4.12 Production of1,3-propanediol
A process for microbial synthesisof 1,3-propanediol is being developed for the manufacture of'green' polyester fabric from renewable resources. Under anaerobicconditions, a selected strain of Klebsiella pneumoniae convertsglycerol ((231-1803) to 1,3-propanedi01 (C3H802) and acetic acid(C2H402), with minimal formation of other fermentation productssuch as butyric acid, ethanol, and 1-12 gas. The fermentation andcell growth equation can be written as:
                68 C3H803 + 3 NH3 = 3 C4H702N + 49 C3H802 + 15 C2H402 + 15 C02 + 40H20
where C4H702N represents thebiomass.
A continuous fermenter is set up for1,3-propanediol production at 37o c and atmosphericpressure. Anaerobic conditions are maintained by sparging the brothwith nitrogen gas at a flow rate of 1000 litres min—I. The feedrate of medium into the fermenter is 1000 kg h—l; the mediumcontains ammonia and 14% w/ w glycerol. The yield of 1,3propanediolis strongly affected by glycerol concentration, which must be keptabove a certain level to suppress the formation of undesiredby-products. Accordingly, the fermentation process is designed sothat the product stream contains an unreacted glycerolconcentration of 3% w/ w.
A: What is the volumetric flow rateand composition of the off-gas?
B: What minimum concentration of NH3 is needed in the feedstream?
C: If the NH3 concentration from (b) is used, what is theconcentration of 1,3-propanediol in the product stream?
