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Bacterial cellulose (BC) materials were used for lipase immobilization to improve enzyme activity and stability. BC films produced by Komagataeibacter xylinus were first acetylated in an acetic anhydride/iodine system to convert their OH groups to more hydrophobic acetyl groups. Activity yield (44.4%) and maximum specific activity (12.44 μmol mg–1 min–1) were achieved when 400 mg of BC was acetylated in 20 mL of acetic anhydride containing 0.275 mM of iodine. Studies on the catalytic activity of lipase also show that the immobilization of lipase on acetylated BC (ABC) films significantly enhanced its tolerance to temperature and pH. Immobilized lipases retained 89% and 56% of their catalytic activities after being incubated at 60 °C and 80 °C for 1 h, respectively; while those of free lipases significantly decreased to 24% (60 °C) and only 11% (80 °C). Immobilized lipases incubated at pH 5.0 and pH 10.0 for 24 h also retained high catalytic activities (70% and 82%, respectively), considerably higher than those of free lipases (19% - pH 5.0 and 63% - pH 10.0). Tolerance to organic solvents, such as n-hexane, acetone, ethanol, isopropanol of ABC-immobilized lipase was also improved. The immobilization of lipase on ABC films significantly improved its reusability and storage stability: ABC-immobilized lipase still could be reused for 30 cycles with residual activities of more than 90%, and still retained 95% of its early activity after 15-day storage at 4 °C. This implies that ABC-immobilized lipase is potentially applied in food, medicine, biodiesel and detergent industries.

Background Even though dragon fruit peel has more health benefits than its pulp, it is considered to be waste after fruit processing. In this study, dragon fruit peel was explored as an additional ingredient in winemaking. Methods The contents of total phenolic compounds, betacyanins and ascorbic acid, the antioxidant capacity by DPPHž method, and the level of consumer acceptability of the wines prepared from two species with and without peel were compared. Results The wines of the H. polyrhizus species contained much higher total phenolics (1.4-1.6 times), betacyanins (75-81 times), and vitamin C (2.8-3.8 times), as well as higher 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity (1.2 times) than the wines of H. undatus. Although the fermentation process led to the degradation of betacyanins, it increased the total phenolics (up to 17%), vitamin C (up to 24%), and DPPHž scavenging activity (up to 19%) as compared with the control when fermentation was conducted at 25°C, which was found as the most suitable fermentation temperature to produce wines with the highest quality in terms of antioxidant content and activity. At this temperature, peel inclusion also increased these values in the wine. In addition, the sensory properties in terms of appearance and aroma could be improved in the final fermented product. Conclusions H. polyrhizus wine might have higher antioxidant properties than H. undatus wine. With a suitable fermentation temperature, peel inclusion as an ingredient could enhance these characteristics of the wine without compromising its sensory quality. This study may provide insights into fruit winemaking with higher health benefits.

In this study, the usage of α-amylase and wheatgrass powder supplement was investigated to reduce the fermentation duration and fortify the nutritional values of banh bo (white honeycomb cake), an indigenous cake made from rice flour and tapioca starch in Vietnam. The results indicate that the addition of 0.05 wt% and 0.07 wt% α-amylase could significantly reduce total fermentation duration from 11 to 6 h while the fortification with 0.5–2 wt% wheat grass did not significantly influence the process. All the batters exhibited strong non-Newtonian behavior, but higher consistency of batters was obtained with the addition of α-amylase. All the resultant cakes did not display a significant difference in porosity, except the cake of 0.2 wt% wheat grass. The hardness and chewiness values decreased gradually with the increase in added enzyme content, but their increasing trends were observed with the addition of wheatgrass. The supplement of wheatgrass powder significantly increased the contents of chlorophyll and phenolic compounds, which both were responsible for the increments in antioxidant capacity. Hedonic tests indicate that the sensory attributes of the final products were successfully maintained. The study may provide insights in cereal-based fermented foods.

BACKGROUND: Red‐fleshed dragon fruit contains high amounts of heat‐sensitive betacyanin pigments that require non‐thermal technologies in their processing. Ultrafiltration (UF) can be a promising alternative technique for fruit juice clarification and cold sterilization. RESULTS: This study reported clarification of red‐fleshed dragon fruit juice by UF employing polyethersulfone UF membranes with pore sizes of 5, 10, and 20 kDa operated at three different transmembrane pressures of 1, 2 and 3 bar. Findings indicated that dragon fruit juice was best ultrafiltrated with the 10 kDa UF membrane at 3 bar, which resulted in the highest permeate flux (around 7.9 kg m⁻² h⁻¹), lowest retention of betacyanins (30.6%) and phenolic compounds (11.3%), as well as having the closest 2,2‐diphenyl‐2‐picrylhydrazyl hydrate scavenging ability as compared to that of the control. Resistance analyses presented that cake resistance (69–94%) played the major role in decreasing flux and was the dominant fouling cause in the UF process, while reversible (5–25%) and irreversible resistances (1–16%) had lesser impacts. Membrane characterizations using scanning electron microscopy and Fourier‐transform infrared spectroscopy suggested that the chemical structure and surface morphology of the UF membrane were hardly altered after being used and washed with detergents. Liquid chromatographic–mass spectroscopic analyses demonstrated that UF was successfully employed for juice clarification without affecting heat‐sensitive compounds of fruit juices such as betacyanins. CONCLUSION: Simultaneous selection of suitable membrane pore size and operation pressure is crucial for UF of fruit juice. UF is a promising technique in processing bioactive compound‐containing liquid foods. © 2021 Society of Chemical Industry

Thai basil leaves (Ocimum basilicum var. thyrsiflorum) have been used in food flavoring and traditional medicine. Hot-air drying is a convenient and low-cost method to preserve them for long-term use but causes the loss of their bioactive compounds during the process. In this work, the effect of pre-blanching on preserving these characteristics of Thai basil leaves dried at different air temperatures was studied. The antioxidant characteristics were evaluated by the contents of total phenolics, total flavonoids and total chlorophylls and the scavenging capacity against 2,2-diphenyl-1-picrylhydrazyl (DPPH) radicals. In addition, the inhibitory activities against starch-digesting enzymes were assessed with α-amylase and amyloglucosidase. At the air temperature of 50oC, antioxidant characteristics of dried leaves with pre-blanching were proven better than those without blanching and came close to those of the fresh sample. The drying temperature had more evident effects on inhibitory activities against starch-digesting enzymes than blanching. These activities of hot-air dried leaves were comparable to those of the fresh one. This study could provide insights into the integration of blanching and hot-air drying to preserve medicinal plants.

The work was supported by King Abdullah University of Science and Technology (KAUST), grant number FCC119713201.

Ethylene glycol (EG) and its derivatives were proposed as internal coagulants to spin hollow fiber membranes of the commercial polymer poly(ether imide) (PEI) and compared with water. The thermodynamic and kinetic characteristics of the polymer–solvent–nonsolvent systems were analyzed. The morphology and ultrafiltration performance of the resultant membranes were investigated. Water leads to a fast precipitation rate while a slow process is obtained for EG derivatives because of their high viscosity, large molecular size, and weak nonsolvent capability. The hollow fibers prepared with EG derivatives as bore fluids have thinner walls, which promote less resistance to the permeant transport. High rejections of bovine serum albumin (66 kg/mol), ovalbumin (45 kg/mol), and α-lactalbumin (14 kg/mol) were detected. The good performance combined with the nontoxicity of the EG derivatives makes them promising coagulants for membrane fabrication.

Green-kernel black bean (Vigna cylindrica (L.) Skeels) were processed with various treatments including soaking, roasting, cooking, autoclave and germination. The effects of these treatments on the chemical compostion, mineral, anti-nutrients, antioxidant and physical properties of the resultant flours were analyzed. The results indicate that green-kernel black bean was excellent sources of dietary fiber (165.4 g/kg), magnesium (2190 mg/kg), anthocyanin (791.6 mg/kg) and phenolic compounds (4.4 g gallic acid equivalent/kg), which were virtually higher than those reported for other pulses. Among the studied processing methods, cooking and autoclave provided the most evident effects on all flour characteristics, where the water holing capacity was enhanced and the flour became brighter. In addition, the levels of anti-nutrients such as tannin, saponin and trypsin inhibitors remarkably reduced and hence the starch digestibility was improved. However, antioxidant compounds were degraded or lost, leading to lower antioxidant capacities in terms of 2,2-diphenyl-2-picrylhydrazyl hydrate (DPPH) free radical scavenging ability and ferric reducing antioxidant power (FRAP). On the other hand, germination resulted in lesser reduction of anti-nutrients but lesser losses of antioxidants and good starch digestibility. Meanwhile, roasting caused the least effects on flour characteristics but was still able to partially degrade anti-nutrients.

In this chapter the state of the art of polyhedral oligomeric silsesquioxane (POSS) nanocomposites used in membrane-based separations for water treatment is reviewed, taking into account representative examples in applications. Transport principles and mechanisms of these processes are briefly discussed. Emphasis is placed on the transport properties of POSS nanocomposites and how POSS chemistry influences them. Tailoring functional side groups of POSS particles and their content is an appealing approach to control pore size or free volume precisely in nanoscale to enhance membrane permeability and selectivity. The inherent properties of POSS cage structure can also be considered to enhance mechanical strength and resistance of membranes under harsh operation conditions.

Cactus (Opuntia ficus-indica), commonly referred as prickly pear or nopal cactus, belongs to the family Cactaceae. It has attracted domestic and international industries’ attention owing to its nutritional and health benefit potentials. In this project, the quality of the cactus cladode juice after treated with the enzymes Pectinex Ultra SP-L and Viscozyme was investigated in terms of total phenolic content (TPC) and 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging activity. There were significant increases in the effectiveness of these enzymes as the concentration increased from 0.05 to 0.15% w/w. Among different concentrations, 0.15% w/w produced a higher yield and high-quality juice. Furthermore, the result indicates that prolonging the incubation duration could improve juice yield but this occurred only within the first hour of reaction, which the highest yield was obtained at 0.75 h. At these conditions, the combination of Pectinex Ultra SP-L and Viscozyme at ratio 1:1 (w/w) showed the most effective on juice yield improvement and 2,2-diphenyl-1-picrylhydrazyl free radical scavenging activity, while the highest total phenolic content was obtained when treating with Pectinex Ultra SP-L. Particularly as compared to the control sample, the juice yield increased from 53% to 76%, the TPC enhanced from 47 μg gallic acid equivalent (GAE)/mL to 70 μg GAE/mL, and the DPPH free radical scavenging activity improved from 277 μg ascorbic acid equivalent (AAE)/mL to 470 μg AAE/mL. Overall, the quality of cactus juice was better with enzymatic treatment than that of the untreated juice. The data also showed that the cactus juice behaved as shear – thickening fluids at room temperature.

The geometry of polymeric hollow fibers for hemodialysis or desalination is a key factor determining their performance. Deformations are frequently observed, but they are rather random. Here we were able to exactly control the shape evolution of the internal channels or lumens of polymeric hollow fibers, leading to polygonal geometries with increasing number of sides. The elasticity of the incipient channel skin and instabilities during fiber formation are affected by the internal coagulant fluid composition and flow rate; and highly influence the polygonal shape. We propose a holistic explanation by analyzing the thermodynamic, kinetic and rheological aspects involved in the skin formation and their synergy.

We proposed the use of ethylene glycol and its mixture with water as bore fluid for the preparation of poly(ether imide) (PEI) hollow fiber membranes and compared their performance and morphology with membranes obtained with conventional coagulants (water and its mixture with the solvent N-methylpyrrolidone (NMP)). Thermodynamics and kinetics of the systems were investigated. Water and 1:1 water:EG mixtures lead to fast precipitation rates. Slow precipitation is observed for both pure EG and 9:1 NMP:water mixture, but the reasons for that are different. While low osmotic driving force leads to slow NMP and water transport when NMP:water is used, the high EG viscosity is the reason for the slow phase separation when EG is the bore fluid. The NMP:water mixture produces fibers with mixed sponge-like and finger-like structure with large pores in the inner and outer layers; and hence leading to a high water permeance and a high MWCO suitable for separation of large-sized proteins. As compared to NMP:water, using EG as bore fluid provides fibers with a finger-like bilayered structure and sponge-like layers near the surfaces, and hence contributing to the higher water permeance. It also induces small pores for better protein rejection.

In this study, we demonstrate an effective way to modify the lumen of polyetherimide hollow fibers by grafting zwitterionic poly(sulfobetaine) to increase the membrane resistance to fouling. Surface-selective grafting of the protective hydrogel layers has been achieved in a facile two-step process. The first step is the adsorption of a macromolecular redox co-initiator on the lumen-side surface of the membrane, which in the second step, after flushing the lumen of the membrane with a solution comprising monomers and a complementary redox initiator, triggers the in situ cross-linking copolymerization at room temperature. The success of grafting reaction has been verified by the surface elemental analyses using X-ray photoelectron spectroscopy (XPS) and the surface charge evaluation using zeta potential measurements. The hydrophilicity of the grafted porous substrate is improved as indicated by the change of contact angle value from 44° to 30°, due to the hydration layer on the surface produced by the zwitterionic poly(sulfobetaine). Compared to the pristine polyetherimide (PEI) substrate, the poly(sulfobetaine) grafted substrates exhibit high fouling resistance against bovine serum albumin (BSA) adsorption, E. coli attachment and cell growth on the surface. Fouling minimization in the lumen is important for the use of hollow fibers in different processes. For instance, it is needed to preserve power density of pressure-retarded osmosis (PRO). In high-pressure PRO tests, a control membrane based on PEI with an external polyamide selective layer was seriously fouled by BSA, leading to a high water flux drop of 37%. In comparison, the analogous membrane, whose lumen was modified with poly(sulfobetaine), not only had a less water flux decline but also had better flux recovery, up to 87% after cleaning and hydraulic pressure impulsion. Clearly, grafting PRO hollow fiber membranes with zwitterionic polymeric hydrogels as a protective layer potentially sustains PRO performance for power generation.

Ionic liquids have been considered green solvents for membrane fabrication. However, the high viscosity of their polymer solutions hinders the formation of membranes with strong mechanical properties. In this study, acetone was explored as a co-solvent with the ionic liquid 1-ethyl-3-methylimidazolium acetate ([EMIM]OAc) to dissolve cellulose acetate. The effects of acetone on the thermodynamic and kinetic aspects of the polymer solutions were studied and the physicochemical properties and separation capability of their resultant membranes were analyzed. The Hansen solubility parameters of [EMIM]OAc were measured by the software HSPiP and these data demonstrated that acetone was a suitable co-solvent to increase the solubility of cellulose acetate. The Gibbs free energy of mixing ΔG m was estimated to determine the proper composition of the polymer solution with better solubility. The study of the kinetics of phase separation showed that the demixing rate of the CA polymer solution in acetone and [EMIM]OAc was higher than that for solutions in [EMIM]OAc only. The membranes prepared from the former solution had higher water permeance and better mechanical stability than those prepared from the later solution. Adding acetone as a co-solvent opened the opportunity of fabricating membranes with higher polymer concentrations for higher separation capability and better mechanical properties.

Pervaporation has been regarded as a promising separation technology in separating azeotropic mixtures, solutions with similar boiling points, thermally sensitive compounds, organic–organic mixtures as well as in removing dilute organics from aqueous solutions. As the pervaporation membrane is one of the crucial factors in determining the overall efficiency of the separation process, this article reviews the research and development (R&D) of polymeric pervaporation membranes from the perspective of membrane fabrication procedures and materials.

Novel crosslinked thermally rearranged polybenzoxazole (C-TR-PBO) membranes, which show impressive results for isopropanol dehydration, have been obtained via in-situ thermal conversion of hydroxyl-containing polyimide precursors. The polyimide precursors are synthesized by the polycondensation of three monomers; namely, 4,4′-(hexafluoroisopropylidene) diphthalic anhydride (6FDA), 3,3′-dihydroxybenzidine diamine (HAB) and 3,5-diaminobenzoic acid (DABA). Due to the incorporation of the carboxylic-group containing diamine DABA into an ortho-hydroxypolyimide precursor, the thermally induced crosslinking reaction can be achieved together with the thermal rearrangement process. Consequently, a synergistic effect of high permeability and high selectivity can be realized in one step. The resultant C-TR-PBO membrane exhibits an unambiguous enhancement in permeation flux compared to its polyimide precursor. Moreover, the newly developed C-TR-PBO membrane displays stable isopropanol dehydration performance at 60 °C throughout the continuous 200 h. The promising preliminary results achieved in this study may offer useful insights for the selection of membrane materials for pervaporation and new methods to molecularly design next-generation pervaporation membranes.

Novel hydrophobic Hyflon AD/poly(vinylidene fluoride) (PVDF) membranes were developed and investigated for n-butanol dehydration via pervaporation. The coating protocols for a thin defect-free Hyflon AD selective layer on the PVDF support were optimized. Water and n-butanol transport was measured, analyzing the effect of the operating conditions. The water flux through the newly developed membranes was higher than 150 g/m2·h, with the selectivity for water higher than 99 wt %. The focus was on the use of Hyflon AD as the selective layer for n-butanol dehydration. The membrane application can be extended to other solvents, supporting an effective and simple method for dehydration with hydrophobic membranes.

For the first time, polyvinylidene fluoride (PVDF), because of its high stabilities and easy processability, was employed as the substrate material to fabricate the thin-film composite (TFC) hollow fiber membrane for ethanol dehydration. A surface modification of the PVDF substrate through an alkaline treatment was carried out before interfacial polymerization to conquer its hydrophobic nature. Various characterizations showed that a proper alkaline treatment can effectively enhance the surface hydrophilicity by introducing oxygen-containing functional groups. Different configurations of PVDF substrates were investigated and the most suitable morphology was found to be the dual-layer hollow fiber with more porous inner layer and relative denser outer surface. Silicone rubber coating was also applied to enhance the membrane selectivity. The highest separation performance showed a separation factor of 40 and a flux of 1288 g/m2 h with high long term stabilities. This study may provide important insights in exploring new substrate materials for TFC membranes.

A novel miscible polymer blend of copoly(1,5-naphthalene/3,5-benzoic acid-2,2′-bis(3,4-dicarboxyphenyl)) hexafluoropropanedimide 6FDA-NDA/DABA and its sulfonated polyimide has been investigated as a water-selective layer to develop dual-layer hollow fiber membranes for ethanol dehydration via pervaporation. The resultant fibers display an excellent flux of >3.0 kg/m 2 h. This is possibly ascribed to a good distribution of sulfonic groups in the polymer matrix, the increased hydrophilicity and enlarged d -space induced by sulfonic groups, which are verified by polarized light microscopy (PLM), contact angle measurement, sorption tests and XRD. Three different post-treatment approaches, namely, thermal treatment, PDMS coating and modification with polyhedral oligosilsesquioxane (POSS) were employed to improve the membrane selectivity. Their effects on polymer chain packing, dense skin layer thickness and ethanol dehydration performance have been investigated with the aid of the advanced PALS technique. Thermal treatment can densify the selective layer structure while PDMS coating provides a thin shielding layer to protect the selective layer from feed-induced swelling. More importantly, POSS modification displays as the most effective way to enhance the membrane selectivity due to the anti-swelling property of POSS inorganic nanoparticles, mobility restriction of polymer chains and narrowed d -space in polymer structure. Compared to various membranes in the literature, the newly developed hollow fibers in the present study have superior fluxes of >2.0 kg/m 2 h and good separation factor of >200 for ethanol dehydration. This study may provide useful insights for the exploration of new materials and post-modifications for biofuel separations.

A dual-layer hollow fiber membrane consisting of copoly(1,5-naphthalene/3,5-benzoic acid-2,2′-bis(3,4-dicarboxyphenyl) hexafluoropropanedimide) (6FDA-NDA/DABA)/polyhedral oligomeric silsesquioxane (POSS) as the outer functional layer and polyetherimide (Ultem ® ) as the inner support layer has been developed for ethanol hydration via pervaporation. By using lower dope flow rates and optimizing inner dope concentration, the newly developed hollow fiber membranes have desirable morphology consisting of a porous inner layer with low transport resistance and a macrovoid-free selective layer for a superior separation performance. Doppler broadening energy spectra (DBES) have been employed to analyze the depth profile of morphological evolution and examine the thickness of dense selective layer as a function of spinning conditions. Incorporating a small amount (2 wt%) of POSS into the selective layer increases its free volume size and diffusion selectivity and hence improves the pervaporation performance of the hybrid membranes. The diffusion mechanism of permeate molecules through polymer chains containing POSS nanoparticles was proposed and verified via FTIR spectra, XRD curves, positron annihilation lifetime (PAL) characterization and vapor sorption tests. Compared to other hollow fiber membranes, the newly developed hollow fibers have a superior flux of 1.9 kg/m 2 h and a comparable separation factor of 166 for ethanol dehydration. The work may open up a new perspective for the development of next-generation high-performance dual-layer hollow fiber membranes with a POSS embedded selective layer for biofuel separation.

The state-of-the-art of membranes for reverse osmosis, nanofiltration, and gas separation is shortly reviewed, taking in account the most representative examples currently in application. Emphasis is also done on recent developments of advanced polymeric and organic–inorganic materials for pressure-driven processes. Many of the more recent membranes are not only polymeric but also contain an inorganic phase. Tailoring innovative materials with organic and inorganic phases coexisting in a nanoscale with multifunctionalization is an appealing approach to control at the same time diffusivity and gas solubility. Other advanced materials that are now being considered for membrane development are organic or organic–inorganic self-assemblies, metal-organic frameworks, and different forms of carbon fillers.

A novel polyimide, copoly(1,5- naphthalene/3,5-benzoic acid-2,2′-bis(3,4-dicarboxyphenyl) hexafluoropropanedimide (6FDA-NDA/DABA), has been synthesized and modified via various cross-linking modifications for ethanol dehydration as a pervaporation membrane. Three different cross-linking approaches – thermal, diamino and diol cross-linking modifications – are employed; their effects on membrane morphology and separation performance are investigated with the help of various characterization techniques. Thermal treatment at high temperature (425 °C) facilitates the decarboxylation-induced cross-linking, therefore restricting the membrane swelling, creating a higher d-space among polymer chains, and contributing to high permeation fluxes and comparable separation factors of the resultant membranes for ethanol dehydration. Diamino cross-linking modification changes imide groups in the polyimide into amide groups but post heat-treatment converts them back. However, the interactions among polymer chains are irreversibly changed by the formation of chemical cross-linking and charge transfer complexes, as well as the enhanced hydrophilicity, which bring out the improvement in membrane performance. Diol cross-linking also constrains the membrane swelling and results in a higher d-space by the cross-linking spacer, and therefore leading to a higher flux but a lower separation factor than membranes modified by the above two other methods. This work may provide useful insights for polyimide synthesis and cross-linking modifications for biofuel separation.

Novel mixed matrix membranes made of polyether-block-amide/polyhedral oligosilsesquioxane (Pebax/POSS) have been developed and investigated in this study for ethanol recovery via pervaporation separation. Two types of POSS; namely, octa(3-hydroxy-3-methylbutyldimethylsiloxy) (AL0136) and disilanolisobutyl (SO1440), were incorporated into Pebax membranes. The effects of POSS loading, feed ethanol concentration and feed temperature on pervaporation performance of the newly developed mixed matrix membranes (MMMs) have been studied. The incorporation of POSS nanoparticles improve the pervaporation performance of the hybrid membranes significantly. At 2 wt.% POSS loading, both permeation flux and separation factor of ethanol/water reach maximum values, which are 183.5 g/m 2 h and 4.6 for Pebax/AL0136 and 125.8 g/m 2 h and 4.1 for Pebax/SO1440, respectively. Pebax/AL0136 MMMs give better performance than Pebax/SO1440 MMMs, probably due to its higher affinity towards ethanol. Experimental results show that an increase in feed ethanol concentration results in an increase in flux, but decreases in separation factor and membrane selectivity. Flux increases but permeability decreases with an increase in operating temperature due to the increase in driving forces and the reduction in permeant sorption, respectively. Separation factor and selectivity are also observed to increase with increasing operating temperature. The changes in driving force, cluster formation, membrane swelling and interaction among permeating molecules play essential roles for the observed trends. This work may provide useful insights of mixed matrix membranes, especially those containing POSS for pervaporation recovery applications.

Water and energy have always been crucial for the world's social and economic growth. Their supply and use must be sustainable. This review discusses opportunities for membrane technologies in water and energy sustainability by analyzing their potential applications and current status; providing emerging technologies and scrutinizing research and development challenges for membrane materials in this field.