Fully automated single-use stirred-tank bioreactors for parallel microbial cultivations

Abstract

Single-use stirred tank bioreactors on a 10-mL scale operated in a magnetic-inductive bioreaction block for 48 bioreactors were equipped with individual stirrer-speed tracing, as well as individual DO- and pH-monitoring and control. A Hall-effect sensor system was integrated into the bioreaction block to measure individually the changes in magnetic field density caused by the rotating permanent magnets. A restart of the magnetic inductive drive was initiated automatically each time a Hall-effect sensor indicates one non-rotating gas-inducing stirrer. Individual DO and pH were monitored online by measuring the fluorescence decay time of two chemical sensors immobilized at the bottom of each single-use bioreactor. Parallel DO measurements were shown to be very reliable and independently from the fermentation media applied in this study for the cultivation of Escherichia coli and Saccharomyces cerevisiae. The standard deviation of parallel pH measurements was pH 0.1 at pH 7.0 at the minimum and increased to a standard deviation of pH 0.2 at pH 6.0 or at pH 8.5 with the complex medium applied for fermentations with S. cerevisiae. Parallel pH-control was thus shown to be meaningful with a tolerance band around the pH set-point of +/- pH 0.2 if the set-point is pH 6.0 or lower.

Small-Scale Bioreactors for the Culture of Embryonic Stem Cells

“…This sample was read by a microtitre plate fluorescence reader, in which the optical density was correlated to cell density. The growth characteristics of E. coli and S. cerevisiae were similar at the 10 mL and 20 L scale (Kusterer et al 2008). The above system has recently been modified with a new impeller for the culture of mycelium forming microorganisms.…”

“…In addition, surface tension effects are more pronounced in shaken systems than in stirred configurations . Recently, many of the smallscale systems in literature have been changed from initial shaken models to a stirred design (Gill et al 2008;Islam et al 2007;Kusterer et al 2008;Weuster-Botz et al 2005). There are many inconsistencies in the literature on the definition of a microbioreactor.…”

“…Maintaining sterility has also been noted as an obstacle to parallelization, in particular during culture sampling. Kusterer et al found that washing the components encountering sampling needles with a mixture of 70% ethanol (v/v) and 20% acetone (v/v) to be sufficient (Kusterer et al 2008). However, cross-contamination between samples must also be avoided where each vessel must be treated as an individual sample with individual sampling ports.…”

“…Most small-scale bioreactors found in the literature are not yet amenable to high-throughput analysis while maintaining consistent hydrodynamic environments as a stirred standard scale bioreactor. Gill et al 2008 Standard (100 mL) 4-16 Kusterer et al 2008 Minibioreactor (12 mL) 48 Isett et al 2007 Minibioreactor (6 mL) 24 Girard et al 2001 Minibioreactor (2 mL) 12-144 Legmann et al 2009 Microbioreactor (700 μL) 180 Table 2. Parallel Application of Small-Scale Bioreactors.…”

A two-stage biological gas to liquid transfer process to convert carbon dioxide into bioplastic

“…Dissolved oxygen (DO) and pH were monitored by fluorimetric sensors immobilized at the bottom of each single-use bioreactor (Kusterer et al, 2008) withdrawn automatically with the liquid handling system at preset process times and were used for the determination of bacterial growth and of concentrations of acetic acid. The oxygen transfer rate was kept sufficiently high by using gas-inducing stirrers (Hortsch & Weuster-Botz, 2010) operated at an agitation speed of 2,800 rpm and a headspace aeration of 0.1 L sterile air min −1 reactor −1 .…”