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 10^36.2 s^-1

#Question id: 14304

#Section 5: Bioprocess Engineering and Process Biotechnology

Pseudomonas sp. has a mass doubling time of 2.4 h when grown on acetate. The saturation constant using this substrate is 1.3 g/l (which is unusually high), and cell yield on acetate is 0.46 g cell/g acetate. If we operate a chemostat on a feed stream containing 38 g/l acetate, find the Cell productivity at 0.8 Dmax?

_____________

#Question id: 14305

#Section 5: Bioprocess Engineering and Process Biotechnology

Ethanol is to be used as a substrate for single-cell protein production in a chemostat. The available equipment can achieve an oxygen transfer rate of 10 g O₂/l of liquid per hour. Assume the kinetics of cell growth on ethanol is of the Monod type, with µm = 0.5 h^–1, K_s = 30 mg/l, YX/S = 0.5 cells/g ethanol, and YO2/S = 2 g O2/g EtOH. We wish to operate the chemostat with an ethanol concentration in the feed of 22 g/L. We also wish to maximize the biomass productivity and minimize the loss of unused ethanol in the effluent. Determine the required dilution rate

#Question id: 14306

#Section 5: Bioprocess Engineering and Process Biotechnology

Pseudomonas putida with mm = 0.5 h^-1 is cultivated in a continuous culture under aerobic conditions where D = 0.28 h^-1 . The carbon and energy source in the feed is lactose with aconcentration of S₀ = 2 g/l. The effluent lactose concentration is desired to be S = 0.1 g/l. If the growth rate is limited by oxygen transfer, by using the following information:

Determine the steady-state biomass concentration (X)

                _________________

#Question id: 14307

#Section 5: Bioprocess Engineering and Process Biotechnology

Pseudomonas putida with mm = 0.5 h^-1 is cultivated in a continuous culture under aerobic conditions where D = 0.28 h^-1 . The carbon and energy source in the feed is lactose with aconcentration of S₀ = 2 g/l. The effluent lactose concentration is desired to be S = 0.1 g/l. If the growth rate is limited by oxygen transfer, by using the following information

Determine specific rate of oxygen consumption (q_O2 ).

#Question id: 14308

#Section 5: Bioprocess Engineering and Process Biotechnology

Pseudomonas putida with µm = 0.5 h^-1 is cultivated in a continuous culture under aerobic conditions where D = 0.28 h^-1 . The carbon and energy source in the feed is lactose with aconcentration of S₀ = 2 g/l. The effluent lactose concentration is desired to be S = 0.1 g/l. If the growth rate is limited by oxygen transfer, by using the following information:

What should be the oxygen-transfer coefficient (k_La) in order to overcome oxygentransfer limitation (i.e., CL = 2 mg/l)? ___________________

#Question id: 14309

#Section 5: Bioprocess Engineering and Process Biotechnology

Glucose is converted to ethanol by immobilized yeast cells entrapped in gel beads. The specific rate of ethanol production is: q_P = 0.2 g ethanol/g-cell-h. The effectiveness factor for an average bead is 0.8. Each bead contains 50 g/L of cells. The voids volume in the column is 40%. Assume growth is negligible (all glucose is converted into ethanol). The feed flow rate is F = 400 l/h and glucose concentration in the feed is S_0i = 150 g glucose/l. The diameter of the column is 1 m and the yield coefficient is about 0.49 g ethanol/g glucose. The column height is 4 m. What is the glucose conversion at the exit of the column?