Microchemostat—microbial continuous culture in a polymer-based, instrumented microbioreactor

Abstract

In a chemostat, microbial cells reach a steady state condition at which cell biomass production, substrates and the product concentrations remain constant. These features make continuous culture a unique and powerful tool for biological and physiological research. We present a polymer-based microbioreactor system integrated with optical density (OD), pH, and dissolved oxygen (DO) real-time measurements for continuous cultivation of microbial cells. Escherichia coli (E. coli) cells are continuously cultured in a 150 microL, membrane-aerated, well-mixed microbioreactor fed by a pressure-driven flow of fresh medium through a microchannel. Chemotaxisial back growth of bacterial cells into the medium feed channel is prevented by local heating. Using poly(ethylene glycol) (PEG)-grafted poly(acrylic acid) (PAA) copolymer films, the inner surfaces of poly(methyl methacrylate) (PMMA) and poly(dimethylsiloxane) (PDMS) of the microbioreactor are modified to generate bio-inert surfaces resistant to non-specific protein adsorption and cell adhesion. The modified surfaces of microbioreactor effectively reduce wall growth of E. coli for a prolonged period of cultivation. Steady state conditions at different dilution rates are demonstrated and characterized by steady OD, pH, and DO levels.

Microfluidic Bioreactors for Cell Culturing: A Review

“…Microbioreactors platforms integrated with highly sensitive detection systems to monitor key variables (pH, dissolved oxygen and biomass) have been applied to screen and optimise conditions for high-throughput fermentation processes. During the last decade, several designs of such microbioreactors have been demonstrated for high-throuput bioprocessing [27,35,37,58,73,180]. The performance of these microbioreactors compares favourably with their conventional macroscale counterparts in terms of the measurement profiles of key physicochemical variables (pH, dissolved oxygen and optical density).…”

“…Another method of temperature control commonly used by scientists is the use of a controlled water bath where the base of the microbioreactor can be connected to a water bath and thermostated water circulated in and out from the base. This approach has been used in microfluidic bioreactors for microbial bioprocessing developments [28,35,58]. Microheaters are an important tool for controlling temperature in miniaturised devices due to their size and the ease with which they can be integrated in such microfluidic devices e.g.…”

“…Zhang et al [58] developed a microbioreactor fabricated from poly(methylmethacrylate) (PMMA) and poly(dimethylsiloxane) (PDMS). The microchannels of the microbioreactor were coated with poly(ethylene glycol) (PEG)-grafted poly(acrylic acid) (PAA) copolymer films to prevent chemotaxisial back growth of bacterial cells, i.e.…”

Integrating impedance-based growth-rate monitoring into a microfluidic cell culture platform for live-cell microscopy

“…Moreover, phototoxic effects may be induced upon frequent imaging 16 so that additional control experiments become necessary to assess such phototoxicity effects, which are tedious to perform. Phototoxicity effects can be obviated by the use of label free techniques, such as measuring the optical density of the cell solution in microfluidic platforms 17,18 . Unfortunately, suitable devices are not amenable to high-resolution optical imaging and to obtaining information at single-cell resolution.…”

Trends of Automation of Integrated Microfluidics

“…While silicon-based micro devices manufactured with methods developed in the semiconductor industry were some of the earliest examples of microfluidics-based research, there has been a shift over the last decade towards polymer-based devices, using materials such as Teflon, thermoset polyesters, silicon elastomer photoresist, SU-8 photoresist, poly-dimethylsiloxane (PDMS) and poly-methyl methacrylate [4][5][6][7]. Silicone rubber-based chemostats [8], bioreactors [9][10][11][12], and other microfluidic platforms [13,14] containing multiple cell chambers have been successfully applied in the cell culture applications in recent years. These microfluidic devices, consisting of optically-transparent PDMS, were fabricated using a casting process from silicon wafer molds containing photoresists with positive-relief channel patterns.…”