Bioprocess Optimization And Pilot-scale Experiment For 1,3-Propanediol Production By Fermentation

In this paper, the bioprocess for bioconversion of giycerol into 1,3-propanediol was studied in anaerobic fed-batch fermentations by Klebsiella pneumoniae. The effects of different giycerol materials on cell growth and product formation during fermentations are investigated, and the experimental results show that: the saponified giycerol without purification has a relatively strong inhibition on cell growth, and only the saponified giycerol after purifications can be used as material. If the giycerol with high purity, i.e. more than 95%, is used as the material, the highest concentration of 1,3-propanediol and conversion ratio can be gained. Although all indexes using the raw fermentation giycerol to produce 1,3-propanediol are lower than pure giycerol , the two-step fermentation using starch as material is feasible due to its lower production cost. Furthermore, the control strategy combined coupling pH and continuous feeding giycerol in fed-batch fermentation is proposed. This strategy is proved to be valid on the automatic control of the giycerol concentration in the fermentation broth.Based on the lab-scale experiment, the pilot-scale anaerobic fermentations for 1,3-propanediol production are carried in a lm~3 fermentation tank. The concentrations of 1,3-propanediol are all above 70g/L in these fermentation broths, with the highest level of 78.5g/L;the average mass conversion ratio of 50.6%;the average fermentation time of 29.7h;and the average productivity of 2.53g/(L.h). The pilot-scale experiments validate the feasibility of the lab-scale control strategy. The final product of 1,3-propanediol with purity above 99% is obtained by separation and purification. The quality of which also can achieve the polymer grade proved by polymerization experiment.In the end, based on the pilot-scale experiment, it also discusses about the production cost and the anticipated economic benefit with regard to a set of equipments which could produce 1500 tons 1,3-propanediol from giycerol per year. The gross investment is 68.7631 millions Yuan, the unit production cost is 24797 Yuan and the net profit is 15.01 millions Yuan per year.