Single-use rocking-motion-type bag bioreactors provide advantages compared to standard stirred tank bioreactors by decreased contamination risks, reduction of cleaning and sterilization time, lower investment costs, and simple and cheaper validation. Currently, they are widely used for cell cultures although their use for small and medium scale production of recombinant proteins with microbial hosts might be very attractive. However, the utilization of rocking- or wave-induced motion-type bioreactors for fast growing aerobic microbes is limited because of their lower oxygen mass transfer rate. A conventional approach to reduce the oxygen demand of a culture is the fed-batch technology. New developments, such as the BIOSTAT CultiBag RM system pave the way for applying advanced fed-batch control strategies also in rocking-motion-type bioreactors. Alternatively, internal substrate delivery systems such as EnBase Flo provide an opportunity for adopting simple to use fed-batch-type strategies to shaken cultures. Here, we investigate the possibilities which both strategies offer in view of high cell density cultivation of E. coli and recombinant protein production.
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Rocking-motion-type bioreactors may provide an interesting alternative to standard cultivation in bioreactors for cultivation of bacteria and recombinant protein production. The BIOSTAT Cultibag RM system with the single-use sensors and advanced control system paves the way for the fed-batch technology also to rocking-motion-type bioreactors. It is possible to reach cell densities which are far above shake flasks and typical for stirred tank reactors with the improved oxygen transfer rate. For more simple applications the EnBase Flo method offers an easy and robust solution for rocking-motion-systems which do not have such advanced control possibilities.
Recently a simple-to-use cultivation technology has been introduced which extends the advantages of the fed-batch principle to shaken cultures, where external feeding is difficult to achieve. The EnBase platform applies an internal delivery of glucose by biocatalytic degradation of glucose containing polymers [19]. Thus no external pump is necessary and the system is applicable in shaken culture formats. A further development of the method from the initially introduced gel based two-compartment system to entire liquid formulations, named EnBase Flo, provides a higher flexibility; it can be applied in systems with optical sensors and enables scale up [18]. In Enbase, cell growth and oxygen consumption is controlled by the amount of a biocatalyst, similar like the pump rate is adapted in a conventional fed-batch system. The release of glucose by the biocatalyst with a constant rate yields a quasi linear biomass increase, and consequently an approximately stable DOT. Simply by enhancing the biocatalyst, i.e. the glucose release rate, such cultures can be optimized to grow at the limit of the oxygen transfer capacity in the system, corresponding to the maximum possible volumetric growth rate. The controlled growth also reduces side metabolite production and thus provides a stable pH in the culture. Further, optimization of trace elements [20] and addition of complex additives [18] increased the robustness of the system in view of oxygen limitation, expression systems, and target proteins. We suggested that the application of EnBase Flo would also simplify the cultivation process and improve the product yield in rocking-motion-type bioreactors.
This study is to our knowledge the first investigation issuing the use of fed-batch technology for E. coli cultivation and recombinant protein production for rocking-motion-type bioreactors. The study indicates that there is a potential of using rocking-motion-type systems which are limited by a low oxygen transfer rate for elevated biomass production. In view of its control system the CultiBag RM system provides the general features which are typical for standard bioreactors. This allows also the application of more advanced control strategies, such as exponential feeding procedures and feed-back control of the pO2. Pulsing of extra oxygen provides some advantage in overcoming the low oxygen transfer rates.
A wide interest for using rocking-motion-type bioreactors is especially expected in facilities which do not have simple access to, or experience with, bioreactor facilities. Enbase Flo provides a simple alternative for a high cell density type of cultivation without the need for the user to be a specialist in fermentation technology. In this system the amount of an enzyme determines the glucose release rate and all optimisation can be done at the microwell or deepwell plate stage. Here we show at the example of ADH that such preoptimised processes simply can be transferred to a rocking-motion-system, without the need for setting up any extra control. This would provide a simple scale up to the 100 scale. On top of this, further modifications can be done for improving the volumetric yield further, e.g. by combining an initial Enbase Flo culture with a subsequent fed-batch of glucose as an external feed, or providing further complex additives as shown in the culture of Fig. 5. Aside from the principal feasibility of Enbase Flo in a rocking-motion-type bioreactor which we demonstrated here, it will be interesting to see whether there is a direct scalability of such a process directly from deepwell plates to the scale of rocking-motion-type systems in a similar way as it was demonstrated recently for the scale up to a stirred tank bioreactor process (see [16, 26]).
The Journal of Food Science and Technology (JFST) is the official publication of the Association of Food Scientists and Technologists of India (AFSTI). This monthly publishes peer-reviewed research papers and reviews in all branches of science, technology, packaging and engineering of foods and food products. Special emphasis is given to fundamental and applied research findings that have potential for enhancing product quality, extend shelf life of fresh and processed food products and improve process efficiency. Critical reviews on new perspectives in food handling and processing, innovative and emerging technologies and trends and future research in food products and food industry byproducts are also welcome. The journal also publishes book reviews relevant to all aspects of food science, technology and engineering. 2ff7e9595c
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