Which of the following properties of water does not contribute to the fitness of the aqueous environment for living organisms?

#Question id: 14329

#Section 5: Bioprocess Engineering and Process Biotechnology

During exponential phase in batch culture, the growth rate of a culture is proportional to the concentration of cells present. When Streptococcus lactis bacteria are cultured in milk, the concentration of cells doubles in45 min. If this rate of growth is maintained for 12 h, what is the final concentration of cells relative to the inoculum level?

#Question id: 14330

#Section 5: Bioprocess Engineering and Process Biotechnology

A radioactive isotope decays at a rate proportional to the amount of isotope present. If the concentration of isotope is C (mg l^-I), its rate of decay is:

A solution of the isotope ³²p is used to radioactively label DNA for hybridisation studies. The half-life of ³²p is 14.3 days. According to institutional safety requirements, the solution cannot be discarded until the activity is 1% its present value. How long will this take?____________________

#Question id: 14331

#Section 5: Bioprocess Engineering and Process Biotechnology

To ensure turbulent conditions and minimum mixing time during agitation with a turbine impeller, the Reynolds number must be at least 10⁴. A stirred laboratory-scale fermenter with a turbine impeller 5 cm in diameter is operated at 800 rpm. If the density of broth being stirred is close to that of water, what is the upper limit for viscosity of the suspension if adequate mixing is to be maintained?

#Question id: 14332

#Section 5: Bioprocess Engineering and Process Biotechnology

To ensure turbulent conditions and minimum mixing time during agitation with a turbine impeller, the Reynolds number must be at least 10⁴. A stirred laboratory-scale fermenter with a turbine impeller 5 cm in diameter is operated at 800 rpm. If the density of broth being stirred is close to that of water. The mixing system is scaled up so the tank and impeller are 15 times the diameter of the laboratory equipment. The stirrer in the large vessel is operated so that the stirrer tip speed (tip speed = π N i D i) is the same as in the laboratory apparatus. How does scale-up affect the maximum viscosity. 

#Question id: 14333

#Section 5: Bioprocess Engineering and Process Biotechnology

A cylindrical bioreactor of diameter 3 m has four baffles. A Rushton turbine mounted in the reactor has a diameter one third the tank diameter and is operated at a speed of 90 rpm. The density of the fluid is approximately I g cm^-3. The reactor is used to culture an anaerobic organism that does not require gas sparging. The broth can be assumed Newtonian. As the cells grow, the viscosity of the broth increases. when the viscosity is 1000 times greater than water, estimate the power required to achieve turbulence.

#Question id: 14334

#Section 5: Bioprocess Engineering and Process Biotechnology

Laboratory-scale fermenters are usually mixed using small stirrers with electric motors rated between 100 and 500 W. One such motor is used to drive a 7cm turbine impeller in a small reactor containing fluid with the properties of water. The stirrer speed is 900 rpm. Estimate the power requirements for this process.