Polyaniline-assisted silver nanoparticles: a novel support for the immobilization of α-amylase

Maltooligosaccharides: Properties, Production and Applications

Maltooligosaccharides (MOS) are homooligosaccharides that consist of 3-10 glucose molecules linked by α-1,4 glycosidic bonds. As they have physiological functions, they are commonly used as ingredients in nutritional products and functional foods. Many researchers have investigated the potential applications of MOS and their derivatives in the pharmaceutical industry. In this review, we summarized the properties and methods of fabricating MOS and their derivatives, including sulfated and non-sulfated alkylMOS. For preparing MOS, different enzymatic strategies have been proposed by various researchers, using α-amylases, maltooligosaccharide-forming amylases, or glycosyltransferases as effective biocatalysts. Many researchers have focused on using immobilized biocatalysts and downstream processes for MOS production. This review also provides an overview of the current challenges and future trends of MOS production.

The application of conventional or magnetic materials to support immobilization of amylolytic enzymes for batch and continuous operation of starch hydrolysis processes

In the production of ethanol, starches are converted into reducing sugars by liquefaction and saccharification processes, which mainly use soluble amylases. These processes are considered wasteful operations as operations to recover the enzymes are not practical economically so immobilizations of amylases to perform both processes appear to be a promising way to obtain more stable and reusable enzymes, to lower costs of enzymatic conversions, and to reduce enzymes degradation/contamination. Although many reviews on enzyme immobilizations are found, they only discuss immobilizations of α-amylase immobilizations on nanoparticles, but other amylases and support types are not well informed or poorly stated. As the knowledge of the developed supports for most amylase immobilizations being used in starch hydrolysis is important, a review describing about their preparations, characteristics, and applications is herewith presented. Based on the results, two major groups were discovered in the last 20 years, which include conventional and magnetic-based supports. Furthermore, several strategies for preparation and immobilization processes, which are more advanced than the previous generation, were also revealed. Although most of the starch hydrolysis processes were conducted in batches, opportunities to develop continuous reactors are offered. However, the continuous operations are difficult to be employed by magnetic-based amylases.

Encapsulation of peroxidase on hydrogel sodium polyacrylate spheres incorporated by silver and gold nanoparticles: A comparative study

The selectivity of biocatalysts based on enzymes, eco-friendly reaction systems, and strong catalyst performance is exceptionally compelling. For improving enzyme recyclability and stability, a good option that has been proved is immobilization. For enzyme immobilization, hydrogel sodium polyacrylate combined with nanoparticles is an interesting class of support matrices as compared to others. This study synthesizes and uses the cross-linked hydrogel sodium polyacrylate-decorated gold or silver nanoparticles (HSP/AuNPs or AgNPs) as immobilized support for peroxidase and FTIR characterizes it. The novel supports immobilized system properties enhanced biocompatibility. They have attained a greater immobilization yield (91% with HSP/AuNPs and 84% with HSP/AgNPs). The rest of the immobilized peroxidase activity, after 10 recurring cycles of HSP/AuNPs was 61% and HSP/AgNPs was 54% . The remaining activity of the immobilized enzyme onto HSP/AgNPs, after storing at 4°C for 6 weeks, was 73% and HSP/AuNPs was 75% of its initial activity. It was revealed that the optimum temperature for the free enzyme and the immobilized enzyme was 50°C and 50–60°C, respectively. For the immobilized enzyme, the optimum pH is 7–7.5, as compared to the optimum pH of free enzyme pH 6.5.

Amylases from thermophilic bacteria: structure and function relationship

Amylases hydrolyze starch to diverse products including dextrins and progressively smaller polymers of glucose units. Thermally stable amylases account for nearly 25% of the enzyme market. This review highlights the structural attributes of the α-amylases from thermophilic bacteria. Heterologous expression of amylases in suitable hosts is discussed in detail. Further, specific value maximization approaches, such as protein engineering and immobilization of the amylases are discussed in order to improve its suitability for varied applications on a commercial scale. The review also takes into account of the immobilization of the amylases on nanomaterials to increase the stability and reusability of the enzymes. The function-based metagenomics would provide opportunities for searching amylases with novel characteristics. The review is expected to explore novel amylases for future potential applications.

Synthesis of Ag@PANI nanocomposites by complexation method and their application as label-free chemo-probe for detection of mercury ions

A novel optical probe consistinsg of Ag@PANI (silver-polyaniline) nanocomposites was developed for detection of mercury ions (Hg2+). The poly-dispersed Ag@PANI nanocomposites were synthesized by complexation reaction method. We studied structural and functional properties of polymer nanocomposites thoroughly. Ag@PANI nanocomposites consist of fibrous morphology with a mean particle size of 31.39 nm. Ag@PANI nanocomposites consist of face-centered cubic crystal structure with an average crystallite size of 19.41 nm. Raman spectroscopy was used in sensitive and selective detection of Hg2+ ions in dynamic range of 0.01–0.1 ppm with limit of detection of 0.019 ppm. Ag@PANI nanocomposite sensor for Hg (II) ions has shown some sublime results in pH range 3–5. Ag@PANI-based sensing probe can be beneficial for Hg2+ ions detection in highly sensitive biological, chemical and environmental analysis. Our sensing probe has shown good reproducibility, and all recorded observations revealed that sensing probe consisting of Ag@PANI nanocomposites is well suited for detection of Hg2+ ions.

Structure, stability and chaperone function of Mycobacterium leprae Heat Shock Protein 18 are differentially affected upon interaction with gold and silver nanoparticles

Gold nanoparticles (AuNPs) and silver nanoparticles (AgNPs) have several biomedical applications. However, the effective usage of these two nanoparticles is impeded due to limited understanding of their interaction with proteins including small heat shock proteins (sHSPs). Specifically, no evidences of interaction of these two nanoparticles with HSP18 (an antigenic protein) which is an important factor for the growth and survival of M. leprae (the causative organism of leprosy) are available in the literature. Here, we report for the first time evidences of "HSP18-AuNPs/AgNPs interaction" and its impact on the structure and chaperone function of HSP18. Interaction of citrate-capped AuNPs/AgNPs (~20 nm diameter) to HSP18 alters the secondary and tertiary structure of HSP18 in a distinctly opposite manner; while "HSP18-AuNPs interaction" leads to oligomeric association, "HSP18-AgNPs interaction" results in oligomeric dissociation of the protein. Surface hydrophobicity, thermal stability, chaperone function of HSP18 and survival of thermally stressed E. coli harbouring HSP18 are enhanced upon AuNPs interaction, while all of them are reduced upon interaction with AgNPs. Altogether, our study reveals that HSP18 is an important drug target in leprosy and its chaperone function may possibly plays a vital role in the growth and survival of M. leprae pathogen in infected hosts.

Multiwalled carbon nanotubes bound beta-galactosidase: It's activity, stability and reusability

Carbon nanotubes (CNTs) based biosensors are recognized to be a next generation building block for ultrasensitive and fast biosensing systems. This article starting with a brief history on CNTs provides an overview on the recent expansion of research in the field of CNT-based biosensors. This is followed by the discussion on structure and properties related to CNTs. Furthermore, the basic and some newly developed synthetic methods of CNTs are summarized. In this chapter, we used polyaniline cobalt multiwalled CNTs to immobilize β-galactosidase, by adopting both noncovalent and covalent strategies. Herein, the methodologies of both techniques have been discussed in detail. The η (effectiveness factor) values for nanocomposite bound β-galactosidase by physical adsorption and covalent method were calculated to be 0.93 and 0.97, respectively. The covalently bound β-galactosidase retained 92% activity even after its 10th successive reuse as compared to the adsorbed enzyme which exhibited only 74% of its initial activity. CNT armored enzymes demonstrated remarkably high catalytic stability at both sides of temperature and pH-optima along with easy recovery from the reaction medium which can be utilized in various biotechnological applications. Lastly, the scientific and technological challenges in the field are discussed at the end of this chapter.

Immobilized Enzymes on Gold Nanoparticles: From Enhanced Stability to Cleaning of Heritage Textiles

Enzyme-based treatments are used in heritage conservation for the effective removal of glues and other damaging organic layers from the surfaces of historic and artistic works. Despite their potential, however, the application of enzymatic treatments is currently limited because of their poor efficiency and low operational and environmental stability. We demonstrate the use of α-amylase immobilized on gold nanoparticles to improve the efficacy of enzymatic treatments enhancing both the reactivity and the stability of the formulations. Gold nanoparticles coated with α-amylase exhibit significant advantages compared to free enzymes. We report up to 5× greater resistance to environmental changes, up to 2× higher efficacy toward removal of starch-based glues from textiles and deeper penetration through the fibers, without causing damage or inducing salt precipitation. These results offer exciting prospects for the development of enzymatic formulations, both for heritage conservation and the wider application of enzymes, such as in medicine, the detergent industry, and green chemistry.

Influence of the Silver Nanoparticles (AgNPs) Formation Conditions onto Titanium Dioxide (TiO2) Nanotubes Based Electrodes on Their Impedimetric Response

This paper presents the comparison of the effects of three methods of production of silver spherical and near-spherical nanoparticles (AgNPs) on the titanium dioxide nanotubes (TNT) base: cyclic voltammetry, chronoamperometry, and sputter deposition. It also evaluates the influence of silver nanoparticles on the electrochemical properties of the developed electrodes. The novelty of this research was to fabricate regular AgNPs free of agglomerates uniformly distributed onto the TNT layer, which has not been accomplished with previous attempts. The applied methods do not require stabilizing and reducing reagents. The extensive electrochemical characteristic of AgNP/TNT was performed by open circuit potential and electrochemical impedance spectroscopy methods. For AgNPs/TNT obtained by each method, the impedance module of these electrodes was up to 50% lower when compared to TNT, which means that AgNPs enabled more efficient electron transfer due to the effective area increase. In addition, the presence of nanoparticles increases the corrosion resistance of the prepared electrodes. These substrates can be used as electrochemical sensors due to their high electrical conductivity, and also as implants due to the antibacterial properties of both the TNT and AgNPs.

Synthesis and Novel Purification Process of PANI and PANI/AgNPs Composite

In this work, polyaniline (PANI) is synthesized via oxidative polymerization of aniline and purified using organic solvents where the emeraldine phase is isolated by employing a phase separation system. The above contributes to the increase in the percentage yield compared to previous works and the possibility of being used as a single phase. In addition, the PANI/AgNPs composite is prepared in situ at the polymerization of aniline, adding silver nitrate and glycine to create the AgNPs inside the PANI matrix by controlling the pH, temperature, time of reaction and incorporating a new purification technique.

Bienzyme Magnetic Nanobiocatalyst with Fe3+-Tannic Acid Film for One-Pot Starch Hydrolysis

In this study, a novel co-immobilization biocatalyst for one-pot starch hydrolysis was prepared through shielding enzymes on the Fe₃O₄/SiO₂ core-shell nanospheres by a Fe³⁺-tannic acid (TA) film. In brief, α-amylase and glucoamylase were covalently immobilized on amino-modified Fe₃O₄/SiO₂ core-shell nanospheres using glutarldehyde as a linker. Then, a Fe³⁺-TA protective film was formed through the self-assembly of the Fe³⁺ and TA coordination complex (Fe³⁺-TA@Fe₃O₄/SiO₂-enzymes). The film acts a "coating" to prevent the enzyme from denaturation and detachment, thus significantly improving its structural and operational stability. Furthermore, the immobilization efficiency reached 90%, and the maximum activity recovery of α-amylase and glucoamylase was 87 and 85%, respectively. More importantly, the bienzyme magnetic nanobiocatalyst with Fe³⁺-TA film could be simply recovered by a magnet. The Fe³⁺-TA@Fe₃O₄/SiO₂-enzymes kept 55% of the original activity after reuse for 9 cycles, indicating outstanding reusability. However, the bienzyme magnetic nanobiocatalyst without Fe³⁺-TA film maintained 28% of the initial activity.

Improvement of stability and reusability of α-amylase immobilized on naringin functionalized magnetic nanoparticles: A robust nanobiocatalyst

Enzyme immobilized on magnetic nanoparticles (MNPs) can be used as efficient recoverable biocatalysts under strong magnetic responses. In the present work, α-amylase was immobilized onto naringin functionalized MNPs via ionic interactions. For this purpose, the MNPs were functionalized with naringin, as a biocompatible flavonoid. The morphology, structure, and properties of functionalized MNPs and the immobilization of α-amylase on synthesized nanocomposite were characterized through different analytical tools including TGA, VSM, FTIR, SEM-EDX and TEM. Furthermore, the optimum conditions of temperature, pH, reaction time and enzyme concentration for immobilization process were investigated. The results showed that the optimal conditions for immobilization of α-amylase onto synthesized nanocarrier occurred at pH6.5 and 55°C. The reusability experiments revealed high activity maintenance of immobilized α-amylase even after 10 reaction cycles. Moreover, the storage stability of immobilized enzyme improved via immobilization in comparison with free one and it maintained 60% of its initial activity after 6weeks storage at 4°C. The improvements in enzyme catalytic properties via immobilization made this nanobiocatalyst as a good candidate in bio-industrial applications. Furthermore, the synthesized nanocomposite would have the potential for practical applications in other and binary enzyme immobilization.

Purification, Characterization of Amylase from Indigenously Isolated Aureobasidium pullulans Cau 19 and Its Bioconjugates with Gold Nanoparticles

The amylase from Aureobasidium pullulans Cau 19 was purified by ammonium sulfate precipitation and Sephadex G-100 chromatography with a 9.25-fold increase in specific activity as compared to crude enzyme. Km and turn over values of the enzyme were 6.25 mg/mL and 5.0 × 10²/min, respectively. Effect of different metal ions on the purified enzyme was investigated; 1 mM calcium (Ca) and cobalt (Co) enhanced enzyme activity by twofold; copper (Cu) had no effect on the activity of the enzyme. Mercury (Hg) 1 mM caused 90% inactivation whereas iron (Fe) and manganese (Mn) caused 10 to 16% inhibition. Amylase from A. pullulans Cau 19 was bioconjugated to gold nanoparticles synthesized using the biomass of A. pullulans Cau 19. Fourier transform infrared spectroscopy confirmed the conjugation of the enzyme to the gold nanoparticles. Though, only 20% of the added enzyme was adsorbed/conjugated on gold nanoparticles, 80% of the adsorbed activity could be estimated in the assay. The conjugated enzyme exhibited better tolerance to a broad pH range of 3.0-9.0 and higher temperatures compared with native enzyme.

Lipase immobilization on facile synthesized polyaniline-coated silver-functionalized graphene oxide nanocomposites as novel biocatalysts: stability and activity insights

Schematic representation of the preparation of PANI/Ag/GO-NCs and immobilization of lipase.

Nanomaterials as novel supports for the immobilization of amylolytic enzymes and their applications: A review

Numerous types of nanoparticles and nanocomposites have successfully been employed for the immobilization and stabilization of amylolytic enzymes; α-amylases, β-amylases, glucoamylases and pullulanases. Nano-support immobilized amylolytic enzymes retained very high activity and yield of immobilization. The immobilization of these enzymes, particularly α-amylases and pullulanases, to the nanosupports is helpful in minimizing the problem of steric hindrances during binding of substrate to the active site of the enzyme. The majority of nano-support immobilized amylolytic enzymes exhibited very high resistance to inactivation induced by different kinds of physical and chemical denaturants and these immobilized enzyme preparations maintained very high activity on their repeated and continuous uses. Amylolytic enzymes immobilized on nano-supports have successfully been applied in food, fuel, textile, paper and pulp, detergent, environmental, medical, and analytical fields.

Isolation of α-Amylase Inhibitors from Kadsura longipedunculata Using a High-Speed Counter-Current Chromatography Target Guided by Centrifugal Ultrafiltration with LC-MS

In this study, a high-speed counter-current chromatography (HSCCC) separation method target guided by centrifugal ultrafiltration with high-performance liquid chromatography-mass spectrometry (CU-LC-MS) was proposed. This method was used to analyze α-amylase inhibitors from Kadsura longipedunculata extract. According to previous screening with CU-LC-MS, two screened potential α-amylase inhibitors was successfully isolated from Kadsura longipedunculata extract using HSCCC under the optimized experimental conditions. The isolated two target compounds (with purities of 92.3% and 94.6%) were, respectively, identified as quercetin-3-O-rhamnoside (1) and protocatechuic acid (2) based on the MS, UV, and ¹H-NMR spectrometry data. To verify the inhibition of screened compounds, the inhibitory activities of quercetin-3-O-rhamnoside (1) and protocatechuic acid (2) on α-amylase were tested, and it demonstrated that the experimental IC50 values of quercetin-3-O-rhamnoside (1) and protocatechuic acid (2) were 28.8 and 12.5 μmol/L. These results proved that the hyphenated technique using CU-LC-MS and HSCCC was a rapid, competent, and reproductive method to screen and separate potential active compounds, like enzyme inhibitors from the extract of herbal medicines.

Metallic/bimetallic magnetic nanoparticle functionalization for immobilization of α-amylase for enhanced reusability in bio-catalytic processes

Novel magnetic nanoparticles coated with silica and gold were synthesized for immobilization of α-amylase enzyme and characterized with Fourier transform infrared spectroscopy, transmission electron microscopy. Effect of various limiting factors such as substrate concentration, temperature, and pH on the catalytic activity of enzyme was investigated. The optimum pH for free and immobilized enzyme was found unaffected (7.0), whereas optimum temperature for the enzyme activity was increased from 60°C for free enzyme to 80°C for immobilized counterpart. The gains in catalytic attributes concomitant to ease of recovery of the enzyme reflect the potential of the approach and the product to be useful for the enzymatic bioprocessing. The Michaelis-Menten constant (Km) value of the immobilized α-amylase was higher than that of free α-amylase, whereas maximum velocity (Vmax), and turn over number (Kcat), values were almost similar. Immobilized α-amylase maintained 60% of the enzyme activity even after recycling ten times.

Facile in situ synthesis and characterization of a novel PANI/Fe3O4/Ag nanocomposite and investigation of catalytic applications

A novel magnetic hybrid nanocomposite was successfully synthesized via in situ polymerization, well characterized by FT-IR, XRD, EDX and FE-SEM analysis, and its catalytic activity shown in the synthesis of pharmaceutically important pyrans.

Graphene based magnetic nanocomposites as versatile carriers for high yield immobilization and stabilization of β-galactosidase

The present study demonstrates an efficient method for high yield immobilization of Aspergillus oryzae β-galactosidase onto graphene-iron oxide nanocomposites (Gr@Fe₃O₄ NCs) by a simple adsorption mechanism.

Chloride Activated Halophilic α-Amylase from Marinobacter sp. EMB8: Production Optimization and Nanoimmobilization for Efficient Starch Hydrolysis

Halophiles have been perceived as potential source of novel enzymes in recent years. The interest emanates from their ability to catalyze efficiently under high salt and organic solvents. Present work encompasses production optimization and nanoimmobilization of an α-amylase from moderately halophilic Marinobacter sp. EMB8. Media ingredients and culture conditions were optimized by “one-at-a-time approach.” Starch was found to be the best carbon source at 5% (w/v) concentration. Glucose acted as catabolic repressor for amylase production. Salt proved critical for amylase production and maximum production was attained at 5% (w/v) NaCl. Optimization of various culture parameters resulted in 48.0 IU/mL amylase production, a 12-fold increase over that of unoptimized condition (4.0 IU/mL). α-Amylase was immobilized on 3-aminopropyl functionalized silica nanoparticles using glutaraldehyde as cross-linking agent. Optimization of various parameters resulted in 96% immobilization efficiency. Starch hydrolyzing efficiency of immobilized enzyme was comparatively better. Immobilized α-amylase retained 75% of its activity after 5th cycle of repeated use.

Immobilization of trypsin on plasma prepared Ag/PPAni nanocomposite film for efficient digestion of protein

This work demonstrates the efficacy of a support matrix prepared by plasma process for trypsin immobilization without any surface activator. Plasma polymerization cum sputtering process is used to prepare the nanocomposite support matrix. Plasma sputtered silver nanoparticles (AgNPs) are uniformly embedded into plasma polymerized aniline (PPAni) film. Various characterization tools are employed to study the surface morphology, microstructure and chemical composition of the support matrices. Trypsin is immobilized onto the support matrix via the formation of covalent bond between them. Plasma generated free radicals on composite films activate the support matrix and make it efficient for increasing the tertiary enzyme stability via multipoint covalent attachment. Trypsin immobilized onto Ag/PPAni matrix has more hydrolyzing capacity of bovine serum albumin (BSA) than free trypsin as well as trypsin immobilized onto PPAni films.

Activity and stability of urease entrapped in thermosensitive poly(N-isopropylacrylamide-co-poly(ethyleneglycol)-methacrylate) hydrogel

Urease was entrapped in thermally responsive poly(N-isopropylacrylamide-co-poly(ethyleneglycol)-methacrylate), p[NIPAM-p(PEG)-MA], copolymer hydrogels. The copolymer membrane shows temperature-responsive properties similar to conventional p(NIPAM) hydrogels, which reversibly swell below and de-swell above the lower critical solution temperature of p(NIPAM) hydrogel at around 32 °C. The retained activities of the entrapped urease (in p[NIPAM-p(PEG)-MA]-4 hydrogels) were between 83 and 53% compared to that of the same quantity of free enzyme. Due to the thermo-responsive character of the hydrogel matrix, the maximum activity was achieved at around 25 °C with the immobilized urease. Optimum pH was the same for both free and entrapped enzyme. Operational, thermal and storage stabilities of the enzyme were found to increase with entrapment of urease in the thermoresponsive hydrogel matrixes. As for reusability, the immobilized urease retained 89% of its activity after ten repeated uses.