Diffusion-driven fed-batch fermentation in perforated ring flasks.

PURPOSE: Simultaneous membrane-based feeding and monitoring of the oxygen transfer rate shall be introduced to the newly established perforated ring flask, which consists of a cylindrical glass flask with an additional perforated inner glass ring, for rapid bioprocess development. METHODS: A 3D-printed adapter was constructed to enable monitoring of the oxygen transfer rate in the perforated ring flasks. Escherichia coli experiments in batch were performed to validate the adapter. Fed-batch experiments with different diffusion rates and feed solutions were performed. RESULTS: The adapter and the performed experiments allowed a direct comparison of the perforated ring flasks with Erlenmeyer flasks. In batch cultivations, maximum oxygen transfer capacities of 80 mmol L-1 h-1 were reached with perforated ring flasks, corresponding to a 3.5 times higher capacity than in Erlenmeyer flasks. Fed-batch experiments with a feed reservoir concentration of 500 g glucose L-1 were successfully conducted. Based on the oxygen transfer rate, an ammonium limitation could be observed. By adding 40 g ammonium sulfate L-1 to the feed reservoir, the limitation could be prevented. CONCLUSION: The membrane-based feeding, an online monitoring technique, and the perforated ring flask were successfully combined and offer a new and promising tool for screening and process development in biotechnology.

Validation of computational fluid dynamics of shake flask experiments at moderate viscosity by liquid distributions and volumetric power inputs.

Computational fluid dynamics (CFD) has recently become a pivotal tool in the design and scale-up of bioprocesses. While CFD has been extensively utilized for stirred tank reactors (STRs), there exists a relatively limited body of literature focusing on CFD applications for shake flasks, almost exclusively concentrated on fluids at waterlike viscosity. The importance of CFD model validation cannot be overstated. While techniques to elucidate the internal flow field are necessary for model validation in STRs, the liquid distribution, caused by the orbital shaking motion of shake flasks, can be exploited for model validation. An OpenFOAM CFD model for shake flasks has been established. Calculated liquid distributions were compared to suitable, previously published experimental data. Across a broad range of shaking conditions, at waterlike and moderate viscosity (16.7 mPa∙s), the CFD model's liquid distributions align excellently with the experimental data, in terms of overall shape and position of the liquid relative to the direction of the centrifugal force. Additionally, the CFD model was used to calculate the volumetric power input, based on the energy dissipation. Depending on the shaking conditions, the computed volumetric power inputs range from 0.1 to 7 kW/m3 and differed on average by 0.01 kW/m3 from measured literature data.

Implementation of Perforated Concentric Ring Walls Considerably Improves Gas-Liquid Mass Transfer of Shaken Bioreactors.

Since their first use in the 1930s, shake flasks have been a widely used bioreactor type for screening and process development due to a number of advantages. However, the limited gas-liquid mass transfer capacities-resulting from practical operation limits regarding shaking frequency and filling volumes-are a major drawback. The common way to increase the gas-liquid mass transfer in shake flasks with the implementation of baffles is generally not recommended as it comes along with several severe disadvantages. Thus, a new design principle for shaken bioreactors that aims for improving the gas-liquid mass transfer without losing the positive characteristics of unbaffled shake flasks is introduced. The flasks consist of cylindrical glass vessels with implemented perforated concentric ring walls. The ring walls improve the gas-liquid mass transfer via the formation of additional liquid films on both of its sides, whereas the perforations allow for mixing between the compartments. Sulfite oxidation experiments revealed over 200% higher maximum oxygen transfer capacities (OTRmax) compared to conventional shake flasks. In batch cultivations of Escherichia coli BL21 in mineral media, unlimited growth until glucose depletion and oxygen transfer rates (OTR) of up to 138 mmol/L/h instead of an oxygen limitation at 57 mmol/L/h as in normal shake flasks under comparable conditions could be achieved. Even overflow metabolism could be prevented due to sufficient oxygen supply without the use of unconventional shaking conditions or oxygen enrichment. Therefore, we believe that the new perforated ring flask principle has a high potential to considerably improve biotechnological screening and process development steps.

A New Three-Component Photo-Initiating System for Visible Light Recording of Volume Holograms with Single-Pulsed Laser.

Versatile substituted electron-deficient trichloromethylarenes can easily be synthesized and combined with a Safranine O/triarylalkylborate salt to form a highly efficient three-component photo-initiation system that starts free radical polymerization to finally form holographic gratings with a single-pulsed laser. The mechanism of this photo-initiation most likely relies on an electron transfer from the borate salt into the semi-occupied HOMO of the excited dye molecule Safranine O, which after fragmentation generates an initiating alkyl radical and longer-lived dye radical species. This dye radical is most probably oxidized by the newly introduced trichloromethylarene derivative as an electron acceptor. The two generated radicals from one absorbed photon initiate the photopolymerization and form index gratings in a suitable holographic recording material. This process is purely photonic and does not require further non-photonic post treatments.

John Brown's system of medicine and its introduction in Denmark around 1800.

At the end of the eighteenth century a scientific basis for medicine was called for. The Scottish physician John Brown proposed an all-comprising medical system in 1780. A surplus or lack of stimulating factors, the prime movers of life according to Brown, was supposed to explain all diseases and indicate their treatment. Individuals only subjected to a small degree of stimulation became affected by "asthenic diseases" which were the most frequent diseases. They should be treated with abundant food and wine, supplemented with camphor, opium, or other drugs considered to be stimulating. Conversely, individuals with "sthenic diseases" should reduce their intake of food and beverage. Brown's system was received with transient approval by some Danish physicians from the late 1790s. But it soon proved to be of no value in medical practice, and its success dwindled within academic medicine around 1814. On the other hand, it seemed to generate new ideas. It became linked with the German Romantic Movement and "Naturphilosophie." The widespread use of camphor and opium in both academic and folk medicine, continued throughout the nine- teenth century and into the twentieth century.

In situ formation of a MoS2 -based inorganic-organic nanocomposite by directed thermal decomposition.

Nanocomposites based on molybdenum disulfide (MoS2 ) and different carbon modifications are intensively investigated in several areas of applications due to their intriguing optical and electrical properties. Addition of a third element may enhance the functionality and application areas of such nanocomposites. Herein, we present a facile synthetic approach based on directed thermal decomposition of (Ph4 P)2 MoS4 generating MoS2 nanocomposites containing carbon and phosphorous. Decomposition at 250 °C yields a composite material with significantly enlarged MoS2 interlayer distances caused by in situ formation of Ph3 PS bonded to the MoS2 slabs through MoS bonds and (Ph4 P)2 S molecules in the van der Waals gap, as was evidenced by (31) P solid-state NMR spectroscopy. Visible-light-driven hydrogen generation demonstrates a high catalytic performance of the materials.

["The Society for letters and natural science" The young Ole H. Mynster and the chemical revolution around 1800]. / "Det Litteraire og Naturforskende Selskab". Den unge Ole H. Mynster og den kemiske revolution omkring 1800.

Ole H. Mynster (1772-1818) was a stepson of the leading physician at the Royal Frederik Hospital in Copenhagen. At an early age he became fond of zoology and mineralogy. He created "societies" in Enlightenment-style for boys and young people with lectures and collections. Later on a circle of talented young students, scientists and poets met in his small room at the hospital. Some of them with Ole Mynster as the head set up a modern scientific journal, Physicalsk, oeconomisk og medicochirurgisk Bibliotek for Danmark og Norge which encouraged the introduction of antiphlogistic chemistry. Ole Mynster became physician at the Royal Frederik Hospital and lecturer in clinical pharmacology. He wrote the first book in Danish on pharmacology based upon chemistry. In their memoirs, prominent members of his circle have told about him, and his son F.L. Mynster has written a draft for a biography. An overview of the activities within natural science and medicine of the young Ole Hieronymus Mynster is presented.

[A case of Yellow fever in 1887]. / Et tilfælde af gul feber i 1887.

A young Danish sailor died from yellow fever in Barbados in 1887. The Shipmaster's letter to the family with a description of the course of the disease, which has been preserved, is presented here together with a photo of the sailor and a painting of the Danish sailing-ship.

[A birth with fatal outcome in 1866]. / En fatalt forløbende fødsel i 1866. En kasuistik med illustrationer.

A birth with fatal outcome for both the mother and the foetus was reported in the Danish medical journal, Bibliothek for Læger in 1868. Here, the article with its two illustrations is summarised because of the vivid description of the course together with the therapeutic considerations expressed by the obstetrician. Due to an earlier osteomyelitis the pregnant woman's spine was deformed and her pelvis was narrowed. The birth came to a standstill, and it became necessary to reduce the circumference of the foetus' cranium by perforation, after which the dead foetus could be delivered. The woman died of infection some days later. Afterwards her deformed lumbar spine and pelvis was removed, preserved and depicted in two lithographs. The preserved pelvis is still extant in the Saxtorphian obstetric collection in Medical Museion, Copenhagen.

Cross-section perimeter is a suitable parameter to describe the effects of different baffle geometries in shaken microtiter plates.

BACKGROUND: Biotechnological screening processes are performed since more than 8 decades in small scale shaken bioreactors like shake flasks or microtiter plates. One of the major issues of such reactors is the sufficient oxygen supply of suspended microorganisms. Oxygen transfer into the bulk liquid can in general be increased by introducing suitable baffles at the reactor wall. However, a comprehensive and systematic characterization of baffled shaken bioreactors has never been carried out so far. Baffles often differ in number, size and shape. The exact geometry of baffles in glass lab ware like shake flasks is very difficult to reproduce from piece to piece due to the hard to control flow behavior of molten glass during manufacturing. Thus, reproducibility of the maximum oxygen transfer capacity in such baffled shake flasks is hardly given. RESULTS: As a first step to systematically elucidate the general effect of different baffle geometries on shaken bioreactor performance, the maximum oxygen transfer capacity (OTRmax) in baffled 48-well microtiter plates as shaken model reactor was characterized. This type of bioreactor made of plastic material was chosen, as the exact geometry of the baffles can be fabricated by highly reproducible laser cutting. As a result, thirty different geometries were investigated regarding their maximum oxygen transfer capacity (OTRmax) and liquid distribution during shaking. The relative perimeter of the cross-section area as new fundamental geometric key parameter is introduced. An empirical correlation for the OTRmax as function of the relative perimeter, shaking frequency and filling volume is derived. For the first time, this correlation allows a systematic description of the maximum oxygen transfer capacity in baffled microtiter plates. CONCLUSIONS: Calculated and experimentally determined OTRmax values agree within ± 30% accuracy. Furthermore, undesired out-of-phase operating conditions can be identified by using the relative perimeter as key parameter. Finally, an optimum well geometry characterized by an increased perimeter of 10% compared to the unbaffled round geometry is identified. This study may also assist to comprehensively describe and optimize the baffles of shake flasks in future.

[A reading of Foucault's "The Birth of the Clinic"]. / En læsning af Michel Foucaults "Klinikkens fødsel".

The starting point for Foucault's book was his wide reading of French medical literature from late 18th and early 19th centuries. He showed how the concept of disease changed profoundly during that period of great societal changes. Foucault's protagonists in the book were the French doctors Pinel, Bichat, Laënnec and Broussais. Here, short biographies and summaries of their works will be presented in the medical and historical context and together with extracts of Foucault's text.

Synthesis, characterization and reactivity of group 4 metallocene bis(diphenylphosphino)acetylene complexes-a reactivity and bonding study.

A study of the coordination chemistry of bis(diphenylphosphino)acetylene, Ph2P-C≡C-PPh2, with selected group 4 metallocenes is presented. By substitution of the alkyne in complexes of the type Cp'2M(L)(η(2)-Me3SiC2SiMe3) (M = Ti, no L; M = Zr, L = pyridine; Cp' = substituted or unsubstituted bridged or unbridged η(5)-cyclopentadienyl), the expected mononuclear complexes Cp*2Ti(η(2)-Ph2PC2PPh2) (4Ti), (rac-ebthi)Ti(η(2)-Ph2PC2PPh2) (5Ti), and (rac-ebthi)Zr(η(2)-Ph2PC2PPh2) (5Zr) [ebthi = ethylenebis(tetrahydroindenyl)] were obtained. When [Cp2Zr] was used in the reaction of Cp2Zr(py)(η(2)-Me3SiC2SiMe3) with Ph2P-C≡C-PPh2, the dinuclear complex [Cp2Zr(η(2)-Ph2PC2PPh2)]2 (6) was formed and isolated in the solid state. In solution, this complex is in equilibrium with the very spectacular structure of complex 7b as the first example of such a highly strained four-membered heterometallacycle of a group 4 metal, involving the rare R2PCCR' fragment in the cyclic unit. Both the stability and reactivity of heterodisubstituted alkynes X-C≡C-X (X = NR2, PR2, SR, SiR3, etc.) themselves and also of their complexes are of general interest. Complex 6 did not react with a second [Cp2Zr] fragment to form a homobimetallic complex. In contrast, for (rac-ebthi)Zr(η(2)-Ph2PC2PPh2) (5Zr) this reaction occurs. In the reaction of complex 4Ti with the Ni(0) complex (Cy3P)2Ni(η(2)-C2H4) (Cy = cyclohexyl), C-P bond cleavage of the alkyne ligand resulted in the formation of the isolated complex [(Cy3P)Ni(µ-PPh2)]2 (11). The structure and bonding of the complexes were investigated by DFT analysis to compare the different possible coordination modes of the R2P-C≡C-PR2 ligand. For compound 7b, a flip-flop coordination of the phosphorus atoms was proposed. Complexes 4Ti, 5Ti, 5Zr, 6, and 11 were characterized by X-ray crystallography.

{N,N-Bis[bis-(2,2,2-tri-fluoro-eth-oxy)phosphan-yl]methyl-amine-κ(2) P,P'}bis-(η(5)-cyclo-penta-dien-yl)titanium(II).

The title compound, [Ti(C5H5)2(C9H11F12NO4P2)], is a four-membered titanacycle obtained from the reaction of Cp2Ti(η(2)-Me3SiC2SiMe3) and CH3N[P(OCH2CF3)2]2 {N,N-bis-[bis-(tri-fluoro-eth-oxy)phosphan-yl]methyl-amine, tfepma}. The Ti(II) atom is coordinated by two cyclo-penta-dienyl (Cp) ligands and the chelating tfepma ligand in a strongly distorted tetra-hedral geometry. The mol-ecule is located on a mirror plane.

Highly strained heterometallacycles of Group†4 metallocenes with bis(diphenylphosphino)methanide ligands.

A study of the coordination chemistry of different bis(diphenylphosphino)methanide ligands [Ph2PC(X)PPh2] (X = H, SiMe3) with Group 4 metallocenes is presented. The paramagnetic complexes [Cp2Ti{κ(2)-P,P-Ph2PC(X)PPh2}] (X = H (3 a), X = SiMe3 (3 b)) have been prepared by the reactions of [(Cp2TiCl)2] with [Li{C(X)PPh2}2(thf)3]. Complex 3 b could also be synthesized by reaction of the known titanocene alkyne complex [Cp2Ti(η(2)-Me3SiC2SiMe3)] with Ph2PC(H)(SiMe3)PPh2 (2 b). The heterometallacyclic complex [Cp2Zr(H){κ(2)-P,P-Ph2PC(H)PPh2}] (4 aH) has been prepared by reaction of the Schwartz reagent with [Li{C(H)PPh2}2(thf)3]. Reactions of [Cp2HfCl2] with [Li{C(X)PPh2}2(thf)3] gave the highly strained corresponding metallacycles [Cp2M(Cl){κ(2)-P,P-Ph2PC(X)PPh2}] (5 aCl and 5 bCl) in very good yields. Complexes 3 a, 4 aH, and 5 aCl have been characterized by X-ray crystallography. Complex 3 a has also been characterized by EPR spectroscopy. The structure and bonding of the complexes has been investigated by DFT analysis. Reactions of complexes 4 aH, 5 aCl, and 5 bCl did not give the corresponding more unsaturated heterometallacyclobuta-2,3-dienes.

Synthesis and structures of ansa-titanocene complexes with diatomic bridging units for overall water splitting.

The synthesis of a series of ansa-titanocene dichlorides [Cp'2TiCl2] (Cp' = bridged η(5)-tetramethylcyclopentadienyl) and the corresponding titanocene bis(trimethylsilyl)acetylene complexes [Cp'2Ti(η(2)-Me3SiC2SiMe3)] is described. The ethanediyl-bridged complexes [C2H4(C5Me4)2TiCl2] (2-Cl2) and [C2H4(C5Me4)2Ti(η(2)-Me3SiC2SiMe3)] (2-btmsa; btmsa = η(2)-Me3SiC2SiMe3) can be obtained from the hitherto unknown calcocenophane complex [C2H4(C5Me4)2Ca(THF)2] (1). Furthermore, a heterodiatomic bridging unit containing both, a dimethylsilyl and a methylene group was introduced to yield the ansa-titanocene dichloride [Me2SiCH2(C5Me4)2TiCl2] (3-Cl2) and the bis(trimethylsilyl)acetylene complex [Me2SiCH2(C5Me4)2Ti(η(2)-Me3SiC2SiMe3)] (3-btmsa). Besides, tetramethyldisilyl- and dimethylsilyl-bridged metallocene complexes (structural motif 4 and 5, respectively) were prepared. All ansa-titanocene alkyne complexes were reacted with stoichiometric amounts of water; the hydrolysis products were isolated as model complexes for the investigation of the elemental steps of overall water splitting. Compounds 1, 2-btmsa, 2-(OH)2, 3-Cl2, 3-btmsa, 4-(OH)2, 3-alkenyl and 5-alkenyl were characterised by X-ray diffraction analysis.

Plasma synthesis of polymer-capped dye-sensitised anatase nanopowders for visible-light-driven hydrogen evolution.

Visible-light-driven photocatalysis is currently attracting a great deal of attention because of its potential application in solar water splitting. However, the development of efficient and durable catalyst systems is still a challenging problem. In Ru dye-sensitised TiO(2) nanopowders, catalyst performances are found to decline as a result of poor bonding of the dye molecule to the TiO(2) surface and subsequent detachment and self-aggregation of the dye. Our strategy to improve the stability of the dye-TiO(2) interface is the encapsulation of the dye/TiO(2) assembly in an amino-group-containing polyallylamine layer anchored to TiO(2). A low-pressure pulsed microwave discharge plasma polymerization process was employed to coat a commercial anatase nanopowder with a thin polyallylamine layer to nanoconfine the adsorbed dye molecules. Electron microscopy and UV/Vis spectroscopy was carried out to characterise the resulting encapsulated nanostructures. The long-term stability of the new nanomaterial as the photoactive component of a water reduction catalyst system for H(2) evolution investigated in a slurry reactor under visible-light irradiation showed stable evolution rates over a period of several days.

The influence of carbon content on the structure and properties of MoS(x)C(y) photocatalysts for light-driven hydrogen generation.

Carbon containing nano-sized molybdenum sulfide composites (MoS(x)C(y)) obtained by thermal decomposition reactions of (R(4)N)(2)MoS(4) (R = -H (C(0)), -CH(3) (C(1)), -C(3)H(7) (C(3)), and -C(6)H(13) (C(6))) show promising performance in visible-light driven photocatalytic hydrogen generation.

Investigation and enhancement of the stability and performance of water reduction systems based on cyclometalated iridium(III) complexes.

Water reduction systems that use a bis-cyclometalated Ir(III) photosensitiser (PS) along with homogeneous Pd complexes as a source of in-situ-formed colloidal Pd as the water reducing complex (WRC) and triethylamine (TEA) as the sacrificial electron donor were tested and characterised with respect to their photocatalytic H(2) production performance. It was confirmed that substitution of the 2-(pyridin-2-yl)benzen-1-ide (pyb) ligand in the well-known system [Ir(pyb)(2)(bpy)](+) (bpy=2,2'-bipyridine) by the fluorinated cyclometalating ligand 5-fluoro-2-(5-methylpyridin-2-yl)benzen-1-ide (Fmpyb) tremendously enhanced the H(2) production rate. Moreover, variation of the bidentate N^N ligand bpy by alkyl substitution in the 4,4'-position resulted in an increase in the H(2) production yield by a factor of three. The incident-photon-to-hydrogen-efficiency could be enhanced from 2.6 to 12.3%. Furthermore, a new dinuclear Co complex was used as a reduction catalyst and showed up to 760 turnovers after 20 h. A detailed study of the concentration impact of all components in the photoredox system was performed. DFT calculations were used to aid the explanation of the findings.

Development of a modified Respiration Activity Monitoring System for accurate and highly resolved measurement of respiration activity in shake flask fermentations.

BACKGROUND: The Respiration Activity Monitoring System (RAMOS) is an established device to measure on-line the oxygen transfer rate (OTR), thereby, yielding relevant information about metabolic activities of microorganisms and cells during shake flask fermentations. For very fast-growing microbes, however, the RAMOS technique provides too few data points for the OTR. Thus, this current study presents a new model based evaluation method for generating much more data points to enhance the information content and the precision of OTR measurements. RESULTS: In cultivations with E.coli BL21 pRSET eYFP-IL6, short diauxic and even triauxic metabolic activities were detected with much more detail compared to the conventional evaluation method. The decline of the OTR during the stop phases during oxygen limitations, which occur when the inlet and outlet valves of the RAMOS flask were closed for calibrating the oxygen sensor, were also detected. These declines reflected a reduced oxygen transfer due to the stop phases. In contrast to the conventional calculation method the new method was almost independent from the number of stop phases chosen in the experiments. CONCLUSIONS: This new model based evaluation method unveils new peaks of metabolic activity which otherwise would not have been resolved by the conventional RAMOS evaluation method. The new method yields substantially more OTR data points, thereby, enhancing the information content and the precision of the OTR measurements. Furthermore, oxygen limitations can be detected by a decrease of the OTR during the stop phases.

Highly strained heterometallacycles of Group†4 metallocenes with bis(diphenylphosphino)amide ligands.

A study regarding coordination chemistry of the bis(diphenylphosphino)amide ligand Ph(2) P-N-PPh(2) at Group 4 metallocenes is presented herein. Coordination of N,N-bis(diphenylphosphino)amine (1) to [(Cp(2) TiCl)(2) ] (Cp=η(5) -cyclopentadienyl) generated [Cp(2) Ti(Cl)P(Ph(2) )N(H)PPh(2) ] (2). The heterometallacyclic complex [Cp(2) Ti(κ(2) -P,P-Ph(2) P-N-PPh(2) )] (3 Ti) can be prepared by reaction of 2 with n-butyllithium as well as from the reaction of the known titanocene-alkyne complex [Cp(2) Ti(η(2) -Me(3) SiC(2) SiMe(3) )] with the amine 1. Reactions of the lithium amide [(thf)(3) Li{N(PPh(2) )(2) }] with [Cp(2) MCl(2) ] (M=Zr, Hf) yielded the corresponding zirconocene and hafnocene complexes [Cp(2) M(Cl){κ(2) -N,P-N(PPh(2) )(2) }] (4 Zr and 4 Hf). Reduction of 4 Zr with magnesium gave the highly strained heterometallacycle [Cp(2) Zr(κ(2) -P,P-Ph(2) P-N-PPh(2) )] (3 Zr). Complexes 2, 3 Ti, 4 Hf, and 3 Zr were characterized by X-ray crystallography. The structures and bondings of all complexes were investigated by DFT calculations.