(524b) Oscillatory Amplitudes Regulation Method in 1,3-PD Production By Klebsiella Pneumoniae

Hangzhou Wang^a, Tong Qiu^b, Jinsong Zhao^b,Bingzhen Chen^b*

^aMemorial University, St. John’s, N.L., Canada

^bTsinghua University, Beijing, China

1,3-propanediol (1,3-PD) is an important chemical raw material, and it can be used to produce polyesters, polyether and polyurethanes with excellent properties. Microbial fermentation production has many advantages ^{1, 2} over chemical synthesis of 1,3-PD. But oscillatory behavior was observed in both experiments and mathematical simulation during the continuous fermentation of Klebsiella pneumoniae, in which biomass, product and substrate oscillations exist under certain operating conditions. It was reported that these oscillations were caused by the existence of Hopf bifurcations in the system³. To design a more stable process and achieve high product quality, these operating condition points corresponding to the Hopf singularity ones should be avoided. And in some particular situations, the singularity operation point is located exactly at the maximum concentration point; the oscillation is unavoidable or is prone to generate. In these situations, it is a better way to regulate the oscillatory phenomenon, that is, to reduce the oscillatory amplitude so as to increase process stability to some extent. In this paper, a regulation method of oscillatory amplitudes is proposed so that the oscillatory amplitude can be attenuated when the oscillation itself is unavoidable. The detailed steps for this regulation method of oscillatory amplitudes as follows:

1. Calculate all steady state solutions for the dynamic system⁴.
2. Identify all Hopf singularity points in the steady state curve^{5, 6}.
3. Simulate the oscillatory phenomenon and find the amplitudes under different operation conditions.
4. Establish the relationship model between the amplitudes and operation conditions(such as feed dilution rate, initial concentration of substrate).
5. Use the relationship model to regulate oscillatory amplitudes in process design.

According to the proposed method, with the results of oscillation simulation around the singularity operation condition points, the product concentration oscillatory amplitudes under different operation conditions can be obtained. These calculated amplitude data can be regressed to a smooth amplitude curve. The curve fits the varying tendency of the process, and can represent the relationship between amplitude and operation conditions. As a result, the characteristics of the oscillatory behavior in dynamic process can be studied quantitatively The oscillation behavior can be predicted and regulated so that a process with better stability can be designed.

Keywords: 1,3-PD, Hopf Singularity points, Oscillatory Amplitudes, Process Design and Regulations

References

1.      Wong, C.-L.; Huang, C.-C.; Chen, W.-M.; Chang, J.-S., Converting crude glycerol to 1,3-propandiol using resting and immobilized Klebsiella sp. HE-2 cells. Biochemical Engineering Journal 2011,58–59, (0), 177-183.

2.      Menzel, K.; Zeng, A. P.; Deckwer, W. D., High concentration and productivity of 1,3-propanediol from continuous fermentation of glycerol by Klebsiella pneumoniae. Enzyme and Microbial Technology 1997,20, (2), 82-86.

3.      Sridhar, L. N., Elimination of Oscillations in Fermentation Processes. AIChE Journal 2011,57, (9), 2397-2405.

4.      Wang, H.; Chen, B.; He, X.; Zhao, J.; Qiu, T., Numerical Analysis Tool for Obtaining Steady-State Solutions and Analyzing Their Stability Characteristics for Nonlinear Dynamic Systems. Journal of Chemical Engineering of Japan 2010,43, (4), 394-400.

5.      Wang, H.; Zhang, N.; Qiu, T.; Zhao, J.; He, X.; Chen, B., Analysis of Hopf Points for a Zymomonas mobilis Continuous Fermentation Process Producing Ethanol. Industrial & Engineering Chemistry Research 2012,52, (4), 1645-1655.

6.      Wang, H.; Zhang, N.; Qiu, T.; Zhao, J.; He, X.; Chen, B., A process design framework for considering the stability of steady state operating points and Hopf singularity points in chemical processes. Chemical Engineering Science 2013,99, (0), 252-264.

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* Corresponding author. Tel.: +86 10 62781499;fax: +86 10 62770304.

E-mail address: dcecbz@tsinghua.edu.cn  (Bingzhen Chen)