1. Ethanol (C2H5OH) is produced by a microorganism cultured anaerobically in a chemostat. The empirical biomass formula is CH2O0.45N0.19 under these conditions. The sterile feed contains a "high" concentration (20 mM) of glucose, an excess of ammonium salts, and no ethanol. When the dilution rate is set at 0.1 h-1, the exit stream contains 2 mM glucose and 0.45 g/L biomass. It is safe to assume that ethanol is the only secreted product.
a. Determine the expected concentration of ethanol (mM) in the exit stream.
b. The dilution rate chosen probably does not optimize biomass productivity. Briefly explain how you know this to be the case and speculate on why this dilution rate may have been chosen.