Lipase-catalyzed esterification of lactic acid with straight-chain alcohols

Enzymatic synthesis of esters of lactic acid and straight-chain alcohols with different chain lengths (C₆–C₁₈) were investigated in batch reactions with hexadecanol (C₁₆) as the model alcohol. Cyclohexane was the best solvent for higher ester yields, and the best biocatalyst was the immobilized Candida antarctica lipase B (Novozym 435) as well as the textile-immobilized Candida sp. lipase. A method was established to obtain ester yields in the range of 71 to 82% for the different alcohols, and the most favorable conditions for the esterification reaction using Novozym 435 were an equimolar ratio of lactic acid to alcohol, each at a concentration of 120 mM each; a 50°C reaction temperature; 190 rpm shaking speed; and the addition of 100 mg molecular sieves (4 Å) for drying. The ester yield increased with increasing lipase load, and a yield of 79.2% could be obtained after 24 h of reaction at 20 wt% of Novozym 435. The immobilized Candida sp. lipase prepared in the laboratory also could be used to produce esters of lactic acid and straight-chain alcohols, but it had a much lower activity than Novozym 435 with a temperature optimum of 40°C.     

Triglyceride selectivity of immobilized <Emphasis Type="Italic">Thermomyces lanuginosa</Emphasis> lipase in interesterification

The triglyceride (fatty acid) selectivity of an immobilized lipase from Thermomyces lanuginosa (Lipozyme TL IM) was investigated in lipase-catalyzed interesterification reactions between two nono-acid TG in n-hexane. Tristearin (tri-C18∶0) was used as a reference in a series of TG with saturated FA from tri-C4∶0 to tri-C20∶0, except for tri-C6∶0, and in a series of unsaturated FA from tri-C18∶1 to tri-C18∶3. The quantification was performed by HPLC, and different methods of selectivity evaluation were used. None of the methods used showed any significant differences between the performances of the lipase on the different TG, indicating that Lipozyme TL IM is nonselective toward FA or TG in the system used. A response surface design was used to investigate the influence of water activities (a _w ) and reaction temperatures on the reactivity of Lipozyme TL IM with a system of tripalmitin (tri-C16∶0) and trilaurin (tri-C12∶0) in n-hexane. An increase in temperature (40 to 60°C) was found to affect the reactivity of the lipase significantly. The reactivity of Lipozyme TL IM was unaffected by the change in a _w from 0.1130 to 0.5289. An increase in a _w only led to an increase in FFA formation.     

The potential of current high‐resolution imaging‐based particle size distribution measurements for crystallization monitoring

High‐speed, in situ video microscopy is a promising technology for measuring critical solid‐phase properties in suspension crystallization processes. This paper demonstrates the feasibility of high‐resolution, video‐imaging‐based particle size distribution (PSD) measurement by applying image analysis and statistical estimation tools to images from a simulated batch crystallization of an industrial photochemical. The results also demonstrate the ability to monitor important quality parameters, such as the ratio of nuclei mass to seed mass, that cannot be monitored by conventional technologies. General recommendations are given for achieving appropriate sampling conditions to enable effective imaging‐based PSD measurement. © 2009 American Institute of Chemical Engineers AIChE J, 2009     

GCase and LIMP2 Abnormalities in the Liver of Niemann Pick Type C Mice

The lysosomal storage disease Niemann–Pick type C (NPC) is caused by impaired cholesterol efflux from lysosomes, which is accompanied by secondary lysosomal accumulation of sphingomyelin and glucosylceramide (GlcCer). Similar to Gaucher disease (GD), patients deficient in glucocerebrosidase (GCase) degrading GlcCer, NPC patients show an elevated glucosylsphingosine and glucosylated cholesterol. In livers of mice lacking the lysosomal cholesterol efflux transporter NPC1, we investigated the expression of established biomarkers of lipid-laden macrophages of GD patients, their GCase status, and content on the cytosol facing glucosylceramidase GBA2 and lysosomal integral membrane protein type B (LIMP2), a transporter of newly formed GCase to lysosomes. Livers of 80-week-old Npc1^−/− mice showed a partially reduced GCase protein and enzymatic activity. In contrast, GBA2 levels tended to be reciprocally increased with the GCase deficiency. In Npc1^−/− liver, increased expression of lysosomal enzymes (cathepsin D, acid ceramidase) was observed as well as increased markers of lipid-stressed macrophages (GPNMB and galectin-3). Immunohistochemistry showed that the latter markers are expressed by lipid laden Kupffer cells. Earlier reported increase of LIMP2 in Npc1^−/− liver was confirmed. Unexpectedly, immunohistochemistry showed that LIMP2 is particularly overexpressed in the hepatocytes of the Npc1^−/− liver. LIMP2 in these hepatocytes seems not to only localize to (endo)lysosomes. The recent recognition that LIMP2 harbors a cholesterol channel prompts the speculation that LIMP2 in Npc1^−/− hepatocytes might mediate export of cholesterol into the bile and thus protects the hepatocytes.     

Model for microbiologically influenced corrosion potential assessment for the oil and gas industry

Corrosion is one of the major causes of failure in onshore and offshore oil and gas operations. Microbiologically influenced corrosion (MIC) is inherently more complex to predict, detect and measure because, for instance, the presence of biofilm and/or bacterial products is not sufficient to indicate active microbiological corrosion. The major challenge for current MIC models is to correlate factors that influence corrosion (i.e. chemical, physical, biological and molecular variables) with the potential of having MIC. Previous work has proposed the potential for MIC as a simple product of multiple factors, without fully considering the synergy or the interference among the factors. The present work proposes a network-based approach to analyse and predict MIC potential considering the complex interactions among a total of 60 influencing factors and 20 screening parameters. The proposed model has the ability to capture the complex interdependences and the synergic interactions of the factors used to assess MIC potential and uses an object-oriented approach based on a Bayesian Network. The model has been tested and verified using real data from a pipeline leakage incident that was a result of MIC. The proposed model constitutes a significant step in deepening the understanding of when MIC occurs and its predictability.

List of acronyms: APB: acid producing bacteria; Aw: water activity; BN: Bayesian network; MIC: microbiologically influenced corrosion; MMMs: molecular microbiological methods; NRB: nitrate-reducing bacteria; OOBN: object-oriented Bayesian network; PWRI: produced water re-injection; SPs: screening parameters; SRB: sulphate-reducing bacteria; SRPs: sulphate-reducing prokaryotes; TDSs: total dissolved solids     

Augmented semantic segmentation for the digitization of grinding tools based on deep learning

In order to analyze various process characteristics, grinding simulations can be used, which need accurate models of the tool and the individual grains. For this purpose, grinding tools can be digitized. To identify characteristic grains from a large number of measurements, each individual grain has to be analyzed and separated from the bond manually. Therefore, a deep learning-based methodology was developed to achieve a high segmentation accuracy of the grain boundaries efficiently. Additionally, a data augmentation approach was investigated to limit the data necessary for learning. The model transferability was quantified by analyzing different states of tool wear.     

Potentiometric determination of the chloride ion activity in cement based materials

The chloride content at the reinforcement is one of the decisive factors for the initiation and propagation of localised corrosion in concrete structures. A monitoring technique for the chloride concentration which is accurate, non-destructive and continuous would thus be highly desirable. For this reason, the performance of ion selective electrodes (ISEs) was investigated both in alkaline solutions and embedded in mortar. The Ag/AgCl electrodes used in this work showed Nernstian behaviour with a slope of –59 ± 1 mV per decade and a detection limit for chloride ions below 10^?2 mol dm^?3 even at pH close to 14; the selectivity coefficient for hydroxide interference was estimated at \( k_{{{\text{Cl}}^{ - } ,{\text{OH}}^{ - } }}^{\text{pot}} \approx 4 \cdot 10^{ - 3} \). The Ag/AgCl membranes show good long-term stability over more than 6 months even in highly alkaline solutions as long as chloride ions are present; in the complete absence of chloride the measured potentials were affected by the pH of the solution. The sensors are, however, able to recover fast as soon as they come into contact with chloride. When using ISEs embedded in concrete, diffusion potentials between the reference electrode and the ISE, as arising e.g. from gradients in pH, significantly affect the potential measurement and present a most important error source for the application of direct potentiometry to concrete. To minimise such errors, the reference electrode has to be positioned as close to the ISE as possible.     

In situ analysis of the strain evolution during welding using low transformation temperature filler materials

ABSTRACT

Compared to conventional welding consumables using low transformation temperature (LTT) filler materials is an innovative method to mitigate tensile residual stresses due to delayed martensite transformation of the weld. For the effective usage of LTT filler materials, a deeper understanding of the complex processes that lead to the final residual stress state during multi-pass welding is necessary. Transformation kinetics and the strain evolution of multi-pass welds during welding were investigated in situ at the beamline HEMS@PETRAIII, Germany. Compared to conventional welds, the total strain was reduced and compression strain was achieved when using LTT filler materials. For an optimal use of the LTT effect in the root of multi-pass welds, the alloying concept must be adapted taking care of dilution.     

Evaluation of the PSMA-Binding Ligand 212Pb-NG001 in Multicellular Tumour Spheroid and Mouse Models of Prostate Cancer

Radioligand therapy targeting the prostate-specific membrane antigen (PSMA) is rapidly evolving as a promising treatment for metastatic castration-resistant prostate cancer. The PSMA-targeting ligand p-SCN-Bn-TCMC-PSMA (NG001) labelled with ²¹²Pb efficiently targets PSMA-positive cells in vitro and in vivo. The aim of this preclinical study was to evaluate the therapeutic potential of ²¹²Pb-NG001 in multicellular tumour spheroid and mouse models of prostate cancer. The cytotoxic effect of ²¹²Pb-NG001 was tested in human prostate C4-2 spheroids. Biodistribution at various time points and therapeutic effects of different activities of the radioligand were investigated in male athymic nude mice bearing C4-2 tumours, while long-term toxicity was studied in immunocompetent BALB/c mice. The radioligand induced a selective cytotoxic effect in spheroids at activity concentrations of 3–10 kBq/mL. In mice, the radioligand accumulated rapidly in tumours and was retained over 24 h, while it rapidly cleared from nontargeted tissues. Treatment with 0.25, 0.30 or 0.40 MBq of ²¹²Pb-NG001 significantly inhibited tumour growth and improved median survival with therapeutic indexes of 1.5, 2.3 and 2.7, respectively. In BALB/c mice, no signs of long-term radiation toxicity were observed at activities of 0.05 and 0.33 MBq. The obtained results warrant clinical studies to evaluate the biodistribution, therapeutic efficacy and toxicity of ²¹²Pb-NG001.