Chemical and Bioprocess Engineering Research Collection

Chemically resistant parts for flow chemistry, with integrated mixing elements have been produced using the 3D printing process of fused filament fabrication, from poly(etheretherketone). Poly(etheretherketone) has greater chemical resistance than common fused filament fabrication materials such as acrylonitrile butadiene styrene, polypropylene, or even high-performance plastics like poly(etherimide), in addition to having superior thermal resistance and excellent mechanical strength. Printed reactors were demonstrated to be suitable for liquid–liquid extraction and flow chemistry and to be capable of withstanding pressures of at least 30 bar allowing superheated solvents to be used. Burst tests in simple geometries of 20 minute duration have indicated that increased operating pressures of up to 60 bar could be accommodated in future reactor designs. The ability to use fused filament fabrication for these reactors allows highly customisable, cost effective flow reactors and equipment to be fabricated on relatively inexpensive benchtop scale printers. X-ray microcomputed tomography was utilised to non-invasively image and verify the internal structure of the prints to ensure fidelity in reactor fabrication. This non-invasive method of equipment validation shows potential in helping to demonstrate regulatory compliance for bespoke additively manufactured components, for example in continuous pharmaceutical manufacturing where the methods and printer used in this work should be sufficient to produce, (continuous) manufacturing scale equipment.

How to predict real time mechanisms of biofilm-particulate interactions?

The commercial use of nanoparticles has increased in recent years due to their unique characteristics, including high surface area, modifiable shape and surface charge and size-dependent properties. Consequently, a greater number of nanomaterials are now being released into the environment and inevitably interact with the natural ecosystem. Bacterial biofilms have the potential to capture and retain nanoparticles, however the factors determining the specific nanoparticle entrapment efficiencies of biofilms are not yet fully understood. Based on fluorescent intensity measurements we developed a simple and straightforward method that allowed the entrapment of different silica nanoparticles by two Pseudomonas strains to be quantified. It was determined that, regardless of nanoparticle size or surface functionalisation, Pseudomonas putida biofilms showed enhanced entrapment efficiencies compared to Pseudomonas fluorescens biofilms. It was also noted that both biofilms showed a higher entrapment capacity towards positively charged NPs. The method developed has the potential to be utilized for high throughput biofilm screening studies in order to develop a new understating of the relationship between nanoparticle characteristics and its uptake by bacterial biofilms.

Conventional wastewater treatment plants consume significant amounts of electricity. The constant aeration of the wastewater in order to foster the growth of microorganisms or the pumping of wastewater are two examples for energy-intensive processes within a plant. Case studies have shown that switching off blowers and inlet pumps for a certain period of time is possible without a loss in water quality. This yields a potential for wastewater treatment plants to provide demand response (DR) to the power system and thereby increase overall system flexibility. So far, the DR potential has only been quantified for individual plants, while the effects of large-scale DR provision by the wastewater treatment sector for the power system have not yet been studied. One reason for this is the lack of optimisation models which include both the wastewater treatment process and the power system operation in sufficient detail. Our model tackles this gap in the literature by providing a reduced-order linear biochemical model for the activated sludge process within a WWTP that can be incorporated into an operational energy system model. The results show that the effluent concentrations are predicted well by the linear reduced-order model in comparison to the results of the Standard Activated-Sludge model No. 1 (ASM1). Potential model applications are the variation of the airflow rate within a certain range and the variation of liquid influent flow rate to the system, which is a result of electricity load shedding of the inlet pumps and the blowers connected to the activated sludge tank.

The modelling and optimization of a process for the production of the medium chain length polyhydroxyalkanoate (mcl-PHA) by the bacterium Pseudomonas putida KT2440 when fed a synthetic fatty acid mixture (SFAM) was investigated. Four novel feeding strategies were developed and tested using a constructed model and the optimum one implemented in further experiments. This strategy yielded a cell dry weight of 70.6 g l−1 in 25 h containing 38% PHA using SFAM at 5 l scale. A phosphate starvation strategy was implemented to improve PHA content, and this yielded 94.1 g l−1 in 25 h containing 56% PHA using SFAM at 5 l scale. The process was successfully operated at 20 l resulting in a cell dry weight of 91.2 g l−1 containing 65% PHA at the end of a 25-h incubation.

Many countries, especially those with a high energy demand but insufficient renewable resources are currently investigating the role that imported low carbon hydrogen may play in meeting future energy requirements and emission reduction targets. A future hydrogen economy is uncertain and predicated on reduced price of hydrogen delivered to customers. Current hydrogen production, steam reforming of natural gas or coal gasification, is co-located to its end-use as a chemical feedstock. Large-scale multi-source value chains of hydrogen needed to support its use for energy are still at concept phase. This research investigates the combination of technical and economic factors which will determine the viability and competitiveness of two competing large scale renewable hydrogen value chains via ammonia and liquid hydrogen. Using a techno-economic model, an evaluation of whether green hydrogen exports to Germany from countries with low-cost renewable electricity production, but high-costs of storage, distribution and transport will be economically competitive with domestic renewable hydrogen production is conducted. The model, developed in Python, calculates costs and energy losses for each step in the value chain. This includes production from an optimised combination of solar and/or wind generation capacity, optimised storage requirements, conversion to ammonia or liquid hydrogen, distribution, shipping, and reconversion. The model can easily be applied to any scenario by changing the inputs and was used to compare export from Chile, Namibia, and Morocco with production in Germany using a 1 GW electrolyser and 2030 cost scenario in each case.

The accurate ab initio modeling of prototypical and well-representative photoactive interfaces for candidate dye-sensitized solar cells (DSCs) is a perennial problem in physical chemistry. To this end, the use of ab initio density functional theory-based molecular dynamics (AIMD) has been studied here to investigate the effect the choice of functional has on a system mimicking the essential workings of a DSC: the energetic properties of a [bmim]+[NTf2]- room-temperature ionic liquid (RTIL) solvating an N719-sensitizing dye adsorbed onto an anatase-titania (101) surface were scrutinized. In so doing, we glean important insights into how using an RTIL as electrolytic hole acceptor alters and modulates the dynamical properties of the widely used N719 dye. A fully crossed study has been carried out comparing the Becke-Lee-Yang-Parr (BLYP) and Perdew-Burke-Ernzerhof (PBE) functionals, both unsolvated and solvated by the RTIL, both with and without Grimme D3 dispersion corrections. Also, vibrational spectra for the photoactive interface in the DSC configuration were calculated by means of Fourier-transforming atomic mass-weighted velocity autocorrelation functions. The ab initio vibrational spectra were compared to high-quality experimental data and against each other; the effects of various methodological choices on the vibrational spectra were also studied, with PBE generally performing best in producing spectra, which matched the experimental frequency modes typically expected.

The photoactivity of carbon-incorporated titanium dioxide (TiO2) has been widely reported. This study involves a novel approach to the incorporation of carbon into TiO2 through the use of microwave plasma processing. The process involved thermally treating printed TiO2 nanoparticle coatings in a microwave-induced argon-oxygen plasma containing low concentrations of methane. The resulting deposited carbon layer was characterized using XRD, XPS, Raman, UV–vis, ellipsometry, and optical profilometry. It was found that the methane gas was dissociated in the microwave plasma into its carbon species, which were then deposited as a nm-thick layer onto the TiO2 coatings, most likely in the form of graphite. The photovoltaic performances of both the TiO2 and the carbon-incorporated TiO2 were assessed through J-V and IPCE measurements of the N719-sensitized solar cells using the titania as their photoanodes. Up to a 72% improvement in the maximum power density (Pd-max) was observed for the carbon-incorporated TiO2 samples as compared to the TiO2, onto which no carbon was added. This improvement was found to be mainly associated with an increase in the short-circuit current density (Jsc), but independent from the open-circuit voltage (Voc), the filter factor (FF), and the level of dye adsorption. Possible contributory factors to the improved performance of the carbon-incorporated TiO2 were the enhanced electron conductivity and electron lifetime, both of which were elucidated through electrochemical impedance spectroscopy (EIS). When the surface layer was examined using XPS, the optimal carbon content on the TiO2 coating surface was found to be 8.4%, beyond which there was a reduction in the DSSC efficiency.

Hematite nanorod arrays were activated through proper control of annealing conditions. The 100-fold improvement in photocurrent was correlated with increased absorption and Sn doping from the tin oxide coated glass substrate. The low onset potential is attributed to a reduction in surface defects, while the morphology is credited for promoting tin diffusion and facilitating electron transport.

The amelioration of biofouling in industrial processing equipment is critical for performance and reliability. While conventional biocides are effective in biofouling control, they are potentially hazardous to the environment and in some cases corrosive to materials. Enzymatic approaches have been shown to be effective and can overcome the disadvantages of traditional biocides, however they are typically uneconomic for routine biofouling control. The aim of this study was to design a robust and reusable enzyme-functionalized nano-bead system having biofilm dispersion properties. This work describes the biochemical covalent functionalization of silica-based nanobeads (hereafter referred to as Si-NanoB) with Proteinase K (PK). Results showed that PK-functionalized Si-NanoB are effective in dispersing both protein-based model biofilms and structurally altering Pseudomonas fluorescens biofilms, with significant decreases in surface coverage and thickness of 30.1% and 38.85%, respectively, while increasing surface roughness by 19 % following 24 h treatments on bacterial biofilms. This study shows that enzyme-functionalized nanobeads may potentially be an environmentally friendly and cost effective alternative to pure enzyme and chemical treatments.

In this study the use of microwave plasma sintering of nickel oxide (NiOx) particles for use as p-type photoelectrode coatings in dye-sensitized solar cells (DSSCs) is investigated. NiOx was chosen as the photocathode for this application due to its stability, wide band gap and p-type nature. For high light conversion efficiency DSSCs require a mesoporous structure exhibiting a high surface area. This can be achieved by sintering particles of NiOx onto a conductive substrate. In this study the use of both 2.45 GHz microwave plasma and conventional furnace sintering were compared for the sintering of the NiOx particles. Coatings 1 to 2.5 μm thick were obtained from the sintered particles (mean particle size of 50 nm) on 3 mm thick fluorine-doped tin oxide (FTO) coated glass substrates. Both the furnace and microwave plasma sintering treatments were carried out at ~ 450 °C over a 5 minute period. Dye sensitization was carried out using Erythrosin B and the UV-vis absorption spectra of the NiOx coatings were compared. A 44% increase in the level of dye adsorption was obtained for the microwave plasma sintered samples as compared to that obtained through furnace treatments. While the photovoltaic performance of the DSSC fabricated using the microwave plasma treated NiOx coatings exhibited a tenfold increase in the conversion efficiency in comparison to the furnace treated samples. This enhanced performance was associated with the difference in the mesoporous structure of the sintered NiOx coatings.

The emergent realisation of Industry 4.0 principles across biomanufacturing, through recent endeavours, will markedly enhance the development and manufacture of modern therapeutics. Through implementation of digital process models, a greater understanding of the intricate relationship between product quality attributes and manufacturing process performance may be established. While contributing towards accelerated process development, representative process models enable advanced optimisation of process parameters, thus having a tangible impact on the assurance of product quality and manufacturing robustness. Hybrid approaches, which couple mechanistic interpretability with statistical data-fitting, are posed to broaden the value and utility of digital models. To augment the advancement in modelling techniques and high-throughput technology, there is a growing requirement for automated approaches towards data processing and model assembly. In this study, a novel strategy is proposed, which leverages saturation and sigmoidal relationships, along with an underlying material balance framework, for the automated assembly of hybrid dynamic models of cell growth. The proposed hybrid model is compared against an equivalent mechanistic model based on Monod expressions. While both models achieve a reasonable fit against experimental data, the hybrid model demonstrates superior predictive performance. Development of automated hybrid models, as demonstrated in this study, may greatly accelerate process digitalisation across biopharmaceutical manufacture.

The influence of permeate flux on bacterial adhesion to NF and RO membranes was examined using two model Pseudomonas species, namely Pseudomonas fluorescens and Pseudomonas putida. To better understand the initial biofouling profile during NF/RO processes, deposition experiments were conducted in cross flow under permeate flux varying from 0.5 up to 120 L/(h m2), using six NF and RO membranes each having different surface properties. All experiments were performed at a Reynolds number of 579. Complementary adhesion experiments were performed using Pseudomonas cells grown to early-, mid- and late-exponential growth phases to evaluate the effect of bacterial cell surface properties during cell adhesion under permeate flux conditions. Results from this study show that initial bacterial adhesion is strongly dependent on the permeate flux conditions, where increased adhesion was obtained with increased permeate flux, until a maximum of 40% coverage was reached. Membrane surface properties or bacterial growth stages was further found to have little impact on bacterial adhesion to NF and RO membrane surfaces under the conditions tested. These results emphasise the importance of conducting adhesion and biofouling experiments under realistic permeate flux conditions, and raises questions about the efficacy of the methods for the evaluation of antifouling membranes in which bacterial adhesion is commonly assessed under zero-flux or low flux conditions, unrepresentative of full-scale NF/RO processes.

The electronic properties and photocatalytic activity of X (N, C) / transition metal (TM=Ta, Hf, Fe) – codoped anatase TiO2 have been investigated using density functional theory. It was found that only the (N, Ta)-codoping case narrows the band gap significantly by about 0.48 eV, driven by the continuum-like p-d hybridized states above the top of valence band and d states at the bottom of conduction band. The calculated energy results suggest that codoping of Ta with N can increase the N concentration in N-doped TiO2 based on energy results.

Combined leachate treatment at municipal wastewater treatment plants (WWTPs) is applicable to a certain extent depending on the leachate composition, treatment plant configuration and its capacity. Co-treatment of leachate at WWTPs has several advantages, but due to increasingly stringent discharge standards applied in WWTPs, it has become more problematic. This study was undertaken to investigate the impact of leachate feeding strategies on effluent quality and the aeration energy costs of WWTPs. A modified version of Benchmark Simulation Model No.1 was used to develop, test and compare several leachate feeding and WWTP control strategies in the context of dynamic pollutant loads and energy prices. The results highlighted that combined leachate treatment led to a deterioration in the quality of discharged wastewater, as indicated by a 12–20% increase in effluent quality index. Additionally, it adversely affected aeration energy demand and cost of the plant by increasing them 1.7–2.3% and 0.8–2.5%, respectively. The impacts could be mitigated by adjusting leachate flow based on effluent ammonium concentrations and by using advanced process control, i.e. feedback ammonium control for dissolved oxygen regulation in aerobic reactors. The study demonstrates that modeling can be used as a valuable tool to assess the potential impacts of leachate co-treatment and develop better management strategies.

Genetic diseases are caused by absent or defective genes. Gene therapy aims to treat these conditions by delivering a functional copy of the affected gene into a patient’s cells. Gene delivery can be performed by recombinant viruses, such as Adeno-Associated Virus (AAV). AAVs are favoured due to their safety, low pathogenicity and their ability to infect multiple tissue types. Currently three AAV-based therapies are approved for the treatment of genetic diseases. Genetic defects are usually present in every cell in a patient’s body. Therefore, gene therapy AAVs must be delivered to the majority of cells in an organ to achieve a therapeutic effect. As a result, AAV-based treatments require the administration of very high amounts of virus. Producing sufficient AAV, at an acceptable cost, without compromising safety is a major challenge in bio-production. Increasing or refining AAV production would enable the treatment of a wide variety of genetic diseases. Optimization strategies have focused on the genetic components needed for AAV assembly, the production cell lines, as well as omics-based approaches.

The effect of liquid flow velocity on biofilm development in a membrane-aerated biofilm reactor was investigated both by mathematical modeling and by experiment, using Vibrio natriegens as a test organism and acetate as carbon substrate. It was shown that velocity influenced mass transfer in the diffusion boundary layer, the biomass detachment rate from the biofilm, and the maximum biofilm thickness attained. Values of the overall mass transfer coefficient of a tracer through the diffusion boundary layer, the biofilm, and the membrane were shown to be identical during different experiments at the maximum biofilm thickness. Comparison of the results with published values of this parameter in membrane attached biofilms showed a similar trend. Therefore, it was postulated that this result might indicate the mechanism that determines the maximum biofilm thickness in membrane attached biofilms. In a series of experiments, where conditions were set so that the active layer of the membrane attached biofilm was located close to the membrane biofilm interface, it was shown that the most critical effect on process performance was the effect of velocity on biofilm structure. Biofilm thickness and effective diffusivity influenced reaction and diffusion in a complex manner such that the yield of biomass on acetate was highly variable. Consideration of endogenous respiration in the mathematical model was validated by direct experimental measurements of yield coefficients. Good agreement between experimental measurements of acetate and oxygen uptake rates and their prediction by the mathematical model was achieved.

It is now generally accepted that biofouling is inevitable in pressure-driven membrane processes for water purification. A large number of published articles describe the development of novel membranes in an effort to address biofouling in such systems. It is reasonable to assume that such membranes, even those with antimicrobial properties, when applied in industrial-scale systems will experience some degree of biofouling. In such a scenario, an understanding of the fate of planktonic cells, such as those entering with the feed water, has important implications with respect to contact killing particularly for membranes with antimicrobial properties. This study thus sought to investigate the fate of planktonic cells in a model nanofiltration biofouling system. Here, the interaction between auto-fluorescent Pseudomonas putida planktonic cells and 7-day-old Pseudomonas fluorescens resident biofilms was studied under permeate flux conditions in a nanofiltration cross flow system. We demonstrate that biofilm cell recruitment during nanofiltration is affected by distinctive biofilm structural parameters such as biofilm depth.

Recent studies have shown that insect wings have evolved to have micro- and nanoscale structures on the wing surface, and biomimetic research aims to transfer such structures to applicationspecific materials. Herein, we describe a simple and cost-effective method of replica molding the wing topographies of four cicada species using UV-curable polymers. Different polymer blends of polyethylene glycol diacrylate and polypropylene glycol diacrylate were used as molding materials and a molding chamber was designed to precisely control the x, y, and z dimensions. Analysis by scanning electron microscopy showed that structures ranged from 148 to 854 nm in diameter, with a height range of 191-2368 nm, and wing patterns were transferred with high fidelity to the crosslinked polymer. Finally, bacterial cell studies show that the wing replicas possess the same antibacterial effect as the cicada wing from which they were molded. Overall, this work shows a quick and simple method for patterning UV-curable polymers without the use of expensive equipment, making it a highly accessible means of producing microstructured materials with biological properties.

C3-Symmetric triaminoguanidinium chloride is condensed with N-pentylphenothiazine carboxaldehyde to realise a thermally stable twisted organic salt on a gram scale. It appears as a nonmetallic economic salt having an integrated propeller shape with three tub-like cores and displays efficient reversible mechano- and thermo-fluorochromic behaviour. Unlike previous reports, the designed fluorescent, colorimetric thermometer works over a higher temperature range of 130-170 °C with five distinct colour variations.