Microfluidic devices can mimic naturally occurring microenvironments and create microbial population heterogeneities ranging from planktonic cells to biofilm states. The exposure of such populations to spatially organized stress gradients can promote their adaptation into complex phenotypes, which are otherwise difficult to achieve with conventional experimental setups. Here a microfluidic chip that employs precise chemical gradients in consecutive microcompartments to perform microbial adaptive laboratory evolution (ALE), a key tool to study evolution in fundamental and applied contexts is described. In the chip developed here, microbial cells can be exposed to a defined profile of stressors such as antibiotics. By modulating this profile, stress adaptation in the chip through resistance or persistence can be specifically controlled. Importantly, chip‐based ALE leads to the discovery of previously unknown mutations in Escherichia coli that confer resistance to nalidixic acid. The microfluidic device presented here can enhance the occurrence of mutations employing defined micro‐environmental conditions to generate data to better understand the parameters that influence the mechanisms of antibiotic resistance.
mixing. These features can often accelerate or even enable reactions to proceed. [4] A key factor for the successful dissemination of this technology is the ability for production of masters for molding microfluidic droplet generators and related accessories through rapid prototyping with low associated manufacturing and material costs, because only few ready-to-use microfluidic devices are currently commercially available and their geometries are usually limited to standard applications.Soft lithography using SU-8 masters is the gold standard for the production of microfluidic prototypes. [5] In this method, an SU-8 photoresist is structured by means of optical lithography and the resulting negative structure is then molded by soft lithography into polydimethylsiloxane (PDMS). For sealing, the elastomeric PDMS chips are usually plasma bonded onto glass supports. The very high structural resolution along with excellent surface quality in terms of low roughness is the major advantages of this technology, whereas low aspect ratios and difficulties in the production of variable heights in a single chip, along with high machine costs and the requirement of clean room facilities for the production of masters, are on the downside. Since trained clean room personnel and expensive infrastructure are often not available in research institutes engaged in biomedical research and the life sciences, there is a great demand for alternative costeffective manufacturing processes for microfluidic chips.The implementation of additive manufacturing (AM) methods in microfluidic prototyping is currently attracting Microfluidic water-in-oil droplets are a versatile tool for biological and biochemical applications due to the advantages of extremely small monodisperse reaction vessels in the pL-nL range. A key factor for the successful dissemination of this technology to life science laboratory users is the ability to produce microfluidic droplet generators and related accessories by low-entry barrier methods, which enable rapid prototyping and manufacturing of devices with low instrument and material costs. The direct, experimental side-by-side comparison of three commonly used additive manufacturing (AM) methods, namely fused deposition modeling (FDM), inkjet printing (InkJ), and stereolithography (SLA), is reported. As a benchmark, micromilling (MM) is used as an established method. To demonstrate which of these methods can be easily applied by the non-expert to realize applications in topical fields of biochemistry and microbiology, the methods are evaluated with regard to their limits for the minimum structure resolution in all three spatial directions. The suitability of functional SLA and MM chips to replace classic SU-8 prototypes is demonstrated on the basis of representative application cases. Microfluidic ManufacturingProf. R. Mikut
We here report the application of a machine‐based microfluidic biofilm cultivation and analysis platform for studying the performance of biocatalytically active biofilms. By using robotic sampling, we succeeded in spatially resolving the productivity of three microfluidic reactors containing biocatalytically active biofilms that inducibly overexpress recombinant enzymes. Escherichia coli biofilms expressing two stereoselective oxidoreductases, the (R)‐selective alcohol dehydrogenase LbADH and the (S)‐selective ketoreductase Gre2p, as well as the phenolic acid decarboxylase EsPAD were used. The excellent reproducibility of the cultivation and analysis methods observed for all three systems underlines the usefulness of the new technical platform for the investigation of biofilms. In addition, we demonstrated that the analytical platform also opens up new opportunities to perform in‐depth spatially resolved studies on the biomass growth in a reactor channel and its biochemical productivity. Since the platform not only offers the detailed biochemical characterization but also broad capabilities for the morphological study of living biofilms, we believe that our approach can also be performed on many other natural and artificial biofilms to systematically investigate a wide range of process parameters in a highly parallel manner using miniaturized model systems, thus advancing the harnessing of microbial communities for technical purposes.
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