Modelling of immobilised enzyme biocatalytic membrane reactor performance

Immobilised enzyme-catalysed conversions frequently provide specific advantages of selectivity overchemical conversions and further, facilitate continuous operation through biocatalyst retention andreuse. This study focuses on the development and modelling of an enzyme-catalysed continuous immo-bilised enzyme biocatalytic membrane reactor (BMR). The conversion of the amidase-catalysed lactamideto lactic acid process was used as an industrially representative system with which to evaluate the processperformance of the BMR.The model was developed from unsteady state differential mass balances incorporating a second orderenzyme decay. This model was validated from empirically determined conversions in dual experimentsusing 80 and 40 mM amide substrate, 6.4 and 20.1 mg immobilised amidase and a flow rate of 0.0005 and0.0001 L/min respectively.Model predictions over a range of amidase amounts and stabilities, flow rates and initial amide con-centrations quantified the direction and extent of the influence of these parameters on the maximumconversions attainable, consequently identifying the critical parameter ranges defining optimal BMR per-formance. Although the model has been developed and validated for the prediction of BMR performanceof the specific lactamide-lactic acid system, it nevertheless has broad applicability for and relevance tobroad-based prediction of the performance of immobilised enzyme BMR processes in general, irrespectiveof the specific enzyme or substrate moieties.This work is based on research supported by the National Research Foundation (NRF),South Africa (SA). The authors gratefully acknowledge funding from the NRF and Stellenbosch University, SA. R du Preez acknowledges bursary funding from the NRF.http://www.elsevier.com/locate/molcatbhb2016Chemical Engineerin

Association of bovine leptin polymorphisms with energy output and energy storage traits in progeny tested Holstein-Friesian dairy cattle sires

peer-reviewedBackground: Leptin modulates appetite, energy expenditure and the reproductive axis by signalling via its receptor the status of body energy stores to the brain. The present study aimed to quantify the associations between 10 novel and known single nucleotide polymorphisms in genes coding for leptin and leptin receptor with performance traits in 848 Holstein-Friesian sires, estimated from performance of up to 43,117 daughter-parity records per sire. Results: All single nucleotide polymorphisms were segregating in this sample population and none deviated (P > 0.05) from Hardy-Weinberg equilibrium. Complete linkage disequilibrium existed between the novel polymorphism LEP-1609, and the previously identified polymorphisms LEP-1457 and LEP-580. LEP-2470 associated (P < 0.05) with milk protein concentration and calf perinatal mortality. It had a tendency to associate with milk yield (P < 0.1). The G allele of LEP-1238 was associated (P < 0.05) with reduced milk fat concentration, reduced milk protein concentration, longer gestation length and tended to associate (P < 0.1) with an increase in calving difficulty, calf perinatal mortality and somatic cells in the milk. LEP-963 exhibited an association (P < 0.05) with milk fat concentration, milk protein concentration, calving difficulty and gestation length. It also tended to associate with milk yield (P < 0.1). The R25C SNP associated (P < 0.05) with milk fat concentration, milk protein concentration, calving difficulty and length of gestation. The T allele of the Y7F SNP significantly associated with reduced angularity (P < 0.01) and reduced milk protein yield (P < 0.05). There was also a tendency (P < 0.1) for Y7F to associate with increased body condition score, reduced milk yield and shorter gestation (P < 0.1). A80V associated with reduced survival in the herd (P < 0.05). Conclusions Several leptin polymorphisms (LEP-2470, LEP-1238, LEP-963, Y7F and R25C) associated with the energetically expensive process of lactogenesis. Only SNP Y7F associated with energy storage. Associations were also observed between leptin polymorphisms and calving difficulty, gestation length and calf perinatal mortality. The lack of an association between the leptin variants investigated with calving interval in this large data set would question the potential importance of these leptin variants, or indeed leptin, in selection for improved fertility in the Holstein-Friesian dairy cow.Department of Agriculture, Food and Fisheries, Ireland - Research Stimulus Fund (RSF-06-0353; RSF-06-0409); Irish Dairy Research Trust; Teagasc Walsh Fellowshi

Reaction Kinetics of CO₂ with Monoethanolamine in <i>n</i>‑Propanol. 1. Reaction Kinetic Data and Comparison with Existing Rate Law Expressions

The reaction kinetics of CO₂ with monoethanolamine is of industrial significance with respect to both CO₂ sequestration applications and characterizing the effective interfacial mass transfer area of packed separation columns. Reaction kinetic data were previously, by necessity, only measured under pseudo-first-order conditions with respect to CO₂. Furthermore, mass-transfer limitations encountered by the heterogeneous techniques restricted the validity range of the reaction kinetic models developed from the data. New reaction kinetic data, independent of mass-transfer limitations and outside pseudo-first-order conditions, are presented. The data, collected via a previously developed novel, in situ FTIR technique, were subsequently compared with the predictions of two widely accepted rate expressions, the power rate law and pseudo-steady-state hypothesis (PSSH) rate law. The expressions were modeled on the data using a novel multiobjective goal attainment algorithm also developed in this study. The PSSH rate law predictions were in closer agreement with the data than the power rate law, but both rate expressions were found to be unable to accurately describe the reaction kinetics of CO₂, proving that they should be used with caution outside of the pseudo-first-order conditions of their derivation. It was, therefore, concluded that a rate law able to describe the reaction kinetics for all reaction conditions should include the zwitterion reaction intermediate concentration in its fundamentally derived rate expression(s)

Continuous Flow Preferential Hydrogenation of an Octanal/Octene Mixture Using Cu/Al₂O₃ Catalysts

γ-Alumina-supported catalysts with varying copper loadings (5–25 wt %) were prepared by incipient wet impregnation and characterized by various characterization techniques. These catalysts were tested for the selective hydrogenation of octanal in a mixture containing 10 wt % octanal and 2 wt % octene diluted in octanol. The reactions were carried out in a continuous flow fixed-bed reactor in a down flow mode with varying pressures, liquid hourly space velocities, and hydrogen (H₂)-to-aldehyde molar ratios. The catalyst activities were assessed over a temperature range between 100 and 180 °C using hydrogen gas as the hydrogen source. The results obtained showed that under these experimental conditions, copper preferentially hydrogenates the aldehyde and the copper content exhibited no significant influence on the catalyst activity or product selectivity. Kinetic modeling revealed that both octanal and octene hydrogenation were first-order reactions, although octene conversion was very low until octanal conversion had reached a significant level. The activation energy for octanal hydrogenation is higher than the octene hydrogenation. A maximum octanal conversion of >99% was obtained at 160 °C, and the best selectivity toward octanol of 99% was achieved at 100 °C (53% conversion). The pressure played a small role with regards to octanal conversion and selectivity toward octanol, whereas it exhibited a significant influence on the octene conversion. Increasing the hydrogen-to-aldehyde ratio was found to have a direct influence on both octanal and octene conversion

A homozygous frameshift mutation in the mouse Flg gene facilitates enhanced percutaneous allergen priming

Loss-of-function mutations in the filaggrin gene (FLG), cause the semi-dominant keratinizing disorder, ichthyosis vulgaris1, and convey major genetic risk to atopic dermatitis/eczema, eczema-associated asthma2,3 and other allergic phenotypes5. Several low frequency FLG null alleles occur in Europeans and Asians, with a cumulative frequency of ~9% in Europe4. Here we report a 1-bp deletion mutation, 5303delA, highly analogous to common human FLG mutations, within the murine flg gene in the spontaneous mouse mutant flaky tail (ft). Importantly, we demonstrate that topical application of allergen to mice homozygous for this mutation results in cutaneous inflammatory infiltrates and enhanced cutaneous allergen priming with development of allergen-specific antibody responses. These data validate ft as a useful model of filaggrin deficiency and provide experimental evidence for the hypothesis that antigen transfer through a defective epidermal barrier is a key mechanism underlying elevated IgE sensitization and initiation of cutaneous inflammation in humans with filaggrin-related atopic disease