Kinetics of reextraction of Penicillin G from the organic phase after reactive extraction

The kinetics of reextraction of penicillin from the LA-2-penicillin complex-n-butylacetate solution by phosphate buffer was investigated experimentally and theoretically. The concentration time functions can be described by a mathematical model in a wide range of pH-values and complex concentrations.List of Symbols a _P [m²/m³] specific interfacial area - c _A , c _Ai [mMol] concentration of amine in the bulk of the organic phase and at the interface - c _AHP , c _AHPi [mMol] concentration of the complex in bulk of the organic phase and at the interface - c _H , c _Hi [mMol] concentration of the proton in the bulk of the aqueous phase and at the interface - c _P , c _Pi [mMol] concentration of the penicillin acid anion in the bulk of the aqueous phase and at the interface - J _A , J _AHP , J _P [mMol · cm · s^–1] fluxes of amine, complex and penicillin acid anion - k _A , k _AHP , k _P [cm · s^–1] mass transfer coefficients of amine, complex and penicillin acid anion - K _G [mMol²] equilibrium constant - t [k] extraction time     

Dissecting tripartite synapses with STED microscopy

The concept of the tripartite synapse reflects the important role that astrocytic processes are thought to play in the function and regulation of neuronal synapses in the mammalian nervous system. However, many basic aspects regarding the dynamic interplay between pre- and postsynaptic neuronal structures and their astrocytic partners remain to be explored. A major experimental hurdle has been the small physical size of the relevant glial and synaptic structures, leaving them largely out of reach for conventional light microscopic approaches such as confocal and two-photon microscopy. Hence, most of what we know about the organization of the tripartite synapse is based on electron microscopy, which does not lend itself to investigating dynamic events and which cannot be carried out in parallel with functional assays. The development and application of superresolution microscopy for neuron–glia research is opening up exciting experimental opportunities in this regard. In this paper, we provide a basic explanation of the theory and operation of stimulated emission depletion (STED) microscopy, outlining the potential of this recent superresolution imaging modality for advancing our understanding of the morpho-functional interactions between astrocytes and neurons that regulate synaptic physiology.     

Investigation of the structure of two-phase flow model-media in bubble-column bioreactors

Summary By applying photographic, electrical conductivity, and electrooptical methods, the transverse variation of bubble size and velocity, the local gas holdup, and the local specific gas/liquid interfacial area were estimated in a bench scale bubble-column bioreactor containing distilled water. The liquid velocity profile, the transverse turbulence intensity variations, and the turbulence energy dissipation scale were also measured by a hot film turbulence probe and constant temperature anemometer technique.     

Investigation of the use of agricultural byproducts for fungal protein production

Cellulose and nutrient salts as well as potato pulp and potato protein liquor (PPL), were used as substrates for the cultivation of Chaetomium cellulolyticum in batch and repeated-batch operations. Using cellulose as the substrate a linear relationship existed between the rates of cell mass formation and acid production. The repeated-batch process was controlled by NaOH consumption using a simple computer model. When the production of cell mass and acid stopped because of a lack of substrate cellulose was fed into the reactor. This occurred within 10 min at which point no NaOH-feed was needed to maintain a constant pH. Repeated-batch operations yielded higher cell concentrations and productivities than batch operations. The relationship between the NaOH and H₂SO₄ consumed, and the fungal mass concentration was complex in cultivation media containing potato pulp and PPL, because various substrates were consumed by the fungus simultaneously and successively. Therefore, for repeated-batch cultivation a constant time interval was used. Repeated-batch cultivation of the fungus on potato pulp and PPL did not yield higher cell concentrations and productivities than did batch cultivation. With the optimal pulp-to-PPL ratio a maximum specific growth rate of 0.61 h¹ was obtained. These investigations indicate, that potato pulp and PPL are well suited to fungal protein production by Chaetomium cellulolyticum for fodder supplement.     

Immobilization of enzymes in liquid membranes for enantioselective hydrolysis

Summary The enantioselective hydrolysis of racemic 4-acetoxy-cyclopentenone by immobilized enzymes is described. Liquid membrane emulsions were used to encapsulate the enzyme. This technique combines the specific enzymatic reaction with a selective transport through the organic phase. The product (–)-4-hydroxy-cyclopentenone was produced with an enantiomeric excess of 82%. The immobilization techniques and all reaction steps, as well as a mathematical model for the complete process are discussed in this report.