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TLS Online TPP Program

#Question id: 4153

Ubiquitin-mediated protein degradation is a complex process, and many of the signals remain unknown.  One known signal involves recognition of amino acids in a processed protein that are either stabilizing (Ala, Gly, Met, Ser, etc.) or destabilizing (Arg, Asp, Leu, Lys, Phe, etc.), and are located at:

#Section 3: Genetics, Cellular and Molecular Biology

  1. a helix-turn-helix motif in the protein.

  2. a lysine-containing target sequence in the protein.

  3. a zinc finger structure in the protein.

  4. the amino-terminus of the protein.

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TLS Online TPP Program

#Question id: 14244

#Section 5: Bioprocess Engineering and Process Biotechnology

Ethanol is produced by anaerobic fermentation of glucose by Saccharomyces cerevisiae. For the particular strain of S. cerevisiae employed, the maintenance coefficient is 0.18 kg kg- 1 h- 1, Yxs is 0.11 kg kg-1, YPX is 3.9 kg kg-1 and µmax is 0.4 h-1.  It is decided to investigate the possibility of using Zymomonas mobilis bacteria instead of yeast for making ethanol. Z. mobilis is known to produce ethanol under anaerobic conditions using a different metabolic pathway to that employed by yeast. Typical values of Yxs are lower than for yeast at about 0.06 kg kg-1; on the other hand, the maintenance coefficient is higher at 2.2 kg kg -1 h -1. Ypx for Z. mobilis is 7.7 kg kg-l; µmax is 0.3 h- 1.  From stoichiometry, what is the maximum theoretical yield of ethanol from glucose                 
TLS Online TPP Program

#Question id: 14245

#Section 5: Bioprocess Engineering and Process Biotechnology

Ethanol is produced by anaerobic fermentation of glucose by Saccharomyces cerevisiae. For the particular strain of S. cerevisiae employed, the maintenance coefficient is 0.18 kg kg- 1 h- 1, Yxs is 0.11 kg kg-1, YPX is 3.9 kg kg-1 and µmax is 0.4 h-1.  It is decided to investigate the possibility of using Zymomonas mobilis bacteria instead of yeast for making ethanol. Z. mobilis is known to produce ethanol under anaerobic conditions using a different metabolic pathway to that employed by yeast. Typical values of Yxs are lower than for yeast at about 0.06 kg kg-1; on the other hand, the maintenance coefficient is higher at 2.2 kg kg -1 h -1. Ypx for Z. mobilis is 7.7 kg kg-l; µmax is 0.3 h- 1. Y’PS is maximum and equal to the theoretical yield when there is zero growth and all substrate entering the cell is used for maintenance activities. If ethanol is the sole extracellular product of energy-yielding metabolism, calculate mp for yeast?

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TLS Online TPP Program

#Question id: 14246

#Section 5: Bioprocess Engineering and Process Biotechnology

A steam steriliser is used to sterilise liquid medium for fermentation. The initial concentration of contaminating organisms is 108 per litre. For design purposes, the final acceptable level of contamination is usually taken to be 10-3cells; this corresponds to a risk that one batch in a thousand will remain contaminated even after the sterilisation process is complete. For how long should 1 m3 medium be treated if the temperature is 80⁰C ________________.10^6

 To be safe, assume that the contaminants present are spores of Bacillus stearothermophilus, one of the most heat-resistant microorganisms known. For these spores the activation energy for thermal death is 283 kJ gmo1-1 and the Arrhenius constant is 1036.2 s-1
TLS Online TPP Program

#Question id: 14247

#Section 5: Bioprocess Engineering and Process Biotechnology

A steam steriliser is used to sterilise liquid medium for fermentation. The initial concentration of contaminating organisms is 108 per litre. For design purposes, the final acceptable level of contamination is usually taken to be 10-3cells; this corresponds to a risk that one batch in a thousand will remain contaminated even after the sterilisation process is complete. For how long should 1 m3 medium be treated if the temperature is 121⁰C ________________.

 To be safe, assume that the contaminants present are spores of Bacillus stearothermophilus, one of the most heat-resistant microorganisms known. For these spores the activation energy for thermal death is 283 kJ gmo1-1 and the Arrhenius constant is 1036.2 s-1

TLS Online TPP Program

#Question id: 14248

#Section 5: Bioprocess Engineering and Process Biotechnology

A steam steriliser is used to sterilise liquid medium for fermentation. The initial concentration of contaminating organisms is 108 per litre. For design purposes, the final acceptable level of contamination is usually taken to be 10-3cells; this corresponds to a risk that one batch in a thousand will remain contaminated even after the sterilisation process is complete. For how long should 1 m3 medium be treated if the temperature is 140⁰C ________________.

        To be safe, assume that the contaminants present are spores of Bacillus stearothermophilus, one of the most heat-resistant microorganisms known. For these spores the activation energy for thermal death is 283 kJ gmo1-1 and the Arrhenius constant is 1036.2 s-1

TLS Online TPP Program

#Question id: 14249

#Section 5: Bioprocess Engineering and Process Biotechnology

Aspartase enzyme is used industrially for manufacture of aspartic acid, a component of low-calorie sweetener. Fumaric acid and ammonia are converted to aspartic acid according to the equation:

 
                                        
Under investigation is a process using aspartase in intact Bacillus cadaveris cells. In the substrate range of interest, the conversion can be described using Michaelis-Menten kinetics with K m 4.0 gl-1. The substrate solution contains 15% (w/v) ammonium fumarate; enzyme is added in the form of lyophilised cells and the reaction stopped when 85% of the substrate is converted. At 32⁰C vmax for the enzyme is 5.9 g l-1h-1 and its half-life is 10.5 d. At 37⁰C Vmax increases to 8.5 g l- 1 h- I but the half-life is reduced to 2.3 d. The average downtime between batch reactions is 28 h. calculate the reactor volume required to produce 5000 tonnes of aspartic acid per year