Alginate–poly(vinyl alcohol) core–shell microspheres for lipase immobilization

Comparative Analysis of Crosslinking Methods and Their Impact on the Physicochemical Properties of SA/PVA Hydrogels

Hydrogels, versatile materials used in various applications such as medicine, possess properties crucial for their specific applications, significantly influenced by their preparation methods. This study synthesized 18 different types of hydrogels using sodium alginate (SA) and two molecular weights of polyvinyl alcohol (PVA). Crosslinking agents such as aqueous solutions of calcium (Ca2+) and copper (Cu2+) ions and solutions of these ions in boric acid were utilized. The hydrogels were subjected to compression strength tests and drying kinetics analysis. Additionally, six hydrogel variants containing larger PVA particles underwent Fourier-transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA) post-drying. Some samples were lyophilized, and their surface morphology was examined using scanning electron microscopy (SEM). The results indicate that the choice of crosslinking method significantly impacts the physicochemical properties of the hydrogels. Crosslinking in solutions with higher concentrations of crosslinking ions enhanced mechanical properties and thermal stability. Conversely, using copper ions instead of calcium resulted in slower drying kinetics and reduced thermal stability. Notably, employing boric acid as a crosslinking agent for hydrogels containing heavier PVA molecules led to considerable improvements in mechanical properties and thermal stability.

Biocatalytic Profiling of Free and Immobilized Partially Purified Alkaline Protease from an Autochthonous Bacillus aryabhattai Ab15-ES

Partially purified alkaline protease produced by an indigenous bacterial strain, Bacillus aryabhattai Ab15-ES, was insolubilized in alginate beads using an entrapment technique. Maximum entrapped enzyme activities of 68.76% and 71.06% were recorded at optimum conditions of 2% (w/v) sodium alginate and 0.3 M calcium chloride. Biochemical profiling of free and immobilized proteases was investigated by determining their activity and stability as well as kinetic properties. Both enzyme preparations exhibited maximum activity at the optimum pH and temperature of 8.0 and 50 °C, respectively. However, in comparison to the free enzyme, the immobilized protease showed improved pH stability at 8.0–9.0 and thermal stability at 40–50 °C. In addition, the entrapped protease exhibited a higher Vmax and increased affinity to the substrate (1.65-fold) than the soluble enzyme. The immobilized protease was found to be more stable than the free enzyme, retaining 80.88% and 38.37% of its initial activity when stored at 4 °C and 25 °C, respectively, for 30 d. After repeated use seven times, the protease entrapped in alginate beads maintained 32.93% of its original activity. These findings suggest the efficacy and sustainability of the developed immobilized catalytic system for various biotechnological applications.

Sustainable production and co-immobilization of cold-active enzymes from Pseudomonas sp. for BTEX biodegradation

Toluene/o-Xylene Monooxygenase (ToMO) is equipped with a broad spectrum of aromatic substrate specificity (such as BTEX; benzene, toluene, ethylbenzene, and isomers of xylenes). TOMO has can hydroxylate more than a single position of aromatic rings in two consecutive monooxygenation reactions. Catechol 1,2-dioxygenase (C1,2D) is an iron-containing enzyme able to cleave the ring of catechol (the converted product from ToMO) for complete detoxification of BTEX. In this study, cold-active ToMO and C1,2D were produced using newly isolated psychrophilic Pseudomonas S2TR-14 in the minimal salt medium supplemented with crustacean waste and different concentrations of used motor oil (0.2-2% (v/v)). Crude ToMO and C1,2D were immobilized into micro/nano biochar-chitosan matrices and used for BTEX biodegradation. The results showed that the highest enzyme production (12 U/mg for ToMO and 22 U/mg for C1,2D) was achieved at the presence of 0.5% v/v used motor oil compared to the control group without motor oil (0.07 and 0.06 U/mg). High immobilization yield was achieved due to covalent bonding of ToMO (92.26% for micro matrix and 77.20% for nano matrix) and C1,2D (87.57% for micro matrix and 74.79% for nano matrix) with matrices. FTIR spectra confirmed the immobilization of enzymes on the surface of microbiochar and nanobiochar-chitosan matrices as proper support. The immobilization increased the storage stability of the enzymes with more than 50% residual activity after 30 days at 4 ± 1 °C, while the free form of enzymes had less than 10% of its activity. Immobilized enzymes degraded more than 80% of BTEX (~200 mg/L in groundwater and ~10,000 mg/kg in soil) at 10 ± 1 °C in groundwater and soil. Therefore, integrated use of microbiochar and nanobiochar with chitosan for co-immobilization of ToMO and C1,2D can be a potential way to remove petroleum hydrocarbons with higher efficiency from contaminated groundwater and soil.

Utilization of different polymers for the improvement of catalytic properties and recycling efficiency of bacterial maltase

Current study deals with the comparative study related to immobilization of maltase using synthetic (polyacrylamide) and non-synthetic (calcium alginate, agar-agar and agarose) polymers via entrapment technique. Polyacrylamide beads were formed by cross-linking of monomers, agar-agar and agarose through solidification while alginate beads were prepared by simple gelation. Results showed that the efficiency of enzyme significantly improved after immobilization and among all tested supports agar-agar was found to be the most promising and biocompatible for maltase in terms of immobilization yield (82.77%). The catalytic behavior of maltase was slightly shifted in terms of reaction time (free enzyme, agarose and polyacrylamide: 5.0 min; agar-agar and alginate: 10.0 min), pH (free enzyme, alginate and polyacrylamide: 6.5; agar-agar, agarose: 7.0) and temperature (free enzyme: 45 °C; alginate: 50 °C; polyacrylamide: 55 °C; agarose: 60 °C; agar-agar: 65 °C). Stability profile of immobilized maltase also revealed that all the supports utilized have significantly enhanced the activity of maltase at higher temperatures then its free counterpart. However, recycling data showed that agar-agar entrapped maltase retained 20.0% of its initial activity even after 10 cycles followed by agarose (10.0%) while polyacrylamide and alginate showed no activity after 8 and 6 cycles respectively.

Improvement of lipase biochemical properties via a two-step immobilization method: Adsorption onto silicon dioxide nanoparticles and entrapment in a polyvinyl alcohol/alginate hydrogel

In this study, the factors affecting lipase adsorption onto SiO₂ nanoparticles including SiO₂ nanoparticles amounts (8, 19 and 30 mg/mL), lipase concentrations (30, 90 and 150 μg/mL), adsorption temperatures (5, 20 and 35 °C) and adsorption times (1, 12.5 and 24 h) were optimized using central composite design. The optimal conditions were determined as a SiO₂ nanoparticles amount of 8.5-14 mg/ml, a lipase concentration of 106-116 μg/mL, an adsorption temperature of 20 °C and an adsorption time of 12.5 h, which resulted in a specific activity and immobilization efficiency of 20,000 (U/g protein) and 60 %, respectively. The lipase adsorbed under optimal conditions (SiO₂-lipase) was entrapped in a PVA/Alg hydrogel, successfully. FESEM and FTIR confirmed the two-step method of lipase immobilization. The entrapped SiO₂-lipase retained 76.5 % of its initial activity after 30 days of storage at 4 °C while adsorbed and free lipase retained only 43.4 % and 13.7 %, respectively. SiO₂-lipase activity decreased to 34.43 % after 10 cycles of use, while the entrapped SiO₂-lipase retained about 64.59 % of its initial activity. Compared to free lipase, the K_m values increased and decreased for SiO₂-lipase and entrapped SiO₂-lipase, respectively. V_max value increased for both SiO₂-lipase and entrapped SiO₂-lipase.

Enhancement of biochemical aspects of lipase adsorbed on halloysite nanotubes and entrapped in a polyvinyl alcohol/alginate hydrogel: strategies to reuse the most stable lipase

Entrapment of halloysite nanotubes (HNTs) loaded with enzyme, into a polymer matrix (PVA/Alg), is a way to produce an environment surrounding the adsorbed enzyme molecules which improves the enzyme properties such as storage and operational stability. Hence, in this study, we optimised the factors affecting lipase adsorption onto halloysite nanotubes including halloysite amounts (5, 42.5 and 80 mg), lipase concentrations (30, 90 and 150 µg/ml), temperatures (5, 20 and 35 °C) and adsorption times (30, 165 and 300 min). The optimal conditions were determined as an halloysite amount of 50 to 80 mg, a lipase concentration of 30 to 57 μg/ml, an adsorption temperature of 20 °C and an adsorption time of 165 min, which resulted in a specific activity and adsorption efficiency of 15,000 (U/g protein) and 70%, respectively. Then, lipase adsorbed under optimal conditions was entrapped in a PVA/Alg hydrogel. The formation mechanism of immobilized lipase was investigated by FESEM and FTIR. Subsequent entrapment of adsorbed lipase improved the lipase storage and operational stability. K_m, V_max, K_cat and K_cat/K_m values showed an increase in the entrapped HNT-lipase performance in comparison with the free and adsorbed lipase.

Chairside fabrication of provisional crowns on FDM 3D-printed PVA model

PURPOSE

The purpose of this study was to evaluate the dimensional accuracy of crowns fabricated using a polyvinyl alcohol (PVA) dental model.

METHODS

An intraoral scanner (LAVA TDS) was used to scan a prepared molar abutment as a master model. The STL file obtained from the scanning process was transferred into the FDM 3D printer (Value 3D Magix MF-1000) and then models were fabricated with PVA filament. In order to compare with the conventional method, an impression of the master model was taken using silicone impression material to fabricate the conventional stone cast model (Conv). An indirect resin composite (Gradia) and self-cured acrylic resin (Curergrace) were used to fabricate crowns (n = 20) according to the manufacturer's instructions. Surface accuracy of the Conv and PVA models and internal accuracy of the crowns set on the models were measured using two methods; 3D digital analysis and silicon-fitting evaluation. Statistical analysis of the results was done using t-test and Willcoxon signed rank test with Bonferroni correction at 5% significance.

RESULTS

Digital analysis showed the Root Mean Square (RMS) value of PVA model surface was higher than that of Conv, while there was no significant difference between the two crown materials. However, the silicon-fitting analysis showed marginal discrepancy of crowns fabricated on PVA model were within 100 µm.

CONCLUSION

3D printed PVA model can be used for chairside crown fabrication with an acceptable accuracy.

Maltose deterioration approach: Catalytic behavior optimization and stability profile of maltase from Bacillus licheniformis KIBGE-IB4

Maltase is an economically valuable enzyme that is used to catalyze the hydrolytic process of maltose and yields d-glucose as a product. In this study, the catalytic behavior of maltase was optimized under various physicochemical condition. Results indicated that bacterial maltase exhibited maximum catalytic activity at 45 °C and pH-6.5 after 5.0 min. It presented greater stability within 0.1 M K2HPO4 buffer having pH-6.5 and showed 100 % activity even after 1.0 h. It retained 83.6 % and 45.0 % activity at 40 °C after 1.0 and 3.0 h, respectively. The enzyme retained 90.0 % activity at -20 °C even after 60 days. The molecular weight of enzyme was deduced to be 157.2 kDa as calculated using polyacrylamide gel electrophoresis (PAGE) and zymography. It was concluded that the characterized maltase has notable stability profile with reference to temperature, pH and other reaction conditions which anticipates its utilization in various starch and maltose hydrolyzing processes for the synthesis of glucose.

Reduction of Phytic Acid in Soymilk by Immobilized Phytase System

In this study, three carriers (glass microsphere, cellulose beads and AlgNa/PVA beads) were evaluated as phytase solid carriers for reduction of phytic acid within soymilk. Phytase was covalently immobilized onto or entrapped within carriers for repeated use. Glass microsphere was chosen due to its high catalytic efficiency. Optimal operating condition (pH 6.0, 60 °C) was determined using 4-Nitrophenyl phosphate disodium salt hexahydrate as an indicator. Operational reusability was confirmed for more than seven batch reactions and the storage stability was capable of sustaining 70% of its catalytic activity for 40 days. The kinetic parameters including rate constant (K), time (τ₅₀ ) in which 50% of phytic acid hydrolysis was reached, and time (τ_complete ) required to achieve complete phytic acid hydrolysis, were 0.023 min^-1 , 35.7 min, 110 min. The current procedure provides a cheap as well as an easy way to carry out the reduction of phytic acid in soymilk, which has great potential in practical application.

Immobilization and characterization of lipase from an indigenous Bacillus aryabhattai SE3-PB isolated from lipid-rich wastewater

Extracellular lipase from an indigenous Bacillus aryabhattai SE3-PB was immobilized in alginate beads by entrapment method. After optimization of immobilization conditions, maximum immobilization efficiencies of 77% ± 1.53% and 75.99% ± 3.49% were recorded at optimum concentrations of 2% (w/v) sodium alginate and 0.2 M calcium chloride, respectively, for the entrapped enzyme. Biochemical properties of both free and immobilized lipase revealed no change in the optimum temperature and pH of both enzyme preparations, with maximum activity attained at 60 °C and 9.5, respectively. In comparison to free lipase, the immobilized enzyme exhibited improved stability over the studied pH range (8.5-9.5) and temperature (55-65 °C) when incubated for 3 h. Furthermore, the immobilized lipase showed enhanced enzyme-substrate affinity and higher catalytic efficiency when compared to soluble enzyme. The entrapped enzyme was also found to be more stable, retaining 61.51% and 49.44% of its original activity after being stored for 30 days at 4 °C and 25 °C, respectively. In addition, the insolubilized enzyme exhibited good reusability with 18.46% relative activity after being repeatedly used for six times. These findings suggest the efficient and sustainable use of the developed immobilized lipase for various biotechnological applications.

Synthesis of Benzyl Acetate Catalyzed by Lipase Immobilized in Nontoxic Chitosan-Polyphosphate Beads

Enzymes serve as biocatalysts for innumerable important reactions, however, their application has limitations, which can in many cases be overcome by using appropriate immobilization strategies. Here, a new support for immobilizing enzymes is proposed. This hybrid organic-inorganic support is composed of chitosan-a natural, nontoxic, biodegradable, and edible biopolymer-and sodium polyphosphate as the inorganic component. Lipase B from Candida antarctica (CALB) was immobilized on microspheres by encapsulation using these polymers. The characterization of the composites (by infrared spectroscopy, thermogravimetric analysis, and confocal Raman microscopy) confirmed the hybrid nature of the support, whose external part consisted of polyphosphate and core was composed of chitosan. The immobilized enzyme had the following advantages: possibility of enzyme reuse, easy biocatalyst recovery, increased resistance to variations in temperature (activity declined from 60 °C and the enzyme was inactivated at 80 °C), and increased catalytic activity in the transesterification reactions. The encapsulated enzymes were utilized as biocatalysts for transesterification reactions to produce the compound responsible for the aroma of jasmine.

Immobilized laccase on oxygen functionalized nanobiochars through mineral acids treatment for removal of carbamazepine

Biocatalytic treatment with oxidoreductase enzymes, especially laccases are an environmentally benign method for biodegradation of pharmaceutical compounds, such as carbamazepine to less harmful compounds. However, enzymes are required to be immobilized on supports to be reusable and maintain their activity. Functionalization of support prior to immobilization of enzyme is highly important because of biomolecule-support interface on enzyme activity and stability. In this work, the effect of oxidation of nanobiochar, a carbonaceous material produced by biomass pyrolysis, using HCl, H₂SO₄, HNO₃ and their mixtures on immobilization of laccase has been studied. Scanning electron microscopy indicated that the structure of nanobiochars remained intact after oxidation and Fourier transform infrared spectroscopy confirmed the formation of carboxylic groups because of acid treatment. Titration measurements showed that the sample treated with H₂SO₄/HNO₃ (50:50, v/v) had the highest number of carboxylic groups (4.7mmol/g) and consequently the highest efficiency for laccase immobilization. Additionally, it was observed that the storage, pH and thermal stability of immobilized laccase on functionalized nanobiochar was improved compared to free laccase showing its potential for continuous applications. The reusability tests towards oxidation of 2, 2'-azino-bis (3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) showed that the immobilized laccase preserved 70% of the initial activity after 3cycles. Finally, using immobilized laccase for degradation of carbamazepine exhibited 83% and 86% removal in spiked water and secondary effluent, respectively.

Synthesis of spherical porous cross-linked glutaraldehyde/poly(vinyl alcohol) hydrogels

Spherical glutaraldehyde cross-linked poly(vinyl alcohol) (PVA) hydrogels (G-PVA) were prepared in three steps: gelatification, cross-linking, and removal of alginate. Gelatification was carried out by dropping a solution of alginate, PVA, and glutaraldehyde into a calcium chloride solution to form calcium alginate. Calcium alginate gels were prepared at 20°C, 40°C, 60°C, and 80°C to study the effect of gelatification temperature on the formation of pores on the surface of G-PVA. The effect of the alginate content was studied. PVA and glutaraldehyde were cross-linked by immersion of the gels in a solution of H2SO4 and Na2SO4. The effect of sodium alginate and inorganic salts, such as MgSO4 and K2SO4, on the formation of pores on the surface of G-PVA was confirmed.

Sandal reactive dyes decolorization and cytotoxicity reduction using manganese peroxidase immobilized onto polyvinyl alcohol-alginate beads

Background

Fungal manganese peroxidases (MnPs) have great potential as bio-remediating agents and can be used continuously in the immobilized form like many other enzymes.

Results

In the present study, purified manganese peroxidase (MnP) enzyme isolated from Ganoderma lucidum IBL-05 was immobilized onto polyvinyl alcohol-alginate beads and investigated its potential for the decolorization and detoxification of new class of reactive dyes and textile wastewater. The optimal conditions for MnP immobilization were 10 % (w/v) PVA, 1.5 % sodium alginate, 3 % boric acid and 2 % CaCl₂ solution. The optimum pH, temperature and kinetic parameters (K_m and V_max) for free and immobilized MnP were found to be significantly altered after immobilization. The immobilized MnP showed high decolorization efficiency for Sandal reactive dyes (78.14–92.29 %) and textile wastewater (61–80 %). Reusability studies showed that after six consecutive dye decolorization cycles, the PVA coupled MnP retained more than 60 % of its initial activity (64.9 % after 6th cycle form 92.29 % in 1st cycle) for Sandal-fix Foron Blue E₂BLN dye. The water quality assurance parameters (BOD, COD and TOC) and cytotoxicity (haemolytic and brine shrimp lethality tests) studies before and after treatment were employed and results revealed that both the dyes aqueous solution and textile wastewater were cytotoxic that reduced significantly after treatment.

Conclusions

The decolorization and cytotoxicity outcomes indicated that immobilized MnP in PVA–alginate beads can be efficiently exploited for industrial and environmental applications, especially for remediation of textile dyes containing wastewater effluents. Graphical abstract

Antibacterial silver nanoparticles in polyvinyl alcohol/sodium alginate blend produced by gamma irradiation

Polyvinyl alcohol/sodium alginate/nano silver (PVA/SA/Ag) composite films were made by solution casting method. Gamma irradiation was used to synthesize silver nanoparticles in situ via reduction of silver nitrate without using harmful chemical agents for biomedical applications. UV-vis and XRD results demonstrated that spherical silver nanoparticles were produced even at low irradiation dose of 5 kGy. By increasing irradiation dose, more nanoparticles were synthesized while no PVA hydrogel was formed up to 15 kGy. Also the size of nanoparticles was reduced with increasing gamma dose evidenced by higher release rate of silver nanoparticles in lukewarm water and SEM images. Comparing SEM images with DLS results indicated good performance of PVA/SA as an efficient stabilizer in preventing agglomeration of the silver nanoparticles. Good miscibility of polyvinyl alcohol and sodium alginate observed on the SEM images was supported with FTIR spectroscopy. Upon addition of sodium alginate to polyvinyl alcohol and increasing silver nanoparticles, the melting peak shifted to lower temperature and crystallinity percent was decreased. Addition of sodium alginate led to remarkable increase in rigidity of PVA. The composites exhibited strong antibacterial activity against Staphylococcus aureus and Escherichia coli even at very low level of silver nanoparticles.

Immobilization of a Plant Lipase from Pachira aquatica in Alginate and Alginate/PVA Beads

This study reports the immobilization of a new lipase isolated from oleaginous seeds of Pachira aquatica, using beads of calcium alginate (Alg) and poly(vinyl alcohol) (PVA). We evaluated the morphology, number of cycles of reuse, optimum temperature, and temperature stability of both immobilization methods compared to the free enzyme. The immobilized enzymes were more stable than the free enzyme, keeping 60% of the original activity after 4 h at 50°C. The immobilized lipase was reused several times, with activity decreasing to approximately 50% after 5 cycles. Both the free and immobilized enzymes were found to be optimally active between 30 and 40°C.

Kinetic Characterization and Effect of Immobilized Thermostable β-Glucosidase in Alginate Gel Beads on Sugarcane Juice

A thermostable β-glucosidase was effectively immobilized on alginate by the method of gel entrapment. After optimization of immobilized conditions, recovered enzyme activity was 60%. Optimum pH, temperature, kinetic parameters, thermal and pH stability, reusability, and storage stability were investigated. The K m and V max for immobilized β-glucosidase were estimated to be 5.0 mM and 0.64 U/ml, respectively. When comparing, free and immobilized enzyme, change was observed in optimum pH and temperature from 5.0 to 6.0 and 60°C to 80°C, respectively. Immobilized enzyme showed an increase in pH stability over the studied pH range (3.0-10.0) and stability at temperature up to 80°C. The storage stability and reusability of the immobilized β-glucosidase were improved significantly, with 12.09% activity retention at 30°C after being stored for 25 d and 17.85% residual activity after being repeatedly used for 4 times. The effect of both free and immobilized β-glucosidase enzyme on physicochemical properties of sugarcane juice was also analyzed.

High-affinity water-soluble system for efficient naringinase immobilization in polyvinyl alcohol-dimethyl sulfoxide lens-shaped particles

Polyvinyl alcohol (PVA) is a water-soluble, biocompatible and biodegradable synthetic polymer whose application in the immobilization of biological agents for use in biocatalysis has shown promising results. This study aimed to investigate and optimize the immobilization of naringinase from Penicillium decumbens in PVA networks, targeting for the hydrolysis of naringin. Variables such as the most suitable cross-linker, catalyst, inorganic salt, co-solvents and solidification process were identified as key issues for PVA-based methods to form lens-shaped particles, while retaining high enzyme activity and stability. Major improvements were established for better and more reproducible immobilization conditions, namely, by designing a new immobilization apparatus to produce uniform lens-shaped particles. The common problems of PVA-based entrapment were significantly mitigated, through the use of selected cross-linker, glutaraldehyde (GA), and co-solvent, dimethyl sulfoxide (DMSO), which decreased the toxicity of the immobilization process and allowed the control of membrane porosity, respectively. The relevance of DMSO and GA and their interaction and effect on the swelling ratio, encapsulation efficiency and residual activity of PVA biocatalysts were established. The immobilization of naringinase in PVA under a DMSO concentration of 60%, cross-linked with 1% GA, and particle lens size of 3.5-4.0 mm, width of 100-300 µm and average particle volume of 12.5 ± 0.92 µL, allowed an encapsulation efficiency of 98.6% and an average residual activity of 87% ± 3.6%. The kinetic characterization of the immobilized naringinase showed no changes in pH profile, whereas hydrolytic activity increased up to 60 °C. Immobilization in PVA/DMSO/GA lens-shaped particles enhanced the storage stability of naringinase. Moreover, these naringinase bio-immobilizates retained a conversion rate higher than 78% after 23 runs.

Production, partial characterization, and immobilization in alginate beads of an alkaline protease from a new thermophilic fungus Myceliophthora sp

Thermophilic fungi produce thermostable enzymes which have a number of applications, mainly in biotechnological processes. In this work, we describe the characterization of a protease produced in solidstate (SSF) and submerged (SmF) fermentations by a newly isolated thermophilic fungus identified as a putative new species in the genus Myceliophthora. Enzyme-production rate was evaluated for both fermentation processes, and in SSF, using a medium composed of a mixture of wheat bran and casein, the proteolytic output was 4.5-fold larger than that obtained in SmF. Additionally, the peak of proteolytic activity was obtained after 3 days for SSF whereas for SmF it was after 4 days. The crude enzyme obtained by both SSF and SmF displayed similar optimum temperature at 50 degrees C, but the optimum pH shifted from 7 (SmF) to 9(SSF). The alkaline protease produced through solid-state fermentation (SSF), was immobilized on beads of calcium alginate, allowing comparative analyses of free and immobilized proteases to be carried out. It was observed that both optimum temperature and thermal stability of the immobilized enzyme were higher than for the free enzyme. Moreover, the immobilized enzyme showed considerable stability for up to 7 reuses.