Measurements show that the pH of a particular lake is 4.0. What is the hydroxide ion concentration of the lake?

#Question id: 14327

#Section 5: Bioprocess Engineering and Process Biotechnology

Bakers' yeast is produced in a 50 000-litre fermenter under aerobic conditions. The carbon substrate is sucrose; ammonia is provided as nitrogen source. The average biomass composition is CH_1.830_0.55N_0.17 with 5% ash. Under efficient growth conditions, biomass is the only major product; the biomass yield from sucrose is 0.5 g g^-I. If the specific growth-rate is 0.45 h^-l, estimate the rate of heat removal required to maintain constant temperature in the fermenter when the yeast concentration is 10 g l^{- 1}     _______________________.10^6

#Question id: 14328

#Section 5: Bioprocess Engineering and Process Biotechnology

In a sewage-treatment plant, a large concrete tank initially contains 440 000 litres liquid and 10 000 kg fine suspended solids. To flush this material out of the tank, water is pumped into the vessel at a rate of 40 000 litres h^{- 1}. Liquid containing solids leaves at the same rate. Estimate the concentration of suspended solids in the tank at the end of 5 h._______________________.

#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.