Improved biosynthesis of silver nanoparticles using keratinase from Stenotrophomonas maltophilia R13: reaction optimization, structural characterization, and biomedical activity

Green synthesis of silver nanoparticles using Keratinase from Pseudomonas aeruginosa-C1M, characterization and applications as novel multifunctional biocatalyst

INTRODUCTION

This study explores the biogenic synthesis of silver nanoparticles (AgNPs) using keratinase from Pseudomonas aeruginosa-C1M as a reducing and stabilizing agent. The synthesis of AgNPs was characterized by a color change from transparent to dark brown and a UV-Vis absorption peak at 450 nm, confirming nanoparticle formation. The study further investigates the structural, morphological, and functional properties of these AgNPs, particularly their antibacterial activity and their potential role in azo dye decontamination.

METHODS AND RESULTS

The FTIR confirmed that AgNPs nanoparticles formation with keratinase. X-ray diffraction analysis showed that the prepared AgNPs were crystalline in nature and had face-centered cubic lattice planes. When observed under the transmission electron microscope and scanning electron microscope the nanoparticles were monodispersed spheres of different sizes. The diameter of the AgNPs was ~ 119 nm according to dynamic light scattering. High dispersion, long-term stability and excellent colloidal properties were supported by a high negative zeta potential value. The silver nanoparticles were found to have an antibacterial activity with zone of inhibition 25 mm and 33 mm against pathogenic strains of Staphylococcus aureus and Escherichia coli respectively. The synthesized zero-valent silver nanoparticles assisted in the decontamination of azo dyes (methyl red, methyl orange, safranin O and methyl violet) through the incorporation of sodium borohydride and light-catalyzed processes.

CONCLUSION

This study demonstrates, for the first time, that keratinase from Pseudomonas aeruginosa-C1M can be used for AgNPs synthesis. The biogenic AgNPs exhibited potent antibacterial activity and played a crucial role in detoxifying hazardous azo dyes. These findings highlight the dual-functional potential of AgNPs for applications in antimicrobial treatments and environmental remediation. Future studies should explore their mechanism of action, scalability, and industrial applications.

Microbial Nanotechnology for Precision Nanobiosynthesis: Innovations, Current Opportunities and Future Perspectives for Industrial Sustainability

A new area of biotechnology is nanotechnology. Nanotechnology is an emerging field that aims to develope various substances with nano-dimensions that have utilization in the various sectors of pharmaceuticals, bio prospecting, human activities and biomedical applications. An essential stage in the development of nanotechnology is the creation of nanoparticles. To increase their biological uses, eco-friendly material synthesis processes are becoming increasingly important. Recent years have shown a lot of interest in nanostructured materials due to their beneficial and unique characteristics compared to their polycrystalline counterparts. The fascinating performance of nanomaterials in electronics, optics, and photonics has generated a lot of interest. An eco-friendly approach of creating nanoparticles has emerged in order to get around the drawbacks of conventional techniques. Today, a wide range of nanoparticles have been created by employing various microbes, and their potential in numerous cutting-edge technological fields have been investigated. These particles have well-defined chemical compositions, sizes, and morphologies. The green production of nanoparticles mostly uses plants and microbes. Hence, the use of microbial nanotechnology in agriculture and plant science is the main emphasis of this review. The present review highlights the methods of biological synthesis of nanoparticles available with a major focus on microbially synthesized nanoparticles, parameters and biochemistry involved. Further, it takes into account the genetic engineering and synthetic biology involved in microbial nanobiosynthesis to the construction of microbial nanofactories.

Response surface methodology based optimization of keratinase from Bacillus velezensis strain ZBE1 and nanoparticle synthesis, biological and molecular characterization

The increasing demands of keratinases for biodegradation of recalcitrant keratinaceous waste like chicken feathers has lead to research on newer potential bacterial keratinases to produce high-value products with biological activities. The present study reports a novel keratinolytic bacterium Bacillus velezensis strain ZBE1 isolated from deep forest soil of Western Ghats of Karnataka, which possessed efficient feather keratin degradation capability and induced keratinase production. Production kinetics depicts maximum keratinase production (11.65 U/mL) on 4th day with protein concentration of 0.61 mg/mL. Effect of various physico-chemical factors such as, inoculum size, metal ions, carbon and nitrogen sources, pH and temperature influencing keratinase production were optimized and 3.74 folds enhancement was evidenced through response surface methodology. Silver (AgNP) and zinc oxide (ZnONP) nanoparticles with keratin hydrolysate produced from chicken feathers by the action of keratinase were synthesized and verified with UV-Visible spectroscopy that revealed biological activities like, antibacterial action against Bacillus cereus and Escherichia coli. AgNP and ZnONP also showed potential antioxidant activities through radical scavenging activities by ABTS and DPPH. AgNP and ZnONP revealed cytotoxic effect against MCF-7 breast cancer cell lines with IC50 of 5.47 µg/ml and 62.26 µg/ml respectively. Characterizations of nanoparticles were carried out by Fourier transform infrared spectroscopy, scanning electron microscopy with energy dispersive X-ray, X-ray diffraction, thermogravimetric analysis and atomic force microscopy analysis to elucidate the thermostability, structure and surface attributes. The study suggests the prospective applications of keratinase to trigger the production of bioactive value-added products and significant application in nanotechnology in biomedicine.

Metal Nanomaterials and Hydrolytic Enzyme-Based Formulations for Improved Antifungal Activity

Active research of metal-containing compounds and enzymes as effective antifungal agents is currently being conducted due to the growing antifungal resistance problem. Metals are attracting special attention due to the wide variety of ligands that can be used for them, including chemically synthesized and naturally obtained variants as a result of the so-called "green synthesis". The main mechanism of the antifungal action of metals is the triggering of the generation and accumulation of reactive oxygen species (ROS). Further action of ROS on various biomolecules is nonspecific. Various hydrolytic enzymes (glucanases and proteases), in turn, exhibit antifungal properties by affecting the structural elements of fungal cells (cell walls, membranes), fungal quorum sensing molecules, fungal own protective agents (mycotoxins and antibiotics), and proteins responsible for the adhesion and formation of stable, highly concentrated populations in the form of biofilms. A wide substrate range of enzymes allows the use of various mechanisms of their antifungal actions. In this review, we discuss the prospects of combining two different types of antifungal agents (metals and enzymes) against mycelial fungi and yeast cells. Special attention is paid to the possible influence of metals on the activity of the enzymes and the possible effects of proteins on the antifungal activity of metal-containing compounds.

Recent trends in microbial nanoparticle synthesis and potential application in environmental technology: a comprehensive review

Microbial technology comprising environment in various aspects of pollution monitoring, treatment of pollutants, and energy generation has been put forth by the researchers worldwide in an eco-friendly manner. During the past few decades, this revolution has pronounced microbial cells in green nanotechnology, extending the scope, efficiency, and investment capita at research institutes, industries, and global markets. In the present review, initially, the source for the microbial synthesis of nanoparticles will be discussed involving bacteria, fungi, actinomycetes, microalgae, and viruses. Further, the mechanism and bio-components of microbial cells such as enzymes, proteins, peptides, amino-acids, exopolysaccharides, and others involved in the bio-reduction of metal ions to corresponding metal nanoparticles will be emphasized. The biosynthesized nanoparticles physicochemical properties and bio-reduction methods' advantages compared with synthetic methods will be detailed. To understand the suitability of biosynthesized nanoparticles in a wide range of applications, an overview of its blend of medicine, agriculture, and electronics will be discussed. This will be geared up with its applications specific to environmental aspects such as bioremediation, wastewater treatment, green-energy production, and pollution monitoring. Towards the end of the review, nano-waste management and limitations, i.e., void gaps that tend to impede the application of biosynthesized nanoparticles and microbial-based nanoparticles' prospects, will be deliberated. Thus, the review would claim to be worthy of unwrapping microorganisms sustainability in the emerging field of green nanotechnology.

A critical review on silver nanoparticles: From synthesis and applications to its mitigation through low-cost adsorption by biochar

Silver nanoparticles are one of the most beneficial forms of heavy metals in nanotechnology applications. Due to its exceptional antimicrobial properties, low electrical and thermal resistance, and surface plasmon resonance, silver nanoparticles are used in a wide variety of products, including consumer goods, healthcare, catalysts, electronics, and analytical equipment. As the production and applications of silver nanoparticles containing products increase daily, the environmental pollution due to silver nanoparticles release is increasing and affecting especially the aqueous ecosystem. Silver nanoparticles can kill useful bacteria in soil and water, and bioaccumulate in living organisms even at low concentrations from 10^-2 to 10 μg/mL silver can show antibacterial effect. On the other hand, the maximum silver discharge limit into freshwater is 0.1 μg/L and 3.2 μg/L for Australia and the USA, respectively. To reduce its toxic consequences and meet the regulatory guidelines, it is crucial to remove silver nanoparticles from wastewater before it is discharged into other water streams. Several technologies are available to remove silver nanoparticles, but the adsorption process using low-cost adsorbents is a promising alternative to mitigate silver nanoparticle pollution in the bulk stage. As one of the low-cost adsorbents, biochar produced from the biomass waste could be a suitable adsorbent. This review focuses on collating the latest evidence on silver nanoparticle production, applications, environmental consequences, and cost-effective technological approaches for silver removal from wastewater.

The tale of a versatile enzyme: Molecular insights into keratinase for its industrial dissemination

Keratinases are unique among proteolytic enzymes for their ability to degrade recalcitrant insoluble proteins, and they are of critical importance in keratin waste management. Over the past few decades, researchers have focused on discovering keratinase producers, as well as producing and characterizing keratinases. The application potential of keratinases has been investigated in the feed, fertilizer, leathering, detergent, cosmetic, and medical industries. However, the commercial availability of keratinases is still limited due to poor productivity and properties, such as thermostability, storage stability and resistance to organic reagents. Advances in molecular biotechnology have provided powerful tools for enhancing the production and functional properties of keratinase. This critical review systematically summarizes the application potential of keratinase, and in particular certain newly discovered catalytic capabilities. Furthermore, we provide comprehensive insight into mechanistic and molecular aspects of keratinases including analysis of gene sequences and protein structures. In addition, development and current advances in protein engineering of keratinases are summarized and discussed, revealing that the engineering of protein domains such as signal peptides and pro-peptides has become an important strategy to increase production of keratinases. Finally, prospects for further development are also proposed, indicating that advanced protein engineering technologies will lead to improved and additional commercial keratinases for various industrial applications.

Metal-Based Nanoparticles as Antimicrobial Agents: An Overview

Metal-based nanoparticles have been extensively investigated for a set of biomedical applications. According to the World Health Organization, in addition to their reduced size and selectivity for bacteria, metal-based nanoparticles have also proved to be effective against pathogens listed as a priority. Metal-based nanoparticles are known to have non-specific bacterial toxicity mechanisms (they do not bind to a specific receptor in the bacterial cell) which not only makes the development of resistance by bacteria difficult, but also broadens the spectrum of antibacterial activity. As a result, a large majority of metal-based nanoparticles efficacy studies performed so far have shown promising results in both Gram-positive and Gram-negative bacteria. The aim of this review has been a comprehensive discussion of the state of the art on the use of the most relevant types of metal nanoparticles employed as antimicrobial agents. A special emphasis to silver nanoparticles is given, while others (e.g., gold, zinc oxide, copper, and copper oxide nanoparticles) commonly used in antibiotherapy are also reviewed. The novelty of this review relies on the comparative discussion of the different types of metal nanoparticles, their production methods, physicochemical characterization, and pharmacokinetics together with the toxicological risk encountered with the use of different types of nanoparticles as antimicrobial agents. Their added-value in the development of alternative, more effective antibiotics against multi-resistant Gram-negative bacteria has been highlighted.

Symbiotic microbes of Saxifraga stellaris ssp. alpigena from the copper creek of Schwarzwand (Austrian Alps) enhance plant tolerance to copper

Saxifraga stellaris var. alpigena grows as one of the very few higher plants in the copper rich area of the "blue creek" in Austria. Two endophytes were isolated from it: Mortierella sp. (fungus), and Stenotrophomonas maltophilia (bacterium). Both microbes were practically inseparable due to resistance of the bacteria to the antibiotics tested. On PDA media, the fungus showed higher tolerance to copper than the bacterium, which disappeared from both the media and the surface of the fungus in the presence of 150 μM of Cu. However, at this Cu concentration, the bacteria were still detectable inside the mycelium and reappeared on the outside when transferred to media of lower Cu concentration. Microscopic studies of in vitro cultivated plants showed that the fungus was present in both, the roots and shoots of the plant. The effects of endophytes on plant performance were assessed in rhizoboxes filled with Cu-rich substratum; plants inoculated with both microbes showed better growth, survival and photosynthesis performance than the non-inoculated controls. The results of this study prove the beneficial influence of the isolated endophytes on the Cu tolerance of S. stellaris, and indicate the ecological potential of applying microbial consortia to plants under extreme environmental conditions.

Nanobiohybrids: a new concept for metal nanoparticles synthesis

In recent years, nanoscience and nanotechnology have brought a great revolution in different areas. In particular, the synthesis of transition metal nanoparticles has been of great relevance for their use in areas such as biomedicine, antimicrobial properties or catalytic applications for chemical synthesis. Recently, an innovative straightforward and very efficient synthesis of these nanoparticles by simply using enzymes as inductors in aqueous media has been described. This represents a very green alternative to the different methodologies described in the literature for metal nanoparticles preparation where harsh conditions are necessary. In this review the most recent advances in the synthesis of metal nanoparticles by this green technology, explaining the synthetic mechanism, the role of the enzyme in the formation of the nanoparticles and the effect on the final properties of these nanoparticles, are summarised. The application of these novel metal nanoparticles-enzyme hybrids in synthetic chemistry as heterogeneous catalysts with metal or dual (enzymatic and metallic) activity and their capacity as environmental and antimicrobial agents have also been discussed.