Depth Filtration Research Articles

Analysis of fouling and breakthrough of process related impurities during depth filtration using confocal microscopy.

Titer improvement has driven process intensification in mAb manufacture. However, this has come with the drawback of high cell densities and associated process related impurities such as cell debris, host cell protein (HCP), and DNA. This affects the capacity of depth filters and can lead to carryover of impurities to protein A chromatography leading to early resin fouling. New depth filter materials provide the opportunity to remove more process related impurities at this early stage in the process. Hence, there is a need to understand the mechanism of impurity removal within these filters. In this work, the secondary depth filter Millistak+ X0HC (cellulose and diatomaceous earth) is compared with the X0SP (synthetic), by examining the breakthrough of DNA and HCP. Additionally, a novel method was developed to image the location of key impurities within the depth filter structure under a confocal microscope. Flux, tested at 75, 100, and 250 LMH was found to affect the maximal throughput based on the max pressure of 30 psi, but no significant changes were seen in the HCP and DNA breakthrough. However, a drop in cell culture viability, from 87% to 37%, lead to the DNA breakthrough at 10% decreasing from 81 to 55 L/m2 for X0HC and from 105 to 47 L/m2 for X0SP. The HCP breakthrough was not affected by cell culture viability or filter type. The X0SP filter has a 30%–50% higher max throughput depending on viability, which can be explained by the confocal imaging where the debris and DNA are distributed differently in the layers of the filter pods, with more of the second tighter layer being utilized in the X0SP.

Mode and dosage time in polyethylene glycol precipitation process influences protein precipitate size and filterability

Precipitation has gained interest as alternative to the costly protein A chromatography for monoclonal antibody purification. Traditional precipitation processes are based on direct addition of precipitant in a single dose, with limited control on co-precipitation of impurities and not considering batch-to-batch variations. We propose a gradual dosage of polyethylene glycol to prevent co-precipitation and control resulting floc size. We used focused beam reflectance measurement to demonstrate that the PEG6000 dosage time and the final concentration significantly changes the particle size distribution (PSD). We demonstrated that gradual and stepwise precipitant addition was superior to conventional batch PEG precipitation, improving product yield and purity by a factor of 4 for HCP removal, for samples pre-treated with CaCl2 and caprylic acid. We studied the 3D structure of the precipitates by fractal dimension and showed that precipitates exhibited different compactness and density depending on the dosage time, resulting in different filterability in tangential flow filtration and depth filtration. To switch from batch to continuous PEG addition, the 3D structure of precipitates needs to be considered due to its high impact on the resulting process performance. Focused beam reflectance measurement (FBRM) and fractal dimension can be used to adjust the precipitation methodology to improve the product quality attributes and inform about the design of further purification steps.

RGBD salient object detection based on depth feature enhancement

The depth map contains spatial location information, which has been proven to be beneficial for RGBD salient object detection. However, the quality of the depth map will directly affect the accuracy of RGBD saliency detection. In order to solve the problem of different quality of depth maps, a detection model based on depth enhancement is designed to enhance the available depth information and filter low-quality depth maps. By comparing four evaluation indicators with five advanced models, the experimental results show that the model in this paper is advanced.

Dynamic SLAM of binocular catadioptric panoramic camera based on inverse depth filter

Dynamic SLAM of binocular catadioptric panoramic camera based on inverse depth filter

Proceedings of the 2019 Viral Clearance Symposium, Session 2: New Modalities in Chromatography and Adsorptive Filters.

In Session 2 of the 2019 Viral Clearance Symposium, new outcomes of viral clearance performance of polishing chromatography and depth filters utilized in the purification processes of biotechnologically produced recombinant proteins such as monoclonal antibodies were presented. It was shown that flow through both multimodal anion-exchange and anion-exchange chromatography are effective tools for removal of retroviruses and, under defined conditions, also for parvoviruses. Cation-exchange chromatography, when operated in bind/elute mode, hydrophobic interaction chromatography, and depth filtration can also be potent for virus removal, but are less robust for parvoviruses. Despite these data provide further understanding of virus removal mechanisms by chromatography and depth filtration operations, more investigation is required for a clear understanding of the molecular mechanisms of virus removal and the relevance of different moleculés interactions including resin, virus, and product.

Proceedings of the 2019 Viral Clearance Symposium, Session 8. Conference Summary: Key Discussion and Outcomes, Pending Questions, and Proposed Experiments and Actions.

This report provides a high-level summary of the key outcomes and gaps based on the research presented at the 2019 Viral Clearance Symposium and identifies new areas for future study and improvements. The 2019 conference structure extended the framework from the preceding conferences, focusing on the key gaps and associated developments and including the additional focus areas of facility risk mitigation, modular viral clearance claims, depth filter viral clearance, retrospective analysis of viral clearance and continuous processing, quantitation and analysis of viral clearance, viral inactivation by detergents and low pH, viral filtration mechanisms, viral filtration of media, viral detection by next-generation sequencing, and ways to improve the efficiency of the overall adventitious agent strategy.

Clarification of yeast cell suspensions by a highly porous polyamide nanofiber sponge

Depth filtration is an attractive method for initial clarification of broth for removing cells and cell debris. Electrospun nanofibers with their large specific surface area and a porous structure are known as attractive materials in filtration processes. However, dead-end filtration of cells through nanofiber mats (NFM) always leads to cake formation and increasing resistance. In this study, for the first time, a nanofiber sponge (NFS) or nanofiber aerogel was synthetized from polyamide 6 (PA6) building blocks. The NFS was flexible, highly porous and mechanically stable. The pore size of the NFS was tuned between 8 and 26 µm during the cryogenic processing step. Volumetric flux and filtration efficiency of the NFS depended on the pore size and the results were compared with those for NFM from the same PA6 nanofiber material. Dead-end filtration of Saccharomyces cerevisiae was feasible at a low differential pressure of 3.5 kPa and cell filtration efficiency was > 99 %. Modelling of the filtration process revealed that cake formation is prevented by NFS filters since cells are able to penetrate into the filter and to adsorb on their internal surface. The filtration characteristics were also compared with commercial depth filters and revealed the high flux of NFS filters along with the possibility to avoid filter aids and a low environmental impact. PA6-NFS filters may become a new and cost effective generation of filters for removing different cells or cell debris from broth and other applications.

Sulfide-bound copper removal from red and white wine using membrane and depth filters: Impacts of oxygen, H2S-to-Cu ratios, diatomaceous earth and wine volume

Sulfide-bound Cu in wine is a potential contributor to the reductive development of wine. This study examines the effectiveness of filtration for the adsorptive removal of this Cu fraction. The copper concentration in wine before and after filtration was determined by atomic spectroscopy (total) and by stripping potentiometry and/or adsorptive methodologies (Cu fractions). Membrane filters (4.7 cm2) removed significant amounts of sulfide-bound Cu from 10 mL of wine, including 60–80 % removal using nylon membranes, but they could not efficiently remove Cu from larger volumes. Dissolved oxygen concentration in the wine immediately prior to membrane filtration did not impact Cu removal, while a high sulfide-to-Cu(II) ratio did enhance removal. Depth filters incorporating diatomaceous earth with cellulose (45 mm-diameter, 3.5 mm-thickness) showed the most efficient removal of sulfide-bound Cu from wines even after treatment of 3.0 L. The relevance of these laboratory scale filtrations to winery scale filtration is discussed.

Depth filtration application of nanofibrillated cellulose-mesoporous silica nanoparticle composites as double-layer membranes

The adsorption capacity of cellulose membranes without modification is negligible for water treatment. Therefore, enhancing cellulose adsorption capacity via cost-effective approaches is required. Double-layer membranes with a nanofibrillated cellulose (NFC) membrane and an in-situ produced NFC-mesoporous silica nanoparticles (MSN) depth filter layers were produced. The membranes were tailored to improve size rejection and saturated adsorption capacity (SAC) by altering the gram per meter square (gsm) of the depth filter layer. The higher SAC of double-layer membranes was achieved by increasing the depth filter layer gsm and because of the significantly lower porosity of double-layer membranes compared to NFC-MSN single-layer membranes. The optimized membrane for methylene blue (MB) showed the SAC of 107 mg per g of MSN. The membrane could be modified with polyethyleneimine (PEI) or polyamide amine-epichlorohydrin (PAE) resin as cationic charged polyelectrolytes for the selective adsorption of anionic molecules of metanil yellow (MY). The membrane modified with PEI had 41 times higher SAC than unmodified specimens toward MY. Optimized double-layer membranes for size rejection, including 30 gsm composite layer, were produced by reducing the NFC fibre diameter via higher homogenization and drying the NFC layer before adding the depth filter layer. The optimized double-layer membrane had a polyethylene glycol (PEG) molecular weight cut-off (MWCO) of 200 kDa. These membranes manufactured by cost-effective materials have great potential of scale-up for membrane manufacturing for water treatment. The combination of good adsorption and size rejection makes a unique material that should be explored further.

Investigating the Influence of Column Depth on the Treatment of Textile Wastewater Using Natural Zeolite.

Textile industry production processes generate one of the most highly polluted wastewaters in the world. Unfortunately, the field is also challenged by the availability of relatively cheap and highly effective technologies for wastewater purification. The application of natural zeolite as a depth filter offers an alternative and potential approach for textile wastewater treatment. The performance of a depth filter treatment system can be deeply affected by the column depth and the characteristics of the wastewater to be treated. Regrettably, the information on the potential of these filter materials for the purification of textile wastewater is still scarce. Therefore, this study investigated the potential applicability of natural zeolite in terms of column depth for the treatment of textile wastewater. From the analysis results, it was observed that the filtration efficiencies were relatively low (6.1 to 13.7%) for some parameters such as total dissolved solids, electrical conductivity, chemical oxygen demand, and sodium chloride when the wastewater samples were subjected to the 0.5 m column depth. Relatively high efficiency of 82 and 93.8% was observed from color and total suspended solids, respectively, when the wastewater samples were subjected to the 0.5 m column depth. Generally, the 0.75 m column depth achieved removal efficiencies ranging from 52.3% to 97.5%, whereas the 1 m column depth achieved removal efficiencies ranging from 86.9% to 99.4%. The highest removal efficiency was achieved with a combination of total suspended solids and 1 m column depth (99.4%). In summary, the treatment approach was observed to be highly effective for the removal of total suspended solids, with a 93.8% removal efficiency when the wastewater was subjected to the 0.5 m column depth, 97.5% for 0.75 m column depth, and 99.4% for 1 m column depth. Moreover, up to 218.233 mg of color per g of the filter material was captured. The results derived in this study provide useful information towards the potential applicability of natural zeolite in the textile wastewater treatment field.

Colored Point Cloud Registration by Depth Filtering.

In the last stage of colored point cloud registration, depth measurement errors hinder the achievement of accurate and visually plausible alignments. Recently, an algorithm has been proposed to extend the Iterative Closest Point (ICP) algorithm to refine the measured depth values instead of the pose between point clouds. However, the algorithm suffers from numerical instability, so a postprocessing step is needed to restrict erroneous output depth values. In this paper, we present a new algorithm with improved numerical stability. Unlike the previous algorithm heavily relying on point-to-plane distances, our algorithm constructs a cost function based on an adaptive combination of two different projected distances to prevent numerical instability. We address the problem of registering a source point cloud to the union of the source and reference point clouds. This extension allows all source points to be processed in a unified filtering framework, irrespective of the existence of their corresponding points in the reference point cloud. The extension also improves the numerical stability of using the point-to-plane distances. The experiments show that the proposed algorithm improves the registration accuracy and provides high-quality alignments of colored point clouds.

Architecture Design and VLSI Implementation of 3D Hand Gesture Recognition System.

With advancements in technology, more and more research is being focused on enhancing daily life quality and convenience. Along with the increase in the development of gesture control systems, many controllers, such as the keyboard, mouse, and other devices, have been replaced with remote control products, which are gradually becoming more intuitive for users. However, vision-based hand gesture recognition systems still have many problems to overcome. Most hand detection methods adopt a skin filter or motion filter for pre-processing. However, in a noisy environment, it is not easy to correctly extract interesting objects. In this paper, a VLSI design with dual-cameras has been proposed to construct a depth map with a stereo matching algorithm and recognize hand gestures. The proposed system adopts an adaptive depth filter to separate interesting foreground objects from the background. We also propose dynamic gesture recognition using depth and coordinate information. The system can perform static and dynamic gesture recognition. The ASIC design is implemented in TSMC 90 nm with about 47.3 K gate counts, and 27.8 mW of power consumption. The average accuracy of each gesture recognition is 83.98%.

Expression of Biofilm-Degrading Enzymes in Plants and Automated High-Throughput Activity Screening Using Experimental Bacillus subtilis Biofilms.

Biofilm-forming bacteria are sources of infections because they are often resistant to antibiotics and chemical removal. Recombinant biofilm-degrading enzymes have the potential to remove biofilms gently, but they can be toxic toward microbial hosts and are therefore difficult to produce in bacteria. Here, we investigated Nicotiana species for the production of such enzymes using the dispersin B-like enzyme Lysobacter gummosus glyco 2 (Lg2) as a model. We first optimized transient Lg2 expression in plant cell packs using different subcellular targeting methods. We found that expression levels were transferable to differentiated plants, facilitating the scale-up of production. Our process yielded 20 mg kg−1 Lg2 in extracts but 0.3 mg kg−1 after purification, limited by losses during depth filtration. Next, we established an experimental biofilm assay to screen enzymes for degrading activity using different Bacillus subtilis strains. We then tested complex and chemically defined growth media for reproducible biofilm formation before converting the assay to an automated high-throughput screening format. Finally, we quantified the biofilm-degrading activity of Lg2 in comparison with commercial enzymes against our experimental biofilms, indicating that crude extracts can be screened directly. This ability will allow us to combine high-throughput expression in plant cell packs with automated activity screening.

Filter depth of complexes

Let be two ideals of a commutative noetherian ring R. The concept of a -filter depth of on an arbitrary R-complex M, is introduced and several characterizations via Koszul complexes and local cohomology are given. Some bounds of for an R-complex such that are provided, in special cases, recover and generalize the known results about the usual (filter-) depth of modules.

Disproportionate filtration behaviors of polymer/chromium gel used for fracture plugging

Polymer/chromium gel is commonly used for fracture plugging in naturally or hydraulic fractured formation. At present study, the filtration behavior of polymer gelant in fracture was investigated. According to the results of gelant analysis, the filtration degree of Cr3+ is obviously higher than that of polymer molecules, which verifies the disproportionate filtration behaviors of gel components. Polymer has great impact on the filtration behavior of Cr3+. Because of the thickening, entrapping and cross-linking effects, the filtration degree of Cr3+ can be greatly decreased by polymer molecules. Moreover, the adsorption layer of polymer molecules on fracture wall, the accumulation layer near the adsorption layer, and the retention layer in the matrix can also significantly hinder the filtration of Cr3+ from fracture into matrix. Results of fractured core flowing experiments show that both the filtration depth of gelant and the filtration degree of Cr3+ from fracture into matrix are reduced with the increase of polymer concentration. In addition, high injection pressure differential contributes to high filtration degree of Cr3+, which further results in the intense disproportionate filtration of gel components. What’s more, with the fracture width increasing and matrix permeability decreasing, the filtration degree of Cr3+ is greatly declined. Research results can provide theoretical reference for improving the water plugging performance of polymer gel in hydraulic fractured formation.

Parameters for effective sand filtration of Schistosoma mansoni cercariae from water

Abstract Schistosomiasis is a water-based neglected tropical disease that is prevalent in over 78 countries. It affects communities that are reliant on freshwater bodies contaminated with Schistosome cercariae for their daily water activities. Whilst treatment with the drug praziquantel is relatively effective, it does not prevent reinfection. One option for reducing schistosomiasis infection is providing at-risk communities with treated water, thereby reducing contact with cercaria-infested water for activities such as bathing or doing laundry. This study aims to establish design guidance for sand filtration to remove schistosome cercariae from water. Four sand filters were tested, varying from 300 to 2000 μm in sand grain size. Each filter was tested with a sand depth of 20 cm, which was increased until no cercariae were detected in the effluent. The required filter depth to remove 100% of cercariae ranged between 40 and 70 cm depending on sand grain size. Cercaria removal was more effective in filters with smaller sand grain size and larger filter depth. These results are valid for intermittent flow, for up to six cycle flushes. While more rigorous testing is needed, these initial results suggest that sand filters can be an effective way to treat cercaria-contaminated water in low-income settings.

A critical review on cleanroom filtration

Purpose Cleanrooms are highly controlled enclosed rooms where air quality is monitored and ensured to have less contamination according to standard cleanliness level. Air filters are used to optimize indoor air quality and remove air pollutants. Filter media and filtering system are decided as per requirement. Depth filter media are mostly used in cleanroom filtrations. This paper aims to present a comprehensive review of the evolution of cleanroom filter media. It evaluates the advantages and disadvantages of air filter media. It is also studied which air filters have additional properties such as anti-microbial properties, anti-odour properties and chemical absorbent. Development and innovation of air filters and filtration techniques are necessary to improve the performance via the synergistic effect and it can be a possible avenue of future research. Design/methodology/approach This paper aims to drive the future of air filter research and development in achieving high-performance filtration with high filtration efficiency, low operational cost and high durability. Air pollutants are classified into three types: suspended particles, volatile organic pollutants and microorganisms. Technologies involved in purification are filtration, water washing purification, electrostatic precipitation and anion technology. They purify the air by running it through a filter medium that traps dust, hair, pet fur and debris. As air passes through the filter media, they function as a sieve, capturing particles. The fibres in the filter medium provide a winding path for airflow. There are different types of air filters such as the high-efficiency particulate air filter, fibreglass air filter and ultra-low particulate air filter. Findings Emerging filtration technologies and filters such as nanofibres, filters with polytetrafluoroethylene membrane are likely to become prevalent over the coming years globally. The introduction of indoor air filtration with thermal comfort can be a possible avenue of future research along with expanding indoor environment monitoring and improving air quality predictions. New air filters and filtration technologies having better performance with low cost and high durability must be developed which can restrict multiple types of pollutants at the same time. Originality/value The systematic literature review approach used in this paper highlights the emerging trends and issues in cleanroom filtration in a structured and thematic manner, enabling future work to progress as it will continue to develop and evolve.

Photonic contact thermometry using silicon ring resonators and tuneable laser-based spectroscopy

Abstract Photonic sensors offer the possibility of purely optical measurement in contact thermometry. In this work, silicon-based ring resonators were used for this purpose. These can be manufactured with a high degree of reproducibility and uniformity due to the established semiconductor manufacturing process. For the precise characterisation of these photonic sensors, a measurement setup was developed which allows laser-based spectroscopy around 1550 nm and stable temperature control from 5 °C to 95 °C. This was characterised in detail and the resulting uncertainty influences of both the measuring set-up and the data processing were quantified. The determined temperature stability at 20 °C is better than 0.51 mK for the typical acquisition time of 10 s for a 100 nm spectrum. For a measurement of >24 h at 30 °C a standard deviation of 2.6 mK could be achieved. A hydrogen cyanide reference gas cell was used for traceable in-situ correction of the wavelength. The determined correction function has a typical uncertainty of 0.6 pm. The resonance peaks of the ring resonators showed a high optical quality of 157 000 in the average with a filter depth of up to 20 dB in the wavelength range from 1525 nm to 1565 nm. When comparing different methods for the determination of the central wavelength of the resonance peaks, an uncertainty of 0.3 pm could be identified. A temperature-dependent shift of the resonance peaks of approx. 72 pm/K was determined. This temperature sensitivity leads together with the analysed uncertainty contributions to a repeatability of better than 10 mK in the analysed temperature range from 10 °C to 90 °C.

Development of a novel motion capture and gait analysis system for rat locomotion

This paper proposes a marker-based motion capture system for rat motion detection and gait analysis. Motion capture in small animals such as rodents is more challenging than in humans because of their small bodies and rapid motion. Existing algorithms have poor applicability in rat motion capture in environments outside the studio. Moreover, gait analysis targeting on the rat is not performed by existing motion capture software. Our method consists of four procedures. First, Region of Interest (ROI) is extracted from the background using the inter-frame difference method and a depth filter. Second, a double-threshold marker detection method is used to detect markers in ROI and a marker shape filter is used to classify the markers. Third, a marker corrector is designed to modify missing and incorrect markers. Finally, a deep learning network is used to analyse the gait trajectory to classify rat as healthy, injured, or rehabilitated. The experimental result shows that marker recognition accuracy is 99.33%, higher than that of most existing software. The validation accuracy of the network is 100% and the loss is 0.0001. This method is conductive to the development of motion capture systems for small animals and research into the gait kinematics of rodents.

Feed Pump Pressure Control System Against Water Turbidity In Depth Filtration Process

This research discusses the feed pump pressure regulation system on water turbidity in the Depth Filtration process. The water purification system applies the depth filtration method by adjusting the speed of the feed pump based on the value of water turbidity. The sensors used are pressure transmitters which are used to measure the filter inlet and outlet pressures, as well as turbidity and conductivity sensors. To adjust the turbidity value of the water according to the clean water standard, the speed of the feed pump is controlled so that the water coming out of the filter outlet is in accordance with the clean water standard. In this system, PID control is applied using ciancone marlin tuning with PID parameters are Kc = 0.214779698, Ti = 0.39875, Td = 0.0625, with these parameters to reach the set point differential pressure requires an average rise time of 9.5 seconds, steady state 18.6 seconds, Settling time 11.8 seconds and over shoot = 2.55% and the value of water turbidity is 16.36 NTU.