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The paper presents a novel instrumental analytical endotoxin quantification assay. It uses common analytical laboratory equipment (HPLC-FLD) and allows quantifying endotoxins (ETs) in different matrices from about 109 EU per mL down to about 40 EU per mL (RSE based). Test results are obtained in concentration units (e.g. ng ET per mL), which can then be converted to commonly used endotoxin units (EU per mL) in case of known pyrogenic activity. During endotoxin hydrolysis, the endotoxin specific rare sugar acid KDO is obtained quantitatively. After that, KDO is stoichiometrically reacted with DMB, which results in a highly fluorescent derivative. The mixture is separated using RP-HPLC followed by KDO-DMB quantification with a fluorescence detector. Based on the KDO content, the endotoxin content in the sample is calculated. The developed assay is economic and has a small error. Its applicability was demonstrated in applied research. ETs were quantified in purified bacterial biopolymers, which were produced by Gram-negative bacteria. Results were compared to LAL results obtained for the same samples. A high correlation was found between the results of both methods. Further, the new assay was utilized with high success during the development of novel endotoxin specific depth filters, which allow efficient, economic and sustainable ET removal during DSP. Those examples demonstrate that the new assay has the potential to complement the animal-based biological LAL pyrogenic quantification tests, which are accepted today by the major health authorities worldwide for the release of commercial pharmaceutical products.

The increased cell density and product titer in biomanufacturing have led to greater use of depth filtration as part of the initial clarification of cell culture fluid, either as a stand-alone unit operation or after centrifugation. Several recent studies have shown that depth filters can also reduce the concentration of smaller impurities like host cell proteins (HCP) and DNA, decreasing the burden on subsequent chromatographic operations. The objective of this study was to evaluate the HCP removal properties of the Pall PDH4 depth filter media, a model depth filter containing diatomaceous earth, cellulose fibers, and a binder. Experiments were performed with both cell culture fluid (CCF) and a series of model proteins with defined pI, molecular weight, and hydrophobicity chosen to match the range of typical HCP. The location of adsorbed (fluorescently labeled) proteins within the depth filters was determined using confocal scanning laser microscopy. Protein binding was greater for proteins that were positively charged and more hydrophobic, consistent with adsorption to the negatively charged diatomaceous earth. The lowest degree of binding was seen with proteins near their pI, which were poorly removed by this filter. These results provide new mechanistic insights into the factors governing the filter capacity and performance characteristics of depth filters containing diatomaceous earth that are widely used in the clarification of CCF.

Beta-glucans are polysaccharides of D-glucose monomers linked by (1-3) beta-glycosidic bonds, are found to have a potential immunogenicity risk in biotherapeutic products, and are labeled as process contaminants. A common source of beta-glucans is from the cellulose found in traditional depth filter media. Typically, beta-glucan impurities that leach into the product from the primary clarification depth filters can be removed by the subsequent bind-and-elute affinity chromatography capture step. Beta-glucans can also be removed by a bind-and-elute cation exchange chromatography step, which is useful for removing beta-glucans introduced by a post-Protein A depth filtration step. However, the increasing prevalence of flowthrough polishing chromatography poses a challenge for beta-glucan removal due to the lack of any bind-and-elute chromatography steps after the post-Protein A depth filter. In this work, a depth filter flush strategy was developed to control beta-glucan leaching into the product pool. Different loading conditions for the depth filtration and subsequent chromatography steps were evaluated to determine the robustness of the optimized flush strategy. Carry through runs demonstrated greater than two-fold reduction in beta-glucan levels using the optimized wash as compared to standard filter flush conditions.

Technologies suitable for the harvest clarification of cell cultures have experienced significant advancements in recent years. These advancements are motivated in part by increased cell densities and impurity levels, widespread industry adoption of single-use technologies, evolving regulatory landscapes, and a resurgence of perfusion cell cultures for continuous processing. This chapter details the major recent developments in the field of harvest clarification and includes discussions of core methods as well as emerging technologies. Core solid/liquid separation technologies such as centrifugation and depth filtration remain as cornerstones for the clarification of batch and fed-batch processes while microfiltration processes are being adopted for perfusion processes. Legacy methods, such as centrifugation have also advanced to incorporate new bowl designs for high density cell cultures, and process modifications have been made to improve product quality. Scale-down models for replicating shear and separation efficiencies have been reported. Recent developments for depth filters include new encapsulated devices, multistage depth filtration, and all-synthetic depth media grades. Tangential flow filtration and alternating tangential flow microfiltration methods are being adopted for high cell density perfusion processes. Recent developments in the areas of cell culture pretreatment and flocculation technologies, particle size characterization, and indirect analytical methods will also be discussed.

Depth type composite filters are porous materials heavily loaded with adsorbents and can remove contaminants from liquids by combining mechanical entrapment and adsorption. There is still a need for developing high performance filters by controlling the internal structure at micro and nano level. In this study, highly fibrillated nanocellulose (NC) with increased surface area was used as partial substitute for the fibre matrix to tailor the filter structure as well as the adsorption and filtration performance. Polyamide-amine-epichlorohydrin (PAE) was added both to adjust the charge of medium and provide wet strength. Filters were fabricated by embedding perlite particles into the cellulose fibre matrix by papermaking technique. The structure of composites was characterized for pore size distribution and surface morphology. Adsorption and filtration characteristics were quantified using two model dyes and silicon dioxide particles. Adsorption was found to be electrostatically controlled and dependent on the charge of the dye molecules and the filter medium. The addition of NC doubled the removal of a cationic dye by increasing the surface area and the available negative charges; it however decreased the removal of an anionic dye by 75%. PAE addition decreased the adsorption of the cationic methylene blue dye, while increasing the adsorption of the anionic metanil yellow dye. Rejection by filtration of 1 µm particles was over 90% for all filters. This study demonstrates that highly fibrillated NC fibres combined with a cationic wet strength polyelectrolyte can be used to tailor the filter structure and properties.

Optimization of a depth filter structure requires information about the filter's performance during its loading with particles. In this paper a macroscopic model of filtration process was proposed. It was based on the description of the loading process of three different gradient fibrous filters produced in the melt-blown technology process. Due to the contamination deposition on fibers, a new method of determination of the filter porosity transition, was suggested. It was based on growth of the deposit mass accumulated in individual filter layers, which was defined upon the scanning electron microscope images, the clearance of layer samples, and the overall increase of the filter mass. Local phenomena, i.e. the agglomerate structure, its spatial distribution and resuspension, were exposed through a two-stage character of the process. The empirical correlations obtained for deposition kinetics and pressure drop development are helpful in filter design. By knowing the desired contamination removal, fiber diameter and porosity can be verified mathematically, so that the filter will work the most efficiently. The proposed description of the structural loading of the multilayer filter is simple and reliable. Further research on biotic and abiotic particle transport mechanisms should be performed.

Despite the world practice, in the Russian Federation immunization against hemophilic infection is carried out only for the children from risk groups, which may be due to the lack of production of this vaccine in the Russian Federation. Therefore, the development of technology for the preparation of polyribosylribitol phosphate (PRP, the active substance of the Hib vaccine) remains relevant. Earlier, the employees of the federal state unitary enterprise “Saint-Petersburg scientific research institute of vaccines and serums and the enterprise for the production of bacterial preparations” of Federal medical and biologic agency of Russia isolated and identified the strain of Haemophilus influenzae SPB type b B-7884. The conditions for cultivation of the strain B-7884 and primary isolation of PRP from the culture liquid were arranged. The aim of the work was to study the possibility of excluding the centrifugation stage for separating H. influenzae SPB type b B-7884 biomass before clarification on the cascade of filter discs, and the development of subsequent stages of PRP isolation from the obtained intermediate product. Materials and methods. PRP isolation from an inactivated culture liquid of strain B-7884 was carried out by centrifugation, filtration, precipitation, homogenization, extraction under various conditions. The concentration of PRP in the intermediate products was determined by the orcinol method, the identity was determined by the latex agglutination test. Results and discussion. The optimal scheme for isolation and purification of the active pharmaceutical ingredient PRP, including filtration through the cascade of deep filters Zeta plus LP 60 (0.3–0.6 μm) and Zeta plus LP 90 (0.1–0.3 μm), concentration and diafiltration on ultrafiltration cassettes with nominal molecular weight cut-off of 30 kDa, precipitation with 10% cetyltrimethylammonium bromide solution (5% v/v), with subsequent homogenization of the obtained precipitate (in the presence of 12.5% of ethanol from the concentrate volume) and extraction (32.5% ethanol), filtration through depth filters Zeta Plus SP 30 and carbon filters Zeta Plus Carbon R53, and precipitation by 1.0% (v/v) 4.0 M sodium chloride solution and freezing at –(20 ± 2)°C, was developed. Conclusion. The obtained results will become the basis for the further development of the polysaccharide substance and allow us to proceed to the next stage in the development of the vaccine against Haemophilus influenzae type b – conjugation with the carrier protein.

Background Integrated continuous production technology is of great interest in biopharmaceutical industry. Efficient, flexible and cost effective methods for continuous cell removal have to be developed, before a fully continuous and integrated product train can be realized. The paper describes the development and testing of such an integrated continuous and disposable set-up for cell separation by flocculation combined with depth filtration. Results Screening of multiple flocculation agents, depth filters, and conditions demonstrated that the best performance was obtained with 0.0375% polydiallyldimethylammonium chloride (pDADMAC; a polycationic flocculation agent) in combination with Clarisolve® depth filters. Using this set-up, a 4-fold decrease of filtration area was achieved relative to standard filtration without flocculation, with yields of ≥97% and DNA depletion of up to 99%. Continuous operation was accomplished using a simple tubular reactor design with parallelization of the filtration. The reactor length was selected to allow a 13.2-min residence time, which was sufficient to complete flocculation in batch experiments. Continuous flocculation performance was monitored on-line using focused beam reflectance measurement. Filter switch cycles based on upstream pressure were controlled by in-line pressure sensors, and were stable from one filter to the next. Conclusion It was demonstrated that stable and efficient continuous flocculation associated with depth filtration can be easily accomplished using tubular reactors and parallelization. Continuous cell separation is essential for the development of fully continuous integrated process trains. This cost-efficient disposable design run in continuous mode significantly reduces facility foot print, process costs and enables great flexbility. © 2017 The Authors. Journal of Chemical Technology & Biotechnology published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Depth filters are used throughout downstream bioprocessing, with specialized filter chemistries developed for removal of host cell proteins, DNA, and protein aggregates. These filters often show very broad breakthrough curves, but there have not been any previous analyses of this phenomenon. Protein breakthrough curves were evaluated for Ribonuclease A and α-chymotrypsin in two small-scale depth filter modules using PDH4 media containing diatomaceous earth. Computational fluid dynamics (CFD) simulations were developed, with flow in the porous media described using the modified Navier-Stokes equations incorporating a Brinkman flow term and a Langmuir binding model. The breakthrough curve in the stainless-steel module was much sharper than that in the commercial Supracap™ 50 capsule due to the more uniform axisymmetric flow field. The behavior in the Supracap™ 50 capsule was more complex, with multiple inflection points observed due to the different flow paths and the time-dependent saturation of the two layers of the depth filter media. These results provide important insights into the factors controlling protein binding/breakthrough in commercial depth filter modules.

Because there is no general design method for depth filters, especially for layered configurations, we here address this methodological gap. Using optimal control theory, paths of the filter coefficient, a measure for local filtration performance, are determined along the filter depth. An analytical optimal control solution is derived and used to validate the numerical algorithm. Two optimal control scenarios are solved numerically: In the first scenario, the goal of constant deposition along the filter depth is addressed. The second scenario aims at maximizing the time until some maximal pressure drop is reached. Furthermore, we present a computational strategy to derive discrete layers suitable for practical design from the continuous optimal control solutions. All optimized scenarios are compared to one-layered filter designs and significant improvements are found. As this work is based on strongly validated and widely used filtration models, the presented methods are expected to have broad applicability. This article is protected by copyright. All rights reserved.

Gaseous microemboli (GME) may originate from the extracorporeal circuit and enter the arterial circulation of the patient. GME are thought to contribute to cerebral deficit and to adverse outcome after cardiac surgery. The arterial filter is a specially designed component for removing both gaseous and solid microemboli. Integration of an arterial filter with an oxygenator is a contemporary concept, reducing both prime volume and foreign surface area. This study aims to determine the air-handling properties of four contemporary oxygenator devices with an integrated arterial filter. Two oxygenator devices, the Capiox FX25 and the Fusion, showed significant increased volume of GME reduction rates (95.03 ± 3.13% and 95.74 ± 2.69%, respectively) compared with both the Quadrox-IF (85.23 ± 5.84%) and the Inspire 6F M (84.41 ± 12.93%). Notably, both the Quadrox-IF and the Inspire 6F M as well as the Capiox FX 25 and the Fusion showed very similar characteristics in volume and number reduction rates and in detailed distribution properties. The Capiox FX25 and the Fusion devices showed significantly increased number and volume reduction rates compared with the Quadrox-IF and the Inspire 6F M devices. Despite the large differences in design of all four devices, our study results suggest that the oxygenator devices can be subdivided into two groups based on their fibre design, which results in screen filter (Quadrox-IF and Inspire 6F M) and depth filter (Capiox FX25 and Fusion) properties. Depth filter properties, as present in the Capiox FX25 and Fusion devices, reduced fractionation of air and may ameliorate GME removal.

Recent progress in mammalian cell culture process has resulted in significantly increased product titers, but also a substantial increase in process- and product-related impurities. Due to the diverse physicochemical properties of these impurities, there is constant need for new technologies that offer higher productivity and improved economics without sacrificing the process robustness required to meet final drug substance specifications. Here, we examined the use of new synthetic adsorptive hybrid filters (AHF) modified with the high binding capacity of quaternary amine (Emphaze™ AEX) and salt-tolerant biomimetic (Emphaze™ ST-AEX) ligands for clearance of process-related impurities like host cell protein (HCP), residual DNA, and virus. The potential to remove soluble aggregates was also examined. Our aim was to develop a mechanistic understanding of the interactions governing adsorptive removal of impurities during filtration by evaluating the effect of various filter types, feed streams, and process conditions on impurity removal. The ionic capacity of these filters was measured and correlated with their ability to remove impurities for multiple molecules. The ionic capacity of AHF significantly exceeded that of traditional adsorptive depth filters (ADF) by 40% for the Emphaze™ AEX and by 700% for the Emphaze™ ST-AEX, providing substantially higher reduction of soluble anionic impurities, including DNA, HCPs and model virus. Nevertheless, we determined that ADF with filter aid provided additional hydrophobic functionality that resulted in removal of higher molecular weight species than AHF. Implementing AHF demonstrated improved process-related impurity removal and viral clearance after Protein A chromatography and enabled a two-step purification process. The consequences of enhanced process performance are far reaching because it allows the downstream polishing train to be restructured and simplified, and chromatographic purity standards to be met with a reduced number of chromatographic steps.

The development of de-dusting hot gases is of increasing importance and growing interest, especially in advanced power generation systems and (petro-)chemical processes. High temperature de-dusting has advantages of exceeding dew points, enhancing energy recovery at higher temperatures, protecting the downstream heat recovery equipment from fouling or erosion, and potentially simplifying the overall process. Additional benefits are a reduced power consumption and the possibility to simultaneously capture gaseous pollutants (SO2, HCl) by the gas-solid reaction with injected alkali or by integrating catalysts to abate NOx, VOC (volatile organic compounds) and PCDD/F (polychlorinated dioxins and furans). Both porous ceramic and porous metal fiber filters have been proposed, with a growing preference for the rigid metal fibre filters. Either surface or depth filters are applied. The operation parameters of hot gas de-dusting by rigid fibre filters include the applied face velocity, the porosity of the filter fleece, its construction and the pulse jet cleaning performance. These parameters will be integrated into design equations to determine the operational pressure drop and filtration efficiency for a given gas flow rate, operating temperature, dust characteristics and pulse-jet cleaning mode. The broad range of potential applications of the filters prior to an energy recovery stage will be illustrated for petrochemical/chemical processes and for combustion and gasification. The expected durability and long-term successful operation necessitate a proper design of the filter media (porosity, pore size, thermal, mechanical and corrosion resistance). The appropriate fabrication materials will be evaluated, with stainless steel or high grade metal alloys recommended for use in the extreme conditions at high temperatures and pressures. Finally prospects and challenges are summarized.

As oily wastewater treatment has emerged as an urgent global issue, oil/water separation using functional filters is attracting significant attention as an environmentally friendly method of oily wastewater purification. Although functional filters based on wetting characteristics have already been developed, it is difficult to use them in the oil/water separation field due to their inability to handle a large amount of wastewater continuously. Herein, a strategy to continuously treat large amounts of oily water for practical application is reported. For the first time, we fabricate a robust superhydrophilic depth filter using a hydrogel material. This filter has great potential for treating large amounts of wastewater because of its large effective area, excellent mechanical and chemical durability, self-cleaning ability and high oil/water separation efficiency. Using this filter, we further develop a device to treat a large amount of wastewater continuously. The promising results demonstrated in this work show the potential applicability of our filter and device in the field of wastewater treatment.

To obtain reliable depth images with high resolution, a novel method is proposed in this study that fuses data acquired from time-of-flight (ToF) and stereo cameras, through which the advantages of both active and passive sensing are utilised. Based on the classic error model of the ToF, gradient information is introduced to establish the likelihood distribution for all disparity candidates. The stereo likelihood is estimated in parallel based on a 3D adaptive support-weight approach. The two independent likelihoods are unified using a maximum likelihood estimation, a process also referred to as a joint depth filter herein. Conventional post-processing methods such as a mutual consistency check are also used after applying a joint depth filter. We also propose a novel hole-filling method based on the seed-growing algorithm to retrieve missing disparities. Experiment results show that the proposed fusion method can produce reliable high-resolution depth maps and outperforms other compared methods.

Depth filtration is widely used for clarification of liquid feeds, including the purification of biopharmaceuticals. The performance characteristics of these depth filters can be strongly influenced by the local flow and pressure distribution within the filter capsule, but there is currently little information on these phenomena in commercial depth filter modules. This work used a combination of computational fluid dynamics (CFD), residence time distribution (RTD) measurements, and dye binding experiments to obtain detailed information on the pressure and flow distribution within a small-scale Supracap™ depth filtration capsule, containing two layers of depth filter media with different pore size, that is of high interest in bioprocessing. The results confirmed the presence of four distinct flow paths through the capsule, with less than 40% of the flow passing completely through both layers of the depth filter media and nearly 11% bypassing the large pore size prefilter layer. Model calculations were in good agreement with the measured RTD and images of dye binding, providing further confirmation of the flow phenomena. These studies provide important insights into the performance characteristics of these depth filters, while providing a framework that can be applied to analyze the pressure and flow distribution in other membrane and depth filtration modules.

A 5-D depth---velocity filter is proposed for enhancing moving objects in noisy light field videos (LFVs) (also known as plenoptic videos). The proposed filter consists of an ultra-low complexity 5-D IIR depth filter and a 5-D FIR velocity filter. The 5-D IIR depth filter is employed to denoise a noisy LFV. The denoised LFV is then utilized to estimate the 3-D apparent velocity of the moving object of interest. The 5-D FIR velocity filter is designed based on the estimated 3-D apparent velocity and is used to enhance the moving object of interest while attenuating other interfering moving objects. Experimental results confirm the effectiveness of the proposed 5-D depth---velocity filter compared to previously reported 5-D depth---velocity filters.

The existing depth video coding algorithms are generally based on in-loop depth filters, whose performance are unstable and easily affected by the outliers. In this paper, we design a joint weighted sparse representation-based median filter as the in-loop filter in depth video codec. It constructs depth candidate set which contains relevant neighboring depth pixel based on depth and intensity similarity weighted sparse coding, then the median operation is performed on this set to select a neighboring depth pixel as the result of the filtering. The experimental results indicate that the depth bitrate is reduced by about 9% compared with anchor method. It is confirmed that the proposed method is more effective in reducing the required depth bitrates for a given synthesis quality level.

Background: The indication for arterial line filtration (ALF) is to inhibit embolisation during cardiopulmonary bypass. Filtration methods have developed from depth filters to screen filters and from a stand-alone component to an integral part of the oxygenator. For many years, ALF has been a standard adopted by a majority of cardiac centres worldwide. The following review aims to summarize the available evidence in support for ALF and report on its current practice in Europe. Method: The principles and application of ALF in Europe was investigated using a survey conducted in 2014. The scientific evidence for ALF was examined by performing a systematic literature search in six different databases, using the following search terms: “Cardiopulmonary bypass AND filters AND arterial”. The primary endpoint was protection against cerebral injury verified by the degree of cerebral embolisation or cognitive tests. The secondary endpoint was improvement of the clinical outcome verified elsewise. Only randomised clinical trials were considered. Results: The response rate was 31% (n=112). The great majority (88.5%) of respondents were using ALF, following more than 10 years of experience. Integrated arterial filtration was used by 55%. Of respondents not using ALF, fifty-four percent considered starting using integrated arterial filtration. The systematic literature database search returned 180 unique publications where 82 were specifically addressing ALF in cardiopulmonary bypass. Only four out of the 82 identified publications fulfilled our inclusion criteria. Of these, three were more than 20 years old and based on the use of bubble oxygenation. Conclusion: ALF is a standard implemented in a majority of cardiopulmonary bypass procedures in Europe. The level of scientific evidence available in support of current arterial line filtration methods in cardiopulmonary bypass is, however, poor. Large, well-designed, randomised trials are warranted.

Ultra scale‐down (USD) methods operating at the millilitre scale were used to characterise full‐scale processing of E. coli fermentation broths autolysed to different extents for release of a domain antibody. The focus was on the primary clarification stages involving continuous centrifugation followed by depth filtration. The performance of this sequence was predicted by USD studies to decrease significantly with increased extents of cell lysis. The use of polyethyleneimine reagent was studied to treat the lysed cell broth by precipitation of soluble contaminants such as DNA and flocculation of cell debris material. The USD studies were used to predict the impact of this treatment on the performance and here it was found that the fermentation could be run to maximum productivity using an acceptable clarification process (e.g., a centrifugation stage operating at 0.11 L/m2 equivalent gravity settling area per hour followed by a resultant required depth filter area of 0.07 m2/L supernatant). A range of USD predictions was verified at the pilot scale for centrifugation followed by depth filtration. © 2016 The Authors Biotechnology Progress published by Wiley Periodicals, Inc. on behalf of American Institute of Chemical Engineers Biotechnol. Prog., 32:382–392, 2016

Depth filtration is employed in the production of many biological products. Although high throughput process development is available for most purification operations, options for high throughput depth filtration are limited. In this report, we describe the development and qualification of an ultra scale-down (USD) device for high throughput depth filtration. The system enables the parallel evaluation of eight single- or multi-layer depth filters approximately 0.2 cm2 in cross-sectional area, greater than two logs smaller than the smallest commercially available devices. To assess precision, scalability, modularity, and media heterogeneity in USD depth filtration, several types of adsorbent media were qualified in the USD device, with filtration performance compared to lab-scale devices (cross-sectional area: 23–25 cm2). The performance was further investigated with several high throughput clarity measurements, including particle characterization of filtrate fractions. Historically, depth filtration development has been limited by the amount of material required to run lab-scale filters. The described high throughput technology enables the screening of filter media early in development, optimization of operating parameters, and coupling of upstream operations to filtration performance. These high throughput capabilities will create efficiencies for development and manufacturing that were unattainable previously and create an important tool for screening novel biological entities.

The requirements for gas purification systems are getting increasingly stricter. This is due to the development of new technologies, increasing environmental pollution, and greater emphasis placed on the protection of human health and the environment. Fibrous filters are among the most widely used tools for removing particles from fluids. This paper explains the very complex process of the non-steady state aerosol particle filtration in fibrous filters using such a technologically advanced solution as an X-ray computed tomography for this purpose. Since online monitoring of the process inside the filter structure or marking particles flowing into the filter in any way, which would facilitate distinguishing between fresh and replaced particles, might be difficult to deploy, a simulation of the process was chosen instead. The experiment was divided into four stages. At the first stage, the advantages of the melt-blown technique were adopted to produce two non-woven fabric types of a given structure – one made of micro-sized fibers, and the other made of submicro- and nano-sized fibers. At the subsequent stage, the provided separating materials were loaded with solid silica particles in identical conditions, and then a stream of clean air at various flow velocities was blown through them. This experiment was designed to examine the behavior of the deposits in the filter during filtration, observe whether they travel inside the filter structure, remain in place or entirely leave the filter. At the last stage of the process, a macroscopic analysis of the filter structure and silica particles deposited inside it was carried out using an X-ray microtomography system. Based on the acquired tomography images, profiles of changes in local porosity of the filters along their depth were made. It was found that deposited particles re-entrain from the fibers during filtration process but they do not leave the filter, only move to its deeper parts.

Depth type composite filters are used to remove contaminants from liquids by combining mechanical entrapment and adsorption. Commonly, depth filters can adsorb either anionic or cationic charged contaminants, but not both, as well as filter micron-sized particles. Therefore, there is still a need to improve the existing depth filter performance. In this study, we developed a two-layer filters with enhanced functionality by spray coating an anionically charged cellulose nanofibre (CNF) layer onto a cationically charged depth filter layer. The depth filter layer was prepared via papermaking technique of vacuum filtration from wood pulp fibres, perlite adsorbent and cationic polyamide-amine epichlorohydrin (PAE) wet strength resin. The CNF coat weight ranged from 4 to 30 g per square metre (gsm). The two layer filters were proven to have triple functionality, capable of adsorbing anionic molecules in the cationic depth filter layer, while the anionic CNF layer could adsorb cationic molecules and was also a microfiltration membrane. A gradual increase in CNF coat weight improved filtration performance but decreased the filter flux. The optimum performance was found at an 8 gsm CNF coat weight, where the membrane layer rejected 80% of 5000 kDa molecular weight polyethylene glycol, at a flux of 133 Litres per square meter per hour (LMH) under 1.5 bar pressure, while still achieving a good breakthrough curve when absorbing cationic methylene blue dye.

In underground mining operation, air is contaminated with fine dusts that can be removed by filtration effectively. Filter cleaning is envisioned to prolong filter media lifetime and to ensure uninterrupted operation requiring little maintenance. For cake filtration, reverse airflow or pulse flow, or filter shaking are widely used. But for depth bed filtration which is needed to meet more stringent emission requirement, continuous filter cleaning is generally not practical. The concept of continuous liquid rinsing of depth filter media is proposed and preliminary studies are performed. These laboratory studies on single vertical fibers include hydrodynamic tests of water along various filter fibers as well as cleaning with different sample dusts. All tested fibers have hydrophobic properties that result in the formation of clamshell droplets with moderate particle removal success. Small, plate-like particles are particularly difficult to remove. Comparative tests with oil that forms a homogeneous film provide excellent particle removal.

Depth filtration is widely used in downstream bioprocessing to remove particulate contaminants via depth straining and is therefore applied to harvest clarification and other processing steps. However, depth filtration also removes proteins via adsorption, which can contribute variously to impurity clearance and to reduction in product yield. The adsorption may occur on the different components of the depth filter, that is, filter aid, binder, and cellulose filter. We measured adsorption of several model proteins and therapeutic proteins onto filter aids, cellulose, and commercial depth filters at pH 5-8 and ionic strengths

In this paper, we summarize on an approach which couples the multiscale method with the homogenization theory to model the pre-treatment depth filtration process in desalination facilities. By first coupling the fluid and solute problems, we systematically derive the homogenized equations for the effective filtration process while introducing appropriate boundary conditions to account for the deposition process occurring on the spheres’ boundaries. Validation of the predicted results from the homogenized model is achieved by comparing with our own experimentally-derived values from a lab-scale depth filter. Importantly, we identify a need to include a computational approach to resolve for the non-linear concentration parameter within the defined periodic cell at higher orders of reaction. The computational values can then be introduced back into the respective homogenized equations for further predictions which are to be compared with the obtained experimental values. This proposed hybrid methodology is currently in progress.

Rapid depth filtration is the dominant pre-treatment technology in seawater desalination industry today. Optimizing the pre-treatment filter’s energy performance provides economies of scale in the total energy usage of desalination facilities on a broader sense. However, this objective remains difficult to achieve by far. In this study, we develop a numerical algorithm, termed as Dynamical Rapid Filtration Model (DRFM), to simulate the effective clogging dynamics occurring inside a depth filter which depends on a multitude of controlled and non-controlled operating parameters. DRFM quantifies the filtration kinetics with a modified Yao’s model to represent the particle removal mechanisms occurring within the simulated filter. A unique length scale is also introduced to account for the particle size effect on the filter’s energy loss rate incurred, i.e. its energy performance, during its effective filtration stage. Concurrently, we performed an experimental study with a lab-scale depth filter to develop a model equation for measuring its total contaminant mass removal rate ( R c ) due to effective clogging conditions. For a predicted R c transient profile, good agreement is obtained between the experimental results and predicted values from DRFM. We then extensively discuss on a novel DRFM hybrid model to optimize the filter’s energy performance which subsequently affects the filter’s optimized backwashing timing for achieving economies of scale. The simulation results from the hybrid model demonstrates on how various filter configurations can result in lower energy cost to effectively pre-treat each unit volume of intake seawater as compared to the current industrial average of 0.39 kWh / m 3 . Finally, we include a cost analysis to demonstrate on how the obtained economies of scale alleviates a portion of the total energy cost for each unit volume of desalinated water.

[no abstract]

High titer (>10 g/L) monoclonal antibody (mAb) cell culture processes are typically achieved by maintaining high viable cell densities over longer culture durations. A corresponding increase in the solids and sub-micron cellular debris particle levels are also observed. This higher burden of solids (≥15%) and sub-micron particles typically exceeds the capabilities of a continuous centrifuge to effectively remove the solids without a substantial loss of product and/or the capacity of the harvest filtration train (depth filter followed by membrane filter) used to clarify the centrate. We discuss here the use of a novel and simple two-polymer flocculation method used to harvest mAb from high cell mass cell culture processes. The addition of the polycationic polymer, poly diallyldimethylammonium chloride (PDADMAC) to the cell culture broth flocculates negatively-charged cells and cellular debris via an ionic interaction mechanism. Incorporation of a non-ionic polymer such as polyethylene glycol (PEG) into the PDADMAC flocculation results in larger flocculated particles with faster settling rate compared to PDADMAC-only flocculation. PDADMAC also flocculates the negatively-charged sub-micron particles to produce a feed stream with a significantly higher harvest filter train throughput compared to a typical centrifuged harvest feed stream. Cell culture process variability such as lactate production, cellular debris and cellular densities were investigated to determine the effect on flocculation. Since PDADMAC is cytotoxic, purification process clearance and toxicity assessment were performed.

Traditional clarification of mammalian cell culture typically combines multiple separation technologies to remove cells in a primary step, and colloids in a secondary step. Recent advances in mammalian expression systems have not only led to cell cultures with very high density and increased protein titers, but also to feed streams with a high proportion of solids and colloids that reduce the efficiency of the separation step. Issues with scale-up, flexibility and installation limit the attractiveness of centrifugation, whereas clarification solely by depth filtration can be costly due to high filter areas required. Therefore, an efficient manufacture process must be developed to overcome these restrictions. In this study we present a complete separation solution that combines cell harvest pretreatment with a polycationic flocculating agent (polydiallyldimethylammonium chloride or pDADMAC), followed by depth filtration using depth filters that were specifically developed for filtration of flocculated or precipitated feed streams. Multiple antibody feed streams treated with pDADMAC and subsequently filtered using pretreatment adapted depth filters resulted in improved removal of cells and colloids, increased clarification throughput, efficient reduction of DNA and high process yield. The residual level of pDADMAC in the filtrates was assessed by surface plasmon resonance spectroscopy. Overall, this next generation clarification solution presented herein led to a robust, high yield, economical separation process with enhanced impurity removal that can be readily incorporated into current clarification platforms.

The surface charging properties of silica micro-particles in aqueous solutions before and after surface chemical amination were measured and analysed using a new approach to the theoretical modelling of ion adsorption. The surface of aminated silica microspheres were further modified by chemical adsorption of l -cysteine groups to determine their ability to adsorb low levels of arsenic ions from aqueous solution. The adsorption of arsenic ions was observed both from changes in particle surface charge and from direct solution analysis, using ICP-OES. The results obtained indicate adsorption levels of about 2–5% of the cysteine surface density, from low-level arsenic solutions (i.e. less than 1 ppm). These initial results indicate that a suitable silica-based depth filter could be developed for the removal of low-level arsenic ions from contaminated water.

The impacts and dynamic penetration of nanoparticle suspension drops into porous filter membranes are studied experimentally and theoretically. This type of penetration is associated with hydrodynamic focusing and is radically different from the wettability-driven imbibition. In the case of hydrodynamic focusing water can penetrate into a non-wettable porous medium at very low values of the dynamic pressure associated with drop impact. Two types of membranes are used in the experiments: (i) glass fiber filter membrane wettable by the carrier fluid (water), and (ii) polytetrafluoroethylene (PTFE) depth filter membrane, non-wettable by the carrier fluid. The nanoparticle entrainment and deposition inside the membrane bulk is used to mostly visualize the ultimate penetration fronts by observing the cut cross-sections of the membranes, albeit also provide an insight into innovative applications like circuit printing on nonwovens. The deposition patterns inside the membranes are also linked to the drop splashing patterns at their front surfaces. The experimental results confirm that during the dynamic focusing water can penetrate into a non-wettable porous medium (PTFE). Water also penetrates by the same hydrodynamic focusing mechanism into the wettable glass fiber membrane, where it additionally spreads on a much longer time scale due to the wettability-driven flow. A theory explaining hydrodynamic focusing penetration of liquid into porous medium after drop impact is proposed. It is used to explain and predict water penetration into the non-wettable filter medium after drop impact, and the results are compared with the experimental data. Also the critical thickness of non-wettable membranes determined by dissipation of the kinetic energy in flow inside membrane is evaluated and compared with the experimental data.

Human growth hormone is a single-chain polypeptide produced commercially from recombinant animal cells as well as recombinant microorganisms. Its increased applications have requested development of highly efficient production systems using particularly animal cells. Depth filter perfusion system (DFPS) has been developed and successfully used for production of recombinant proteins such as antibodies from recombinant Chinese hamster ovary (rCHO) cells. In this study, rCHO cells expressing recombinant human growth hormone (rhGH) were successfully cultivated in the DFPS for 2,200 h. Parameters affecting the performance of the DFPS for rhGH production were investgated. The depth filter with 40 µm pores was selected for stable operation. The shifts of culture temperature and pH were tested at 37 and 33℃, and 7.2 and 7.0, respectively. In the begining of the culture, more than 80% of the seeded cells were immobilized in 200 min by medium/cell circulation. When the culture temperature was lowered from 37 to 33℃, about 50% increase of the volumetric productivity (VP) at a perfusion rate of 2.0/day was achieved, and the VP reached 168 mg/L/d at perfusion rate of 3.0/day, showing the benefit of cultures in low temperature. In contrast, when pH was shifted from 7.2 to 7.0, maintaining rhGH concentration at about 60 mg/L and decreased perfusion rate from 2.0 to 1.0/day, the VP dropped to 50%. As the DFPS showed stable and efficient production of rhGH for long-term periods from this study, it can be an attractive choice for production of rhGH from recombinant animal cells.

A depth filter is widely used in biopharmaceutical manufacturing process. In this study, we found that buffer exchange to reduce conductivity dramatically improved the removal of impurities in depth filtration. The host cell protein clearance was comparable to that of protein A affinity chromatography, which is generally used as a first capture step in monoclonal antibody purification. In addition, a combination of different depth filters showed enhanced purification. Additional flow-through purification is possible without any sample preparation, and a biopharmaceutical-quality purity level (

Cell harvesting is the separation or retention of cells and cellular debris from the supernatant containing the target molecule Selection of harvest method strongly depends on the type of cells, mode of bioreactor operation, process scale, and characteristics of the product and cell culture fluid. Most traditional harvesting methods use some form of filtration, centrifugation, or a combination of both for cell separation and/or retention. Filtration methods include normal flow depth filtration and tangential flow microfiltration. The ability to scale down predictably the selected harvest method helps to ensure successful production and is critical for conducting small-scale characterization studies for confirming parameter targets and ranges. In this chapter we describe centrifugation and depth filtration harvesting methods, share strategies for harvest optimization, present recent developments in centrifugation scale-down models, and review alternative harvesting technologies.

There are essentially two main types of filters from a layout design point of view. There are those that are essentially ancillary fittings, such as line strainers, and those which are unit operations in their own right. Nowadays, filtration tends toward continuous operation, though batch and semibatch operation is still very important in the pharmaceutical, food, and water sectors. The most important technological advance in filtration in recent years has been the increased availability of consistent and economical membrane filters. As these tend to come in standardized packages of a fixed size, membrane plant layouts tend to be highly modularized.

The effect of increasing the hydrophobicity of poly(propylene) (PP) fibers, the most frequently used synthetic filter materials, on depth filtration performance was investigated. Reduced graphene oxide (RGO) was employed to fabricate highly hydrophobic surfaces by a dip-coating method. The anchoring of RGO on the surface of the PP fibers was confirmed by the appearance of signals corresponding to RGO in Raman and X-ray photoelectron spectra. In addition, scanning electron microscopy images revealed the presence of wrinkled and folded RGO sheets on the PP fibers. The water contact angle increased from 108° to 125° after the first RGO coating, and it was saturated at about 135°. Using kaolin as model hydrophilic particles, the depth filters with RGO-coated PP fibers showed a superior performance in terms of water flux and trans-filter pressure in comparison with those with the pristine and hydrophilic PP fibers prepared by coating functionalized GO. More importantly, particle detachment was enhanced by the hydrophobic coating during backwashing. This can be ascribed to the weakened attractive force between the RGO-coated fiber surfaces and kaolin particles due to the increase of hydrophobicity. This approach provides an effective means of enhancing the performance of synthetic fiber-based depth filters.

This work investigates the performance and optimization of a hybrid process consisting of a fixed-bed adsorption (FBA) column and a dead-end filtration (DEF) cell for the removal of methylene blue (MB) from water. Granular activated carbon and cellulose acetate depth filter sheets were used as adsorbent and filter medium, respectively. Effects of four operation parameters (initial concentration, feed flowrate, bed length, and filter type) on the MB removal rate (RR) were investigated using breakthrough data analysis and response surface methodology. This RR (mass of MB removed per second) captures the removal capacity and separation rate, simultaneously. The maximum RR was found theoretically equal to 3.875 s−1 at the optimized conditions of initial concentration =39.86 mg/L, flowrate = 1.15 L/min, bed length =29.95 cm, and filter type = OS100, and validated with the experimental data with 99% agreement. The performance of the hybrid process operating at the optimal operation conditions was found to be superior to those of the individual FBA column and DEF cell. After 100 s from the process commencement, the RR obtained with the hybrid process was about 64% higher than that obtained with the FBA column and 30% higher than that obtained with the DEF cell.

Depth filter media are usually composed of multiple layers to attain optimal values of main filtration parameters such as pressure drop and particle collection efficiency (PCE). Understanding the performance of the single layers that make up the filter media can contribute to attaining these optimum values. For the purpose of this study, we have developed two samples of depth filter media, 2LM and 3LM, composed of two and three layers, respectively. Samples of the media and single layers have been prepared in flat sheet form. Filtration performance of these samples has been evaluated using a lab-scale flat sheet filter media test unit with KCl as the test aerosol. Results from these tests have been compared with those from an automated filter tester (AFT) with NaCl as the test aerosol. These media have been characterized based on filter media properties and data from the filtration performance tests and the effect of layers on filtration performance has been observed. Pressure drop data from the tests wit...

Optimal bioreactor harvest time is typically determined based on maximizing product titer without compromising product quality. We suggest that ease of downstream purification should also be considered during harvest. In this view, we studied the effect of antiapoptosis genes on downstream performance. Our hypothesis was that more robust cells would exhibit less cell lysis and thus generate lower levels of cell debris and host-cell contaminants. We focused on the clarification unit operation, measuring postclarification turbidity and host-cell protein (HCP) concentration as a function of bioreactor harvest time/cell viability. In order to mimic primary clarification using disk-stack centrifugation, a scale-down model consisting of a rotating disk (to simulate shear in the inlet feed zone of the centrifuge) and a swinging-bucket lab centrifuge was used. Our data suggest that in the absence of shear during primary clarification (typical of depth filters), a 20-50% reduction in HCP levels and 50-65% lower postcentrifugation turbidity was observed for cells with antiapoptosis genes compared to control cells. However, on exposing the cells to shear levels typical in a disk-stack centrifuge, the reduction in HCP was 10-15% while no difference in postcentrifugation turbidity was observed. The maximum benefit of antiapoptosis genes is, therefore, realized using clarification options that involve low shear