Enzymatic Membrane Bioreactor Research Articles

High performance removal of chlorophenols from an aqueous solution using an enzymatic membrane bioreactor

Organochlorides and particularly chlorophenols are environmental pollutants that deserve special attention. Enzymatic membrane bioreactors may be alternatives for efficiently removing such hazardous organochlorides from aqueous solutions. We propose here a novel enzymatic membrane bioreactor comprising an ultrafiltration membrane GR81PP, electrospun fibers made of cellulose acetate, and laccase immobilized using an incubation and a fouling approach. Configurations of this biosystem exhibiting the highest catalytic activity were selected for removal of 2-chlorophenol and 4-chlorophenol from aqueous solution in an enzymatic membrane bioreactor under various process conditions. The highest removal of chlorophenols, at 88% and 74% for 2-chlorophenol and 4-chlorophenol, respectively, occurred at pH 5 and 30 °C in the GR81PP/cellulose acetate/laccase biosystem with enzyme immobilized by the fouling method. Furthermore, the GR81PP/cellulose acetate/laccase biosystem with enzyme immobilized by the fouling method exhibited significant reusability and storage stability compared with the biosystem with laccase immobilized by the incubation method. The mechanism of enzyme immobilization is based on pore blocking and cake-layer formation, while the mechanism of chlorophenols removal was identified as a synergistic combination of membrane separation and enzymatic conversion. The importance of the conducted research is due to efficient removal of hazardous organochlorides using a novel enzymatic membrane bioreactor. The study demonstrates the biosystem's high catalytic activity, reusability, and stability, offering a promising solution for environmental pollution control.

Production of Fructo‐Oligosaccharides in Membrane Bioreactor Using Rotating Ceramic Membrane Disc

AbstractFructo‐oligosaccharides (FOS) are often produced via enzymatic conversion in industry. Enzyme membrane bioreactor (EMBR) can enhance the catalytic efficiency by in‐situ product removal. Its major bottleneck is the fouling caused by the deposition of enzyme on membrane surface. An EMBR system with a compact rotating disc device was established for continuous FOS production. This study further investigated the influences of the membrane rotation on the flux control and enzyme activity. The speed of 600 rpm was a good compromise between flux and fouling control, which stabilized the flux at ∼80 L m−2h−1 during the process. Moreover, the rotation led to an increase in the rejection of enzymes by 20 %, compensating the loss of enzyme due to the inhomogeneous distribution of membrane pore size.

Recent Progress in Enzymatic Preparation of Chitooligosaccharides with a Single Degree of Polymerization and Their Potential Applications in the Food Sector.

Chitosan oligosaccharides (COS), derived from chitin, have garnered considerable attention owing to their diverse biological activities and potential applications. Previous investigations into the bioactivity of COS often encountered challenges, primarily stemming from the use of COS mixtures, making it difficult to discern specific effects linked to distinct degrees of polymerization (DP). Recent progress underscores the significant variation in the biological activities of COS corresponding to different DPs, prompting dedicated research towards synthesizing COS with well-defined polymerization. Among the available methods, enzymatic preparation stands out as a viable and environmentally friendly approach for COS synthesis. This article provides a comprehensive overview of emerging strategies for the enzymatic preparation of single COS, encompassing protein engineering, enzymatic membrane bioreactors, and transglycosylation reactions. Furthermore, the bioactivities of single COS, including anti-tumor, antioxidant, antibacterial, anti-inflammatory, and plant defense inducer properties, exhibit close associations with DP values. The potential applications of single COS, such as in functional food, food preservation, and crop planting, are also elucidated.

Coupling horseradish peroxidase based bioreactor with membrane distillation: Elucidating antibiotics degradation and membrane fouling mitigation

The frequent detection of antibiotics in the surface water bodies increases concerns due to their harmful effect on the biota. In this study, the potential of standalone membrane distillation (MD) and horseradish peroxidase (HRP) enzyme assisted MD treatment (MDHRP) was explored for the removal of 13 antibiotics. A standalone MD system achieved 95 to >99 % removal of the antibiotics from feed solution in ultra-pure water. The enzymatic membrane bioreactor, i.e., MDHRP completely retained both the HRP enzyme and antibiotics (>99 %) in the feed tank, and HRP achieved biocatalytic degradation of antibiotics, thus reducing antibiotics concentration in the feed solution. Overall, 16 to >99 % degradation of the antibiotics retained within MDHRP system was achieved by HRP. Antibiotics degradation was greatly affected by the chemical structure and physicochemical properties of the antibiotics. MDHRP treatment resulted in high removal (>70 %) of antibiotics containing either electron-donating groups (e.g., phenolic group) or both electron-donating group/electron-withdrawing groups (e.g., phenolic and amide groups/carboxylic group) in their structures. When secondary-treated effluent (i.e., effluent from a conventional membrane bioreactor) was spiked with antibiotics and used as a feed in MDHRP system, in addition to the antibiotics degradation, HRP reduced the concentration of bulk organic carbon (30 %) and nitrogen (62 %) from feed during continuous operation. This in turn assisted in reducing membrane fouling and improving the membrane flux.

Process Design for the Production of Prebiotic Oligosaccharides in an Enzyme Membrane Bioreactor: Interaction between Enzymatic Reaction and Membrane Filtration

AbstractAppropriately designed and operated enzyme membrane bioreactors (EMBRs) can fully utilize the activity of free, soluble enzymes while maximizing enzyme reusability and simultaneously removing the enzyme‐free product in situ. A filtration model system was applied to determine critical EMBR design factors suitable for continuous enzymatic production of prebiotic fructo‐oligosaccharides. The filtration flux and separation efficiency were investigated in terms of the membrane cutoff rating. In addition, the influence of operational conditions on enzyme activity was also determined.

Combining enzymatic membrane bioreactor and ultraviolet photolysis for enhanced removal of trace organic contaminants: Degradation efficiency and by-products formation

Coupling of membrane distillation with bioreactors containing enzymes such as ‘laccase’ forms an enzymatic membrane bioreactor resulting in complete retention of both trace organic contaminants and enzyme, facilitating simultaneous trace organic contaminants degradation. Integration of enzymatic membrane bioreactor and ultraviolet photolysis may result in further improved degradation of trace organic contaminants in membrane-concentrate. We studied the degradation as well as by-products formation of five selected trace organic contaminants, namely, sulfamethoxazole, diclofenac, bisphenol A, oxybenzone, and carbamazepine by ‘membrane distillation — ultraviolet photolysis’ system and ‘enzymatic membrane bioreactor — ultraviolet photolysis’ system. In the former, the membrane effectively retained the trace organic contaminants and then ultraviolet photolysis of membrane-concentrate resulted in trace organic contaminant degradation in the following order: diclofenac (88 %) > sulfamethoxazole (71 %) > oxybenzone (35 %) > bisphenol A (33 %) > carbamazepine (27 %). By contrast, the enzymatic membrane bioreactor — ultraviolet photolysis system resulted in 100 % degradation of diclofenac, sulfamethoxazole, and bisphenol A and around 70 % degradation of oxybenzone and carbamazepine. This system also resulted in more than 50 % reduction in number of degradation products with 60–70 % lower abundance. Our results indicate that laccase degradation led to products that were more amenable to the post-treatment by ultraviolet photolysis. Overall, it can be concluded that for enzymatic membrane bioreactor — ultraviolet photolysis system, enzymatic pre-treatment not only helped in better degradation of the parent trace organic contaminants but also led to the formation of fewer by-products with lower abundance (i.e., more complete degradation).

Production and purification of fructo-oligosaccharides using an enzyme membrane bioreactor and subsequent fermentation with probiotic Bacillus coagulans

Fructo-oligosaccharides (FOS) are low-calorie sweeteners that can be synthesized by the transfructosylation of sucrose using enzymes known as fructosyltransferases. However, enzymatic conversion is inhibited by the accumulation of glucose as a byproduct, which limits the conversion rate and yield. We therefore developed a semi-continuous production process in an enzyme membrane bioreactor (EMBR) system followed by fermentation with the probiotic bacterium Bacillus coagulans. Filtration experiments were conducted in total recycle mode to evaluate membrane fouling using the resistance-in-series model. We found that fouling was predominantly caused by the accumulation of proteins at the membrane surface, which accounted for 29.6–95.5% of the total filtration resistance depending on the conditions. Using these data, we were able to achieve a stable filtration flux that fulfilled the requirements of the EMBR system by regulating the filtration parameters. The average concentration of total FOS in the products of EMBR reached 270 g·L−1, which was 4.6% higher than the batch process. Subsequently, the crude FOS preparation was treated by fed-batch fermentation with B. coagulans. The monosaccharides in the reaction mix (glucose and fructose) were completely removed, increasing the concentration of FOS to 195.9 g·L−1 and the purity to 96.6%.

Removal of trace organic contaminants by enzymatic membrane bioreactors: Role of membrane retention and biodegradation

Performance of an enzymatic membrane bioreactor (EMBR) equipped with either an ultrafiltration (UF) or a nanofiltration (NF) membrane was explored for the degradation of a set of 29 chemically diverse trace organic contaminants (TrOCs). The NF membrane provided effective retention (90-99%) of TrOCs within the NF-EMBR. On the other hand, partial retention of charged and significantly hydrophobic (log >3) TrOCs was achieved by the UF membrane via charge repulsion and adsorption on the enzyme gel-layer formed on the membrane surface during UF-EMBR operation. Laccase achieved TrOC-specific degradation in both EMBRs. The extent of TrOC degradation was significantly (5 to 65%) better by NF-EMBR as compared to that achieved by UF-EMBR. Addition of a redox-mediator (violuric acid) at concentrations ranging from 10-100 μM improved the degradation of non-phenolic TrOCs, but degradation efficiency reached a plateau when its concentration was increased beyond 25 μM. Although the permeate flux of the UF/NF membranes dropped with time due to membrane fouling caused by enzyme gel-layer and/or concentration polarization, membrane flushing with water was effective in recovering the flux by up to 95%.

An innovative two-step enzymatic membrane bioreactor approach for the continuous production of antioxidative casein hydrolysates with reduced bitterness

Enzymatic batch processes bear some disadvantages, such as the high quantity of enzyme, energy and labor needed and, consequently, high production costs. The aim of this study was the production of a sodium caseinate hydrolysate with improved antioxidative capacity and reduced bitterness in a continuous system to avoid such drawbacks. Therefore, a novel, food-grade, two-step enzymatic membrane bioreactor (EMBR) process was designed in which a functional improved permeate with a 33% increased antioxidativity compared to sodium caseinate was produced with the endopeptidases Sternzym BP 25201. This bitter permeate was subsequently debittered in a second EMBR step with commercial Flavourzyme, which was reduced in its endopeptidase activity. This resulted in a linear production of 7.5 gProduct h−1 of antioxidative (antioxidativity: +39% compared to sodium caseinate), debittered peptides. The influence of the peptidases on each other was excluded by separating the endo- and exopeptidases in two EMBR steps and a product with consistent properties like degree of hydrolysis, antioxidativity and taste was obtained. The process conditions chosen were optimal regarding a stable product formation for three days. Therefore, the process was superior in its productivity, enzyme usage and run time compared to an equivalent batch process.

Fabrication and Optimization of a Lipase Immobilized Enzymatic Membrane Bioreactor based on Polysulfone Gradient-Pore Hollow Fiber Membrane

Enzymatic membrane bioreactors (EMBRs) possess the characteristic of combining catalysis with separation, and therefore have promising application potentials. In order to achieve a high-performance EMBR, membrane property, as well as operating parameters, should give special cause for concerns. In this work, an EMBR based on hollow fiber polysulfone microfiltration membranes with radial gradient pore structure was fabricated and enzyme immobilization was achieved through pressure-driven filtration. Lipase from Candida rugosa was used for immobilization and EMBR performance was studied with the enzymatic hydrolysis of glycerol triacetate as a model reaction. The influences of membrane pore diameter, substrate feed direction as well as operational parameters of operation pressure, substrate concentration, and temperature on the EMBR activity were investigated with the production of hydrolysates kinetically fitted. The complete EMBR system showed the highest activity of 1.07 × 104 U⋅g−1. The results in this work indicate future efforts for improvement in EMBR.

Two phase enzymatic membrane reactor for the production of biodiesel from crude Eruca sativa oil

In the present study, a novel two-phase enzymatic membrane bioreactor (TP-EMR) was developed for the enzymatic biodiesel production from crude Eruca sativa oil. Commercial poly acrylonitrile (PAN) ultrafiltration membrane was examined with a molecular weight cut offs (MWCO) of 30 and 100 kilo Dalton (kDa). Using enzymatic membrane bioreactor with hydrophilic PAN membrane increased the yield of biodiesel production. In this regards, PAN membrane with a MWCO of 100 kDa gave the better results. The inactivation and inhibition effects of methanol and produced glycerol were reduced with the use of membrane bioreactor. It was found that by methanol feeding via aqueous phase, methanol has been penetrated across membrane pores to the organic phase. Afterwards, methanol has reacted with oil at the interface of the membrane at the presence of Candida rugosa lipase (CRL) as a biocatalyst. Produced glycerol, which surrounded the CRL, could be removed from organic phase and conveyed to the aqueous phase to reduce the inhibitory effect of glycerol on the activity of CRL. The yield of about 100% from Eruca sativa oil was achieved in TP-EMR with PAN 100 and organic phase flow rate of 40 ml/min along with 40% initial water content in organic phase.

Impact of simultaneous retention of micropollutants and laccase on micropollutant degradation in enzymatic membrane bioreactor

This study systematically compares the performance of ultrafiltration (UF) and nanofiltration (NF) based enzymatic membrane bioreactors (EMBRs) for the degradation of five micropollutants, namely atrazine, carbamazepine, sulfamethoxazole, diclofenac and oxybenzone to elucidate the impact of effective membrane retention of micropollutants on their degradation. Based on the permeate quality, NF-EMBR achieved 92–99.9% micropollutant removal (i.e., biodegradation + membrane retention), while the removal of these micropollutants by UF-EMBR varied from 20 to 85%. Mass balance analysis revealed that micropollutant degradation was improved by 15–30% in NF-EMBR as compared to UF-EMBR, which could be attributed to the prolonged contact time between laccase and micropollutants following their effective retention by the NF membrane. A small decline in permeate flux was observed during EMBR operation. However, the flux could be recovered by flushing the membrane with permeate.

Special Issue on Wastewater Treatment and Reuse Technologies

Wastewater treatment allows for the safe disposal of municipal and industrial wastewater to protect public health and the ecosystem[...]

Immobilization of Enzymes on a Phospholipid Bionically Modified Polysulfone Gradient-Pore Membrane for the Enhanced Performance of Enzymatic Membrane Bioreactors.

Enzymatic membrane bioreactors (EMBRs), with synergistic catalysis-separation performance, have increasingly been used for practical applications. Generally, the membrane properties, particularly the pore structures and interface interactions, have a significant impact on the catalytic efficiency of the EMBR. Therefore, a biomimetic interface based on a phospholipid assembled onto a polysulfone hollow-fiber membrane with perfect radial gradient pores (RGM-PSF) has been prepared in this work to construct a highly efficient and stable EMBR. On account of the special pore structure of the RGM-PSF with the apertures decreasing gradually from the inner side to the outer side, the enzyme molecules could be evenly distributed on the three-dimensional skeleton of the membrane. In addition, the supported phospholipid layer in the membrane, prepared by physical adsorption, was used for the immobilization of the enzymes, which provides sufficient linkage to prevent the enzymes from leaching but also accommodates as many enzyme molecules as possible to retain high bioactivity. The properties of the EMBR were studied by using lipase from Candida rugosa for the hydrolysis of glycerol triacetate as a model. Energy-dispersive X-ray and circular dichroism spectroscopy were employed to observe the effect of lecithin on the membrane and structure changes in the enzyme, respectively. The operational conditions were investigated to optimize the performance of the EMBR by testing substrate concentrations from 0.05 to 0.25 M, membrane fluxes from 25.5 to 350.0 L·m−2·h−1, and temperatures from 15 to 55 °C. As a result, the obtained EMBR showed a desirable performance with 42% improved enzymatic activity and 78% improved catalytic efficiency relative to the unmodified membrane.

Biocatalytic degradation of pharmaceuticals, personal care products, industrial chemicals, steroid hormones and pesticides in a membrane distillation-enzymatic bioreactor

Laccase-catalyzed degradation of a broad spectrum of trace organic contaminants (TrOCs) by a membrane distillation (MD)-enzymatic membrane bioreactor (EMBR) was investigated. The MD component effectively retained TrOCs (94–99%) in the EMBR, facilitating their continuous biocatalytic degradation. Notably, the extent of TrOC degradation was strongly influenced by their molecular properties. A significant degradation (above 90%) of TrOCs containing strong electron donating functional groups (e.g., hydroxyl and amine groups) was achieved, while a moderate removal was observed for TrOCs containing electron withdrawing functional groups (e.g., amide and halogen groups). Separate addition of two redox-mediators, namely syringaldehyde and violuric acid, further improved TrOC degradation by laccase. However, a mixture of both showed a reduced performance for a few pharmaceuticals such as primidone, carbamazepine and ibuprofen. Mediator addition increased the toxicity of the media in the enzymatic bioreactor, but the membrane permeate (i.e., final effluent) was non-toxic, suggesting an added advantage of coupling MD with EMBR.

Integration of an enzymatic bioreactor with membrane distillation for enhanced biodegradation of trace organic contaminants

A novel membrane distillation – enzymatic membrane bioreactor (MD-EMBR) system was developed for efficient degradation of trace organic contaminants (TrOCs). Degradation of five TrOCs, namely carbamazepine, oxybenzone, diclofenac, atrazine and sulfamethoxazole was examined using two commercially available laccases (from Trametes versicolor and Aspergillus oryzae). The MD system ensured complete retention (>99%) of both enzyme and TrOCs. Of particular interest was that the complete retention of the TrOCs resulted in high TrOC degradation by both laccases. Oxybenzone and diclofenac degradation in the MD-EMBR ranged between 80 and 99%. Compared to previously developed EMBRs, as much as 40% improvement in the removal of resistant non-phenolic TrOCs (e.g., carbamazepine) was observed. Laccase from A. oryzae demonstrated better TrOC degradation and enzymatic stability. With the addition of redox mediators, namely 1-hydroxybenzotriazole (HBT) or violuric acid (VA), TrOC degradation was improved by 10–20%. This is the first demonstration of a laccase-based high retention membrane bioreactor for enhanced biodegradation of TrOCs.

Continuous transformation of chiral pharmaceuticals in enzymatic membrane bioreactors for advanced wastewater treatment.

This study demonstrates continuous enantiomeric inversion and further biotransformation of chiral profens including ibuprofen, naproxen and ketoprofen by an enzymatic membrane bioreactor (EMBR) dosed with laccase. The EMBR showed non-enantioselective transformations, with high and consistent transformation of both (R)- and (S)-ibuprofen (93 ± 6%, n = 10), but lower removals of both enantiomers of naproxen (46 ± 16%, n = 10) and ketoprofen (48 ± 17%, n = 10). Enantiomeric analysis revealed a bidirectional but uneven inversion of the profens, for example 14% inversion of (R)- to (S)- compared to 4% from (S)- to (R)-naproxen. With redox-mediator addition, the enzymatic chiral inversion of both (R)- and (S)-profens remained unchanged, although the overall conversion became enantioselective; except for (S)-naproxen, the addition of redox mediator promoted the degradation of (R)-profens only.

Comparative study on hydrolysis of oils by lipase immobilized biocatalytic PS membranes using biphasic enzyme membrane reactor

In the present study the hydrolysis of olive, palm and castor oil had been carried out to yield valuable free fatty acids by using immobilized Candida rugosa lipase. This study was designed to achieve high yield of lipase immobilization by investigating different factors (applied pressure, time, and lipase concentration) for ultrafiltration process of immobilization. A biphasic enzyme membrane bioreactor was fabricated having aqueous-organic two-phase system with lipase immobilized polysulfone. Effect of operating variables on the performance of this biphasic EMR was investigated with the hydrolysis of olive oil, palm oil and castor oil.It was found that the optimal conditions for highest degree of hydrolysis (%) were temperature 37°C, pH 8.0, at concentration of 0.05M in iso-octane and initial reaction time was 24h. In optimal conditions, degree of hydrolysis for olive oil, palm oil and castor oil was 38.5%, 35.4% and 21.2% respectively. Reusability feature was also studied and only ∼20% decrease in activity was observed after five cycles.

High-performance enzymatic membrane bioreactor based on a radial gradient of pores in a PSF membrane via facile enzyme immobilization

Hollow fiber polysulfone membranes with perfect radial gradient distributed pores were selected as substrates, and subsequently the enzyme-immobilization process was achieved by filtration and crosslinking, to finally construct an enhanced EMBR.

Development of a two separate phase submerged biocatalytic membrane reactor for the production of fatty acids and glycerol from residual vegetable oil streams

Enzymatic membrane bioreactors (MBR) have been studied for very different applications since many years. Submerged MBR has also been successfully used for treatment of wastewater. In the existing submerged configuration, the membrane works as the separation unit operation while the bioconversion is carried out by microorganisms suspended in the tank reactor. In the present work, a novel approach that combines the concept of biocatalytic membranes and submerged modules is proposed for the treatment of biomass. Lipase enzyme from Candida rugosa has been immobilized in polyethersulphone hollow fiber (PES HF) membrane in order to develop a two separate phase biocatalytic submerged membrane reactor in which the membrane works as both catalytic and separation unit. Furthermore, the submerged biocatalytic membrane reactor is intended for production of valuable components from waste biomass, and different physical, chemical and fluid dynamics has been optimized. Response surface methodology (RSM) has been used to model the operating parameters and Box-Behnken method has been applied to maximize the fatty acids production and optimization. At TMP 80 ± 2 kPa, pH 7.40 ± 0.1, temperature 35 ± 0.5 °C with an axial velocity of 0.07 ± 0.01 ms−1 and organic stirring 89.01 rad s−1 the system showed the global examined value within the experimental scope. The proof of principle using fried cooked oils has been performed in later period.