Continuous Recirculation Research Articles

Water Heater Type, Temperature Setting, Operational Conditions, and Insulation Affect Ecological Niches for Legionella Growth.

Residential water heating represents an important nexus of energy/water conservation, waterborne disease, hygiene, and consumer preference. Here, we examine attributes of two off-the-shelf 151-L tank water heaters, one with hot water recirculation (recirculating) and another without recirculation (standard), compared to a tankless on-demand heater (on-demand). Energy efficiency decreased in the order on-demand > standard > continuous recirculation. However, the electric on-demand water heater repeatedly malfunctioned and could not consistently achieve target temperatures >48 °C. At a temperature setting of 48 °C, the volume of water in the pipe and tank within a temperature range at very high risk for Legionella growth (38-47 °C) decreased from recirculating (150 L) > standard (40 L) > on-demand (∼0.47 L). However, at a temperature setting of 66 °C, the standard tank was stratified, and the bottom 13 L fell within the very high-risk temperature range, whereas the recirculating tank system maintained 100% of its volume >55 °C, which is not suitable for Legionella growth. Addition of insulation was found to markedly increase the temperature throughout the tank. In the standard tank set at 66 °C with insulation, no volume was maintained within the very high-risk range. Insulation can holistically increase energy efficiency and reduce health risks at a sufficiently elevated temperature setting.

Improvement of biogas productivity from distillery wastewater by partial potassium reduction pretreatment using two-step microfiltration and nanofiltration

The main purpose of the current study was to employ filtration pretreatment to lower the K concentration in distillery wastewater (DW) from a very high level (8800 mg/L) close to severe inhibition (>12000 mg/L) to 4350 mg/L, which was in the moderate toxic range (2500–4500 mg/L) for methanogens. The filtration pretreatment system consisted of the two steps of microfiltration (MF) to remove large solid particles and nanofiltration (NF) to reduce K concentration in the retained DW. Both steps of MF and NF were operated in batch mode with continuous recirculation. The permeate of the MF step was fed to the NF unit in conjunction with different dilution ratios (dilution water volume-to-feed volume) to lower the K content in the retentate. The higher the cumulative dilution ratio, the lower the K concentration in the retentate of the NF step. However, it has to be traded off against the increasing total volume of permeate with the higher cumulative dilution ratio. Thus, at the optimum cumulative dilution ratio of 0.5:1, the DW from filtration pretreatment with a high COD value of 111500 mg/L and a low K content of 4350 mg/L was found to have significantly higher methanogenic productivities in terms of average production rate and yields of both biogas and methane with a higher optimum COD loading rate, as compared to those of the untreated DW. Moreover, the use of the two-step filtration in this investigation could significantly lower the dilution ratio as compared to the sole dilution method (0.5:1 against 2:1).

Utilization of a human Liver Tissue Chip for drug-metabolizing enzyme induction studies of perpetrator and victim drugs

Polypharmacy-related drug-drug interactions (DDIs) are a significant and growing healthcare concern. An increasing number of therapeutic drugs on the market underscores the necessity to accurately assess new drug combinations during preclinical evaluation for DDIs. In vitro primary human hepatocytes (PHH) models are only applicable for short-term induction studies because of their rapid loss of metabolic function. Though coculturing nonhuman stromal cells with PHH has been shown to stabilize metabolic activity long-term, there are concerns about human specificity for accurate clinical assessment. In this study, we demonstrated a PHH-only liver microphysiological system in the Liver Tissue Chip is capable of maintaining long-term functional and metabolic activity of PHH from 3 individual donors and thus a suitable platform for long-term DDI induction studies. The responses to rifampicin induction of 3 PHH donors were assessed using cytochrome P450 activity and mRNA changes. Additionally, victim pharmacokinetic studies were conducted with midazolam (high clearance) and alprazolam (low clearance) following perpetrator drug treatment, rifampicin-mediated induction, which resulted in a 2-fold and a 2.6-fold increase in midazolam and alprazolam intrinsic clearance values, respectively, compared with the untreated liver microphysiological system. We also investigated the induction effects of different dosing regimens of the perpetrator drug (rifampicin) on cytochrome P450 activity levels, showing minimal variation in the intrinsic clearance of the victim drug (midazolam). This study illustrates the utility of the Liver Tissue Chip for in vitro liver-specific DDI induction studies, providing a translational experimental system to predict clinical clearance values of both perpetrator and victim drugs. Significance StatementThis study demonstrated the utility of the Liver Tissue Chip with a primary human hepatocyte–only liver microphysiological system for drug-drug interaction induction studies. This unique in vitro system with continuous recirculation maintains long-term functionality and metabolic activity for up to 4 weeks, enabling the study of perpetrator and victim drug pharmacokinetics, quantification of drug-induced cytochrome P450 mRNA and activity levels, investigation of patient variability, and ultimately clinical predictions.

Construction and evaluation of electrophotocataltic tubular reactor in phenol degradation

Contamination of the environment is one of the main threats to achieving sustainability. Even though there have been significant legal efforts to regulate parameters for effluent disposal, conventional treatment methods often prove to be ineffective, resulting in the incomplete removal of pollutants. This inefficiency leads to serious environmental issues, such as the toxicity of biomes, which is closely related to the bioaccumulation of harmful substances. In response to this challenge, this study aimed to develop and optimize an electrophotocatalytic reactor for the remediation of a synthetic phenol solution using advanced oxidative processes (AOPs). By applying these processes, we observed that the characteristics of the reaction medium allowed for a maximum pollutant removal yield of 54.73% over a 3-hour operation period in a continuous recirculation regime. Despite the promising results, the study revealed the influence of additional factors that were not considered, which are likely important in further optimizing the reactor's efficiency for real-world applications.

Packing Incubation and Addition of Rot Fungi Extracts Improve BTEX Elimination from Air in Biotrickling Filters.

The removal of benzene, toluene, ethylbenzene, and xylene (BTEX) from air was investigated in two similar biotrickling filters (BTFs) packed with polyurethane (PU) foam, differing in terms of inoculation procedure (BTF A was packed with pre-incubated PU discs, and BTF B was inoculated via the continuous recirculation of a liquid inoculum). The effects of white rot fungi enzyme extract addition and system responses to variable VOC loading, liquid trickling patterns, and pH were studied. Positive effects of both packing incubation and enzyme addition on biotrickling filtration performance were identified. BFF A exhibited a shorter start-up period (approximately 20 days) and lower pressure drop (75 ± 6 mm H2O) than BTF B (30 days; 86 ± 5 mm H2O), indicating the superior effects of packing incubation over inoculum circulation during the biotrickling filter start-up. The novel approach of using white rot fungi extracts resulted in fast system recovery and enhanced process performance after the BTF acidification episode. Average BTEX elimination capacities of 28.8 ± 0.4 g/(m3 h) and 23.1 ± 0.4 g/(m3 h) were reached for BTF A and BTF B, respectively. This study presents new strategies for controlling and improving the abatement of BTEX in biotrickling filters.

Process Performance and Nutrient Removal in Fish Processing Wastewater Using a Membrane Bioreactor (MBR) Unit for Reuse for Irrigation

This study investigated the removal of nitrogen and phosphates in fish processing wastewater through process optimization of a membrane bioreactor (MBR) treatment unit. Raw process wastewater was collected from the Makindi fish farm and was pre-filtered through a mesh of 0.8 mm. The experiment was conducted at a lab scale using commercial Polyethersulfone (PES) membranes submerged in the MBR unit. The pre-filtered wastewater sample was added into a denitrification (anoxic) tank. The process was conducted through continuous recirculation between the aeration and the anoxic tank to enhance the removal of nitrogenous compounds. The recirculation flow rate was 10L/h. A hydraulic residence time (HRT) of approximately 22-25h was maintained, and the aeration rate in the aerobic tank was 100L/min. Aluminum sulphate AI2(SO4)318H2O was added continually into the anoxic tank and with constant stirring to enhance the removal of phosphates. A removal rate of 85±2% for NH4+-N, 84±1% for NO3- -N, and 69±3% for PO43--P was obtained. The nutrient concentration in the effluent was successfully reduced to an acceptable level with both nitrogenous compounds and phosphate concentrations obtained within the range of < 30 mg/L and ≤ 5 mg/L as per the WHO guidelines for wastewater reuse for irrigation. The results showed a successful process optimization that can be applied to ensure optimized performance of the MBR unit thus improve its effectiveness for the treatment of fish processing wastewater. The study therefore recommends process optimization as a tool for effective removal of nutrients in the MBR system thus making it a potential recycling approach for treatment of fish processing wastewater for reuse for irrigation purposes.

Solar powered electrocatalytic treatment of actual human urine coupled with hydrogen production using Ti/MMO for the removal of nitrogen-based compounds

This study addresses a significant micropollutant removal from actual human urine (AHU) through photovoltaic driven electrochemical treatment. This study showed significant reductions of 69.09 % urea, 67.95 % creatinine, and 95.180 % uric acid under optimal continuous recirculation conditions. Analysis revealed that the degradation of pollutants were facilitated by in-situ generation of reactive oxygen and chlorine species during treatment. Further, the procedure employed with molecular hydrogen generation during anodic oxidation as useful byproduct. Thus, the findings suggest that novel mixed metal oxide exhibits high efficacy for AHU treatment, offering a prominent concept for onsite treatment of complex mixed wastewater in real-life applications.

#3022 Rationale and design of the CORDIAL first-in-human clinical trial: a system for sorbent-assisted continuous flow peritoneal dialysis

Abstract Background and Aims Peritoneal dialysis has important disadvantages, including low plasma clearance and a limited technique survival. A new device for sorbent-assisted continuous flow peritoneal dialysis has been designed (Wearable Artificial KIDney, WEAKID) that is based on continuous recirculation (rapid cycling) of peritoneal dialysate via a single-lumen peritoneal catheter with regeneration of dialysate using sorbents. Anticipated benefits are a better plasma clearance a higher mass transfer area coefficient with continuous flow of dialysate and enhanced diffusion due to a higher time-averaged plasma-dialysate concentration gradient with sorbent-based dialysate regeneration, and a prolonged technique survival thanks to lower peritonitis risk (less (dis)connections) and a lower glucose exposure. Method This is a first-in-human, prospective, open-label, non-randomized, single-arm, multicenter study, that will be performed at the University Medical Center Utrecht (Utrecht, The Netherlands), Università degli studi di Modena e Reggio Emilia (Italy), and Instituto de Investigación Hospital Universitario La Paz, Servicio Madrileño de Salud (Spain). We aim to include 12 stable, adult PD patients. In the first week, blood, urine, and dialysate samples will be collected over three separate days to assess the efficacy of the patient's standard PD schedule. The WEAKID system will then be tested in a clinical setting on 6 days over a period of 2 weeks (three consecutive days per week). During the first week, participants will be treated with WEAKID without sorbents for 4h (first day) or 8h (second and third day). The second week, treatment will consist of WEAKID with sorbents for 4h (first day) or 8h (second and third day). This way, exposure to new components of the system is incremental and the effectiveness of continuous recirculation of dialysate and that the added effect of sorbent-based dialysate regeneration can be analyzed separately. Outcomes The primary aim of this first-in-human clinical trial is to evaluate the (short term) clinical safety and performance of WEAKID treatment in a clinical setting. The primary safety objective will be assessed by describing and examining the incidence of: Key secondary objectives include an evaluation of efficacy in terms of plasma clearance, ultrafiltration, net base release, and patient tolerance. Planning Inclusion of the first patient is expected in January 2024, the final inclusion is expected to take place in November 2024.

Continuous production and recirculation of plasma‐activated water bubbles under different flow regimes for mixed‐species bacterial biofilm inactivation inside pipelines

AbstractBiofilm formation in broiler drinking water systems is a public health concern. Bacterial detachment from the pipes into the drinking water subsequently increases the risk of waterborne transmission and has detrimental effects on animal and human health. The study evaluated the antimicrobial effectiveness of plasma‐activated water bubbles (PAWBs) recirculated under different flow regimes against the mixed‐species biofilms of Salmonella Typhimurium ATCC13311 and Aeromonas australiensis 03‐09 grown on the inner surfaces of polyvinyl chloride (PVC) pipes. A benchtop pipeline model representing broiler drinker lines was developed to compare the biofilm inactivation efficacy of PAWB recirculated at different flow rates, corresponding to Reynold's number of 1000, 2500, and 4000. The synergistic mechanical and oxidative recirculation using PAWB resulted in a higher biofilm inactivation from the pipe walls as compared to recirculation using distilled water alone. Apart from the flow regimes, various parameters including the volume of PAWB circulated, the concentration of the major plasma reactive species, and treatment time affected the susceptibility of the mixed‐species biofilms to PAWB treatment. Under all tested conditions, the bacterial cells were below the detection limit of 1 log CFU/mL in water after PAWB treatments. A better understanding of the hydrodynamic variations prevalent in the drinking water system is important for designing an effective disinfection protocol using PAWB. The results obtained from the study provide important information on the use of PAWB for biofilm control strategies.

Assessment of the development of Lactuca sativa Batavia Aficion in hydroponic and aquaponic systems

The need to improve the methods of growing plants in hydroponic systems to ensure optimal conditions for their growth and achieve high yields is urgent. The purpose of this study was to compare the hydroponic production of Lactuca sativa Batavia Aficion using a conventional Knop nutrient solution compared to aquaponics using nutrient-rich fish water. Laboratory, potentiometric, and photometric methods were used for this purpose. The yield, biometric, and qualitative indicators of lettuce leaves were investigated. Despite the lower nutrient concentration in the aquaponic solution, the nutritional status of Lactuca sativa Batavia Aficion was within the optimal range. The nitrate content of lettuce grown in the aquaponics system was higher than in hydroponics, but there were no significant differences in the content of total N (3.24% and 2.97%), Mg (1,973 mg/kg and 1,943 mg/kg), Fe (93.91 mg/kg and 93.83 mg/kg), K (73.7 mg/kg and 73.6 mg/kg), and Ca (19.5 mg/kg and 20.1 mg/kg). The yield of Lactuca sativa Batavia Aficion on aquaponics was 2.8 kg / m2 and 3.2 kg m2 – on hydroponics, with a density of 36 plants per square metre. Water monitoring in the aquaponic system showed low concentrations of nitrates, phosphorus (P), potassium (K), and magnesium (Mg), but the proportion of mineral nutrients and pH were stable throughout the lettuce growing period. Lettuce leaves in the aquaponics system reached a fresh weight of 80 g in 34 days, which is on average 13% less than lettuce leaves in the hydroponics system. The EC (electrical conductivity) values recorded in this study in a hydroponic system were between 1.2 and 1.5 cm/m. In the aquaponic system, EC has higher values due to the low rate of water replacement, contributing to greater growth and accumulation of solution ions. However, due to continuous recirculation in the water, the conditions become satisfactory for growing plants. The results obtained can contribute to the creation of more efficient and sustainable agricultural systems, reducing resource consumption and improving the resistance of cultivated crops to various stressful conditions

Enabling continuous immune cell recirculation on a microfluidic array to study immunotherapeutic interactions in a recapitulated tumour microenvironment.

The effects of immunotherapeutics on interactions between immune and cancer cells are modulated by multiple components in the tumour microenvironment (TME), including endothelium and tumour stroma, which provide both a physical barrier and immunosuppressive stimuli. Herein, we report a recirculating chip to enable continuous immune cell recirculation through a microfluidic cell array to include these crucial players. This system consists of a three-layered cell array (μFCA) spatially emulating the TME, with tailored fluidic circuits establishing T cell recirculation. This platform enables the study of dynamics among the TME, immune cells in a circulatory system and cancer cell responses thereof. Through this system, we found that tumour endothelium hindered T cell infiltration into the reconstructed breast cancer tumour compartment. This negative effect was alleviated when treated with anti-human PD-L1 (programmed cell death ligand 1) antibody. Another key stromal component - cancer associated fibroblasts - attenuated T cell infiltration, compared against normal fibroblasts, and led to reduced apoptotic activity in cancer cells. These results confirm the capability of our tumour-on-a-chip system in identifying some key axes to target in overcoming barriers to immunotherapy by recapitulating immune cell interactions with the reconstructed TME. Our results also attest to the feasibility of scaling up this system for high-throughput cancer immunotherapeutic screening.

A novel microfluidic tool for the evaluation of local drug delivery systems in simulated in vivo conditions.

A 3D-printed microfluidic tool for assessing local drug delivery systems (LDD) in simulated in vivo conditions was developed and evaluated. The device was designed considering the oral environment and dental applications, and it was fabricated with a high-precision resin 3D printer. Chitosan scaffolds loaded with different concentrations of doxycycline were used for evaluating our device. The concentration of the released drug was measured through in-line UV-VIS spectroscopy, and to verify the repeatability and accuracy of our measurements, comparisons with standard HPLC results were made (5% deviation). Cumulative drug release profiles in steady-state conditions were obtained and compared to the Weibull model. The behaviour of the LDD system in a dynamic environment was also evaluated during experiments where step changes in pH were introduced. It was demonstrated that under infection-like conditions, there is an immediate response from the polymer and a clear increase in the concentration of the released drug. Continuous flow and recirculation experiments were also conducted, revealing significant differences in the drug release profiles. Specifically, in the case of continuous flow, the quantity of the released drug is much higher due to the higher driving force for diffusion (concentration gradient). Overall, the proposed microfluidic tool proved to be ideal for evaluating LDD systems, as the in vivo microenvironment can be replicated in a better way than with currently used standard systems.

A Novel Milli-fluidic Liver Tissue Chip with Continuous Recirculation for Predictive Pharmacokinetics Applications

A crucial step in lead selection during drug development is accurate estimation and optimization of hepatic clearance using in vitro methods. However, current methods are limited by factors such as lack of physiological relevance, short culture/incubation times that are not consistent with drug exposure patterns in patients, use of drug absorbing materials, and evaporation during long-term incubation. To address these technological needs, we developed a novel milli-fluidic human liver tissue chip (LTC) that was designed with continuous media recirculation and optimized for hepatic cultures using human primary hepatocytes. Here, we characterized the LTC using a series of physiologically relevant metrics and test compounds to demonstrate that we could accurately predict the PK of both low- and high-clearance compounds. The non-biological characterization indicated that the cyclic olefin copolymer (COC)–based LTC exhibited negligible evaporation and minimal non-specific binding of drugs of varying ionic states and lipophilicity. Biologically, the LTC exhibited functional and polarized hepatic culture with sustained metabolic CYP activity for at least 15 days. This long-term culture was then used for drug clearance studies for low- and high-clearance compounds for at least 12 days, and clearance was estimated for a range of compounds with high in vitro-in vivo correlation (IVIVC). We also demonstrated that LTC can be induced by rifampicin, and the culture age had insignificant effect on depletion kinetic and predicted clearance value. Thus, we used advances in bioengineering to develop a novel purpose-built platform with high reproducibility and minimal variability to address unmet needs for PK applications.Graphical

Experimental investigation of residence time and axial velocity of 6.0 cm graphite pebbles in a cold-flow pebble bed reactor using radioisotope-based technique

Understanding pebble flow characteristics and residence time distribution is essential for reactor design, fuel burnup estimations, and safety analysis of High-Temperature Gas-Cooled Pebble Bed Reactors. However, due to the complex nature of the dense granular flow, pebble flow remains inadequately understood and challenging to study through experiments. In this work, a three-dimensional experimental pebble-bed setup was developed to investigate pebble flow behavior in pebble-bed reactors. For the first time, 6.0 cm graphite pebbles were utilized, and features such as one pebble at a time discharge mode and continuous pebble recirculation were incorporated. The overall and zonal residence time distributions and the zonal-averaged axial velocity were investigated using a radioisotope-based residence time distribution (RTD) technique. The results showed that the overall residence time increases as the radius of the initial seeding position increases, but with a higher increase rate at the wall compared to the center region. The zonal residence time findings indicated a uniform profile in the upper section of the bed, except near the wall. However, non-uniformity in the radial profile increased in the lower sections, with the greatest variation occurring in the conical section. The axial velocity of the pebbles was found to be small and nearly uniform in the upper section of the bed. In the lower section, however, the velocity increased significantly for the center-region pebbles compared to those at the wall, resulting in a pronounced non-uniform radial profile. Moreover, a consistent hexagonal arrangement of pebbles was observed across the entire container wall after recirculating several bed inventories, which is worth further investigation.

Blood component separation in straight microfluidic channels.

Separation of blood components is required in many diagnostic applications and blood processes. In laboratories, blood is usually fractionated by manual operation involving a bulk centrifugation equipment, which significantly increases logistic burden. Blood sample processing in the field and resource-limited settings cannot be readily implemented without the use of microfluidic technology. In this study, we developed a small footprint, rapid, and passive microfluidic channel device that relied on margination and inertial focusing effects for blood component separation. No blood dilution, lysis, or labeling step was needed as to preserve sample integrity. One main innovation of this work was the insertion of fluidic restrictors at outlet ports to divert the separation interface into designated outlet channels. Thus, separation efficiency was significantly improved in comparison to previous works. We demonstrated different operation modes ranging from platelet or plasma extraction from human whole blood to platelet concentration from platelet-rich plasma through the manipulation of outlet port fluidic resistance. Using straight microfluidic channels with a high aspect ratio rectangular cross section, we demonstrated 95.4% platelet purity extracted from human whole blood. In plasma extraction, 99.9% RBC removal rate was achieved. We also demonstrated 2.6× concentration of platelet-rich plasma solution to produce platelet concentrate. The extraction efficiency and throughput rate are scalable with continuous and clog-free recirculation operation, in contrast to other blood fractionation approaches using filtration membranes or affinity-based purification methods. Our microfluidic blood separation method is highly tunable and versatile, and easy to be integrated into multi-step blood processing and advanced sample preparation workflows.

Effect of recirculation and hydraulic loading rate on ammonium and phosphate recovery from fertilizer industry wastewater

This study aimed to determine the optimum recirculation ratio and hydraulic loading rate for the recovery process of ammonium and phosphate, and study the formation, morphology, and structure of struvite crystals. This study provides a crystallization method to treat fertilizer wastewater using a continuous system and recirculation, including a fluidized bed reactor (FBR). Ammonium and phosphate were recovered from fertilizer industry wastewater using a continuous FBR under different recirculation ratios (3, 6, and 9) and loading rates (0.39 L/min, 0.59 L/min, and 0.79 L/min). MgCl2 was used as the precipitant with a 1.5:1 molarity ratio [Mg2+]:[PO43−]. The results showed that 55.71% phosphate and 49.69% ammonium could be recovered at recirculation ratio and hydraulic loading rate were 9 and 0.39 L/min, respectively. Scanning electron microscopy-energy diffraction X-ray analysis showed that the formed crystals comprised 80% struvite. Further, a high recirculation ratio and low loading rate resulted in higher ammonium and phosphate recovery efficiencies. These results indicated that a long detention time of treated wastewater can increase the nutrient recovery.

Prediction and control of elevated temperatures within landfills under aeration and recirculation based on the thermal non-equilibrium model

Aeration is an effective approach to sustainable landfilling but may lead to elevated temperatures within landfills, resulting in landfill fires or explosions. Therefore, aeration is usually combined with leachate recirculation to control the elevated temperatures within landfills. To predict landfill temperatures during aeration and recirculation, a local thermal non-equilibrium model is developed considering the heat generation of biodegradation, the heat removal due to evaporation and leachate-gas flow, and the effects of the capillary. The solver is implemented in OpenFOAM based on the finite volume method and validated against a waste-column experiment and an in-situ aeration test. The simulation results demonstrate that the assumption of local thermal equilibrium will distinctly overestimate the temperature, maximally by 15 °C in the studied case. The model is then used to simulate a typical aerobic landfill unit to investigate the formation of explosive gas mixtures and elevated temperatures under different operating conditions. The simulation results of gas composition suggest that aeration will not result in explosive gas within landfills. A reasonable recirculation method for temperature control with corresponding operating parameters under a group of values of aeration pressure (2000–4000 Pa) and recirculation rate (0.0001–0.0008 m/s) are proposed, which can provide some guides for the design of an aeration and recirculation combined system. For a given total volume of added leachate, a higher recirculation rate does not always mean better cooling, and the cooling effect of continuous recirculation is better than that of intermittent recirculation.

Carbonic Anhydrase Enhanced UV-Crosslinked PEG-DA/PEO Extruded Hydrogel Flexible Filaments and Durable Grids for CO2 Capture.

In this study, poly (ethylene glycol) diacrylate/poly (ethylene oxide) (PEG-DA/PEO) interpenetrating polymer network hydrogels (IPNH) were extruded into 1D filaments and 2D grids. The suitability of this system for enzyme immobilization and CO2 capture application was validated. IPNH chemical composition was verified spectroscopically using FTIR. The extruded filament had an average tensile strength of 6.5 MPa and elongation at break of 80%. IPNH filament can be twisted and bent and therefore is suitable for further processing using conventional textile fabrication methods. Initial activity recovery of the entrapped carbonic anhydrase (CA) calculated from esterase activity, showed a decrease with an increase in enzyme dose, while activity retention of high enzyme dose samples was over 87% after 150 days of repeated washing and testing. IPNH 2D grids that were assembled into spiral roll structured packings exhibited increased CO2 capture efficiency with increasing enzyme dose. Long-term CO2 capture performance of the CA immobilized IPNH structured packing was tested in a continuous solvent recirculation experiment for 1032 h, where 52% of the initial CO2 capture performance and 34% of the enzyme contribution were retained. These results demonstrate the feasibility of using rapid UV-crosslinking to form enzyme-immobilized hydrogels by a geometrically-controllable extrusion process that uses analogous linear polymers for both viscosity enhancement and chain entanglement purposes, and achieves high activity retention and performance stability of the immobilized CA. Potential uses for this system extend to 3D printing inks and enzyme immobilization matrices for such diverse applications as biocatalytic reactors and biosensor fabrication.

SMART FARMING USING A SOLAR POWERED AQUAPONICS SYSTEM FOR A SUSTAINABLE FOOD PRODUCTION

This paper discusses the prospect of utilization of solar energy for aquaponics operation. Aquaponic is a platform for farmers to simultaneously grow fish and plants in a same unit. It is sustainable and produces little waste. The need of pumps for continuous water recirculation and air supply within the system could be a hindrance in the aquaponics operation especially if the unit is nowhere near any power outlet. It is indeed a visible solution as Malaysia located at equator and receives average sunlight ~9 hours a day throughout the year with solar intensity as high as 1800-1900 kWh/m2. The work presents detail equipment for establishment of suitable solar PV system for aquaponics operation and reviews utilities of aquaponics platform that can be supported using solar energy. Possible integration of Internet-of-Things (IoT) for remote monitoring of such solar operated aquaponics unit is also discussed. Analysis showed that even when operated with full energy supply for only 12 hours, the yield and growth rates of the crop and fish grown in the system powered remains unaffected. This signified the potential for the use of solar energy as alternative energy for operation of the aquaponics unit. The main advantage perhaps is the realization of aquaponics setup in remote area where electricity is not accessible. Installation cost may be relatively high (100W PV system could cost nearly RM 600 for installation) but for a long run, it is highly beneficial as utility cost and cost for installing the national grid can be significantly reduced. Summarizing, the project introduced the concept of smart farming via aquaponics for a sustainable production of crop and fish using a renewable and clean solar energy for its operation.

Mixotrophic chain elongation with syngas and lactate as electron donors.

Feeding microbial communities with both organic and inorganic substrates can improve sustainability and feasibility of chain elongation processes. Sustainably produced H2 , CO2 , and CO can be co-fed to microorganisms as a source for acetyl-CoA, while a small amount of an ATP-generating organic substrate helps overcome the kinetic hindrances associated with autotrophic carboxylate production. Here, we operated two semi-continuous bioreactor systems with continuous recirculation of H2 , CO2 , and CO while co-feeding an organic model feedstock (lactate and acetate) to understand how a mixotrophic community is shaped during carboxylate production. Contrary to the assumption that H2 , CO2 , and CO support chain elongation via ethanol production in open cultures, significant correlations (p < 0.01) indicated that relatives of Clostridium luticellarii and Eubacterium aggregans produced carboxylates (acetate to n-caproate) while consuming H2 , CO2 , CO, and lactate themselves. After 100 days, the enriched community was dominated by these two bacteria coexisting in cyclic dynamics shaped by the CO partial pressure. Homoacetogenesis was strongest when the acetate concentration was low (3.2g L-1 ), while heterotrophs had the following roles: Pseudoramibacter, Oscillibacter, and Colidextribacter contributed to n-caproate production and Clostridium tyrobutyricum and Acidipropionibacterium spp. grew opportunistically producing n-butyrate and propionate, respectively. The mixotrophic chain elongation community was more efficient in carboxylate production compared with the heterotrophic one and maintained average carbon fixation rates between 0.088 and 1.4g CO2 equivalents L-1 days-1 . The extra H2 and CO consumed routed 82% more electrons to carboxylates and 50% more electrons to carboxylates longer than acetate. This study shows for the first time long-term, stable production of short- and medium-chain carboxylates with a mixotrophic community.