Progress in monitoring, modeling and control of bioprocesses during the last 20 years.

To increase product yields and to ensure consistent product quality, key issues of industrial fermentations, process optimization and scale up are aimed at maintaining optimum and homogenous reaction conditions minimizing microbial stress exposure and enhancing metabolic accuracy. For each individual product, process and facility, suitable strategies have to be elaborated by a comprehensive and detailed process characterization, identification of the most relevant process parameters influencing product yield and quality and their establishment as scale-up parameters to be kept constant as far as possible. Physical variables, which can only be restrictedly kept constant as single parameters, may be combined with other pertinent parameters to appropriate mathematical groups or dimensionless terms. Process characterization is preferably based on real-time or near real-time data collected by in situ and on-line measurements and may be facilitated by supportive approaches and tools like neural network based chemometric data analysis and modelling, clarification of the mixing and stream conditions through computational fluid dynamics and scale-down simulations. However, as fermentation facilities usually are not strictly designed according to scale-up criteria and the process conditions in the culture vessels thus may differ significantly and since any strategy and model can only insufficiently consider and reflect the highly complex interdependence and mutual interaction of fermentation parameters, successful scale up in most cases is not the result of a conclusive and straight-lined experimental strategy, but rather will be the outcome of a separate process development and optimization on each scale. This article gives an overview on the problems typically coming along with fermentation process optimization and scale up, and presents currently applied scale-up strategies while considering future technologies, with emphasis on Escherichia coli as one of the most commonly fermented organisms.

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Optimization and scale up of industrial fermentation processes

This review of process analytical chemistry is an update to the previous review on this subject published in 1995(A2). The time period covered for this review includes publications written or published from late 1994 until early 1999, with the addition of a few classic references pointing to background information critical to an understanding of a specific topic area. These older references have been critically included as established fundamental works. New topics covered in this review not previously treated as separate subjects in past reviews include sampling systems, imaging (via optical spectroscopy), and ultrasonic analysis.

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Process Analytical Chemistry

The ability to measure all process variables is of great importance in the field of bioprocess monitoring and control, and continuous, real-time measurements are highly desired. The more complete and real-time the measurements are, the more stable, reproducible, and efficient the process can be, leading to reproducibly high-quality products. This additional information allows the operator to better document the entire process. The process analytical technologies initiative of the US Food and Drug Administration is strongly related to the analysis and control of biopharmaceutical processes. The aim of the initiative is to create processes, generating products of ensured quality by measuring quality-related process variables. The quality of the product is enhanced by a deep understanding of the process, which is enabled by an effective and suitable sensor system. The aim of this review is to provide an overview of current and emerging sensors for bioprocess monitoring. Sensors directly interfaced to bioreactors for measuring important variables from the gas phase, such as oxygen and carbon dioxide concentration, are discussed, as well as sensors for the monitoring of the biomass concentration and morphology and of the changing medium composition. Furthermore, sensor systems are discussed. These involve sensors (especially biosensors) that are not implemented directly inside the bioreactor but rather are used in conjunction with sample-taking systems such as flow injection analysis. A major focus is given to spectroscopic sensors, which are noninvasive and offer interesting options for a simultaneous analysis of various compounds. Since data handling is extremely important for this kind of sensor, chemometrics are also included. Soft sensors are discussed as technology that allows a user to incorporate more process data as it become available. Finally, the current state of disposable sensor technology is presented. These sensors are needed for the growing area of disposable and continuous biomanufacturing.

Sensor systems for bioprocess monitoring

This review article has been written for the journal, Biotechnology and Bioengineering, to commemorate the 70th birthday of Daniel I.C. Wang, who served as doctoral thesis advisor to each of the co-authors, but a decade apart. Key roots of the current PAT initiative in bioprocess monitoring and control are described, focusing on the impact of Danny Wang's research as a professor at MIT. The history of computer control and monitoring in biochemical processing has been used to identify the areas that have already benefited and those that are most likely to benefit in the future from PAT applications. Past applications have included the use of indirect estimation methods for cell density, expansion of on-line/at-line and on-line/in situ measurement techniques, and development of models and expert systems for control and optimization. Future applications are likely to encompass additional novel measurement technologies, measurements for multi-scale and disposable bioreactors, real time batch release, and more efficient data utilization to achieve process validation and continuous improvement goals. Dan Wang's substantial contributions in this arena have been one key factor in steering the PAT initiative towards realistic and attainable industrial applications. © 2006 Wiley Periodicals, Inc.

Bioprocess monitoring and computer control : Key roots of the current PAT initiative

Fermentation monitoring and control by on-line flow injection and liquid chromatography

Monitoring and control of recombinant protein production

On-line determination of intracellular β-galactosidase activity in recombinant Escherichia coli using flow injection analysis (FIA)

Development of enzyme cartridge flow-injection analysis for industrial process monitoring. Part II. Application for monitoring of microorganism cultivations

SPA::EcoRI fusion protein was produced by Escherichia coli JM103 carrying the multicopy expression plasmid pMTC48, the multicopy repressor plasmid pRK248, and the multicopy protection plasmid pEcoR4 in a 60-L working volume airlift tower loop reactor on M9 minimal medium with glucose. Cell mass concentration, total cell count, number of colony-forming units, specific growth rate, yield coefficient, and metabolite (acetate, pyruvate, succinate, lactate, ethanol) concentrations were monitored during the growth phase and gene expression. Gene expression was induced by temperature shift or chemically by isopropyl-thiogalactosidase in the airlift tower loop reactor (ALTR) at constant cultivation time and in a small stirred tank reactor at different cultivation times. During induction, the cultivation medium was supplemented with concentrated Luria–Bertani (LB) medium. The intracellular enzyme activity was evaluated as a function of the time after the start of the induction. It was found that the reduction of the glucose concentration and increase of the dissolved oxygen concentration reduced the acetate produced and increased the intracellular enzyme activity. © 1993 John Wiley & Sons, Inc.

Fed‐batch cultivation of recombinant escherichia coli JM103 and production of the fusion protein SPA::EcoRI in a 60‐L working volume airlift tower loop reactor

Lutz Brandes

Papers

Fermentation monitoring and control by on-line flow injection and liquid chromatography

Monitoring and control of recombinant protein production

On-line determination of intracellular β-galactosidase activity in recombinant Escherichia coli using flow injection analysis (FIA)

Development of enzyme cartridge flow-injection analysis for industrial process monitoring. Part II. Application for monitoring of microorganism cultivations

Fed‐batch cultivation of recombinant escherichia coli JM103 and production of the fusion protein SPA::EcoRI in a 60‐L working volume airlift tower loop reactor