 7H2O and K2HPO4/KH2PO4. Among them, only Yeast Extract and Peptone were found to significantly affect the cell concentration. A maximum cell yield was found when the concentrations of Yeast Extract and Peptone were, respectively, 5.31 g/l and 5.08 g/l. All conclusions are restricted to the experimental range studied.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/abio.370130204
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  • 4
    Digitale Medien
    Digitale Medien
    Optimization of the conditions of the fermentation of beet molasses to lactic acid by Lactobacillus delbrueckii (1994)
    Berlin : Wiley-Blackwell
    Acta Biotechnologica 14 (1994), S. 251-260 
    Details
    ISSN: 0138-4988
    Schlagwort(e): Life Sciences ; Life Sciences (general)
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Optimization studies were carried out for the production of L-lactic acid from the fermentation of beet molasses by Lactobacillus delbrueckii. A Central Composite Design was used to determine the optimum values of the process variables (temperature, pH, inoculum concentration, and initial sucrose concentration) for obtaining the maximum yield and the maximum volumetric productivity of lactic acid. Among the variables selected for study, it was found that all of them apart from the temperature significantly affected the responses (yield and volumetric productivity of lactic acid). The Central Composite Design also permitted formulating two second-order polynomial empirical models relating to the responses and the significant variables. From these models it was possible to determine the value of the variables giving the maximum yield of lactic acid production (87.8%) and the maximum volumetric rate of lactic acid biosynthesis (2.7 g/l · h). Finally, the dependence of the lactic acid yield and productivity on the model variables was investigated. All conclusions are restricted to the experimental range studied.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/abio.370140307
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  • 5
    Digitale Medien
    Digitale Medien
    Behaviour of different Lactobacillus species in the production of lactic acid by the fermentation of whey (1995)
    Berlin : Wiley-Blackwell
    Acta Biotechnologica 15 (1995), S. 67-76 
    Details
    ISSN: 0138-4988
    Schlagwort(e): Life Sciences ; Life Sciences (general)
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: The behaviour of different Lactobacillus casei and Lactobacillus plantarum species in the fermentation of Manchego whey was experimentally studied and the results were statistically analyzed using a hypothesis contrast method. The steadiness of the velocity of the production of lactic acid during the fermentation process allowed the use of this variable to compare the different microorganisms. From this comparison it was inferred that the individuals of the same population behave alike and that the L. casei population produces lactic acid at a higher rate than the L. plantarum population. A competitive effect among the members of the L. casei population was also observed.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/abio.370150109
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  • 6
    Digitale Medien
    Digitale Medien
    Optimization of the fermentation of whey by Lactobacillus casei (1993)
    Berlin : Wiley-Blackwell
    Acta Biotechnologica 13 (1993), S. 323-331 
    Details
    ISSN: 0138-4988
    Schlagwort(e): Life Sciences ; Life Sciences (general)
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Optimization studies have been carried out for the production of L-lactic acid from the fermentation of whey by Lactobacillus casei. Two Statistical Designs, a full 24 Factorial Design and a full 32 Factorial Design, have been used to determine the most suitable values of the operational variables for obtaining the maximum lactic acid production rate. The variables selected for study were temperature, pH, lactose concentration, and inoculum concentration. Among them only temperature and pH were found to affect the response significantly. A second-order polynomial empirical model relating both the response (lactic acid production rate) and the variables was formulated. The maximum acid production rate was found when the values of pH and temperature were 5.4 and 38°C, respectively. All conclusions are restricted to the experimental range studied.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/abio.370130403
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  • 7
    Digitale Medien
    Digitale Medien
    Hydrolysis of cellobiose using β-glucosidase from Penicillium funiculosum. Kinetic analysis (1999)
    Berlin : Wiley-Blackwell
    Acta Biotechnologica 19 (1999), S. 3-16 
    Details
    ISSN: 0138-4988
    Schlagwort(e): Life Sciences ; Life Sciences (general)
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: The kinetics of cellobiose hydrolysis was studied using β-glucosidase from Penicillium funiculosum, both free and immobilized on nylon powder, at different temperatures, pH values, enzymatic activities and initial cellobiose and glucose concentrations.The experimental results were fitted to a kinetic model by considering the substrate and product inhibitions as well as the thermal deactivation of β-glucosidase with a mean deviation of less than 10%. The immobilization of β-glucosidase led to an increase in the stability of the enzyme against changes in the pH value.
    Zusätzliches Material: 10 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/abio.370190102
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  • 8
    Digitale Medien
    Digitale Medien
    Enzymatic hydrolysis of wheat straw: Kinetic analysis (1993)
    Berlin : Wiley-Blackwell
    Acta Biotechnologica 13 (1993), S. 21-30 
    Details
    ISSN: 0138-4988
    Schlagwort(e): Life Sciences ; Life Sciences (general)
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Pretreated wheat straw was enzymatically hydrolyzed in 250-ml flasks using the culture filtrate of Trichoderma reesei QM-9414. The influence of the initial enzymatic activity in the liquid phase was studied. The unreacted core model was used to analyze the experimental data obtained at 40, 46 and 50°C. The model adequately describes the data for hydrolysis times lower than 10 h.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/abio.370130105
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  • 9
    Digitale Medien
    Digitale Medien
    Immobilization of β-glucosidase from different sources on nylon tube (1992)
    Berlin : Wiley-Blackwell
    Acta Biotechnologica 12 (1992), S. 357-364 
    Details
    ISSN: 0138-4988
    Schlagwort(e): Life Sciences ; Life Sciences (general)
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Cellulase from four different fungi and β-glucosidase from almonds were immobilized on the inner surface of nylon tubing. The highest values of β-glucosidase activity retention on the support were obtained when P. funiculosum and N. crassa were used as the enzyme source. A comparative study of the thermal stability referring to β-glucosidase activity was developed using free and immobilized enzymes. The most stable β-glucosidases (from P. funiculosum and A. niger) did not show an appreciable change in its thermal stability after immobilization. An important increase in thermal stability was observed when less stable β-glucosidases (from T. reesei, N. crassa and almonds) were immobilized.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/abio.370120502
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