Simulation of an iterative learning control system for fed-batch cell culture processes

This paper describes an iterative learning control scheme for fed-batch operation where repetitive trajectory tracking tasks are required. The proposed learning strategy is model-independent, and it takes advantage of the repetitive feature of system operations with a certain degree of intelligence and requires only small size of dynamic database for the learning process. The convergence of the learning process is proven. An example of simultaneously tracking two predefined trajectories by iterative learning control with two control inputs is given to illustrate the methodology. Satisfactory performance of the learning system can be observed from the simulation results.     

Model based calculation of substrate/inducer feed-rate profiles in fed-batch processes for recombinant protein production

A model-based feed-rate profile optimization problem is discussed for the fed-batch recombinant protein production. Two optimization procedures, an evolutionary programming technique and a simplified method using the dynamic programming concept, are discussed and compared. Modeling as well as experimental results are presented.     

Simultaneous production of propionic acid and vitamin B12 from corn stalk hydrolysates by Propionibacterium freudenreichii in an expanded bed adsorption bioreactor

Abstract

Vitamin B12 and propionic acid that were simultaneous produced by Propionibacterium freudenreichii are both favorable chemicals widely used in food preservatives, medicine, and nutrition. While the carbon source and propionic acid accumulation reflected fermentation efficiency. In this study, using corn stalk as a carbon source and fed-batch fermentation process in an expanded bed adsorption bioreactor was studied for efficient and economic biosynthesis of acid vitamin B12 and propionic. With liquid hot water pretreated corn stalk hydrolysates as carbon source, 28.65?mg L^?1 of vitamin B12 and 17.05?g L^?1 of propionic acid were attained at 168?h in batch fermentation. In order to optimize the fermentation outcomes, fed-batch fermentation was performed with hydrolyzed corn stalk in expanded bed adsorption bioreactor (EBAB), giving 47.6?mg L^?1 vitamin B12 and 91.4?g L^?1 of propionic acid at 258?h, which correspond to product yields of 0.37?mg g^?1 and 0.75?g g^?1, respectively. The present study provided a promising strategy for economically sustainable production of vitamin B12 and propionic acid by P. freudenreichii fermentation using biomass cornstalk as carbon source and expanded bed adsorption bioreactor.     

Effects of feeding and induction strategy on the production of BmR1 antigen in recombinant E. coli

Aim:  To investigate the effects of feeding and induction strategies on the production of Bm R1 recombinant antigen.
Methods and Results:  Fed-batch fermentation was studied with respect to the specific growth rate and mode of induction to assess the growth potential of the bacteria in a bioreactor and to produce high yield of Bm R1 recombinant antigen. Cells were grown at a controlled specific growth rate (μ_set) during pre-induction, followed by constant feeding postinduction. The highest biomass (24·3 g l⁻¹) was obtained during fed-batch process operated at μ_set of 0·15 h⁻¹, whereby lower μ_set (0·075 h⁻¹) gave the highest protein production (9·82 mg l⁻¹). The yield of Bm R1 was increased by 1·2-fold upon induction with 1 mmol l⁻¹ IPTG (isopropyl-β- d -thiogalactoside) compared to using 5 mmol l⁻¹ and showed a further 3·5-fold increase when the culture was induced twice at the late log phase.
Conclusions:  Combination of feeding at a lower μ_set and twice induction with 1 mmol l⁻¹ IPTG yielded the best result of all variables tested, promising an improved method for Bm R1 production .
Significance and Impact of the Study:  This method can be used to increase the production scale of the Bm R1 recombinant antigen to meet the increasing demand for Brugia Rapid^™, a commercial diagnostic test for detection of brugian filariasis.     

On-line Measurements and Control of Viable Cell Density in Cell Culture Manufacturing Processes using Radio-frequency Impedance

In this work, radio-frequency (RF) impedance is reviewed as a method for monitoring and controlling cell culture manufacturing processes. It is clear from the many publications cited that RF Impedance is regarded as an accurate and reliable method for measuring the live cell bio-volume both on-line and off-line and the technology is also sutable for animal cells in suspension, attached to micro-carriers or immobilized in fixed beds. In cGMP production, RF Impedance is being used in three main areas. Firstly, it is being used as a control instrument for maintaining consistent perfusion culture allowing the bioreactor to operate under optimum conditions for maximum production of recombinant proteins. In the second application it has not replaced traditional off-line live cell counting techniques but it is being used as an additional monitoring tool to check product conformance. Finally, RF Impedance is being used to monitor the concentration of live cells immobilized on micro-carriers or packed beds in cGMP processes where traditional off-line live cell counting methods are inaccurate or impossible to perform.     

Cloning, characterization ofPichia etchellsii β-glucosidase II and effect of media composition and feeding strategy on its production in a bioreactor

The cloning and expression of β-glucosidase II, encoded by the geneßglu2, from thermotolerant yeastPichia etchellsii intoEscherichia coli is described. Cloning of the 7.3 kbBamHI/SalI yeast insert containingßglu2 in pUC18, which allowed for reverse orientation of the insert, resulted in better enzyme expression. Transformation of this plasmid intoE. coli JM109 resulted in accumulation of the enzyme in periplasmic space. At 50°C, the highest hydrolytic activity of 1686 IU/g protein was obtained on sophorose. Batch and fed-batch techniques were employed for enzyme production in a 14 L bioreactor. Exponential feeding rates were determined from mass balance equations and these were employed to control specific growth rate and in turn maximize cell growth and enzyme production. Media optimization coupled with this strategy resulted in increased enzyme units of 1.2 kU/L at a stabilized growth rate of 0.14 h^?1. Increased enzyme production in bioreactor was accompanied by formation of inclusion bodies.     

Fermentation strategies for recombinant protein expression in the methylotrophic yeastPichia pastoris

Fermentation strategies for recombinant protein production inPichia pastoris have been investigated and are reviewed here. Characteristics of the expression system, such as phenotypes and carbon utilization, are summarized. Recently reported results such as growth model establishment, application of a methanol sensor, optimization of substrate feeding strategy, DOstat controller design, mixed feed technology, and perfusion and continuous culture are discussed in detail.