Novel Cell-Inorganic Hybrid Catalytic Interfaces with Enhanced Enzymatic Activity and Stability for Sensitive Biosensing of Paraoxon

Purified protein glutaminase from Chryseobacterium proteolyticum enhances the properties of wheat gluten

Protein glutaminase (PG), originating from Chryseobacterium proteolyticum, can catalyze the deamidation of glutamine residues in plant proteins into glutamic acid, thus enhancing its functional properties. However, the low yield of PG limits its industrial production. In this study, the yield of PG in C. proteolyticum TM1040 increased by 121 %, up to 7.30 U/mL in a 15 L fermenter after medium optimization. Subsequently, purified PG was obtained by cation exchange chromatography (CEX) coupled with hydrophobic interaction chromatography (HIC). The degree of deamidation (DD) of wheat gluten after purified PG deamidation was 87.11 %, which is superior to chemical deamidation in safety and DD. The emulsifying and foaming properties of deamidated wheat gluten were 2.67 and 18.86 times higher, and the water- and oil-holding properties were 4.23 and 18.77 times higher, respectively. The deamidated wheat gluten with enhanced functional properties was used to improve the flavor and texture in baking cakes.

Biominerals and Bioinspired Materials in Biosensing: Recent Advancements and Applications

Inspired by nature's remarkable ability to form intricate minerals, researchers have unlocked transformative strategies for creating next-generation biosensors with exceptional sensitivity, selectivity, and biocompatibility. By mimicking how organisms orchestrate mineral growth, biomimetic and bioinspired materials are significantly impacting biosensor design. Engineered bioinspired materials offer distinct advantages over their natural counterparts, boasting superior tunability, precise controllability, and the ability to integrate specific functionalities for enhanced sensing capabilities. This remarkable versatility enables the construction of various biosensing platforms, including optical sensors, electrochemical sensors, magnetic biosensors, and nucleic acid detection platforms, for diverse applications. Additionally, bioinspired materials facilitate the development of smartphone-assisted biosensing platforms, offering user-friendly and portable diagnostic tools for point-of-care applications. This review comprehensively explores the utilization of naturally occurring and engineered biominerals and materials for diverse biosensing applications. We highlight the fabrication and design strategies that tailor their functionalities to address specific biosensing needs. This in-depth exploration underscores the transformative potential of biominerals and materials in revolutionizing biosensing, paving the way for advancements in healthcare, environmental monitoring, and other critical fields.

Construction of bacterial laccase displayed on the microbial surface for ultrasensitive biosensing of phenolic pollutants with nanohybrids-enhanced performance

Although bacterial laccase (BLac) has many advantages including short fermentation period and adaptable activity to wide temperature and pH ranges, it is of challenge and significance to apply BLac to the biosensors, due to the intracellular secretion and poor electron transfer efficiency of BLac. Here, cell surface-displayed BLac (CSDBLac) was successfully constructed as whole-cell biocatalyst through microbial surface display technology, eliminating the mass transfer restriction and laborious purification steps. Meanwhile, MXenes/polyetherimide-multiwalled carbon nanotubes (MXenes/PEI-MWCNTs) nanohybrids were designed to immobilize CSDBLac and improve their electrochemical activity. Then, an electrochemical biosensor was successfully constructed to detect common phenolic pollutants (catechol and hydroquinone) by the co-immobilization of CSDBLac and MXenes/PEI-MWCNTs nanohybrids onto a glassy carbon electrode. Subsequently, it was successfully applied to the water samples assay with good reliability and repeatability. This work innovatively used BLac and nanohybrid as the core elements of biosensor, which not only effectively solved the application bottleneck of BLac on biosensors, but also dramatically promote the electro transfer efficiency between whole-cell biocatalyst and electrode. This method is of profound meanings for significantly improving the performance of phenolic biosensors and other biosensors from the origin.

Recent Advancements in Enzyme‐Incorporated Nanomaterials: Synthesis, Mechanistic Formation and Applications

Over the past decade, nanotechnology has been developed and employed across various entities. Among the numerous nanostructured material types, enzyme‐incorporated nanomaterials have shown great potential in various fields, as an alternative to biologically derived as well as synthetically developed hybrid structures. The mechanism of incorporating enzyme onto a nanostructure depends on several factors including the method of immobilization, type of nanomaterial, as well as operational and environmental conditions. The prospects of enzyme‐incorporated nanomaterials have shown promising results across various applications, such as biocatalysts, biosensors, drug therapy, and wastewater treatment. This is due to their excellent ability to exhibit chemical and physical properties such as high surface‐to‐volume ratio, recovery and/or reusability rates, sensitivity, response scale, and stable catalytic activity across wide operating conditions. In this review, the evolution of enzyme‐incorporated nanomaterials along with their impact on our society due to its state‐of‐the‐art properties, and its significance across different industrial applications are discussed. In addition, the weakness and future prospects of enzyme‐incorporated nanomaterials were also discussed to guide scientists for futuristic research and development in this field.

Microbial whole-cell biosensors: Current applications, challenges, and future perspectives

Microbial Whole-Cell Biosensors (MWCBs) have seen rapid development with the arrival of 21st century biological and technological capabilities. They consist of microbial species which produce, or limit the production of, a reporter protein in the presence of a target analyte. The quantifiable signal from the reporter protein can be used to determine the bioavailable levels of the target analyte in a variety of sample types at a significantly lower cost than most widely used and well-established analytical instrumentation. Furthermore, the versatile and robust nature of MWCBs shows great potential for their use in otherwise unavailable settings and environments. While MWCBs have been developed for use in biomedical, environmental, and agricultural monitoring, they still face various challenges before they can transition from the laboratory into industrialized settings like their enzyme-based counterparts. In this comprehensive and critical review, we describe the underlying working principles of MWCBs, highlight developments for their use in a variety of fields, detail challenges and current efforts to address them, and discuss exciting implementations of MWCBs helping redefine what is thought to be possible with this expeditiously evolving technology.

Cobalt Phosphate Nanocrystals: A Catalase-Like Nanozyme and In Situ Enzyme-Encapsulating Carrier for Efficient Chemoenzymatic Synthesis of α-Keto Acid

Chemoenzymatic catalysis combining the traits of chemical and enzymatic catalysis provides tremendous possibilities for the design of biosynthetic pathways utilizing inorganic catalysts and enzymes. However, the efficiency of chemoenzymatic catalysis is usually governed by the synergy and compatibility of the two catalysts. Here, we report for the first time the catalase-like activity of cobalt phosphate nanocrystals (CoPs). By a one-pot biomimetic mineralization with CoPs and l-amino acid oxidase (LAAO) under a mild condition, we have fabricated a hybrid nanobiocatalyst, LAAO@CoPs, for the chemoenzymatic synthesis of α-keto acid. The as-fabricated nanobiocatalyst with directly contacted catalytic sites of the enzyme and nanozyme maximizes the substrate channeling effects for in situ chemical decomposition of the oxidative intermediate, H₂O₂, during the enzymatic oxidation of l-tryptophan (l-Trp), thus minimizing the H₂O₂ accumulation and byproduct generation. Benefiting from the superiority of LAAO@CoPs, complete conversion (100.0%) of l-Trp to indole pyruvic acid is achieved, over two times higher than the yield of the free LAAO system (47.6%). Meanwhile, LAAO@CoPs show high stabilities against heat and proteolytic treatments. This work offers a new design approach for constructing a high-performance nanobiocatalyst for cascade reactions, especially for those systems with toxic or reactive intermediates.

Improving the anode performance of microbial fuel cell with carbon nanotubes supported cobalt phosphate catalyst

Microbial fuel cell (MFC) is a sustainable technology that can convert waste to energy by harnessing the power of exoelectrogenic bacteria. However, the poor biocompatibility and low electrocatalytic activities of surface usually cause weak bacterial adhesion and low electron transfer efficiency, which seriously hampers the development of MFCs. Herein, a novel carbon nanotube supported cobalt phosphate (CNT/Co-Pi) electrode is fabricated by assembling CNTs on carbon cloth, followed by the electrodeposition of Co-Pi catalyst. The deposited amorphous Co-Pi thin film contains phosphate and the cobalt ions of multiple oxidation states. The hydrophilic phosphate can promote the adhesion of microorganisms on electrode. The strong conversion ability of multiple states of cobalt offers excellent electrocatalytic activity for the electron transfer across biotic/abiotic interface. Therefore, the highly conductive CNTs substrate, along with the Co-Pi catalyst, provide an effective electron transfer between the electrogenic bacteria and the electrode, which endows MFC high power densities up to 1200 mW m^-2. Our work has demonstrated for the first time that CNT/Co-Pi catalyst can promote the interfacial electron transfer between electrogenic bacteria and electrode, and highlighted the application potentials of Co-Pi as an anode catalyst for the fabrication of high performance MFC anodes.

Artificial Bioaugmentation of Biomacromolecules and Living Organisms for Biomedical Applications

The synergistic union of nanomaterials with biomaterials has revolutionized synthetic chemistry, enabling the creation of nanomaterial-based biohybrids with distinct properties for biomedical applications. This class of materials has drawn significant scientific interest from the perspective of functional extension via controllable coupling of synthetic and biomaterial components, resulting in enhancement of the chemical, physical, and biological properties of the obtained biohybrids. In this review, we highlight the forefront materials for the combination with biomacromolecules and living organisms and their advantageous properties as well as recent advances in the rational design and synthesis of artificial biohybrids. We further illustrate the incredible diversity of biomedical applications stemming from artificially bioaugmented characteristics of the nanomaterial-based biohybrids. Eventually, we aim to inspire scientists with the application horizons of the exciting field of synthetic augmented biohybrids.

Preparation of a Copper Polyphosphate Kinase Hybrid Nanoflower and Its Application in ADP Regeneration from AMP

In this research article, we reported a self-assembly approach to prepare a copper polyphosphate kinase 2 hybrid nanoflower and established a cofactor ADP regeneration system from AMP using the nanoflower. First, the structure of the hybrid nanoflower was confirmed by scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy, which indicated the successful loading of the enzyme in the hybrid nanoflower. Moreover, compared to the free enzyme, the hybrid nanoflower exhibited a better performance in ADP production and possessed wider catalytic pH and temperature ranges as well as improved storage stability. The hybrid nanoflower also exhibited well reusability, preserving 71.7% of initial activity after being used for ten cycles. In addition, the phosphorylation of glucose was conducted by utilizing ADP-dependent glucokinase coupled with the ADP regeneration system, in which the hybrid nanoflower was used for regenerating ADP from AMP. It was observed that the ADP regeneration system operated effectively at a very small amount of AMP. Thus, the hybrid nanoflower had great application potential in industrial catalytic processes that were coupled with ADP-dependent enzymes.

Recent Advances in Enzyme-Nanostructure Biocatalysts with Enhanced Activity

Owing to their unique physicochemical properties and comparable size to biomacromolecules, functional nanostructures have served as powerful supports to construct enzyme-nanostructure biocatalysts (nanobiocatalysts). Of particular importance, recent years have witnessed the development of novel nanobiocatalysts with remarkably increased enzyme activities. This review provides a comprehensive description of recent advances in the field of nanobiocatalysts, with systematic elaboration of the underlying mechanisms of activity enhancement, including metal ion activation, electron transfer, morphology effects, mass transfer limitations, and conformation changes. The nanobiocatalysts highlighted here are expected to provide an insight into enzyme–nanostructure interaction, and provide a guideline for future design of high-efficiency nanobiocatalysts in both fundamental research and practical applications.

Displaying of acetylcholinesterase mutants on surface of yeast for ultra-trace fluorescence detection of organophosphate pesticides with gold nanoclusters

Acetylcholinesterase (AChE) has been widely applied on the enzyme inhibition-based detection of organophosphate pesticides (OPs). To improve the sensitivity of fluorometric OPs assay, great efforts were made to change the fluorometric probes or analytical strategies rather than improve the sensitivity of AChE towards OPs. In this work, AChE wild-type (WT) and mutants (E69Y and E69Y/F330L) from Drosophila were successfully displayed on the surface of yeast through a-agglutinin-mediated microbial surface display system. The location of AChE on yeast surface was confirmed by immunofluorescence analysis. Further, a fluorescence OPs detection method was developed by combining yeast surface-displayed AChE mutants and protein-directed electronegative fluorescent gold nanoclusters (Au NCs). Yeast surface-displayed AChE can catalyze the hydrolysis of acetylthiocholine to produce thiocholine. The electropositive thiocholine can not only bind with AuNCs by Au-S bond but also absorb Au NCs by the electrostatic interaction, leading to the aggregation of AuNCs and corresponding fluorescence quenching. When AChE was incubated with paraoxon, a typical model of OPs, the activity of AChE was inhibited and the thiocholine-induced aggregation of AuNCs was reduced. The fluorescence assay based on Au NCs and yest-AChE-E69Y/F330L exhibited the ultra-sensitivity for ultra-trace OPs and 2-6 orders of magnitude lower detection limit (3.3 × 10^-14 M) than those of AChE-WT-based method and other reported methods. In addition, the proposed method showed excellent reliability for the real samples assay. This work would provide an alternative strategy for the improvement of bio-analysis at its source.

Tackling the Challenges of Enzymatic (Bio)Fuel Cells

The ever-increasing demands for clean and sustainable energy sources combined with rapid advances in biointegrated portable or implantable electronic devices have stimulated intensive research activities in enzymatic (bio)fuel cells (EFCs). The use of renewable biocatalysts, the utilization of abundant green, safe, and high energy density fuels, together with the capability of working at modest and biocompatible conditions make EFCs promising as next generation alternative power sources. However, the main challenges (low energy density, relatively low power density, poor operational stability, and limited voltage output) hinder future applications of EFCs. This review aims at exploring the underlying mechanism of EFCs and providing possible practical strategies, methodologies and insights to tackle these issues. First, this review summarizes approaches in achieving high energy densities in EFCs, particularly, employing enzyme cascades for the deep/complete oxidation of fuels. Second, strategies for increasing power densities in EFCs, including increasing enzyme activities, facilitating electron transfers, employing nanomaterials, and designing more efficient enzyme-electrode interfaces, are described. The potential of EFCs/(super)capacitor combination is discussed. Third, the review evaluates a range of strategies for improving the stability of EFCs, including the use of different enzyme immobilization approaches, tuning enzyme properties, designing protective matrixes, and using microbial surface displaying enzymes. Fourth, approaches for the improvement of the cell voltage of EFCs are highlighted. Finally, future developments and a prospective on EFCs are envisioned.

Surface display of organophosphorus-degrading enzymes on the recombinant spore of Bacillus subtilis

Organophosphorus-degrading enzymes show high hydrolysis efficiency and provide an environmentally friendly solution to the pollution of organophosphorus compound. However, poor enzyme stability and tedious purification process have limited practical applications. Spore-based display system can provide many advantages, such as safety, low cost, easy preparation and high resistance to harsh conditions. Recently, we have constituted the recombinant spore displaying organophosphorus hydrolase and organophosphorus acid anhydrolase. In the spore display systems, recombinant spores could be reliably produced and normal sporulation was not affected; the activities of recombinant spores were 15.81 and 10.67 U/mg spores (dry weight) respectively; furthermore, the recombinant spores exhibited significantly enhanced resistance to various harsh conditions compared to free-form enzymes. These results indicated that the spore display could contribute to the practical application of organophosphorus-degrading enzymes and provide a promising solution to bioremediation of organophosphorus compounds.

Tuned Amperometric Detection of Reduced β-Nicotinamide Adenine Dinucleotide by Allosteric Modulation of the Reductase Component of the p-Hydroxyphenylacetate Hydroxylase Immobilized within a Redox Polymer

We report the fabrication of an amperometric NADH biosensor system that employs an allosterically modulated bacterial reductase in an adapted osmium(III)-complex-modified redox polymer film for analyte quantification. Chains of complexed Os(III) centers along matrix polymer strings make electrical connection between the immobilized redox protein and a graphite electrode disc, transducing enzymatic oxidation of NADH into a biosensor current. Sustainable anodic signaling required (1) a redox polymer with a formal potential that matched the redox switch of the embedded reductase and avoided interfering redox interactions and (2) formation of a cross-linked enzyme/polymer film for stable biocatalyst entrapment. The activity of the chosen reductase is enhanced upon binding of an effector, i.e. p-hydroxy-phenylacetic acid ( p-HPA), allowing the acceleration of the substrate conversion rate on the sensor surface by in situ addition or preincubation with p-HPA. Acceleration of NADH oxidation amplified the response of the biosensor, with a 1.5-fold increase in the sensitivity of analyte detection, compared to operation without the allosteric modulator. Repetitive quantitative testing of solutions of known NADH concentration verified the performance in terms of reliability and analyte recovery. We herewith established the use of allosteric enzyme modulation and redox polymer-based enzyme electrode wiring for substrate biosensing, a concept that may be applicable to other allosteric enzymes.

Phage capsid protein-directed MnO2 nanosheets with peroxidase-like activity for spectrometric biosensing and evaluation of antioxidant behaviour

Small molecular weight proteins (5.21 kDa) were used as bio-templates to synthesize MnO₂ nanosheets (NSs). This work will open up a protein-directed avenue to synthesize 2D morphology. Further, the as-prepared MnO₂ NSs showed intrinsic peroxidase-like activity and were then applied for glucose detection and evaluation of antioxidant behaviours of typical antioxidants.

Recent advances in biomolecule immobilization based on self-assembly: organic-inorganic hybrid nanoflowers and metal-organic frameworks as novel substrates

In the past few years, the immobilization of biomolecules on hybrid nanoflowers and metal-organic frameworks (MOFs) via self-assembly synthesis has received much attention due to its simplicity, high efficiency, and a bright prospect of enhancing the stability, activity and even selectivity of biomolecules compared to conventional immobilization methods. In the synthesis of organic-inorganic hybrid nanoflowers, biomolecules used as organic components are simply mixed with metal ions which act as inorganic components to form flower-like nanocomposites, while in the self-assembly process of encapsulating biomolecules in MOFs (biomolecule@MOF composites), the biomolecules just need to be added to the precursor mixtures of MOFs, in which the biomolecules are therefore embedded in MOF crystals with small pores. In this review, we focus on the recent advances of these composites, especially in the synthesis strategies, mechanism and applications in biosensors, biomedicine, pollutant disposal, and industrial biocatalysis, and future perspectives are discussed as well.

Rational design of engineered microbial cell surface multi-enzyme co-display system for sustainable NADH regeneration from low-cost biomass

As an important cofactor, NADH is essential for most redox reactions and biofuel cells. However, supply of exogenous NADH is challenged, due to the low production efficiency and high cost of NADH regeneration system, as well as low stability of NADH. Here, we constructed a novel cell surface multi-enzyme co-display system with ratio- and space-controllable manner as exogenous NADH regeneration system for the sustainable NADH production from low-cost biomass. Dockerin-fused glucoamylase (GA) and glucose dehydrogenase (GDH) were expressed and assembled on the engineered bacterial surfaces, which displayed protein scaffolds with various combinations of different cohesins. When the ratio of GA and GDH was 3:1, the NADH production rate of the whole-cell biocatalyst reached the highest level using starch as substrate, which was three times higher than that of mixture of free enzymes, indicating that the highly ordered spatial organization of enzymes would promote reactions, due to the ratio of enzymes and proximity effect. To confirm performance of the established NADH regeneration system, the highly efficient synthesis of L-lactic acid (L-LA) was conducted by the system and the yield of L-LA (16 g/L) was twice higher than that of the mixture of free enzymes. The multi-enzyme co-display system showed good stability in the cyclic utilization. In conclusion, the novel sustainable NADH system would provide a cost-effective strategy to regenerate cofactor from low-cost biomass.

Redesigning of Microbial Cell Surface and Its Application to Whole-Cell Biocatalysis and Biosensors

Microbial cell surface display technology can redesign cell surfaces with functional proteins and peptides to endow cells some unique features. Foreign peptides or proteins are transported out of cells and immobilized on cell surface by fusing with anchoring proteins, which is an effective solution to avoid substance transfer limitation, enzyme purification, and enzyme instability. As the most frequently used prokaryotic and eukaryotic protein surface display system, bacterial and yeast surface display systems have been widely applied in vaccine, biocatalysis, biosensor, bioadsorption, and polypeptide library screening. In this review of bacterial and yeast surface display systems, different cell surface display mechanisms and their applications in biocatalysis as well as biosensors are described with their strengths and shortcomings. In addition to single enzyme display systems, multi-enzyme co-display systems are presented here. Finally, future developments based on our and other previous reports are discussed.