One-step purification of a recombinant beta-galactosidase using magnetic cellulose as a support: Rapid immobilization and high thermal stability

Adsorption features of reduced aminated supports modified with glutaraldehyde: Understanding the heterofunctional features of these supports

Immobilization of enzymes on aminated supports using the glutaraldehyde chemistry may involve three different interactions, cationic, hydrophobic, and covalent interactions. To try to understand the impact this heterofunctionality, we study the physical adsorption of the beta-galactosidase from Aspergillus niger, on aminated supports (MANAE) and aminated supports with one (MANAE-GLU) or two molecules of glutaraldehyde (MANAE-GLU-GLU). To eliminate the chemical reactivity of the glutaraldehyde, the supports were reduced using sodium borohydride. After enzyme adsorption, the release of the enzyme from the supports using different NaCl concentrations, Triton X100, ionic detergents (SDS and CTAB), or different temperatures (4 °C to 55 °C) was studied. Using MANAE support, at 0.3 M NaCl almost all the immobilized enzyme was released. Using MANAE-GLU, 0.3 M, and 0.6 M NaCl similar results were obtained. However, incubation at 1 M or 2 M NaCl, many enzyme molecules were not released from the support. For the MANAE-GLU-GLU support, none of the tested concentrations of NaCl was sufficient to release all enzyme bound to the support. Only using high temperatures, 0.6 M NaCl, and 1 % CTAB or SDS, could the totality of the proteins be released from the support. The results shown in this paper confirm the heterofunctional character of aminated supports modified with glutaraldehyde.

Immobilization and Characterization of a Processive Endoglucanase EG5C-1 from Bacillus subtilis on Melamine-Glutaraldehyde Dendrimer-Functionalized Magnetic Nanoparticles

Exploring an appropriate immobilization approach to enhance catalytic activity and reusability of cellulase is of great importance to reduce the price of enzymes and promote the industrialization of cellulose-derived biochemicals. In this study, Fe3O4 magnetic nanoparticles (MNPs) were functionalized with meso-2,3-dimercaptosuccinic acid to introduce carboxyl groups on the surface (DMNPs). Then, melamine-glutaraldehyde dendrimer-like polymers were grafted on DMNPs to increase protein binding sites for the immobilization of processive endoglucanase EG5C-1. Moreover, this dendrimer-like structure was beneficial to protect the conformation of EG5C-1 and facilitate the interaction between substrate and active center. The loading capacity of the functionalized copolymers (MG-DMNPs) for EG5C-1 was about 195 mg/g, where more than 90% of the activity was recovered. Immobilized EG5C-1 exhibited improved thermal stability and increased tolerability over a broad pH range compared with the free one. Additionally, MG-DMNP/EG5C-1 biocomposite maintained approximately 80% of its initial hydrolysis productivity after five cycles of usage using filter paper as the substrate. Our results provided a promising approach for the functionalization of MNPs, enabling the immobilization of cellulases with a high loading capacity and excellent activity recovery.

Lactose hydrolysis in packed-and fluidized-bed reactors using a recombinant β-galactosidase immobilized on magnetic core-shell capsules

The objective of this study was to develop a bioprocess for lactose hydrolysis in diverse dairy matrices, specifically skim milk and cheese whey, utilizing column reactors employing a core-shell enzymatic system featuring β-galactosidase fused to a Cellulose Binding Domain (CBD) tag (β-galactosidase-CBD). The effectiveness of reactor configurations, including ball columns and toothed columns operating in packed and fluidized-bed modes, was evaluated for catalyzing lactose hydrolysis in both skim milk and cheese whey. In a closed system, these reactors achieved lactose hydrolysis rates of approximately 50% within 5 h under all evaluated conditions. Considering the scale of the bioprocess, the developed enzymatic system was capable of continuously hydrolyzing 9.6 L of skim milk while maintaining relative hydrolysis levels of approximately 50%. The biocatalyst, created by immobilizing β-galactosidase-CBD on magnetic core-shell capsules, exhibited exceptional operational stability, and the proposed bioprocess employing these column reactors showcases the potential for scalability.

Region-Directed Enzyme Immobilization through Engineering Protein Surface with Histidine Clusters

Enzyme immobilization is a key enabling technology for a myriad of industrial applications, yet immobilization science is still too empirical to reach highly active and robust heterogeneous biocatalysts through a general approach. Conventional protein immobilization methods lack control over how enzymes are oriented on solid carriers, resulting in negative conformational changes that drive enzyme deactivation. Site-selective enzyme immobilization through peptide tags and protein domains addresses the orientation issue, but this approach limits the possible orientations to the N- and C-termini of the target enzyme. In this work, we engineer the surface of two model dehydrogenases to introduce histidine clusters into flexible regions not involved in catalysis, through which immobilization is driven. By varying the position and the histidine density of the clusters, we create a small library of enzyme variants to be immobilized on different carriers functionalized with different densities of various metal chelates (Co2+, Cu2+, Ni2+, and Fe3+). We first demonstrate that His-clusters can be as efficient as the conventional His-tags in immobilizing enzymes, recovering even more activity and gaining stability against some denaturing agents. Furthermore, we find that the enzyme orientation as well as the type and density of the metal chelates affect the immobilization parameters (immobilization yield and recovered activity) and the stability of the immobilized enzymes. According to proteomic studies, His-clusters enable a different enzyme orientation as compared to His-tag. Finally, these oriented heterogeneous biocatalysts are implemented in batch reactions, demonstrating that the stability achieved by an optimized orientation translates into increased operational stability.

Proteases immobilized on nanomaterials for biocatalytic, environmental and biomedical applications: Advantages and drawbacks

Proteases have gained significant scientific and industrial interest due to their unique biocatalytic characteristics and broad-spectrum applications in different industries. The development of robust nanobiocatalytic systems by attaching proteases onto various nanostructured materials as fascinating and novel nanocarriers has demonstrated exceptional biocatalytic performance, substantial stability, and ease of recyclability over multiple reaction cycles under different chemical and physical conditions. Proteases immobilized on nanocarriers may be much more resistant to denaturation caused by extreme temperatures or pH values, detergents, organic solvents, and other protein denaturants than free enzymes. Immobilized proteases may present a lower inhibition. The use of non-porous materials in the immobilization prevents diffusion and steric hindrances during the binding of the substrate to the active sites of enzymes compared to immobilization onto porous materials; when using very large or solid substrates, orientation of the enzyme must always be adequate. The advantages and problems of the immobilization of proteases on nanoparticles are discussed in this review. The continuous and batch reactor operations of nanocarrier-immobilized proteases have been successfully investigated for a variety of applications in the leather, detergent, biomedical, food, and pharmaceutical industries. Information about immobilized proteases on various nanocarriers and nanomaterials has been systematically compiled here. Furthermore, different industrial applications of immobilized proteases have also been highlighted in this review.

Magnetic core-shell cellulose system for the oriented immobilization of a recombinant β-galactosidase with a protein tag

The objective of this study was to immobilize a recombinant β-galactosidase (Gal) tagged with a cellulose-binding domain (CBD) onto a magnetic core-shell (CS) cellulose system. After 30 min of reaction, 4 U/capsule were immobilized (CS@Gal), resulting in levels of yield and efficiency exceeding 80 %. The optimal temperature for β-galactosidase-CBD activity increased from 40 to 50 °C following oriented immobilization. The inhibitory effect of galactose decreased in the enzyme reactions catalyzed by CS@Gal, and Mg2+ increased the immobilized enzyme activity by 40 % in the magnetic CS cellulose system. The relative enzyme activity of the CS@Gal was 20 % higher than that of the soluble enzyme activity after 20 min at 50 °C. The CS support and CS@Gal capsules exhibited an average size of 8 ± 1 mm, with the structure of the shell (alginate-pectin-cellulose) enveloping and isolating the magnetic core. The immobilized β-galactosidase-CBD within the magnetic CS cellulose system retained ∼80 % of its capacity to hydrolyze lactose from skim milk after 10 reuse cycles. This study unveils a novel and promising support for the oriented immobilization of recombinant β-galactosidase using a magnetic CS system and a CBD tag. This support facilitates β-galactosidase reuse and efficient separation, consequently enhancing the catalytic properties of the enzyme.

Genipin crosslinked porous chitosan beads as robust supports for β-galactosidase immobilization: Characterization, stability, and bioprocessing potential

This study aimed to modify the porosity of chitosan beads using Na2CO3 as a porogen agent and to crosslink them with genipin for the immobilization of β-galactosidase from Aspergillus oryzae. Immobilization was performed under four different pH conditions (4.5, 6.0, 7.5, and 9.0), resulting in biocatalysts named B4, B6, B7, and B9, respectively. The immobilized enzymes were characterized for immobilization parameters and stability, including thermal, pH, storage, and operational stability. The optimal conditions for the support were determined as 50 mM Na2CO3. The biocatalyst exhibited nearly 100 % retention of initial activity after 5 h of incubation at different pH conditions and showed improved thermal stability compared to the free enzyme across all pH conditions. After 50 cycles of lactose hydrolysis, all biocatalysts retained at least 71 % of their initial activity, with B6 retaining nearly 100 %. Scanning electron microscopy revealed structural modifications, particularly in B4, leading to weakened support structure after reuse. Continuous lactose hydrolysis showed increased productivity from 41.3 to 48.1 g L-1 h-1 for B6, with 78.1 % retention of initial capacity. All biocatalysts retained >95 % activity when stored at 4 °C for 20 weeks, highlighting their suitability for enzyme immobilization in continuous and discontinuous bioprocesses.

A systematic review about affinity tags for one-step purification and immobilization of recombinant proteins: integrated bioprocesses aiming both economic and environmental sustainability

The present study reviewed and discussed the promising affinity tags for one-step purification and immobilization of recombinant proteins. The approach used to structure this systematic review was The Preferred Reporting Items for Systematic Review and Meta-analysis (PRISMA) methodology. The Scopus and Web of Science databases were used to perform the bibliographic survey by which 267 articles were selected. After the inclusion/exclusion criteria and the screening process, from 25 chosen documents, we identified 7 types of tags used in the last 10 years, carbohydrate-binding module tag (CBM), polyhistidine (His-tag), elastin-like polypeptides (ELPs), silaffin-3-derived pentalysine cluster (Sil3k tag), N-acetylmuramidase (AcmA tag), modified haloalkane dehalogenase (HaloTag®), and aldehyde from a lipase polypeptide (Aldehyde tag). The most used bacterial host for expressing the targeted protein was Escherichia coli and the most used expression vector was pET-28a. The results demonstrated two main immobilization and purification methods: the use of supports and the use of self-aggregating tags without the need of support, depending on the tag used. Besides, the chosen terminal for cloning the tag proved to be very important once it could alter enzyme activity. In conclusion, the best tag for protein one-step purification and immobilization was CBM tag, due to the eco-friendly supports that can be provided from industry wastes, the fast immobilization with high specificity, and the reduced cost of the process.

Novel Approach for the Isolation and Immobilization of a Recombinant Transaminase: Applying an Advanced Nanocomposite System

The increasing application of recombinant enzymes demands not only effective and sustainable fermentation, but also highly efficient downstream processing and further stabilization of the enzymes by immobilization. In this study, a novel approach for the isolation and immobilization of His-tagged transaminase from Chromobacterium violaceum (CvTA) has been developed. A recombinant of CvTA was simultaneously isolated and immobilized by binding on silica nanoparticles (SNPs) with metal affinity linkers and additionally within poly(lactic acid) (PLA) nanofibers. The linker length and the nature of the metal ion significantly affected the enzyme binding efficiency and biocatalytic activity of CvTA-SNPs. The formation of PLA nanofibers by electrospinning enabled rapid embedding of CvTA-SNPs biocatalysts and ensured enhanced stability and activity. The developed advanced immobilization method reduces the time required for enzyme isolation, purification and immobilization by more than fourfold compared to a classical stepwise technique.

Hydrophobic cell surface display system of PETase as a sustainable biocatalyst for PET degradation

Remarkably, a hydrolase from Ideonella sakaiensis 201-F6, termed PETase, exhibits great potential in polyethylene terephthalate (PET) waste management due to it can efficiently degrade PET under moderate conditions. However, its low yield and poor accessibility to bulky substrates hamper its further industrial application. Herein a multigene fusion strategy is introduced for constructing a hydrophobic cell surface display (HCSD) system in Escherichia coli as a robust, recyclable, and sustainable whole-cell catalyst. The truncated outer membrane hybrid protein FadL exposed the PETase and hydrophobic protein HFBII on the surface of E. coli with efficient PET accessibility and degradation performance. E. coli containing the HCSD system changed the surface tension of the bacterial solution, resulting in a smaller contact angle (83.9 ± 2° vs. 58.5 ± 1°) of the system on the PET surface, thus giving a better opportunity for PETase to interact with PET. Furthermore, pretreatment of PET with HCSD showed rougher surfaces with greater hydrophilicity (water contact angle of 68.4 ± 1° vs. 106.1 ± 2°) than the non-pretreated ones. Moreover, the HCSD system showed excellent sustainable degradation performance for PET bottles with a higher degradation rate than free PETase. The HCSD degradation system also had excellent stability, maintaining 73% of its initial activity after 7 days of incubation at 40°C and retaining 70% activity after seven cycles. This study indicates that the HCSD system could be used as a novel catalyst for efficiently accelerating PET biodegradation.

Co-Immobilizing Two Glycosidases Based on Cross-Linked Enzyme Aggregates to Enhance Enzymatic Properties for Achieving High Titer Icaritin Biosynthesis

Icaritin is a rare and high-value isopentane flavonoid compound with remarkable activities. Increasing yields while reducing cost has been a great challenge in icaritin production. Herein, we first reported a high titer icaritin biosynthesis strategy from epimedin C through co-immobilizing α-l-rhamnosidase (Rha1) and β-glucosidase (Glu4) using cross-linked enzyme aggregates (CLEAs). The created CLEAs exhibited excellent performances in terms of catalytic activity, thermal stability, pH stability, and reusability. Notably, Rha1-CLEAs (K_i: 1 M) and Glu4-CLEAs (K_i: 0.1 M) were more tolerant to sugars (glucose or rhamnose) than free enzymes (0.1 M for Rha1 and 0.007 M for Glu4) by immobilization, achieving the highest icaritin productivity under the highest substrate concentration ever reported. Finally, about 34.24 g/L icaritin could be obtained from 100 g/L epimedin C within 8 h, indicating the great potential for industrialization. This study also provides a promising strategy for the low-cost production of other high-value aglycone compounds by solving poor stability and sugar inhibition of glycosidase.