Nonlinear Flux-Pressure Behavior of Solvent Permeation through a Hydrophobic Nanofiltration Membrane.

Nonpolar solvents have been reported to exhibit a nonlinear flux-pressure behavior in hydrophobic membranes. This study explored the flux-pressure relationship of six nonpolar solvents in a lab-cast hydrophobic poly(dimethylsiloxane) (PDMS) membrane and integrated the permeance behavior in the evaluation of the proposed transport model. The solvents exhibited a nonlinear relationship with the applied pressure, along with the point of permeance transition (1.5-2.5 MPa), identified as the critical pressure corresponding to membrane compaction. Two classical transport models, the pore-flow model and solution-diffusion model, were evaluated for the prediction of permeance. The solution-diffusion model indicated a high correlation with the experimental results before the point of transition (R 2 = 0.97). After the point of transition, the compaction factor (due to membrane compaction after the critical pressure) derived from the permeance characteristics was included, which significantly improved the predictability of the solution-diffusion model (R 2 = 0.91). A nonlinear flux-pressure behavior was also observed in hexane-oil miscella (a two-component system), confirming the existence of a similar phenomenon. The study revealed that a solution-diffusion model with appropriate inclusion of compaction factor could be used as a prediction tool for solvent permeance over a wide range of applied transmembrane pressures (0-4 MPa) in solvent-resistant nanofiltration (SRNF) membranes.

Effect of ozone, lactic acid and combination treatments on the control of microbial and pesticide contaminants of fresh vegetables.

BACKGROUND: Fruit and vegetable consumption has increased due to their tremendous health benefits. However, recent studies have shown that contaminated products may serve as vehicles for foodborne pathogens and harmful chemicals. Therefore, fresh vegetables must be decontaminated before consumption to ensure food safety. RESULTS: In this study, the combined decontamination treatment of lactic acid (2.5 mL L-1 ) and ozone (9 mg L-1 ) for 10 min showed better efficacy in the removal of contaminants from fresh vegetables as compared to individual treatments. The combined treatment resulted in a reduction of 1.5-3.5 log CFU of native mesophilic bacteria per gram and 1.6-2.9 log CFU of artificially inoculated Escherichia coli per gram from tomato, cucumber, carrot and lettuce. The combined treatment also removed spiked pesticides, which represent artificial chemical contamination (28-97% chlorpyrifos and 62-100% λ-cyhalothrin residues), from fresh vegetables. No significant difference (P > 0.05) in various sensory attributes of vegetables was observed between untreated and treated (lactic acid and ozone) vegetables. CONCLUSIONS: The combination treatment provides a novel approach to target two groups of contaminants using a single procedure. The combination treatment can be used as an alternative to currently used decontamination techniques for the supply of safe vegetables to consumers. © 2020 Society of Chemical Industry.

Encapsulation of ß-amylase in water-oil-water enzyme emulsion liquid membrane (EELM) bioreactor for enzymatic conversion of starch to maltose.

The ß-amylase was encapsulated in emulsion liquid membrane (ELM), which acted as a reactor for conversion of starch to maltose. The membrane phase was consisted of surfactant (span 80), stabilizer (polystyrene), carrier for maltose transport (methyl cholate) and solvent (xylene). The substrate starch in feed phase entered into the internal phase by the process of diffusion and hydrolyzed to maltose by encapsulated ß-amylase. Methyl cholate present in the membrane acts as a carrier for the product maltose, which helps in transport of maltose to feed phase from internal aqueous phase. The residual activity of ß-amylase after the five-reaction cycle was found to decrease to ∼70%, which indicated possibility to recycle the components of the emulsion and enzyme. The pH and temperature of the encapsulated enzyme were found to be optimum at 5.5 and 60 °C, respectively. The novelty of the present work lies in the development of Enzyme Emulsion Liquid Membranes (EELM) bioreactor for the hydrolysis of starch into maltose mediated by encapsulated ß-amylase. The attempt has been made for the first time for the successful encapsulation of ß-amylase into EELM. The best results gave the highest residual enzyme activity (94.1%) and maltose production (29.13 mg/mL).

Selective extraction of lipase and amylase from enzyme mixture by employing liquid emulsion membrane.

This work deals with the extraction of lipase and amylase from enzyme mixture by employing liquid emulsion membranes (LEM). The electrostatic interaction between enzymes and reverse micellar surfactant polar head group plays an important role for selective extraction of two different enzymes having different isoelectric points. The optimized conditions for lipase extraction (pH 7.0) resulted in the purification fold and activity recovery of 5.43 fold and 89.53%, respectively, whereas, in case of amylase (pH 9.0) the purification fold and activity recovery were 6.58 and 94.32%, respectively. The results were compared with the control sample (containing individual enzymes) and mixture of enzymes lipase and amylase and it was shown that for optimum conditions the activity recovery and purification fold was higher for the individual enzymes as compared to their mixture. Downstream processing involving LEM was shown to be a feasible method for selective extraction of enzymes. © 2018 American Institute of Chemical Engineers Biotechnol. Prog., 34:721-729, 2018.

Downstream processing of lactoperoxidase from milk whey by involving liquid emulsion membrane.

The current work deals with downstream processing of lactoperoxidase using liquid emulsion membrane from the bovine milk whey, which is a by-product from dairy industry. It is an alternate separation technique that can be used for the selective extraction of lactoperoxidase. The extraction of lactoperoxidase in liquid emulsion membrane takes place due to the electrostatic interaction between the enzyme and polar head group of reverse micellar surfactant. The optimum conditions resulted in 2.86 factor purity and activity recovery of 75.21%. Downstream processing involving liquid emulsion membrane is a potential technique for the extraction of lactoperoxidase from bovine whey.

ß-Cyclodextrin capped graphene-magnetite nanocomposite for selective adsorption of Bisphenol-A.

Beta-cyclodextrin capped Graphene-magnetite (G-Fe3O4-BCD) nanocomposite was synthesized by ethylenediamine conjugation and used as an adsorbent for selective removal of Bisphenol-A (BPA) in water. Characterization of nanocomposite revealed BCD conjugated to Fe3O4 nanoparticles (30-40nm) embedded on graphene. Adsorption process followed Langmuir model and pseudo second order kinetics with an adsorption capacity of 59.6mg/g. It was found to be highly favourable physisorption and endothermic process as indicated by ΔG° (-3.36kJ/mol) and ΔH° (2.08kJ/mol) values at ambient temperatures. The nanocomposite was highly specific towards BPA compared to its analogs, largely driven by host-guest interaction between BCD and BPA. Nanocomposite had a high magnetization of 97emu/g with superparamagnetic property at room temperature which helps in faster separation using an external magnetic field. Nanocomposite can be regenerated with methanol and can be reused without much loss in adsorption efficiency (<10%) after 6 cycles. It has huge potential and application in selective adsorption of target molecules.

Ultrasound assisted forward osmosis concentration of fruit juice and natural colorant.

The present study deals with the effect of higher and lower molecular weight compounds present in the feed on concentration polarization during forward osmosis concentration and its mitigation by the application of ultrasound. The effects of ultrasound on transmembrane water flux at different forward osmosis membrane orientations and different model feed solutions consisting of sucrose and pectin have also been evaluated. The feed containing sucrose and pectin subjected towards active layer of the membrane was found to be the most suitable orientation. The application of ultrasound (30kHz) significantly reduced the concentration polarization when the feed contains sucrose concentration up to 5%. Whereas, in case of feed containing 0.5% pectin, the ultrasound was not found to be effective in dislodging the gel layer formation resulting in severe external concentration polarization on the membrane surface. In comparison to the ordinary forward osmosis process, the ultrasound-assisted forward osmosis process resulted in higher water fluxes in case of sweet lime juice as well as rose extract containing anthocyanin. The degradation of rose anthocyanin due to ultrasound was found to be 1.82%. Application of ultrasound was found to be an effective way in mitigating concentration polarization on the forward osmosis membrane resulting in increased flux.

Ways and Means for the Infusion of Bioactive Constituents in Solid Foods.

The development and consumption of functional food, or foods that promote health not merely basic nutrition, is on rise. In recent years, industrial and consumer interests have focused on developing foods supplemented with bioactive constituents that provide greater physiological benefits. The direct addition of these components to liquid or fabricated solid foods has led to a wide range of new products appearing on the market. Osmotic dehydration, an operation in which food stuff is soaked in solution of low water activity, has been reported as a suitable technology for formulating new products because of the twofold effect that it has on food where it partially removes water and impregnates the food pieces (solid food matrix) with solutes from the osmotic solution. The article focuses on the impregnation of bioactive constituents having added advantage to human health such as antioxidants, minerals, vitamins, and probiotics. The infusion of enzymes and aroma also has been discussed. Application of ultrasound, vacuum, high pressure, and/or atmospheric impregnation techniques appears to be the feasible technologies for impregnation of solid food matrix for the incorporation of bioactive ingredients.

Opportunities and Challenges in Application of Forward Osmosis in Food Processing.

Food processing and preservation technologies must maintain the fresh-like characteristics of food while providing an acceptable and convenient shelf life as well as assuring safety and nutritional value. Besides, the consumers' demand for the highest quality convenience foods in terms of natural flavor and taste, free from additives and preservatives necessitated the development of a number of membrane-based non-thermal approaches to the concentration of liquid foods, of which forward osmosis has proven to be the most valuable one. A series of recent publications in scientific journals have demonstrated novel and diverse uses of this technology for food processing, desalination, pharmaceuticals as well as for power generation. Its novel features, which include the concentration of liquid foods at ambient temperature and pressure without significant fouling of membrane, made the technology commercially attractive. This review aims to identify the opportunities and challenges associated with this technology. At the same time, it presents a comprehensive account of recent advances in forward osmosis technology as related to the major issues of concern in its rapidly growing applications in food processing such as concentration of fruit and vegetable juices (grape, pineapple, red raspberry, orange, and tomato juice and red radish juice) and natural food colorants (anthocyanin and betalains extracts). Several vibrant and vital issues such as recent developments in the forward osmosis membrane and concentration polarization aspects have been also addressed. The asymmetric membrane used for forward osmosis poses newer challenges to account both external and internal concentration polarization leading to significant reduction in flux. The recent advances and developments in forward osmosis membrane processes, mechanism of water transport, characteristics of draw solution and membranes as well as applications of forward osmosis in food processing have been discussed.

Mixed reverse micelles facilitated downstream processing of lipase involving water-oil-water liquid emulsion membrane.

Our earlier work for the first time demonstrated that liquid emulsion membrane (LEM) containing reverse micelles could be successfully used for the downstream processing of lipase from Aspergillus niger. In the present work, we have attempted to increase the extraction and purification fold of lipase by using mixed reverse micelles (MRM) consisting of cationic and nonionic surfactants in LEM. It was basically prepared by addition of the internal aqueous phase solution to the organic phase followed by the redispersion of the emulsion in the feed phase containing enzyme, which resulted in globules of water-oil-water (WOW) emulsion for the extraction of lipase. The optimum conditions for maximum lipase recovery (100%) and purification fold (17.0-fold) were CTAB concentration 0.075 M, Tween 80 concentration 0.012 M, at stirring speed of 500 rpm, contact time 15 min, internal aqueous phase pH 7, feed pH 9, KCl concentration 1 M, NaCl concentration 0.1 M, and ratio of membrane emulsion to feed volume 1:1. Incorporation of the nonionic surfactant (e.g., Tween 80) resulted in remarkable improvement in the purification fold (3.1-17.0) of the lipase. LEM containing a mixture of nonionic and cationic surfactants can be successfully used for the enhancement in the activity recovery and purification fold during downstream processing of enzymes/proteins.

Effect of pretreatments on extraction of pigment from marigold flower.

Marigold flower (Tagetes erecta L) is one of the richest sources of xanthophylls. An enzymatic pretreatment method was developed for improved extraction of pigments from marigold flowers. Pretreatment with enzyme solution increased the diffusion coefficient from 1.56 x 10(-9) m(2)/s to 4.02 x 10(-9) m(2)/s and mass transfer coefficient from 0.14 h(-1) to 0.36 h(-1) coefficients. At the same time, dry yield, resin yield and pigment yield were also found to increase along with increased retention of colour. Sodium hydroxide or citric acid pretreatments increased the diffusion coefficient during drying, but resulted in lower dry yield due to loss of soluble compounds whereas, pigment yield was higher as compared to control. The enzyme treated and air dried sample, stored at 4 °C was found to be the most stable, as indicated by a low (0.0006 day(-1)) degradation constant. Pretreatment of marigold flowers with an aqueous enzyme solution (0.2%) results in improved resin, pigment yield and retention of pigment during storage. Pretreatment of marigold flowers with sodium hydroxide citric acid followed by hydraulic pressing resulted in a significant reduction of water and also indicated improved dry yield, resin yield and pigment yield as compared to control sample.

Degradation of isoprothiolane by a defined microbial consortium using response surface methodology.

A defined microbial consortium was developed for the degradation of isoprothiolane. Isoprothiolane-biodegradation parameters were optimized using Response Surface Methodology (RSM). Three variables chosen for the study were inoculum concentration (50-1500 microg protein ml(-1)), temperature (25-35 degrees C) and pH (4-8) each at levels -1.682, -1, 0, 1 and 1.682. Incubation time of 72 hr was kept constant. Degradation of different concentrations of isoprothiolane was studied. The optimized conditions obtained were, inoculum concentration of 50 microg protein ml(-1) at 30 degrees C and pH between 4-8. The maximum predicted percentage degradation of 100, 100, 100, 100 and 95.5 was obtained respectively for 5, 10, 20, 30 and 50 ppm of initial isoprothiolane concentrations at different pH levels 7.7, 6.8, 6.2, 4.7 and 4.6. Validation of the model indicated that experimental values were found to be in agreement with the predicted one.

Reverse micelles-mediated transport of lipase in liquid emulsion membrane for downstream processing.

This work deals with the downstream processing of lipase (EC 3.1.1.3, from Aspergillus niger) using liquid emulsion membrane (LEM) containing reverse micelles for the first time. The membrane phase consisted of surfactants [cetyltrimethylammonium bromide (CTAB) and Span 80] and cosolvents (isooctane and paraffin light oil). The various process parameters for the extraction of lipase from aqueous feed were optimized to maximize activity recovery and purification fold. The mechanism of lipase transport through LEM consisted of three steps namely solubilization of lipase in reverse micelles, transportation of reverse micelles loaded with lipase through the liquid membrane, and release of the lipase into internal aqueous phase. The results showed that the optimum conditions for activity recovery (78.6%) and purification (3.14-fold) were feed phase ionic strength 0.10 M NaCl and pH 9.0, surfactants concentration (Span 80 0.18 M and CTAB 0.1 M), volume ratio of organic phase to internal aqueous phase 0.9, ratio of membrane emulsion to feed volume 1.0, internal aqueous phase concentration 1.0 M KCl and pH 7.0, stirring speed 450 rpm, and contact time 15 min. This work indicated the feasibility of LEM for the downstream processing of lipase.

Recent trends and developments in infrared heating in food processing.

Fruit processing and preservation technologies must keep fresh-like characteristics while providing an acceptable and convenient shelf life as well as assuring safety and nutritional value. Processing technologies include a wide range of methodologies to inactivate microorganisms, improve quality and stability, and preserve and minimize changes of fruit fresh-like characteristics. Infrared (IR) heating offers many advantages over conventional heating under similar conditions, which include reduced heating time, uniform heating, reduced quality losses, versatile, simple and compact equipment, and significant energy saving. The integration of IR with other matured processing operations such as blanching, dehydration, freeze-dehydration, thawing, roasting, baking, cooking has been shown to open up new processing options. Combinations of IR heating with microwave heating and other common conductive and convective modes of heating have been gaining momentum because of increased energy throughput. A number of publications and patents have demonstrated novel and diverse uses of this technology. This review aims at identifying the opportunities and challenges associated with this technology. The effect of IR on food quality attributes is also discussed. The types of equipment commonly used for IR processing have also been summarized.

Development of immobilized biophotonic beads consisting of Photobacterium leiognathi for the detection of heavy metals and pesticide.

The present communication deals with construction of immobilized robust biophotonic bead using P. leiognathi, a marine luminescent bacterium for their possible application in monitoring of environmental toxicants. Immobilization efficiency of agar, carrageenan and sodium alginate was evaluated separately in terms of luminescence response and was recorded as 30.3, 77.4 or 99.5%, respectively. Under optimized storage conditions, the luminescent response of P. leiognathi in the immobilized state was studied over a period of 30 days. These biophotonic beads were further used as a rapid and reliable optical biosensing tool for the detection of heavy metals [Hg(II), As(V) or Cd(II)] and pesticide [2,4-dichlorophenoxyacetic acid (2,4-D)] in water systems. The concentration range for the detection of Hg(II), As(V), Cd(II) and 2,4-D was 2-32ppm, 4-128ppm, 16-512ppm and 100-600ppm, respectively, while corresponding sensitivity threshold was 2.0ppm, 4.0ppm, 16.0ppm and 100ppm. A comparison of inhibition constant (K(d)) (or EC(20)) values indicated that the sensitivity thresholds rank as Hg(II)>As(V)>Cd(II)>2,4-D. Moreover, the time taken for the detection of heavy metals and pesticide was less than 30min. Using the bioluminescence inhibition method, the concentration of heavy metals and pesticide could be predicted.

Opportunities and challenges in application of ultrasound in food processing.

The demand for convenience foods of the highest quality in terms of natural flavor and taste, and which are free from additives and preservatives, has spurred the need for the development of a number of non-thermal approaches to food processing, of which ultrasound technology has proven to be very valuable. Increasing number of recent publications have demonstrated the potential of this technology in food processing. A combination of ultrasound with pressure and/or heat is a promising alternative for the rapid inactivation of microorganisms and enzymes. Therefore, novel techniques like thermosonication, manosonication, and manothermosonication may be a more relevant energy-efficient processing alternative for the food industry in times to come. This review aims at identifying the opportunities and challenges associated with this technology. In addition to discussing the effects of ultrasound on foods, this review covers various areas that have been identified as having great potential for future development. It has been realized that ultrasound has much to offer to the food industry such as inactivation of microorganisms and enzymes, crystallization, drying, degassing, extraction, filtration, homogenization, meat tenderization, oxidation, sterilization, etc., including efficiency enhancement of various operations and online detection of contaminants in foods. Selected practical examples in the food industry have been presented and discussed. A brief account of the challenges in adopting this technology for industrial development has also been included.

Statistical optimization of medium composition for bacterial cellulose production by Gluconacetobacter hansenii UAC09 using coffee cherry husk extract--an agro-industry waste.

During the production of grape wine, the formation of thick leathery pellicle/bacterial cellulose (BC) at the airliquid interface was due to the bacterium, which was isolated and identified as Gluconacetobacter hansenii UAC09. Cultural conditions for bacterial cellulose production from G. hansenii UAC09 were optimized by central composite rotatable experimental design. To economize the BC production, coffee cherry husk (CCH) extract and corn steep liquor (CSL) were used as less expensive sources of carbon and nitrogen, respectively. CCH and CSL are byproducts from the coffee processing and starch processing industry, respectively. The interactions between pH (4.5- 8.5), CSL (2-10%), alcohol (0.5-2%), acetic acid (0.5- 2%), and water dilution rate to CCH ratio (1:1 to 1:5) were studied using response surface methodology. The optimum conditions for maximum BC production were pH (6.64), CSL (10%), alcohol (0.5%), acetic acid (1.13%), and water to CCH ratio (1:1). After 2 weeks of fermentation, the amount of BC produced was 6.24 g/l. This yield was comparable to the predicted value of 6.09 g/l. This is the first report on the optimization of the fermentation medium by RSM using CCH extract as the carbon source for BC production by G. hansenii UAC09.

Integrated downstream processing of lactoperoxidase from milk whey involving aqueous two-phase extraction and ultrasound-assisted ultrafiltration.

The present work involves the adoption of an integrated approach for the purification of lactoperoxidase from milk whey by coupling aqueous two-phase extraction (ATPE) with ultrasound-assisted ultrafiltration. The effect of system parameters of ATPE such as type of phase system, polyethylene glycol (PEG) molecular mass, system pH, tie line length and phase volume ratio was evaluated so as to obtain differential partitioning of contaminant proteins and lactoperoxidase in top and bottom phases, respectively. PEG 6000-potassium phosphate system was found to be suitable for the maximum activity recovery of lactoperoxidase 150.70% leading to 2.31-fold purity. Further, concentration and purification of enzyme was attempted using ultrafiltration. The activity recovery and purification factor achieved after ultrafiltration were 149.85% and 3.53-fold, respectively. To optimise productivity and cost-effectiveness of integrated process, influence of ultrasound for the enhancement of permeate flux during ultrafiltration was also investigated. Intermittent use of ultrasound along with stirring (2 min acoustic and 2 min stirring) resulted in increased permeate flux from 0.94 to 2.18 l/m(2) h in comparison to the ultrafiltration without ultrasound. The use of ultrasound during ultrafiltration resulted in increase in flux, but there was no significant change in activity recovery and purification factor. The integrated approach involving ATPE and ultrafiltration may prove to be a feasible method for the downstream processing of lactoperoxidase from milk whey.

Single step purification of lactoperoxidase from whey involving reverse micelles-assisted extraction and its comparison with reverse micellar extraction.

The extraction of lactoperoxidase (EC 1.11.1.7) from whey was studied using single step reverse micelles-assisted extraction and compared with reverse micellar extraction. The reverse micelles-assisted extraction resulted in extraction of contaminating proteins and recovery of lactoperoxidase in the aqueous phase leading to its purification. Reverse micellar extraction at the optimized condition after forward and backward steps resulted in activity recovery of lactoperoxidase and purification factor of the order of 86.60% and 3.25-fold, respectively. Whereas reverse micelles-assisted extraction resulted in higher activity recovery of lactoperoxidase (127.35%) and purification factor (3.39-fold). The sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) profiles also evidenced that higher purification was obtained in reverse micelles-assisted extraction as compared of reverse micellar extracted lactoperoxidase.

A simple kinetic model for growth and biosynthesis of polyhydroxyalkanoate in Bacillus flexus.

Polyhydroxyalkanoate (PHA), which is produced by several bacteria, is a biodegradable polymer that has many industrial and medical applications. This study deals with development of a simple kinetic model and modification of the logistic equation that can provide an adequate description of PHA formation process by Bacillus flexus. The parameters studied were kinetics of microbial growth, substrate consumption, and product formation. The microbial growth was described by simplification of Monod's model. A simplified Luedeking-Piret type model could be employed to represent the product kinetics. The kinetic constants were evaluated on the basis of non-linear regression and the differential equations were solved using Runge-Kutta algorithm and MATLAB software. A good agreement was found between the experimental and predicted values, which indicated that the model differential equations could describe the PHA formation and fermentation process. In this study, a modification of the logistic equation has also been attempted for describing the growth of B. flexus.