Genetically Fused T4L Acts as a Shield in Covalent Enzyme Immobilisation Enhancing the Rescued Activity

Biosilica-coated carbonic anhydrase displayed on Escherichia coli: A novel design approach for efficient and stable biocatalyst for CO2 sequestration

A robust and stable carbonic anhydrase (CA) system is indispensable for effectively sequestering carbon dioxide to mitigate climate change. While microbial surface display technology has been employed to construct an economically promising cell-displayed CO2-capturing biocatalyst, the displayed CA enzymes were prone to inactivation due to their low stability in harsh conditions. Herein, drawing inspiration from biomineralized diatom frustules, we artificially introduced biosilica shell materials to the CA macromolecules displayed on Escherichia coli surfaces. Specifically, we displayed a fusion of CA and the diatom-derived silica-forming Sil3K peptide (CA-Sil3K) on the E. coli surface using the membrane anchor protein Lpp-OmpA linker. The displayed CA-Sil3K (dCA-Sil3K) fusion protein underwent a biosilicification reaction under mild conditions, resulting in nanoscale self-encapsulation of the displayed enzyme in biosilica. The biosilicified dCA-Sil3K (BS-dCA-Sil3K) exhibited improved thermal, pH, and protease stability and retained 63 % of its initial activity after ten reuses. Additionally, the BS-dCA-Sil3K biocatalyst significantly accelerated the CaCO3 precipitation rate, reducing the time required for the onset of CaCO3 formation by 92 % compared to an uncatalyzed reaction. Sedimentation of BS-dCA-Sil3K on a membrane filter demonstrated a reliable CO2 hydration application with superior long-term stability under desiccation conditions. This study may open new avenues for the nanoscale-encapsulation of enzymes with biosilica, offering effective strategies to provide efficient, stable, and economic cell-displayed biocatalysts for practical applications.

Novel Strategies for Spatiotemporal and Controlled BMP-2 Delivery in Bone Tissue Engineering

Bone morphogenetic protein-2 (BMP-2) has been commercially approved by the Food and Drug Administration for use in bone defects and diseases. BMP-2 promotes osteogenic differentiation of mesenchymal stem cells. In bone tissue engineering, BMP-2 incorporated into scaffolds can be used for stimulating bone regeneration in organoid construction, drug testing platforms, and bone transplants. However, the high dosage and uncontrollable release rate of BMP-2 challenge its clinical application, mainly due to the short circulation half-life of BMP-2, microbial contamination in bone extracellular matrix hydrogel, and the delivery method. Moreover, in clinical translation, the requirement of high doses of BMP-2 for efficacy poses challenges in cost and safety. Based on these, novel strategies should ensure that BMP-2 is delivered precisely to the desired location within the body, regulating the timing of BMP-2 release to coincide with the bone healing process, as well as release BMP-2 in a controlled manner to optimize its therapeutic effect and minimize side effects. This review highlights improvements in bone tissue engineering applying spatiotemporal and controlled BMP-2 delivery, including molecular engineering, biomaterial modification, and synergistic therapy, aiming to provide references for future research and clinical trials.

Oriented multivalent silaffin-affinity immobilization of recombinant lipase on diatom surface: Reliable loading and high performance of biocatalyst

Microbial lipases are widely used biocatalysts; however, their functional surface immobilization should be designed for successful industrial applications. One of the unmet challenges is to develop a practical surface immobilization to achieve both high stability and activity of lipases upon the large loading. Herein, we present a silaffin-based multivalent design as a simple and oriented approach for Bacillus subtilis lipase A (LipA) immobilization on economic diatom biosilica matrix to yield highly-stable activity with reliable loading. Specifically, silaffin peptides Sil3H, Sil3K, and Sil3R, as monovalent or divalent genetic fusion tags, selectively immobilized LipA on biosilica surfaces. Sil3K peptide fusion to LipA termini most efficiently produced high catalytic activity upon immobilization. The activity was 70-fold greater than that of immobilized wild-type LipA. Compared to single fusion, the double Sil3K fusion displayed 1.7 higher enzymatic loading combined with high catalytic performances of LipA on biosilica surfaces. The multivalent immobilized LipA was distributed uniformly on biosilica surfaces. The biocatalyst was stable over a wide pH range with 98% retention activity after 10 reuses. The stabilized lipase fusion was compatible with laundry detergents, making it an attractive biocatalyst for detergent formulations. These findings demonstrate that multivalent surface immobilization is a plausible method for developing high-performance biocatalysts suitable for industrial biotechnological applications.

Enhanced bone regeneration via spatiotemporal and controlled delivery of a genetically engineered BMP-2 in a composite Hydrogel

Scaffolds functionalized with bone morphogenetic protein-2 (BMP-2) have shown great potential for bone regeneration. However, structural instability and the necessity for supra-physiological dose have thus far limited practical applications for BMP-2. Protein modification and site-specific covalent immobilization of BMP-2 to carrier materials might be optimal strategies to overcome these problems. Here, we report a broadly applicable strategy where the polyhistidine tag-T4 Lysozyme (His6-T4L) was genetically fused at the N-terminus of BMP-2 and used as a protein spacer, which on one hand enhanced protein solubility and stability, and on the other hand mediated site-specific covalent anchoring of BMP-2 upon binding to nickel-chelated nitrilotriacetic acid (Ni-NTA) microparticles (denoted as MPs-His6-T4L-BMP2) to further maximize its rescued activity. We also constructed a novel gelatin-based hydrogel that was crosslinked by transglutaminase (TG) and tannic acid (TA). This hydrogel, when incorporated with MPs-His6-T4L-BMP2, displayed excellent in-situ injectability, thermosensitivity, adhesiveness and improved mechanical properties. The effective loading mode led to a controlled and long-term sustained release of His6-T4L-BMP2, thereby resulting in enhancement of bone regeneration in a critical-sized bone defect. We believe that the protein modification strategy proposed here opens up new route not only for BMP-2 applications, but can be used to inform novel uses for other macromolecules.

Looking Back: A Short History of the Discovery of Enzymes and How They Became Powerful Chemical Tools

Enzymatic approaches to challenges in chemical synthesis are increasingly popular and very attractive to industry given their green nature and high efficiency compared to traditional methods. In this historical review we highlight the developments across several fields that were necessary to create the modern field of biocatalysis, with enzyme engineering and directed evolution at its core. We exemplify the modular, incremental, and highly unpredictable nature of scientific discovery, driven by curiosity, and showcase the resulting examples of cutting-edge enzymatic applications in industry.

Developing Multicompartment Biopolymer Hydrogel Beads for Tandem Chemoenzymatic One-Pot Process

Chemoenzymatic processes have been gaining interest to implement sustainable reaction steps or even create new synthetic routes. In this study, we combined Grubbs’ second-generation catalyst with pig liver esterase and conducted a chemoenzymatic one-pot process in a tandem mode. To address sustainability, we encapsulated the catalysts in biopolymer hydrogel beads and conducted the reaction cascade in an aqueous medium. Unfortunately, conducting the process in tandem led to increased side product formation. We then created core-shell beads with catalysts located in different compartments, which notably enhanced the selectivity towards the desired product compared to homogeneously distributing both catalysts within the matrix. Finally, we designed a specific large-sized bead with a diameter of 13.5 mm to increase the diffusion route of the Grubbs’ catalyst-containing shell. This design forced the ring-closing metathesis to occur first before the substrate could diffuse into the pig liver esterase-containing core, thus enhancing the selectivity to 75%. This study contributes to addressing reaction-related issues by designing specific immobilisates for chemoenzymatic processes.

Overcoming Water Insolubility in Flow: Enantioselective Hydrolysis of Naproxen Ester

Hydrolytic enantioselective cleavage of different racemic non-steroidal anti-inflammatory drugs (NSAIDs) ester derivatives has been studied. An engineered esterase form Bacillus subtilis (BS2m) significantly outperformed homologous enzymes from Halomonas elongata (HeE) and Bacillus coagulants (BCE) in the enantioselective hydrolysis of naproxen esters. Structural analysis of the three active sites highlighted key differences which explained the substrate preference. Immobilization of a chimeric BS2m-T4 lysozyme fusion (BS2mT4L1) was improved by resin screening achieving twice the recovered activity (22.1 ± 5 U/g) with respect to what had been previously reported, and was utilized in a packed bed reactor. Continuous hydrolysis of α-methyl benzene acetic acid butyl ester as a model substrate was easily achieved, albeit at low concentration (1 mM). However, the high degree of insolubility of the naproxen butyl ester resulted in a slurry which could not be efficiently bioconverted, despite the addition of co-solvents and lower substrate concentration (1 mM). Addition of Triton® X-100 to the substrate mix yielded 24% molar conversion and 80% e.e. at a 5 mM scale with 5 min residence time and sufficient retention of catalytic efficiency after 6 h of use.

Immobilized Biocatalysts

An application-related definition for immobilized enzymes was given by Chibata in 1978 […]