Online automatic tuning and control for fed-batch cultivation

Performance of controllers applied in biotechnological production is often below expectation. Online automatic tuning has the capability to improve control performance by adjusting control parameters. This work presents automatic tuning approaches for model reference specific growth rate control during fed-batch cultivation. The approaches are direct methods that use the error between observed specific growth rate and its set point; systematic perturbations of the cultivation are not necessary. Two automatic tuning methods proved to be efficient, in which the adaptation rate is based on a combination of the error, squared error and integral error. These methods are relatively simple and robust against disturbances, parameter uncertainties, and initialization errors. Application of the specific growth rate controller yields a stable system. The controller and automatic tuning methods are qualified by simulations and laboratory experiments with Bordetella pertussis

Specific Growth Rate And Sliding Mode Stabilization Of Fed-Batch Processes

The subject of this paper is specific growth rate control of a fed-batch biotechnological process. The objective of the paper is to present comfortable tools and mathematical methodology that permits control stabilization of biotechnological processes with synchronized utilization of different mathematical approaches. The control design is based on the equivalent transformations to Brunovsky normal form of an enlarged Monod-Wang model, on a chattering optimal control and sliding mode control solutions. This approach permits new precise control solutions for stabilization of continuous and fed-batch cultivation processes. In the paper are investigated Monod-Wang kinetic model and it singular Monod form. The simpler Monod and Monod-Wang models are restricted forms of Wang-Yerusalimsky model. The Wang-Yerusalimsky kinetic model could be accepted as a common model. A second order sliding mode is investigated and compared with standard sliding mode algorithms. The sliding mode control permits to solve the control problems with smaller quantity of priory information and elimination of parameters and measurements noises

Scaling-up vaccine production: implementation aspects of a biomass growth observer and controller

Abstract This study considers two aspects of the implementation of a biomass growth observer and specific growth rate controller in scale-up from small- to pilot-scale bioreactors towards a feasible bulk production process for whole-cell vaccine against whooping cough. The first is the calculation of the oxygen uptake rate, the starting point for online monitoring and control of biomass growth, taking into account the dynamics in the gas-phase. Mixing effects and delays are caused by amongst others the headspace and tubing to the analyzer. These gas phase dynamics are modelled using knowledge of the system in order to reconstruct oxygen consumption. The second aspect is to evaluate performance of the monitoring and control system with the required modifications of the oxygen consumption calculation on pilot-scale. In pilot-scale fed-batch cultivation good monitoring and control performance is obtained enabling a doubled concentration of bulk vaccine compared to standard batch productio

Strategy for improving extracellular lipolytic activities by a novel thermotolerant Staphylococcus sp. strain

<p>Abstract</p> <p>Background</p> <p>Extracellular bacterial lipases received much attention for their substrate specificity and their ability to function under extreme environments (pH, temperature...). Many staphylococci produced lipases which were released into the culture medium. Reports of extracellular thermostable lipases from <it>Staphylococcus </it>sp. and active in alkaline conditions are not previously described.</p> <p>Results</p> <p>This study focused on novel strategies to increase extracellular lipolytic enzyme production by a novel <it>Staphylococcus </it>sp. strain ESW. The microorganism needed neutral or alkaline pH values between 7.0 and 12.0 for growth. For pH values outside this range, cell growth seemed to be significantly inhibited. <it>Staphylococcus </it>sp. culture was able to grow within a wide temperature range (from 30 to 55°C). The presence of oils in the culture medium leaded to improvements in cells growth and lipolytic enzyme activity. On the other hand, although chemical surfactants leaded to an almost complete inhibition of growth and lipolytic enzyme production, their addition along the culture could affect the location of the enzyme. In addition, our results showed that this novel <it>Staphylococcus </it>sp. strain produced biosurfactants simultaneously with lipolytic activity, when soapstock (The main co-product of the vegetable oil refining industry), was used as the sole carbon source.</p> <p>Conclusion</p> <p>A simultaneous biosurfactant and extracellular lipolytic enzymes produced bacterial strain with potential application in soap stock treatment</p

Estimation of biomass concentration using interval observers in an E. coli fed-batch fermentation

In bioreactors, the measurement of variables that play a key role in the quality and productivity of fermentations, is of major importance. However, their direct measurement is often expensive or even impossible considering the current sensor technology. Therefore, on-line estimation of unmeasured variables in bioreactors can be an interesting approach. The objective of this work is to introduce an alternative solution for the observation of biomass concentration in E. coli fed-batch fermentations, in cases where the kinetic model is unclear and several variables, like the concentration of the influent substrates and the initial values of the state variables are badly known, a situation that is common in many practical applications. The simple interval observer is designed on the basis of the cooperativity properties of the observer error dynamics (Rapaport and Dochain, 2005). The performance of the interval observer is illustrated through numerical simulation and it was found that the observer deal well with uncertainties up to 50% and with white noise in the variables measured on-line. The interval obtained for the biomass estimation is also quite narrow, indicating that it is possible to accurately predict biomass concentration under the presence of uncertainties.Programa de Desenvolvimento Educativo para Portugal (PRODEP)Fundação para a Ciência e a Tecnologia (FCT) - Projecto recSysBio POCI/BIO/60139/200

Implementation of a specific rate controller in a fed-batch E. coli fermentation

The specific growth rate is one of the most important process variables characterizing the state of microorganisms during fermentations mainly because the biosynthesis of many products of interest is often related with the values assumed by this parameter. In the particular case of the fed-batch operation of Escherichia coli for the production of recombinant proteins, it is important to maintain the specific growth rate below a certain threshold in order to avoid the accumulation of acetic acid throughout the fermentation and, additionally, it is often argued that both pre- and the post-induction specific growth rates should be closely controlled in order to achieve maximum productivities of the desired recombinant protein. In a previous work the authors have developed and validated by simulations a strategy for the automatic control of the specific growth rate in E. coli fed-batch fermentations based on an asymptotic observer for biomass and on developed estimators for the specific growth rates. The main purpose of the present work was to implement experimentally the developed observer, estimator and controller in a real fed-batch fermentation process. For that purpose a data acquisition and control program was developed in LabVIEW that allows the acquisition of the necessary on line data (off gas and dissolved oxygen concentration and culture weight) and the calculation of the feeding rates using the developed equations. The feedforward-feedback controller developed was able to keep the culture growing in an exponential phase throughout the fermentation without accumulation of glucose and acetate.Fundação para a Ciência e a Tecnologia (FCT) - RecSysBio projecto POCI/BIO/60139/200

Specific growth rate regulation in a simulated fed-batch E. coli fermentation

The specific growth rate is one of the most important process variables characterizing the state of microorganisms during fermentations mainly because the biosynthesis of many products of interest is often related with the values assumed by this parameter. In the particular case of the fed-batch operation of Escherichia coli for the production of recombinant proteins, it is often argued that both pre- and the post-induction specific growth rates should be closely controlled in order to achieve maximum productivities on the desired recombinant protein. In this work a feedforward-feedback controller was developed with the purpose of regulating the global specific growth rate during a fed-batch fermentation of E. coli. The developed algorithm allows to maintain the cells in two different metabolic regimens (simultaneous oxidative and fermentative growth on glucose or oxidative growth on glucose), depending on the selected setpoint for the controlled variable. The pure open-loop version of the controller revealed a relatively poor performance when dealing with process noise. However, the introduction of on-line measurements of fermenter weight and biomass estimation obtained from asymptotic observers allowed a better approximation between the desired setpoints and the simulated values of the specific growth rates. Finally, the introduction of a proportional action in the controller equation allows an improved robustness against variations in model parameters.Fundação para a Ciência e a Tecnologia (FCT) - POCI/BIO/60139/2004

Monitoring of fed-batch E. coli fermentations with software sensors

Accurate monitoring and control of industrial bioprocess requires the knowledge of a great number of variables, being some of them not measurable with standard devices. To overcome this difficulty, software sensors can be used for on-line estimation of those variables and, therefore, its development is of paramount importance. An Asymptotic Observer was used for monitoring Escherichia coli fed-batch fermentations. Its performance was evaluated using simulated and experimental data. The results obtained showed that the observer was able to predict the biomass concentration profiles showing, however, less satisfactory results regarding the estimation of glucose and acetate concentrations. In comparison with the results obtained with an Extended Kalman Observer, the performance of the Asymptotic Observer in the fermentation monitoring was slightly better.recSysBioPrograma de Desenvolvimento Educativo para Portugal III (PRODEP