•VTES-g-silicalite-1/PDMS/PAN thin film composite pervaporation membrane was designed.•Glucose, xylose, protein, and salts are impermeable components.•Fermentation nutrients at a lower concentration didn’t deteriorate the pervaporation performance.•The composite membrane shows outstanding fouling resistance in operation with fermentation broths.Organophilic pervaporation (OPV) has been considered as one of the most promising separation processes for the recovery of biofuels from fermentation broths, however, in addition to preferred target product – liquid biofuels, the yeast cells and fermentation nutrients could affect the recovery efficiency of biofuels from broths by pervaporation. In this paper, the influence of the yeast cells and the fermentation nutrient components such as the sources of carbon, nitrogen and salts on the separation performance of the vinyltriethoxysilane (VTES)-grafted- (VTES-g-) silicalite-1/PDMS/PAN thin-film composite membrane was conducted systematically. The results revealed that glucose, xylose, protein, and salts cannot permeate through the membrane. Glucose concentration in the fermentation broth should be kept at a lower level (less than 20 g/L) to eliminate its deleterious influence on ethanol flux and membrane selectivity. Xylose and corn steep liquor (CSL) have little effect on the pervaporation performance of the composite membrane. The addition of NaCl improved the membrane selectivity and ethanol flux but slightly lowered down total permeation flux. Adding dry yeast cells to the ethanol solution can enhance the turbulence in the feed mixtures, resulting an increase of the membrane flux and selectivity. The pervaporation performance of fermentation broths was also studied. The results showed that the nutrients and the deposition of yeast cells on the membrane surface didn’t deteriorate the pervaporation performance, indicating excellent fouling resistance of the novel VTES-g-silicalite-1/PDMS/PAN composite membrane in operation with fermentation broths. The continuous ethanol fermentation can be directly connected to the in-situ pervaporative recovery system without requiring prior removal of yeast cells.

•Ultrasonic probe-assisted enzymolysis technology was developed for the hydrolysis of soy sauce residue.•Effect of ultrasound on protease activity and SSR structure was investigated.•Increasing ultrasound treatment time or power could reduce substrate size.•Low ultrasound power was helpful for increasing the enzyme activity.•Different modes of ultrasonic probe-assisted enzymatic hydrolysis were compared.Ultrasonic probe-assisted enzymolysis technology was developed to improve the hydrolysis efficiency of soy sauce residue (SSR). The effects of enzyme type and enzymatic hydrolysis parameters on the hydrolysis degree of SSR were studied firstly to obtain the optimal enzymatic hydrolysis conditions. Then the effects of ultrasound on protease activity and structure of SSR were investigated to elucidate the acting mechanism of ultrasound. Finally, the ultrasonic-assisted enzymatic hydrolysis modes were designed and compared, and the hydrolysates from SSR were characterized to evaluate their further application. The results showed that a hydrolysis degree of 15.53% could be obtained under the optimum enzymolysis conditions: enzyme amount 6000 U/g, pH 7.8, temperature 50 °C, the ratio of substrate to water phase 1:20, hydrolysis time 4 h. Increasing ultrasound treatment time or power could reduce substrate size and consequently enhance the catalytic surface area. Prolonging ultrasound treatment time had a negative influence on enzyme activity, but low ultrasound power was helpful for increasing the enzyme activity. Ultrasound pretreatment of SSR followed by enzymatic hydrolysis increased the hydrolysis degree by 47.6%. When the ultrasound was applied directly to enzymolysis process, the hydrolysis degree of SSR exhibited an increase of 33.0%. The hydrolysates from SSR exhibited good antioxidant activities, and had a potential use as a functional ingredient in food or feed industry.

α,ω-Dicarboxylic acids (DC) are versatile chemical intermediates with different chain lengths, which are well-known as polymer building block. In this work, a new strain with high productivity of DC was isolated from oil-contaminated soil. Based on the morphology and phylogenetic analyses of the internal transcribed spacer sequences, it was characterized as Candida viswanathii. It was found that the contribution of carbon flux to the cell growth and DC production from n-dodecane could be regulated by the sucrose and yeast extract concentrations in the medium, and besides the broth pH, a suitable proportioning of sucrose and yeast extract was the key to achieve the optimal transition from cell growth phase to DC production phase. By optimizing culture conditions in a 7.5-L bioreactor, a higher DC productivity of 1.59 g·L−1 h−1 with a corresponding concentration of 181.6 g/L was obtained. After the purification of DC from the culture, the results from gas chromatography–mass spectrometry, infrared spectroscopy and 1H-NMR showed that α,ω-dodecanedioic acid (DC12) was the major product of C. viswanathii ipe-1 using pure n-dodecane as substrate. For the first time, we reported that a high productivity of DC12 could be produced by C. viswanathii.

•An integrated process recycles water, caseins, whey proteins and lactose.•This process can mitigate the sludge/retentate disposal and membrane fouling.•IP-UF pretreatment greatly reduces fouling and concentration polarization of NF.•NF retentate with concentrated lactose is obtained with IP-UF pretreatment.•Fermentation fed by NF retentate with IP-UF pretreatment produces more LA.An integrated isoelectric precipitation (IP) – ultrafiltration (UF) – nanofiltration (NF) – lactic acid (LA) fermentation process was established for recovering water, proteins, cells and LA from model dairy wastewater (MDW). This process could solve the problems of sludge/retentate disposal and membrane fouling during membrane-based wastewater treatment. The IP process greatly retarded concentration polarization and fouling of UF. However, PES membrane was still severely fouled by whey proteins. XPS results showed that carboxyl groups (CO) belonging to the proteins was on PES10 surface, but it was not found on Ultracel PLGC membrane. Proteins in MDW with IP were completely retained by Ultracel PLGC UF membrane and lactose almost passed through. After IP-UF pretreatment, the fouling of NF membrane was greatly retarded (irreversible fouling decreased from 44.4% to 11.1% in a pilot-plant test). Thus, the volume reduction ratio was highly increased to 37 and the retentate with high strength lactose of 44.2 g L−1 was obtained. With a model NF retentate (45.0 g L−1 of lactose) without proteins, 5.42 g L−1 of cell mass and 37.6 g L−1 of LA concentration were produced by the LA producer B. coagulans IPE22.Download high-res image (172KB)Download full-size image

•Co-utilization of wheat straw hydrolysates and n-dodecane improved DC12 production.•Glucose, xylose and sodium acetate are simultaneously assimilated by C. viswanathii.•DC12 production can be increased by the addition of sodium acetate.•Detoxification of the wheat straw hydrolysates is unnecessary for DC12 production.Candida viswanathii ipe-1 was used to produce α, ω-dodecanedioic acid (DC12), which showed capability to ferment xylose and glucose simultaneously, while arabinose utilization was less efficient. A low concentration of furfural enhanced cell growth, and the addition of 4.0 g/L sodium acetate largely increased DC12 production. It indicated that detoxification of the wheat straw hydrolysates was not necessary for the biosynthesis of DC12. Based on the promising features of our strain, an efficient process was developed to produce DC12 from co-utilization of wheat straw hydrolysates and n-dodecane. Using this process, 129.7 g/L DC12 with a corresponding productivity of 1.13 g·L−1·h−1 could be produced, which was increased by 40.0% compared with a sole carbon of glucose. The improved DC12 yield by the co-utilization of wheat straw hydrolysates and n-dodecane using C. viswanathii ipe-1 demonstrates the great potential of using biomass as a feedstock in the production of DC12.

•Biocatalytic membrane is prepared based on membrane chromatography concept.•PDA-based membrane adsorber is used for simultaneous enzyme purification and immobilization.•Flow-through mode is more efficient than dipping incubation for enzyme immobilization.•Regeneration of biocatalytic membrane is realized by reversible “elution-binding” process.•The prepared biocatalytic membrane has a high BPA removal by gravity-driven flow-through operation.Enzyme purification and subsequent immobilization usually require multiple steps and consume plenty of chemicals. Traditional dipping incubation operation is lengthy and the interior of porous carrier is not fully exploited due to the diffusion barrier. To solve these problems, one-step enzyme purification and immobilization was developed based on membrane chromatography concept. A membrane adsorber was prepared by polydopamine coating on a PVDF microfiltration membrane (or on a cheap and disposable cellulose filter paper) and subsequent polyethyleneimine grafting, without any solvent usage. Laccase was selectively immobilized on such membrane adsorber (enzyme activity: 39.9±4.4 U/mL; expressed activity: 19.6±3.0%) by directly capturing it from a crude fermentation broth without pH adjustment under flow-through mode. The immobilized laccase had a high purity of 92.2%, while the membrane permeability decreased due to the adsorption of laccase and impurities (“membrane fouling”). Thanks to the dominant convective transport, the enzyme loading was high and much faster than that by dipping incubation (5 min vs. 80 min). Moreover, enzyme reloading on membrane adsorber was easily realized by reversible desorption-adsorption process. The constructed biocatalytic membrane exhibited a commendable reusability for bisphenol A (BPA) removal only driven by its gravity.Download high-res image (239KB)Download full-size image

•Polydopamine-coated membrane can be used as a platform for fast ligand screening.•Ligand structure and molecular weight show a significant effect on membrane adsorber properties.•750 kDa polyethylenimine is selected as ligand for one-step purification of α1-antitrypsin.•High activity recovery (96.6%) and high purity of α1-antitrypsin (94.6%) are obtained.One-step purification of biomolecules from complex feed is challenging with commercial membrane adsorbers since it is difficult to screen and regulate the ligands on the membrane with traditional techniques for removal of various impurities. By readily grafting cationic polyelectrolyte ligands on a polydopamine (PDA)-coated membrane, a membrane adsorber with suitable ligand (750 kDa polyethylenimine, PEI) was selected to achieve one-step purification of α1-antitrypsin (AAT) from pretreated human plasma fraction IV. It was found that ligand structure and molecular weight showed a significant effect on the properties and separation performance of membrane adsorbers. The attached polyelectrolytes increased membrane hydrophilicity but caused an enhancement of filtration resistance, and quaternization of the ligands (PEI and polyallylamine) further improved the hydrophilicity but decreased the charge quantity. By further screening elution salt concentration, flow rate, buffer pH, loading volume as well as molecular weight of PEI ligands, a high activity recovery of 96.6% and a high purity of 94.6% of AAT were obtained by one-step membrane chromatography, which was even better than those by multiple-step method. This could be owing to the special multilayer structure of PEI chains, which could suppress the impurity protein binding on the adsorption sites by exclusion effect. The present work not only provides new insights into the purification of biomolecules from complex streams with polyelectrolyte-coupled membrane adsorbers, but also offers a new approach to design the ligands on membrane adsorber for specific application.Download high-res image (162KB)Download full-size image

•Membrane adsorber is prepared through dopamine coating on a hydrophobic membrane.•Dopamine coating increases hydrophilicity and mechanical strength of membrane adsorber.•Salt-tolerant anion-exchange membrane adsorber can well work at 200 mM NaCl.•A high recovery (∼100%) and high purity of IgG (>99%) can be achieved.•The prepared membrane adsorber has better reusability than the commercial one.In this study, a polyvinylidene fluoride (PVDF) hydrophobic membrane with high mechanical property was used as substrate to prepare salt-tolerant anion-exchange (STAE) membrane adsorber. Effective hydrophilization and functionalization of PVDF membrane was realized via polydopamine (PDA) deposition, thus overcoming the drawbacks of hydrophobic substrates including poor water permeability, inert property as well as severe non-specific adsorption. The following polyallylamine (PAH) coupling was carried out at pH 10.0, where unprotonated amine groups on PAH chains were more prone to couple with PDA. This membrane adsorber could remain 75% of protein binding capacity when NaCl concentration increased from 0 to 150 mM, while its protein binding capacity was independent of flow rate from 10 to 100 membrane volume (MV)/min due to its high mechanical strength (tensile strength: 43.58 ± 2.30 MPa). With 200 mM NaCl addition at pH 7.5, high purity (above 99%) and high recovery (almost 100%) of Immunoglobulin G (IgG) were obtained when using the STAE membrane adsorber to separate IgG/human serum albumin (HSA) mixture, being similar to that without NaCl at pH 6.0 (both under the flow rate of 10–100 MV/min). Finally, the reliable reusability was confirmed by five reuse cycles of protein binding and elution operations. In comparison with commercial membrane adsorber, the new membrane adsorber exhibited a better mechanical property, higher IgG polishing efficiency and reusability, while the protein binding capacity was lower due to less NH2 density on the membrane. The outcome of this work not only offers a facile and effective approach to prepare membrane adsorbers based on hydrophobic membranes, but also demonstrates great potential of this new designed STAE membrane adsorbers for efficient monoclonal antibody (mAb) polishing.

•A novel membrane adsorber is prepared by grafting alginate dialdehyde on nylon membrane.•Alginate dialdehyde (ADA) reacts with sodium bisulfite to generate sulphonic groups on ligands.•Sulphonic and carboxylic groups (both on membrane and ADA) endow a high binding capacity.•The novel membrane adsorber captures lysozyme from chicken egg white solution.•The purified lysozyme shows similar specific activity as commercial product.Fabricating membrane adsorbers with high adsorption capacity and appreciable throughput for the separation and purification of protein products is challenging in biomedical and pharmaceutical industries. Herein, we report the synthesis of a novel membrane adsorber by functionalizing a nylon microfiltration membrane with alginate dialdehyde (ADA) followed by sulphonic addition, without any solvent usage, and its successful application in the purification of lysozyme. Taking advantage of abundant dual cation exchange (CEX) groups on sulphonic-ADA (S-ADA) ligands, this novel S-ADA-nylon membrane adsorber showed an unprecedented static binding capicity of 286 mg/mL for lysozyme adsorption. Meanwhile, the prepared membrane adsorber could be easily regenerated (complete protein elution) under mild conditions and be reused at least for five times. Featured with a unique selectivity, the S-ADA-nylon membrane also captured lysozyme from chicken egg white solution with a high purity (100%) and a high recovery of 98%. The purified lysozyme showed similar specific activity as commercial product. The present work provides a facile, green and low-cost approach for the preparation of high-performance membrane adsorbers, which has a great potential in protein production.

•Metal chelating affinity membrane chromatography is used to prepare biocatalytic membrane.•Metal ions have a significant effect on laccase activity recovery and its specific activity.•Cascade catalysis with stacked biocatalytic membranes improves BPA degradation.•Membrane fouling by BPA polymerization products causes BPA removal decline.•Biocatalytic membrane regeneration is achieved by simple elution-cleaning-reloading.Biocatalytic membranes are promising to remove micro-pollutants in aqueous environment due to their mild and green operation condition. However, more efforts need to be devoted to improving their removal efficiency and stability. In this study, metal chelating affinity membrane chromatography (MCAMC) was used to construct a biocatalytic membrane by selectively capturing laccase from a crude fermentation broth. Metal ions had a significant effect on the activity of the immobilized laccase and copper ion was the best choice. A pH of 4.5 was selected for laccase adsorption and its loading seemed the same under flow rates from 0.5 to 10 mL min−1 thanks to the inherent convective transport of membrane chromatography. The pH value and salt concentration in the storage buffer had an obvious effect on the stability of the immobilized laccase, and the prepared biocatalytic membrane retained 87% of initial activity after 20 days storage. When applying such membrane to micro-pollutant removal (taking bisphenol A (BPA) as an example), a high BPA removal efficiency (99.3%) could be obtained. The biocatalytic membranes could be operated at a high flux of 50 L m−2 h−1 without recycling the permeate into the feed, and its throughput and BPA removal rate were superior to the most results in the literature. However, BPA removal decline (from 99.6% to 56.6% after five cycles) occurred during the successive water treatment due to the membrane fouling caused by BPA polymerization products. Membrane regeneration could be achieved by simple elution-cleaning-reloading, and the laccase activity and BPA removal were fully recovered.Download high-res image (132KB)Download full-size image

•VTES-g-silicalite-1/PDMS mixed matrix PV membrane was designed and prepared.•PV performance for VOCs aqueous solutions containing methanol was investigated.•The mixed matrix membrane showed high performance for recovering VOCs.•PV-based process provides an ecofriendly option for wastewater treatment.Recovery of volatile organic compounds (VOCs) from industrial wastewaters is important for the prevention of environmental pollution. This study investigated pervaporative recovery of VOCs by vinyltriethoxysilane (VTES)-grafted-silicalite-1/PDMS mixed matrix membrane (MMM) from the methanol-containing binary, ternary and quaternary wastewater solutions. The separation of methanol/water binary mixtures was first conducted. The influence of feed concentration and temperature on the membrane performance, such as permeation fluxes and VOC/water separation factor, was investigated. It was observed that with the increase of VOC concentration in the feed, the total permeation flux increased and the selectivity changed slightly first, then decreased. At a feed methanol concentration of 10.51 wt% at 65 °C, the maximum PSI of 5346 g/m2 h with a separation factor of over 10 were obtained with the VTES-g-silicalite-1/PDMS MMM, which makes it among the best in the literature and is very competitive for methanol recovery from aqueous solutions. The apparent activation energies of water and VOC during the pervaporation process was calculated based on Arrhenius equation. Then the mixed matrix membrane was applied to ternary and quaternary wastewater model solutions. Compared with binary methanol/water mixture, the addition of ethanol and/or acetone led to a decrease of the total flux, methanol flux, and methanol/water separation factor, but increased the total VOCs flux and the permeate VOCs concentration. Separation factors of individual VOC towards water follow the order of acetone > ethanol > methanol, which is consistent with those in binary aqueous mixtures.

Micropollutants present in water have many detrimental effects on the ecosystem. Membrane technology plays an important role in the removal of micropollutants, but there remain significant challenges such as concentration polarization, membrane fouling, and variable permeate quality. The work reported here uses a multifunctional membrane with rejection, adsorption, and catalysis functions to solve these problems. On the basis of mussel-inspired chemistry and biological membrane properties, a multifunctional membrane was prepared by applying “reverse filtration” of a laccase solution and subsequent “dopamine coating” on a nanofiltration (NF) membrane support, which was tested on bisphenol A (BPA) removal. Three NF membranes were chosen for the preparation of the multifunctional membranes on the basis of the membrane properties and enzyme immobilization efficiency. Compared with the pristine membrane, the multifunctional membrane exhibited significant improvement of BPA removal (78.21 ± 1.95%, 84.27 ± 7.30%, and 97.04 ± 0.33% for NT103, NF270, and NF90, respectively), all of which are clearly superior to the conventional Fenton treatment (55.0%) under similar conditions and comparable to soluble laccase coupled with NF270 membrane filtration (89.0%). The improvement would appear to be due to a combination of separation (reducing the enzymatic burden), adsorption (enriching the substrate concentration as well as prolonging the residence time), and lastly, catalysis (oxidizing the pollutants and breaking the “adsorption saturation limits”). Furthermore, the synergistic effect of the polydopamine (PDA) layer on the enzymatic oxidation of BPA was confirmed, which was due to its enhanced adsorption and electron transfer performance. The multifunctional membrane could be reused for at least seven cycles with an acceptable activity loss, demonstrating good potential for removal of micropollutants.Keywords: adsorption; enzyme; laccase immobilization; micropollutants; multifunctional membrane; nanofiltration

•PDA-coated PES membrane was applied to fabricate various membrane adsorbers.•Anion-exchange, hydrophobic interaction and affinity membrane adsorbers were prepared.•Membrane adsorbers exhibited a high selectivity in fractionation of IgG/HSA mixture.•This work provides a promising direction for facile fabrication of membrane adsorbers.Polydopamine, as an intermediate layer coated on PES membrane, was applied to fabricate various membrane adsorbers. Anion-exchange, hydrophobic interaction and affinity membrane adsorbers prepared by this facile method exhibited a high selectivity in fractionation of IgG (immunoglobulin)/HSA (human serum albumin) mixture. The anion-exchange membrane adsorber containing polyethylenimine (PEI) improved the HSA purity from 17.7% to 96.7%; The hydrophobic interaction membrane adsorber with Dodecyl mercaptan (DDM) as ligand obtained an IgG purity of 94.6%; Histidine attached affinity membrane chromatography achieved nearly a 100% purity of IgG. The present work indicated that the polydopamine layer not only activated membrane surface to attach various adsorptive ligands under the mild condition, but also reduced non-specific adsorption. Due to the versatile conjunction function, this facile mussel-inspired coating is also promising for the preparation of diverse membrane adsorbers.

During membrane processes of wastewater treatment, biofouling is a critical issue affecting membrane performance. Interspecies quorum quenching (QQ) by bacterial cells has been reported as a novel approach for mitigating the biofouling via restraining quorum sensing (QS), where secreted signaling molecules, e.g., acyl homoserine lactones (AHLs) being essential for biofilm formation are degraded by QQ bacteria. Herein, we isolated a novel indigenous QQ bacterium, Bacillus methylotrophicus strain WY from real wastewater sludge for controlling membrane biofouling. Strain WY was successfully characterized for QS and QQ activity and possessed a wide-ranging activity for degrading AHLs. More than 90% degradation for C8-HSL, C10-HSL, C12-HSL, C14-HSL, 3-oxo-C6HSL, 3-oxo-C8HSL and 3-oxo-C12HSL were achieved. Further, sodium alginate beads immobilized strain WY cells were applied to the microfiltration process. Compared to the vacant beads, using the beads with stain WY increased membrane flux by 3 to 4 times, demonstrating excellent biofouling control ability of strain WY.

•The order of rejection followed [BMIM]Cl > [BMIM]BF4 > [AMIM]Cl.•The organic cation in IL had an important effect on the IL rejection.•The solution-diffusion transport model can be used to predict the fluxes of ILs.•[BMIM]Cl in aqueous can be concentrated to 18.85 wt% using NF90 membrane.•NF is promising for concentrating IL.The study of filtration behavior in the concentration of ionic liquids (ILs) using nanofiltration (NF) membranes is of significance to recycle IL from the solution obtained by the dissolution of natural polymer and raw biomass. Firstly, the transmembrane pressure for the binary 1-allyl-3-methylimidazolium chloride ([AMIM]Cl) - H2O, 1-butyl-3-methylimidazolium chloride ([BMIM]Cl) - H2O and 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM]BF4) - H2O systems over the flux range from 6.64 to 132.74 L m−2 h−1 was examined using the dead-end filtration cell. Then, the solution-diffusion transport model was used to calculate the permeate flux of IL on the basis of radii of anion and cation in IL taken from literature. The real IL retention with NF270 was lower than that with NF90 which attained around 96% for [BMIM]Cl IL at a permeate flux of 53.10 L m−2 h−1. For the two membranes, the retention of [BMIM]Cl was higher than that of [BMIM]BF4 even if the radius of [BMIM]BF4 was slightly larger. Finally, under the optimal experimental parameters, [BMIM]Cl in the binary system of [BMIM]Cl-H2O can be concentrated to approximately 20 weight percent (wt%). All of these will provide necessary fundamental data for the application of NF technology to concentrate IL in the IL-H2O system.

•Highly purified α1-antitrypsin is obtained by a two-step membrane chromatography.•AEMC can be used for protein capture and preliminary purification.•HIMC can be used for final precise polishing.•Membrane chromatography outperforms column chromatography in α1-antitrypsin purification.•This work offers an alternative for extracting target protein from a dilute feed.The surging demand for plasma proteins, mainly driven by the growing market and the development of new therapeutic indications, is promoting manufacturers to improve the throughput of plasma proteins. Due to the inherent convective mass transfer, membrane chromatography has been proved to be an efficient approach for extracting a small amount of target proteins from large-volume feed. In this study, α1-antitrypsin (AAT) was extracted from human plasma fraction IV by a two-step membrane chromatography. An anion-exchange membrane chromatography (AEMC) was used to capture the plasma proteins in bind/elute mode, and the obtained effluent was further polished by a hydrophobic interaction membrane chromatography (HIMC) in flow-through mode. Under optimal conditions, the recovery and purity of AAT achieved 87.0% and 0.58 AAT/protein (g/g) by AEMC, respectively. After the precise polishing by HIMC, the purity of AAT was 1.22 AAT/protein (g/g). The comparison results showed that membrane chromatography outperformed column chromatography in both steps because of its high throughput. This two-step membrane chromatography could obtain an AAT recovery of 83.3% and an activity recovery of 91.4%. The outcome of this work not only offers an alternative process for protein purification from plasma, but also provides guidelines for manufacturing product from a large-volume feed with multi-components by membrane chromatography.

Alkaline pretreatment of lignocellulosic biomass produced certain amounts of alkaline-soluble lignin and phenolic compounds in the hydrolyzate, which might bring a negative effect on the alkali reuse for continuous biomass pretreatment. In the present work, lignin recovery from the alkaline rice straw hydrolyzate by ceramic ultrafiltration was investigated in terms of lignin retention and fouling mechanisms. Results showed that over 75% of lignin was retained using a ceramic membrane with the molecular weight cutoff (MWCO) of 5000 Da. The relative higher cross-flow velocity and lower pressure led to less resistance and membrane fouling, and complete or intermediate pore blocking was the most possible fouling mechanism. The alkaline solution from an ultrafiltration permeate was recycled for the pretreatment of fresh rice straw after a simple pH adjustment. By comparing the composition of solid residues and its enzymatic hydrolyzate after pretreatments with fresh and recycled alkaline solutions, it was found that the alkaline hydrolyzate could be polished by ultrafiltration for further reuse (at least four cycles). Moreover, the alkali recycling from the hydrolyzate could retard the release of phenolic compounds during the pretreatment. The consumptions of NaOH and water were reduced by 42% and 50%, respectively, during pretreatments with reuse of alkali. Alkali recycling benefits lignocellulose biorefinery by decreasing the costs associated with water and alkali supplementation as well as wastewater treatment.

•Hydroxycinnamic acids are separated from alkaline lignocellulosic hydrolyzate by NF.•Separation efficiency of hydroxycinnamic acids to aldehydes is optimal at neutral pH.•Higher NaCl concentration results in lower retentions of phenolics.•Concentration–diafiltration mode greatly improves the purity of hydroxycinnamic acids.•Mass percentage of hydroxycinnamic acids can reach 91.4% by NF.Alkali pretreatment could cause the degradation of the lignin of lignocellulose, releasing hydroxycinnamic acids and phenolic aldehydes into the hydrolyzate. Hydroxycinnamic acids (ferulic and p-coumaric acids) found in alkaline lignocellulosic hydrolyzate are high value-added products. Their separation and concentration from phenolic aldehydes were investigated using nanofiltration (NF) membrane with model solution and practical hydrolyzate. The effect of main operating parameters such as feed pH, permeate flux, NaCl concentration and the synergistic effect of pH and salt on the retentions of phenolic acids and aldehydes in the model solution were studied. Results indicated that the separation performance of hydroxycinnamic acids from aldehydes was optimal at neutral pH. All the phenolics retentions decreased with increasing NaCl concentration, especially for aldehydes. Salt and pH acted synergistic effect on phenolic aldehydes retention. When the practical alkaline hydrolyzate was treated under concentration–diafiltration mode, the mass percentage of hydroxycinnamic acids reached as high as 91.4%. This work demonstrated that NF could accomplish the separation and concentration of hydroxycinnamic acids from practical alkaline lignocellulosic hydrolyzate.

•EUF–ED was first applied in separation of lysozyme from bovine serum albumin.•EUF–ED had a higher flux than EUF with the lysozyme transmission remaining the same.•Ion migration during EUF–ED caused changes in pH and conductivity of feed solution.•The concentration polarization of lysozyme near CEM can affect the ion migration.An integrated process for improving selectivity and permeate flux in ultrafiltration based protein fractionation was developed by combining electrodialysis (ED) with electro-ultrafiltration (EUF). The performance of such a process was first investigated using individual proteins (bovine serum albumin and lysozyme) and then with a mixture of the two. The experimental results showed that as with EUF on its own, the build-up of lysozyme concentration polarization near the cation exchange membrane in the permeate compartment significantly affected ion migration and led to change in pH and conductivity of the feed solution during an EUF–ED process with lysozyme, or bovine serum albumin and lysozyme mixture. As compared with EUF, EUF–ED of protein mixture resulted in a 20% increase in permeate flux with the lysozyme transmission remaining the same. The demineralization that occurred during EUF–ED made this process suitable for protein separation from the feed solutions with high conductivity.

•Perfluorooctanoate (PFOA) can be concentrated and recovered by NF90 membrane.•The formation of PFOA micelles enhances the membrane performance.•Concentration polarization promotes the formation of PFOA micelles on the membrane.•Both acid and alkaline pHs deteriorate the NF performance for PFOA recovery.•Higher temperature results in more membrane fouling caused by PFOA.Perfluorooctanoate (PFOA) is a persistent chemical that has been detected globally in the natural aquatic environment, while the waste discharge of fluoropolymer industry is one of the major sources of PFOA pollution. In this study, the removal and recovery of PFOA by nanofiltration (NF) were investigated with ammonium perfluorooctanoate model solutions under a wide range of PFOA concentrations. Performances of two commercially available NF membranes, namely NF270, NF90, were evaluated. The results show that the NF90 membrane offered a higher PFOA rejection (almost 100% at a PFOA concentration below 800 mg L−1). Using NF90 membrane, a model solution with a higher initial PFOA concentration of 1000 mg L−1 was used to further test the membrane performance. Both stable osmotic pressure at membrane surface and high PFOA rejection (99.3%) were obtained when the PFOA concentration was larger than a certain value due to the formation of micelles. Furthermore, membrane operation parameters (i.e. stirring speed, pH, temperature, and permeate flux) on the TMP and the PFOA concentration in permeate were investigated under a much higher initial PFOA concentration (10,000 mg L−1). The experimental results clearly confirm that recovery of highly concentrated PFOA of more than 117073.7 mg L−1 could be achieved by one-step NF treatment, while the permeate could be further treated by multi-stage NF to fully recover the PFOA. It was also found that the permeability of membrane could be recovered completely by simple water rinse, suggesting that NF is highly applicable for recovery of PFOA from wastewater in fluoropolymer production.

Polyethylene oxide (PEO)-modified ultrafiltration (UF) membranes were prepared using polyacrylonitrile-graft-polyethylene oxide (PAN-g-PEO) copolymers through immersion precipitation phase inversion method. Compared to PAN membrane, the PEO-modified UF membranes possessed extraordinary hydrophilic surface owing to the enrichment of PEO segments, which was confirmed by X-ray photoelectronic spectroscopy (XPS). The effects of membrane hydrophilicity on the organic fouling resistance were investigated by means of the resistance-in-series model. The results showed that the hydrophilic modification of UF membrane contributed to the fouling control in bovine serum albumin (BSA) and Escherichia coli (E. coli) bacteria filtration. The antifouling ability of the membranes increased with increasing PEO content. The pure water flux could recover completely after filtering BSA and bacteria, respectively, for the membranes with 25.2% and 8.5% PEO content. In contract, the increase of membrane hydrophilicity had a negative effect on the humic acid (HA) and sodium alginate (SA) filtration. The membrane permeability of the PAN membrane unexpectedly increased after HA or SA filtration, while the flux recovery ratio of PEO-modified membranes decreased with increasing PEO content. The differences in fouling behavior of the various organic foulants on hydrophobic or hydrophilic membrane were attributed to the nature of organic foulants and their interaction with membranes.

The interest in ionic liquids (IL) is motivated by its unique properties, such as negligible vapor pressure, thermal stability, wide electrochemical stability window, and tunability of properties. ILs have been highlighted as solvents for liquid–liquid extraction and liquid membrane separation. To further expand its application in separation field, the ionic liquid membranes (ILMs) and its separation technology have been proposed and developed rapidly. This paper is to give a comprehensive overview on the recent applications of ILMs for the separation of various compounds, including organic compounds, mixed gases, and metal ions. Firstly, ILMs was classified into supported ionic liquid membranes (SILMs) and quasi-solidified ionic liquid membranes (QSILMs) according to the immobilization method of ILs. Then, preparation methods of ILMs, membrane stability as well as applications of ILMs in the separation of various mixtures were reviewed. Followed this, transport mechanisms of gaseous mixtures and organic compounds were elucidated in order to better understand the separation process of ILMs. This tutorial review intends to not only offer an overview on the development of ILMs but also provide a guide for ILMs preparations and applications.

β-Poly(malic acid) (PMLA) has attracted increasing attentions because of its potential application in medicine and other industries. In this study, the variation of PMLA molecular weight (Mw) in the batch culture and the strategies to enhance PMLA Mw were studied. Adding exogenous Ca2+ (0.1 g/L CaCl2) to the medium caused a significant increase in both PMLA concentration and Mw (11.38% and 26.3%, respectively) when Na2CO3 was used as the neutralizer. The Mw of PMLA during the process of batch culture, which associated with the specific PMLA production per unit cell mass (Yp/x) before glucose was depleted, increased from 12.522KDa to its maximum 18.693KDa and then kept decreasing until the end of the culture. Compared with the results in batch culture, Mw increased by 84.4% (up to 19.51 kDa) with a productivity of 1.1 g h−1 L−1 when the cells were maintained in exponential growth phase during Ca2+ added repeated batch culture. The present work provides an efficient approach to obtain superior quality PMLA product with high Mw.

•EUF–ED was first applied in separation of lysozyme from bovine serum albumin.•EUF–ED had a higher flux than EUF with the lysozyme transmission remaining the same.•Ion migration during EUF–ED caused changes in pH and conductivity of feed solution.•The concentration polarization of lysozyme near CEM can affect the ion migration.An integrated process for improving selectivity and permeate flux in ultrafiltration based protein fractionation was developed by combining electrodialysis (ED) with electro-ultrafiltration (EUF). The performance of such a process was first investigated using individual proteins (bovine serum albumin and lysozyme) and then with a mixture of the two. The experimental results showed that as with EUF on its own, the build-up of lysozyme concentration polarization near the cation exchange membrane in the permeate compartment significantly affected ion migration and led to change in pH and conductivity of the feed solution during an EUF–ED process with lysozyme, or bovine serum albumin and lysozyme mixture. As compared with EUF, EUF–ED of protein mixture resulted in a 20% increase in permeate flux with the lysozyme transmission remaining the same. The demineralization that occurred during EUF–ED made this process suitable for protein separation from the feed solutions with high conductivity.

•The role of PSF-b-PEG copolymers as pore formation additives was investigated.•The effects of copolymer composition, hydrophilic chain length and copolymer dosage were discussed.•The high PEG content in the copolymers favored the pore formation.•The PEG chain length seemed to have no influence on the pore size and size distribution.•The modified membranes exhibited the better antifouling ability and more durable stability.Polysulfone (PSF) membranes were prepared by nonsolvent-induced phase separation (NIPS) method using PSF-b-PEG copolymer as pore formation additive. The effects of copolymer composition, hydrophilic chain length and copolymer dosage on membrane morphologies, permeability, stability and biocompatibility were systematically discussed in order to determine the role of the additive. The results suggest that the copolymer composition and dosage play an important role in pore formation. The increase of PEG content in the copolymer results in larger pore size and narrower pore size distribution. The modified membranes show average surface pore sizes in the range of 11.4–15.2 nm, which increase by 14–52% compared to that of the pristine PSF membrane. With increase of copolymer dosage, the pore size increases first and then decreases. The hydrophilic chain length has no significant influence on the pore size and size distribution. The results of pure water flux and rejection agree with the variation of pore size. With increasing the copolymer dosage, the static adsorption of protein and platelet to the membrane is suppressed and thus the antifouling ability is improved. The PSF-b-PEG copolymer outperforms the common water soluble additive (i.e. PVP) in terms of the better pore forming ability and membrane stability, implying that the PSF-b-PEG copolymer would be an alternative to PVP in membrane preparation.