Hoog Antink, Marieke Melanie
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Hoog Antink, Marieke Melanie
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Hoog Antink, Marieke Melanie
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Item-typ:Veröffentlichung, Proteolytic ceramic capillary membranes for the production of peptides under flow(Elsevier, 2019-04-15); ; ; ; In this study, we investigate the effect of membrane surface functionalization on the immobilization of the protease subtilisin A and its performance in the production of peptides from the model protein casein under flow. The surface of tubular ceramic membranes was silanized to yield carboxylated and aminated supports for enzyme immobilization via non-covalent and carbodiimide activated binding. The protease density correlated with electrostatic interactions between the positively charged enzyme and the supports, with the highest enzyme density reached on negatively charged, carboxylated membranes (0.019 molecules/nm², noncovalent approach). Enzyme leaching was reduced by covalent binding of protease to carboxylated supports (5% leached) and slightly improved by binding to aminated membranes (46%) over non-covalent binding to unfunctionalized reference capillaries (66%). Regarding carbodiimide activated immobilization, protease on unfunctionalized and aminated supports exhibited a significantly larger specific activity (0.99 μmol/min/mg) than enzymes on carboxylated surfaces (0.15 μmol/min/mg), which suggests preferred enzyme orientation. In protein hydrolysis, these differences in surface-enzyme interactions were reflected by variations in peptide composition and degree of hydrolysis. Accordingly, we demonstrate that surface functionalization critically determines the surface properties of protease support materials for the production of peptides under flow and allows tailoring the performance of proteolytic capillary membranes.Wissenschaftlicher ArtikelBand:147119 97 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, Porous ceramics with tailored pore size and morphology as substrates for coral larval settlement(Elsevier, 2018-08-07); ; ; ; The growing demand for stony corals as ornamental aquarium animals requires defined aquacultural breeding strategies. For the sexual propagation of corals, material substrates are needed, that attract larvae and support their settlement and development. In this study, five types of highly porous ceramic materials were developed following the example of coral skeleton. The applicability of these settlement substrates was tested using larvae of the stony coral Pocillopora damicornis. Partial sintering of pressed clay pellets, freeze casting of clay and alumina-mullite based slurries and direct foaming of high alkane phase emulsified suspensions (HAPES) using alumina were employed. By the addition of mm-sized spherical polystyrene beads as sacrificial templates during freeze casting (alumina-mullite), superficial pores in the size of the larvae were created. The inorganic substrates featured open porosities between 35% (pressed clay) and 83% (foamed alumina), pore sizes ranging from nm to mm-scale and pore morphologies dominated by interparticle porosity (pressed), lamellar pores (freeze casting) and cellular pore types (direct foaming). The ceramic substrates were incubated in artificial sea water for 3 months to induce necessary biofilm formation and algae growth. Afterwards, individual substrates were exposed to 5 coral larvae, and their settlement behavior was monitored over 14 days. At the end of this period, all ceramic materials were successfully accepted as settlement substrates, with a mean settlement rate of 46.2%, and no significant differences between the substrate types. On samples with large surface superficial pores, a significantly reduced survival of settled larvae (79%) compared to the other porous materials (93–98%) was determined, suggesting a non-ideal surface topography. While alumina foam samples (HAPES) exhibit the most promising results in terms of settlement and survival of larvae, clay-based substrates provide a more economic solution for the sexual propagation of corals in aquaculture.Wissenschaftlicher ArtikelBand:44Heft:14121 172 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, Aluminium acetate as alternative cross-linker for temperature controlled gel-casting and joining of ceramics(Elsevier, 2016-01-15); ; ; ; In an earlier established gel-casting process, the biopolymer alginate is cross-linked with Ca2+-ions released through the temperature controlled dissolution of calcium iodate-particles (Ca(IO3)2). In this study, aluminum acetate (AlAc) is compared to Ca(IO3)2 as an alternative temperature controlled cross-linker for an alginate–alumina slurry. Both cross-linkers are characterized regarding gel-forming properties, resulting microstructure, impurities, mechanics of sintered parts and the ability of joining ceramic blocks in the green state via connecting gelation with and without adding slurry. Rheological measurements show that both cross-linker have a similar gelling behavior and lead to gelled blocks of high quality. AlAc-particle create a denser and more homogenous microstructure, while Ca(IO3)2-particles induce pores, abnormal grain growth and lower mechanical values. Nevertheless Ca(IO3)2 shows excellent joining properties which makes it a suitable alternative to pressure joining. In summary, AlAc is an excellent alternative cross-linker but Ca(IO3)2 remains the method of choice for joining gelled bodies.Wissenschaftlicher ArtikelBand:36Heft:5124 122