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  • Biochemistry and Biotechnology  (1)
  • Egglayers  (1)
  • 1
    ISSN: 1432-2242
    Schlagwort(e): Egglayers ; Marek's disease resistance ; Egg production ; Endogeneous viral genes ; Group specific antigen
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Endogenous viral (ev) genes related to the avian leukosis virus were classified in two differentially selected strains of Leghorns in order to investigate whether such genes affect production traits. Strain K had been selected for resistance to Marek's disease (MD) and for high egg production and egg weight, whereas strain S had been selected only for MD susceptibility. Except that founders of strain K included a few commercial birds, both strains were derived from a common genetic base. DNA restriction fragment length analyses of 110 strain K and 94 strain S birds revealed the presence of 8 different ev-genes, 6 of which were identical to previously identified loci. This result was confirmed by assays for group specific antigen (gs-antigen), the product of the gag region of the ev-genes. The levels of gs-antigen in the birds closely followed what had been predicted from data obtained from previously described ev-genes. Both strains had a similar average number of ev-genes per bird (3.5 and 3.2 for strains S and K, respectively). However, strain K carried only five different ev-genes while strain S carried seven. Four of these loci were present in both strains. Among the ev-genes absent or occurring less frequently in strain K were those that code either for infectious endogenous virus (ev-10 and possibly ev-19) or for the internal viral gag-proteins (ev-3). Only those ev-genes which are transcriptionally silent or which code for the viral envelope gene were present in increased frequencies in strain K. The results indicate that selection for egg traits and/or Marek's disease resistance reduces the frequency of ev-genes which produce endogenous virus or the viral gag-proteins.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991), S. 1087-1094 
    ISSN: 0006-3592
    Schlagwort(e): fermentation ; optimization ; enzymatic reactions ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Two general models for batch simultaneous enzymatic and microbial reaction (SEMR) processes are presented, the second derived from and simpler than the first and accounting for enzyme denaturation. Using the second model and parameter values from the literature, simulation was used to examine a range of enzyme addition rate strategies (in which the rate was a linear function of time) for a relatively fast ethanol fermentation and for a longer duration citric acid fermentation, both using cellulose as the substrate. For the ethanol process it is optimal (for a specific objective function which accounts for product value and enzyme cost) to add all the enzyme at the beginning of the process. But for the citric acid process a linearly decreasing enzyme addition rate, coupled with the addition of a small fraction of the enzyme at time zero, is better than pure batch operation or operation with the best constant enzyme feed rate.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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