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Fluid hydrodynamic stress has a deterministic effect on the morphology of filamentous fungi. Although the coaxial mixer has been recognized as a suitable gas dispersion system for minimizing inhomogeneities within a bioreactor, its performance for achieving enhanced oxygen transfer while operating at a reduced shear environment has not been investigated yet, specifically upon scale-up. Therefore, the influence of the impeller type, aeration rate, and central impeller retrofitting on the efficacy of an abiotic coaxial system containing a shear-thinning fluid was examined. The aim was to assess the hydrodynamic parameters, including stress, mass transfer, bubble size, and gas hold-up, upon conducting a scale-up study. The investigation was conducted through dynamic gassing-in, tomography, and computational fluid dynamics combined with population balance methods. It was observed that the coaxial bioreactor performance was strongly influenced by the agitator type. In addition, coaxial bioreactors are scalable in terms of shear environment and oxygen transfer rate., (© 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

The aim of the current research study is to conduct a comparative assessment of biocompatibility of zwitterionic-coated polyether sulfone (PES) clinical hemodialysis (HD) membranes using both theoretical and experimental methods. Fibrinogen plays a key role in assessing membrane hemocompatibility since its membrane-surface adsorption triggers several biological reactions, complete thrombosis and embolism. As a result, adsorption of fibrinogen on the untreated PES surface and novel synthesized PES coated with poly 3-((3-(3-carboxy-2,5-dimethyltridecanamido) propyl) dimethylammonio) propane-1-sulfonate as a zwitterion (ZW) was compared. Specifically, the comparison was conducted using in situ synchrotron based micro computed tomography imaging (SR-μCT), Attenuated Total Reflection Fourier Transform Infrared (ATR-FTIR) spectroscopy, and Scanning Electron Microscopy (SEM). The in situ SR-μCT showed that fibrinogen adsorption and membrane fouling were intense on PES membrane surface. However, there was insignificant fouling in the middle layer of zwitterion coated PES membrane (PES-ZW). Moderate shifting of peaks was observed in ATR-FTIR spectra of the adsorbed fibrinogen when compared to the bulk protein spectra, which may be due to the conformational transformations occurring during the adsorption process. The spectral features indicate that PES-ZW surface has a lower adsorption affinity for fibrinogen than that for the PES surface. In this innovative study, the use of molecular modeling docking to evaluate the interaction of fibrinogen active pose with PES-ZW and PES models with the aim of gaining an in depth understanding of the functional group responsible for the interactions was explored. The PES and PES/zwitterion hemodialysis membrane models indicated minimum binding energies with fibrinogen by -6.00 and -6.70 kcal/mol, respectively. Docking studies thus suggest that the membrane's sulfone functional groups play an essential key role during the fibrinogen interaction and adsorption. The HD patients' uremic samples were incubated in vitro with PES and PES-ZW membranes for the inflammatory biomarkers released of Serpin/Antithrombin-III, Properdin, C5a, IL-1α, IL-1β, TNF-α, and IL6. This study's results emphasize that even though a neutral charge of synthesized novel zwitterion PES, which enhances biocompatibility, the sulfone group still significantly affected the interactions with fibrinogen., Competing Interests: Declaration of competing interest No conflict of interest to declare., (Copyright © 2020 Elsevier B.V. All rights reserved.)

End stage renal disease (ESRD) patients depend on hemodialysis (HD) as a life-sustaining treatment, but HD membrane properties play a critical role in blood activation during HD and can lead to severe patient outcomes. This study reports on a series of investigations on the common clinical HD membranes available in Canadian hospitals to explore the key reasons behind their susceptibility to blood activation and unstable cytokine. Clinical HD membranes composed of cellulose triacetate (CTA) and polyvinylpyrrolidone: polyarylethersulfone (PAES: PVP) were thoroughly characterized in terms of morphology and chemical composition. Membrane-surface interactions with uremic blood samples after HD treatment were probed using Fourier Transform Infra-Red (FTIR) and Raman spectroscopic techniques in order to understand changes in chemistry on membrane fibers. In addition, as part of this innovative study, we utilized Molecular Modeling Docking to examine the interactions of human blood proteins and membrane models to gain an in-depth understanding of functional group types responsible for perceived interactions. In-vitro adsorption of fibrinogen on different clinical HD membranes was compared at similar clinical operating conditions. Samples were collected from dialysis patients to ascertain the extent of inflammatory biomarkers released, before, during (30 and 90 min) and after dialysis (4 h). Collected blood samples were analyzed using Luminex assays for the inflammatory biomarkers of Serpin/Antithrombin-III, Properdin, C5a, 1L-1α, 1L-1β, TNF-α, IL6, and vWF. We have likewise incubated uremic blood in vitro with the two membrane materials to determine the impact that membrane materials pose in favor of activation away from the hydrodynamics influences. The results of our morphological, chemical, spectroscopic, and in vitro incubation analyses indicate that CTA membranes have a smoother surface and higher biocompatibility than PAES: PVP membranes, however, it has smaller pore size distribution, which results in poor clearance of a broad spectrum of uremic toxins. However, the rougher surface and greater hydrophilicity of PAES: PVP membranes increases red blood cell rupture at the membrane surface, which promotes protein adsorption and biochemical cascade reactions. Molecular docking studies indicate sulfone functional groups play an important role in the adsorption of proteins and receptors. PAES: PVP membranes result in slower but greater adsorption of fibrinogen, but are more likely to experience reversible and irreversible fouling as well as backfiltration. Our major finding is that a single dialysis session, even with a more biocompatible membrane such as CTA, increases the levels of complement and inflammation factors, but to a milder extent than dialysis with a PAES membrane.

Wheat straw is a low-cost feedstock for the production of biofuel. Pretreatment process is an important stage in producing biofuels since it makes the fibers more accessible to enzymatic hydrolysis which is the final step of producing biofuels. Pretreated wheat straw (PWS) slurries are non-Newtonian fluids with yield stress. Mixing of fluids exhibiting yield stress such as the pretreated wheat straw slurry results in the generation of cavern, which is a fully-mixed zone, around the impeller and the stationary regions elsewhere, which causes difficulties in the production of biofuels. In this study, the non-invasive electrical resistance tomography technique was utilized to determine the cavern dimensions as a function of the impeller type and impeller speed. The cavern sizes were then used to measure the yield stress of PWS slurries as a function of fiber size (≤ 2 and ≤ 6 mm) and fiber concentration (6, 8, and 10 wt%).

The hydrodynamics of gas-liquid two-phase flow in a single-use bioreactor were investigated in detail both experimentally and numerically. Electrical resistance tomography (ERT) and dynamic gas disengagement (DGD) combined with computational fluid dynamics (CFD) were employed to assess the effect of the volumetric gas flow rate and impeller speed on the gas-liquid flow field, local and global gas holdup values, and Sauter mean bubble diameter. From the results obtained from DGD coupled with ERT, the bubble sizes were determined. The experimental data indicated that the total gas holdup values increased with increasing both the rotational speed of impeller and volumetric gas flow rate. Moreover, the analysis of the flow field generated inside the aerated stirred bioreactor was conducted using CFD results. Overall, a more uniform distribution of the gas holdup was obtained at impeller speeds ≥ 100 rpm for volumetric gas flow rates ≥ 1.6 × 10 -5  m 3 /s.

Degradation and mineralization of aqueous methylene blue (MB) are investigated in a bench scale external loop airlift sonophotoreactor. A central composite design along with response surface methodology is employed to model and optimize the sonophotolytic process. A quadratic empirical expression between responses and independent variables (pH and initial concentrations of H2O2 and MB) is derived. The efficiencies of the system for the MB degradation after 10, 15, and 30 min, and total organic carbon reduction after 150 min are considered as responses. The analysis of variance performed high values for the coefficient of determination R(2) and adjusted R(2) for all four responses. Optimum values of process variables for the maximum degradation and mineralization efficiency are pH 6.6 and initial concentrations of H2O2 and MB are 1,280 and 10.56 mg/L, respectively. With optimal operating conditions, 99.93% and 55.32% MB removal (after 10 min) and TOC reduction (after 150 min) are achieved, respectively. Artificial neural networks are also used to model the experimental data. The respirometric study is conducted to compare the biodegradability of untreated and sonophotolytically pre-treated MB solutions at different reaction times. Pre-treated solutions at 180, 240, and 300 min performed higher biodegradability compared to those of untreated MB solutions.

Application of ozone technology to lignocellulosic biohydrogen production was explored with a barley straw. Ozone pretreatment effectively degraded the straw lignin and increased reducing sugar yield. A simultaneous enzyme hydrolysis and dark fermentation experiment was conducted using a mixed anaerobic consortium together with saccharification enzymes. Both untreated and ozonated samples produced hydrogen. Compared to the untreated group, hydrogen produced by the groups ozonated for 15, 30, 45 and 90 min increased 99%, 133%, 166% and 94%, respectively. Some inhibitory effect on hydrogen production was observed with the samples ozonated for 90 min, and the inhibition was on the fermentative microorganisms, not the saccharification enzymes. These results demonstrate that production of biohydrogen from barley straw, a lignocellulosic biomass, can be significantly enhanced by ozone pretreatment., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

The present study summarizes results of mixing characteristics in a draft tube airlift bioreactor using ERT. This technique offers the possibility for noninvasive and nonintrusive visualization of flow fields in the bioreactor and has rarely been utilized previously to analyze operating parameters and mixing characteristics in this type of bioreactors. Several operating parameters and geometric characteristics were examined. In general, results showed that the increase in superficial gas velocity corresponds to an increase in energy applied and thus, to a decrease in mixing time. This generally corresponded to an increase in liquid circulation velocity and shear rate values. Bottom clearances and draft tube diameters affected flow resistance and frictional losses. The influence of sparger configurations on mixing time and liquid circulation velocity was significant due to their effect on gas distribution. However, the effect of sparger configuration on shear rate was not significant, with 20% reduction in shear rates using the cross-shaped sparger. Fluid viscosity showed a marked influence on both mixing times and circulation velocity especially in the coalescing media of sugar and xanthan gum (XG) solutions. Results from this work will help to develop a clear pattern for operation and mixing that can help to improve several industrial processes, especially the ones related to emerging fields of technology such as the biotechnology industry.