For the development of biotechnological processes in academia as well as in industry new techniques are required which enable online monitoring for process characterization and control. Nuclear magnetic resonance (NMR) spectroscopy is a promising analytical tool, which has already found broad applications in offline process analysis. The use of online monitoring, however, is oftentimes constrained by high complexity of custom-made NMR bioreactors and considerable costs for high-field NMR instruments (>US$200,000). Therefore, low-field (1) H NMR was investigated in this study in a bypass system for real-time observation of fermentation processes. The new technique was validated with two microbial systems. For the yeast Hansenula polymorpha glycerol consumption could accurately be assessed in spite of the presence of high amounts of complex constituents in the medium. During cultivation of the fungal strain Ustilago maydis, which is accompanied by the formation of several by-products, the concentrations of glucose, itaconic acid, and the relative amount of glycolipids could be quantified. While low-field spectra are characterized by reduced spectral resolution compared to high-field NMR, the compact design combined with the high temporal resolution (15 s-8 min) of spectra acquisition allowed online monitoring of the respective processes. Both applications clearly demonstrate that the investigated technique is well suited for reaction monitoring in opaque media while at the same time it is highly robust and chemically specific. It can thus be concluded that low-field NMR spectroscopy has a great potential for non-invasive online monitoring of biotechnological processes at the research and practical industrial scales.
A l d o l S y n t h e s i s b y a n t i -M a r k o v n i k o v H y d r a t i o n o f P r o p a r g y l o x y S u b s t r a t e sAbstract: Aldol derivatives have been synthesized by redox-neutral catalytic anti-Markovnikov hydration of propargyloxy substrates. A reiterative sequence of aldehyde alkynylation and alkyne hydration leads to 1,3-polyol derivatives.
Zooming in on microfluidics: The potential of conventional NMR microscopy is limited by poor sensitivity and long measurement times. Recent advances in remote‐detection NMR spectroscopy overcome these limitations and give unique insight into microfluidic processes with unprecedented spatial and temporal resolution (picture: high‐resolution three‐dimensional velocity maps of fast flow in a microcapillary).
Zoom in die Mikrofluidik: Das Potenzial konventioneller NMR‐Mikroskopie ist durch niedrige Empfindlichkeit und lange Messdauern begrenzt. Neue Fortschritte in der Ferndetektions‐NMR überwinden diese Grenzen und geben einzigartige Einblicke in mikrofluidische Prozesse mit zuvor nicht dagewesener räumlicher und zeitlicher Auflösung (Bild: hochaufgelöste dreidimensionale Geschwindigkeitsbilder von schnellem Fluss in einer Mikrokapillare).
Investigating the 2D-T
2-T
2-relaxation exchange of inter-stitial water in a packing of sedimented Stöber-silicate spheres, we come the conclusion that contrary to its behaviour in macro-pores, water confined in nano-pores of silica exhibits enhanced diffusivity. The 2D-experiments, performed at different temperatures, reveal a temperature-dependent bimodal relaxation distribution and two-site relaxation exchange. Our recently introduced kinetic multi-site exchange model is applied to derive the according exchange rates. The resulting Arrhenius plot produces an exchange activation energy of 7 kJ/mol, which is well below the hydrogen bond energy or the activation energy for self-diffusion of water in the bulk. A possible hopping-mechanism as the source of enhanced proton-diffusion in nanoporous silica is discussed, as well as its significance to mass transfer in porous media.
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