Design and Application of Intelligence Algorithms in Continuous Fermentation of Glycerol

Guoli Wu,Zongli Ruan,Juan Wang

doi:10.1109/access.2021.3114323

Guoli Wu, Zongli Ruan + Show 1 more

Open Access

https://doi.org/10.1109/access.2021.3114323

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Abstract

The bioconversion of 1,3-propanediol from glycerol by Klebsiella pneumoniae can be described by a nonlinear dynamic system. Some work has been done on the identification and optimization of the system, in which the dilution rate of glycerol is considered as a constant. However, the demand of glycerol may vary at different fermentation stages, it is reasonable to view the glycerol metabolic system with dilution rate varying with time. In this paper, we model the glycerol metabolic process as a fourteen-dimensional nonlinear dynamical system, where the dilution rate is considered varying with time. Then an optimal discrete-valued control problem for maximizing the average concentration of 1,3-propanediol in the fermentation process is established. To solve the optimization problem, auxiliary control and an exact penalty function are used to convert this problem into a large-scale parameter optimization problem. For better balancing local and global search ability, a competitive particle swarm algorithm with time-varying control factors is proposed which is proved to be faster and more stable than the traditional competitive particle swarm algorithm. Numerical experiments are conducted to show the rationality, effectiveness and applicability of the method proposed.

Highlights

NONLINEAR HYBRID DYNAMICAL SYSTEM According to the factual experiments, we assume that (H1) Glycerol is the only substrate that added to the reactor during the process of continuous culture, and no medium is pumped inside or outside the reactor in the whole process. (H2) The concentrations of reactants are uniform in the reactor, time delay and nonuniform space distribution are ignored
The velocity field of concentration changes during the process of glycerol continuous fermentation is formulated as follows according to the previous work [6]: x1(t) = ( (t) − d(t))x1(t), (1)
The largest Fitness value and the least runtime mean that CPSOT has good solving accuracy and fast speed

Summary

NONLINEAR HYBRID DYNAMICAL SYSTEM

According to the factual experiments, we assume that (H1) Glycerol is the only substrate that added to the reactor during the process of continuous culture, and no medium is pumped inside or outside the reactor in the whole process. (H2) The concentrations of reactants are uniform in the reactor, time delay and nonuniform space distribution are ignored. According to the results of [6,17], we assume that glycerol passes the membrane by passive diffusion and 1,3-PD by passive diffusion coupled with active transport, and the inhibition of 3-HPA on cell growth (GDHt activity, PDOR activity) exists at any concentration of 3-HPA Under these assumptions, the velocity field of concentration changes during the process of glycerol continuous fermentation is formulated as follows according to the previous work [6]: x1(t) = ( (t) − d(t))x1(t),. Where, m is the maximum specific growth rate, Pi (i = 1, 2, ,15) are extracellular kinetic parameters, and xi* (i = 2,3, 4,5) are critical concentrations

OPTIMAL CONTROL PROBLEM AND REFORMULATION

PROBLEM REFORMULATION

DISCRETIZATION

A COMPETITIVE PARTICLE SWARM ALGORITHM

NUMERICAL EXAMPLE AND RESULTS

CONCLUSION