Growth Rate In Fed-batch Culture Research Articles

Large‐scale production of endotoxin‐free plasmids for transient expression in mammalian cell culture

Transient expression of recombinant proteins in mammalian cell culture in a 100-L scale requires a large quantity of plasmid that is very labour intensive to achieve with shake flask cultures and commercially available plasmid purification kits. In this paper we describe a process for plasmid production in 100-mg scale. The fermentation is carried out in a 4-L fed-batch culture with a minimal medium. The detection of the end of batch and triggering the exponential (0.1 h(-1)) feed profile was unattended and controlled by Multi-fermenter Control System. A restricted specific growth rate in fed-batch culture increased the specific plasmid yield compared to batch cultures with minimal and rich media. This together with high biomass concentration (68-107 g L(-1) wet weight) achieves high volumetric yields of plasmid (95-277 mg L(-1) depending on the construct). The purification process consisted of alkaline lysis, lysate clarification and ultrafiltration, two-phase extraction with Triton X-114 for endotoxin removal, anion-exchange chromatography as a polishing step, ultrafiltration and sterile filtration. Both fermentation and purification processes were used without optimisation for production of four plasmids yielding from 39 to 163 mg of plasmids with endotoxin content of 2.5 EU mg(-1) or less.

A pseudo-exponential feeding method for control of specific growth rate in fed-batch cultures

A simple feeding method for controlling specific growth rate in fed-batch culture was developed. This method applies a constant feed rate using a concentrate reservoir and two mixing chambers in series to simulate the exponential feeding. Fed-batch cultures with Escherichia coli showed that the present feeding method could sustain the cells growing at predetermined specific growth rates, where the time length for exponential growth was dependent on the magnitude of the growth rate. The present feeding method is convenient to operate, requires no computerized control equipments, and thus could expect an extensive application in fed-batch culture.

Simulation and Experimental Studies of the Profile Control of the Specific Growth Rate in a Fed-batch Culture

The aim of this paper is to develop and discuss a practically useful system so that the specific growth rate in a baker's yeast fed-batch cultute will follow the desired profile specified in advance as accurately as possible. For this, first, the specific growth rate should be estimated using indirect measurement of the overall growth rate or using online data of cell concentration. Based on the careful analysis of the previously proposed method, an improved method was proposed which uses moving averages and dynamic mass balancing. It was shown that the specific growth rate could be estimated with sufficient accuracy using an extended Kalman filtering algorithm using the estimated overall growth rate, or using the cell concentration. Secondly, the control scheme called "Prograrruned-controller/Feedback-compensator(PF) system " consists of a prograrruned controller and a feedback compensator has been used for the profile control of μ. The PF-MRAC in which the model reference adaptive controller was used for the compensator, was shown to be effective for this purpose. Finally, the profile control of the specific growth rate in a baker's yeast fed-batch culture was realized experimentally using the proposed control scheme. The experiments showed that the estimation and control schemes proposed were sufficiently useful.