Immobilized Form Research Articles

Tyrosinase@HKUST-1: a super stable biocatalyst efficient for catecholic product synthesis

Although metal–organic frameworks (MOFs) have been considered as promising matrices for enzyme immobilization, HKUST-1, constructed from copper acetate (CuAc2) and benzene 1,3,5-tricarboxylate (BTC), has rarely been explored for this application. In this study, mushroom tyrosinase (EC 1.14.18.1) was immobilized in the form of tyrosinase@HKUST-1 following a simple reaction procedure by mixing BTC with the enzyme prior to addition of CuAc2. The resultant biocatalyst was characterized in both structural features and catalytic properties. Upon incorporation into the HKUST-1 frameworks, the enzyme gained a prominent enhancement in stability against pH, temperature and storage: When incubated at 50 °C and pH 6.0, tyrosinase@HKUST-1 presented a half-life of 32.6 h, which is 77-fold and over tenfold higher than that of the free enzyme and its other immobilization forms, respectively; and the catalyst fully maintained its activity for at least 2 months when stored at 30 °C. The applicability of this new biocatalyst was demonstrated by employing it as catalyst for regioselective ortho-hydroxylation reactions to produce catecholic products with huge pharmacological effects, i.e., hydroxytyrosol and l-DOPA, with excellent yields and productivities. This study has thus offered a facile immobilization method to prepare a novel biocatalyst with super stability, and tyrosinase@HKUST-1 so formed from crude mushroom extract provides an efficient catalyst which can be applied to the production of catecholic products with health benefits.Graphical

Reduction of multiple antibiotics from the waste water using coated glutathione S-transferase producing biocatalyst

Oxytetracycline is widely used in veterinary and human medicine. It has been detected in wastewater from pharmaceuticals, hospitals and domestic wastewater. In recent years, much more attention has been directed towards glutathione transferases (GSTs) because of their bio-transforming ability of antibiotics. In this study, 19 Lactobacillus strains were initially screened for the production of GSTs and five strains were selected for biotransformation of oxytetracycline. Among the strains, L. fermentum LA6 improved oxytetracyline degradation than other strains. It was subjected to optimize GST production and optimum growth was achieved after 24 h incubation at 32 ± 2 °C and 200 mg/L initial oxytetracycline concentration. The biocatalyst was immobilized and antibiotic degradation efficiency was analyzed. The immobilized culture of L. fermentum LA6 improved biodegradation of oxytetracycline in the wastewater. At 50 mg/L initial antibiotic concentration, 53.2 ± 2.8% oxytetracycline degradation was achieved, however, it improved at 200 mg/L antibiotic concentration in the culture medium (89.1 ± 4.3%) after 24 h. The chemical oxygen demand (COD) of the wastewater decreased significantly after treatment. At 200 mg/L oxytetracycline concentration, COD removal was considerably high (93.6 ± 5.3 mg/L) than 150 mg/L oxytetracycline concentration in the medium. Antibiotic removal efficiency in immobilized form revealed that this method is highly suitable for the removal of antibiotics from the wastewater.

Enhanced whole-cell biotransformation of 3-chloropropiophenone into 1-phenyl-1-propanone by hydrogel entrapped Chlorella emersonii (211.8b).

This study focuses on dehalogenation of halogenated organic substrate (3-Chloropropiophenone) using both free and hydrogel entrapped microalgae Chlorella emersonii (211.8b) as biocatalyst. We aimed at successful immobilization of C. emersonii (211.8b) cells and to assess their biotransformation efficiency. Aquasorb (entrapping material in this study) was found to be highly biocompatible with the cellular growth and viability of C. emersonii. A promising number of entrapped cells was achieved in terms of colony-forming units (CFUs = 2.1 × 104) per hydrogel bead with a comparable growth pattern to that of free cells. It was determined that there is no activity of hydrogenase that could transform 1-phenyl-2-propenone into 1-phenyl-1-propanone because after 12h the ratio between two products (0.36 ± 0.02) remained constant throughout. Furthermore, it was found that the entrapped cells have higher biotransformation of 3-chloropropiophenone to 1-phenyl-1-propanone as compared to free cells at every interval of time. 1-phenyl-2-propenone was excluded from the whole-cell biotransformation as it was also found in the control group (due to spontaneous generation). Hence, enhanced synthesis of 1-phenyl-1-propanone by entrapped Chlorella (211.8b) can be ascribed to either an enzymatic activity (dehalogenase) or thanks to the antioxidants from 211-8b, especially when they are in immobilized form. The aquasorb based immobilization of microalgae is highly recommended as an effective tool for exploiting microalgal potentials of biocatalysis specifically when free cells activities are seized due to stress.

Optimization and characterization of immobilized laccase on titanium dioxide nanostructure and its application in removal of Remazol Brilliant Blue R

The objective of this study was to determine optimum condition for immobilizing laccase onto porous TiO 2 nanostructure, and to characterize the immobilized enzyme. XRD and FTIR analyses revealed that laccase was successfully immobilized. The maximum recovery activity of 85.30 ± 0.89% was achieved when immobilization conditions were: 1.5 mg/mL laccase concentration, pH 7.0, and 18 h contact time. Shifting of optimum temperature and pH were observed after immobilization. Kinetics revealed that the immobilized form had lower substrate specificity and catalytic rate compared to the free enzyme. Storage stability of the immobilized form were improved compared to the free enzyme. Interestingly, the immobilized laccase could preserve 31.84 ± 1.86% of enzyme activity after keeping the enzyme at room temperature continuously for 14 days. Maximum RBBR removal of 76.09 ± 0.47% was achieved at pH 5.0, and repeatability of the immobilized enzyme in decolorization was performed for 3 cycles with 40% decrease in efficiency. The immobilized laccase can be removed easily from the solution using forceps without further separation processes. • Combination of laccase enzyme and nanostructure was applied to produce the nanobiocatalyst. • Laccase was successfully immobilized on nano TiO 2 using covalent binding method. • Stability, durability, and reusability of the immobilized laccase were improved. • Maximum RBBR decolorization of the immobilized laccase was 76.09 ± 0.47% at pH 5.0. • After completion of the reaction, the immobilized laccase can be easily separated.

An evaluation into the biosorption and biodegradation of azo dyes by indigenous siderophores-producing bacteria immobilized in chitosan.

The biodegradation and biosorption efficiency of an indigenous siderophores-producing bacterial community on azo dyes with immobilization in chitosan beads was evaluated in this study. 13 bacterial strains were isolated from textile wastewater streams. The bacterial strains were tested for the production of siderophores as well as their ability to decolorize toxic azo dyes in aqueous solution. Both qualitatively and quantitatively, all of the strains displayed high siderophores productivity. Furthermore, they displayed remarkable decolorization efficiency for azo dyes (Acid Black 1 and Reactive Black 5) in both free and immobilized form. The immobilization process was found not only to enhance the decolorization but also the degradation of azo dyes by the bacterial isolates. In a SEM micrograph, bacterial strains were immobilized, and the pores in chitosan bead to be trapped and adsorbed for dyes from synthetic wastewater. The extent of dye compounds degradation were examined using UV-visible and FTIR spectrophotometers on treated water samples and dye absorbed beads. After 72h of incubation, the UV-visible analysis revealed that the bacterial community could significantly reduce both azo dyes in wastewater by 90% at 300 mgL-1 dyes initial concentration. FTIR study confirmed the bonds of these dyes were broken to form less toxic chemicals via the bacterial community immobilized in chitosan beads. The immobilized bacterial community thus demonstrated effective approach of azo dye biosorption and biodegradation.

Polysaccharides as Support for Microbial Biomass-Based Adsorbents with Applications in Removal of Heavy Metals and Dyes.

The use of biosorbents for the decontamination of industrial effluent (e.g., wastewater treatment) by retaining non-biodegradable pollutants (antibiotics, dyes, and heavy metals) has been investigated in order to develop inexpensive and effective techniques. The exacerbated water pollution crisis is a huge threat to the global economy, especially in association with the rapid development of industry; thus, the sustainable reuse of different treated water resources has become a worldwide necessity. This review investigates the use of different natural (living and non-living) microbial biomass types containing polysaccharides, proteins, and lipids (natural polymers) as biosorbents in free and immobilized forms. Microbial biomass immobilization performed by using polymeric support (i.e., polysaccharides) would ensure the production of efficient biosorbents, with good mechanical resistance and easy separation ability, utilized in different effluents’ depollution. Biomass-based biosorbents, due to their outstanding biosorption abilities and good efficiency for effluent treatment (concentrated or diluted solutions of residuals/contaminants), need to be used in industrial environmental applications, to improve environmental sustainability of the economic activities. This review presents the most recent advances related the main polymers such as polysaccharides and microbial cells used for biosorbents production; a detailed analysis of the biosorption capability of algal, bacterial and fungal biomass; as well as a series of specific applications for retaining metal ions and organic dyes. Even if biosorption offers many advantages, the complexity of operation increased by the presence of multiple pollutants in real wastewater combined with insufficient knowledge on desorption and regeneration capacity of biosorbents (mostly used in laboratory scale) requires more large-scale biosorption experiments in order to adequately choose a type of biomass but also a polymeric support for an efficient treatment process.

Investigation of Ferrochromium Wastes for their Hazardous Hexavalent Chromium Content

In this study, ferrochromium slag (FS) and electric-arc furnace dust (EAFD) samples were examined for their hazardous hexavalent chromium content mainly by X-ray photoelectron spectroscopy (XPS) analysis. According to the experimental results, magnesium-silicate constitutes the main framework of both FS and EAFD samples. Highly crystalline FS contains 3.11%Cr2O3 as spinel phases while this constituent is much higher, 15.44%, in EAFD. The general XPS spectra show that both samples mainly consist of O, Mg and Si elements. In addition, FS also includes aluminum while carbon, calcium and potassium are the other major elements for EAFD. The peaks appeared in the range of 577-589 eV confirm chromium content of the samples. Besides, the peaks appeared at 1022 and 1045 eV point out zinc content of EAFD. Based on the XPS atomic ratio, Cr contents of FS and EAFD were obtained as 0.505 and 0.987%, respectively while EAFD further contains 2.594% Zn. The detailed XPS analysis indicates that chromium exists as two oxidation states, trivalent and hexavalent forms at 2p orbitals. Specifically, for 2p3/2 orbitals, trivalent and hexavalent chromium were assigned at 577.1 and 579.2 eV, respectively whereas 586.9 and 588.9 eV for 2p1/2 orbitals. Furthermore, the corresponding intensities of these peaks are much higher for EAFD. By comparing the peak intensities, the relative proportions of Cr (VI) were calculated as 49.44 and 49.53% for FS and EAFD, respectively. The leaching tests show that solubilities of all the metals examined except Cr are far below the toxicity limits for hazardous waste and even below the ranges of non-hazardous waste. Specifically, chromium contents of the filtrates were determined as 0.862 and 268.050 mg/l for FS and EAFD, respectively. Considering the toxicity limits of chromium, EAFD can be surely labeled as a highly hazardous waste whereas, on the other hand, FS is within the limits of non-hazardous waste. In conclusion, it can be said that the hazardous hexavalent chromium content must be reduced to immobile trivalent forms for the dust sample prior to disposed in landfills.

Phase assemblage and microstructures of Gd2Ti2-xZrxO7 (x = 0.1–0.3) pyrochlore glass-ceramics as potential waste forms for actinide immobilization

Glass-ceramics (GCs) based on titanate pyrochlores have attracted recent attention as candidate waste forms for actinide immobilization. As zirconate pyrochlore has a superior radiation resistance, it is anticipated that Zr substitution of Ti in titanate pyrochlore GCs would increase their potential for waste form applications. The concept was primarily addressed via the preparation of Gd2Ti2-xZrxO7 (x = 0.1–0.3) GCs to determine the effects of sintering temperature, Zr substitution, and pyrochlore content (50–70 wt%) on the properties of the resultant GCs. XRD and SEM analyses were used to reveal the phase assemblages and microstructures while TEM and Raman spectroscopy were used to analyze the local structures. XRD results confirmed the formation of the targeted pyrochlore as the major phase, with Gd9.33(SiO4)6O2 oxyapatite present as a minor phase. SEM analyses revealed that up to 0.2 formula units of Ti could be substituted by Zr under the processing conditions. The pyrochlore crystallite sizes were largely controlled by the sintering temperature and cooling rate and showed little sensitivity to the glass contents. This work has demonstrated successful substitutions of Ti with Zr in Gd2Ti2O7 GCs as potential waste forms for actinide wastes owing to their superior radiation resistance.

Kinetic and thermodynamic study of laccase cross-linked onto glyoxyl Immobead 150P carrier: Characterization and application for beechwood biografting

In this study, we cross-linked aminated Thermothelomyces thermophilus laccase onto Immobead 150P epoxy carrier, and achieved an immobilization yield of 99.84 %. The optimum temperature and pH values for the oxidation of ABTS by laccase were determined to be 70 °C and pH 3.0. After 6 h at 50 °C, laccase activity was diminished by about 13 % in the free form and 28 %, in the immobilized form. Km values for both free and cross-linked laccase were 0.051 and 0.567 mM, whereas Vmax values were 2.027 and 0.854 μmol. min−1, respectively. The immobilized laccase was able to preserve its full activity for 6 weeks, retaining approximately 95 % and 78 % of its initial activity after 8 and 20 weeks, respectively. The contact angles were two-fold higher when the laccase enzyme was occupied in the biografting reaction, revealing that the hydrophobic compound bonded stably onto beechwood samples.

Challenges and perspectives of the β-galactosidase enzyme.

The enzyme β-galactosidase has great potential for application in the food and pharmaceutical industries due to its ability to perform the hydrolysis of lactose, a disaccharide present in milk and in dairy by-products. It can be used in free form, in batch processes, or in immobilized form, which allows continuous operation and provides greater enzymatic stability. The choice of method and support for enzyme immobilization is essential, as the performance of the biocatalyst is strongly influenced by the properties of the material used and by the interaction mechanisms between support and enzyme. Therefore, this review showed the main enzyme immobilization techniques, and the most used supports for the constitution of biocatalysts. Also, materials with the potential for immobilization of β-galactosidases and the importance of their biotechnological application are presented. KEY POINTS: • The main methods of immobilization are physical adsorption, covalent bonding, and crosslinking. • The structural conditions of the supports are determining factors in the performance of the biocatalysts. • Enzymatic hydrolysis plays an important role in the biotechnology industry.

Biodiesel Synthesis through the Non-Alcohol Route using the Immobilized Lipase Enzyme from Bacillus subtilis as Biocatalyst

Biodiesel is one alternative energy that might be promising to substitute the petroleum-based fuel due to its biodegradability and less toxic level. Biodiesel can be synthesized through the non-alcohol route by substituting the alcohol with methyl acetate using lipase enzyme as the Biocatalyst, which may give less by-product during the reaction. In this research, lipase from Bacillus subtilis has been produced and prepared in a crude, dry and immobilized form. It is used as the Biocatalyst for biodiesel synthesis. Several variables were investigated for obtaining the optimum condition in producing biodiesel, including the form of lipase enzyme, the variation of molar ratio between oil and methyl acetate, and the enzyme concentration. The immobilized Bacillus subtilis lipase enzyme loading was also calculated to know how many percent of the lipase is successfully immobilized. The biodiesel produced using lipase from Bacillus subtilis will then be compared with the biodiesel produced using Candida rugosa commercial lipase. Based on the experimental, the immobilized lipase with 1:12 of oil to methyl acetate and enzyme concentration of 2% gives the highest biodiesel yield among the others, as much as 53.99%. This yield was higher than the biodiesel produced using Candida rugosa lipase. In conclusion, the immobilized lipase from Bacillus subtilis is one of the promising Biocatalyst for biodiesel production.

Investigation of the insulating properties of the Cherkasy deposit clays for the creation of underlying screens of radioactive waste at the ‘Vector’ site

The lack of scientifically substantiated requirements, comprehensively developed and approved in a prescribed manner, for the usage of clays as a barrier material poses risks for the safe disposal of radioactive waste in facilities at the ‘Vector’ site for the period of their operation and closure. The bentonite clay from Ukraine’s largest Cherkasy deposit of bentonite and palygorskite clays is considered the most durable as the main component of the insulating (underlying) screens of radioactive waste disposal facilities. The main properties and compositional features of the Cherkasy natural bentonite clay (Dashukovskaya site, layer II) and its variety such as alkaline earth bentonite (activated soda bentonite), which provide isolation of radioactive waste in disposal, are considered. It is shown that the Cherkasy field has good waterproofing and barrier properties, including a high sorption capacity with respect to 90Sr and 137Cs, which is one of the main characteristics that ensure the safe disposal of radioactive waste. The alkaline earth bentonite absorbs 90Sr and 137Cs more efficiently than natural bentonite does. However, 90Sr is sorbed in larger quantities than 137Cs on both types of bentonite. With increasing time of interaction with an aqueous solution, both types demonstrate a redistribution of the mobile (exchangeable) and immobile (non-replaceable) forms of radionuclides. The contribution of the stationary form that does not participate in migration processes also increases. A comprehensive analysis of the bentonite clays of the Cherkasy deposit was carried out, taking into account the significance of recoverable reserves and the potential for improving the technical and economic parameters of clays. Thus, the Cherkasy bentonite clays can be recommended as an additional anti-migration engineering barrier for ground/near-surface facilities for the disposal of radioactive waste. When choosing the type of bentonite clay for use as a barrier in a radioactive waste disposal facility, one could take into account the data published in the article, but the question of applying the bentonite clays of the Cherkasy deposit to ensure the safe disposal of radioactive waste remains to be further studied.

Solidification of municipal solid waste incineration fly ash and immobilization of heavy metals using waste glass in alkaline activation system

Hazardous heavy metals in Municipal Solid Waste Incineration (MSWI) fly ash are a threat to the environment and ecosystems. The objective of the work is to investigate the solidification of MSWI fly ash and the immobilization of the heavy metals through alkaline activation reaction with waste glass as an additive. Compressive strength measurement, X-ray diffraction (XRD), 29Si nuclear magnetic resonance spectroscopy (29Si NMR) and scanning electron microscope (SEM) were performed to evaluate the solidification effect and characterize the microstructure of alkali-activated MSWI fly ash-based mortars. The leaching test, back-scattered electron microscopy (BSE) and X-ray photoelectron spectroscopy (XPS) were conducted to determine the heavy metals' immobilization effect and their immobilization forms. It was found that waste glass addition effectively reinforced the solidification of MSWI fly ash and immobilized the heavy metals. With 40% addition of waste glass, the compressive strength reached a maximum of 3.55 MPa. The immobilization efficiency of Cr increased with the addition of waste glass, while that of Cu, Pb, Zn and Cd is dependent on the eluant final pH, which decreased with the decrease of eluant final pH. The main immobilization forms include physical encapsulation, the formation of alkaline environment and the generation of silicate compounds.

Development of geopolymer waste form for immobilization of radioactive borate waste

Radioactive borate waste containing a high concentration of boron (B) is problematic to be solidified using cement because soluble borate such as boric acid hinders the hydration reaction. In this study, borate waste was used as a raw material for metakaolin-based geopolymer according to the characteristic that B replaces a part of Si. Geopolymers using KOH alkaline activator (K-geopolymers) showed higher compressive strength than geopolymers using NaOH alkaline activator (Na-geopolymer). In addition, the compressive strength increased proportionally to the Si/(Al+B) ratio regardless of the alkaline cation species. These variations in compressive strength might be due to the viscosity of the geopolymer mixture, atomic size of alkaline cations, and the increase in Si content. The characteristic analyses (XRD, FT-IR, and solid state 11B MAS NMR) indicated that B was incorporated into the geopolymer structure. Thus, the K-geopolymer has a dense and homogeneous microstructure. In a semi-dynamic leaching test, less B leached from the geopolymers compared to the cement waste form. Consequently, borate waste can be solidified using metakaolin-based geopolymer, and the use of a KOH alkaline activator is advantageous in terms of mechanical property and structural durability.

Cr(VI) bioremediation by active algal-bacterial aerobic granular sludge: Importance of microbial viability, contribution of microalgae and fractionation of loaded Cr

In this study, chromium (Cr) was used as an example of the most toxic heavy metals that threaten human health, and Cr(VI) bioremediation was implemented by using a new type of aerobic granular sludge (AGS), i.e., algal-bacterial AGS. Results showed that the total Cr removal efficiency by active algal-bacterial AGS was 85.1 ± 0.6% after 6 h biosorption at pH 6 and room temperature, which could be further improved to 93.8 ± 0.4% with external electron donor (glucose) supply. However, inactivation dramatically decreased the total Cr removal efficiency to 29.6 ± 3.5%, and no effect was noticed when external electron donor was provided. With an antibiotic (levofloxacin) or metabolic inhibitor (NaN3) addition, the total Cr removal efficiency of bacterial AGS was inhibited by 16.0% or 10.1%, but this efficiency was maintained in the case of algal-bacterial AGS. Analysis of extracellular polymeric substances (EPS) composition revealed that under Cr(VI) exposure, more loosely bound EPS were secreted by algal-bacterial AGS, favoring Cr(VI) reduction. Results from chemical fractionation indicated that 90.5 ± 4.2% of the loaded Cr on algal-bacterial AGS was in an immobile form, reflecting the low environmental risk of Cr-loaded algal-bacterial AGS after biosorption of hazardous heavy metals from wastewater.

Metal Affinity Immobilization of the Processive Endoglucanase EG5C-1 from Bacillus subtilis on a Recyclable pH-Responsive Polymer

Establishing a suitable immobilization strategy to improve the accessibility of immobilized cellulase for insoluble cellulose and subsequently recover the enzyme from the remaining substrate is crucial to promote the industrialization of biofuels. Here, using iminodiacetic acid (IDA) and Ni2+ ions, a novel metal-chelated copolymer of methacrylic acid and methyl methacrylate was prepared for the immobilization of His-tagged processive endoglucanase EG5C-1 via affinity interaction between polyhistidine tag and Ni2+. The optimum loading capacity of the functionalized polymer (Eud-IDA-Ni2+) for EG5C-1 was about 280 mg/g, where more than 80% of the activity was recovered. Immobilized EG5C-1 exhibited improved thermal and pH stability and better reusability than the free one, and after five cycles of usage, the hydrolysis productivity remained above 70% of the initial value. The Eud-IDA-Ni2+/EG5C-1 biocomposite displayed reversibly soluble–insoluble characteristics with pH change, which was in the soluble state during the enzyme reaction process but could be recovered in an insoluble form by lowering the pH after the reaction. Thus, the yield obtained from the hydrolysis of an insoluble phosphoric acid-swollen cellulose substrate was similar for the free and immobilized form of EG5C-1. Our combined results suggested that a metal-ion-chelated, pH-responsive polymer had the potential for His-tagged cellulase immobilization to improve both the operational efficiency and economic benefit of the cellulosic biorefinery industry.

Mercury vertical and horizontal concentrations in agricultural soils of a historically contaminated site: Role of soil properties, chemical loading, and cultivated plant species in driving its mobility

The long term vertical and horizontal mobility of mercury (Hg) in soils of agricultural areas of a historically contaminated Italian National Relevance Site (SIN Brescia-Caffaro) was investigated. The contamination resulted from the continuous discharge of Hg in irrigation waters by an industrial plant (Caffaro S.p.A), equipped with a mercury-cell chlor-alkali process. The contamination levels with depth ranged from about 20 mg/kg dry weight (d.w.) of soil in the top (plow) layer to less than 0.1 mg/kg d.w. at 1 m depth. The concentrations varied also spatially, up to one order of magnitude within the same field and showing a decreasing trend from the Hg source (i.e., irrigation ditches). The concentration profiles and gradients measured were explained considering Hg loading, soil properties, such as the texture, organic carbon content, pH and cation exchange capacity. A Selective Sequential Extraction (SSE) was also applied on soil samples from an ad hoc greenhouse experiment to investigate the role of different plant species in influencing Hg speciation in soils. Although most of the extracted Hg was included in scarcely mobile or immobile forms, some plant species (i.e., alfalfa) showed to importantly increase the soluble and exchangeable fractions with respect to the unplanted control soils, thus affecting mobility and potential bioavailability of Hg.

Enhanced Stability of Long-Living Immobilized Recombinant β-d-N-Acetyl-Hexosaminidase A on Polylactic Acid (PLA) Films for Potential Biomedical Applications.

β-d-N-acetyl-hexosaminidase (Hex, EC 3.2.1.52) is an acid hydrolase that catalyzes the cleavage of the β-1,4 bond in N-acetyl-d-galactosamine (Gal-NAc) and N-acetyl-d-glucosamine (Glc-NAc) from the non-reducing end of oligosaccharides and glycoconjugates. It is widely expressed in both the prokaryotic and eukaryotic world, where it performs multiple and important functions. Hex has antifungal activity in plants, is capable of degrading many biological substrates, and can play an important role in the biomedical field for the treatment of Tay-Sachs and Sandhoff diseases. With the aim being able to obtain a device with a stable enzyme, a method of covalent immobilization on polylactic acid (PLA) films was developed for the A isoform of the β-d-N-acetyl-hexosaminidase enzyme (HexA), produced in a recombinant way from Human Embryonic Kidney-293 (HEK-293) cells and suitably purified. An in-depth biochemical characterization of the immobilized enzyme was carried out, evaluating the optimal temperature, thermal stability, pH parameters, and Km value. Moreover, the stability of the enzymatic activity over time was assessed. The results obtained showed an improvement in terms of kinetic parameters and stability to heat for the enzyme following immobilization and the presence of HexA in two distinct immobilized forms, with an unexpected ability for one of them to maintain its functionality for a long period of time (over a year). The stability and functionality of the enzyme in its immobilized form are therefore extremely promising for potential biotechnological and biomedical applications.

Impact of pH on Pollutional Parameters of Textile Industry Wastewater with Use of Chlorella pyrenoidosa at Lab‐Scale: A Green Approach

The current study focused on the pollution remediation of textile industry wastewater by using Chlorella pyrenoidosa in two different physical forms: free algal biomass and immobilized algal biomass. The hypothesis behind the present study was to analyze the pollution reduction efficiency of immobilized algal biomass and free algal biomass on comparative scale on the basis of the adsorption process which is directly proportional with the surface area of the adsorbate. So, in this context the immobilized form of algae could enhance the pollution reduction efficiency due to availability of more surface area. So, the textile industry wastewater was treated by both free algal biomass and immobilized algal biomass and the major wastewater contributors like nitrate, phosphate, Biochemical Oxygen Demand (BOD) and Chemical Oxygen Demand (COD) were assessed before and after the treatment process. To conclude the optimum comparative results, the pH of wastewater was maintained constant, as it can capitalize or moderate the adsorption process (initial pH of was 8.2 ± 0.1, but it was maintained to 8). The contamination remediation was found to be effective with immobilized algal biomass (46.7% of nitrate, 59.4% of phosphate, 83.1% BOD and 83.0% of COD) than free algal biomass (43.2% of nitrate, 56.7% of phosphate, 71.4% of BOD and 78.0% COD).

Biosorption of CU(II) Ions by Leucaena Leucocephala Leave from Aqueous Solution

As a preliminary study, this project aims to remove the copper (Cu II) from aqueous solutions using Leucaena leucocephala leaves. Effect of free cell and immobilized form of biosorbent on adsorption capacity were evaluated in this study. Kinetic models of pseudo-first order, second order and equilibrium isotherms of Langmuir and Freundlich were used to predict the efficiency of Cu 2+ absorption by Leucaena leucocephala leaves adsorption system. The functional groups involved during the adsorption were identified using Fourier Transform Infrared (FTIR) whereby the Leucaena leucocephala leaves has the large amount of hydroxyl functional groups at the wavelength of 3411.66 cm -1. Atomic Absorption Spectroscopy (AAS) were used to measure the metal concentration before and after the adsorption process. The maximum percentage removal of the Cu 2+ was achieved by immobilized form of Leucaena leucocephala leaves as biosorbent in aqueous solutions with a 72.3% of removal. Adsorption kinetics of pseudo-second order was well fitted with the adsorption data with the R 2 of 0.9622. In addition, the results reveal that Langmuir isotherm was the best model to explain the adsorption of Cu 2+ using immobilized Leucaena leucocephala leaves with the R 2 of 0.9974. This result showed that Leucaena leucocephala leaves as an effective and potential biosorbent for the adsorption of Cu 2+ from the wastewater.