Abstract
BackgroundThe efficiency of biotechnological production processes depends on selecting the best performing microbial strain and the optimal cultivation conditions. Thus, many experiments have to be conducted, which conflicts with the demand to speed up drug development processes. Consequently, there is a great need for high-throughput devices that allow rapid and reliable bioprocess development. This need is addressed, for example, by the fiber-optic online-monitoring system BioLector which utilizes the wells of shaken microtiter plates (MTPs) as small-scale fermenters. To further improve the application of MTPs as microbioreactors, in this paper, the BioLector technology is combined with microfluidic bioprocess control in MTPs. To realize a user-friendly system for routine laboratory work, disposable microfluidic MTPs are utilized which are actuated by a user-friendly pneumatic hardware.ResultsThis novel microfermentation system was tested in pH-controlled batch as well as in fed-batch fermentations of Escherichia coli. The pH-value in the culture broth could be kept in a narrow dead band of 0.03 around the pH-setpoint, by pneumatically dosing ammonia solution and phosphoric acid to each culture well. Furthermore, fed-batch cultivations with linear and exponential feeding of 500 g/L glucose solution were conducted. Finally, the scale-up potential of the microscale fermentations was evaluated by comparing the obtained results to that of fully controlled fermentations in a 2 L laboratory-scale fermenter (working volume of 1 L). The scale-up was realized by keeping the volumetric mass transfer coefficient kLa constant at a value of 460 1/h. The same growth behavior of the E. coli cultures could be observed on both scales.ConclusionIn microfluidic MTPs, pH-controlled batch as well as fed-batch fermentations were successfully performed. The liquid dosing as well as the biomass growth kinetics of the process-controlled fermentations agreed well both in the microscale and laboratory scale. In conclusion, a user-friendly and disposable microfluidic system could be established which allows scaleable, fully controlled and fully monitored fermentations in working volumes below 1 milliliter.
Highlights
The efficiency of biotechnological production processes depends on selecting the best performing microbial strain and the optimal cultivation conditions
Besides the test of this novel, user-friendly system in pH-controlled batch as well as in fed-batch fermentations of Escherichia coli, this paper describes the scaleup of the microfermentations and the comparison of the obtained results in the microfluidic microtiter plates (MTPs) to fermentations in a 2 L laboratory-scale fermenter
The newly developed single-use microfluidic MTP and the interaction with its new actuator hardware was tested in pH-controlled batch (Figures 4 and 5) as well as fed-batch fermentations (Figure 6) of Escherichia coli K12 in minimal medium
Summary
The efficiency of biotechnological production processes depends on selecting the best performing microbial strain and the optimal cultivation conditions. State-of-the-art bioprocesses are based on a large number of small-scale experiments in which the best performing microbial strain and the optimal cultivation conditions are evaluated These screening experiments are becoming even more important, since modern methods in genetic engineering and molecular biology can need for high-throughput small-scale cultivation systems increases. To place their application as shaken microbioreactors on a firm footing, intense efforts have been made to characterize fluid movement, gas transfer, energy input and mixing in these vessels [reviewed in: [11,12,13]] This characterization work and the developed methods build the fundament to improve the MTPs as described by Funke et al [14]. This new MTP-well geometry, the Flowerplate (m2p-labs GmbH; Aachen, Germany), is applied in this current work
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