Novel Archaeal Histamine Oxidase from Natronobeatus ordinarius: Insights into Histamine Degradation for Enhancing Food Safety

Histamine, found abundantly in salt-fermented foods, poses a risk of food poisoning. Natronobeatus ordinarius, a halophilic archaeon isolated from a salt lake, displayed a strong histamine degradation ability. Its histamine oxidase (HOD) gene was identified (hodNbs). This is the first report of an archaeal HOD. The HODNbs protein was determined to be a tetramer with a molecular weight of 307 kDa. HODNbs displayed optimum activity at 60-65 °C, 1.5-2.0 M NaCl, and pH 6.5. Notably, within the broad NaCl range between 0.5 and 2.5 M, HODNbs retained above 50% of its maximum activity. HODNbs exhibited good thermal stability, pH stability, and salinity tolerance. HODNbs was able to degrade various biogenic amines. The Vmax of HODNbs for histamine was 0.29 μmol/min/mg, and the Km was 0.56 mM. HODNbs exhibited high efficiency in histamine removal from fish sauce, namely, 100 μg of HODNbs degraded 5.63 mg of histamine (37.9%) in 10 g of fish sauce within 24 h at 50 °C. This study showed that HODNbs with excellent enzymatic properties has promising application potentials to degrade histamine in high-salt foods.

Production, purification, properties and current perspectives for modification and application of microbial lipases

With the industrialization and development of modern science, the application of enzymes as green and environmentally friendly biocatalysts in industry has been increased widely. Among them, lipase (EC. 3.1.1.3) is a very prominent biocatalyst, which has the ability to catalyze the hydrolysis and synthesis of ester compounds. Many lipases have been isolated from various sources, such as animals, plants and microorganisms, among which microbial lipase is the enzyme with the most diverse enzymatic properties and great industrial application potential. It therefore has promising applications in many industries, such as food and beverages, waste treatment, biofuels, leather, textiles, detergent formulations, ester synthesis, pharmaceuticals and medicine. Although many microbial lipases have been isolated and characterized, only some of them have been commercially exploited. In order to cope with the growing industrial demands and overcome these shortcomings to replace traditional chemical catalysts, the preparation of new lipases with thermal/acid-base stability, regioselectivity, organic solvent tolerance, high activity and yield, and reusability through excavation and modification has become a hot research topic.

Cloning and Characterization of Chitin Deacetylase from Euphausia superba

Chitin deacetylase (CDA) can catalyze the deacetylation of chitin to produce chitosan. In this study, we identified and characterized a chitin deacetylase gene from Euphausia superba (EsCDA-9k), and a soluble recombinant protein chitin deacetylase from Euphausia superba of molecular weight 45 kDa was cloned, expressed, and purified. The full-length cDNA sequence of EsCDA-9k was 1068 bp long and encoded 355 amino acid residues that contained the typical domain structure of carbohydrate esterase family 4. The predicted three-dimensional structure of EsCDA-9k showed a 67.32% homology with Penaeus monodon. Recombinant chitin deacetylase had the highest activity at 40 °C and pH 8.0 in Tris-HCl buffer. The enzyme activity was enhanced by metal ions Co2+, Fe3+, Ca2+, and Na+, while it was inhibited by Zn2+, Ba2+, Mg2+, and EDTA. Molecular simulation of EsCDA-9k was conducted based on sequence alignment and homology modeling. The EsCDA-9k F18G mutant showed a 1.6-fold higher activity than the wild-type enzyme. In summary, this is the first report of the cloning and heterologous expression of the chitin deacetylase gene in Euphausia superba. The characterization and function study of EsCDA-9k will serve as an important reference point for future application.

Multiple Origins of Bioluminescence in Beetles and Evolution of Luciferase Function

Bioluminescence in beetles has long fascinated biologists, with diverse applications in biotechnology. To date, however, our understanding of its evolutionary origin and functional variation mechanisms remains poor. To address these questions, we obtained high-quality reference genomes of luminous and nonluminous beetles in 6 Elateroidea families. We then reconstructed a robust phylogenetic relationship for all luminous families and related nonluminous families. Comparative genomic analyses and biochemical functional experiments suggested that gene evolution within Elateroidea played a crucial role in the origin of bioluminescence, with multiple parallel origins observed in the luminous beetle families. While most luciferase-like proteins exhibited a conserved nonluminous amino acid pattern (TLA346 to 348) in the luciferin-binding sites, luciferases in the different luminous beetle families showed divergent luminous patterns at these sites (TSA/CCA/CSA/LVA). Comparisons of the structural and enzymatic properties of ancestral, extant, and site-directed mutant luciferases further reinforced the important role of these sites in the trade-off between acyl-CoA synthetase and luciferase activities. Furthermore, the evolution of bioluminescent color demonstrated a tendency toward hypsochromic shifts and variations among the luminous families. Taken together, our results revealed multiple parallel origins of bioluminescence and functional divergence within the beetle bioluminescent system.

UV mutagenesis for lipase overproduction from Bacillus cereus ATA179, nutritional optimization, characterization and its usability in the detergent industry

In this study, the wild-type Bacillus cereus ATA179 was mutagenized by random UV mutagenesis to increase lipase production. The mutant with maximum lipolytic activity was named Bacillus cereus EV4. The mutant strain (10.6 U/mL at 24 h) produced 60% more enzyme than the wild strain (6.6 U/mL at 48 h). Nutritional factors on lipase production were investigated. Sucrose was the best carbon source, (NH4)2HPO4 was the best nitrogen source and CuSO4 was the best metal ion source. Mutant EV4 showed a 32% increase in lipase production in the modified medium. The optimum temperature and pH were found to be 60 °C and 7.0, respectively. CuSO4, CaCl2, LiSO4, KCl, BaCl2, and Tween 20 had an activating effect on the enzyme. Vmax and Km values were found to be 17.36 U/mL and 0.036 mM, respectively. The molecular weight was determined as 28.2 kDa. The activity of lipase was found to be stable up to 60 days at 20 °C, 75 days at 4 °C, and 90 days at -20 °C. The potential of lipase in the detergent industry was investigated. The enzyme was not affected by detergent additives but was effective in removing stains in fabrics contaminated with oily substances.

[Functional characterization and enzymatic properties of flavonoid glycosyltransferase gene CtUGT49 in Carthamus tinctorius]

Carthami Flos, as a traditional blood-activating and stasis-resolving drug, possesses anti-tumor, anti-inflammatory, and immunomodulatory pharmacological activities. Flavonoid glycosides are the main bioactive components in Carthamus tinctorius. Glycosyltransferase deserves to be studied in depth as a downstream modification enzyme in the biosynthesis of active glycoside compounds. This study reported a flavonoid glycosyltransferase CtUGT49 from C. tinctorius based on the transcriptome data, followed by bioinformatic analysis and the investigation of enzymatic properties. The open reading frame(ORF) of the gene was 1 416 bp, encoding 471 amino acid residues with the molecular weight of about 52 kDa. Phylogenetic analysis showed that CtUGT49 belonged to the UGT73 family. According to in vitro enzymatic results, CtUGT49 could catalyze naringenin chalcone to the prunin and choerospondin, and catalyze phloretin to phlorizin and trilobatin, exhibiting good substrate versatility. After the recombinant protein CtUGT49 was obtained by hetero-logous expression and purification, the enzymatic properties of CtUGT49 catalyzing the formation of prunin from naringenin chalcone were investigated. The results showed that the optimal pH value for CtUGT49 catalysis was 7.0, the optimal temperature was 37 ℃, and the highest substrate conversion rate was achieved after 8 h of reaction. The results of enzymatic kinetic parameters showed that the K_m value was 209.90 μmol·L~(-1) and k_(cat) was 48.36 s~(-1) calculated with the method of Michaelis-Menten plot. The discovery of the novel glycosyltransferase CtUGT49 is important for enriching the library of glycosylation tool enzymes and provides a basis for analyzing the glycosylation process of flavonoid glycosides in C. tinctorius.

[Expression and characterization of mesophilic GH1 β-glucosidase CdBglA from acidophilic Cuniculiplasma divulgatum]

β-glucosidase has important applications in food, pharmaceutics, biomass conversion and other fields, exploring β-glucosidase with strong adaptability and excellent properties thus has received extensive interest. In this study, a novel glucosidase from the GH1 family derived from Cuniculiplasma divulgatum was cloned, expressed, and characterized, aiming to find a better β-glucosidase. The amino acid sequences of GH1 family glucosidase derived from C. divulgatum were obtained from the NCBI database, and a recombinant plasmid pET-30a(+)-CdBglA was constructed. The recombinant protein was induced to express in Escherichia coli BL21(DE3). The enzymatic properties of the purified CdBglA were studied. The molecular weight of the recombinant CdBglA was 56.0 kDa. The optimum pH and temperature were 5.5 and 55 ℃, respectively. The enzyme showed good pH stability, 92.33% of the initial activity could be retained when treated under pH 5.5-11.0 for 1 h. When pNPG was used as a substrate, the kinetic parameters Km, Vmax and Kcat/Km were 0.81 mmol, 291.99 μmol/(mg·min), and 387.50 s-1 mmol-1, respectively. 90.33% of the initial enzyme activity could be retained when CdBglA was placed with various heavy metal ions at a final concentration of 5 mmol/L. The enzyme activity was increased by 28.67% under 15% ethanol solution, remained unchanged under 20% ethanol, and 43.68% of the enzyme activity could still be retained under 30% ethanol. The enzyme has an obvious activation effect at 0-1.5 mol/L NaCl and can tolerate 0.8 mol/L glucose. In conclusion, CdBglA is an acidic and mesophilic enzyme with broad pH stability and strong tolerance to most metal ions, organic solvents, NaCl and glucose. These characteristics may facilitate future theoretical research and industrial production.

Dextranase Production Using Marine Microbacterium sp. XD05 and Its Application

Dextranase, also known as glucanase, is a hydrolase enzyme that cleaves α-1,6 glycosidic bonds. In this study, a dextranase-producing strain was isolated from water samples of the Qingdao Sea and identified as Microbacterium sp. This strain was further evaluated for growth conditions, enzyme-producing conditions, enzymatic properties, and hydrolysates. Yeast extract and sodium chloride were found to be the most suitable carbon and nitrogen sources for strain growth, while sucrose and ammonium sodium were found to be suitable carbon and nitrogen sources for fermentation. The optimal pH was 7.5, with a culture temperature of 40 °C and a culture time of 48 h. Dextranase produced by strain XD05 showed good thermal stability at 40 °C by retaining more than 70% relative enzyme activity. The pH stability of the enzyme was better under a weak alkaline condition (pH 6.0-8.0). The addition of NH4+ increased dextranase activity, while Co2+ and Mn2+ had slight inhibitory effects on dextranase activity. In addition, high-performance liquid chromatography showed that dextran is mainly hydrolyzed to maltoheptanose, maltohexanose, maltopentose, and maltootriose. Moreover, it can form corn porous starch. Dextranase can be used in various fields, such as food, medicine, chemical industry, cosmetics, and agriculture.

[Biochemical properties of Scedosporium aurantiacum extracellular elastase-like protease]

Extracellular elastase-like protease is one of the key virulence proteases of Scedosporium aurantiacum. To date, little is known about this enzyme in terms of genetic information, structure, properties and virulence mechanism due to the difficulties in purification caused by its low secretion amount, high specific activity, uncompleted genome sequencing and annotation. This work investigated the gene, structure and enzymatic properties of this enzyme. The S. aurantiacum elastase-like protease from the fungal culture supernatant was analyzed through tandem mass spectrometry (MS/MS) approach, illustrating its primary structure. Bioinformatics tools were employed to predict the conserved domain and tertiary structure, the enzymatic properties were also studied. It turned out that S. aurantiacum extracellular elastase-like protease demonstrated well hydrolysis towards elastin and bovine achilles tendon collagen, with Vmax of 18.14 μg/s and 17.57 μg/s respectively, better than fish scale gelatin, with the lowest hydrolysis effect on casein. Its activity towards elastin was lower than that of the elastase from porcine pancreas, with values of Kcat/Km of 3.541 (μg/s) and 4.091 (μg/s), respectively. It was an alkaline protease, with optimal pH 8.2 and temperature 37 oC. Zn2+ promoted the enzymatic activity while Ca2+, Mg2+, Na+, elastatinal and PMSF inhibited its activity. Its sequence was similar to Paecilomyces lilacinus secreted serine protease (PDB Entry: c3f7oB_) with multiple conserved fractions each containing more than 7 amino acids, thus suitable for design of PCR primer. This study increased our knowledge on S. aurantiacum extracellular elastase-like protease in terms of structure and enzymatic properties, and may facilitate later studies on protein expression and virulence mechanism.

Production, Characterization and Application of a Novel Chitosanase from Marine Bacterium Bacillus paramycoides BP-N07

Chitooligosaccharides (COS), a high-value chitosan derivative, have many applications in food, pharmaceuticals, cosmetics and agriculture owing to their unique biological activities. Chitosanase, which catalyzes the hydrolysis of chitosan, can cleave β-1,4 linkages to produce COS. In this study, a chitosanase-producing Bacillus paramycoides BP-N07 was isolated from marine mud samples. The chitosanase enzyme (BpCSN) activity was 2648.66 ± 20.45 U/mL at 52 h and was able to effectively degrade chitosan. The molecular weight of purified BpCSN was approximately 37 kDa. The yield and enzyme activity of BpCSN were 0.41 mg/mL and 8133.17 ± 47.83 U/mg, respectively. The optimum temperature and pH of BpCSN were 50 °C and 6.0, respectively. The results of the high-performance liquid chromatography (HPLC) and thin-layer chromatography (TLC) of chitosan treated with BpCSN for 3 h showed that it is an endo-chitosanase, and the main degradation products were chitobiose, chitotriose and chitotetraose. BpCSN was used for the preparation of oligosaccharides: 1.0 mg enzyme converted 10.0 g chitosan with 2% acetic acid into oligosaccharides in 3 h at 50 °C. In summary, this paper reports that BpCSN has wide adaptability to temperature and pH and high activity for hydrolyzing chitosan substrates. Thus, BpCSN is a chitosan decomposer that can be used for producing chitooligosaccharides industrially.

[Expression, purification and characterization of a novel bis (hydroxyethyl) terephthalate hydrolase from Hydrogenobacter thermophilus]

PET (polyethylene terephthalate) is one of the most important petrochemicals that is widely used in mineral water bottles, food and beverage packaging and textile industry. Because of its stability under environmental conditions, the massive amount of PET wastes caused serious environmental pollution. The use of enzymes to depolymerize PET wastes and upcycling is one of the important directions for plastics pollution control, among which the key is the depolymerization efficiency of PET by PET hydrolase. BHET (bis(hydroxyethyl) terephthalate) is the main intermediate of PET hydrolysis, its accumulation can hinder the degradation efficiency of PET hydrolase significantly, and the synergistic use of PET hydrolase and BHET hydrolase can improve the PET hydrolysis efficiency. In this study, a dienolactone hydrolase from Hydrogenobacter thermophilus which can degrade BHET (HtBHETase) was identified. After heterologous expression in Escherichia coli and purification, the enzymatic properties of HtBHETase were studied. HtBHETase shows higher catalytic activity towards esters with short carbon chains such as p-nitrophenol acetate. The optimal pH and temperature of the reaction with BHET were 5.0 and 55 ℃, respectively. HtBHETase exhibited excellent thermostability, and retained over 80% residual activity after treatment at 80 ℃ for 1 hour. These results indicate that HtBHETase has potential in biological PET depolymerization, which may facilitate the enzymatic degradation of PET.

[Enzymatic properties and degradation characterization of a bis(2-hydroxyethyl) terephthalate hydrolase from Saccharothrix sp.]

The discovery of new enzymes for poly(ethylene terephthalate) (PET) degradation has been a hot topic of research globally. Bis-(2-hydroxyethyl) terephthalate (BHET) is an intermediate compound in the degradation of PET and competes with PET for the substrate binding site of the PET-degrading enzyme, thereby inhibiting further degradation of PET. Discovery of new BHET degradation enzymes may contribute to improving the degradation efficiency of PET. In this paper, we discovered a hydrolase gene sle (ID: CP064192.1, 5085270-5086049) from Saccharothrix luteola, which can hydrolyze BHET into mono-(2-hydroxyethyl) terephthalate (MHET) and terephthalic acid (TPA). BHET hydrolase (Sle) was heterologously expressed in Escherichia coli using a recombinant plasmid, and the highest protein expression was achieved at a final concentration of 0.4 mmol/L of isopropyl-β-d-thiogalactoside (IPTG), an induction duration of 12 h and an induction temperature of 20 ℃. The recombinant Sle was purified by nickel affinity chromatography, anion exchange chromatography, and gel filtration chromatography, and its enzymatic properties were also characterized. The optimum temperature and pH of Sle were 35 ℃ and 8.0, and more than 80% of the enzyme activity could be maintained in the range of 25-35 ℃ and pH 7.0-9.0 and Co2+ could improve the enzyme activity. Sle belongs to the dienelactone hydrolase (DLH) superfamily and possesses the typical catalytic triad of the family, and the predicted catalytic sites are S129, D175, and H207. Finally, the enzyme was identified as a BHET degrading enzyme by high performance liquid chromatography (HPLC). This study provides a new enzyme resource for the efficient enzymatic degradation of PET plastics.

Structures, Biochemical Characteristics, and Functions of β-Xylosidases

The complete degradation of abundant xylan derived from plants requires the participation of β-xylosidases to produce the xylose which can be converted to xylitol, ethanol, and other valuable chemicals. Some phytochemicals can also be hydrolyzed by β-xylosidases into bioactive substances, such as ginsenosides, 10-deacetyltaxol, cycloastragenol, and anthocyanidins. On the contrary, some hydroxyl-containing substances such as alcohols, sugars, and phenols can be xylosylated by β-xylosidases into new chemicals such as alkyl xylosides, oligosaccharides, and xylosylated phenols. Thus, β-xylosidases shows great application prospects in food, brewing, and pharmaceutical industries. This review focuses on the molecular structures, biochemical properties, and bioactive substance transformation function of β-xylosidases derived from bacteria, fungi, actinomycetes, and metagenomes. The molecular mechanisms of β-xylosidases related to the properties and functions are also discussed. This review will serve as a reference for the engineering and application of β-xylosidases in food, brewing, and pharmaceutical industries.

Heterologous expression and characterization of Bacillus velezensis SW5 serine protease involved in the hydrolysis of anchovy protein

BACKGROUND

Bacillus velezensis SW5, with good enzyme production ability, was isolated and identified in our laboratory from fermented fish sauce. Its galactosidase has been expressed in Escherichia coli, which could hydrolyze lactose in milk. The present study aims to express a novel serine protease gene (SPr-SW5) of this strain by Bacillus subtilis WB800N, and applies the expressed enzyme in hydrolysis of anchovy to prepare antioxidant substances, aiming to alleviate the waste of low-value fish resources.

RESULTS

SPr-SW5 with the open reading frame of 1353 bp encodes a serine protease (SPr-SW5) with 450 amino acids. The theoretical molecular weight and isoelectric point are 47.2 kDa and 5.22, respectively. The successful expression of SPr-SW5 in B. subtilis WB800N was confirmed by a skim milk plate test. Its optimal temperature and pH were 50 °C and 8.0, respectively. SPr-SW5 activity was increased by Ca²⁺ and Zn²⁺ , but inhibited by Fe³⁺ . Furthermore, SPr-SW5 was tolerant to 1% Tween-40 and Tween-80; however, its activity was strongly inhibited by 10 mm phenylmethylsulfonyl fluoride. Additionally, SPr-SW5 could be capable of hydrolyzing anchovy, the hydrolysate (AHP) at 10 g L^-1 , with 2,2-diphenyl-1-picrylhydrazyl and hydroxyl (·OH) scavenging rates of 73.21% and 79.71%, displaying good antioxidant activity.

CONCLUSION

The novel SPr-SW5 was successfully expressed in B. subtilis WB800N. It exhibited excellent temperature stability and good tolerance to several metal ions. In addition, the anchovy hydrolyzed by expressed SPr-SW5 has good antioxidant ability. Overall, this research lays a good foundation for SPr-SW5 with respect to exploration and application in the food industry as enzyme preparation. © 2023 Society of Chemical Industry.

Purification and Characterization of the Enzyme Fucoidanase from Cobetia amphilecti Utilizing Fucoidan from Undaria pinnatifida

Fucoidanase is an unstable enzyme with high specificity that requires a large about of time to screen it from microorganisms. In this study, enzymatic hydrolysis was used to produce low-molecular-weight fucoidan from microorganisms via the degradation of high-molecular-weight fucoidan without damage to the sulfate esterification structure of oligosaccharide. The microbial strain HN-25 was isolated from sea mud and was made to undergo mutagenicity under ultraviolet light. Fucoidanase was extracted via ultrasonication and its enzymatic activity was improved via optimization of the ultrasonic conditions. The enzymatic properties and degradation efficiency of fucoidanase were characterized. The microbial strain HN-25 is a Gram-negative aerobic and rod-shaped-cell bacterium, and therefore was identified as Cobetia amphilecti via 16s rDNA. The results proved that fucoidanase is a hydrolytic enzyme with a molecular weight of 35 kDa and with high activity and stability at 30 °C and pH 8.0. The activity of fucoidanase was significantly enhanced by sodium and calcium ions and inhibited by a copper ion and ethylenediaminetetraacetate (EDTA). There was a significant decrease in the molecular weight of fucoidan after enzymatic hydrolysis. The low-molecular-weight fuicodan was divided into four fractions, mainly concentrated at F3 (20~10 kDa) and F4 (≤6 kDa). These consequences suggest that fucoidanase obtained from Cobetia amphilecti is stable and efficient and could be a good tool in the production of bioactive compounds.

[Expression and characterization of a bifunctional thermal β-glucosidase IuBgl3 from thermophilic archaeon Infirmifilum uzonense]

β-glucosidase has important applications in food, medicine, biomass conversion and other fields. Therefore, exploring β-glucosidase with strong stability and excellent properties is a research hotspot. In this study, a GH3 family β-glucosidase gene named Iubgl3 was successfully cloned from Infirmifilum uzonense. Sequence analysis showed that the full length of Iubgl3 was 2 106 bp, encoding 702 amino acids, with a theoretical molecular weight of 77.0 kDa. The gene was cloned and expressed in E. coli and the enzymatic properties of purified IuBgl3 were studied. The results showed that the optimal pH and temperature for pNPG hydrolysis were 5.0 and 85 ℃, respectively. The enzyme has good thermal stability, and more than 85% of enzyme activity can be retained after being treated at 80 ℃ for2 h. This enzyme has good pH stability and more than 85% of its activity can be retained after being treated at pH 4.0-11.0 for 1 h. It was found that the enzyme had high hydrolysis ability to p-nitrophenyl β-d-glucoside (pNPG) and p-nitrophenyl β-d-xylopyranoside (pNPX). When pNPG was used as the substrate, the kinetic parameters K_m and V_max were 0.38 mmol and 248.55 μmol/(mg·min), respectively, and the catalytic efficiency k_cat/K_m was 6 149.20 s^-1mmol^-1. Most metal ions had no significant effect on the enzyme activity of IuBgl3. SDS completely inactivated the enzyme, while EDTA increased the enzyme activity by 30%. This study expanded the β-glucosidase gene diversity of the thermophilic archaea GH3 family and obtained a thermostable acid bifunctional enzyme with good industrial application potential.

[Preparation and catalytic properties of catalase-inorganic hybrid nanoflowers]

Catalase is widely used in the food, medical, and textile industries. It possesses exceptional properties including high catalytic efficiency, high specificity, and environmental friendliness. Free catalase cannot be recycled and reused in industry, resulting in a costly industrial biotransformation process if catalase is used as a core ingredient. Developing a simple, mild, cost-effective, and environmentally friendly approach to immobilize catalase is anticipated to improve its utilization efficiency and enzymatic performance. In this study, the catalase KatA derived from Bacillus subtilis 168 was expressed in Escherichia coli. Following separation and purification, the purified enzyme was prepared as an immobilized enzyme in the form of enzyme-inorganic hybrid nanoflowers, and the enzymatic properties were investigated. The results indicated that the purified KatA was obtained through a three-step procedure that included ethanol precipitation, DEAE anion exchange chromatography, and hydrophobic chromatography. Then, by optimizing the process parameters, a novel KatA/Ca₃(PO₄)₂ hybrid nanoflower was developed. The optimum reaction temperature of the free KatA was determined to be 35 ℃, the optimum reaction temperature of KatA/Ca₃(PO₄)₂ hybrid nanoflowers was 30-35 ℃, and the optimum reaction pH of both was 11.0. The free KatA and KatA/Ca₃(PO₄)₂ hybrid nanoflowers exhibited excellent stability at pH 4.0-11.0 and 25-50 ℃. The KatA/Ca₃(PO₄)₂ hybrid nanoflowers demonstrated increased storage stability than that of the free KatA, maintaining 82% of the original enzymatic activity after 14 d of storage at 4 ℃, whereas the free KatA has only 50% of the original enzymatic activity. In addition, after 5 catalytic reactions, the nanoflower still maintained 55% of its initial enzymatic activity, indicating that it has good operational stability. The K_m of the free KatA to the substrate hydrogen peroxide was (8.80±0.42) mmol/L, and the k_cat/K_m was (13 151.53± 299.19) L/(mmol·s). The K_m of the KatA/Ca₃(PO₄)₂ hybrid nanoflowers was (32.75±2.96) mmol/L, and the k_cat/K_m was (4 550.67±107.51) L/(mmol·s). Compared to the free KatA, the affinity of KatA/Ca₃(PO₄)₂ hybrid nanoflowers to the substrate hydrogen peroxide was decreased, and the catalytic efficiency was also decreased. In summary, this study developed KatA/Ca₃(PO₄)₂ hybrid nanoflowers using Ca²⁺ as a self-assembly inducer, which enhanced the enzymatic properties and will facilitate the environmentally friendly preparation and widespread application of immobilized catalase.

Screening of Polyethylene-Degrading Bacteria from Rhyzopertha Dominica and Evaluation of Its Key Enzymes Degrading Polyethylene

Polyethylene (PE) is widely used, and it has caused serious environmental problems due to its difficult degradation. At present, the mechanism of PE degradation by microorganisms is not clear, and the related enzymes of PE degradation need to be further explored. In this study, Acinetobacter baumannii Rd-H2 was obtained from Rhizopertha dominica, which had certain degradation effect on PE plastic. The degradation performance of the strains was evaluated by weight loss rate, SEM, ATR/FTIR, WCA, and GPC. The multi-copper oxidase gene abMco, which may be one of the key genes for PE degradation, was analyzed and successfully expressed in E. coli. The laccase activity of the gene was determined, and the enzyme activity was up to 159.82 U/L. The optimum temperature and pH of the enzyme are 45 °C and 4.5 respectively. It shows good stability at 30-45 °C. Cu²⁺ can activate the enzyme. The abMCO was used to degrade polyethylene film, showing a good degradation effect, proving that the enzyme could be the key to degrading PE.

Extraction and Characterization of Lysozyme from Salted Duck Egg White

Salted duck egg white (SDEW), as the main by-product in the production process of salted egg yolk, has not been effectively used as a food resource because of its high salt concentration. This study creatively used isoelectric point precipitation, ultrafiltration, and cation exchange to separate and purify lysozyme from SDEW and preliminarily explored the enzymatic properties of lysozyme. The results showed that the relative molecular weight of lysozyme was about 14 KDa, and the specific activity of lysozyme reached 18,300 U/mg. Lysozyme had good stability in the temperature range of 30 °C to 60 °C and pH of 4 to 7. Metal ions, Fe²⁺, Cu²⁺, and Zn²⁺, strongly inhibited lysozyme activity. Different surfactants showed certain inhibition effects on lysozyme from SDEW, among which glycerin had the strongest inhibitory effect. This study aimed to provide a theoretical reference for industrial purification and production of lysozyme from SDEW.

Heterologous Expression of a Thermostable α-Galactosidase from Parageobacillus thermoglucosidasius Isolated from the Lignocellulolytic Microbial Consortium TMC7

α-Galactosidase is a debranching enzyme widely used in the food, feed, paper, and pharmaceuticals industries and plays an important role in hemicellulose degradation. Here, T26, an aerobic bacterial strain with thermostable α-galactosidase activity, was isolated from laboratory-preserved lignocellulolytic microbial consortium TMC7, and identified as Parageobacillus thermoglucosidasius. The α-galactosidase, called T26GAL and derived from the T26 culture supernatant, exhibited a maximum enzyme activity of 0.4976 IU/ml when cultured at 60°C and 180 rpm for 2 days. Bioinformatics analysis revealed that the α-galactosidase T26GAL belongs to the GH36 family. Subsequently, the pET-26 vector was used for the heterologous expression of the T26 α-galactosidase gene in Escherichia coli BL21 (DE3). The optimum pH for α-galactosidase T26GAL was determined to be 8.0, while the optimum temperature was 60°C. In addition, T26GAL demonstrated a remarkable thermostability with more than 93% enzyme activity, even at a high temperature of 90°C. Furthermore, Ca²⁺ and Mg²⁺ promoted the activity of T26GAL while Zn²⁺ and Cu²⁺ inhibited it. The substrate specificity studies revealed that T26GAL efficiently degraded raffinose, stachyose, and guar gum, but not locust bean gum. This study thus facilitated the discovery of an effective heat-resistant α-galactosidase with potent industrial application. Meanwhile, as part of our research on lignocellulose degradation by a microbial consortium, the present work provides an important basis for encouraging further investigation into this enzyme complex.

Establishment of a Novel Cell Surface Display Platform Based on Natural "Chitosan Beads" of Yeast Spores

Cell surface display technology, which expresses and anchors proteins on the surface of microbial cells, has broad application prospects in many fields, such as protein library screening, biocatalysis, and biosensor development. However, traditional cell surface display systems have disadvantages: the molecular weight of phage display proteins cannot be too large; bacterial display lacks the post-translational modification process for eukaryotic proteins; yeast display is prone to excessive protein glycosylation and misfolding of multisubunit proteins; and the compatibility of Bacillus subtilis spore display needs to be further improved. Therefore, it is extremely valuable to develop an efficient surface display platform with strong universality and stress resistance properties. Although yeast surface display systems have been extensively investigated, the establishment of a surface display platform using yeast spores has rarely been reported. In this study, a novel cell surface display platform based on natural "chitosan beads" of yeast spores was developed. The target protein in fusion with the chitosan affinity protein (CAP) exhibited strong binding capability with "chitosan beads" of yeast spores in vitro and in vivo. Moreover, this protein display system showed highly preferable enzymatic properties and stability. As an example, the displayed LXYL-P1-2-CAP demonstrated high thermostability and reusability (60% of the initial activity after seven cycles of reuse), high storage stability (75% of original activity after 8 weeks), and excellent tolerance to a concentration up to 75% (v/v) organic reagents. To prove the practicability of this surface display system, the semisynthesis of paclitaxel intermediate was demonstrated and its highest conversion rate was 92% using 0.25 mM substrate. This study provides a novel and useful platform for the surface display of proteins, especially for multimeric macromolecular proteins of eukaryotic origin.

[Recombinant expression of black sesame polyphenol oxidase and its enzymatic properties]

To investigate the enzyme properties of the black sesame polyphenol oxidase (BsPPO), a synthesized Bsppo gene was cloned into the vector pMAL-c5x and expressed in E. coli. Subsequently, the MBP fusion label in the recombinant protein was removed by protease digestion after affinity purification. The synthesized Bsppo gene contained 1 752 bp which encodes 585 amino acids with a deduced molecular weight of 65.3 kDa. Transformation of the recombinant vector into E. coli BL21(DE3) resulted in soluble expression of the fusion protein MBP-BsPPO. The enzymatic properties of the recombinant BsPPO was investigated after MBP fusion tag excision followed by affinity purification. The results demonstrated that the optimal temperature and pH for BsPPO was 25°C and 4.0, respectively. BsPPO exhibited a good stability under low temperature and acidic environment. Low-intensity short-term light exposure increased the activity of BsPPO. Cu²⁺ could improve the activity of BsPPO while Zn²⁺ and Ca²⁺ showed the opposite effect. BsPPO could catalyze the oxidation of monophenols, diphenols, and triphenols, and exhibited good catalytic activity on l-tyrosine and vanillic acid. Moreover, BsPPO exhibited high catalytic activity on black sesame metabolites, including 2-methoxy cinnamic acid, indole-3-carboxylic acid and phloretin. These results may serve as a basis for further characterization of BsPPO.

[Characterization and identification of Lactobacillus fermentum 4,6-α-glucosyltransferase and its products]

4,6-α-glucosyltransferases (4,6-α-GTs), which converts amylose into α(1-6) bonds-containing α-glucan, possesses great application potential in enzymatic synthesis of dietary fiber. Primers were designed according to the conserved motifs existing in the amino acid sequence of 4,6-α-GTs, and used to amplify a putative GTFB-Like 4,6-α-GTs gene (named as gtf16) from the genomic DNA of Lactobacillus. The gtf16 gene was cloned into the plasmid pET15b, expressed in Escherichia coli BL21(DE3), followed by purification and characterization. The optimum pH and the optimum temperature of the purified enzyme were 5.0 and 40 °C, respectively. The biotransformation product of this enzyme was systematically characterized by thin-layer chromatography, NMR spectroscopy, and hydrolysis reaction. The Gtf16-catalyzed product shows a similar structure to that of the isomalto/malto-polysaccharide (IMMP), which is the amylose-derived product catalyzed by GtfB from Lactobacillus reuteri 121. Moreover, The Gtf16-catalyzed product contains up to 75% of α(1-6) bonds and has an average molecular weight of 23 793 Da. Furthermore, the content of the anti-digestive components was 88.22% upon hydrolysis with digestive enzymes.

Characterization and Heterologous Expression of UDP-Glucose 4-Epimerase From a Hericium erinaceus Mutant with High Polysaccharide Production

Hericium erinaceus is an important medicinal fungus in traditional Chinese medicine because of its polysaccharides and other natural products. Compared terpenoids and polyketides, the analysis of synthetic pathway of polysaccharides is more difficult because of the many genes involved in central metabolism. In previous studies, A6180, encoding a putative UDP-glucose 4-epimerase (UGE) in an H. erinaceus mutant with high production of active polysaccharides, was significantly upregulated. Since there is no reliable genetic manipulation technology for H. erinaceus, we employed Escherichia coli and Saccharomyces cerevisiae to study the function and activity of A6180. The recombinant overexpression vector pET22b-A6180 was constructed for heterologous expression in E. coli. The enzymatic properties of the recombinant protein were investigated. It showed that the recombinant A6180 could strongly convert UDP-α-D-glucose into UDP-α-D-galactose under optimal conditions (pH 6.0, 30°C). In addition, when A6180 was introduced into S. cerevisiae BY4742, xylose was detected in the polysaccharide composition of the yeast transformant. This suggested that the protein coded by A6180 might be a multifunctional enzyme. The generated polysaccharides with a new composition of sugars showed enhanced macrophage activity in vitro. These results indicate that A6180 plays an important role in the structure and activity of polysaccharides. It is a promising strategy for producing polysaccharides with higher activity by introducing A6180 into polysaccharide-producing mushrooms.

Serum Albumin: A Multifaced Enzyme

Human serum albumin (HSA) is the most abundant protein in plasma, contributing actively to oncotic pressure maintenance and fluid distribution between body compartments. HSA acts as the main carrier of fatty acids, recognizes metal ions, affects pharmacokinetics of many drugs, provides the metabolic modification of some ligands, renders potential toxins harmless, accounts for most of the anti-oxidant capacity of human plasma, and displays esterase, enolase, glucuronidase, and peroxidase (pseudo)-enzymatic activities. HSA-based catalysis is physiologically relevant, affecting the metabolism of endogenous and exogenous compounds including proteins, lipids, cholesterol, reactive oxygen species (ROS), and drugs. Catalytic properties of HSA are modulated by allosteric effectors, competitive inhibitors, chemical modifications, pathological conditions, and aging. HSA displays anti-oxidant properties and is critical for plasma detoxification from toxic agents and for pro-drugs activation. The enzymatic properties of HSA can be also exploited by chemical industries as a scaffold to produce libraries of catalysts with improved proficiency and stereoselectivity for water decontamination from poisonous agents and environmental contaminants, in the so called “green chemistry” field. Here, an overview of the intrinsic and metal dependent (pseudo-)enzymatic properties of HSA is reported to highlight the roles played by this multifaced protein.

Isolation and Purification of Organophosphorus Hydrolases Secreted from Acetone-acclimated Phosphorus Accumulating Organisms and Study of Their Properties for Hydrophobic Organophosphorus Sensor

The present work studied an acclimation method for phosphorus accumulating organisms (PAOs) with a high content of acetone in culture solutions to develop microbial-based enzyme sensors for highly hydrophobic organophosphorus (OP) pesticides. Through three steps of cultivation and acclimation, only rod-shaped bacteria survived among the various PAOs. The extracellular enzymes released from the acclimated PAOs were salted out by using ammonium sulfate, then purified by a dialysis membrane and a DEAE-Sepharose FF anion exchange column. Two enzyme components were successfully separated-both of which showed hydrolase activity on disodium p-nitrophenyl phosphate (enzyme I, 1.57 μmol/(min·μg); enzyme II, 0.88 μmol/(min·μg) at 45°C). Further, SDS-PAGE gel electrophoresis results showed that the molecular weights of enzymes I and II were about 15.11 and 11.98 kDa, respectively. On this basis, the applicability of the enzyme in hydrophobic OP biosensors was demonstrated.

Immobilization of Phospholipase A1 Using a Protein-Inorganic Hybrid System

In this study, four kinds of phospholipase A1-metal (Al/Co/Cu/Mn) hybrid nanostructures were prepared for enhancing the stability of the free PLA1. The formed hybrid complexes were characterized by scanning electron microscope (SEM), Fourier infrared spectroscopy (FTIR), and X-ray diffraction (XRD). The stability and substrate specificity of immobilized enzymes were subsequently determined. After immobilization, the temperature tolerance of PLA1–metal hybrid nanostructures was enhanced. The relative activity of PLA1–Al/Co/Cu hybrid nanostructures remained above 60% at 50 °C, while that of free enzyme was below 5%. The thermal transition temperature measured by differential scanning calorimetry (DSC) was found to increase from 65.59 °C (free enzyme) to 173.14 °C, 123.67 °C, 96.31 °C, and 114.79 °C, referring to PLA1–Cu/Co/Al/Mn hybrid nanostructures, respectively. Additionally, after a storage for fourteen days at 4 °C, the immobilized enzymes could exhibit approximately 60% of the initial activity, while the free PLA1 was inactivated after four days of storage. In brief, using Co²⁺, Cu²⁺, Al³⁺, and Mn²⁺ as the hybridization materials for immobilization could improve the catalytic properties and stability of the free PLA1, suggesting a promising method for a wider application of PLA1 in many fields such as food, cosmetics, and the pharmaceutical industry.

[Enzymatic properties of α-L-rhamnosidase and the factors affecting its activity: a review]

α-L-rhamnosidase is a very important industrial enzyme that is widely distributed in a variety of organisms. α-L-rhamnosidase of different origins show functional diversity. For example, the optimal pH of α-L-rhamnosidase from bacteria is close to neutral or alkaline, while the optimal pH of α-L-rhamnosidase from fungi is in the acidic range. Furthermore, the enzymatic properties of α-L-rhamnosidases of different origins differ in terms of the optimal temperature, the thermal stability, and the substrate specificity, which determine the different applications of these enzymes. In this connection, it is crucial to elucidate the similarities and differences in the catalytic mechanism and substrate specificity of α-L-rhamnosidase of different origins through analyzing its enzymatic properties. Moreover, it is important to explore and understand the effects of aglycon and metal cations on enzyme activity and the competitive inhibition of L-rhamnose and glucose on enzymes. These knowledge can help discover α-L-rhamnosidase of industrial significance and promote its industrial application.

Lipase from new isolate Bacillus cereus ATA179: optimization of production conditions, partial purification, characterization and its potential in the detergent industry

In this study, 341 Bacillus sp. strains were isolated from agricultural soils of Turkey. The potent extracellular lipase producer was selected. It was identified by 16S rRNA, named as Bacillus cereus ATA179. Optimal nutritional and physical parameters for lipase production were determined. Sucrose as the carbon source, (NH₄)₂HPO₄ as the nitrogen source, CaCl₂ as the metal ion were obtained. The best results of physical parameters were stated at 45°C, pH 7.0, shaking rate 50 rpm, inoculation amount 7% and inoculum age 24 h. ATA179 strain showed a 51% increase in enzyme production in the modified medium created by optimizing nutritional and physical conditions. Optimum pH value and temperature were found as 6.0 and 55 °C, respectively. CaCl₂, Tween 20, Triton X-100 had an activating effect on enzyme activity. V_max and K_m kinetic values were found as 18.28 U/mL and 0.11 mM, respectively. The molecular weight was determined as 47 kDa. Lipase was found to be stable up to 75 days at -20 ºC. The potential of the enzyme in detergent industry was also investigated. It was not affected by detergent additives, but was found to be effective in removing oils from contaminated fabrics. This new lipase may have potential to be used in detergent industry.

Overexpression and characterization of a novel GH4 galactosidase with β-galactosidase activity from Bacillus velezensis SW5

A novel galactosidase gene (gal3149) was identified from Bacillus velezensis SW5 and heterologously expressed in Escherichia coli BL21 (DE3). The novel galactosidase, Gal3149, encoded by gal3149 in an open reading frame of 1,299 bp, was 433 amino acids in length. Protein sequence analysis showed that Gal3149 belonged to family 4 of glycoside hydrolases (GH4). Gal3149 displayed higher enzyme activity for the substrate 2-nitrophenyl-β-d-galactopyranoside (oNPG) than for 4-nitrophenyl-α-d-galactopyranoside (pNPαG). This is the first time that an enzyme belonging to GH4 has been shown to exhibit β-galactosidase activity. Gal3149 showed optimal activity at pH 8.0 and 50°C, and exhibited excellent thermal stability, with retention of 50% relative activity after incubation at a temperature range of 0 to 50°C for 48 h. Gal3149 activity was significantly improved by K⁺ and Na⁺, and was strongly or completely inhibited by Ag⁺, Zn²⁺, Tween-80, Cu²⁺, carboxymethyl cellulose, and oleic acid. The rate of hydrolyzed lactose in 1 mL of milk by 1 U of Gal3149 reached about 50% after incubation for 4 h. These properties lay a solid foundation for Gal3149 in application of the lactose-reduced dairy industry.

Enzymatic Properties of Recombinant Ligase Butelase-1 and Its Application in Cyclizing Food-Derived Angiotensin I-Converting Enzyme Inhibitory Peptides

Butelase-1 is an efficient ligase from Clitoria ternatea with wide applications in the food and biopharmaceutical fields. This research aimed to achieve high-efficiency expression of butelase-1 and explore its application in food-derived angiotensin I-converting enzyme (ACE) inhibitory peptides. The recombinant butelase-1 zymogen was prepared at a yield of 100 mg/L in Escherichia coli and successfully activated at pH 4.5, resulting in a 6973.8 U/L yield of activated butelase-1 with a specific activity of 348.69 U/mg and a catalytic efficiency of 9956 M^-1 s^-1. Activated butelase-1 exhibited considerable resistance to Tween-20, Triton X-100, and methanol. The "traceless" cyclization of ACE inhibitory peptides was realized using activated butelase-1, which resulted in higher stability and ACE inhibitory activity than those of the linear peptides. Our work proposed an efficient method for the preparation of butelase-1 and provided a promising model for its application in food fields.

[Characterization of inulosucrase and the enzymatic synthesis of inulin]

As a type of prebiotics and dietary fiber, inulin performs plenty of significant physiological functions and is applied in food and pharmaceutical fields. Inulosucrase from microorganisms can use sucrose as the substrate to synthesize inulin possessing higher molecular weight than that from plants. In this work, a hypothetical gene coding inulosucrase was selected from the GenBank database. The catalytic domain was remained by N- and C- truncation strategies, constructing the recombinant plasmid. The recombinant plasmid was expressed in E. coli expression system, and after purifying the crude enzyme by Ni²⁺ affinity chromatography, a recombinant enzyme with a molecular weight of approximately 65 kDa was obtained. The optimal pH and temperature of the recombinant enzyme were 5.5 and 45 °C, respectively, when sucrose was used as the sole substrate. The activity of this enzyme was inhibited by various metal ions at different degrees. After purifying the produced polysaccharide, nuclear magnetic resonance analysis was used to determine that the polysaccharide was inulin connected by β-(2,1) linkages. Finally, the conditions for the production of inulin were optimized. The results showed that the inulin production reached the maximum, approximately 287 g/L after 7 h, when sucrose concentration and enzyme dosage were 700 g/L and 4 U/mL, respectively. The conversion rate from sucrose to inulin was approximately 41%.

[Expression and characterization of β-N-acetylglucosaminidases from Bacillus coagulans DSM1 for N-acetyl-β-D glucosamine production]

β-N-acetylglucosaminidases (NAGases) can convert natural substrates such as chitin or chitosan to N-acetyl-β-D glucosamine (GlcNAc) monomer that is wildly used in medicine and agriculture. In this study, the BcNagZ gene from Bacillus coagulans DMS1 was cloned and expressed in Escherichia coli. The recombinant protein was secreted into the fermentation supernatant and the expression amount reached 0.76 mg/mL. The molecular mass of purified enzyme was 61.3 kDa, and the specific activity was 5.918 U/mg. The optimal temperature and pH of the BcNagZ were 75 °C and 5.5, respectively, and remained more than 85% residual activity after 30 min at 65 °C. The Mie constant Km was 0.23 mmol/L and the Vmax was 0.043 1 mmol/(L·min). The recombinant BcNagZ could hydrolyze colloidal chitin to obtain trace amounts of GlcNAc, and hydrolyze disaccharides to monosaccharide. Combining with the reported exochitinase AMcase, BcNagZ could produce GlcNAc from hydrolysis of colloidal chitin with a yield over 86.93%.

Cloning, expression, and bioinformatics analysis and characterization of a β-galactosidase from Bacillus coagulans T242

The activities of β-galactosidases from bacteria and molds are affected by temperature, pH, and other factors in the processing of dairy products, limiting their application, so it is necessary to find alternative lactases. In this study, the β-galactosidase gene from Bacillus coagulans T242 was cloned, co-expressed with a molecular chaperone in Escherichia coli BL21, and subjected to bioinformatic and kinetic analyses and lactase characterization. The results show that the enzyme is a novel thermostable neutral lactase with optimum hydrolytic activity at pH 6.8 and 50°C. The thermal stability and increased lactose hydrolysis activity of β-galactosidase in the presence of Ca²⁺ indicated its potential application in the dairy industry.

Characterization of a Novel Laccase LAC-Yang1 from White-Rot Fungus Pleurotus ostreatus Strain Yang1 with a Strong Ability to Degrade and Detoxify Chlorophenols

In this study, a laccase LAC-Yang1 was successfully purified from a white-rot fungus strain Pleurotus ostreatus strain yang1 with high laccase activity. The enzymatic properties of LAC-Yang1 and its ability to degrade and detoxify chlorophenols such as 2,6-dichlorophenol and 2,3,6-trichlorophenol were systematically studied. LAC-Yang1 showed a strong tolerance to extremely acidic conditions and strong stability under strong alkaline conditions (pH 9–12). LAC-Yang1 also exhibited a strong tolerance to different inhibitors (EDTA, SDS), metal ions (Mn²⁺, Cu²⁺, Mg²⁺, Na⁺, K⁺, Zn²⁺, Al³⁺, Co²⁺, and metal ion mixtures), and organic solvents (glycerol, propylene glycol). LAC-Yang1 showed good stability in the presence of Mg²⁺, Mn²⁺, glycerol, and ethylene glycol. Our results reveal the strong degradation ability of this laccase for high concentrations of chlorophenols (especially 2,6-dichlorophenol) and chlorophenol mixtures (2,6-dichlorophenol + 2,3,6-trichlorophenol). LAC-Yang1 displayed a strong tolerance toward a variety of metal ions (Na²⁺, Zn²⁺, Mn²⁺, Mg²⁺, K⁺ and metal ion mixtures) and organic solvents (glycerol, ethylene glycol) in its degradation of 2,6-dichlorophenol and 2,3,6-trichlorophenol. The phytotoxicity of 2,6-dichlorophenol treated by LAC-Yang1 was significantly reduced or eliminated. LAC-Yang1 demonstrated a good detoxification effect on 2,6-dichlorophenol while degrading this compound. In conclusion, LAC-Yang1 purified from Pleurotus ostreatus has great application value and potential in environmental biotechnology, especially the efficient degradation and detoxification of chlorophenols.

Synthesis of Citrate-Coated Penta-twinned Palladium Nanorods and Ultrathin Nanowires with a Tunable Aspect Ratio

Green and scalable methodologies for the preparation of metal nanoparticles with fine control of shape and size are of high interest in many areas including catalysis, nanomedicine, and nanodiagnostics. In this contribution, we describe a new synthetic method for the production of palladium (Pd) penta-twinned nanowires and nanorods utilizing sodium citrate, formic acid, ascorbic acid, and potassium bromide (KBr) in water, without the use of surfactants or polymers. The synthesis is green, fast, and without the need of complex setups. Interestingly, a microwave-assisted scale-up process has been developed. The combination of a synthetic protocol for seeds and the seed-mediated growth process allows us to synthesize nanorods and nanowires by modulating the concentration of KBr. The synthesized nanomaterials have been physicochemically characterized. High-resolution transmission electron microscopy shows that the nanorods and nanowires have a penta-twinned structure enclosed by {100} lateral facets. Moreover, the absence of sticky molecules or toxic byproducts guarantees the biocompatibility of the nanomaterials, while leaving the surface clean to perform enzymatic activities.

[Characterization of a sucrose phosphorylase from Leuconostoc mesenterides for the synthesis of α-arbutin]

Sucrose phosphorylase (SPase) gene from Leuconostoc mesenteroides ATCC 12291 was synthesised after codon optimization, and inserted into pET-28a plasmid to generate pET-28a-spase. The recombinant strain Escherichia coli BL21 (DE3)/pET-28a-spase was induced for Spase expression. The recombinant protein Spase was purified and characterized. The specific enzyme activity of SPase was 213.98 U/mg, the purification ratio was 1.47-fold, and the enzyme activity recovery rate was 87.80%. The optimal temperature and the optimal pH of the SPase were identified to be 45 °C and 6.5 respectively, and Km, Vmax and kcat of the SPase for sucrose was 128.8 mmol/L, 2.167 μmol/(mL·min), and 39 237.86 min-1. The recombinant SPase was used for α-arbutin production from hydroquinone and the reaction process was evaluated. The optimal conditions for synthesis of α-arbutin by SPase were 40 g/L hydroquinone, 5:1 molar ratio of sucrose and hydroquinone, and 250 U/mL recombinant SPase at pH 7.0 and 30 °C for 24 h in the dark, and then 500 U/mL glucoamylase was added at 40°C for 2.5 h. Under the optimized process, the yield of α-arbutin reached 98 g/L, and the hydroquinone conversion rate was close to 99%. In summary, the recombinant SPase was cloned and characterized, and its application for α-arbutin production was feasible.

[Expression, purification and characterization of catalase from Corynebacterium glutamicum]

Catalase catalyzes the decomposition of H₂O₂ to H₂O and O₂, and has a wide range of industrial applications. However, most catalases used in the textile and paper industries are often subjected to high-alkaline challenges which makes it necessary to develop alkaline catalase. In this study, a catalase from Corynebacterium glutamicum was expressed in Escherichia coli, and the expression conditions were optimized. The recombinant catalase was purified by Ni-chelating affinity chromatography, and the recombinant enzyme was characterized. The optimal conditions of producing the recombinant catalase were: an IPTG concentration of 0.2 mmol/L, a culturing temperature of 25 °C and a culturing time of 11 h. The purified catalase had a specific activity of 55 266 U/mg, and it had a high activity in the pH range of 4.0 to11.5, with the highest activity at pH 11.0. When treated in pH 11.0 for 3 h, the enzyme retained 93% of its activity, indicating that the enzyme was qualified with a favorable stability under high-alkaline condition. The recombinant catalase had maximal activity at 30 °C, and showed a satisfactory thermal stability at a range of 25 °C to 50 °C. The apparent Km and Vmax values of purified catalase were 25.89 mmol/L and 185.18 mmol/(minmg), respectively. Besides, different inhibitors, such as sodium dodecyl sulfate (SDS), urea, NaN₂, β-mercaptoethanol, and EDTA had different degrees of inhibition on enzyme activity. The catalase from C. glutamicum shows high catalytic efficiency and high alkaline stability, suggesting its potential utilization in industrial production.

Heterologous Expression of Recombinant Transglutaminase in Bacillus subtilis SCK6 with Optimized Signal Peptide and Codon, and Its Impact on Gelatin Properties

Microbial transglutaminases (MTGs) are widely used in the food industry. In this study, the MTG gene of Streptomyces sp. TYQ1024 was cloned and expressed in a food-grade bacterial strain, Bacillus subtilis SCK6. Extracellular activity of the MTG after codon and signal peptide (SP Ync M) optimization was 20 times that of the pre-optimized enzyme. After purification, the molecular weight of the MTG was 38 kDa and the specific activity was 63.75 U/mg. The optimal temperature and pH for the recombinant MTG activity were 50°C and 8.0, respectively. MTG activity increased 1.42- fold in the presence of β-ME and 1.6-fold in the presence of DTT. Moreover, 18% sodium chloride still resulted in 83% enzyme activity, which showed good salt tolerance. Cross-linking gelatin with the MTG increased the strength of gelatin 1.67 times and increased the thermal denaturation temperature from 61.8 to 75.8°C. The MTG also significantly increased the strength and thermal stability of gelatin. These characteristics demonstrated the huge commercial potential of MTG, such as for applications in salted protein foods.

Encapsulation of Mannose-6-phosphate Isomerase in Yeast Spores and Its Application in l-Ribose Production

A mannose-6-phosphate isomerase (MPI) from Geobacillus thermodenitrificans was expressed and successfully encapsulated into the Saccharomyces cerevisiae spores. Our results demonstrated that compared to the free enzyme, the MPI triple mutant encapsulated in osw2Δ spores exhibited much preferred enzymatic properties, such as enhanced catalytic activity, excellent reusability, thermostability, and tolerance to various harsh conditions. In combination with an l-arabinose isomerase (AI) also from G. thermodenitrificans, this technique of spore encapsulation was applied for producing a high-value rare sugar l-ribose from biomass-derived l-arabinose. Using a 10 mL reaction system, 350 mg of l-ribose was produced from 1 g of l-arabinose with a conversion yield of 35% by repeatedly reacting with 200 mg of AI-encapsulated spores and 300 mg of MPI-encapsulated spores. This study provides a very useful and concise approach for the synthesis of rare sugars and other useful compounds.

Regulation of Exopolysaccharide Production by ProE, a Cyclic-Di-GMP Phosphodiesterase in Pseudomonas aeruginosa PAO1

The ubiquitous second messenger c-di-GMP is involved in regulation of multiple biological functions including the important extracellular matrix exopolysaccharides (EPS). But how c-di-GMP metabolic proteins influence EPS and their enzymatic properties are not fully understood. Here we showed that deletion of proE, which encodes a protein with GGDEF-EAL hybrid domains, significantly increased the transcriptional expression of the genes encoding EPS production in Pseudomonas aeruginosa PAO1 and changed the bacterial colony morphology. Our data showed that ProE is a very active phosphodiesterase (PDE), with a high enzyme activity in degradation of c-di-GMP. Interestingly, the optimal activity of ProE was found in the presence of Co²⁺, unlike other PDEs that commonly rely on Mg²⁺ or Mn²⁺ for best performance. Furthermore, we identified three widely conserved novel residues that are critical for the function of ProE through site-directed mutagenesis. Subsequent study showed that ProE, together with other three key PDEs, i.e., RbdA, BifA, and DipA regulate the EPS production in P. aeruginosa PAO1. Moreover, by using the GFP-fusion approach, we observed that these four EPS associated-PDEs showed a polar localization pattern in general. Taken together, our data unveil the molecular mechanisms of ProE in regulation of EPS production, and provide a new insight on its enzymatic properties in degradation of c-di-GMP.

Purification and properties of a laccase from the mushroom Agaricus sinodeliciosus

A homogeneous monomeric laccase (ASL) from Agaricus sinodeliciosus, with a molecular mass of 65 kDa, was isolated using ion-exchange chromatography (CM-cellulose and Q-Sepharose) and gel-filtration chromatography (Superdex 75). This laccase exhibited maximum activity at 50 °C and pH 5.0. Hg²⁺ and Cd²⁺ significantly inhibited its activity. The laccase displayed a K_m value of 0.9 mM toward 2,2'-azinobis-(3-ethylbenzthiazoline-6-sulfonate) (ABTS). In addition to ABTS, ASL exhibited higher affinity toward o-toluidine and benzidine than other substrates. ASL is able to decolorize malachite green and Eriochrome black T.

Two Highly Similar Chitinases from Marine Vibrio Species have Different Enzymatic Properties

Chitinase, as one of the most important extracellular enzymes in the marine environment, has great ecological and applied values. In this study, two chitinases (Chi1557 and Chi4668) with 97.33% amino acid sequences identity were individually found in Vibrio rotiferianus and Vibrio harveyi. They both were encoding by 561 amino acids, but differed in 15 amino acids and showed different enzymatic properties. The optimal temperature and pH ranges were 45-50 °C and pH 5.0-7.0 for Chi1557, while ~50 °C and pH 3.0-6.0 for Chi4668. K+, Mg2+, and EDTA increased the enzymatic activity of Chi4668 significantly, yet these factors were inhibitory to Chi1557. Moreover, Chi1557 degraded colloidal chitin to produce (GlcNAc)2 and minor GlcNAc, whereas Chi4668 produce (GlcNAc)2 with minor (GlcNAc)3 and (GlcNAc)4. The Kcat/Km of Chi4668 was ~4.7 times higher than that of Chi1557, indicating that Chi4668 had stronger catalytic activity than Chi1557. Furthermore, site-directed mutagenesis was performed on Chi1557 focusing on seven conserved amino acid residues of family GH18 chitinases. Chi1557 was almost completely inactive after Glu154, Gln219, Tyr221, or Trp312 was individually mutated, retained ~50% activity after Tyr37 was mutated, and increased two times activity after Asp152 was mutated, indicating that these six amino acids were key sites for Chi1557.

Effects of Substrate-Binding Site Residues on the Biochemical Properties of a Tau Class Glutathione S-Transferase from Oryza sativa

Glutathione S-transferases (GSTs)—an especially plant-specific tau class of GSTs—are key enzymes involved in biotic and abiotic stress responses. To improve the stress resistance of crops via the genetic modification of GSTs, we predicted the amino acids present in the GSH binding site (G-site) and hydrophobic substrate-binding site (H-site) of OsGSTU17, a tau class GST in rice. We then examined the enzyme activity, substrate specificity, enzyme kinetics and thermodynamic stability of the mutant enzymes. Our results showed that the hydrogen bonds between Lys42, Val56, Glu68, and Ser69 of the G-site and glutathione were essential for enzyme activity and thermal stability. The hydrophobic side chains of amino acids of the H-site contributed to enzyme activity toward 4-nitrobenzyl chloride but had an inhibitory effect on enzyme activity toward 1-chloro-2,4-dinitrobenzene and cumene hydroperoxide. Different amino acids of the H-site had different effects on enzyme activity toward a different substrate, 7-chloro-4-nitrobenzo-2-oxa-1,3-diazole. Moreover, Leu112 and Phe162 were found to inhibit the catalytic efficiency of OsGSTU17 to 7-chloro-4-nitrobenzo-2-oxa-1,3-diazole, while Pro16, Leu112, and Trp165 contributed to structural stability. The results of this research enhance the understanding of the relationship between the structure and function of tau class GSTs to improve the abiotic stress resistance of crops.

[Expression and characterization of a multicopper oxidase from Lactobacillus fermentum]

Biogenic amines (BAs) are low molecular weight organic compounds that present in fermented foods. Large amount of ingested biogenic amines can cause allergy or significant symptoms. Reduction of BAs by enzymatic reaction in fermented foods is one of the most efficient methods for removal of biohazard compounds and assurance food safety. In this study, the multicopper oxidase (MCO) gene in the genome of Lactobacillus fermentum was successfully cloned in Escherichia coli BL21 and expressed at 484 U/L. The recombinant MCO was purified by the immobilized metal affinity chromatography method. The optimal reaction temperature and pH for this enzyme was detected to be 50 °C and 3.5. The Km and Vmax values of the recombinant MCO was determined to be 1.30 mmol/L and 7.67×10⁻² mmol/(L·min). Moreover, this MCO dramatically degrades histamine and tyramine by 51.6% and 40.9%, and can degrade other BAs including tryptamine, phenylethylamine, putrescine, cadaverine and spermidine, and was found to be tolerant to 18% (W/V) NaCl. The recombinant MCO is also capable of degrading BAs in soy sauce. The degradation rate of total BAs in soy sauce reaches 10.6% though a relatively low level of enzyme (500 U/L) is used. Multicopper oxidase has the potential to degrade biogenic amines in fermented foods, which lays a foundation for the further application of this kind of food enzymes.

Production of l-Ribulose Using an Encapsulated l-Arabinose Isomerase in Yeast Spores

The rare sugar l-ribulose is produced from the abundant sugar l-arabinose by enzymatic conversion. An l-arabinose isomerase (AI) from Geobacillus thermodenitrificans was efficiently expressed and encapsulated in Saccharomyces cerevisiae spores. Deletion of the yeast OSW2 gene, which causes a mild defect in the integrity of the spore wall, substantially improved the activity of encapsulated AI, without damaging its superior enzymatic properties of thermostability, pH tolerance,and resistance toward SDS and proteinase treatments. In a 10 mL reaction, 100 mg of dry AI encapsulated in spores produced 250 mg of l-ribulose from 1 g of l-arabinose, indicating a 25% conversion rate. Notably, the product of l-ribulose was directly purified from the reaction solution with an approximately 91% recovery using a Ca²⁺ ion exchange column. Our results describe not only a facile approach for the production of l-ribulose but also a useful strategy for the enzymatic conversion of rare sugars in "Izumoring".

[Heterologous expression and characterization of Aspergillus oryzae acidic protease in Pichia pastoris]

Acid protease, an important aspartic protease, has been widely used in food, pharmaceutical and tanning industries. To promote the research and application of acid protease, an acid protease gene (pepA) from Aspergillus oryzae was obtained from fermented soy based on metagenome sequencing, and then cloned and transformed into Pichia pastoris GS115 for heterologous expression. The characteristic of recombinant PepA was also investigated. The activity of acid protease in the culture supernatant of P. pastoris was 50.62 U/mL. The molecular mass of PepA was about 50 kDa, and almost no other proteins in the supernatant were observed, as shown by SDS-PAGE. The optimum pH and temperature of PepA were determined as pH 4.5 and 50 ℃. Mn²⁺ and Cu²⁺ enhanced the activity of PepA, whereas Fe³⁺, Fe²⁺ and Ca² had inhibitory effects on its activity. The above findings can provide guidance for heterologous expression and industrial application of acid protease from Aspergillus oryzae.

Expression, Purification and Characterization of Chondroitinase AC II from Marine Bacterium Arthrobacter sp. CS01

Chondroitinase (ChSase), a type of glycosaminoglycan (GAG) lyase, can degrade chondroitin sulfate (CS) to unsaturate oligosaccharides, with various functional activities. In this study, ChSase AC II from a newly isolated marine bacterium Arthrobacter sp. CS01 was cloned, expressed in Pichia pastoris X33, purified, and characterized. ChSase AC II, with a molecular weight of approximately 100 kDa and a specific activity of 18.7 U/mg, showed the highest activity at 37 °C and pH 6.5 and maintained stability at a broad range of pH (5–7.5) and temperature (below 35 °C). The enzyme activity was increased in the presence of Mn²⁺ and was strongly inhibited by Hg²⁺. Moreover, the kinetic parameters of ChSase AC II against CS-A, CS-C, and HA were determined. TLC and ESI-MS analysis of the degradation products indicated that ChSase AC II displayed an exolytic action mode and completely hydrolyzed three substrates into oligosaccharides with low degrees of polymerization (DPs). All these features make ChSase AC II a promising candidate for the full use of GAG to produce oligosaccharides.

Characterization and Exploration of Recombinant Wheat Catalase for Improvement of Wheat-Flour-Processing Quality

The wheat catalase gene ( wcat1) was cloned and overexpressed in Pichia pastoris. The purified wCat1 exhibits its highest activity at pH 7.5 and 35 °C with K_m and V_max of 22.95 mM and 0.24 μmol/min, respectively. wCat1 could markedly improve the farinographic properties of dough, with the stability time increasing and degree of softening decreasing, and enhance the rheological properties of dough. wCat1 could also elevate bread-making quality, with increased specific volume of the bread and decreased hardness, gumminess, and chewiness, which are attributable to increased amounts of SDS-insoluble protein in dough, resulting in extended glutenin networks and thus larger pores in the fermented dough and bread crumb. The decrease of hydrogen peroxide and increase of free thiol groups in wCat1-treated dough suggest that the decomposition of hydrogen peroxide by wCat1 likely promotes disulfide-bond formation and thus the cross-linking of dough proteins.