A biological process for the production of 1,3-propanediol by Klebsiella pneumonia
A new polyester made with 1,3-propanediol, polytrimethylene terephthalate (PTT), is of great commercial interest because of PTT's excellent properties in textile and fiber industries. Current commercial routes to produce 1,3-propanediol are chemical synthetical methods from acrolein or ethylene oxide. The interest in investigating the biochemical processes to produce 1,3-propanediol originates from the idea of utilizing inexpensive, renewable resources like glucose to produce industrial chemicals, which provides solutions to environmental pollution and possible depletion of petroleum and natural gas. Our specific objective is to develop a two-step biological process to produce 1,3-propanediol by using glucose and to investigate culture conditions that lead to high 1,3-propanediol concentrations, yields and productivities by batch and fed-batch fermentations. A strain was screened from the wild type of Klebsiella pneumoniae ATCC 25955 to be cultured under mild aerobic fermentation by using raw glycerol instead of strictly anaerobic conditions as reported in previous 1,3-propanediol fermentation literatures. A creative pH fluctuation process was applied to control unwanted byproduct concentrations and improve the final 1,3-propanediol concentrations and yields. The highest final concentration of 1,3-propanediol achieved in this report was 70 g/l; the yield was 0.6 mol/mol; the two main byproducts, lactic acid and 2,3-butanediol were as low as 10 g/l or so; and the residual glycerol was nearly zero. This is one of the best results among current reported research work on 1,3-propanediol. Furthermore, a mathematical model about inhibition effect has been developed and compared with experimental data for better understanding the microorganism growth and the 1,3-propanediol production, which is a typical growth-rated product. Therefore, the critical concentrations discussed in the models have been specified based on the experiment data and model simulations, which give the corresponding critical concentrations as C*Gly = 150 g/l; C*PD = 83 g/l; C*Lac = 70 g/l; C*BD = 90 g/l; C* EtOH = 32 g/l. ^
Major Professor: George T. Tsao, Purdue University.
Biology, Microbiology|Engineering, Chemical