S-Layer-Based Nanocomposites for Industrial Applications

Display of porcine epidemic diarrhea virus spike protein B-cell linear epitope on Lactobacillus mucosae G01 S-layer surface induce a robust immunogenicity in mice

The Porcine epidemic diarrhea virus (PEDV) presents a substantial risk to the domestic pig industry, resulting in extensive and fatal viral diarrhea among piglets. Recognizing the mucosal stimulation triggered by PEDV and harnessing the regulatory impact of lactobacilli on intestinal function, we have developed a lactobacillus-based vaccine that is carefully designed to elicit a strong mucosal immune response. Through bioinformatics analysis, we examined PEDV S proteins to identify B-cell linear epitopes that meet the criteria of being non-toxic, soluble, antigenic, and capable of neutralizing the virus. In this study, a genetically modified strain of Lactobacillus mucosae G01 (L.mucosae G01) was created by utilizing the S layer protein (SLP) as a scaffold for surface presentation. Chimeric immunodominant epitopes with neutralizing activity were incorporated at various sites on SLP. The successful expression of SLP chimeric immunodominant epitope 1 on the surface of L.mucosae G01 was confirmed through indirect immunofluorescence and transmission electron microscopy, revealing the formation of a transparent membrane. The findings demonstrate that the oral administration of L.mucosae G01, which expresses the SLP chimeric immunodominant gene epitope1, induces the production of secreted IgA in the intestine and feces of mice. Additionally, there is an elevation in IgG levels in the serum. Moreover, the levels of cytokines IL-2, IL-4, IFN-γ, and IL-17 are significantly increased compared to the negative control group. These results suggest that L. mucosae G01 has the ability to deliver exogenous antigens and elicit a specific mucosal immune response against PEDV. This investigation presents new possibilities for immunoprophylaxis against PEDV-induced diarrhea.

Catalytic Performance in Nitroarene Reduction of Nanocatalyst Based on Noble Metal Nanoparticles Supported on Polymer/s-Layer Protein Hybrids

We present a novel bionanocatalyst fabricated by the adsorption-reduction of metal ions on a polyurethane/S-layer protein biotemplate. The bioinspired support was obtained by the adsorption of S-layer proteins (isolated from Lentilactobacillus kefiri) on polyurethane particles. Silver and platinum nanoparticles were well-loaded on the surface of the support after the combination with metallic salts and reduction with H2 at room temperature. Transmission electron microscopy analysis revealed the strawberry-like morphology of the bionanocatalysts with a particle size, dn, of 2.39 nm for platinum and 9.60 nm for silver. Both systems catalyzed the hydrogenation of p-nitrophenol to p-aminophenol with high efficiency in water at mild conditions in the presence of NaBH4. Three different amounts of bionanocatalyst were tested, and in all cases, conversions between 97 and 99% were observed. The catalysts displayed excellent recyclability over ten cycles, and no extensive damage in their nanostructure was noted after them. The bionanocatalysts were stable during their production, storage, and use, thanks to the fact that the biosupport provides an effective driving force in the formation and stabilization of the metallic nanoparticles. The successful bioinspired production strategy and the good catalytic ability of the systems are encouraging in the search for nontoxic, simple, clean, and eco-friendly procedures for the synthesis and exploitation of nanostructures.

A Genetically Engineered, Chain Mail-Like Nanostructured Protein Material with Increased Fatigue Resistance and Enhanced Self-Healing

Protein-based nanostructured materials are being developed for many biomedical and nanotechnological applications. Despite their many desirable features, protein materials are highly susceptible to disruption by mechanical stress and fatigue. This study is aimed to increase fatigue resistance and enhance self-healing of a natural protein-based supramolecular nanomaterial through permanent genetic modification. The authors envisage the conversion of a model nanosheet, formed by a regular array of noncovalently bound human immunodeficiency virus capsid protein molecules, into a supramolecular "chain mail." Rationally engineered mutations allow the formation of a regular network of disulfide bridges in the protein lattice. This network links each molecule in the lattice to each adjacent molecule through one covalent bond, analogous to the rivetting of interlinked iron rings in the chain mail of a medieval knight. The engineered protein nanosheet shows greatly increased thermostability and resistance to mechanical stress and fatigue in particular, as well as enhanced self-healing, without undesirable stiffening compared to the original material. The results provide proof of concept for a genetic design to permanently increase fatigue resistance and enhance self-healing of protein-based nanostructured materials. They also provide insights into the molecular basis for fatigue of protein materials.

S-Layer Ultrafiltration Membranes

Monomolecular arrays of protein subunits forming surface layers (S-layers) are the most common outermost cell envelope components of prokaryotic organisms (bacteria and archaea). Since S-layers are periodic structures, they exhibit identical physicochemical properties for each constituent molecular unit down to the sub-nanometer level. Pores passing through S-layers show identical size and morphology and are in the range of ultrafiltration membranes. The functional groups on the surface and in the pores of the S-layer protein lattice are accessible for chemical modifications and for binding functional molecules in very precise fashion. S-layer ultrafiltration membranes (SUMs) can be produced by depositing S-layer fragments as a coherent (multi)layer on microfiltration membranes. After inter- and intramolecular crosslinking of the composite structure, the chemical and thermal resistance of these membranes was shown to be comparable to polyamide membranes. Chemical modification and/or specific binding of differently sized molecules allow the tuning of the surface properties and molecular sieving characteristics of SUMs. SUMs can be utilized as matrices for the controlled immobilization of functional biomolecules (e.g., ligands, enzymes, antibodies, and antigens) as required for many applications (e.g., biosensors, diagnostics, enzyme- and affinity-membranes). Finally, SUM represent unique supporting structures for stabilizing functional lipid membranes at meso- and macroscopic scale.

Organizing Multi-Enzyme Systems into Programmable Materials for Biocatalysis

Significant advances in enzyme discovery, protein and reaction engineering have transformed biocatalysis into a viable technology for the industrial scale manufacturing of chemicals. Multi-enzyme catalysis has emerged as a new frontier for the synthesis of complex chemicals. However, the in vitro operation of multiple enzymes simultaneously in one vessel poses challenges that require new strategies for increasing the operational performance of enzymatic cascade reactions. Chief among those strategies is enzyme co-immobilization. This review will explore how advances in synthetic biology and protein engineering have led to bioinspired co-localization strategies for the scaffolding and compartmentalization of enzymes. Emphasis will be placed on genetically encoded co-localization mechanisms as platforms for future autonomously self-organizing biocatalytic systems. Such genetically programmable systems could be produced by cell factories or emerging cell-free systems. Challenges and opportunities towards self-assembling, multifunctional biocatalytic materials will be discussed.