Pore Diameter Of Gas Distributor Research Articles

Improvement of nisin production by using the integration strategy of co-cultivation fermentation, foam fractionation and pervaporation

In this work, an integrated strategy of fermentation and separation was developed to improve nisin production. During fermentation, the acidification of fermentation liquid would hinder the synthesis and maturation of nisin inside strain cells. First, Saccharomyces cerevisiae (S. cerevisiae) was co-cultivated with Lactococcus lactis subsp. lactis (L. lactis) to overcome above obstacle. Experimental results indicated that lactose could be used as the substrate carbon source of co-cultivation fermentation. When inoculation ratio of L. lactis and S. cerevisiae was 102:1, nisin titer and ethanol concentration in the fermentation liquid were 3436.3 ± 171.8 IU/mL and 5.9 ± 0.2 mg/mL, respectively. Subsequently, glucose (500 g/L) was supplied into the culture at 24 h for further increasing nisin yield through the quorum sensing of microorganisms. Foam fractionation was used to recover nisin from fermentation liquid. Under the conditions of volumetric air flow rate 40 mL/min, pore diameter of gas distributor 180 μm and initial coupling time of fermentation and foam fractionation after sugar supplementation 9 h, enrichment ratio and recovery percentage of nisin reached 5.8 ± 0.2 and 63.1 ± 2.8%, respectively. Through integrating pervaporation after sugar supplementation for 9 h, permeate concentration and recovery percentage of bioethanol were 367.2 ± 16.5 mg/mL and 76.2 ± 3.4%, respectively. The total nisin titer was 4593.2 ± 206.6 IU/mL.

Foam fractionation for the separation of SDBS from its aqueous solution: Process optimization and property test

Foam fractionation is an adsorption bubble separation technique allowing recovery and immediate reuse of surfactants. This work was aimed at investigating the variations in recovery efficiency and physicochemical property of sodium dodecyl benzene sulfonate (SDBS) through multiple foam fractionation operation. First, a suitable SDBS concentration of 0.05 g/L was determined for preparing feeding solution. Subsequently, effects of volumetric air flow rate, height ratio of liquid phase and foam phase, and pore diameter of gas distributor on recovery efficiency of SDBS were investigated, respectively. Response surface methodology (RSM) was used to optimize the operating conditions of foam fractionation for separating SDBS. Under the conditions of volumetric air flow rate 80 mL/min, height ratio of liquid phase and foam phase 1:2, and pore diameter of gas distributor 0.180 mm, enrichment ratio and recovery percentage of SDBS were 134.83 ± 6.74 and 63.43 ± 3.17%, respectively. In repetitive separation experiments, the maximum separation number of recovered SDBS by foam fractionation was 3. Experimental results of surface activity and foam properties of recovered SDBS solution suggested that the interfacial adsorption and desorption processes had induced the structural transition and irreversible aggregation of SDBS molecules after multiple foam fractionation operation.

Effective recovery of casein from its aqueous solution by ultrasonic treatment assisted foam fractionation: Inhibiting molecular aggregation

In this work, a novel technology of ultrasonic treatment assisted foam fractionation was developed for the effective recovery of casein from its aqueous solution. Experimental results indicated that ultrasound wave could be used to significantly inhibit the aggregation of casein molecules through decreasing particle size and strengthening interfacial adsorption. At an ultrasonic power of 600 W, the excess surface of casein in foam fractionation with ultrasonic treatment was increased by 46% compared to that without ultrasonic treatment. Under the suitable operation conditions of temperature 25 °C, pH 6.0, casein concentration 0.20 g/L, pore diameter of gas distributor 180 μm, liquid height 300 mm, feed feeding rate 2 mL/min, volumetric air flow rate 150 mL/min, ultrasonic power 600 W and ultrasonic treatment time 2 min, the enrichment ratio and recovery percentage of casein were 7.3 ± 0.36 and 90.2 ± 4.51%, respectively. SEM and AFM analysis showed that ultrasonic treatment could not only inhibit the self-aggregation of casein molecules in the solution, but also weaken the aggregation induced by the interfacial adsorption during foam fractionation. Subunits composition analysis revealed that ultrasonic treatment in foam fractionation had no effect on the structural integrity of casein molecules, but it could change the loose degree of the molecular structure.

Modified multi-walled carbon nanotubes assisted foam fractionation for effective removal of acid orange 7 from the dyestuff wastewater

In this study, multi-walled carbon nanotubes (MWCNTs) had been used to strengthen the removal of acid orange 7 (AO7) from the dyestuff wastewater by using foam fractionation. First, the surface modification of MWCNTs was performed by introducing hypochlorite groups (-OCl). The modified MWCNTs were characterized by using SEM, XRD, FTIR and Raman spectroscopy. Subsequently, the potential of modified MWCNTs as a novel collector for AO7 adsorption was examined. The adsorption conditions of modified MWCNTs towards AO7 were optimized by using response surface methodology (RSM) with a central composite design (CCD). The adsorption capacity of modified MWCNTs towards AO7 could reach 47.72 ± 0.79 mg·g−1 under the optimum conditions. The kinetics and the equilibrium adsorption data were analyzed by using different kinetic and isotherm models. According to the regression results, adsorption kinetics data were well described by pseudo-second order model, whereas adsorption isotherm data were best represented by Langmuir isotherm model. Finally, foam fractionation was performed with a batch mode. Under the suitable conditions of loading liquid volume 300 mL, modified MWCNTs dosage 180 mg, cetyltrimethylammonium bromide (CTAB) concentration 50 mg·L−1, AO7 concentration 30 mg·L−1, pore diameter of gas distributor 0.125 mm and air flow rate 100 mL·min−1, the removal percentage and enrichment ratio of AO7 were 91.23% and 6.17, respectively. The decolourization ratio of solution after foam fractionation was found to be 98.66%.

Production and separation of pseudomonas aeruginosa rhamnolipids using coupling technology of cyclic fermentation with foam fractionation

Rhamnolipids are widely investigated to control the growth of food pathogenic bacteria as well as repair environmental problems. This work was proposed to in situ recover rhamnolipids from the fermentation medium of Pseudomonas aeruginosa D1 through foam fractionation. The kinetic model of the fermentation process of Pseudomonas aeruginosa was established, solved and tested. The model fitted well with the experimental data. The results showed that the initial addition rhamnolipids concentration of 1.25 g/L had little effect on the growth of bacteria, but could significantly affect the synthesis of rhamnolipids. Under the suitable conditions of volumetric air flow rate 60 mL/min, loading liquid volume 100 mL, pore diameter of gas distributor 160 μm, the enrichment ratio and the recovery percentage of rhamnolipids reached 4.83 and 75.15%, respectively. Experimental results indicated that the maximum yield of rhamnolipids could be obtained by coupling foam fractionation with fermentation at 42 h, in which the synthesis rate of rhamnolipids was maximal. Moreover, the yield of rhamnolipids per unit volume of fermentation medium was 16.46 g/L, and the yield was 32.63% higher than that of uncoupled operation, and 13.04 and 10.32% higher than those of coupled operation at other fermentation times.

Xanthan gum assisted foam fractionation for the recovery of casein from the dairy wastewater

Casein was the major protein in the milk of mammals and it was massively lost in the discharged wastewater during dairy product manufacture. This work was aimed at recovering casein from the dairy wastewater by using foam fractionation. In order to improve the foam stability, xanthan gum was used as the foam stabilizer based on the association between protein and polysaccharide. The results of the scanning electron microscope (SEM) and fluorescence emission spectrum suggested that casein could be associated with xanthan gum primarily through electrostatic attraction, which was significantly affected by pH. Moreover, the introduction of xanthan gum had a marked impact on the surface tension, foam ability, foam stability, turbidity, zeta potential and average particle size of casein dispersion. Foam fractionation was performed under the suitable operation condition of pH 6.0, loading liquid volume 400 mL, amount ratio of casein and xanthan gum 1:2, volumetric airflow rate 100 mL/min and pore diameter of gas distributor 0.180 mm. The enrichment ratio and the recovery percentage of casein reached as high as 16.81 and 86.51%, respectively. This work is expected to provide a cost-effective method to recover the trace desired material through improving foam stability based on intermolecular forces.Research highlightsFoam fractionation has been proposed to recover casein from dairy wastewater.Xanthan gum has been used to improve the foam stability of casein.The main interaction between casein and xanthan gum was an electrostatic attraction.Xanthan gum contributed to weakening the flowability of interstitial liquid.

Separation of Protein-Binding Anthraquinones from Semen Cassiae Using Two-Stage Foam Fractionation

Anthraquinones are compounds of high medicinal value in many plants. Based on their good protein binding affinity, foam fractionation was attempted to separate them using proteins in the aqueous extract of Semen Cassiae as collectors. Firstly, the interaction between anthraquinones and Semen Cassiae proteins has been analyzed by the Stem–Volmer equation with physcion as a standard. The results show that physcion had good interaction with the proteins via hydrophobic forces. More importantly, the proteins effectively assisted the foam fractionation of several anthraquinones including aurantio-obtusifolin, aloe-emodin, rhein, emodin, chrysophanol, and physcion. On this basis, a two-stage foam fractionation technology was developed for process intensification using a foam fractionation with vertical sieve trays (VSTs). VSTs, initial feed concentration of total anthraquinones, temperature, volumetric air flow rate and pore diameter of gas distributor had significant effects on enrichment ratio and recovery yield of anthraquinones. Under suitable conditions, the enrichment ratio of total anthraquinones reached 47.0 ± 4.5 with a concentration of 939 ± 94 mg/L in the foamate while their total recovery percentage reached more than 47.7%. In addition, foam fractionation also increased the purity and hydroxyl radical scavenging activity of total anthraquinones. The results had significant implications for the separation of anthraquinones from Semen Cassiae.

Effective recovery of trans-resveratrol from the leaching solution of muscat grape pomace by developing a novel technology of foam fractionation

Resveratrol (2,5,4′-trihydroxystilbene) is a naturally occurring phytoalexin produced by some spermatogphytes and it has recently attracted the increasing attention of agronomists and pharmacologists owing to its satisfactory bioactivities. The objective of this work was to develop a cost-effective technology of foam fractionation to recover trans-resveratrol (trans-Res) from the leaching solution of muscat grape pomace on the assistance of molecular imprinting modified SiO2 nanoparticles. First, trans-Res was leached from muscat grape pomace through the method of alkaline extraction. Under the suitable leaching conditions, the leaching yield of trans-Res reached 84.34%. Adsorption experiments were performed for describing the adsorption behavior of trans-Res on the molecular imprinting modified SiO2 nanoparticles. Results indicated that their adsorption could be fairly described by Freundlich model and fitted well with the pseudo-second-order kinetics model. Moreover, the molecular imprinting modified SiO2 nanoparticles could effectively maintain the stability of trans-Res through avoiding the cis-trans photo-isomerization and oxidative degradation. Finally, foam fractionation was carried out for recovering trans-Res from the leaching solution, in which the concentration of trans-Res was as high as 29.09 mg/L. The molecular imprinting modified SiO2 nanoparticles were used as the collector. Under the suitable conditions of loading liquid volume 250 mL, particle size of molecular imprinting modified SiO2 nanoparticles 436.0 nm, sapindus saponin concentration 0.075 g/L, volumetric gas flow rate 100 mL/min and pore diameter of gas distributor 0.180 mm, the enrichment ratio and the recovery percentage of trans-Res reached 13.68 ± 1.03 and 89.73 ± 3.57%, respectively. This work is expected to provide a new technology for selectively recovering non-surface-active materials from the solution with their isomers or analogues, and to facilitate the industrialization of foam fractionation.

Recovery of silk sericin from the filature wastewater by using a novel foam fractionation column

Silk industry was an important mainstay of Asian textile industry. However, a large volume of filature wastewater is produced during the cocoon cooking step and it might lead to severe environment pollution without effective treatment. In fact, the wastewater contained an important and valuable protein, silk sericin. In this work, foam fractionation was purposed to recover silk sericin (SS) from the filature wastewater. A novel column with groined internal component (GIC) was developed for strengthening foam fractionation at room temperature. Compared with the control column, the collected foam from the experimental column possessed of a low liquid holdup because the low gas-liquid weakened the viscous effect caused by the rising velocity of the bubbles, when the rising foam passed through the corner channels creased by GIC. Under the suitable operating conditions of pH 4.0, length of GIC 400 mm, volumetric air flow rate 200 mL/min and pore diameter of gas distributor 180 μm, the enrichment ratio and the recovery percentage of SS reached 6.77 and 80.29%, respectively. This work is expected to provide a cost-effective technique to recover SS from the filature wastewater, and to facilitate the industrialization of foam fractionation in wastewater treatment.

Precipitation of proteins from soybean whey wastewater by successive foaming and defoaming

To remove whey soybean proteins (WSP) from soybean whey wastewater (SWW), a continuous technology of successive foaming and defoaming was developed to precipitate WSP based on the foam fractionation of WSP from SWW. The roles of foaming and elevated temperature in precipitation of WSP were firstly investigated. The results show that foaming played the critical role in the precipitation of WSP, particularly the precipitation of lipoxidase, β-amylase and lectin, and elevating temperature enhanced the foaming-induced precipitation. Based on these results, the technology was optimized by studying the effects of temperature, pore diameter of gas distributor, superficial air flowrate and retention time on the removal yield of WSP. Under the conditions of length of foam column 700 mm, temperature 60.0 °C, pore diameter of gas distributor 120 ± 20 μm, superficial air flowrate 2.55 mm/s and retention time of 5.0 h, a high removal yield of 88.4 ± 3.9% was obtained. A SDS-PAGE analysis of the variation of WSP composition with retention time further confirmed the effective removal of WSP from SWW, and lectin was found to be the only soluble protein in the residual SWW. Compared with batch foam fractionation, the current technology was more effective in separating WSP from SWW.

Foam fractionation for effective recovery of resveratrol from the leaching liquor of Polygonum cuspidatum by using partially ethylated β-cyclodextrin as collector and frother

In this work, foam fractionation has been proposed to recover resveratrol from the leaching liquor of Polygonum cuspidatum. Resveratrol is a natural polyphenol without surface activity. For achieving the adsorption of resveratrol on the gas-liquid interface, a biological surfactant of partially ethylated β-cyclodextrin (partially Eβ-CD) was prepared. First, the inclusion behavior between partially Eβ-CD and resveratrol was investigated. Resveratrol molecular could easily enter into the cavity of partially Eβ-CD from its wide rim due to the possible driving forces of charge transfer and dipole-dipole interactions. The experiments of foam properties suggested that partially Eβ-CD could decrease the surface tension of aqueous solution, thus generating stable foam. By using partially Eβ-CD as collector and frother, foam fractionation was performed. Under the suitable conditions of partially Eβ-CD concentration 0.680 g/L, loading liquid volume 250 mL, volumetric air flow rate 40 mL/min, pore diameter of gas distributor 0.45 mm and pH 4.0, the enrichment ratio and the recovery percentage of resveratrol reached 2.79 and 73.84%, respectively. The concentration of resveratrol in the foamate was as high as 0.050 g/L. This work is expected to provide a new strategy to effectively recover a non-surface-active material from its aqueous solution, and to facilitate the industrialization of foam fractionation.

Effective recovery of casein from its highly diluted solution by using a technology of foam fractionation coupled with isoelectric precipitation

A technology of foam fractionation coupled with isoelectric precipitation was developed for effectively recovering casein from its highly diluted solution without using any surfactants as stabilizers due to its poor surface activity. The results showed that foam stability could be improved by using the pore diameter of gas distributor 125 μm and increasing the liquid phase height to 1750 mm. In the two-stage continuous foam fractionation, the enrichment ratio and the recovery percentage of casein were obtained as high as 12.1 and 92.3%, respectively. Then, the foamate was treated by precipitation and the supernatant could be used as the feed solution of the first stage foam fractionation. By using the coupled technology, the enrichment ratio was further increased to 52.6 and the recovery percentage was 91.7%. The concentration of casein 0.01 g/L and its mass percent 5% were got in the residual solution and the precipitated solution, respectively.

Modified β -CD-Cu ion complex and yam mucilage assisted batch foam fractionation for separating puerarin from Ge-gen ( Radix puerariae )

Abstract At present, the large scale application of batch foam fractionation is still in confrontation with many problems and difficulties, especially for the enrichment of non-surface-active materials. It is difficult to select a suitable surfactant as the collector when a non-surface-active material can only form a stable association with the expensive surfactants or has not any interactions with the commercially available surfactants. The objective of this work was to investigate the feasibility of batch foam fractionation for recovering such a non-surface-active material, puerarin. Yam mucilage, an abundant byproduct from the manufacture of yam starch, was used to generate a stable foam phase based on its good foamability. According to the properties of puerarin and yam mucilage, β -cyclodextrin ( β -CD) was selected as a basic material to establish an association between them. The results of fluorescence sensitization experiments indicated that puerarin could form an equimolar inclusion complex with β -CD and the inclusion constant was 405.8. Subsequently, β -CD was modified by introducing carbon disulfide and copper (Cu) ion. Then, puerarin could be adsorbed on the gas-liquid interface in the form of ternary complex with modified β -CD-Cu ion complex and glycoprotein molecules (see Fig. 7). Batch foam fractionation was carried out by using the crude extracting solution as the initial feeding solution, in which the concentration of puerarin was as high as 4.6 g/L. Under the suitable conditions of temperature 50 °C, pH 6.0, loading volume of feed solution 400 mL, the pore diameter of gas distributor 0.450 mm, additive volume of yam mucilage 30 mL and volumetric air flow rate 100 mL/min, the enrichment ratio and the percent recovery of puerarin were 4.3 and 82.3%, respectively. This strategy could be generalized to the separation of various non-surface-active materials due to the low cost and the diversiform cavity dimension of cyclodextrins.

Separation of SDS from its determined lowest concentration by a two-stage foam separation

ObjectiveThe lowest concentration of sodium dodecyl sulfate (SDS) separated capably from its feed solution using a one-stage foam separation was determined. Both enrichment ratio and recovery percentage of SDS were increased and SDS concentration of the residual solution was decreased at its lowest concentration. Materials methodThe effects of SDS concentration and superficial gas velocity on foaming height and enrichment ratio of SDS were studied in order to determine the lowest SDS concentration in foam separation. A two-stage foam separation technology using only one column was developed to improve the performances at the lowest SDS concentration. ResultsThe results showed that the lowest SDS concentration in foam separation was 50mg/L. In the one-stage foam separation, SDS surface excess increased with increasing the height of the liquid phase and the pore diameter of gas distributor, thus enrichment ratio increased from 1.9 to 7.2 and however, recovery percentage decreased and SDS concentration of the residual solution significantly increased. In the developed two-stage foam separation, enrichment ratio and recovery percentage increased to 28.0 and 94.2%, respectively and at the same time, SDS concentration of the residual solution decreased to 6.0mg/L under the operating conditions of SDS concentration of the feed solution of 50.0mg/L, loading volume of 0.630L and superficial gas velocity of 1.33mm/s.