Make proper surfaces for immobilization of enzymes: Immobilization of lipase and α-amylase on modified Na-sepiolite

Applications and characterization of anti-browning enzymatically modified potato starch (EPS) film associated with chitosan (CTS)/L-Cys/citric acid (CA) on fresh-cut potato slices

This study explores the influence of incorporating L-cysteine (L-Cys), chitosan (CTS), and citric acid (CA) on the enzymatic modification of potato starch (EPS) films to enhance anti-browning properties. Four types of EPS composite films were evaluated for preserving fresh-cut potato slices at low temperatures to inhibit browning. Their thermal, physiochemical, mechanical, and digestibility properties were assessed. Results indicate that the addition of CTS, CA, and L-Cys improved the anti-browning activity of the EPS films by increasing film thickness and reducing water vapor permeability (WVP), oxygen transmission rate (OTR), ultraviolet (UV) transmittance, and tensile strength (TS). Furthermore, these additives improved the film's microstructure, resulting in reinforced intermolecular interactions, increased elongation at break, heightened crystallinity, enhanced thermal stability, and favorable gastrointestinal digestibility. Overall, EPS/CTS/L-Cys/CA composite films show promise as edible packaging materials with effective anti-browning properties.

Surfactant-mediated bio-manufacture: A unique strategy for promoting microbial biochemicals production

Biochemicals are widely used in the medicine and food industries and are more efficient and safer than synthetic chemicals. The amphipathic surfactants can interact with the microorganisms and embed the extracellular metabolites, which induce microbial metabolites secretion and biosynthesis, performing an attractive prospect of promoting the biochemical production. However, the commonness and differences of surfactant-mediated bio-manufacture in various fields are largely unexplored. Accordingly, this review comprehensively summarized the properties of surfactants, different application scenarios of surfactant-meditated bio-manufacture, and the mechanism of surfactants increasing metabolites production. Various biochemical productions such as pigments, amino acids, and alcohols could be enhanced using the cloud point and the micelles of surfactants. Besides, the amphiphilicity of surfactants also promoted the utilization of fermentation substrates, especially lignocellulose and waste sludge, by microorganisms, indirectly increasing the metabolites production. The increase in target metabolites production was attributed to the surfactants changing the permeability and composition of the cell membrane, hence improving the secretion ability of microorganisms. Moreover, surfactants could regulate the energy metabolism, the redox state and metabolic flow in microorganisms, which induced target metabolites synthesis. This review aimed to broaden the application fields of surfactants and provide novel insights into the production of microbial biochemicals.

Fabrication of immobilized lipases from Candida rugosa on hierarchical mesoporous silica for enzymatic enrichment of ω-3 polyunsaturated fatty acids by selective hydrolysis

In this study, lipase from Candida rugosa was immobilized on hydrophobic hierarchical porous hollow silica microsphere (HPHSM-C3) via adsorption. The prepared biocatalyst HPHSM-C3@CRL exhibited higher activity, thermal and pH stability. HPHSM-C3@CRL remained 70.2% of initial activity after 30 days of storage at 24 °C and 50.4% of initial activity after 10 cycles. Moreover, HPHSM-C3@CRL was utilized in enzymatic enrichment of omega-3 polyunsaturated fatty acids (ω-3 PUFAs) in glycerides, achieving ω-3 PUFAs content of 53.42% with the hydrolysis rate of 48.78% under optimal condition. The Km and Vmax value of HPHSM-C3@CRL was 42.2% lower and 63.5% higher than those of CRL, respectively. The 3D structure analysis of CRL, substrates and pore structure of HPHSM-C3 suggested that the hierarchical pore improved activity and selectivity of immobilized lipase. This result demonstrated that HPHSM-C3@CRL may be an effective biocatalyst for the enzymatic enrichment of ω-3 PUFAs in food industries.

Structure-based modification of a-amylase by conventional and emerging technologies: Comparative study on the secondary structure, activity, thermal stability and amylolysis efficiency

α-Amylase is an endo-enzyme that catalyzes the hydrolysis of starch into shorter oligosaccharides. α-Amylase plays a crucial role in various industries. Manipulated α-amylases are of particular interest due to their remarkable amylolysis efficiency and thermostability for large-scale biotechnological processes. The retained catalytic activity of enzymes is decreased according to extreme pH, temperature, pressure, and chemical reagents. Broad industrial applications of α-amylases need special properties such as stability against temperature, pH, and chelators, and also attain reusability, desirable enzymatic activity, efficiency, and selectivity. Considering the biotechnological importance of α-amylase, its high stability is the most critical challenge for its economic viability. Therefore, improving its functionality and stability recently gained much interest. To achieve this purpose, various emerging technologies in combination with conventional methods on α-Amylases with different sources have been conducted. The present review is an attempt to summarize the effect of various conventional methods and emerging technologies employed to date on α-amylase secondary structure, thermal stability, and performance.

Improved production of alkaline and solvent-stable proteases from a halotolerant Exiguobacterium isolate through heterologous expression

Halophiles are excellent sources of detergent proteases that are attributed to stability in alkaline pH, salts, surfactants, and hydrophobic solvents. The lower enzymatic yields and tedious downstream processes necessitate the search for newer halophilic sources. We have previously reported a halotolerant Exiguobacterium sp. TBG-PICH-001, which secretes solvent-tolerant alkaline protease/s. The present study describes the heterologous expression of two protease genes, namely, rsep metalloprotease (WP_195864791, 1.23 Kb) and tpa serine protease (WP_195864453, 0.879 Kb) genes. These were cloned into the pET 22b + plasmid vector and expressed in Escherichia coli BL21(DE3). The recombinant proteases rsep and tpa showed respective yields of 6.3 and 6.7 IU/mg, 11 and 12-fold higher than the crude native protease/s from TBG-PICH-001. These showed soluble expression at 46 and 32 KDa, respectively. These were purified to homogeneity through Ni-NTA-affinity chromatography. The purified proteases were characterized for properties like pH & temperature optima and stability, substrate specificity, kinetic parameters, and detergent attributes. They showed affinity towards various substrates with a respective Km of 392 and 301 μM towards casein. The recombinant proteases exhibited stability in the alkaline pH (7-10), surfactants, metal ions, detergents, and hydrophobic solvents, rendering their suitability as detergent additives.

A bifunctional core-shell gold@Prussian blue nanozyme enabling dual-readout microfluidic immunoassay of food allergic protein

Food allergy has posed a great threat for public health due to its rising prevalence worldwide, and thus sensitive and reliable food allergen monitoring methods is of great significance. In this study, we prepared a bifunctional core-shell gold@Prussian blue nanoparticles (Au@PBNP) nanozyme, which not only could serve as an alternative to natural peroxidase for colorimetric immunoassay, but also act as a unique Raman label in Raman-silent region (1800-2800 cm-1) for SERS analysis. By combining microfluidic device, smartphone, and portable Raman spectrometer, a new smartphone/SERS dual-readout microfluidic immunoassay platform was established for portable detection of food allergic protein (i.e., alpha-lactalbumin (α-LA)). The established method for detection of α-LA showed a LOD of 0.011 ng/mL in a liner range of 0.2-600 ng/mL. Furthermore, this method was also challenged in spiked food samples with good average recoveries, showing a great potential in practical applications.

Deglycation activity of the Escherichia coli glycolytic enzyme phosphoglucose isomerase

Glycation is a spontaneous chemical reaction, which affects the structure and function of proteins under normal physiological conditions. Therefore, organisms have evolved diverse mechanisms to combat glycation. In this study, we show that the Escherichia coli glycolytic enzyme phosphoglucose isomerase (Pgi) exhibits deglycation activity. We found that E. coli Pgi catalyzes the breakdown of glucose 6-phosphate (G6P)-derived Amadori products (APs) in chicken lysozyme. The affinity of Pgi to the glycated lysozyme (Km, 1.1 mM) was ten times lower than the affinity to its native substrate, fructose 6-phosphate (Km, 0.1 mM). However, the high kinetic constants of the enzyme with the glycated lysozyme (kcat, 396 s-1 and kcat/Km, 3.6 × 105 M-1 s-1) indicated that the Pgi amadoriase activity may have physiological implications. Indeed, when using total E. coli protein (20 mg/mL) as a substrate in the deglycation reaction, we observed a release of G6P from the bacterial protein at a Pgi specific activity of 33 μmol/min/mg. Further, we detected 11.4 % lower APs concentration in protein extracts from Pgi-proficient vs. deficient cells (p = 0.0006) under conditions where the G6P concentration in Pgi-proficient cells was four times higher than in Pgi-deficient cells (p = 0.0001). Altogether, these data point to physiological relevance of the Pgi deglycation activity.

Dynamic immobilization of bacterial cells on biofilm in a polyester nonwoven chemostat

Cell immobilization plays an important role in biocatalysis for high-value products. It is necessary to maintain the viability of immobilized cells for bioconversion using viable cells as biocatalysts. In this study, a novel polyester nonwoven chemostat was designed for cell immobilization to investigate biofilm formation and the dynamic balance between adsorption and desorption of cells on polyester nonwoven. The polyester nonwoven was suitable for cell immobilization, and the cell numbers on the polyester nonwoven can reach 6.5 ± 0.38 log CFU/mL. After adding the polyester nonwoven to the chemostat, the fluctuation phenomenon of free bacterial cells occurred. The reason for this phenomenon was the balance between adsorption and desorption of bacterial cells on the polyester nonwoven. Bacterial cells could adhere to the surface of polyester nonwoven via secreting extracellular polymeric substances (EPS) to form biofilms. As the maturation of biofilms, some dead cells inside the biofilms can cause the detachment of biofilms. This process of continuous adsorption and desorption of cells can ensure that the polyester nonwoven chemostat has lasting biological activity.

Preparation of water-insoluble lignin nanoparticles by deep eutectic solvent and its application as a versatile and biocompatible support for the immobilization of α-amylase

As one of the most abundant biopolymers, lignin is a widely available resource. However, its potential largely remains untapped, with most of it ending up as waste from industries like paper production, pulp processing, and bio-refining. The research undertaken in this study focused on the extraction of lignin from agroforestry waste using a deep eutectic solvent (DES) as a carrier for α-amylase immobilization, resulting in high stability and reusability. Several techniques, including Nuclear Magnetic Resonance (NMR), Scanning Electron Microscopy (SEM), Energy-Dispersive X-ray Spectroscopy (EDS), and the Brunauer-Emmett-Teller (BET) method were employed to examine the structure and morphology of both the extracted lignin and the immobilized enzyme. The temperature used to recover lignin by DES would affect immobilization efficiency and enzyme loading by influencing its specific surface area, pore size, and volume distribution. Investigations using Nuclear Overhauser Effect Spectroscopy (NOESY) uncovered that the hydroxyl groups in G, H, and S units and the β-O-4 structure of lignin primarily serve as binding sites for enzyme molecules. Immobilized α-amylase demonstrated a higher pH and thermal stability level, with an optimal pH of 7.0 and temperature of 100 °C, compared to the free enzyme, which exhibited optimal activity at a pH of 6.5 and temperature of 90 °C. Importantly, immobilized α-amylase retained >80 % of its initial activity even after 28 days at room temperature, and it maintained 70 % of its activity after being reused 12 times. These findings strongly suggest that lignin derived from agroforestry residues holds promising potential as a future versatile immobilization material, a prospect integral to society's sustainable development.

Trends in the Use of Lipases: A Systematic Review and Bibliometric Analysis

Scientific mapping using bibliometric data network analysis was applied to analyze research works related to lipases and their industrial applications, evaluating the current state of research, challenges, and opportunities in the use of these biocatalysts, based on the evaluation of a large number of publications on the topic, allowing a comprehensive systematic data analysis, which had not yet been conducted in relation to studies specifically covering lipases and their industrial applications. Thus, studies involving lipase enzymes published from 2018 to 2022 were accessed from the Web of Science database. The extracted records result in the analysis of terms of bibliographic compatibility among the articles, co-occurrence of keywords, and co-citation of journals using the VOSviewer algorithm in the construction of bibliometric maps. This systematic review analysis of 357 documents, including original and review articles, revealed studies inspired by lipase enzymes in the research period, showing that the development of research, together with different areas of knowledge, presents good results related to the applications of lipases, due to information synchronization. Furthermore, this review showed the main challenges in lipase applications regarding increased production and operational stability; establishing well-defined evaluation criteria, such as cultivation conditions, activity, biocatalyst stability, type of support and reactor; thermodynamic studies; reuse cycles; and it can assist in defining goals for the development of successful large-scale applications, showing several points for improvement of future studies on lipase enzymes.

Regioselective syntheses of 2-oxopyridine carbonitrile derivatives and evaluation for antihyperglycemic and antioxidant potential

A library of 2-oxopyridine carbonitriles 1-34 was synthesized by regioselective nucleophilic substitution reactions. In the first step, a one-pot multicomponent reaction yield pyridone intermediates. The resulting pyridone intermediates were then reacted with phenacyl halides in DMF and stirred at 100 °C for an hour to afford the desired compounds in good yields. Structures of synthetic molecules were characterized by EI-MS, HREI-MS, ¹H NMR, and ¹³C NMR, and all thirty-four (34) compounds were found to be new. All synthetic compounds were examined for antidiabetic and antioxidant potential. The compounds exhibited α-glucosidase inhibitory potential in the range of IC₅₀ = 3.00 ± 0.11-43.35 ± 0.67 μM and α-amylase inhibition potential in the range of IC₅₀ = 9.20 ± 0.14-65.56 ± 1.05 μM. Among the tested compounds, 1 showed the most significant α-glucosidase inhibitory activity, with an IC₅₀ value of 3.00 ± 0.11 μM, while the most active compound against α-amylase was 6, with an IC₅₀ value = 9.20 ± 0.14 μM. The kinetic studies and analysis indicated that the compounds followed the competitive mode of inhibition. In addition, the molecular docking studies showed the interaction profile of all molecules with the binding site residues of α-glucosidase and α-amylase enzymes.

Carboxylic acid reductases: Structure, catalytic requirements, and applications in biotechnology

Biocatalysts have been gaining extra attention in recent decades due to their industrial-relevance properties, which may hasten the transition to a cleaner environment. Carboxylic acid reductases (CARs) are large, multi-domain proteins that can catalyze the reduction of carboxylic acids to corresponding aldehydes, with the presence of adenosine triphosphate (ATP) and nicotinamide adenine dinucleotide phosphate (NADPH). This biocatalytic reaction is of great interest due to the abundance of carboxylic acids in nature and the ability of CAR to convert carboxylic acids to a wide range of aldehydes essentially needed as end products such as vanillin or reaction intermediates for several compounds production such as alcohols, alkanes, and amines. This modular enzyme, found in bacteria and fungi, demands an activation via post-translational modification by the phosphopantetheinyl transferase (PPTase). Recent advances in the characterization and structural studies of CARs revealed valuable information about the enzymes' dynamics, mechanisms, and unique features. In this comprehensive review, we summarize the previous findings on the phylogeny, structural and mechanistic insight of the domains, post-translational modification requirement, strategies for the cofactors regeneration, the extensively broad aldehyde-related industrial application properties of CARs, as well as their recent immobilization approaches.

Allergenicity reduction of cow milk treated by alkaline protease combined with Lactobacillus Plantarum and Lactobacillus helveticus based on epitopes

This paper has investigated the residual allergenicity of cow's milk treated by enzymatic hydrolysis combined with Lactobacillus fermentation (Lb. Plantarum and Lb. helveticus). The treated products were comprehensively evaluated by SDS-PAGE, RP-HPLC, ELISA, and Caco-2 models. And the allergenic changes of residual allergenic peptides were explored by DC-T co-culture. The results showed that alkaline protease was the most suitable protease that targeted to destroy epitopes of milk major allergen than trypsin, pepsin, and papain by prediction. And the residual epitopes were reduced to four which was treated by alkaline protease combined with Lb. helveticus. The transport absorption capacity of treated products was almost twice than milk. Meanwhile, the seven residual allergenic peptides were obtained from treated products. Among them, αs₁-casein (AA84-90) can be used as an immune tolerance peptide for further study. Lb. helveticus combined with alkaline protease treatment may be considered promising strategy of protect from cow's milk allergy.

Recent advances in simultaneous thermostability-activity improvement of industrial enzymes through structure modification

Engineered thermostable microbial enzymes are widely employed to catalyze chemical reactions in numerous industrial sectors. Although high thermostability is a prerequisite of industrial applications, enzyme activity is usually sacrificed during thermostability improvement. Therefore, it is vital to select the common and compatible strategies between thermostability and activity improvement to reduce mutants̕ libraries and screening time. Three functional protein engineering approaches, including directed evolution, rational design, and semi-rational design, are employed to manipulate protein structure on a genetic basis. From a structural standpoint, integrative strategies such as increasing substrate affinity; introducing electrostatic interaction; removing steric hindrance; increasing flexibility of the active site; N- and C-terminal engineering; and increasing intramolecular and intermolecular hydrophobic interactions are well-known to improve simultaneous activity and thermostability. The current review aims to analyze relevant strategies to improve thermostability and activity simultaneously to circumvent the thermostability and activity trade-off of industrial enzymes.

Solvent tolerant enzymes in extremophiles: Adaptations and applications

Non-aqueous enzymology has always drawn attention due to the wide range of unique possibilities in biocatalysis. In general, the enzymes do not or insignificantly catalyze substrate in the presence of solvents. This is due to the interfering interactions of the solvents between enzyme and water molecules at the interface. Therefore, information about solvent-stable enzymes is scarce. Yet, solvent-stable enzymes prove quite valuable in the present day biotechnology. The enzymatic hydrolysis of the substrates in solvents synthesizes commercially valuable products, such as peptides, esters, and other transesterification products. Extremophiles, the most valuable yet not extensively explored candidates, can be an excellent source to investigate this avenue. Due to inherent structural attributes, many extremozymes can catalyze and maintain stability in organic solvents. In the present review, we aim to consolidate information about the solvent-stable enzymes from various extremophilic microorganisms. Further, it would be interesting to learn about the mechanism adapted by these microorganisms to sustain solvent stress. Various approaches to protein engineering are used to enhance catalytic flexibility and stability and broaden biocatalysis's prospects under non-aqueous conditions. It also describes strategies to achieve optimal immobilization with minimum inhibition of the catalysis. The proposed review would significantly aid our understanding of non-aqueous enzymology.

Kinetic and thermodynamic studies of novel acid phosphatase isolated and purified from Carthamus oxyacantha seedlings

Acid phosphatase (ACP) is a key enzyme in the regulation of phosphate feeding in plants. In this study, a new ACP from C. oxyacantha was isolated to homogeneity and biochemically described for the first time. Specific activity (283 nkat/mg) was found after 2573 times purification fold and (17 %) yield. Using SDS-PAGE under denaturing and nondenaturing conditions, ACP was isolated as a monomer with a molecular weight of 36 kDa. LC-MS/MS confirmed the presence of this band, suggesting that C. oxycantha ACP is a monomer. The enzyme could also hydrolyze orthophosphate monoester with an optimal pH of 5.0 and a temperature of 50 °C. Thermodynamic parameters were also determined (Ea, ΔH°, ΔG°, and ΔS°). ACP activity was further studied in the presence of cysteine, DTT, SDS, EDTA, β-ME, Triton-X-100 H₂O₂, and PMSF. The enzyme had a K_m of 0.167 mM and an Ea of 9 kcal/mol for p-nitrophenyl phosphate. The biochemical properties of the C. oxyacantha enzyme distinguish it from other plant acid phosphatases and give a basic understanding of ACP in C. oxyacantha. The results of this investigation also advance our knowledge about the biochemical significance of ACP in C. oxyacantha. Thermal stability over a wide pH and temperature range make it more suitable for use in harsh industrial environments. However, further structural and physiological studies are anticipated to completely comprehend its important aspects in oxyacantha species.

Enzyme immobilization on biomass-derived carbon materials as a sustainable approach towards environmental applications

Enzymes with their environment-friendly nature and versatility have become highly important 'green tools' with a wide range of applications. Enzyme immobilization has further increased the utility and efficiency of these enzymes by improving their stability, reusability, and recyclability. Biomass-derived matrices when used for enzyme immobilization offer a sustainable solution to environmental pollution and fuel depletion at low costs. Biochar and other biomass-derived carbon materials obtained are suitable for the immobilization of enzymes through different immobilization strategies. Environmental pollution has become an utmost topic of research interest due to an ever-increasing trend being observed in anthropogenic activities. This has widely contributed to the release of various toxic effluents into the environment in their native or metabolized forms. Therefore, more focus is being directed toward the utilization of immobilized enzymes in the bioremediation of water and soil, biofuel production, and other environmental applications. In this review, up-to-date literature concerning the immobilization and potential uses of enzymes immobilized on biomass-derived carbon materials has been presented.

The antioxidant activities, inhibitory effects, kinetics, and mechanisms of artocarpin and α-mangostin on α-glucosidase and α-amylase

This study investigated the antioxidant activities, enzyme inhibitory activities and the interaction mechanisms of artocarpin and α-mangostin on α-amylase and α-glucosidase. Results showed that artocarpin and α-mangostin had obvious antioxidant activities and inhibitory activities on α-glucosidase and α-amylase. The inhibitions of the two compounds on α-glucosidase were reversible and non-competitive according to the kinetics studies. Fluorescence intensity measurements indicated that the interaction mechanisms between the inhibitors and the two enzymes were static processes. Isothermal titration calorimetry (ITC) analysis showed that the bindings between the inhibitors and the enzymes complex were all spontaneous. The main driving forces between α-mangostin and artocarpin with α-glucosidase might be hydrogen bonds and electrostatic interactions, respectively. While the forces between the two inhibitors and α-amylase might be hydrophobic interactions. Furthermore, molecular docking results showed that artocarpin and α-mangostin could bind to the allosteric site of the two enzymes, except for artocarpin in the active site pocket of α-amylase. All the results indicated that artocarpin and α-mangostin might be promising candidates for hypoglycemic functional products.

Green synthesis of polydopamine functionalized magnetic mesoporous biochar for lipase immobilization and its application in interesterification for novel structured lipids production

In this study, the polydopamine functionalized magnetic mesoporous biochar (MPCB-DA) was prepared for immobilization of Bacillus licheniformis lipase via covalent immobilization. Under optimized immobilization conditions, the maximum immobilization yield, efficiency and immobilized lipase amount were found to be 45%, 54% and 36.9 mg/g, respectively. The immobilized lipase, MPCB-DA-Lipase showed good thermal stability and alkali resistance. The MPCB-DA-Lipase retained 56% initial activity after 10 reuse cycles, with more than 85% relative activity after 70 days' storage at 4 or 25 °C. The MPCB-DA-Lipase was efficiently applied in the interesterification of Cinnamomum camphora seed kernel oil and perilla seed oil, with maximum interesterification efficiency of 46%. The produced structured lipids belong to the S₂U and U₂S triacylglycerols, a novel medium-and long-chain triacylglycerol. These results demonstrated that the MPCB-DA-Lipase may be used as an efficient biocatalyst in lipid processing applications of food industries.

Presenting B-DNA as macromolecular crowding agent to improve efficacy of cytochrome c under various stresses

Existence of numerous biomolecules results in biological fluids to be extremely crowded. Thus, Macromolecular crowding is an essential phenomenon to sustain active conformation of proteins in biological systems. Herein, double helical deoxyribonucleic acid (B-DNA) is presented for the first time as a biomacromolecular crowding system for sustainable packaging of cytochrome c (Cyt C). The peroxidase activity of Cyt C was investigated in the presence of various concentrations of B-DNA (from salmon milt). At an optimized concentration of 0.125 mg/mL B-DNA, an 11-fold higher catalytic activity was found than in native Cyt C with improved stability. Molecular docking and spectroscopic analyses revealed that electrostatic and H-bonding are the main interactions between DNA and Cyt C that affect the structural stability and activity of the protein. Moreover, the catalytic activity and stability of the protein were further investigated in the presence of severe process conditions by UV-visible, circular dichroism, and Fourier-transform infrared spectroscopies. Molecularly crowded Cyt C showed significantly higher activity and stability under severe environments such as high temperature (110 °C), oxidative stress, high pH (pH 10) and biological (trypsin) and chemical denaturants (urea) compared to bare Cyt C. The observed results support the suitability of DNA-based macromolecular crowding media as a viable and effective stabilizer of proteins against multiple stresses.

A designed experiment for CdS-AgBr photocatalyst toward methylene blue

A boosted photocatalytic activity was observed for the CdS-AgBr nanocomposite in the degradation of methylene blue (MB). The experimental design method based on the response surface methodology (RSM) approach used to study the simultaneous interaction effects between the influencing variables. Analysis of variance (ANOVA) of the results confirmed a significant model for processing the data because an F value of 32.34 for the suggested model was higher than that of the critical value of F_{0.05, 14, 13} = 2.55 at 95% confidence interval. This analysis also showed a non-significant lack of fit (LOF) (as a measure of the randomness of the deviations around the obtained data) because the LOF F value of 8.27 was smaller than that of the critical value of F_{0.05, 10, 3} = 8.79. R² values near to unity were achieved (the multiple correlation coefficients R² (R² = 0.9627), adjusted R² (adj-R² = 0.9226), and predicted R² (pred-R² = 0.7423)). Six center points suggested by the model included the following conditions: pH, 6.1; C_MB, 3.5 mg/L; a dose of the catalyst, 0.68 g/L; and irradiation time, 40.5 min. During the center point runs, the degradation efficiencies were obtained in the range of 38 to 43%. The optimal run included pH, 9; catalyst dosage, 1 g/L; irradiation time, 60 min; and C_MB, 2 mg/L, and the best removal efficiency of 98% was achieved during these conditions.

Effect of polyol osmolytes on the structure-function integrity and aggregation propensity of catalase: A comprehensive study based on spectroscopic and molecular dynamic simulation measurements

Owing to the ability of catalase to function under oxidative stress vis-à-vis its industrial importance, the structure-function integrity of the enzyme is of prime concern. In the present study, polyols (glycerol, sorbitol, sucrose, xylitol), were evaluated for their ability to modulate structure, activity and aggregation of catalase using in vitro and in silico approaches. All polyols increased catalase activity by decreasing K_m and increasing V_max resulting in enhanced catalytic efficiency (k_cat/K_m) of the enzyme, with glycerol being the most efficient with a k_cat/K_m increase from 4.38 × 10⁴ mM^-1 S^-1 (control) to 5.8 × 10⁵ mM^-1 S^-1. Correlatively with this, enhanced secondary structure with reduced hydrophobic exposure was observed in all polyols. Furthermore, increased stability, with an increase in melting temperature by 15.2 °C, and almost no aggregation was observed in glycerol. Overall, ability to regulate structure-function integrity and aggregation propensity was highest for glycerol and lowest for xylitol. Simulation studies were performed involving structural dynamics measurements, principal component analysis and free energy landscape analysis. Altogether, all polyols were stabilizing in nature and glycerol, in particular, has potential to efficiently prevent not only the antioxidant defense system but also might serve as a stability aid during industrial processing of catalase.

Efficient hydrolysis of starch by α-amylase immobilized on cloisite 30B and modified forms of cloisite 30B by adsorption and covalent methods

In this paper, α-amylase from Bacillus subtilis was successfully immobilized on three supports. First, α-amylase was immobilized on cloisite 30B via the adsorption method. Then cloisite 30B was activated with tosyl chloride and epichlorohydrin. These activated supports were used for covalent immobilization of α-amylase, and their enzymatic activities were effectively tested in the starch hydrolysis. The results demonstrated that the specific activity of α-amylase immobilized on cloisite 30B was 2.39 ± 0.03, for α-amylase immobilized on activated cloisite 30B with epichlorohydrin was 1.96 ± 0.05 and for α-amylase immobilized on activated cloisite 30B with tosyl chloride was 2.17 ± 0.05 U mg^-1. The optimum pH for the activity of free α-amylase was 7, but for α-amylase immobilized on cloisite 30B was 8, and for α-amylase immobilized on activated supports was 7.5. The immobilized enzymes had better thermal resistance and storage stability than free α-amylase, and they also showed excellent reusability.

Immobilization of α-amylase in ethylcellulose electrospun fibers using emulsion-electrospinning method

α-Amylase encapsulated in water in oil (W/O) emulsion was prepared using poly ethylene glycol (PEG 10000) (2%w/v) as water phase and ethylcellulose (EC) in ethyl acetate as oil phase at the ratio of 10:90 v/v. Next, the electrospun fibers were prepared by mixing enzyme loaded emulsion with EC solution (20%w/v) in acetic acid/ethyl acetate (20:80 v/v) at the 2:1 ratio. The emulsion showed good physical stability. The immobilized enzyme showed high activity across a board range of pHs and temperatures. The storage stability of the immobilized enzyme was 2 fold of free enzyme activity after 45 days. The residual activity of immobilized α-amylase onto of fibers after 10 and 15 repeated cycles, was approximately 100% and 50%, respectively. The results of this study indicated that the α-amylase loaded EC fibers have acceptable activity against harsh conditions and excellent reusability.

An effective immobilization of β-glucosidases by partly cross-linking enzyme aggregates

Enzyme immobilization provides ideal operating conditions for enzymes stabilization and sustainable recycling. In this work, as a kind of clay material, montmorillonite (MTL) was chosen for immobilizing the β-glucosidase extracted from Agrocybe aegirit. The immobilized β-glucosidase via partly cross-linking enzyme aggregates (pCLEAs) formed by self-catalysis provided biocatalysts with satisfactory thermal and pH stability. Compared to the glutaraldehyde cross-linked, the immobilized β-glucosidase (β-G-pCLEAs@MTL) exhibited significantly higher immobilization efficiency (IE) and immobilization yield (IY), which were 80.6% and 76.9%, respectively. The β-G-pCLEAs@MTL also showed better stability and preferable reusability. And the activity of the β-G-pCLEAs@MTL remained 85.0% after 5 cycles and 74.7% after 10 cycles. Therefore, the method based on the pre- crosslinking to form pCLEAs and after-immobilization can effectively improve IY and IE. In addition, MTL seems to be a good alternative carrier to immobilize other enzymes for industrial application.

Effect of Different TiO2 Morphologies on the Activity of Immobilized Lipase for Biodiesel Production

Lipase catalytic activity is greatly influenced by immobilization on nanoparticles. In this study, lipase from Aspergillus niger was immobilized on TiO₂ nanoparticles with different morphologies: microspheres, nanotubes, and nanosheets. All TiO₂ samples were prepared by a hydrothermal method. Lipase/TiO₂ nanocomposites were prepared by a physical adsorption method through hydrophobic interactions. The prepared composites were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), and high-resolution transmission electron microscopy (HRTEM). The catalytic activity of free and immobilized lipases was tested using sunflower oil in the presence of methanol to produce biodiesel at 40 °C for 90 min. The lipase immobilized on TiO₂ microspheres showed the highest activity compared to the lipase immobilized on TiO₂ nanotubes and nanosheets. To optimize the lipase-to-microsphere ratio, lipase was immobilized on TiO₂ microspheres in different microspheres/lipase, w/w, (S/L) ratios of 1:1, 1:0.75, 1:0.5, and 1:0.25. It was noticed that the hydrolytic activity follows the order 1:0.25 > 1:0.5 > 1:75 > 1:1. The immobilization yield activities were found to be 113, 123, 125, and 130% for the microspheres/lipase (S/L) ratios of 1:1, 1:0.75, 1:0.5, and 1:0.25, respectively.

Highly effective enzymes immobilization on ceramics: Requirements for supports and enzymes

Enzyme immobilization is a well-known method for the improvement of enzyme reusability and stability. To achieve very high effectiveness of the enzyme immobilization, not only does the method of attachment need to be optimized, but the appropriate support must be chosen. The essential necessities addressed to the support applied for enzyme immobilization can be focused on the material features as well as on the stability and resistances in certain conditions. Ceramic membranes and nanoparticles are the most widespread supports for enzyme immobilization. Hence, the immobilization of enzymes on ceramic membrane and nanoparticles are summarized and discussed. The important properties of the supports are particle size, pore structure, active surface area, volume to surface ratio, type and number of reactive available groups, as well as thermal, mechanical, and chemical stability. The modifiers and the crosslinkers are crucial to the enzyme loading amount, the chemical and physical stability, and the reusability and catalytical activity of the immobilized enzymes. Therefore, the chemical and physical methods of modification of ceramic materials are presented. The most popular and used modifiers (e.g. APTES, CPTES, VTES) as well as activating agents (GA, gelatin, EDC and/or NHS) applied to the grafting process are discussed. Moreover, functional groups of enzymes are presented and discussed since they play important roles in the enzyme immobilization via covalent bonding. The enhanced physical, chemical, and catalytical properties of immobilized enzymes are discussed revealing the positive balance between the effectiveness of the immobilization process, preservation of high enzyme activity, its good stability, and relatively low cost.

Enhancing thermostabilization of a newly discovered α-amylase from Bacillus cereus GL96 by combining computer-aided directed evolution and site-directed mutagenesis

This study has described the characterization of a new a-amylase from the recently isolated Bacillus cereus GL96. Subsequently, an in-silico approach was taken into account to redesign the enzyme to meet higher thermal stability. Finally, the engineered enzyme was constructed experimentally using side-directed mutagenesis (SDM) and characterized accordingly. The enzyme was stable over pH 4-11, with the highest activity at 9.5. The temperature profile of the wild-type enzyme showed optimum activity at 50 °C plus 40% of stability at temperatures up to 70 °C. The in-silico result was indicated D162W, D162R, and D162K as the three stabilizing mutations. Among them, D162K showed better results, especially in the molecular dynamics simulation, and therefore, it was constructed by SDM. This variant was shown 5 °C higher optimum temperature (55 °C) with increasing activity than the native enzyme. In addition, it was significantly more stable than the native form. For example, while the latter almost wholly lost its function at a temperature above 70 °C, the D162K can retain more than 40% of its initial activity up to 80 °C. Considering the promising properties that the mutant enzyme showed, it can be considered for further investigation to meet the industrial requirement completely.

A SiO2 Microcarrier with an Opal-like Structure for Cross-Linked Enzyme Immobilization

The opal-like SiO₂ microcarriers with different pore diameters named opal-SiO₂I and opal-SiO₂II were synthesized and utilized as microcarriers to immobilize Rhizopus oryzae lipase (ROL) and Aspergillus oryzae α-amylases (AOA). ROL and AOA can be more stably immobilized on the cross-linked SiO₂ opals by neopentyl glycol diglycidyl ether (NGDE), which is the first attempt to use it as a cross-linking agent compared with glutaraldehyde. According to the morphology analysis, multiple layers of SiO₂ monodisperse microspheres were regularly packed and formed an opal-like structure, and enzymes were well scattered and immobilized throughout the SiO₂ opals. The results showed that the performance of enzymes immobilized on opal-SiO₂II with a larger specific surface area was much better than that of opal-SiO₂I. The enzyme activity of ROL@opal-SiO₂II and AOA@opal-SiO₂II cross-linked with 1% NGDE increased 5.32 and 9.32 times compared with their free counterpart, respectively. Furthermore, pH and thermal stability and reusability of ROL/AOA@opal-SiO₂II were significantly improved and higher than those of ROL/AOA@opal-SiO₂I and free enzymes. This study provides an easily obtained microcarrier opal-SiO₂II, which shows potential for efficient different enzyme immobilizations and further industrial applications.

Valorization and optimization of agro-industrial orange waste for the production of enzyme by halophilic Streptomyces sp

This study underlines the biotechnical valorization of the accumulated and unusable remains of agro-industrial orange fruit peel waste to produce α-amylase under submerged conditions by Streptomyces sp. KP314280 (20r). The response surface methodology based on central composite design (RSM-CCD) and artificial neural network coupled with a genetic algorithm (ANN-GA) were used to model and optimize the conditions for the α-amylase production. Four independent variables were evaluated for α-amylase activity including substrate concentration, inoculum size, sodium chloride powder (NaCl), and pH. A ten-fold cross-validation indicated that the ANN has a greater ability than the RSM to predict the α-amylase activity (R²_ANN = 0.884 and R²_RSM = 0.725). The analysis of variance indicated that the aforementioned four factors significantly affected the α-amylase activity. Additionally, the α-amylase production experiments were conducted according to the optimal conditions generated by the GA. The results indicated that the amylase yield increased by 4-fold. Moreover, the α-amylase production (12.19 U/mL) in the optimized medium was compatible with the predicted conditions outlined by the ANN-GA model (12.62 U/mL). As such, the ANN and GA combination is optimizable for α-amylase production and exhibits an accurate prediction which provides an alternative to other biological applications.

The photocatalytic rate of ZnO supported onto natural zeolite nanoparticles in the photodegradation of an aromatic amine

Aniline and its derivate are critical environmental pollutants, and thus, the introduction of an eco-friendly catalyst for removing them is an important research future. The ZnO supported on the ball-mill prepared clinoptilolite nanoparticles (CNPs) was prepared via an ion-exchange process followed by the calcination process. The amount of loaded ZnO in the ZnO-CNP (CZ) samples varied as 0.54, 0.63, 0.72, and 0.86 meq/g as the Zn(II) concentration in the ion-exchange solution varied from 0.1 to 0.5 M. The ZnO-CNP catalyst was briefly characterized by XRD, FTIR, and DRS techniques. The pHpzc value for the various ZnO-CNPs was about 7.1 that had no change with the ZnO loading. By applying the Scherrer equation on the XRD results, a nano-dimension of about 50 nm was obtained for the catalyst. Bandgap energy of the ZnO-CNP samples was estimated by applying the Kubelka-Munk equation on the DRS reflectance spectra. The value for the CZ2 catalyst was about 3.64 eV. The supported ZnO-CNP sample was then used in the photodegradation of 2,4-dichloroaniline (DCA). Raw zeolite showed a relatively low photocatalytic activity. The degradation efficiency was followed by recording the absorbance of the DCA solution by UV-Vis spectrophotometer. The effects of the essential critical operating factors on the degradation efficiency were kinetically studied by applying the Hinshelwood equation to the results. The ZnO-CNP catalyst with 2 w% ZnO showed the best photocatalytic rate in the optimal conditions of 0.75 g/L, C_DCA: 15 ppm, and the initial pH: 5.8. Finally, HPLC analysis of the blank and the photodegraded DCA solutions at 180 and 300 min confirmed 74 and 87% of DCA molecules were degraded during these times. The results confirm that supported ZnO onto clinoptilolite caused enhanced photocatalytic activity because the zeolite internal electrical field prevents the e^-/h⁺ recombination.

Process optimization of polyphenol oxidase immobilization: Isotherm, kinetic, thermodynamic and removal of phenolic compounds

Chitosan/montmorillonite (CTS/MMT) and chitosan‑gold nanoparticles/montmorillonite (CTS-Au/MMT) composites were prepared, characterized through Fourier transformed infrared (FT-IR), X-ray powder diffraction (XRD), and scanning electron microscopy (SEM), and utilized as support for immobilization of polyphenol oxidase (PPO). PPO was immobilized on CTS/MMT (IPPO) and CTS-Au/MMT (IPPO-Au) by physical adsorption, respectively. In order to achieve simultaneous maximization of immobilization efficiency and enzyme activity, the immobilization process parameters were optimized by Taguchi-Grey relational analysis (TGRA) approach. Under the optimal immobilization condition, the immobilization efficiency and enzyme activity reached at 50.16% and 1.46 × 10⁴ U/mg for IPPO, and 63.35% and 3.01 × 10⁴ U/mg for IPPO-Au, respectively. The isotherm, kinetic and thermodynamics of PPO adsorption were investigated in detail. The adsorption process was better explained by Toth isotherm and Fractal-like pseudo second order model, respectively. Intra-particle diffusion and film diffusion were involved in the adsorption process and intra-particle diffusion was not the only rate-controlling step. The adsorption of PPO was exothermic, physical and spontaneous at the investigated temperature range. The immobilized PPO were used to oxidize phenolic compounds. All investigated phenolic compounds showed the higher conversion as catalyzed by IPPO-Au. For both IPPO and IPPO-Au, the conversion of substituted phenols was higher than that of phenol.

Chemical and physical Chitosan modification for designing enzymatic industrial biocatalysts: How to choose the best strategy?

Chitosan is one of the most abundant natural polymer worldwide, and due to its inherent characteristics, its use in industrial processes has been extensively explored. Because it is biodegradable, biocompatible, non-toxic, hydrophilic, cheap, and has good physical-chemical stability, it is seen as an excellent alternative for the replacement of synthetic materials in the search for more sustainable production methodologies. Thus being, a possible biotechnological application of Chitosan is as a direct support for enzyme immobilization. However, its applicability is quite specific, and to overcome this issue, alternative pretreatments are required, such as chemical and physical modifications to its structure, enabling its use in a wider array of applications. This review aims to present the topic in detail, by exploring and discussing methods of employment of Chitosan in enzymatic immobilization processes with various enzymes, presenting its advantages and disadvantages, as well as listing possible chemical modifications and combinations with other compounds for formulating an ideal support for this purpose. First, we will present Chitosan emphasizing its characteristics that allow its use as enzyme support. Furthermore, we will discuss possible physicochemical modifications that can be made to Chitosan, mentioning the improvements obtained in each process. These discussions will enable a comprehensive comparison between, and an informed choice of, the best technologies concerning enzyme immobilization and the application conditions of the biocatalyst.

Supported cuprous oxide-clinoptilolite nanoparticles: Brief identification and the catalytic kinetics in the photodegradation of dichloroaniline

The supported CuO onto the ball-mill prepared clinoptilolite nanoparticles (CNPs) was prepared via an ion exchange process in Cu(II) aqueous solution followed by the calcination process. The CuO-CNP samples with various CuO loading were briefly characterized by XRD, FTIR, and DRS. pHpzc was varied in the range of 6.3 to 6.8 depending on the amount of loaded CuO in the samples. The band gap energy was estimated by applying the Kubelka-Munk equation on the DRS results that varied from 2.41 to 2.50 eV depending on the CuO loading. Based on the Scherrer equation nano-sized CuO-CNP at about 50 nm was estimated. The CuO-CNP contained 3.9% CuO showed the highest photocatalytic activity toward dichloroaniline (DCA). The effects of the experimental variables on DCA photodegradation were studied by using the Hinshelwood model. The optimal conditions for obtaining a higher rate for DCA photodegradation were the catalyst dose of 0.5 g/L, C_DCA: 5 ppm, and the initial pH: 3. HPLC analysis of the photodegraded DCA solutions for 180 and 300 min gave the degradation extents 71% and 90%, respectively.

Photocatalytic kinetics of 2,4-dichloroaniline degradation by NiO-clinoptilolite nanoparticles

The ball-mill clinoptilolite nanoparticles (CNP) was ion-exchanged in Ni(II) solutions and calcined to obtain NiO-CNP catalysts with various NiO loadings. The resultant CNP was ion-exchanged in 0.1, 0.2, 0.3, and 0.4 M Ni(II) solutions and then calcined at 450 °C. The resultant NiO-CNPs contained 1.9, 2.3, 3.0, and 3.2% NiO, respectively. The XRD, FTIR, and DRS characterization techniques were applied. By applying the Scherrer equation on the XRD results, the average crystallite size for the NiO-CNP samples was estimated in the range of 42-65 nm. The pHpzc of the NiO-CNP species was slightly changed from 6.8 to 7.6 by an increase in the loaded NiO. The band gap energy of the samples was calculated by applying the Kubelka-Munk equation on the DRS results. The band gap energies of 3.81, 4.05, and 3.63 eV were estimated for the direct electronic transitions of the CN2, CN2.3, and CN3.2 samples, respectively. The boosted photoactivity was obtained in 2,4-dichloroanilyne (DCA) degradation when NiO supported onto both micronized clinoptilolite and its nanoparticles. The effects of the most important experimental variables on DCA photodegradation rate were kinetically studied by applying the Hinshelwood model on the results. The faster rate for the DCA photodegradation was achieved at the optimal conditions, including the catalyst dose: 0.5 g/L, C_DCA: 5 ppm, and the initial pH: 3. Some new peaks were observed in the HPLC chromatograms for the photodegraded DCA solutions after 180 min and 300 min, which showed 84% and 95% DCA photodegradation.

Covalent immobilization of lipase from Candida rugosa on epoxy-activated cloisite 30B as a new heterofunctional carrier and its application in the synthesis of banana flavor and production of biodiesel

In this paper, an epoxy-activated cloisite (ECL) was prepared as a new heterofunctional carrier via a reaction between cloisite 30B (CL) and epichlorohydrin and utilized for covalent immobilization of lipase from Candida rugosa. The lipase immobilized on the ECL (LECL) was successfully used in the olive oil hydrolysis, synthesis of isoamyl acetate (banana flavor), and biodiesel production. The TGA, FT-IR, SEM, and XRD were used to characterize CL, ECL, and LECL. The influences of temperature, pH, thermal stability, and storage capacity were examined in the olive oil hydrolysis. The effects of solvent, temperature, time, water content, and substrates molar ratio on the yields of ester and biodiesel were also investigated. In the optimized conditions, the hydrolytic activity of LECL was 1.85 ± 0.05 U/ mg, and the maximum yield of ester and biodiesel was 91.6% and 95.4%, respectively. The LECL showed good thermal stability and storage capacity compared to the free lipase. Additionally, LECL was reusable for both esterification and transesterification after being used for nine cycles.

Design of amino-functionalized hollow mesoporous silica cube for enzyme immobilization and its application in synthesis of phosphatidylserine

In this study, hollow mesoporous silica cube (HMSC) modified with amino (-NH₂) were synthesized and applied in the immobilization of phospholipase D (PLD) via physical adsorption and chemical cross-linking strategy. The amino-functionalized nano carrier HMSC represented excellent immobilization ability and achieved 87.15 % immobilization rate. The immobilized PLD has wider pH application range and thermal stability, and maintained over 90% of the initial activity after incubation at 50 °C for 2 h. After 50 days of storage at 4 ℃, immobilized PLD retained 40.12 % of its initial activity while free PLD lost 88.28% of its initial activity. The modified HMSC with immobilized PLD (HMSC-NH₂-PLD) retained 50.73% activities after 9 consecutive reuses. Using the HMSC-NH₂-PLD, a high-efficient method for the conversion of phosphatidylserine (PS) from phosphatidylcholine (PC) and L-serine was proposed. The HMSC-NH₂-PLD exhibited prominent enzymatic activity for PS synthesis, the maximal conversion of PS was 90.40% with a catalytic efficiency (CE) of 31.95 μmol / (g h under the optimal conditions. The research in this paper provides a sustainable and efficient biocatalysis application for PS synthesis.