Search Results (295)

Volatile fatty acids (VFAs) are essential precursors in chemical synthesis for various chemicals, polymers, pharmaceuticals, and fragrance compounds. Acidogenic anaerobic digestion (or arrested methanogenesis) is a promising method to stabilize organic wastes and convert them to value-added products such as VFAs. However, the VFAs’ accumulation could in turn suppress the fermentation process through product inhibition and limit the titer of VFA in the digestate. Therefore, in situ separation and recovery of VFAs from the fermentate is crucial to constructing an effective continuous VFA-producing system. Recent research has been dedicated to addressing these issues and advancing the utilization of biobased VFAs, particularly through process-intensified strategies employing novel green solvents such as natural deep eutectic solvents. Furthermore, in situ conversion of VFAs into esters is another potential strategy for VFA removal. However, VFA esterification in an aqueous medium is challenging due to the abundant water driving the reaction toward hydrolysis. Recent advances in free or immobilized enzyme catalysis in solvents have demonstrated improved ester yield by providing a hydrophobic space for the esterification reaction in aqueous solution. In this review, we present an overview of critical aspects on the state-of-the-art of green solvent-based process intensification strategies, including feedstock selection and pretreatment, operating condition optimization, advances in membrane- and solvent-based recovery methods, and biocatalytic in situ esterification. Lastly, we provide perspectives toward cost-effective, continuous, high-solid, environmental-benign, and industrial-relevant VFA production applications. Full article

Hydrogel-based optical sensors have emerged as a versatile class of analytical materials that combine soft-matter processability, tunable network chemistry, and compatibility with luminescent, colorimetric, photonic, and hybrid transduction strategies. Progress in the field is driven not by a single sensing mechanism, but by the convergence of key advances in material functionalization, embedded selectivity, operation across diverse sample matrices, mechanical and analytical robustness, and usability beyond the laboratory. Current systems include framework-integrated, nanoparticle-doped, probe-functionalized, photonic-crystal, enzyme-immobilized, and device-coupled hydrogels, reflecting growing architectural diversity and application-oriented engineering. Selectivity has likewise advanced from basic interferent screening to recognition-specific, imprinted, and pattern-discriminative formats suited to complex environmental, food, biological, and wearable settings. Evidence of stability, reusability, and deformation tolerance further suggests that many platforms are moving beyond proof-of-concept demonstrations toward credible real-world operation. At the same time, translational priorities such as portability, smartphone readout, implantable and epidermal formats, and multifunctionality spanning antimicrobial action, adsorption, anti-counterfeiting, and device integration are becoming increasingly prominent. Together, these trends show that hydrogel-based optical sensing is maturing into a materially rich, application-responsive domain. The key challenge ahead is to unify materials design, selectivity control, durability, and deployability in standardized, reproducible, and clinically or environmentally credible sensing platforms. Full article

Steroid glycosides constitute an important class of bioactive molecules, yet their selective synthesis remains challenging. Here, we established a screening platform for nucleotide sugar-dependent glycosyltransferases (GTs) coupled with sucrose synthase (SuSy) for in situ UDP-glucose regeneration, enabling cost-efficient steroid glucosylation. A library of GTs comprising literature-derived enzymes and newly mined archaeal and fungal candidates was constructed using sequence filtering, AlphaFold3 modeling, and docking-guided prioritization. The resulting panel was screened against 31 structurally diverse steroids (androgens, estrogens, pregnanes, and corticosteroids) using crude Escherichia coli lysates as catalysts and UPLC-DAD, LC-MS and NMR analytics. YjiC and OleD glycosyltransferases emerged as the most promiscuous biocatalysts, while Sbaic7OGT and SgUGT74AC1_M7 displayed greater selectivity toward estrogens and selected testosterone derivatives. Product assignment for representative reactions was validated using authenticated reference standards or NMR (1D/2D) analysis, confirming regioisomeric estradiol monoglucosides (3-O- and 17-O-), estrone 3-O-glucoside, and an unexpected product diversification for 17α-testosterone by endogenous E. coli enzyme, where the major product was identified as a 6′-O-acetylated glucoside. Finally, SuSy-coupled cascades were applied in semi-preparative scale and evaluated under optimized conditions and co-immobilization formats. Full article

Hormones regulate numerous physiological processes and are essential for maintaining metabolic homeostasis. Accurate hormone quantification is crucial for the diagnosis and monitoring of endocrine and metabolic disorders. Electrochemical biosensors have recently emerged as promising platforms for hormone detection, offering simplicity, rapid response, cost-effectiveness, and high sensitivity compared to conventional techniques such as chromatography and mass spectrometry. This review summarizes the advances in electrochemical biosensors for detecting clinically relevant hormones, including cortisol, estrogen, progesterone, thyroid-stimulating hormone, parathyroid hormone, prolactin, and insulin, since 2010. Particular attention has been paid to developments in electrode modification strategies, including nanomaterials, redox enzymes, and novel recognition elements, which significantly improve the sensitivity and selectivity. These advances enable hormone detection at lower concentrations in various biological and environmental matrices. Despite these promising developments, challenges related to sensor stability, fabrication costs, and regeneration procedures limit their large-scale commercialization. Future research should focus on improving robustness, optimizing immobilization strategies, and integrating innovative materials to enhance the analytical performance. Continued collaboration among researchers, engineers, and healthcare professionals is essential. With ongoing technological progress, electrochemical biosensors are expected to play an important role in clinical diagnosis, point-of-care testing, and personalized medicine. Full article

This study presents a headset-type biofluorometric gas sensor incorporating a CMOS camera for continuous, non-invasive monitoring of transcutaneous ethanol from the ear canal. The sensor employs alcohol dehydrogenase (ADH) to catalyze the NAD⁺-to-NADH conversion during ethanol oxidation, enabling quantitative measurement through NADH fluorescence detection (λ_ex = 340 nm, λ_em = 490 nm). The integrated system comprises a wireless CMOS camera, an ADH-immobilized cotton mesh enzyme membrane, UV-LED excitation source, optical bandpass filters, and a dual convex lens assembly housed in a 3D-printed headset powered by a lithium battery. Key improvements include a 3.5-fold enhancement in fluorescence collection efficiency achieved through optimized dual convex lens configuration. Systematic screening of seven cotton mesh materials identified Iwatsuki cotton mesh as the optimal enzyme immobilization substrate, exhibiting minimal autofluorescence and 14.2-fold higher water retention capacity compared to H-PTFE membranes. The glutaraldehyde-crosslinked ADH-immobilized cotton mesh maintained enzymatic activity for over 45 min with a 10-fold improvement in signal-to-noise ratio. The system demonstrated a dynamic detection range spanning 10 ppb to 10 ppm for gaseous ethanol and exhibited high selectivity against interfering volatile organic compounds in skin gas, including methanol, acetaldehyde, formaldehyde, and acetone. Human experiments validated the system’s practical performance. Following alcohol consumption, subjects wore the device for 50 min while real-time fluorescence monitoring captured dynamic ethanol concentration changes in the ear canal. The dose-dependent fluorescence response—approximately 2-fold higher at 0.4 g/kg versus 0.04 g/kg alcohol intake—correlated well with calibration data. This headset-type biofluorometric sensor enables unrestrained continuous monitoring of ear canal ethanol, providing a novel wearable platform for alcohol metabolism assessment with potential applications in health monitoring and clinical research. Full article

Nano–bio hybrid catalysts have emerged as a promising platform for sustainable energy conversion by integrating the high selectivity of enzymes with the structural robustness and conductivity of nanomaterials. In recent years, the growing demand for clean energy technologies has driven the development of biohybrid systems capable of efficient electron transfer, enhanced catalytic activity, and improved operational stability. This review comprehensively discusses the design principles, mechanistic foundations, and performance metrics of enzyme–nanomaterial interfaces for energy-related applications. We first outline the fundamentals of enzymatic redox catalysis and the limitations of free enzymes in practical systems. Subsequently, we examine the functional roles of nanomaterials including carbon-based materials, metal and metal oxide nanoparticles, and two-dimensional platforms such as MXenes in facilitating enzyme immobilization and promoting direct or mediated electron transfer. Special emphasis is placed on engineering strategies at the bio–nano interface, including immobilization techniques, surface functionalization, and structural tuning to optimize catalytic efficiency. The review further highlights representative hybrid systems based on laccase, glucose oxidase, peroxidase, and hydrogenase enzymes, and evaluates their applications in biofuel cells, solar–bio hybrid systems, green oxidation reactions, and self-powered biosystems. Stability challenges, deactivation mechanisms, and enhancement strategies such as polymer coatings, cross-linking, and nanoconfinement are critically analyzed. Finally, emerging directions including artificial enzymes, AI-guided catalyst design, and self-healing bioelectrodes are discussed to provide a forward-looking perspective on next-generation sustainable bioelectrocatalytic systems. Full article

This study presents a highly efficient and sustainable biocatalytic platform for bisphenol A (BPA) bioremediation through the covalent immobilization of laccase onto hierarchically functionalized cotton fibers. The immobilization strategy involved selective periodate oxidation of cellulose, grafting a hexamethylenediamine (HMDA) spacer arm, and glutaraldehyde activation, ensuring stable covalent attachment. Characterization via FTIR, SEM, and BET confirmed successful surface modification and high enzyme loading, achieving an immobilization yield of 90.5%. The immobilized laccase (CT-DA-HMD-Lac) exhibited significantly enhanced performance compared to the free enzyme, with a two-fold increase in maximum reaction velocity (V_max) and a 75% improvement in catalytic efficiency of action (V_max/K_m). Furthermore, the biocatalyst demonstrated superior robustness, maintaining high activity across broader pH and temperature ranges, and retaining 75% of its initial activity after 15 consecutive reusability cycles. Storage stability was also markedly improved, with 83% activity retention after 60 days. Practical application in BPA degradation showed 85% removal efficiency within 300 min, a 2.4-fold increase in the degradation rate constant over the free enzyme. These results highlight functionalized cotton as a promising, cost-effective, and scalable support for advanced enzymatic wastewater treatment and the remediation of persistent endocrine-disrupting chemicals. Full article

Consolidated Bioprocessing (CBP) is a promising technology that integrates enzyme production, biomass hydrolysis, and sugars fermentation. However, CBP is underexplored from a process engineering point of view. Considering that cell recycling can increase process economic viability and that the selection of a bioreactor is a key factor to ensure process effectiveness, this study demonstrates the feasibility of recycling cells during sugarcane bagasse CBP by using magnetic immobilized enzyme producer yeast and a low shear stress vortex flow bioreactor. In the first step, Ca-alginate immobilized strains achieved good productivities (0.48 g/L/h) and 5.7 g/L of ethanol in only 12 h, but cell recovery was hindered by residual solids. To overcome this limitation, magnetic particles were incorporated into the spheres, allowing for rapid post-fermentation, maintaining ethanol production and productivity (6.1 g/L and 0.51 g/L/h). Three repeated batches were successful performed (producing an average of 5.5 g/L of ethanol, 0.46 g/L/h) with complete cell recovery from the remaining solid after biomass hydrolysis, maintaining high cell viability and bead integrity, highlighting the robustness of the immobilization strategy and the suitability of the bioreactor for the process. The successful cell recovery accomplished overcomes a fundamental limitation of bioprocesses carried out in the presence of solids. This strategy represents an important step for biorefineries development, with potential applicability to other bioprocesses using solid substrates. Full article

The accelerating global demand for sustainable energy, driven by population growth, industrialization, and environmental concerns, has intensified the search for renewable alternatives to fossil fuels. Biofuels, including bioethanol, biodiesel, biogas, and biohydrogen, offer a viable and practical pathway to reducing net carbon dioxide (CO₂) emissions. Yet, their large-scale production remains constrained by biomass recalcitrance, high pretreatment costs, and the enzyme-intensive nature of conversion processes. Recent advances in enzyme immobilization using magnetic nanoparticles (MNPs), covalent organic frameworks, metal–organic frameworks, and biochar have significantly improved enzyme stability, recyclability, and catalytic efficiency. Complementary strategies such as cross-linked enzyme aggregates, carrier-free immobilization, and site-specific attachment further reduce enzyme leaching and operational costs, particularly in lipase-mediated biodiesel synthesis. In addition to biocatalysis, nanozymes—nanomaterials exhibiting enzyme-like activity—are emerging as robust co-catalysts for biomass degradation and upgrading, although challenges in selectivity and environmental safety persist. Green synthesis approaches employing plant extracts, microbes, and agro-industrial wastes are increasingly adopted to produce eco-friendly nanomaterials and bio-derived supports aligned with circular economy principles. These functionalized materials have demonstrated promising performance in esterification, transesterification, and catalytic routes for biohydrogen generation. Technoeconomic and lifecycle assessments emphasize the need to balance catalyst complexity with environmental and economic sustainability. Multifunctional catalysts, process intensification strategies, and engineered thermostable enzymes are improving productivity. Looking forward, pilot-scale validation of green-synthesized nano- and biomaterials, coupled with appropriate regulatory frameworks, will be critical for real-world deployment. Full article

The development of efficient bioelectrodes requires suitable fabrication strategies, starting with the electrode material, which affects the electron transfer between the biocatalyst and the electrode surface. Then, selection and adjustment of the enzyme immobilization conditions are essential to enhance the performance of the bioelectrodes for their desirable utility. In this study, we report the fabrication of a high-performance bioelectrode using a one-step crosslinking of FAD-dependent glucose dehydrogenase (FAD-GDH) and thionine acetate as a redox mediator, with genipin serving as a natural, biocompatible crosslinker. Electrodes were manufactured on flexible polyester substrates using a direct printing technique, enabling reproducible and low-cost production. Among the tested crosslinkers, genipin significantly enhanced the catalytic performance of bioelectrodes. Comparative studies on graphite, silver, and gold electrode materials identified graphite as the most suitable due to its extended electroactive surface area. The developed bioelectrodes applied to glucose biosensing demonstrated a linear amperometric response to glucose in the range of 0.02–2 mM and 0.048–30 mM, covering clinically relevant concentrations. The application of artificial sweat confirmed high detection accuracy. These findings highlight the potential integration of genipin-based enzyme–mediator networks for future non-invasive sweat glucose monitoring platforms. Full article

The endocrine stress response is a valuable tool for evaluating how organisms cope with environmental challenges. However, selecting an appropriate matrix for measuring glucocorticoids (GCs) requires careful consideration of sample quality and accessibility. This study reveals that blood sampling affects plasma cortisol levels in the subterranean rodent Ctenomys talarum, with the effect being reversed shortly thereafter. To facilitate a non-invasive approach, an enzyme-linked immunosorbent assay (EIA) that had previously been validated for measuring plasma cortisol in C. talarum was evaluated to measure adrenocortical activity by analyzing fecal glucocorticoid metabolites (FGCs). Using this assay, we monitored the stress response during wild capture, transport to captivity, adrenocorticotropic hormone (ACTH) stimulation, and immobilization. This showed that FGC levels accurately reflect adrenal activation in these contexts. We also documented a relationship between reproductive seasonality and FGCs. Finally, we provide evidence for a relationship between adrenal activity and behavior. Our results suggest that when considering plasma GCs for the assessment of acute stress, it is crucial to understand the magnitude and timing of the effects of blood sampling on the stress state of organisms. The validation of FGC measurement in C. talarum provides a new option for advancing ecophysiological studies in both the wild and captivity. Full article

Enzymatic electrochemical sensors are promising for real-time glucose monitoring due to their high sensitivity and continuous detection capability. In this work, a magnetic Fe₃O₄@MXene nanocomposite was synthesized hydrothermally. The introduction of Fe₃O₄ not only reduced MXene’s inherent negative surface charge, improving interaction with glucose oxidase (GOD), but also formed a porous structure that enhances enzyme immobilization via physical adsorption. Based on these properties, a Fe₃O₄@MXene/GOD/Nafion/GCE electrode was fabricated. The composite’s high specific surface area, excellent conductivity, and good biocompatibility significantly promoted the direct electron transfer (DET) of GOD. Meanwhile, the apparent electron transfer rate constant (k_s) was calculated to be 9.57 s⁻¹, representing a 1.26-fold enhancement over the MXene-based electrode (7.57 s⁻¹) and confirming faster electron transfer kinetics. The sensor showed a bilinear glucose response in the ranges of 0.05–15 mM, with sensitivity of 120.47 μA·mM⁻¹·cm⁻² and a detection limit of 38 μM. It also exhibited excellent selectivity, reproducibility and stability. Satisfactory recovery rates were achieved in artificial serum samples while demonstrating comparable detection performance to commercial blood glucose meters. Full article

The enzymatic production of prebiotic galactooligosaccharides (GOS), functional food ingredients with established health benefits, remains an active research area driven by a rising global demand for GOS. These oligosaccharides are synthesized from lactose via transgalactosylation catalyzed by β-galactosidase, accompanied by hydrolysis of both substrate and products, and the competition between these reactions critically determines the maximum achievable GOS yield. In this study, β-galactosidase from Aspergillus oryzae was immobilized on an anion-exchange resin (Dowex Marathon MSA) using three glutaraldehyde-based crosslinking strategies. The resulting immobilized biocatalysts were characterized and evaluated for GOS synthesis, with product yield as the principal performance indicator. The results demonstrated that the immobilized biocatalysts markedly modulated the balance between transgalactosylation and hydrolytic activities. The biocatalyst prepared by simultaneous resin activation and enzyme crosslinking provided the highest GOS yield and operational stability. This biocatalyst was subsequently used to study the effects of lactose concentration, pH, enzyme loading, and temperature. Among these, lactose concentration most strongly influenced GOS yield, whereas the other factors primarily affected the reaction rate. These findings offer practical insights into enzyme immobilization strategies for optimizing GOS production. Full article

Objective: This study aimed to develop a stable and active biocatalytic system for enzyme immobilization, utilizing an electrospun support doped with a metal–organic framework (MOF) and supplemented with an ionic liquid as a lipase stabilizer and activity enhancer. Methodology: The system was applied for an efficient and enantioselective resolution of racemic citalopram. Key parameters, including MOF concentration, electrospinning and immobilization conditions, ionic liquid selection, and reaction time, were optimized to enhance biocatalyst performance. Results: The optimal immobilization time was determined to be 24 h, achieving 52% immobilization efficiency and 100% activity recovery. The resulting biocatalytic system HIGH PVC-MOF-lip-CA exhibited superior storage stability, retaining 80% of its initial activity, a 75% improvement over the free enzyme. In the resolution of citalopram, the system achieved 96% conversion of S-citalopram within 24 h, with the enantiomeric excess of 93% in favor of the S-ester over the R-ester. These findings demonstrate the system’s potential for efficient and stereoselective biocatalytic applications. Full article

Acetochlor is a selective herbicide affecting weeds of cereal plants. Its analysis in soils allows accessing their suitability for crops and risks of contamination of agricultural products. The aim of this study was to develop a microplate enzyme immunoassay for the determination of acetochlor in soil extracts. For the development, rabbit antibodies specific to acetochlor were obtained by immunization with a conjugate of carrier protein with a derivative of acetochlor with mercaptopropionic acid. Another derivative with mercaptosuccinic acid was applied for immobilization on the solid phase. In the study, organic extracts have been obtained from soil varying solvents and their ratios, and using QuEChERS protocol. The extracts have been tested to estimate residual influences of the sample matrix. Optimal conditions for the immunoassay were selected, appropriate sample preparation techniques, and the composition of the medium for competitive immune interaction. The most effective approach involved dichloromethane extraction, followed by careful evaporation and subsequent reconstitution of the dry residue in a 10 mM phosphate-buffer solution supplemented with 0.1% gelatin. The resulting analytical system exhibited a detection limit of 59.4 ng/mL for acetochlor, with a working range spanning from 112 to 965 ng/mL. Taking into account the soil sample preparation, the LOD was estimated as 0.3 µg/g with the working range from 0.66 to 5.7 µg/g of soil. Analysis of prepared extracts from gray forest soil demonstrated a revealing of acetochlor between 74% and 124%. Full article