Immobilization of cellulase on a reversibly soluble-insoluble support: properties and application

Enzymatic treatment to improve permeability and quality of cherry tomatoes for production of dried products

BACKGROUND

Cherry tomatoes are nutritious and favored by consumers. Processing them into dried cherry tomatoes can prolong their storage life and improve their flavor. The pretreatment of tomato pericarp is crucial for the subsequent processing. However, the traditional physical and chemical treatments of tomato pericarp generally cause nutrient loss and environmental pollution.

RESULTS

In this study, a novel enzymatic method for cherry tomatoes was performed using mixed enzymes containing cutinase, cellulase and pectinase. Results showed that the pericarp permeability of cherry tomatoes was effectively improved due to enzymatic treatment. Changes in the microscopic structure and composition of the cuticle were revealed. After treatment with different concentrations of enzymes, cherry tomatoes exhibited higher pericarp permeability and sensory quality to varying degrees. The lycopene content and total polyphenol content significantly increased 2.4- and 1.45-fold, respectively. In addition, the satisfactory effect of the six-time reuse of enzymes on cherry tomatoes could still reach the same level as the initial effect, which effectively reduced the cost of production.

CONCLUSIONS

This study revealed for the first time that a mixed enzymatic treatment consisting of cutinase, pectinase and cellulase could effectively degrade the cuticle, enhance the pericarp permeability and improve the quality of cherry tomatoes, with the advantages of being mildly controllable and environmentally friendly, providing a new strategy for the processing of dried cherry tomatoes. © 2023 Society of Chemical Industry.

Cellulase immobilization to enhance enzymatic hydrolysis of lignocellulosic biomass: An all-inclusive review

Cellulase-mediated lignocellulosic biorefinery plays a crucial role in the production of high-value biofuels and chemicals, with enzymatic hydrolysis being an essential component. The advent of cellulase immobilization has revolutionized this process, significantly enhancing the efficiency, stability, and reusability of cellulase enzymes. This review offers a thorough analysis of the fundamental principles underlying immobilization, encompassing various immobilization approaches such as physical adsorption, covalent binding, entrapment, and cross-linking. Furthermore, it explores a diverse range of carrier materials, including inorganic, organic, and hybrid/composite materials. The review also focuses on emerging approaches like multi-enzyme co-immobilization, oriented immobilization, immobilized enzyme microreactors, and enzyme engineering for immobilization. Additionally, it delves into novel carrier technologies like 3D printing carriers, stimuli-responsive carriers, artificial cellulosomes, and biomimetic carriers. Moreover, the review addresses recent obstacles in cellulase immobilization, including molecular-level immobilization mechanism, diffusion limitations, loss of cellulase activity, cellulase leaching, and considerations of cost-effectiveness and scalability. The knowledge derived from this review is anticipated to catalyze the evolution of more efficient and sustainable biocatalytic systems for lignocellulosic biomass conversion, representing the current state-of-the-art in cellulase immobilization techniques.

Advances in extraction and purification of citrus flavonoids

Flavonoids are the representative active substances of citrus with various biological activities and high nutritional value. In order to evaluate and utilize citrus flavonoids, isolation and purification are necessary steps. This manuscript reviewed the research advances in the extraction and purification of citrus flavonoids. The structure classification, the plant and nutritional functions, and the biosynthesis of citrus flavonoids were summarized. The characteristics of citrus flavonoids and the selection of separation strategies were explained. The technical system of extraction and purification of citrus flavonoids was systematically described. Finally, outlook and research directions were proposed.

Overview on immobilization of enzymes on synthetic polymeric nanofibers fabricated by electrospinning

The arrangement and type of support has a significant impact on the efficiency of immobilized enzymes. 1-dimensional fibrous materials can be one of the most desirable supports for enzyme immobilization. This is due to their high surface area to volume ratio, internal porosity, ease of handling, and high mechanical stability, all of which allow a higher enzyme loading, release and finally lead to better catalytic efficiency. Fortunately, the enzymes can reside inside individual nanofibers to remain encapsulated and retain their three-dimensional structure. These properties can protect the enzyme's tolerance against harsh conditions such as pH variations and high temperature, and this can probably enhance the enzyme's stability. This review article will discuss the immobilization of enzymes on synthetic polymers, which are fabricated into nanofibers by electrospinning. This technique is rapidly gaining popularity as one of the most practical ways to fibricate polymer, metal oxide, and composite micro or nanofibers. As a result, there is interest in using nanofibers to immobilize enzymes. Furthermore, present research on electrospun nanofibers for enzyme immobilization is primarily limited to the lab scale and industrial scale is still challanging. The primary future research objectives of this paper is to investigate the use of electrospun nanofibers for enzyme immobilization, which includes increasing yield to transfer biological products into commercial applications.

Glucan Conversion and Membrane Recovery of Biomimetic Cellulosomes During Lignocellulosic Biomass Hydrolysis

Enzyme immobilization has been identified as one way to recycle enzymes and reduce processing costs during enzymatic hydrolysis of lignocellulosic materials. However, most immobilization methods have not been attractive to lignocellulosic processing plants. In this study, cellulase enzymes were attached to a copolymer of glycidyl methacrylate (GMA) and poly(ethylene glycol) methyl ether methacrylate (PEGMA) to make polymer-enzyme conjugates (PECs) and facilitate recovery using a 50-kDa molecular weight cutoff membrane. Glucan conversion during biomass hydrolysis was investigated using new PECs and PECs recovered after an initial hydrolysis stage. Enzyme immobilization on PECs did not reduce effectiveness during the initial hydrolysis. Temperature and pH showed similar effects on free enzymes and PECs. PECs facilitated higher conversion rates than free enzymes at high biomass loadings. Recovered PECs were used to achieve approximately 100% glucan conversion in a subsequent hydrolysis step when supplemented with 40% of the free enzyme used in the first stage. The combination of PECs and membrane recovery has the potential to reduce hydrolysis cost during cellulosic bioprocessing.

Status of the application of exogenous enzyme technology for the development of natural plant resources

Exogenous enzymes are extraneous enzymes that are not intrinsic to the subject. The exogenous enzyme industry has been rapidly developing recently. Successful application of recombinant DNA amplification, high-efficiency expression, and immobilization technology to genetically engineered bacteria provides a rich source of enzymes. Amylase, cellulase, protease, pectinase, glycosidase, tannase, and polyphenol oxidase are among the most widely used such enzymes. Currently, the application of exogenous enzyme technology in the development of natural plant resources mainly focuses on improving the taste and flavor of the product, enriching the active ingredient contents, deriving and transforming the structure of a chosen compound, and enhancing the biological activity and utilization of the functional ingredient. In this review, we discuss the application status of exogenous enzyme technology for the development of natural plant resources using typical natural active ingredients from plant, such as resveratrol, steviosides, catechins, mogrosides, and ginsenosides, as examples, to provide basis for further exploitation and utilization of exogenous enzyme technology.

Enhanced Catalytic Performance of Trichoderma reesei Cellulase Immobilized on Magnetic Hierarchical Porous Carbon Nanoparticles

Cellulase from Trichoderma reesei was immobilized by covalent or non-covalent binding onto magnetic hierarchical porous carbon (MHPC) nanomaterials. The immobilization yield and the enzyme activity were higher when covalent immobilization approach was followed. The covalent immobilization approach leads to higher immobilization yield (up to 96%) and enzyme activity (up to 1.35 U mg^-1) compared to the non-covalent cellulase binding. The overall results showed that the thermal, storage and operational stability of the immobilized cellulase was considerably improved compared to the free enzyme. The immobilized cellulose catalyzed the hydrolysis of microcrystalline cellulose up to 6 consecutive successive reaction cycles, with a total operation time of 144 h at 50 °C. The half-life time of the immobilized enzyme in deep eutectic solvents-based media was up to threefold higher compared to the soluble enzyme. The increased pH and temperature tolerance of the immobilized cellulase, as well as the increased operational stability in aqueous and deep eutectic solvents-based media indicate that the use of MHPCs as immobilization nanosupport could expand the catalytic performance of cellulolytic enzymes in various reaction conditions.

Functionalized kaolin as support for endoglucanase immobilization

Endoglucanases are an enzyme of cellulases complex that has a great potential for many technological applications. One of the issues of its use concerns the recovery and reuse of this enzyme. Thus, in this study, the use of a surface-modified kaolin was evaluated to immobilize endoglucanase and evaluate the enzyme activity for its reuse. Kaolin was surface modified with 3-aminopropyltriethoxysilane (APTES) and glutaraldehyde (GA). In addition, the properties of the immobilized enzyme were investigated and compared with those of the free enzyme. Results showed that the optimal pH value of endoglucanase was not affected by the immobilization process but showed a broader range of optimal temperature compared to free enzyme. Immobilization on kaolin allowed fast and easy cellulase recovery with a loss of enzyme activity of only 20% after eight cycles of use. These results indicate that kaolin is a promising substitute to the currently synthetic supports studied for cellulases immobilization with the advantage of being abundant in nature, resistant to microbial attack, chemically and mechanically stable.

Flexible Peptide Linkers Enhance the Antimicrobial Activity of Surface-Immobilized Bacteriolytic Enzymes

Chemical linkers are frequently used in enzyme immobilization to improve enzyme flexibility and activity, whereas peptide linkers, although ubiquitous in protein engineering, are much less explored in enzyme immobilization. Here, we report peptide-linker-assisted noncovalent immobilization of the bacteriolytic enzyme lysostaphin (Lst) to generate anti- Staphylococcus aureus surfaces. Lst was immobilized through affinity tags onto a silica surface (glass slides) and nickel nitrilotriacetic acid (NiNTA) agarose beads via silica-binding peptides (SiBPs) or a hexahistidine tag (His-tag) fused at the C-terminus of Lst, respectively. By inserting specific peptide linkers upstream of the SiBP or His-tag, the immobilized enzymes killed >99.5% of S. aureus ATCC 6538 cells (10⁸ CFU/mL) within 3 h in buffer and could be reused multiple times without significant loss of activity. In contrast, immobilized Lst without a peptide linker was less active/stable. Molecular modeling of Lst-linker-affinity tag constructs illustrated that the presence of the peptide linkers enhanced the molecular flexibility of the proximal Lst binding domain, which interacts with the bacterial substrate, and such increased flexibility correlated with increased antimicrobial activity. We further show that Lst immobilized onto NiNTA beads retained the ability to kill ∼99% of a 10⁸ CFU/mL microbial challenge even in the presence of 1% of a commercial anionic surfactant, C12-14 alcohol EO 3:1 sodium sulfate, when the Lst construct contained a decapeptide linker containing glycine, serine, and alanine residues. This linker-assisted immobilization strategy could be extended to an unrelated lytic enzyme, the endolysin PlyPH, to target Bacillus anthracis Sterne cells either in buffer or in the presence of anionic surfactants. Our approach, therefore, provides a facile route to the use of antimicrobial enzymes on surfaces.

Recovery and reuse of immobilized α-amylase during desizing of cotton fabric

Purpose

Enzymatic desizing using α-amylase is the conventional and eco-friendly method of removing starch based size. Conventionally, enzymes are drained after completion of process; being catalysts, they retain their activity after reaction and need to be reused. Immobilization allows the recovery of enzymes to use them as realistic biocatalyst. This study aims to recover and reuse of α-amylase for desizing of cotton via immobilization.

Design/methodology/approach

This paper investigates the application of α-amylase immobilized on Chitosan and Eudragit S-100 for cotton fabric desizing. A commercial α-amylase was immobilized on reversibly soluble-insoluble polymers to work out with inherent problems of heterogeneous reaction media. The immobilization process was optimized for maximum conjugate activity, and immobilized amylases were applied for grey cotton fabric desizing.

Findings

The desizing performance of immobilized amylases was evaluated in terms of starch removal and was compared to free enzyme. The immobilized amylases showed adequate desizing efficiency up to four cycles of use and were recovered easily at the end of each cycle. The amylase immobilized on Eudragit is more efficient for a particular concentration than chitosan.

Practical implications

Immobilization associates with insolubility and increased size of enzymes which lead to poor interactions and limited diffusion especially in textiles where enzymes have to act on macromolecular substrates (heterogeneous media). The selection of support materials plays a significant role in this constraint.

Originality/value

The commercial α-amylase was covalently immobilized on smart polymers for cotton fabric desizing. The target was to achieve immobilized amylase with maximum conjugate activity and limited constraints. The reversibly soluble-insoluble polymers support provide easy recovery with efficient desizing results in heterogeneous reaction media.

Covalent Immobilization of Cellulase Using Magnetic Poly(ionic liquid) Support: Improvement of the Enzyme Activity and Stability

A magnetic nanocomposite was prepared by entrapment of Fe₃O₄ nanoparticles into the cross-linked ionic liquid/epoxy type polymer. The resulting support was used for covalent immobilization of cellulase through the reaction with epoxy groups. The ionic surface of the support improved the adsorption of enzyme, and a large amount of enzyme (106.1 mg/g) was loaded onto the support surface. The effect of the presence of ionic monomer and covalent binding of enzyme was also investigated. The structure of support was characterized by various instruments such as FT-IR, TGA, VSM, XRD, TEM, SEM, and DLS. The activity and stability of immobilized cellulase were investigated in the prepared support. The results showed that the ionic surface and covalent binding of enzyme onto the support improved the activity, thermal stability, and reusability of cellulase compared to free cellulase.

Immobilization of cellulase proteins on zeolitic imidazolate framework (ZIF-8)/polyvinylidene fluoride hybrid membranes

ZIF-8/PVDF hybrid membranes have been applied in cellulase immobilization for the first time, which improves cellulase stability with preserved activity.

Recyclable magnetic carboxymethyl chitosan/calcium alginate - cellulase bioconjugates for corn stalk hydrolysis

The use of cellulase hydrolysis of straw to produce fermentable sugars has many application prospects. However, cellulase is very expensive, which hampers its industrial applications. To improve cellulase's catalytic activity and reduce the enzyme cost, magnetite carboxymethyl chitosan/calcium alginate - cellulase bioconjugate (MCCCB) was synthesized via an improved hydrothermal method, molecular self-assembly technology, physical absorption, embedding and covalent bonding. Its loading capacity was 3.95mg/mL, and the catalytic activity increased to 267.18%. We decreased the release rate, improved the reusability, and enhanced the stability of MCCCB. Corn stalk hydrolysis also greatly improved, and the overall yield of fermentable sugars increased by 698.26%. All of these results indicate that MCCCB could significantly improve the efficiency of cellulase, greatly reduce the cost of enzyme, and effectively promote the production of fermentable sugars.

Utilization of spent coffee grounds for isolation and stabilization of Paenibacillus chitinolyticus CKS1 cellulase by immobilization

This study has explored the feasibility of using spent coffee grounds as a good supporting material for the Paenibacillus chitinolyticus CKS1 cellulase immobilization. An optimal operational conditions in a batch-adsorption system were found to be: carrier mass of 12 g/L, under the temperature of 45 °C and no pH adjustments. The immobilization yield reached about 71%. An equilibrium establishment between the cellulase and the carrier surface occurred within 45 min, whereas the process kinetics may be predicted by the pseudo-second-order model. An immobilized cellulase preparation expressed very good avicelase activity, this reached up to 2.67 U/g, and revealed an improved storage stability property, compared to free enzyme sample counterpart. The addition of metal ions, such as K⁺ and Mg²⁺ did not affect positively immobilization yield results, but on the contrary, contributed to an improved bio-activities of the immobilized cellulase, thus may be employed before each enzyme application. The method developed in this study offers a cheap and effective alternative for immediate enzyme isolation from the production medium and its stabilization, compared to other carriers used for the immobilization.

A useful method integrating production and immobilization of recombinant cellulase

The development of cellulase-based bioprocess is afflicted by the processing efficiency of enzymes. To address this issue, a method based on artificial oil bodies (AOBs) was proposed to integrate production and immobilization of recombinant cellulase. First, the heterologous endoglucanase (celA), cellobiohydrolase (celK), and β-glucosidase (gls) genes were individually fused with oleosin, a structural protein of plant seed oils. After expression in Escherichia coli, each fusion protein of insolubility was mixed together with plant oils. AOBs were assembled by subjecting the mixture to sonication. Consequently, active CelA, CelK, and Gls were resumed and co-immobilized on AOBs surface. Finally, the assembly condition (including the protein ratio) and the reaction condition were further optimized by response surface methodology. The resulting AOBs-bound cellulase remained stable for 4 cycles of cellulose-hydrolyzed reactions. Overall, the result shows a promise of this proposed approach for processing recombinant cellulase, which may provide a facile method to investigate optimum combination of cellulase components towards various cellulosic materials.

From protein engineering to immobilization: promising strategies for the upgrade of industrial enzymes

Enzymes found in nature have been exploited in industry due to their inherent catalytic properties in complex chemical processes under mild experimental and environmental conditions. The desired industrial goal is often difficult to achieve using the native form of the enzyme. Recent developments in protein engineering have revolutionized the development of commercially available enzymes into better industrial catalysts. Protein engineering aims at modifying the sequence of a protein, and hence its structure, to create enzymes with improved functional properties such as stability, specific activity, inhibition by reaction products, and selectivity towards non-natural substrates. Soluble enzymes are often immobilized onto solid insoluble supports to be reused in continuous processes and to facilitate the economical recovery of the enzyme after the reaction without any significant loss to its biochemical properties. Immobilization confers considerable stability towards temperature variations and organic solvents. Multipoint and multisubunit covalent attachments of enzymes on appropriately functionalized supports via linkers provide rigidity to the immobilized enzyme structure, ultimately resulting in improved enzyme stability. Protein engineering and immobilization techniques are sequential and compatible approaches for the improvement of enzyme properties. The present review highlights and summarizes various studies that have aimed to improve the biochemical properties of industrially significant enzymes.

Preparation of a pH-sensitive polyacrylate amphiphilic copolymer and its application in cellulase immobilization

P(MDB), a pH-sensitive and reversible water-soluble copolymer, was synthesized with methacrylic acid (MAA), 2-(dimethylamino) ethyl methacrylate (DMAEMA), and butyl methacrylate (BMA) and used as carrier for cellulase. The copolymer is insoluble between pH 2.5 and 4.1, and soluble below pH 2.5 or above 4.1. Its recovery in aqueous solution was 97.2% by adjusting its isoelectric point (pI) to 3.1. Cellulase was covalently immobilized on P(MDB) with 1-ethyl-3-(3-dimethyllaminopropyl) carbodiimide. Under optimized conditions, the activity yield of immobilized cellulase was 63.24% and its recovery was 96.8% by adjusting the pI to 3.5. Maximum activity of the immobilized cellulase was achieved at 60 °C (pH 5.0), while free cellulase exhibited maximum activity at 55 °C (pH 5.0). The immobilized cellulase retained 83.1% of its initial activity after repeated five cycles of hydrolysis reaction. P(MDB) is a promising carrier for immobilizing enzymes with high and low optimum pH due to its dissolving characteristics.

Ultrasonication--a complementary 'green chemistry' tool to biocatalysis: a laboratory-scale study of lycopene extraction

Lycopene is bequeathed with multiple bio-protective roles, primarily attributed to its unique molecular structure. The concomitant exploitation of two of the green chemistry tools viz., sonication and biocatalysis is reported here for the laboratory scale extraction of lycopene from tomato peel. The coupled system improved the extraction by 662%, 225% and 150% times over the unaided, only cellulase 'Onozuka R-10' treated and only sonication treated samples respectively. The sonication parameters (duration, cycle and amplitude) during the coupled operation were optimized using response surface methodology (RSM). Derivative UV-visible spectra (i.e., dA/dλ and d(2)A/dλ(2) against λ), FTIR analysis, and DPPH scavenging test suggested that the reported extraction protocol did not affect the molecular structure and bioactivity of the extracted lycopene. The influence of sonication on the probable structural modulation (through UV-visible spectral analysis) and activity of the enzyme were also analyzed. A plausible mechanism is proposed for the enhanced extraction achieved via the coupled system.

Immobilization of catalase via adsorption on poly(styrene-d-glycidylmethacrylate) grafted and tetraethyldiethylenetriamine ligand attached microbeads

Fibrous poly(styrene-d-glycidylmethacrylate) (P(S-GMA)) brushes were grafted on poly(styrene-divinylbenzene) (P(S-DVB)) beads using surface initiated-atom transfer radical polymerization (SI-ATRP). Tetraethyldiethylenetriamine (TEDETA) ligand was incorporated on P(GMA) block. The multi-modal ligand attached beads were used for reversible immobilization of catalase. The influences of pH, ionic strength and initial catalase concentration on the immobilization capacities of the P(S-DVB)-g-P(S-GMA)-TEDETA beads have been investigated. Catalase adsorption capacity of P(S-DVB-g-P(S-GMA)-TEDETA beads was found to be 40.8 ± 1.7 mg/g beads at pH 6.5 (with an initial catalase concentration 1.0mg/mL). The K(m) value for immobilized catalase on the P(S-DVB-g-P(S-GMA)-TEDETA beads (0.43 ± 0.02 mM) was found about 1.7-fold higher than that of free enzyme (0.25 ± 0.03 mM). Optimum operational temperature and pH was increased upon immobilization. The same support was repeatedly used five times for immobilization of catalase after regeneration without significant loss in adsorption capacity or enzyme activity.