#Question id: 14245

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, Y_PX is 3.9 kg kg^-1 and µ_max 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; µ_max 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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