Immobilized Form Research Articles

The effect of cesium content on the thermodynamic stability and chemical durability of (Ba,Cs)1.33(Al,Ti)8O16 hollandite

AbstractTitanate‐based hollandite ceramics are promising nuclear waste forms for Cs immobilization. In this work, a series of Al‐substituted hollandite (Ba,Cs)1.33(Al,Ti)8O16 was investigated across a broad compositional range with varying Cs content. Powder X‐ray diffraction showed that all samples exhibited a tetragonal hollandite phase. Enthalpies of formation determined by high‐temperature melt solution calorimetry indicated enhanced thermodynamic stability with increased Cs content, which generally agreed with sublattice‐based thermodynamic calculations. Moreover, enthalpies of formation of the samples were primarily affected by three factors: (a) relative sizes of cations on the A‐sites and B‐sites, (b) tolerance factor, and (c) optical basicity. Fractional element release revealed that Cs retention was significantly improved for the high Cs‐containing hollandite compositions, which were supported by the evolution of microstructure of the pre and postleach particles. Elution studies of Al‐substituted hollandite spiked with radioactive 137Cs indicated that transmutation of Cs to Ba in the hollandite was accompanied by an increase in the retention of the Cs decay product, suggesting long‐term stability of Al‐substituted hollandite phase.

Role of microbial lipases in transesterification process for biodiesel production

Bio-diesel is a fuel produced by transesterification reaction of oil or fat in the presence of a catalyst. It is an alternate renewable source for petrol and diesel, which helps in reducing greenhouse gases emissions. Chemical catalysts such as sodium hydroxide, potassium hydroxide, sulfuric acid are used in the conventional methods of biodiesel production. This review focusses on application of lipase enzyme in transesterification of different types of oils such as: soybean, sunflower, rapeseed, palm oil, and waste cooking oil. Worldwide production of biodiesel via lipase enzyme and its economic as well as future aspects are also discussed. Various researchers have used free lipase in biodiesel production however, some lipases are also utilized as immobilized form. There are number of fungal and bacterial species that have been used to synthesize lipases, some of the microbial species are as follows: Aspergillus niger, Burkholderia cepacia, Pseudomonas aeruginosa, Staphylococcus epidermidis etc. Solid-state fermentation and broth culture of fungus is suitable for crude lipase production. Immobilized lipase plays very significant role in transesterification process. Lipases enzymes act as a good catalyst therefore, its production and utilization may be a better alternative of chemical catalysts.

Fusion and secretory expression of an exo-inulinase and a d-allulose 3-epimerase to produce d-allulose syrup from inulin.

This study developed a feasible catalytic method for d-allulose syrup production using a fusion enzyme, either in free or immobilized form, through hydrolysis of inulin extracted from Jerusalem artichoke tubers. d-Allulose 3-epimerase (DAE) was actively expressed in secretory form by fusing with the extracellular exo-inulinase CSCA in Escherichia coli BL21 (DE3). The best linker ligating the two enzymes was a flexible peptide containing 12 residues (GSAGSAAGSGEF). At 55 °C and pH 8.0, and as with the addition of 1 mmol L-1 Mn2+ , the CSCA-linkerE-DAE fusion enzyme obtained through high cell-density cultivation displayed a maximal exo-inulinase activity of 21.8 U mg-1 and resulted in a yield of 6.3 g L-1 d-allulose and 39.2 g L-1 d-fructose using 60 g L-1 inulin as the raw material. Catechol-modified alginate with titanium ions (Alg(Ti)PDA) was found to be a promising immobilization material for the fusion enzyme. After conversion for 8 days, the Alg(Ti)PDA-immobilized CSCA-linkerE-DAE (8 U g-1 ) completed 24 reaction cycles and retained over 80% of its original activity. Each reaction obtained an average of 19.8 g L-1 d-allulose and 32.7 g L-1 D-fructose from 60 g L-1 inulin. This study shed light on a feasible and cost-effective approach for the production of syrup containing d-allulose and D-fructose with inulin as the raw material via the use of a CSCA and DAE fusion enzyme. This syrup is of added value as a functional sweetener. © 2020 Society of Chemical Industry.

Design of immobilized biocatalyst and optimal conditions for tyrosol β-galactoside production.

Tyrosol β-galactoside (TG) is a phenylethanoid glycoside with proven neuroprotective properties. This work deals with its biocatalytic production from tyrosol and lactose using Aspergillus oryzae β-galactosidase in immobilized form. Six commercial carriers were examined to find the optimal biocatalyst. Besides standard biocatalyst performance characteristics, adsorption of the hydrophobic substrate on immobilization carrier matrices was also investigated. The adsorption of tyrosol was significant, but it did not have adverse effects on TG production. On the contrary, TG yield was improved for some biocatalysts. A biocatalyst prepared by covalent binding of β-galactosidase on an epoxy-activated carrier was used for detailed investigation of the effect of reaction conditions on glycoside production. Temperature had a surprisingly weak effect on the overall process rate. A lactose concentration of 0.83M was found to be optimal to enhance TG formation. The impact of tyrosol concentration was rather complex. This substrate caused inhibition of all reactions. Its concentration had a strong effect on the hydrolysis of lactose and all products. Higher tyrosol concentrations, 30-40g/L, were favorable as pseudo-equilibrium concentrations of TG and galactooligosaccharide were reached. Repeated batch results revealed excellent operational stability of the biocatalyst.

Optimization of various encapsulation systems for efficient immobilization of actinobacterial glucose isomerase

Abstract Glucose isomerase (GI) converts glucose into fructose by a reversible reaction. This reaction is industrially valuable for the production of high fructose corn syrup (HFCS) which is used as a sweetener by food and beverage industries. GI being an expensive enzyme necessitates its usage in immobilized form for increasing its reusability and economic viability. Global HFCS production accounts to 10 million tons which is highest among products yielded by immobilized process. Current study evaluates different encapsulation systems for immobilization of GI produced by Streptomyces sp. T.S.A.KP which was found to be Streptomyces enissocaesilis (Accession number MN911386 ). This is the first report of extracellular GI production by a strain of Streptomyces enissocaesilis. GI was immobilized using chitosan, alginate and agar to enhance its stability and conversion efficiency. The concentration of polymeric gel with cross linking agent was optimized to get ideal pore size for maximum GI activity. Immobilization on chitosan significantly increased (P

Transformation of calcite to fluorapatite at room temperature: Impact of initial phosphate and fluoride levels

Geogenic fluoride (F) contamination in groundwater is a severe problem affecting millions of people across the world. For many F-contaminated aquifers, the solution saturation state is controlled by calcite and/or dolomite solubility. Recently, apatite-based ex situ F-immobilization techniques have gained attention as they minimize the release of secondary pollutants, otherwise attributed to conventional sorptive F-removal methods. Likewise, addition of phosphate (PO4) to F-contaminated subsurface environments could potentially facilitate immobilization of fluoride in sparingly soluble apatites. The success of these ex situ or in situ interventions would rely on careful understanding of the mechanisms behind F immobilization and the long-term stability of these immobilized forms. In this study, the impact of PO4 on the extent and forms of F uptake in the presence of calcite under conditions supersaturated with respect to fluorapatite (Ca5(PO4)3F; FA) were investigated. A year-long series of batch equilibration experiments with varying degrees of initial supersaturation, involving combinations of F (0.1–0.42 mM), PO4 (0.7–1 mM), and calcite (0.1–4 g·L−1), were conducted at room temperature. Total dissolved concentrations of F, Ca, and PO4 were analyzed with time. Changes in solution saturation state were evaluated within a thermodynamic modeling framework comprising an updated database of relevant aqueous and mineral solubility reactions. Additionally, surface complexation modeling was used to interpret F uptake on calcite. Results from the solution chemistry indicated that the system responded to relative kinetics of dissolution of calcite and precipitation of FA or fluoridated HA. System pH and Ca concentrations in the presence of phosphate were controlled by rapid calcite dissolution, which facilitated F uptake by creating conditions highly supersaturated with respect to FA. Formation of FA was suggested by the observed PO4: F molar uptake ratio (∼3), consistent with FA stoichiometry, and was confirmed with scanning electron microscopy-associated energy dispersive X-ray spectroscopy, X-ray diffraction, Fourier-transformed infrared spectroscopy, transmission electron microscopy-associated selected area diffraction, and X-ray photoelectron spectroscopy on solids collected at the end of the equilibration studies. Furthermore, stoichiometric PO4:F molar uptake was found only for systems containing concentrations of initial F, PO4, and calcite above certain critical levels (0.42 mM, 1 mM, and 1 g·L−1, respectively). Surface complexation modeling predictions suggested minimal adsorption of F and PO4 onto calcite for all conditions, irrespective of the initial concentrations. For sub-critical initial concentrations, F uptake probably occurred due to formation of fluoridated-hydroxyapatite (non-stoichiometric FA). Significantly, these immobilized F forms controlled the observed F and P concentrations below the respective drinking water and discharge limits for a year.

Evaluation of Designed Immobilized Catalytic Systems: Activity Enhancement of Lipase B from Candida antarctica

Immobilized enzymatic catalysts are widely used in the chemical and pharmaceutical industries. As Candida antarctica lipase B (CALB) is one of the more commonly used biocatalysts, we attempted to design an optimal lipase-catalytic system. In order to do that, we investigated the enantioselectivity and lipolytic activity of CALB immobilized on 12 different supports. Immobilization of lipase on IB-D152 allowed us to achieve hyperactivation (178%) in lipolytic activity tests. Moreover, the conversion in enantioselective esterification increased 43-fold, when proceeding with lipase-immobilized on IB-S861. The immobilized form exhibited a constant high catalytic activity in the temperature range of 25 to 55 °C. Additionally, the lipase immobilized on IB-D152 exhibited a higher lipolytic activity in the pH range of 6 to 9 compared with the native form. Interestingly, our investigations showed that IB-S500 and IB-S60S offered a possibility of application in catalysis in both organic and aqueous solvents. A significant link between the reaction media, the substrates, the supports and the lipase was confirmed. In our enzymatic investigations, high-performance liquid chromatography (HPLC) and the titrimetric method, as well as the Bradford method were employed.

Dual immobilization of α-amylase and horseradish peroxidase via electrospinning: A proof of concept study

In this work, we propose a facile technique to dually-immobilize α-amylase and horseradish peroxidase (HRP) as two different enzyme models via entrapment within two distinct polymeric electrospun fibers by simple mixing steps and compare their properties with both individually immobilized forms and with the free counterparts. The immobilization was verified using Fourier transform infrared spectroscopy (FTIR) and Field emission scanning electron microscope (FESEM). The immobilization efficiencies for the dual-immobilized HRP and α-amylase were 89% and 85%, respectively. The retained catalytic activities of the dual-immobilized HRP and α-amylase enzymes were observed to be 79% and 80.2% after 10 cycles, respectively. After storage for 12 weeks, the dual-immobilized enzymes still retained nearly 90% activities similar to the individually immobilized ones. This immobilization procedure did not appear to exert either negative or back inhibitory effects upon both enzymes with respect to the different enzymatic assay procedures. This approach demonstrates that two or more type of enzymes could be mixed with different polymers individually and undergoes electrospinning simultaneously. We believe that this approach is expected to considerably promote and extend the application of multi-enzyme systems and worth further investigation for potential enzyme mediated cascade reactions.

Application of free and immobilized laccase for removal and detoxification of fluoroquinolones from aqueous solution

<p>Laccase from Trametes versicolor was immobilized by covalent bonds formation on CPC silica carriers. Elimination of two floroqinolone (FQ); enrofloxacine (ENR) and flumequine (FLU) using laccase in both free and immobilized form in the absence and presence of 1-hydroxybenzotriazole (HBT) and 4-Hydroxybenzoic acid (HBA) as mediators was investigated. Temperature, pH and storage stability of immobilized laccase was significantly improved compare to free laccase. In the absence of a laccase mediator, the initial concentrations of 50 mg L–1 of ENR and FLU decreased by 19 % and 28 %, respectively, after 6 h treatment using the immobilized laccase, while, the removal percentages were increased to 98 % and 96 %, respectively, when the immobilized laccase was used in presence of HBT. Whereas, the removal percentages of ENR and FLU were increased to 97 % and 88 %, respectively, when the immobilized laccase was used in presence of HBA. After twenty runs of the enzymatic elimination (laccase-HBT system) of ENR and FLU, the immobilized laccase exhibited the relative removal of 17.63 % and 15.62 %, respectively. The results of microtoxicity test (growth inhabitation percentage of six bacterial strains) showed a significant decrease in toxicity of the laccase-treated ENR and FLU solution.</p>

Immobilized Biocatalysts of Eversa® Transform 2.0 and Lipase from Thermomyces Lanuginosus: Comparison of Some Properties and Performance in Biodiesel Production

Eversa® Transform (ET), and the lipase from Thermomyces lanuginosus (TLL), liquid commercial lipases formulations, have been immobilized on octyl agarose beads and their stabilities were compared. Immobilized and free ET forms were more thermostable than TLL formulations at pH 5.0, 7.0, and 9.0, and the ET immobilized form was more stable in the presence of 90% methanol or dioxane at 25 °C and pH 7. Specific activity versus p-nitrophenyl butyrate was higher for ET than for TLL. However, after immobilization the differences almost disappeared because TLL was very hyperactivated (2.5-fold) and ET increased the activity only by 1.6 times. The enzymes were also immobilized in octadecyl methacrylate beads. In both cases, the loading was around 20 mg/g. In this instance, activity was similar for immobilized TLL and ET using triacetin, while the activity of immobilized ET was lower using (S)-methyl mandelate. When the immobilized enzymes were used to produce biodiesel from sunflower oil and methanol in tert-butanol medium, their performance was fairly similar.

Forty years of study on the thermostable β-glycosidase from S. solfataricus: Production, biochemical characterization and biotechnological applications.

The aim of this paper is to make the point on the fortieth years study on the β-glycosidase from Sulfolobus solfataricus. This enzyme represents one of the thermophilic biocatalysts, which is more extensively studied as witnessed by the numerous literature reports available since 1980. Comprehensive biochemical studies highlighted its broad substrate specificity for β-d-galacto-, gluco-, and fuco-sides and also showed its remarkable exo-glucosidase and transglycosidase activities. The enzyme demonstrated to be active and stable over a wide range of temperature and pHs, withstanding to several drastic conditions comprising solvents and detergents. Over the years, a great deal of studies were focused on its homotetrameric tridimensional structure, elucidating several structural features involved in the enzyme stability, such as ion pairs and post-translational modifications. Several β-glycosidase mutants were produced in the years in order to understand its peculiar behavior in extreme conditions and/or to improve its functional properties. The β-glycosidase overproduction was also afforded reporting numerous studies dealing with its production in the mesophilic host Escherichia coli, Saccharomyces cerevisiae, Pichia pastoris, and Lactococcus lactis. Relevant applications in food, beverages, bioenergy, pharmaceuticals, and nutraceutical fields of this enzyme, both in free and immobilized forms, highlighted its biotechnological relevance.

Rapid synthesis of zirconolite ceramic wasteform by microwave sintering for disposition of plutonium

The application of microwave synthesis – sintering to the fabrication of zirconolite (CaZrTi2O7), as a candidate waste form for plutonium immobilization, was demonstrated as an alternative to conventional solid state reactive sintering. Ceramics of near-theoretical density were produced with a rapid dwell time of just 10 min at 1400 °C, and overall throughput time of just 60 min. In comparison with processing at 1200 °C, elevation of the processing temperature to 1400 °C significantly improved the microstructure homogeneity and reduced the porosity. The ability to sinter in air presents the potential advantage and allows for flexible control of redox conditions.

Application of zero valent iron (ZVI) immobilized in Ca-Alginate beads for C.I. Reactive Red 195 catalytic degradation in an air lift reactor operated with ozone

The efficiency of nanoscale zero-valent iron (nZVI) for the recalcitrant organic pollutants degradation has been frequently reported. However, some disadvantages such as low hydraulic conductivity, rapid passivation and consequent loss of reactivity have motivated researchers to study immobilized forms. In this work, calcium alginate beads incorporated with nZVI were prepared, characterized and applied in a catalytic ozonation system of Reactive Red 195 dye (RR195). In order to avoid shearing the calcium alginate beads, an Air lift reactor operated with Air/O3 cycles in an 8 mg L−1 concentration was used. The RR195 treatability tests conducted with a dye concentration of 25 mg L−1, 50 g L−1 of nZVI-Alg beads and an Air/O3 feed flow of 1 L min−1, revealed significant process efficiency, which was not limited only to the dye discoloration. Total discoloration levels were observed in 30 min of treatment and reductions in 97 % of organic matter in 90 min of treatment, measured through the chemical oxygen demand. The typical absorptions of aromatic compounds reduction (λmax =290 nm) and the acute toxicity reduction (Artemia Saline bioassay), contribute to the Alg-nZVI/O3 system potential for the application in the treatment of liquid effluents contaminated with dyes.

Reusable on-plate immunoprecipitation method with covalently immobilized antibodies on a protein G covered microtiter plate

Covalent immobilization of antibodies to protein G beads is a basic molecular biology method, although the beads present poor recovery results. Our aim was to reuse the immobilized antibody-protein G complex on a very small scale, therefore we optimized the crosslinking procedure to be used on the wells of a standard 96-well microplate. The method used involves the affinity binding of the antibody to the protein G surface, followed by the immobilization step using different crosslinking reagents, DMP and BS3, quenching the crosslinking reaction, and binding the antibody-specific antigen. By scaling down the procedure, we were able to reuse the anti-EGFR crosslinked wells more than 20 times. This method can be used to perform assays on a wide range of solid supports containing the protein G in an immobilized form, including functionalized nanosensors, for immunoprecipitation, protein and cell lysate purification, target protein enrichment.

Production, characterisation and immobilization of laccase for an efficient aniline-based dye decolourization

Laccase was produced by cultivation of Trametes versicolor on non-expensive substrates, barley husk and eggshell, in solid-state conditions. An efficiency of crude laccase extract in free and immobilized form for the degradation of aniline-based dye was investigated in batch experiments. Up to 91 % of dye conversion was achieved using free crude enzyme, while the use of partially purified enzyme led to 60.9 % of conversion. Crude laccase was immobilized on calcium alginate beads and used in 10 cycles-repetitive batch experiments where complete decolourization was achieved. The results of this study suggest that a) barley husk and eggshell can be used for laccase production without the need to add additional carbon and nitrogen sources or mineral compounds; b) crude laccase entrapped in alginate beads can be applied in aniline-based dye decolourization in repetitive batch experiments.

A Novel and High-Effective Biosynthesis Pathway of Hesperetin-7-O-Glucoside Based on the Construction of Immobilized Rhamnosidase Reaction Platform.

Hesperetin-7-O-glucoside (HMG) is a precursor for synthesizing a sweetener named neohesperidin dihydrochalcone, and the coordination toward flavonoids of metal ions tends to increase the water solubility of flavonoids. In order to achieve effective synthesis of HMG, an immobilized enzyme catalysis platform was constructed using an immobilized rhamnosidase on Fe3O4@graphene oxide (Fe3O4@GO), a novel reaction pathway based on the platform was designed for preparing a hesperidin complex as a soluble substrate, and ammonium hydroxide as a ligand dissociation agent to obtain HMG. The Fe3O4@GO was characterized by Fourier transform infrared (FT-IR), X-ray diffraction (XRD), scanning electron microscope (SEM), and thermal methods (TG/DSC) analysis to evaluate the immobilization matrix properties. The enzyme activity in free and immobilized form at different pH and temperature was optimized. The reusability of immobilized enzyme was also determined. In addition, the kinetic parameters (Km and Vmax) were computed after experiment. Results indicated that rhamnosidase immobilized on Fe3O4@GO using a green cross-linker of genipin hydrolyzed successfully and selectively the soluble hesperidin-Cu (II) complex into HMG-Cu (II), a permanent magnet helped the separation of immobilized enzyme and hydrolytes, and ammonium hydroxide was an effective ligand dissociation agent of translating HMG-Cu (II) into HMG with high purity determined by ultraviolet-visible (UV-Vis) spectra analysis and time-of-flight mass spectrometry (TOF-MS). As a result, a novel and high-effective biosynthesis pathway of HMG based on a selectively catalytic reaction platform were constructed successfully. The pathway based on the platform has great potential to produce valuable citrus monoglycoside flavonoid HMG, and the designed reaction route are feasible using the hesperidin-Cu (II) complex with good solubility as a reaction substrate and using ammonium water as a dissociation agent.

Adsorptive behavior of free and immobilized Chlorella pyrenoidosa for decolorization

In the present work, the potential adsorptive behavior of algal cells (Chlorella pyrenoidosa) for decolorization of dye industry wastewater has been studied in the form of free algal cells (FAC) and immobilized algal cells (IAC). Effect of concentrations of real dye industry wastewater (50 and 100%), temperatures (30, 40, 50, and 60 °C) at controlled pH, and equal amount of algal cells (2 g mL−1) have been studied. Adsorption isotherms (Langmuir and Freundlich) with kinetic and thermodynamic equations were applied to experimental data; 52–87% of decolorization was noticed with both algal cells and concentrations at room temperature. But, maximum (98%) decolorization was obtained at 50 °C with immobilized form of algal cell. Results were analyzed by Langmuir and Freundlich equations at different temperatures and were found to be more significant (R2 = 0.99) with Langmuir isotherm for adsorption with IAC. The pseudo-second-order kinetic model was also found significant (R2 = 0.90) to explain the kinetics of adsorption more efficiently. Endothermic nature reaction has been in adsorption process and thermodynamic parameters (ΔG, ΔH, and ΔS) also have been calculated. It has been concluded from the results that adsorption of the dye in wastewater that follows a pseudo-second-order kinetics provides a low-cost approach solution for treatment.

Covalent Immobilization of Naringinase over Two‐Dimensional 2D Zeolites and its Applications in a Continuous Process to Produce Citrus Flavonoids and for Debittering of Juices

AbstractThe crude naringinase from Penicillium decumbens and a purified naringinase with high α‐L‐rhamnosidase activity could be covalently immobilized on two‐dimensional zeolite ITQ‐2 after surface modification with glutaraldehyde. The influence of pH and temperature on the enzyme activity (in free and immobilized forms) as well as the thermal stability were determined using the specific substrate: p‐nitrophenyl‐alpha‐L‐rhamnopyranoside (Rha‐pNP). The crude and purified naringinase supported on ITQ‐2 were applied in the hydrolysis of naringin, giving the flavonoids naringenin and prunin respectively with a conversion >90 % and excellent selectivity. The supported enzymes showed long term stability, being possible to perform up to 25 consecutive cycles without loss of activity, showing its high potential to produce the valuable citrus flavonoids prunin and naringenin. We have also succeeded in the application of the immobilized crude naringinase on ITQ‐2 for debittering grapefruit juices in a continuous process that was maintained operating for 300 h, with excellent results.

Amano Lipase PS from Burkholderia cepacia- Evaluation of the Effect of Substrates and Reaction Media on the Catalytic Activity

: Lipases in the native or immobilized form have commonly been used as catalysts in the chemical and pharmaceutical industry. One of the widely available enzyme catalysts on the market is lipase from Burkholderia cepacia (BCLs), previously called Pseudomonas cepacia (PCLs). This enzyme is applied, among others, in the stereoselective acylation of molecules to achieve chiral pure enantiomers of drugs or their building blocks. In this study, Amano lipase PS (APS-BCL), which is a commercial lipase from Burkholderia cepacia (BC) was tested. The lipolytic activity of APS-BCL by hydrolysis of vegetable oils and enantioselective activity of APS-BCL by the kinetic resolution of (R,S)-1-phenylethanol with using isopropenyl acetate as an acyl donor were evaluated. An effect of reaction media with different logP values (t-butyl methyl ether, dichloromethane, diisopropyl ether, toluene, cyclohexane, n-hexane, isooctane and n-heptane) on the enantioselective activity of lipase was also studied. The high value of the enantiomeric ratio (E =308.5) with the utilization of isopropenyl acetate was achieved. Whereas, the best reaction medium turned out to be diisopropyl ether, C =47.9%, eep =98%, ees =90%, after 24 h of incubation. Moreover, the influence of ω6/ω9 polyunsaturated fatty acids (PUFAs) ratio in commercial (peanut, camelina, rape, pumpkin seed, walnut, sesame, avocado, rice, corn, black cumin, hemp, safflower, grape seed) oils was investigated for the lipase activity. For the first time, the cut-off limit of ω6/ω9 ratio was proposed. The ratio equal to or higher than 2.3 allows achieving higher lipolytic activity.

Synthesis and Stabilization of Support-Free Mesoporous Gold Nanoparticles.

Porous gold nanoparticles (PGNs) are usually prepared in an immobilized form on a solid substrate, which is not practical in many applications. In this work, a simple method is reported for the preparation and stabilization of mesoporous gold particles of a few hundred nanometers in size in aqueous suspension. Nanoparticles of Ag-Au alloy were fabricated on CaF and Si/SiO substrates by the solid-state dewetting method. Silver was selectively dissolved (dealloyed), and the resulting porous gold nanoparticles were chemically removed from the substrate either in a concerted step with dealloying, or in a subsequent step. Nitric acid was used for the one-step dealloying and detachment of the particles from CaF substrate. The consecutive use of HNO and HF resulted in the dealloying and the subsequent detachment of the particles from Si/SiO substrate. The PGNs were recovered from the aqueous suspensions by centrifugation. The Au content of the suspensions was monitored by using elemental analysis (ICP-OES), and recovery was optimized. The morphology and the optical characteristics of the support-free PGNs were analyzed by scanning electron microscopy (SEM), dynamic light scattering spectroscopy (DLS), and near-infrared spectrophotometry (NIR). The obtained PGNs are spherical disk-shaped with a mean particle size of 765 ± 149 nm. The suspended, support-free PGNs display an ideally narrow dipole plasmon peak at around 1450 nm in the NIR spectral region. Thus, the new colloidal PGNs are ideal candidates for biomedical applications, for instance photothermal therapy.