Optimized preparation of CALB-CLEAs by response surface methodology: The necessity to employ a feeder to have an effective crosslinking

The effect of carbon chain length of cross-linking agent on the functionality of carrier- free immobilized Thermomyces lanuginosa lipase particles

The cross-linked enzyme (CLEs) of Thermomyces lanuginosa lipase (TLL) was prepared in an isocyanide-based multi-component reactions (ICMRs) platform by applying three di-acidic cross-linkers to unveil more factors contributing to the functional properties of CLEs. The linkers were 1,11-undecanedicarboxylic acid, azelaic acid, and adipic acid with 11, 7, and 4 carbon lengths, respectively, providing a proper tool to investigate the effect of linker length on the activity, stability, and selectivity of the resulting CLEs. The immobilization yields of 60-90 % and the specific activities of 168, 88.4 and 49 U/mg were obtained for the CLEs of 1,11-undecanedicarboxylic acid, azelaic acid, adipic acid, respectively. The lower activity of azelaic and adipic acid-mediated CLEs compared to the soluble TLL (110 U/mg) was explained by in silico calculations. The results revealed that as opposed to 1,11-undecanedicarboxylic acid, both linkers tended to penetrate the enzyme active site, thus resulting in a major inhibitory effect on the enzyme functionality. The thermal and co-solvent stability of the immobilized derivatives improved compared to those of free TLL. The selectivity of CLEs was also examined by catalytic release of main omega-3 fatty acids from fish oil, presenting the highest selectivity of 22 for the CLEs of azelaic acid.

Combined cross-linking of Rhizomucor miehei lipase and Candida antarctica lipase B for the effective enrichment of omega-3 fatty acids in fish oil

The incorporation of a non-specific lipase and a sn-1,3 specific one in a single immobilized system can be a promising approach for the exploitation of both lipases. A one-step immobilization platform mediated by an isocyanide-based multi-component reaction was applied to create co-cross-linked enzymes (co-CLEs) of lipases from Rhizomucor miehei (sn-1,3 specific) and Candida antarctica (non-specific). Glutaraldehyde was found to be effective cross-linker by producing specific activity of 16.9 U/mg and immobilization yield of 99 %. High activity recovery of up to 404 % was obtained for immobilized derivatives. Leaking experiment showed covalent nature of the cross-linking processes. BSA had considerable effect on the immobilization process, providing 87-100 % immobilization yields and up to 10 times improvement in the specific activity of the immobilized derivatives. Scanning electron microscopy images showed flower-like and rod-like structures for the CLEs prepared by glutaraldehyde and undecanedicarboxylic acid, respectively. The prepared co-CLEs were examined in non-selective enrichment of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) from fish oil, showing capability of releasing up to 100 % of both omega-3 fatty acids within 8 h of the reaction. The reusability of co-CLEs in five successive cycles presented retaining 63-72 % of their initial activities after the fifth reuse cycle in the hydrolysis reaction.

Enzyme immobilization technology as a tool to innovate in the production of biofuels: A special review of the Cross-Linked Enzyme Aggregates (CLEAs) strategy

This review emphasizes the crucial role of enzyme immobilization technology in advancing the production of two main biofuels, ethanol and biodiesel, with a specific focus on the Cross-linked Enzyme Aggregates (CLEAs) strategy. This method of immobilization has gained attention due to its simplicity and affordability, as it does not initially require a solid support. CLEAs synthesis protocol includes two steps: enzyme precipitation and cross-linking of aggregates using bifunctional agents. We conducted a thorough search for papers detailing the synthesis of CLEAs utilizing amylases, cellulases, and hemicellulases. These key enzymes are involved in breaking down starch or lignocellulosic materials to produce ethanol, both in first and second-generation processes. CLEAs of lipases were included as these enzymes play a crucial role in the enzymatic process of biodiesel production. However, when dealing with large or diverse substrates such as lignocellulosic materials for ethanol production and oils/fats for biodiesel production, the use of individual enzymes may not be the most efficient method. Instead, a system that utilizes a blend of enzymes may prove to be more effective. To innovate in the production of biofuels (ethanol and biodiesel), enzyme co-immobilization using different enzyme species to produce Combi-CLEAs is a promising trend.

Easy and Versatile Technique for the Preparation of Stable and Active Lipase-Based CLEA-like Copolymers by Using Two Homofunctional Cross-Linking Agents: Application to the Preparation of Enantiopure Ibuprofen

An easy and versatile method was designed and applied successfully to obtain access to lipase-based cross-linked-enzyme aggregate-like copolymers (CLEA-LCs) using one-pot, consecutive cross-linking steps using two types of homobifunctional cross-linkers (glutaraldehyde and putrescine), mediated with amine activation through pH alteration (pH jump) as a key step in the process. Six lipases were utilised in order to assess the effectiveness of the technique, in terms of immobilization yields, hydrolytic activities, thermal stability and application in kinetic resolution. A good retention of catalytic properties was found for all cases, together with an important thermal and storage stability improvement. Particularly, the CLEA-LCs derived from Candida rugosa lipase showed an outstanding behaviour in terms of thermostability and capability for catalysing the enantioselective hydrolysis of racemic ibuprofen ethyl ester, furnishing the eutomer (S)-ibuprofen with very high conversion and enantioselectivity.

Combined cross-linked enzyme aggregates of cyclodextrin glucanotransferase and maltogenic amylase from Bacillus lehensis G1 for maltooligosaccharides synthesis

Maltooligosaccharides (MOS) are functional oligosaccharides that can be synthesized through enzymatic cascade reaction between cyclodextrin glucanotransferase (CGTase) and maltogenic amylase (Mag1) from Bacillus lehensis G1. To address the problems of low operational stability and non-reusability of free enzymes, both enzymes were co-immobilized as combined cross-linked enzyme aggregates (Combi-CLEAs-CM) with incorporation of bovine serum albumin (BSA) and Tween 80 (Combi-CLEAs-CM-add). Combi-CLEAs-CM and Combi-CLEAs-CM-add showed activity recoveries of 54.12 % and 69.44 %, respectively after optimization. Combi-CLEAs-CM-add showed higher thermal stability at higher temperatures (40 °C) with longer half-life (46.20 min) as compared to those of free enzymes (36.67 min) and Combi-CLEAs-CM (41.51 min). Both combi-CLEAs also exhibited higher pH stability over pH 5 to pH 9, and displayed excellent reusability with >50 % of initial activity retained after four cycles. The reduction in K_m value of about 22.80 % and 1.76-fold increase in starch hydrolysis in comparison to Combi-CLEAs-CM attested the improvement of enzyme-substrate interaction by Tween 80 and pores formation by BSA in Combi-CLEAs-CM-add. The improved product specificity of Combi-CLEAs-CM-add also produced the highest yield of MOS (492 mg/g) after 3 h. Therefore, Combi-CLEAs-CM-add with ease of preparation, excellent reusability and high operational stability is believed to be highly efficacious biocatalyst for MOS production.

(Magnetic) Cross-Linked Enzyme Aggregates of Cellulase from T. reesei: A Stable and Efficient Biocatalyst

Cross-linked enzyme aggregates (CLEAs) represent an effective tool for carrier-free immobilization of enzymes. The present study promotes a successful application of functionalized magnetic nanoparticles (MNPs) for stabilization of cellulase CLEAs. Catalytically active CLEAs and magnetic cross-linked enzyme aggregates (mCLEAs) of cellulase from Trichoderma reesei were prepared using glutaraldehyde (GA) as a cross-linking agent and the catalytic activity and stability of the CLEAs/mCLEAs were investigated. The influence of precipitation agents, cross-linker concentration, concentration of enzyme, addition of bovine serum albumin (BSA), and addition of sodium cyanoborohydride (NaBH₃CN) on expressed activity and immobilization yield of CLEAs/mCLEAs was studied. Particularly, reducing the unsaturated Schiff's base to form irreversible linkages is important and improved the activity of CLEAs (86%) and mCLEAs (91%). For increased applicability of CLEAs/mCLEAs, we enhanced the activity and stability at mild biochemical process conditions. The reusability after 10 cycles of both CLEAs and mCLEAs was investigated, which retained 72% and 65% of the initial activity, respectively. The thermal stability of CLEAs and mCLEAs in comparison with the non-immobilized enzyme was obtained at 30 °C (145.65% and 188.7%, respectively) and 50 °C (185.1% and 141.4%, respectively). Kinetic parameters were determined for CLEAs and mCLEAs, and the K_M constant was found at 0.055 ± 0.0102 mM and 0.037 ± 0.0012 mM, respectively. The maximum velocity rate (V_max) was calculated as 1.12 ± 0.0012 µmol/min for CLEA and 1.17 ± 0.0023 µmol/min for mCLEA. Structural characterization was studied using XRD, SEM, and FT-IR. Catalytical properties of immobilized enzyme were improved with the addition of reducent NaBH₃CN by enhancing the activity of CLEAs and with addition of functionalized aminosilane MNPs by enhancing the activity of mCLEAs.

Lipase immobilization via cross-linked enzyme aggregates: Problems and prospects - A review

In this review we have focused on the preparation of cross-linked enzyme aggregates (CLEAs) from lipases, as these are among the most used enzyme in bioprocesses. This immobilization method is considered very attractive due to preparation simplicity, non-use of supports and the possibility of using crude enzyme extracts. CLEAs provide lipase stabilization under extreme temperature or pH conditions or in the presence of organic solvents, in addition to preventing enzyme leaching in aqueous medium. However, it presents some problems in the preparation and limitations in their use. The problems in preparation refer mainly to the crosslinking step, and may be solved using an aminated feeder. The problems in handling have been tackled designing magnetic-CLEAs or trapping the CLEAs in particles with better mechanical properties, the substrate diffusion problems has been reduced by producing more porous-CLEAs, etc. The enzyme co-immobilization using combi-CLEAs is also a new tendency. Therefore, this review explores the CLEAs methodology aimed at lipase immobilization and its applications.

Production and Characterization of Cross-Linked Aggregates of Geobacillus thermoleovorans CCR11 Thermoalkaliphilic Recombinant Lipase

Immobilization of enzymes has many advantages for their application in biotechnological processes. In particular, the cross-linked enzyme aggregates (CLEAs) allow the production of solid biocatalysts with a high enzymatic loading and the advantage of obtaining derivatives with high stability at low cost. The purpose of this study was to produce cross-linked enzymatic aggregates (CLEAs) of LipMatCCR11, a 43 kDa recombinant solvent-tolerant thermoalkaliphilic lipase from Geobacillus thermoleovorans CCR11. LipMatCCR11-CLEAs were prepared using (NH4)2SO4 (40% w/v) as precipitant agent and glutaraldehyde (40 mM) as cross-linker, at pH 9, 20 °C. A U10(56) uniform design was used to optimize CLEA production, varying protein concentration, ammonium sulfate %, pH, glutaraldehyde concentration, temperature, and incubation time. The synthesized CLEAs were also analyzed using scanning electron microscopy (SEM) that showed individual particles of <1 µm grouped to form a superstructure. The cross-linked aggregates showed a maximum mass activity of 7750 U/g at 40 °C and pH 8 and retained more than 20% activity at 100 °C. Greater thermostability, resistance to alkaline conditions and the presence of organic solvents, and better durability during storage were observed for LipMatCCR11-CLEAs in comparison with the soluble enzyme. LipMatCCR11-CLEAs presented good reusability by conserving 40% of their initial activity after 9 cycles of reuse.

Textile Dye Biodecolorization by Manganese Peroxidase: A Review

Wastewater emissions from textile factories cause serious environmental problems. Manganese peroxidase (MnP) is an oxidoreductase with ligninolytic activity and is a promising biocatalyst for the biodegradation of hazardous environmental contaminants, and especially for dye wastewater decolorization. This article first summarizes the origin, crystal structure, and catalytic cycle of MnP, and then reviews the recent literature on its application to dye wastewater decolorization. In addition, the application of new technologies such as enzyme immobilization and genetic engineering that could improve the stability, durability, adaptability, and operating costs of the enzyme are highlighted. Finally, we discuss and propose future strategies to improve the performance of MnP-assisted dye decolorization in industrial applications.

Efficient substrate accessibility of cross-linked levanase aggregates using dialdehyde starch as a macromolecular cross-linker

Cross-linked enzyme aggregates (CLEAs) are influenced by mass diffusion limitations such as the degree of molecular cross-linking attained, which affects substrate accessibility. Thus, this study seeks to improve substrate accessibility using macromolecular cross-linkers in cross-linked levanase aggregates (CLLAs) formation for levan-type fructooligosaccharides (L-FOS) production. Dialdehyde starch-tapioca (DAST) was successfully developed and used to cross-link levanase to form CLLAs-D and with bovine serum albumin (BSA) to form CLLAs-DB which showed activity recoveries of 65.6% and 81.6%, respectively. After cross-linking, the pH (6-10) and thermal stability (30-40 °C) increased, and organic solvent tolerance resulted in the activation of CLLAs. Likewise, CLLAs-DB had higher substrate affinity and accessibility and a higher effectiveness factors than CLLAs-D. The total L-FOS yield of CLLAs-DB (78.9% (w/v)) was higher than that of CLLAs-D (62.4% (w/v)). Therefore, as a cross-linker, DAST may have application prospects as a promising and green biocatalyst for product formation.

Preparation of cross-linked enzyme aggregates of lipase from Aspergillus niger: process optimization, characterization, stability, and application for epoxidation of lemongrass oil

Cross-linked enzyme aggregates (CLEAs) of lipase were prepared after fractional precipitation with 40-50% ammonium sulfate and then cross-linking with glutaraldehyde. The process variables for the preparation of lipase-CLEAs such as glutaraldehyde concentration, cross-linking period, and initial pH of medium were optimized. The optimized conditions for the preparation of lipase-CLEAs were 25 mM/80 min/pH 7.0, and 31.62 mM/90 min/pH 6.0 with one factor at a time approach and numerical optimization with central composite design, respectively. Lipase-CLEAs were characterized by particle size analysis, SEM, and FTIR. Cross-linking not only shifted the optimal pH and temperature from 7.0 to 7.5 and 40-45 to 45-50 °C, but also altered the secondary structure. Lipase-CLEAs showed an increase in K_m by 7.70%, and a decrease in V_max by 16.63%. Lipase-CLEAs presented better thermostability than free lipase as evident from thermal inactivation constants (t_1/2, D and E_d value), and thermodynamic parameters (E_d, ΔH°, ΔG°, and ΔS°) in the range of 50-70 °C. Lipase-CLEAs retained more than 65% activity up to four cycles and showed good storage stability for 12 days when stored at 4 ± 2 °C. They were successfully utilized for the epoxidation of lemongrass oil which was confirmed by changes in iodine value, epoxide value, and FTIR spectra.

Chitosan-based CLEAs from Aspergillus niger type A feruloyl esterase: high-productivity biocatalyst for alkyl ferulate synthesis

The enzymatic synthesis of alkyl ferulates is an important reaction in cosmetic and pharmaceutical chemistries, since it may allow to expand the biorefinery concept valorizing biomass wastes enriched in ferulic acid. However, robust biocatalysts for that purpose are scarce. Herein, we have immobilized the type A feruloyl esterase from Aspergillus niger (AnFaeA) as cross-linked enzyme aggregates, employing chitosan as co-feeder (ChCLEAs). High immobilization yields and relative activity recovery were attained in all assessed conditions (> 93%). Furthermore, we enhanced the thermal stability of the soluble enzyme 32-fold. AnFaeA-ChCLEAs were capable to quantitatively perform the solvent-free direct esterification of short- to medium-chain alkyl ferulates (C4-C12) in less than 24 h. By raising the operational temperature to 50 °C, AnFaeA-ChCLEAs transformed 350 mM ferulic acid into isopentyl ferulate with a space-time yield of 46.1 g of product × L^-1 × day^-1, 73-fold higher than previously reported. The overall sustainability of this alkyl ferulate production bioprocess is supported by the high total turnover number (TTN 7 × 10⁵) and the calculated green metrics (E factor = 30). Therefore, we herein present a robust, efficient, and versatile heterogeneous biocatalyst useful for the synthesis of a wide diversity of alkyl ferulates. KEY POINTS: • CLEAs of feruloyl esterase A from A. niger using chitosan as co-feeder were obtained. • Microenvironment of the biocatalysts allowed to obtain C1 to C18 alkyl ferulates. • Biocatalyst at boundary conditions showed a high productivity of 46 g/L day. Graphical Abstract.

Carrier-bound and carrier-free immobilization of type A feruloyl esterase from Aspergillus niger: Searching for an operationally stable heterogeneous biocatalyst for the synthesis of butyl hydroxycinnamates

Feruloyl esterases synthesize butyl hydroxycinnamates, molecules possessing interesting biological properties, nonetheless, they exhibit a low stability under synthesis conditions in organic solvents, restricting its use. To enhance its operational stability in synthesis, we immobilized type A feruloyl esterase from Aspergillus niger (AnFAEA) using several carrier-bound and carrier-free strategies. The most active biocatalysts were: 1) AnFAEA immobilized on epoxy-activated carriers (protein load of 0.6 mg_enzyme x mg^-1_carrier) that recovered 91 % of the initial hydrolytic activity, and 2) AnFAEA aggregated and cross-linked in the presence of 5 mg of BSA and 15 mM of glutaraldehyde (AnFAEA-amino-CLEAs), which exhibited 385 % of its initial hydrolytic activity; both using 4-nitrophenyl butyrate as substrate. The AnFAEA-amino-CLEAs were 12.7 times more thermostable at 60 °C than the AnFAEA immobilized on epoxy-activated carrier, thus AnFAEA-amino-CLEAs were selected for further characterization. Interestingly, during methyl sinapate hydrolysis (pH 7.2 and 30 °C), AnFAEA-amino-CLEAs K_M was 15 % higher, while during butyl sinapate synthesis the K_M was reduced in 63 %, both compared with the soluble enzyme. The direct esterification of butyl sinapate at solvent free conditions using sinapic acid 50 mM, reached 95 % conversion after 24 h employing AnFAEA-amino-CLEAs, which could be used for 10 cycles without significant activity losses, demonstrating their outstanding operational stability.

Preparation of CLEAs and magnetic CLEAs of a recombinant l-arabinose isomerase for d-tagatose synthesis

The insolubilization of a recombinant l-arabinose isomerase (l-AI) from Enterococcus faecium by cross-linked enzyme aggregates (CLEA) was investigated, aiming the biochemical production of d-tagatose from d-galactose. d-tagatose is a functional sweetener that has many health benefits, sweetening properties and lower calorific value. Different precipitants (ammonium sulfate, ethanol, acetone, polyethylene glycol 4000) were used in the first step of the protocol, in order to establish the precipitation conditions, and the best results of yield and activity were achieved with ammonium sulfate. In order to facilitate the recovery of the biocatalyst, a new strategy for immobilization of the multimeric enzyme l-arabinose isomerase was proposed. Magnetic cross-linked enzyme aggregates (m-CLEA) were obtained using ammonium sulfate as precipitant and magnetic nanoparticles (MNP) functionalized with APTES (3- Aminopropyltriethoxysilane). Another immobilization strategy was to immobilize the enzyme onto MNP-APTES, as a control. The best results were achieved when the m-CLEA was produced with 20 mg of MNP, 7.69 U. g^-1 of enzymatic activity, 7.61 % of recovered activity, 99 % of yield of immobilization. On the other hand, the enzyme immobilized onto MNP-APTES, presented only 2.12 U. g^-1 of enzymatic activity, 32.3 % of recovered activity, and 15 % of yield of immobilization.

Immobilization of Enzymes as Cross-Linked Enzyme Aggregates: General Strategy to Obtain Robust Biocatalysts

Among carrier-free immobilization techniques, cross-linked enzyme aggregates (CLEA) have been extensively described for a great number of diverse enzymes. During the last two decades, numerous efforts have been devoted to identify and understand the main variables involved in CLEA's preparation process leading to robust immobilized biocatalysts. Since every enzyme immobilized as CLEA requires specific conditions and protocols, herein we provide a general preparation strategy where main parameters are highlighted and correlated with a possible desired improved enzyme feature.

Soluble enzyme cross-linking via multi-component reactions: a new generation of cross-linked enzymes

Production of CLEs using a multi-component reaction.

Dextran Aldehyde in Biocatalysis: More Than a Mere Immobilization System

Dextran aldehyde (dexOx), resulting from the periodate oxidative cleavage of 1,2-diol moiety inside dextran, is a polymer that is very useful in many areas, including as a macromolecular carrier for drug delivery and other biomedical applications. In particular, it has been widely used for chemical engineering of enzymes, with the aim of designing better biocatalysts that possess improved catalytic properties, making them more stable and/or active for different catalytic reactions. This polymer possesses a very flexible hydrophilic structure, which becomes inert after chemical reduction; therefore, dexOx comes to be highly versatile in a biocatalyst design. This paper presents an overview of the multiple applications of dexOx in applied biocatalysis, e.g., to modulate the adsorption of biomolecules on carrier surfaces in affinity chromatography and biosensors design, to serve as a spacer arm between a ligand and the support in biomacromolecule immobilization procedures or to generate artificial microenvironments around the enzyme molecules or to stabilize multimeric enzymes by intersubunit crosslinking, among many other applications.

CLEAs, Combi-CLEAs and ‘Smart’ Magnetic CLEAs: Biocatalysis in a Bio-Based Economy

Biocatalysis has emerged in the last decade as a pre-eminent technology for enabling the envisaged transition to a more sustainable bio-based economy. For industrial viability it is essential that enzymes can be readily recovered and recycled by immobilization as solid, recyclable catalysts. One method to achieve this is via carrier-free immobilization as cross-linked enzyme aggregates (CLEAs). This methodology proved to be very effective with a broad selection of enzymes, in particular carbohydrate-converting enzymes. Methods for optimizing CLEA preparations by, for example, adding proteic feeders to promote cross-linking, and strategies for making the pores accessible for macromolecular substrates are critically reviewed and compared. Co-immobilization of two or more enzymes in combi-CLEAs enables the cost-effective use of multiple enzymes in biocatalytic cascade processes and the use of “smart” magnetic CLEAs to separate the immobilized enzyme from other solids has raised the CLEA technology to a new level of industrial and environmental relevance. Magnetic-CLEAs of polysaccharide-converting enzymes, for example, are eminently suitable for use in the conversion of first and second generation biomass.

Evaluation of Strategies to Produce Highly Porous Cross-Linked Aggregates of Porcine Pancreas Lipase with Magnetic Properties

The preparation of highly porous magnetic crosslinked aggregates (pm-CLEA) of porcine pancreas lipase (PPL) is reported. Some strategies to improve the volumetric activity of the immobilized biocatalyst were evaluated, such as treatment of PPL with enzyme surface-modifying agents (polyethyleneimine or dodecyl aldehyde), co-aggregation with protein co-feeders (bovine serum albumin and/or soy protein), use of silica magnetic nanoparticles functionalized with amino groups (SMNPs) as separation aid, and starch as pore-making agent. The combination of enzyme surface modification with dodecyl aldehyde, co-aggregation with SMNPs and soy protein, in the presence of 0.8% starch (followed by hydrolysis of the starch with α-amylase), yielded CLEAs expressing high activity (immobilization yield around 100% and recovered activity around 80%), high effectiveness factor (approximately 65% of the equivalent free enzyme activity) and high stability at 40 °C and pH 8.0, i.e., PPL CLEAs co-aggregated with SMNPs/bovine serum albumin or SMNPs/soy protein retained 80% and 50% activity after 10 h incubation, respectively, while free PPL was fully inactivated after 2 h. Besides, highly porous magnetic CLEAs co-aggregated with soy protein and magnetic nanoparticles (pm-SP-CLEAs) showed good performance and reusability in the hydrolysis of tributyrin for five 4h-batches.

Immobilization of ligninolytic enzymes from white-rot fungi in cross-linked aggregates

Ligninolytic enzymes from white-rot fungi are widely used in biotechnological processes. However, the application of these enzymes as free enzymes is limited due to their instability and lack of reusability. Enzyme stabilization is therefore a major challenge in biocatalytic process research, and immobilization methods are desirable. Using cross-linked enzyme aggregates (CLEAs) such as magnetic CLEAs, porous-CLEAs and combi-CLEAs is a promising technique for overcoming these issues. Cross-linking methods can stabilize and immobilize enzymes by interconnecting enzyme molecules via multiple bonds using cross-linking agents such as glutaraldehyde. The high catalyst density and microporous assembly of CLEAs guarantee high catalyst activity, which, together with their long shelf life, operational stability, and reusability, provide a cost-efficient alternative to matrix-assisted immobilization approaches. Here, we review current progress in ligninolytic enzyme immobilization and provide a comprehensive review of CLEAs. Moreover, we summarize the use of these CLEAs for biocatalysis processes, bioremediation such as dye decolourization, wastewater treatment or pharmaceutically active compound elimination.

A strategic approach for direct recovery and stabilization of Fusarium sp. ICT SAC1 cutinase from solid state fermented broth by carrier free cross-linked enzyme aggregates

The major hurdles in commercial exploitation of cutinase (having both esterolytic and lipolytic activities) with potent industrial applications are its high production cost, operational instability and reusability. Although commercially available in immobilized form, its immobilization process (synthesis of support/carrier) makes it expensive. Herein we tried to address multiple issues of production cost, stability, and reusability, associated with cutinase. Waste watermelon rinds, an agroindustrial waste was considered as a cheap support for solid state fermentation (SSF) for cutinase production by newly isolated Fusarium sp. ICT SAC1. Subsequently, carrier free cross-linked enzyme aggregates of cutinase (cut-CLEA) directly from the SSF crude broth were developed. All the process variables affecting CLEA formation along with the different additives were evaluated. It was found that 50% (w/v) of ammonium sulphate, 125μmol of glutaraldehyde, cross-linking for 1h at 30°C and broth pH of 7.0, yielded 58.12% activity recovery. All other additives (hexane, butyric acid, sodium dodecyl sulphate, Trition-X 100, Tween-20, BSA) evaluated presented negative results to our hypothesis. Kinetics and morphology studies confirmed the diffusive nature of cut-CLEA and BSA cut-CLEA. Developed CLEA showed better thermal, solvent, detergent and storage stability, making it more elegant and efficient for industrial biocatalytic process.

Immobilized ligninolytic enzymes: An innovative and environmental responsive technology to tackle dye-based industrial pollutants - A review

In the twenty-first century, chemical and associated industries quest a transition prototype from traditional chemical-based concepts to a greener, sustainable and environmentally-friendlier catalytic alternative, both at the laboratory and industrial scale. In this context, bio-based catalysis offers numerous benefits along with potential biotechnological and environmental applications. The bio-based catalytic processes are energy efficient than conventional methodologies under moderate processing, generating no and negligible secondary waste pollution. Thanks to key scientific advances, now, solid-phase biocatalysts can be economically tailored on a large scale. Nevertheless, it is mandatory to recover and reprocess the enzyme for their commercial feasibility, and immobilization engineering can efficiently accomplish this challenge. The first part of the present review work briefly outlines the immobilization of lignin-modifying enzymes (LMEs) including lignin peroxidase (LiP), manganese peroxidase (MnP) and laccase of white-rot fungi (WRF). Whereas, in the second part, a particular emphasis has been given on the recent achievements of carrier-immobilized LMEs for the degradation, decolorization, or detoxification of industrial dyes and dye-based industrial wastewater effluents.

Polyethylenimine: a very useful ionic polymer in the design of immobilized enzyme biocatalysts

This review discusses the possible roles of polyethylenimine (PEI) in the design of improved immobilized biocatalysts from diverse perspectives.

A novel cross-linked enzyme aggregates (CLEAs) of papain and neutrase-production, partial characterization and application

The neutrase (EC 3.4.24.4) and papain (EC 3.4.22.2) were together immobilized ascross-linked enzyme aggregates (N-P-CLEAs) and their properties were characterized. The influence of the precipitant, cross-linking ratio of glutaraldehyde and cross-linking time were investigated. Ethanol was selected as the more efficient precipitant compared with ammonium sulfate. The proper cross-linking ratio of enzyme and glutaraldehyde was 1:5 (v/v) and the optimized cross-linking time was 4h. N-P-CLEAs showed obvious improvement in thermal stability and pH stability than the free enzyme (P<0.05) and could hold relatively high activity retention in nonpolar and hydrophilic solvents and without activity loss at 4°C for more than six months. The cross-linking reaction had been appeared in N-P-CLEAs and more orderly microscopic surface morphology of N-P-CLEAs was observed. The molecular weight and thermal denaturation temperature of N-P-CLEAs were increased while the isoelectric point was decreased compared with those of the free enzymes. Application of N-P-CLEAs in bean proteins and zein showed a higher degree of hydrolysis, such as the hydrolysis degree of mung bean protein hydrolyzed by N-P-CLEAs was 12%, increased by approximately 4.5% compared to that of free enzyme. The results demonstrated that the N-P-CLEAs was suitable for application in food protein hydrolysis.

Immobilization of Glycoside Hydrolase Families GH1, GH13, and GH70: State of the Art and Perspectives

Glycoside hydrolases (GH) are enzymes capable to hydrolyze the glycosidic bond between two carbohydrates or even between a carbohydrate and a non-carbohydrate moiety. Because of the increasing interest for industrial applications of these enzymes, the immobilization of GH has become an important development in order to improve its activity, stability, as well as the possibility of its reuse in batch reactions and in continuous processes. In this review, we focus on the broad aspects of immobilization of enzymes from the specific GH families. A brief introduction on methods of enzyme immobilization is presented, discussing some advantages and drawbacks of this technology. We then review the state of the art of enzyme immobilization of families GH1, GH13, and GH70, with special attention on the enzymes β-glucosidase, α-amylase, cyclodextrin glycosyltransferase, and dextransucrase. In each case, the immobilization protocols are evaluated considering their positive and negative aspects. Finally, the perspectives on new immobilization methods are briefly presented.

Cross-linked enzyme aggregates (CLEA) in enzyme improvement – a review

Structural and functional catalytic characteristics of cross-linked enzyme aggregates (CLEA) are reviewed. Firstly, advantages of enzyme immobilization and existing types of immobilization are described. Then, a wide description of the factors that modify CLEA activity, selectivity and stability is presented. Nowadays CLEA offers an economic, simple and easy tool to reuse biocatalysts, improving their catalytic properties and stability. This immobilization methodology has been widely and satisfactorily tested with a great variety of enzymes and has demonstrated its potential as a future tool to optimize biocatalytic processes.

Magnetic combined cross-linked enzyme aggregates of horseradish peroxidase and glucose oxidase: an efficient biocatalyst for dye decolourization

In this study, the magnetic combined cross-linked enzyme aggregates (combi-CLEAs) of glucose oxidase (GOD) and horseradish peroxidase (HRP) were designed and prepared successfully.

Preparation and characterization of a Combi-CLEAs from pectinases and cellulases: a potential biocatalyst for grape juice clarification

Combi-CLEAs of pectinases and cellulases were prepared for grape juice clarification.