A proteomic and transcriptional view of acidogenic and solventogenic steady-state cells of Clostridium acetobutylicum in a chemostat culture

The complex changes in the life cycle of Clostridium acetobutylicum, a promising biofuel producer, are not well understood. During exponential growth, sugars are fermented to acetate and butyrate, and in the transition phase, the metabolism switches to the production of the solvents acetone and butanol accompanied by the initiation of endospore formation. Using phosphate-limited chemostat cultures at pH 5.7, C. acetobutylicum was kept at a steady state of acidogenic metabolism, whereas at pH 4.5, the cells showed stable solvent production without sporulation. Novel proteome reference maps of cytosolic proteins from both acidogenesis and solventogenesis with a high degree of reproducibility were generated. Yielding a 21% coverage, 15 protein spots were specifically assigned to the acidogenic phase, and 29 protein spots exhibited a significantly higher abundance in the solventogenic phase. Besides well-known metabolic proteins, unexpected proteins were also identified. Among these, the two proteins CAP0036 and CAP0037 of unknown function were found as major striking indicator proteins in acidogenic cells. Proteome data were confirmed by genome-wide DNA microarray analyses of the identical cultures. Thus, a first systematic study of acidogenic and solventogenic chemostat cultures is presented, and similarities as well as differences to previous studies of batch cultures are discussed

Online quality assurance of microchannels in roll-to-roll by optical coherence tomography

Abstract Roll-to-roll (R2R) process is an emerging technology to manufacture printed electronics, microfluidics, biochemical sensors etc. The requirements for high quality and small tolerances at the manufacturing phase are of the essence for such products. To verify the quality and guarantee the high production yield, high speed, non-destructive testing methods are needed. In this paper, optical coherence tomography (OCT) device is used at the R2R-line to measure online hot embossed microchannel structures at speed of 1 m/min, which is typical for the hot embossing process. The channel’s width and shape are determined along the web. The applicability of OCT for topography measurements is demonstrated in an actual R2R environment

Wavelength scanning interferometry for topography of microchannels at roll-to-roll Line with optical coherence tomography

Abstract Roll-to-roll (R2R) process is mass manufacturing method that can produce various products ranging from printed electronics to microfluidics. Microfluidics, used in biosensors, demands high tolerances and quality to guarantee correct functionality of sensors. In this work, optical coherence tomography device was installed at the R2R-line to measure the height and width of the hot embossed microchannel structures at speed of 1m/min. The repeating channel structure on the 10 m long sample web was measured at 1m interval. An algorithm, typically used in wavelength scanning interferometry (WSI), is utilized to recover topography at nanometer scale. The results showed that the R2R hot embossing process was very stable and predictable. If process parameters, for instance pressure at the hot embossing unit was increased, it resulted deeper channels as expected. The OCT, with the WSI algorithm, provides topography of microchannel at nanometer scale being thus an excellent tool for optimization of process parameters and for on-line quality control

Effect of solvent lamination on roll-to-roll hot-embossed PMMA microchannels evaluated by optical coherence tomography

Abstract Manufacturing of microfluidic based diagnostic devices requires small tolerances and uniform quality to guarantee reliable and repeatable test results. This work describes characterization of morphological changes that occur to a hot embossed PMMA microfluidic channel after solvent lamination with a PMMA lid. A non-contact cross-sectional analysis of the lidded microfluidic device was performed by optical coherence tomography (OCT). The solvent induced morphology change led to a porous structure in bottom corners of hot-embossed channels, which allowed a fluid to absorb in the material. The measurements of solvent diffusion showed faster diffusion rate at the corners of the channel, in which the accumulated stress during the embossing process was the highest. The stress profile was verified by simulation of von Mises stresses during a molding phase of a hot embossing process. The porous structure with increased fluid diffusion has an unwanted effect on bioassay result, e.g. when detection molecules leak into the substrate thus leading to unspecific signal on chip. OCT was found to be a valuable, non-destructive imaging method to monitor solvent diffusion process and lamination process quality