On-line state estimation of biomass based on acid production in Zymomonas mobilis cultures

Abstract

The concentrations of biomass, substrate and product are very important state variables of almost every bioprocess and generally unable to be measured directly in situ due to the lack of reliable sensors. In this paper, an adaptive observer of the biomass concentration is proposed for an anaerobic fermentation process where only the measurement of the acid product is available on-line. The observer was tested to be effective by several experiments under various operating conditions. In this experimental system, an auto-sampling device was connected between the bioreactor for the fermentation of Zymomonas mobilis and a HPLC so that the concentrations of glucose and ethanol could be directly measured through such implementation.

Biomass measurement online: the performance of in situ measurements and software sensors

“…The most popular correlation method is the use of oV-gas analysis in biomass estimation [11,15,18,48,64]. Measurements of chemical properties of the medium such as pH, conductivity, or the demand of pH control agents have also been used in estimating biomass concentrations [1,25,67]. Also physical properties of the culture such as broth viscosity have been combined with biomass measurements [6,68].…”

“…Another popular way for biomass estimation has emerged from state estimation and process control theory in the form of adaptive state estimators. These models are often based on simple Wrst-order rate equations and continuous parameter estimation (or tuning) protocols [35,67]. A common drawback with kinetics-based biomass estimators is the assumption of constant coeYcients.…”

Identification of a fed-batch fermentation process: comparison of computational and laboratory experiments

“…the class of unknown dynamic systems under consideration is a plant extension which includes ones given by ordinary nonlinear differential equations with a relatively smooth regular part; 2. the class of the model structures used for identi®cation purposes includes the DNN in which weights are adjusted on-line by a special``differential learning procedure'' (12).…”

“…Because of the complexity and high nonlinearity of analyzed systems, it is required to obtain the kinetic parameter estimates of the bioreactors [11,12], which obviously demands the construction of on-line models in continuous or in discrete time [13,14]. In [6,15] it was shown by simulation that the use of static NN to predict some key variables in a fermentation process guaranteed a low degree of observation noise in such estimates.…”

On-line estimation of biomass and intracellular protein for recombinant Escherichia coli cultivated in batch and fed-batch modes

“…Biomass is a critical parameter in the fermentation process, and it is difficult to be measured (Madrid and Felice, 2005;Vanek et al, 2004;Vicente et al, 1998;Wang et al, 1998). It is important because it is a key variable in the optimization of a specific process, or to reach a maximum efficiency to obtain a certain product, i.e., an antibiotic and recombinant protein.…”