The impact of lipases on the rheological behavior of colloidal silica nanoparticle stabilized Pickering emulsions for biocatalytical applications

The use of Pickering emulsions for biocatalytical applications has recently received increased attention in cases where hydrophobic reactants are involved. For process applications, knowledge of the emulsion’s rheology is crucial for the fluid dynamical design of equipment and selection of operating conditions. Colloidal silica nanoparticle stabilized Pickering emulsions usually exhibit shear-thinning behavior caused by a complex particle-particle network. While this has been observed by many authors, no publication has yet dealt with the rheology of silica nanoparticle stabilized Pickering emulsions containing enzymes. Thus, the aim of this study was to investigate the impact of the commonly used biocatalyst lipase (type and concentration), the dispersed phase volume fraction and the silica particle concentration on the rheological behavior of water-in-oil Pickering emulsions. For this purpose, the impact of the named parameters on the viscosity curves were measured. Lipases reduced the viscosities and transferred the rheological behavior from shear-thinning to Newtonian, which might be due to interactions of the lipase molecules via the formation of intermolecular disulfide bonds, which disturb the hydrogen-bond based silica particle-particle network. However, by increasing the dispersed phase volume fraction or the silica particle concentration the rheological behavior of emulsions became again shear-thinning. This work will help to produce bioactive Pickering emulsions with tailor-made characteristics.BMBF, 031A163A, Basistechnologien Forschertandem: Modularisierte mehrphasige Biokatalyse durch enzymatisch aktive w/o Pickering Emulsionen im Membranreaktor (BioPICK

Met zijn allen aan de dialoogtafel

Sinds januari 2015 zijn de gemeenten verantwoordelijk voor de inrichting, organisatie en uitvoering van alle jeugdhulp. Daarbij maken de gemeenten verschillende keuzes. Maar het is onduidelijk of en hoe deze keuzen bijdragen aan de transformatiedoelen. Er zijn namelijk weinig best practices waarop gemeenten hun keuzes kunnen baseren. Dit maakt de transformatie jeugd een maatschappelijk experiment dat niet alleen kansen biedt om de jeugdhulp te verbeteren, maar ook risico’s met zich meebrengt. Denk daarbij aan meer ongelijkheid in zorgverlening, onzekerheid, coördinatie- en afstemmingsproblemen of onvoldoende transparantie (o.a. Vrangbaek, 2007; Kinderombudsman, 2016)

Towards recombinantly produced milk proteins: Physicochemical and emulsifying properties of engineered whey protein beta-lactoglobulin variants

DFG, 273937032, SPP 1934: Dispersitäts-, Struktur- und Phasenänderungen von Proteinen und biologischen Agglomeraten in biotechnologischen ProzessenBMBF, 031B0222, Basistechnologie Nachwuchsgruppe "Multiskalige Modellierung und Modifikation von Multienzymkomplexen als Basistechnologie für zellfreie Reaktionskaskaden" (II

Filtrierbarkeit und rheologisches Verhalten von Lipase-enthaltenden und mit Silika-Partikel stabilisierten Wasser-in-Öl Pickering Emulsionen für die Anwendung von kontinuierlicher Zweiphasen-Biokatalyse im Membranreaktor

The technical application of biocatalysts is commonly realized in aqueous media limiting their application to hydrophilic compounds; however, most relevant substrates and products are hydrophobic. To overcome this, the use of two-phase systems such as Pickering emulsions presents a promising alternative. In Pickering emulsions, biocatalysts are immobilized in water droplets stabilized by nanoparticles and those water droplets are surrounded by an organic solvent containing the substrates and the products. Pickering emulsions have been successfully employed for two-phase biocatalysis in batch processes. Nevertheless, for their industrial up-scaling, a continuous process with an efficient liquid/liquid phase separation and enzyme recovery is required. The aim of this thesis is to evaluate the feasibility of using a continuous membrane reactor for two-phase biocatalysis in water-in-oil Pickering emulsions: the ultrafiltration membrane rejects the water droplets containing the biocatalyst while the organic phase containing the product is filtered through the membrane. To reach this aim the interplay between the physico-chemical properties of Pickering emulsions and the filterability must be characterized in detail. Hence, the impact of the type of lipase, concentration and type of nanoparticles on the (i) drop size distribution, (ii) rheological character and (iii) filterability of bioactive water-in-oil Pickering emulsions was investigated. The addition of lipases to the Pickering emulsion decreased the droplet size, reduced the viscosity and improved the filterability of the Pickering emulsion. All these observed effects might be due to protein-protein interactions of the lipases via disulfide bonds. The higher the particle concentration is the smaller the mean droplet size is. However, an increase in the particle concentration decreased the filterability which might be due to unbound particles forming the filter cake and increased the viscosity. Thus, the used particle concentration should be minimized. Regarding the type of particles, the use of colloidal particles decreased the droplet size and improved the filterability of bioactive water-in-oil Pickering emulsions. Finally, a continuous biocatalysis in a membrane reactor at constant flux was performed at industrial relevant hydraulic residence time reaching an operation time of 30 h maintaining the enzymatic activity. This overall result of the thesis is the first step towards scalable continuous two-phase biocatalysis in Pickering emulsions.Die technische Anwendung von Biokatalysatoren wird im Allgemeinen in wässrigen Medien realisiert, wodurch der Bereich der Reaktanten auf hydrophile Verbindungen begrenzt wird. Die Verwendung von zweiphasigen Pickering Emulsionen stellt eine vielversprechende Alternative dar, um diese Limitierung zu überwinden. In Pickering Emulsionen sind die Biokatalysatoren in mit Nanopartikeln stabilisierten Wassertröpfchen immobilisiert, welche dann von einem organischen Lösungsmittel umgeben sind, in dem die hydrophoben Substrate und Produkte gelöst sind. Pickering Emulsionen wurden bereits erfolgreich für zweiphasige biokatalytische Reaktionen in Batch-Prozessen verwendet. Jedoch wurde bisher noch kein effizienter und kontinuierlicher Prozess zur Trennung der Flüssig-Flüssig-Phasen und zur Recyclisierung der Biokatalysatoren beschrieben. Das Ziel dieser Arbeit ist es, die Nutzbarkeit eines kontinuierlichen Membranreaktors für die zweiphasige Biokatalyse in Wasser-in-Öl Pickering Emulsionen zu untersuchen. Die Membran hält die Wassertropfen mit den darin immobilisierten Biokatalysatoren zurück, während die organische Phase mit den darin gelösten Produkten durch die Membran filtriert wird. Um dieses Ziel zu erreichen, ist es notwendig, das Zusammenspiel zwischen den physikalisch-chemischen Eigenschaften einer Pickering Emulsion und der Filtrierbarkeit zu charakterisieren. Hierfür wurden die Einflüsse der Art der Lipase, der Konzentration sowie der Art der Nanopartikel auf die Tropfengrößenverteilung, den rheologischen Charakter und die Filtrierbarkeit von bioaktiven Wasser-in-Öl Pickering Emulsionen untersucht. Die Zugabe von Lipasen zu der Pickering Emulsion reduzierte die Tropfengröße, verringerte die Viskosität und steigerte die Filtrierbarkeit der Pickering Emulsionen. Es kann begründet vermutet werden, dass alle diese beobachteten Effekte auf Protein-Protein-Wechselwirkungen der Lipase über Disulfidbindungen zurückzuführen sind. Höhere Partikelkonzentrationen erhöhten die Stabilität von Emulsionen. Jedoch steigerte die höhere Partikelkonzentration die Viskosität und senkte den Fluss durch die Membran, vermutlich aufgrund ungebundener Partikel, die einen dichten Filterkuchen bildeten. Daher sollte die Partikelkonzentration so gering wie möglich gehalten werden. In Bezug auf die Art der verwendeten Partikel (sphärisch oder kolloidal) führte die Verwendung von kolloidalen Partikeln zu kleineren Tropfengrößen und höherer Filtrierbarkeit. Abschließend wurde eine kontinuierliche Biokatalyse in einem Membranreaktor bei konstantem Fluss, d. h. konstanter Verweilzeit, und bei industriell relevanter Verweilzeit durchgeführt. Die Substrat- und Produktkonzentrationen waren konstant und reproduzierbar und das Enzym war nach 30 Stunden noch aktiv. Dieses Gesamtergebnis der Arbeit ist der erste Schritt in Richtung einer skalierbaren kontinuierlichen zweiphasigen Biokatalyse in Pickering Emulsionen.BMBF, 031A163A, Basistechnologien Forschertandem: Modularisierte mehrphasige Biokatalyse durch enzymatisch aktive w/o Pickering Emulsionen im Membranreaktor (BioPICK

Incidence of severe critical events in paediatric anaesthesia (APRICOT): a prospective multicentre observational study in 261 hospitals in Europe

Background Little is known about the incidence of severe critical events in children undergoing general anaesthesia in Europe. We aimed to identify the incidence, nature, and outcome of severe critical events in children undergoing anaesthesia, and the associated potential risk factors. Methods The APRICOT study was a prospective observational multicentre cohort study of children from birth to 15 years of age undergoing elective or urgent anaesthesia for diagnostic or surgical procedures. Children were eligible for inclusion during a 2-week period determined prospectively by each centre. There were 261 participating centres across 33 European countries. The primary endpoint was the occurence of perioperative severe critical events requiring immediate intervention. A severe critical event was defined as the occurrence of respiratory, cardiac, allergic, or neurological complications requiring immediate intervention and that led (or could have led) to major disability or death. This study is registered with ClinicalTrials.gov, number NCT01878760. Findings Between April 1, 2014, and Jan 31, 2015, 31 127 anaesthetic procedures in 30 874 children with a mean age of 6.35 years (SD 4.50) were included. The incidence of perioperative severe critical events was 5.2% (95% CI 5.0-5.5) with an incidence of respiratory critical events of 3.1% (2.9-3.3). Cardiovascular instability occurred in 1.9% (1.7-2.1), with an immediate poor outcome in 5.4% (3.7-7.5) of these cases. The all-cause 30-day in-hospital mortality rate was 10 in 10 000. This was independent of type of anaesthesia. Age (relative risk 0.88, 95% CI 0.86-0.90; p<0.0001), medical history, and physical condition (1.60, 1.40-1.82; p<0.0001) were the major risk factors for a serious critical event. Multivariate analysis revealed evidence for the beneficial effect of years of experience of the most senior anaesthesia team member (0.99, 0.981-0.997; p<0.0048 for respiratory critical events, and 0.98, 0.97-0.99; p=0.0039 for cardiovascular critical events), rather than the type of health institution or providers. Interpretation This study highlights a relatively high rate of severe critical events during the anaesthesia management of children for surgical or diagnostic procedures in Europe, and a large variability in the practice of paediatric anaesthesia. These findings are substantial enough to warrant attention from national, regional, and specialist societies to target education of anaesthesiologists and their teams and implement strategies for quality improvement in paediatric anaesthesia

Incidence of severe critical events in paediatric anaesthesia (APRICOT): a prospective multicentre observational study in 261 hospitals in Europe

Background Little is known about the incidence of severe critical events in children undergoing general anaesthesia in Europe. We aimed to identify the incidence, nature, and outcome of severe critical events in children undergoing anaesthesia, and the associated potential risk factors. Methods The APRICOT study was a prospective observational multicentre cohort study of children from birth to 15 years of age undergoing elective or urgent anaesthesia for diagnostic or surgical procedures. Children were eligible for inclusion during a 2-week period determined prospectively by each centre. There were 261 participating centres across 33 European countries. The primary endpoint was the occurence of perioperative severe critical events requiring immediate intervention. A severe critical event was defined as the occurrence of respiratory, cardiac, allergic, or neurological complications requiring immediate intervention and that led (or could have led) to major disability or death. This study is registered with ClinicalTrials.gov, number NCT01878760. Findings Between April 1, 2014, and Jan 31, 2015, 31â127 anaesthetic procedures in 30â874 children with a mean age of 6·35 years (SD 4·50) were included. The incidence of perioperative severe critical events was 5·2% (95% CI 5·0â5·5) with an incidence of respiratory critical events of 3·1% (2·9â3·3). Cardiovascular instability occurred in 1·9% (1·7â2·1), with an immediate poor outcome in 5·4% (3·7â7·5) of these cases. The all-cause 30-day in-hospital mortality rate was 10 in 10â000. This was independent of type of anaesthesia. Age (relative risk 0·88, 95% CI 0·86â0·90; p<0·0001), medical history, and physical condition (1·60, 1·40â1·82; p<0·0001) were the major risk factors for a serious critical event. Multivariate analysis revealed evidence for the beneficial effect of years of experience of the most senior anaesthesia team member (0·99, 0·981â0·997; p<0·0048 for respiratory critical events, and 0·98, 0·97â0·99; p=0·0039 for cardiovascular critical events), rather than the type of health institution or providers. Interpretation This study highlights a relatively high rate of severe critical events during the anaesthesia management of children for surgical or diagnostic procedures in Europe, and a large variability in the practice of paediatric anaesthesia. These findings are substantial enough to warrant attention from national, regional, and specialist societies to target education of anaesthesiologists and their teams and implement strategies for quality improvement in paediatric anaesthesia. Funding European Society of Anaesthesiology