Μm Microfiltration Membrane Research Articles

Hybrid pasteurization strategy for energy conservation and quality preservation in cloudy apple juice processing

The study investigates the combination of microfiltration (MF) with traditional thermal pasteurization (TP), high-pressure processing (HPP), and electron beam irradiation (EBI) in the production of cloudy apple juice. Using 0.22 μm MF membranes instead of 0.45 or 0.1 μm, the highest flux was achieved, the permeate and retentate exhibited minimal deviation from raw apple juice (RAJ) in terms of physicochemical indicators. MF divided RAJ into a cloudy retentate containing microorganisms and a clarified permeate in a 1:4 vol ratio. The retentate was then pasteurized by HPP, TP, and EBI, after which it was mixed with the permeate to create cloudy apple juice. This innovative process reduced processed juice volume by 80% compared to single pasteurization method, decreased the loss of volatile compounds by 20.05%–33.52%, and cut energy consumption by 72.29%–75.35%. Overall, the hybrid pasteurization strategy approach shows great promise pasteurization technique for producing high-quality cloudy apple juice.

Near dissolved organic matter microfiltration (NDOM MF) coupled with UVC LED disinfection to maximize the efficiency of water treatment for the removal of Giardia and Cryptosporidium

Microfiltration (MF) membranes with a mean pore size same as or smaller than 0.45 µm have been typically used to separate pathogenic protozoa in water since materials larger than 0.45 µm are considered particulates. However, 0.45 µm is too small to separate protozoa which are 4–6 µm (Cryptosporidium oocyst) or 8–15 µm (Giardia cyst) in size. In this study, we optimized the mean pore size of MF membranes to maximize the producibility and guarantee a high removal rate simultaneously and proposed the membrane filtration using an MF membrane with an optimum mean pore size larger than but close to dissolved organic matter (DOM), which is called near DOM MF (NDOM MF). According to the MF test using polystyrene surrogate beads with diameters of 3 and 8 µm, an MF membrane with a 0.8 µm mean pore size was the best in that it showed 52% to 146% higher water fluxes than a 0.45 µm MF membrane while maintaining the removal rate at 3–4 log. It was also the case for a low-temperature MF test, revealing the NDOM MF is highly effective regardless of temperature changes. Lastly, we tried to find the possibility of combining the NDOM MF with disinfection by an ultraviolet light emitting diode (UVC LED) to further guarantee the high quality of treated water while providing high process efficiency.

Evaluation of hybrid pressure-driven and osmotically-driven membrane process for non-thermal production of apple juice concentrate

This study investigates the potential of hybrid membrane processes including microfiltration (MF), ultrafiltration (UF) and forward osmosis (FO) for non-thermal concentration of apple juice. The process performance and characteristics (physicochemical properties, nutritional and aroma components and microbiological quality) of apple juice were studied. The clarity of apple juice was significantly promoted as pore size of membrane reduced. MF and UF can also ensure microbiological safety in pre-treated apple juice. According to its efficiency of filtration as well as performance of simultaneous clarification and cold-sterilization, 0.22 μm MF membrane was identified as the optimal membrane for the pre-treatment. The pre-treated apple juice can be concentrated up to 65°Brix by subsequent single stage FO. FO retained nutritional and volatile compounds of apple juice while significant reductions were found in the juice concentrated by vacuum evaporation. Hybrid MF-FO can be a promising non-thermal technology to produce apple juice concentrate with high quality.

Enhanced removal of Pb(II) from contaminated water by hierarchical titanate microtube derived from titanium glycolate

Adsorbents with hierarchical hollow architecture are proved to be promising in wastewater purification. Herein, hierarchical titanate microtube (HTMT) has been fabricated by simple alkaline hydrothermal. The obtained HTMT presented hollow structure with large interior voids and countless external nanosheets. HTMT exhibited superior adsorption performance to eliminate Pb(II) from wastewater due to the large specific surface area as 80.4 m2 g−1 and abundant exchangeable intercalated Na+. HTMT showed maximum adsorption capacity as 540.5 mg g−1 at 298 K, fast adsorption rate and good reusability to remove Pb(II). Moreover, HTMT could selectively remove Pb(II) in the environment containing high concentration of interference cations(Na+, K+, Ca2+, Mg2+, Al3+) and heavy metals (Cu2+, Cd2+, Zn2+, Ni2+) with high efficiency. Furthermore, the large micron size of HTMT ensured the feasibility and reliability for reclamation of adsorbents by 0.45 μm microfiltration membrane. The adsorption mechanism was mainly ions exchange and inner-sphere complexation. The high adsorption capacity, fast adsorption rate, strong selectivity and good reusability make HTMT attractive for practical removal of Pb(II) from contaminated water.

Phenolic compounds from Syzygium cumini (L.) Skeels leaves: Extraction and membrane purification

A hybrid process consisting of extraction and microfiltration was proposed in this study for producing purified, clear and stable aqueous phenolic extract from jamun (Syzygium cumini (L.) Skeels) leaf. Response surface methodology was successfully used for optimization of extraction conditions. Pseudo-first order kinetic model successfully described the extraction of total polyphenols from jamun leaves, with the activation energy determined as 9.5 kJ/mol based on the Arrhenius model. The kinetic constants were used to study the kinetic and thermodynamic compensations of extraction of TPC from jamun leaves. Applying the statistical criterion, the kinetic and thermodynamic compensations were concluded to be real and the extraction process was controlled by entropy. A total of ten phenolic compounds including six phenolic acids (tannic acid, gallic acid, ellagic acid, caffeic acid, ferulic acid and p-coumaric acid) and four flavonoids (catechin, epicatechin, quercetin and myricetin 3-O-rhamnoside) were identified and quantified in jamun leaf extract obtained under optimum extraction conditions. The selection of appropriate membrane in the microfiltration step was a critical aspect. To observe the effect of membrane pore size on the permeate flux and permeate quality, leaf extracts were then microfiltered using four different microfiltration membranes (0.1, 0.22, 0.45, and 0.8 μm) under batch concentration mode. The flux decline was successfully described by the Hermia’s cake filtration model. The stability of clarified extract was investigated at 4 °C for 45 days. The 0.45 μm microfiltration membrane was suggested for the clarification of jamun leaf extract in order to achieve high flux, polyphenol recovery, extract purity and improved storage stability.

Application of Orbitrap high resolution mass spectrometry for the screening and identification of 15 adulterated weight loss compounds in dietary supplements

A liquid chromatography-Orbitrap high resolution mass spectrometry (LC-HRMS) method and a TraceFinder database were developed for the screening and identification of 15 adulterated weight loss compounds in dietary supplements. The samples were extracted with methanol and filtered through a 0.22 μm microfiltration membrane prior to LC-HRMS analysis. The Full MS/dd-MS2 mode was utilized in both positive and negative ion modes and the collected data were imported into the TraceFinder screening software. The established compound database and screening method were used for rapid, automatic, and high-precision screening to determine if the weight loss compounds were adulterated. The method validation results indicated that all of the analytes showed excellent linear relationships with regression coefficients (r) above 0.998. The recoveries were in the range of 79.7%-95.4% while the precisions ranged from 3.3% to 8.7%. The method and database were used to screen weight loss adulterants in 29 batches of dietary supplements; six batches of samples tested positive for adulterants with the identification of four compounds including sibutramine. This method enables the automatic high-precision screening and identification of adulterants, providing a novel and powerful tool for combating the increasingly rampant occurrence of adulteration in dietary supplements.

Cake Compressibility Analysis of BPOME from a Hybrid Adsorption-Microfiltration Process.

This study investigates the utility of a hybrid adsorption-membrane process for cake compressibility evaluation of biotreated palm oil mill effluent (BPOME). A low-cost empty fruit bunch (EFB) based powdered activated carbon (PAC) was employed for the upstream adsorption process with operation conditions of 60 g/L PAC dose, 68 min mixing time, and 200 rpm mixing speed to reduce the feed-water strength and alleviate probable fouling of the membranes. Two polyethersulfone microfiltration (MF) membranes of 0.1 and 0.2 μm pore sizes were investigated under constant transmembrane pressures (TMP) of 40, 80, and 120 kPa. The compressibility factors (z), which was obtained from the slopes of power plots (function of specific cake resistance (α) and pressure gradient) were evaluated. The z values of 0.32 and 0.52, respectively obtained, for the 0.1 and 0.2 μm MF membranes provided compressible and stable z values as observed from their power plots. Besides, these membranes were found suitable for the measurement of z since the results are in consonance with the established principle of cake compressibility. Moreover, the upstream adsorption mitigated the clogging of the membranes which ultimately led to moderate resistances and cake compressibility. These are indications that with the secondary cake filtration, a sustainable flux can be achieved during BPOME filtration. The membranes exhibited close to 100% restoration after cleaning.

Production of phage free cheese whey: Design of a tubular laboratory membrane filtration system and assessment of a feasibility study

An interposed “phage filtration” process step is proposed prior to subsequent processing of cheese whey to whey products to reduce fermentation risks due to phage contamination. At laboratory scale, the characteristics of three single tube ceramic membranes on the filtration performance in terms of phage retention, protein transmission and filtrate flux were analysed. From these tested membranes, a 0.1 μm microfiltration membrane was found to be suitable for significant phage reduction (3.4 log units) in cheese whey, simultaneously allowing total protein transmission of 56.2%. The experiments within the designed feasibility study conducted with a pilot plant microfiltration system provided a higher phage retention (4.1 log units) and a significantly increased transmission of major whey proteins (up to 84%) in comparison with the laboratory plant. The results shown in this study can easily be adapted by the dairy industry for better phage control and enhanced process safety.

Determination of residual toluene diisocyanate in sponge bra by gas chromatography

A gas chromatography (GC) with internal standard method was developed for the determination of residual toluene diisocyanate (TDI) in sponge bra. The samples were extracted with ethyl acetate dehydrated, and cleaned up with 0.22 μm microfiltration membrane. The residual toluene diisocyanate was separated on a DB-624 capillary column using temperature programming. The flame ionization detector (FID) was used at 250 ℃. The inlet temperature was 180 ℃ with nitrogen as carrier gas. The linear range was 10-200 mg/L (R2=0.9989) for TDI. The average recovery ranged from 80.5% to 91.6% with RSD not more than 7.9%(n=6). The limit of detection (LOD) and limit of quantification (LOQ) were 10 mg/kg and 100 mg/kg, respectively. The developed method was then utilized to analyse the 100 batches of sponge bra samples from the manufacturing enterprises, the entity shops and electric business platforms. The method is simple, time-saving and environment friendly with high sensitivity and good reproducibility, and has practical application value due to its low-cost and short-circle.

Examination of whey de-fatting by enhanced membrane filtration

The largest quantities of by-products of dairy processing originates from the cheese making. Whey proteins are used for animal feeding and human nutrition as well, for example in dry soups, infant formulas, and supplements. The fat components of the whey might impair its use. The aim of our experiments was to investigate the separation of the lipid fraction of whey. The microfiltration is said to be a gentle and energy efficient method for this task. During the measurements 0.2 μm microfiltration membranes were used and the membrane separation was enhanced by vibration, inserting static mixer and air sparging. The de-fatting efficiency, the retention of the whey components, the flux values, and the resistances in different combinations were compared in this paper.

Electrospun polyimide nanofiber membranes for high flux and low fouling microfiltration applications

A newly developed electrospun polyimide nanofiber mat/membrane along with three commercial 0.22µm microfiltration membranes have been investigated for applications within a renewable biorefinery to complete solid–liquid clarification at two locations: (1) following enzymatic hydrolysis (pre-fermentation) and (2) post-ethanol fermentation. Performance was assessed by evaluating process flux, reversible and irreversible fouling, and the ability to completely remove insoluble solids. Lignin (the primary insoluble solid following enzymatic hydrolysis of a biomass feedstock), yeast cells, and cell debris (following fermentation to ethanol), along with soluble phenolic compounds, all being very hydrophobic in nature, caused extensive fouling, which led to permanent irreversible flux decline for the three commercial membranes. In addition, all three commercial membranes showed a small amount of insoluble solids in the permeate, indicating incomplete removal of the insoluble solids. In contrast, the polyimide nanofiber membrane showed virtually no irreversible fouling and complete retention of insoluble solids, suggesting the tremendous potential for biorefinery applications.

Analysis of the different filtration parameters of whey by tubular and vibratory filtration systems

The largest quantities of by-product of the dairy, namely whey comes from the cheese making. The whey proteins are used by the agriculture in animal nutrition, and by the human nutrition as well; dry soups, infant formulas and supplements. The aim of our experiments was the separation of the lipid fraction of whey. During the measurements 0.05 μm, 0.2 μm and 0.45 μm microfiltration membranes were used in vibrating membrane filtration equipment (VSEP) and in a laboratory tubular membrane module. During the microfiltration, analytical characteristics, the fouling and the retention values were examined. Using the VSEP and the tubular module made possible to compare the effect of vibration, the static mixer and/ the airflow on the separation parameters.

Fouling phenomena during membrane filtration of microalgae

Harvesting of secreted fuel precursors is an alternative approach to sustainable biofuel production from algae, and relies on selective separation of growth media from algal suspensions. Membrane fouling and species fractionation for selected ultrafiltration (UF) and microfiltration (MF) membranes were investigated for this purpose. Suspensions were filtered using total recycle, flux-stepping protocols to measure fouling rates and subsequent fouling reversibility. Severe fouling was observed at high flux values for 50kg/mol UF and 0.22μm MF membranes, with much of the fouling irreversible. In contrast, a 5μm MF membrane showed essentially no increase in resistance, even though the whole algal cells were rejected to form a cake on the membrane surface. Analysis of the permeate from the 5μm MF filtration indicated the presence of “protein-like”, “humic-like”, and high-molecular-mass polymeric materials, as well as submicron particles. However, model solutions of dissolved organic material showed very low fouling compared to the as-grown algal suspensions. Instead, submicron particles present in the algal suspensions and in the 5μm MF permeate are thought to be the primary foulants by forming high-resistance cakes on the UF and 0.22μm MF membranes and also by plugging the pores of 0.22μm MF membranes. Thus, the flux decline and lack of “easy“ reversibility for our algal suspensions, filtered on specific membranes, appears to be primarily associated with deposition of smaller colloidal species within the membrane and/or near its surface, rather than with macromolecules or a cake of whole algal cells. Furthermore, membrane characteristics similar to those of the 5μmMF membrane employed may offer a unique strategy for separation of these undesirable particulate materials from healthy cultures of algae with large-enough size.

Plasmid DNA recovery from fermentation broths by a combined process of micro- and ultrafiltration: Modeling and application

Abstract Microfiltration and ultrafiltration operations were used in tandem to isolate and purify a 6050 bp plasmid DNA (pDNA). To achieve primary isolation of the plasmid from fermentation broths, immediately after cell lysis, a 0.2 μm microfiltration membrane was selected for solid/liquid separation, which was performed in a diafiltration mode, as an alternative to centrifugation. Then to attain plasmid concentration and purification, an ultrafiltration membrane with a pore radius of 4.1 nm was selected. Permeation of pDNA and RNA in the two membrane steps was modeled using recently published mass transfer models applicable to the permeation of closed segmented chains and freely-jointed chains, respectively. The permeation of proteins and genomic DNA (gDNA) was also studied in these operations. The microfiltration operation allowed high plasmid and RNA permeation, as expected. It was observed that significant amounts of gDNA, previously precipitated during the cell lysis step, reappear in solution during the diafiltration step. The effect of the ionic strength on this apparent re-solubilization was investigated, by testing the addition of two different salts to the diafiltration buffer: CH3COOK and CaCl2. The results show that these salts can be used to control gDNA apparent re-solubilization. During the ultrafiltration operation high plasmid retention with low adsorption was obtained under low ionic strength conditions. The results also show that a significant removal proteins and the re-solubilized gDNA is achieved, as well as some purification in respect to low molecular weight RNA, since all these components permeate through the ultrafiltration membrane.

Some observations on the chemical cleaning of fouled membranes

Multi-photon microscopy, a fluorescence based technique, was used to image in-situ the fouling and cleaning of a 0.22 μm microfiltration membrane fouled by bovine serum albumin and ovalbumin. Imaging of the cleaning was possible for two of the three cleaning regimes used. The free chlorine cleaner bleached the fluorescence labelling on the proteins and so visualisation of the process, whilst using this cleaner, could not be undertaken. However, during the use of solutions of either sodium hydroxide or Ultrasil 53, appropriate fluorescent labelling of the proteins allows the foulant species to be clearly identified. Cleaning with sodium hydroxide was less effective resulting in only 50% flux recovery. The cleaning mechanism was different and large aggregates remained on the membrane surface even after 1 h of cleaning. Images correlated well with filtration data and clearly show re-fouling of the membrane during the second half of the cleaning cycle by ovalbumin alone. The discussion includes observations on the need for one to be aware of the potential for this to occur and on the need for some studies to involve repeated cycles of fouling and cleaning.

Physiochemical, antioxidant and whitening properties of extract from root cortices of mulberry as affected by membrane process

Extract from root cortices of mulberry ( Morus alba, L.) was separated into permeate and retentate fractions using a membrane system equipped with either a microfiltration membrane or one of four molecular weight cut-off ultrafiltration membranes. The effects of membrane process at volume concentration ratio (VCR)=4 on the physiochemical characteristics, the contents of active compounds, antioxidant ability, and whitening capability (tyrosinase inhibitory activity) in permeate and retentate were evaluated. The clarification degree, antioxidant effects, and whitening capability of the permeates increased as compared to those of feed. In addition, permeate treated with a 0.45 μm microfiltration membrane exhibited less fouling layer and specific resistance (α pC B=622.8 m −2×10 −6) and thus had a higher permeate flux than treated with other ultrafiltration membranes (α pC B=786.1–1025.3 m −2×10 −6). A higher content of active compounds, such as chlorogenoic acid and p-hydroxybenzoic acid may explain higher antioxidant and whitening capabilities in permeate of extracts from root cortices of mulberry.

Tangential flow microfiltration and ultrafiltration for human influenza A virus concentration and purification

Large scale purification of viruses and viral vectors for gene therapy applications and viral vaccines is a major separation challenge. Here tangential flow microfiltration and ultrafiltration using flat sheet membranes has been investigated for concentration of human influenza A virus. Ultrafiltration membranes with molecular weight cutoffs of 100 and 300 kDa as well as 0.1, 0.2 and 0.45 microm microfiltration membranes have been tested. The results indicate that use of 300 kDa membranes not only concentrate the virus particles but also lead to a significant removal of host cell proteins and DNA in the permeate. Tangential flow filtration may be used to fractionate virus particles. Human influenza A virus particles are spherical with an average size of 100 nm. Use of a 0.1 microm membrane leads to passage of virus particles less than 100 nm into the permeate and an increase of larger particles in the retentate. These results suggest that control of the transmembrane pressure, membrane pore size and pore size distribution could enable isolation of intact virus particles from damaged virions. Isolation of the virus particles of interest from viral fragments and other particulate matter could result in simplification of subsequent purification steps. Larger pore size membranes such as 0.45 microm that allow the passage of all virus particles may be used to remove host cell fragments. In addition virus particles attached to these fragments will be removed. Careful selection of membrane morphology and operating conditions will be essential in order to maximize the benefit of tangential flow filtration steps in the purification of viral products from cell cultures.

Functional properties of ovine whey protein concentrates produced by membrane technology after clarification of cheese manufacture by-products

Functionality (solubility, emulsifying and foaming properties) of ovine cheese whey and deproteinized whey ( Sorelho) protein concentrates was evaluated. Both by-products of ovine cheese manufacture were clarified by thermocalcic precipitation and microfiltration using two pore size membranes (0.65 and 0.20 μm). Next, they were ultrafiltrated/diafiltrated, and then, the liophilization of the corresponding retentates was carried out. The functionality of these powders, as well as that of untreated ultrafiltrated whey protein concentrate (WPC) and microfiltration retentates powders, was evaluated. The clarification treatment increased solubility of the WPC produced from ovine whey and deproteinized ovine whey. Moreover, these products had foaming properties, whereas conventional WPC and microfiltration retentate powders (MFRP) were unable to produce foams. The whey product obtained after clarification using a 0.65 μm microfiltration membrane had the best foaming properties. The clarification treatment did not significantly increase emulsifying activity and stability, except for the Sorelho product obtained using a 0.65 μm membrane. MFRP from ovine whey and Sorelho, the by-products of the clarification procedure, showed similar solubility and higher emulsifying activity than conventional WPC, although their emulsion stability was lower. The clarification procedure studied, particularly when a 0.65 μm microfiltration membrane was used, improved some functional properties of the whey and Sorelho protein concentrates, and also generated microfiltration retentates for potential use in food manufacturing.

The modified fouling index using ultrafiltration membranes (MFI-UF): characterisation, filtration mechanisms and proposed reference membrane

The existing modified fouling index (MFI 0.45), based on cake filtration, uses a 0.45 μm microfiltration membrane to measure the particulate fouling potential of feedwater. To incorporate smaller colloidal particles into the MFI measurement, the application of ultrafiltration (UF) membranes was proposed. In this study, a suitable reference membrane for the MFI-UF test was investigated using polysulphone (PS) and polyacrylonitrile (PAN) UF membranes of 1–100 kDa molecular-weight-cut-off (MWCO) in tap water experiments. The stability of the MFI-UF value over time and the influence of MWCO on the MFI-UF obtained were examined. Field emission scanning electron microscopy (FESEM) of the membrane surfaces and an analysis using the constant pressure blocking and cake filtration models were carried out. A stable MFI-UF ∗ was found for PAN membranes. Whereas, the MFI-UF continuously decreased over time for PS membranes. The measured MFI-UF ∗ (2000–13,300 s/l 2) were significantly higher than the MFI 0.45 expected for tap water, (1–5 s/l 2), indicating smaller particles were retained. FESEM showed PAN membranes were homogeneously permeable, resulting in a stable MFI-UF ∗ value as cake filtration was proven to be the dominant mechanism. Whereas, FESEM showed the 1, 2 and 5 kDa PS membranes were heterogeneously permeable and sparsely porous resulting in (i) artificially high MFI-UF ∗ and (ii) limited cake filtration. Hence, the MFI-UF never stabilised. The MFI-UF ∗ appeared MWCO independent within the 3–100 kDa range as most likely the cake itself acts as a second membrane, determining the size of particles retained and the resultant MFI-UF ∗.

Valorization of by-products from ovine cheese manufacture: clarification by thermocalcic precipitation/microfiltration before ultrafiltration

The objective of this work was to valorize ovine cheese whey and deproteinized whey (Sorelho), resulting from portuguese whey cheese (Requeijão) manufacture, by means of thermocalcic precipitation and microfiltration (TP/MF) followed by ultrafiltration–diafiltration (UF/DF). The chemical composition of microfiltration and UF/DF retentate powders was studied and compared with that of conventional ultrafiltration powders, in view of further applications. Clarification of by-products from ovine cheese manufacture by TP/MF significantly improved posterior ultrafiltration treatments. When ovine cheese whey was used, microfiltration retentate powders obtained using a 0.20 μm pore size membrane showed higher protein concentration than powders produced with a 0.65 μm membrane, while no significant differences were found in the protein content of Sorelho MF powders. In all cases, UF/DF retentate powders from clarified products using a 0.65 μm microfiltration membrane showed the highest protein concentration. Clarified and diafiltrated products presented the lowest Ca2+ levels. It could be concluded that the clarification procedure studied, particularly the use of a 0.65 μm microfiltration membrane in clarification treatment, allowed us to obtain acceptable microfiltration fluxes and improved ultrafiltration rates and also gave rise to products of potential use in the food industry.