A comprehensive review on incredible renewable carriers as promising platforms for enzyme immobilization & thereof strategies

Enzyme Immobilization and Co-Immobilization: Main Framework, Advances and Some Applications

Enzymes are outstanding (bio)catalysts, not solely on account of their ability to increase reaction rates by up to several orders of magnitude but also for the high degree of substrate specificity, regiospecificity and stereospecificity. The use and development of enzymes as robust biocatalysts is one of the main challenges in biotechnology. However, despite the high specificities and turnover of enzymes, there are also drawbacks. At the industrial level, these drawbacks are typically overcome by resorting to immobilized enzymes to enhance stability. Immobilization of biocatalysts allows their reuse, increases stability, facilitates process control, eases product recovery, and enhances product yield and quality. This is especially important for expensive enzymes, for those obtained in low fermentation yield and with relatively low activity. This review provides an integrated perspective on (multi)enzyme immobilization that abridges a critical evaluation of immobilization methods and carriers, biocatalyst metrics, impact of key carrier features on biocatalyst performance, trends towards miniaturization and detailed illustrative examples that are representative of biocatalytic applications promoting sustainability.

The combination of covalent and ionic exchange immobilizations enables the coimmobilization on vinyl sulfone activated supports and the reuse of the most stable immobilized enzyme

The coimmobilization of lipases from Rhizomucor miehei (RML) and Candida antarctica (CALB) has been intended using agarose beads activated with divinyl sulfone. CALB could be immobilized on this support, while RML was not. However, RML was ionically exchanged on this support blocked with ethylendiamine. Therefore, both enzymes could be coimmobilized on the same particle, CALB covalently using the vinyl sulfone groups, and RML via anionic exchange on the aminated blocked support. However, immobilized RML was far less stable than immobilized CALB. To avoid the discarding of CALB (that maintained 90% of the initial activity after RML inactivation), a strategy was developed. Inactivated RML was desorbed from the support using ammonium sulfate and 1% Triton X-100 at pH 7.0. That way, 5 cycles of RML thermal inactivation, discharge of the inactivated enzyme and re-immobilization of a fresh sample of RML could be performed. In the last cycle, immobilized CALB activity was still over 90% of the initial one. Thus, the strategy permits that enzymes can be coimmobilized on vinyl sulfone supports even if one of them cannot be immobilized on it, and also permits the reuse of the most stable enzyme (if it is irreversibly attached to the support).

Strategy for Conjugating Oligopeptides to Mesoporous Silica Nanoparticles Using Diazirine-Based Heterobifunctional Linkers

Successful strategies for the attachment of oligopeptides to mesoporous silica with pores large enough to load biomolecules should utilize the high surface area of pores to provide an accessible, protective environment. A two-step oligopeptide functionalization strategy is examined here using diazirine-based heterobifunctional linkers. Mesoporous silica nanoparticles (MSNPs) with average pore diameter of ~8 nm and surface area of ~730 m²/g were synthesized and amine-functionalized. Tetrapeptides Gly-Gly-Gly-Gly (GGGG) and Arg-Ser-Ser-Val (RSSV), and a peptide comprised of four copies of RSSV (4RSSV), were covalently attached via their N-terminus to the amine groups on the particle surface by a heterobifunctional linker, sulfo-succinimidyl 6-(4,4′-azipentanamido)hexanoate (sulfo-NHS-LC-diazirine, or SNLD). SNLD consists of an amine-reactive NHS ester group and UV-activable diazirine group, providing precise control over the sequence of attachment steps. Attachment efficiency of RSSV was measured using fluorescein isothiocyanate (FITC)-tagged RSSV (RSSV-FITC). TGA analysis shows similar efficiency (0.29, 0.31 and 0.26 mol peptide/mol amine, respectively) for 4G, RSSV and 4RSSV, suggesting a generalizable method of peptide conjugation. The technique developed here for the conjugation of peptides to MSNPs provides for their attachment in pores and can be translated to selective peptide-based separation and concentration of therapeutics from aqueous process and waste streams.

Modified alginate-chitosan-TiO2 composites for adsorptive removal of Ni(II) ions from aqueous medium

In this study, organo-funtionalization of sodium-alginate has been carried out using phenylsemicarbazide as modifier to graft N, O-donor atoms containing functional groups (amino-carbamate moieties) to offer novel support for TiO₂ immobilization. Hybrid composite made of aminocarbamated alginate, carboxymethyl chitosan (CMC) and titanium oxide TiO₂ (MCA-TiO₂) was prepared for the promising adsorptive remediation of Ni(II). FT-IR, SEM-EDX were employed to characterize MCA-TiO₂. The optimization of TiO₂ to modified alginate mass ratio was carried out and hydrogel beads with TiO₂/MCA mass ratio of 10.0% (2MCA-TiO₂) revealed highest sorption efficiency. The produced sorbents were adapted in the form of hydrogel beads for operation. Organic functionalization based on aminocarbamate (OCONHNH₂) moieties on linear chains of alginate embedded additional chelating functional sites which enhanced sorption and selectivity. Batch mode experiments were conducted for optimization of pH and sorbent dose. Equilibrium sorption, kinetic and thermodynamic studies were performed to pattern the nature of sorption. Kinetic data was found in close agreement with pseudo-second order rate expression (PSORE). Isothermal equilibrium sorption data was well fitted with Langmuir adsorption model. Maximum sorption capacity was evaluated as 229 mg/g at 298 K and pH = 6.0.

Free and immobilized biocatalysts for removing micropollutants from water and wastewater: Recent progress and challenges

Enzymatic conversion of micropollutants into less-toxic derivatives is an important bioremediation strategy. This paper aims to critically review the progress in water and wastewater treatment by both free and immobilized enzymes presenting this approach as highly efficient and performed under environmentally benign and friendly conditions. The review also summarises the effects of inorganic and organic wastewater matrix constituents on enzymatic activity and degradation efficiency of micropollutants. Finally, application of enzymatic reactors facilitate continuous treatment of wastewater and obtaining of pure final effluents. Of a particular note, enzymatic treatment of micropollutants from wastewater has been mostly reported by laboratory scale studies. Thus, this review also highlights key research gaps of the existing techniques and provides future perspectives to facilitate the transfer of the lab-scale solutions to a larger scale and to improve operationability of biodegradation processes.

Production of a recyclable nanobiocatalyst to synthesize quinazolinone derivatives

Nanobiocatalysts (NBCs) are an emerging innovation that paves the way toward sustainable and eco-friendly endeavors.

Lipase immobilization on glutaraldehyde activated graphene oxide/chitosan/cellulose acetate electrospun nanofibrous membranes and its application on the synthesis of benzyl acetate

In this research, lipase Km12 was immobilized on the glutaraldehyde-activated graphene oxide/chitosan/cellulose acetate nanofibers (GO/Chit/CA NFs) prepared by the electrospinning method. This immobilized lipase exhibited a higher activity value than the free lipase in the acidic pH region. This enzyme showed a 10 °C shift in the maximum temperature activity. Results displayed that the Vmax value of NFs-lipase was 0.64 µmol/min, while it was gained 0.405 µmol/min for the free lipase. The activity of NFs-lipase was reserved 100% after 10 min maintaining at 60 °C, in which the free lipase only kept 75% of its original activity. Moreover, a 20% enhancement in the lipase activity was observed for NFs-lipase after 180 min of incubation at 60 °C, compared to the free enzyme. Reusability studies exhibited that the immobilized lipase well-kept 80% of its original activity after 10 cycles of reusing. Results displayed that 14% of the protein was leaked from NFs-lipase at the same condition. Transesterification results indicated that the free lipase exhibited 65% and 85% conversation level of benzyl acetate after 12 and 24 h of incubation. Besides, the immobilized lipase showed 80% and 95% conversation level at the same condition. These results indicated the high performance of free and immobilized lipase in the production of benzyl acetate for applications in the perfume and cosmetic industries.

Preparation of ZIF@ADH/NAD-MSN/LDH Core Shell Nanocomposites for the Enhancement of Coenzyme Catalyzed Double Enzyme Cascade

The field of enzyme cascades in limited microscale or nanoscale environments has undergone a quick growth and attracted increasing interests in the field of rapid development of systems chemistry. In this study, alcohol dehydrogenase (ADH), lactate dehydrogenase (LDH), and mesoporous silica nanoparticles (MSN) immobilized nicotinamide adenine dinucleotide (NAD⁺) were successfully immobilized on the zeolitic imidazolate frameworks (ZIFs). This immobilized product was named ZIF@ADH/NAD-MSN/LDH, and the effect of the multi-enzyme cascade was studied by measuring the catalytic synthesis of lactic acid. The loading efficiency of the enzyme in the in-situ co-immobilization method reached 92.65%. The synthesis rate of lactic acid was increased to 70.10%, which was about 2.82 times that of the free enzyme under the optimal conditions (40 °C, pH = 8). Additionally, ZIF@ADH/NAD-MSN/LDH had experimental stability (71.67% relative activity after four experiments) and storage stability (93.45% relative activity after three weeks of storage at 4 °C; 76.89% relative activity after incubation in acetonitrile-aqueous solution for 1 h; 27.42% relative activity after incubation in 15% N, N-Dimethylformamide (DMF) solution for 1 h). In summary, in this paper, the cyclic regeneration of coenzymes was achieved, and the reaction efficiency of the multi-enzyme biocatalytic cascade was improved due to the reduction of substrate diffusion.

Immobilization of papain: A review

Papain is a cysteine protease from papaya, with many applications due to its broad specificity. This paper reviews for first time the immobilization of papain on different supports (organic, inorganic or hybrid supports) presenting some of the features of the utilized immobilization strategies (e.g., epoxide, glutaraldehyde, genipin, glyoxyl for covalent immobilization). Special focus is placed on the preparation of magnetic biocatalysts, which will permit the simple recovery of the biocatalyst even if the medium is a suspension. Problems specific to the immobilization of proteases (e.g., steric problems when hydrolyzing large proteins) are also defined. The benefits of a proper immobilization (enzyme stabilization, widening of the operation window) are discussed, together with some artifacts that may suggest an enzyme stabilization that may be unrelated to enzyme rigidification.

Improved adenylate cyclase activity via affinity immobilization onto co-modified GO with bio-inspired adhesive and PEI

Adenylate cyclase (AC) can efficiently catalyze the conversion of adenosine triphosphate (ATP) to cyclic adenosine-3', 5'-monophosphate (cAMP). However, AC directly immobilized on substrate is not desirable due to enzyme inactivation. Herein, bio-inspired adhesive of polydopamine and polyethyleneimine (PDA/PEI) was used as flexible chains to graft on graphene oxide (GO), and the AC was directionally immobilized through affinity between metal ions and his-tags of AC. The properties of modified GO and the activity of immobilized AC were studied in detail. PDA/PEI layers have been proved to improve the amino density of GO surface for affinity groups decoration and adjust the interaction between AC and support. And modified GO by this novel method contributes to subsequent grafting and immobilization of AC by affinity. AC immobilized on modified GO exhibited high activity recovery with about 90 % of free AC, while enzyme immobilized on unmodified GO has been inactivated. This study offers a versatile approach for support modification and enzyme oriented immobilization. PDA/PEI functionalized GO can be used as a promising carrier to immobilize other his-tagged enzymes.

Modulation of the Biocatalytic Properties of a Novel Lipase from Psychrophilic Serratia sp. (USBA-GBX-513) by Different Immobilization Strategies

In this work, the effect of different immobilization procedures on the properties of a lipase obtained from the extremophilic microorganism Serratia sp. USBA-GBX-513, which was isolated from Paramo soils of Los Nevados National Natural Park (Colombia), is reported. Different Shepharose beads were used: octyl-(OC), octyl-glyoxyl-(OC-GLX), cyanogen bromide (BrCN)-, and Q-Sepharose. The performance of the different immobilized extremophile lipase from Serratia (ESL) was compared with that of the lipase B from Candida antarctica (CALB). In all immobilization tests, hyperactivation of ESL was observed. The highest hyperactivation (10.3) was obtained by immobilization on the OC support. Subsequently, the thermal stability at pH 5, 7, and 9 and the stability in the presence of 50% (v/v) acetonitrile, 50% dioxane, and 50% tetrahydrofuran solvents at pH 7 and 40 °C were evaluated. ESL immobilized on octyl-Sepharose was the most stable biocatalyst at 90 °C and pH 9, while the most stable preparation at pH 5 was ESL immobilized on OC-GLX-Sepharose supports. Finally, in the presence of 50% (v/v) tetrahydrofuran (THF) or dioxane at 40 °C, ESL immobilized on OC-Sepharose was the most stable biocatalyst, while the immobilized preparation of ESL on Q-Sepharose was the most stable one in 40% (v/v) acetonitrile.

Evaluating enzyme stabilizations in calcium carbonate: Comparing in situ and crosslinking mediated immobilization

Enzyme immobilization using inorganic materials has been shown to preserve enzyme activity improving and improve their practical applications in biocatalytic process designs. Proper immobilization methods have been used to obtain high recycling and storage stability. In this study, we compared the activity and stability of in situ or crosslink-immobilized enzymes in a CaCO₃ biomineral carrier. More than 30% of the initial enzyme activity was preserved for both the systems after 180 days upon 15 activity measurements at room temperature, confirming the improved stability of these enzyme systems (100 mM phosphate buffer, pH 8.0); however, differences in enzyme loading, activity, and characteristics were observed for each of these methods. Each system exhibited efficacy of 80% and 20%, respectively. Based on the same amount of immobilized enzyme (0.2 mg), the specific activities of hydrolysis of p-nitrophenyl butyrate substrate at room temperature of in situ immobilized carboxyl esterase (CE) and crosslinked CE were 11.37 and 7.63 mM min^-1 mg^-1, respectively (100 mM phosphate buffer, pH 8.0). Moreover, based on the kinetic behavior, in situ immobilized CE exhibited improved catalytic efficiency (Vmax Km^-1) of the enzyme, exhibiting 4-fold higher activity and efficiency values than those of the CE immobilized in CaCO₃. This is the first study to describe the stabilization of enzymes in CaCO₃ and compare the enzyme kinetics and efficiencies between in situ immobilization and crosslinking in CaCO₃ carriers.