Microorganisms are omnipresent in all environments and play mainly the role of transformers, thanks to the multiple enzymes they are able to produce. In order to valorize fermented foods in the Republic of the Congo, ...Microorganisms are omnipresent in all environments and play mainly the role of transformers, thanks to the multiple enzymes they are able to produce. In order to valorize fermented foods in the Republic of the Congo, this work aimed to characterize and study some properties of microorganisms isolated from samples of peppers sold in three markets of Brazzaville. A numeration of the total aerobic mesophilic flora (TAMF) was made in a solid medium, allowing the evaluation of each sample’s microbial concentration. The microbial mass varied from 2.8 × 105 CFU/g for the Ouénzé sample to 1.8 × 104 CFU/g for the Total sample and 2 × 104 CFU/g for the Moungali market sample. The evaluation of the enzymatic properties of the Bacillus isolates showed that 68.42% were capable of producing cellulases and 78.94% were capable of producing amylases and proteases. Antimicrobial activities revealed that 63.15% of the isolates were able to secrete inhibitory substances against E. coli and Staphylococcus aureus. Molecular analysis by PCR amplification, sequencing of the 16S rRNA gene and BLAST bioinformatics analysis provides newly identified bacteria strains with new accession numbers in GenBank: Bacillus thuringiensis MBCBR322 (OP474008), Bacillus megaterium MBCBJ1822 (OP476493), Bacillus thuringiensis MBCBR222 (OP476494), Priestia megaterium MBCBJ2022 (OP476495) and Lactobacillus paraplantarum MBCBR1522 (OP476496). Multiple sequences alignment of identified sequences with their homologs of GenBank has shown high similarities. The phylogenetic inference assay has provided the two groups of strains observed in this study, and the two groups are very coherent with the phylogeny of the reference.展开更多
Plasticized poly(L-lactide)(PLLA) materials have been applied in many fields and the microstructure performance of such materials attracts much attention of researchers. However, few reports declared the hydrolytic de...Plasticized poly(L-lactide)(PLLA) materials have been applied in many fields and the microstructure performance of such materials attracts much attention of researchers. However, few reports declared the hydrolytic degradation ability of the plasticized PLLA materials. In this article, a small quantity of poly(ethylene glycol)(PEG) was introduced into PLLA, which aimed to understand the hydrolytic degradation behavior of the plasticized PLLA materials. The microstructures of the plasticized samples were comparatively investigated using scanning electron microscopy(SEM), wide angle X-ray diffraction(WAXD), differential scanning calorimetry(DSC) and Flourier transform infrared spectroscopy(FTIR), etc. The results demonstrated that PEG improved the hydrophilicity of sample surface, and the relatively high content of PEG enhanced the crystallization ability of PLLA matrix. The hydrolytic degradation measurement was carried out at 60 ℃ in an alkaline solution of pH = 12. The results demonstrated that the plasticized PLLA samples exhibited accelerated hydrolytic degradation compared with the pure PLLA sample, and the hydrolytic degradation was also dependent on the PEG content. Further results demonstrated that PEG induced the change of hydrolytic degradation mechanism possibly due to the good dissolution ability of PEG in water, which provided more paths for the penetration of water. Furthermore, the microstructure evolution of the plasticized PLLA during the hydrolytic degradation process was also investigated, and the results demonstrated the occurrence of PLLA crystallization, which was possibly contributed to the decreased hydrolytic degradation rate observed at relatively long hydrolytic degradation time. This work is of great significance and may open a new way for promoting the reclamation of PLLA waste material.展开更多
The effects of La on some hydrolytic enzyme activities in red soil were studied in incubation and pot culture experiments. In the incubation experiment, La slightly stimulates the activities of urease and acidic phosp...The effects of La on some hydrolytic enzyme activities in red soil were studied in incubation and pot culture experiments. In the incubation experiment, La slightly stimulates the activities of urease and acidic phosphatase in soil and strongly stimulates sucrase activity in soil. In the pot culture experiment, La stimulates the activities of urease, acidic phosphatase and sucrase to different degrees. The stimulative effects of rare earth elements (REE) on hydrolytic enzyme activities in soil may result in increasing yield of crops.展开更多
The effects of temperature and relative humidity on the hydrolytic degradation of poly（p-dioxanone）（PPDO） were investigated. The hydrolytic degradation behaviors were monitored by tracing the changes of water abso...The effects of temperature and relative humidity on the hydrolytic degradation of poly（p-dioxanone）（PPDO） were investigated. The hydrolytic degradation behaviors were monitored by tracing the changes of water absorption, mechanical and crystalline properties, molecular weight and its distribution, surface morphologies, as well as infrared absorption peaks and hydrogen chemical shifts during the degradation. It is found that the water absorption increases whilst the intrinsic viscosity, tensile strength and elongation at break decrease as the temperature or relative humidity increases. With degradation time growing, the molecular weight drops and its distribution broadens. The crystallinity of PPDO has a tendency to increase at first and then to decrease, while the crystalline structure is not significantly changed. At the same time, some cracks are observed on the surface and keep growing and deepening. All results show that temperature plays more significant roles than relative humidity during the degradation. The analyses of Fourier transform infrared spectroscopy and hydrogen nuclear magnetic resonance spectroscopy reveal that the degradation of PPDO is a predominant hydrolysis of ester linkages.展开更多
Lansoprazole degradation is accelerated in both acidic and basic medium in water. The present investigation deals with the hydrolytic degradation of Lansoprazole. Acidic medium degradation show all known impurities an...Lansoprazole degradation is accelerated in both acidic and basic medium in water. The present investigation deals with the hydrolytic degradation of Lansoprazole. Acidic medium degradation show all known impurities and degradation products whereas basic degradation studies show new impurity which has higher molecular weight than Lansoprazole. New impurity was identified, isolated using mass based auto purification system and characterised by 1H NMR, 13C NMR, HMBC, HSQC, NOE, COSY and HRMS experiments. Isolated impurity was showing molecular weight of 467.10, molecular formula of C23H16F3N5OS and its name is 7-(3-Methyl-4-(2,2,2-trifluoroethoxy) pyridin-2-yl)-7H-benzo[4,5]imidazo[2,1-b]benzo[4,5]imidazo[2,1-d][1,3,5]thiadiazine.展开更多
Poly(amidoamine) dendrimers-modified reduced graphene oxide nanosheets(PAMAM/rGO) composite was selected as a carrier of heterogeneous Ag0.3Co0.7nanoparticles in order to obtain an excellent catalyst for ammonia boran...Poly(amidoamine) dendrimers-modified reduced graphene oxide nanosheets(PAMAM/rGO) composite was selected as a carrier of heterogeneous Ag0.3Co0.7nanoparticles in order to obtain an excellent catalyst for ammonia borane(AB) hydrolysis. During the synthetic processes, GO could easily assembled with PAMAM by the electrostatic and hydrogen-bonding interactions. Structural characterization revealed that Ag0.3Co0.7bimetallic nanoparticles with uniform size distribution of 5 nm are well dispersed on PAMAM/rGO composite architecture. Ag0.3Co0.7@PAMAM/rGO was found to be a highly active and reusable catalyst in hydrogen generation from the hydrolysis of AB with a turnover frequency value(TOF) of 19.79 molH2min-1molM-1at 25.0±0.1℃ and retained 75.4% of their initial activity with a complete release of hydrogen in five runs. The relatively high TOF value and low apparent activation energy(34.21 kJ mol-1) make these Ag0.3Co0.7@PAMAM/rGO NPs as a high-efficient catalyst for catalytic dehydrogenation of AB facilitating the development of practically applicable energy storage materials.展开更多
The selective precipitation of zinc from zinc-nickel sulfate solution with the Zn/Ni molar ratio of20:1was studied.Dropwise addition of0.5mol/L NaOH solution into the zinc-nickel sulfate solution containing0,0.01,0.02...The selective precipitation of zinc from zinc-nickel sulfate solution with the Zn/Ni molar ratio of20:1was studied.Dropwise addition of0.5mol/L NaOH solution into the zinc-nickel sulfate solution containing0,0.01,0.02,0.03and0.04mol/L ethylene diamine tetraacetate(EDTA)as a chelating agent was done.The equilibrium analysis of precipitation pathway was performed using Visual MINTEQ program.The equilibrium analysis showed that the presence of small amounts of EDTA can prevent nickel precipitation in alkaline conditions without any negative effect on zinc precipitation.On this basis,more than90%of zinc could be precipitated as a product with about50%Zn and only0.11%Ni at pH=9.0merely as a result of the presence of0.03mol/L EDTA in the solution.The stirring time of120min after precipitation was found to be essential for more complete separation.The X-ray diffraction studies on the precipitate revealed that the precipitated phase was Zn4(OH)6SO4.4H2O.展开更多
Zinc(II) complexes of new macrocyclic tetraamines (cyclam derivatives) having a strategically appended phenolate group, have ben examined as catalyst for the hyd rolysis of 4nitrophenyl acetate(NA). It ovas proven th...Zinc(II) complexes of new macrocyclic tetraamines (cyclam derivatives) having a strategically appended phenolate group, have ben examined as catalyst for the hyd rolysis of 4nitrophenyl acetate(NA). It ovas proven that coordinated phenolate can serve as a good nucleophile that efficiently catalyze 4-nitrophenyl acetate(NA) hydrolysis.展开更多
A tung oil-based boron-nitrogen coordination polymer(TWE-BN)was specially designed and synthesized as a highly efficient water-based lubricant additive,which has been beneficial to both energy conservation and conduci...A tung oil-based boron-nitrogen coordination polymer(TWE-BN)was specially designed and synthesized as a highly efficient water-based lubricant additive,which has been beneficial to both energy conservation and conducive to environmental protection.Its hydrolysis stability and tribological properties in water were investigated.To better research the lubricating properties,and thus to understand the interaction between the surface and the lubricating additives.Herein,both experimental and theoretical computations based on density functional theory(DFT)were performed.The addition of TWE-BN reduces the water friction coefficient and wear scar diameter,and the maximum non-seizure load increased from 93 to 726 N.Moreover,the anti-corrosion ability on copper was classified as 1b level.The stainless-steel surface was analyzed using scanning electron microscopy(SEM)and X-ray photoelectron spectroscopy(XPS).In hydrolytic stability testing,TWE-BN was better than nitrogen-free tung oil-based lubricant additive(TWE-B)and remained non-hydrolyzed for at least 15 days,implying the feasibility of tung oil-based boron-nitrogen coordination as highly effective and hydrolytic stability lubricant additives.展开更多
In this study,the hydrolytic amino acids of Chinese human and Holstein cow milk of different lactation periods were analyzed by the advanced isobaric tags for relative and absolute quantitation(iTRAQ)combined with the...In this study,the hydrolytic amino acids of Chinese human and Holstein cow milk of different lactation periods were analyzed by the advanced isobaric tags for relative and absolute quantitation(iTRAQ)combined with the high performance liquid chromatography-mass spectrometry(HPLC-MS/MS)approach.The total contents of the hydrolytic amino acids in cow colostrum,cow mature milk,human colostrum and human mature milk were 5.00,4.38,2.12 and 2.48 g·L^(-1),respectively.Among these,the contents of the hydrolytic amino acids in cow milk were higher than those in human milk,indicating a decreasing trend with the prolongation of lactation.Additionally,principal component and hierarchical cluster analyses were used to further screen the differentially expressed amino acids.These results enhanced the understanding of the hydrolytic amino acids in cow and human milk across different lactation periods,which could provide potential directions for newborn dairy powder and nutritious supplementary.展开更多
Sponges (Phylum: Porifera) is one of the major groups in the Lakshadweep coral reefs. These sponges harbor diverse bacteria with metabolic potentiality. From biodiversity to biotechnological prospecting, scientific in...Sponges (Phylum: Porifera) is one of the major groups in the Lakshadweep coral reefs. These sponges harbor diverse bacteria with metabolic potentiality. From biodiversity to biotechnological prospecting, scientific investigations related to sponge associated microorganisms have expanded, but remain rather limited to few geographic locations. In this study, culturable bacteria associated with two demosponges viz Dysidea granulosa, Sigmadocia fibulata and the ambient water were screened for commercially important enzymes such as amylase, protease, gelatinase, lipase, deoxyribonucleic, phosphatase and urease. Amylase and phosphatase were the predominant enzymes produced by >80% of sponge-associated bacteria compared to the ambient water. Nearly 50% of the sponge-associated bacteria expressed multiple enzymatic activities (> 4) with variation in the percentage of expression of individual enzymes. More than 65% of the culturable heterotrophic bacteria associated with sponges were Gammaproteobacteria. The order Vibrionales was the main source for multiple enzyme production. Sponge associated bacteria formed more closely related clusters than the water isolates based upon their activity pattern. High recovery of sponge-associated bacteria with multiple enzymatic activities suggest that these versatile bacteria are yet unexploited potential for bioprospecting.展开更多
It is well known that fossil fuels are one of the major pollutants that contribute to climate change and there is a need to develop alternatives to their uses.One option is the use of a renewable fuel such as biogas o...It is well known that fossil fuels are one of the major pollutants that contribute to climate change and there is a need to develop alternatives to their uses.One option is the use of a renewable fuel such as biogas obtained from the breaking down of organic matter in the anaerobic digestion process.When biogas is cleaned up to a certain quality,it can substitute the use of natural gas.However,this slow process requires optimization to increase the amount of gas.There are chemical,physical and biological treatments for organic matter to increase the amount and quality of biogas.In the former research,a biological treatment was tested by adding a selection of microorganisms that showed hydrolytic activity to an anaerobic digester for its optimization.First,a selection of microorganisms with the ability to grow in fresh sewage sludge as only nutrient was selected.Then,the lipolytic,cellulolytic and PA(Proteolytic Activity)of microorganisms was tested using selective growth media.Finally,10 samples with the greatest hydrolytic activity were used to evaluate their effects in the increasing of biogas production in the anaerobic process.The results showed that 83%of the microorganisms with the ability to grow in sewage sludge were proteolytic,while the percentage of lipolytic and cellulolytic microorganisms was smaller.Furthermore,it was found that proteolytic microorganisms are the ones that increase biogas yield in a maximum of 80%with a COD(Chemical Oxygen Demand)reduction of 58%.展开更多
A new metallomicelle, formed by Cu2+ Or Zn2+ ion and N-tetradecyl-2-(N-2-hydroxyethyl aminomethyl) imidazol in the presence of cetyltrimethylammonium bromide, was found to possess remarkable catalytic activity to the ...A new metallomicelle, formed by Cu2+ Or Zn2+ ion and N-tetradecyl-2-(N-2-hydroxyethyl aminomethyl) imidazol in the presence of cetyltrimethylammonium bromide, was found to possess remarkable catalytic activity to the hydrolysis of p-nitrophenyl picolinate.展开更多
The reaction of bis-[2-amino-4-pheny1-5-thiazolyl] disulfide with 5-nitro-salicylaldehyde in absolute ethanol resulted in the formation of a new Schiff base ligand H<sub>2</sub>L (1). Characterization of t...The reaction of bis-[2-amino-4-pheny1-5-thiazolyl] disulfide with 5-nitro-salicylaldehyde in absolute ethanol resulted in the formation of a new Schiff base ligand H<sub>2</sub>L (1). Characterization of the ligand was performed by FT-IR, <sup>1</sup>H NMR, <sup>13</sup>C NMR, UV-Vis, elemental analysis and single crystal X-ray diffraction. The ligand, (1), possesses a disulfide –S–S– bridge of 2.1121 (3) ? length, and the molecule adopts a cis-conformation around this bond. In the crystal structure of (1), an intramolecular O–H···N hydrogen bond with D… A distance of 2.69 (3) ? was present. The reaction of (1) with Co(NO<sub>3</sub>)<sub>2</sub>·6H<sub>2</sub>O and CuCl<sub>2</sub>·2H<sub>2</sub>O in methanol afforded the corresponding metal complexes. The obtained solids were further investigated by elemental analysis and UV-Vis titration that confirmed the formation of [CoL] and [ClCuHL] complexes. However, recrystallizaion of the Co(II) complex in dimethylsulfoxide caused the complete hydrolysis of the imine bond and afforded a Co(II) complex in which two 5-nitro-salicylaldehyde and two DMSO molecules were coordinated to the central metal in an octahedral fashion. This structure (2) was also confirmed by single crystal X-ray analysis.展开更多
Green tea catechins are classified as (-)-epi-forms (2R, 3R) or (-)-forms (2S, 3R) with respect to stereoisomerism. The (-)-forms (2S, 3R) in catechin preparations obtained from green tea amounts to approximately 10% ...Green tea catechins are classified as (-)-epi-forms (2R, 3R) or (-)-forms (2S, 3R) with respect to stereoisomerism. The (-)-forms (2S, 3R) in catechin preparations obtained from green tea amounts to approximately 10% of total catechins, whereas the other 90% are (-)-epiforms (2R, 3R). High temperature induces the conversion of (-)-epiforms (2R, 3R) to (-)-forms (2S, 3R). This study investigated the effect of catechin prepa-rations containing 10, 20 and 30% (-)-forms (2S, 3R) on the oxidative and hydrolytic stability of butter. For comparison, butter with δ-tocopherol and BHT and butter without stabilizer were analysed. Butter stability was examined under conditions of refrigeration (8 oC) and freezing (-22 oC) and at temperature of 50 oC and 100 oC. Catechin preparations were more efficient butter stabilizers than BHT and δ-tocopherol. Thermal modification of catechins that led to the genera-tion of 20% of (-) forms (2S, 3R) improved their antioxidative efficacy, but longer treatment lead- ing to the formation of 30% of (-) forms (2S, 3R) decreased their antioxidative activity. The hy-drolytic stability of butter, however, increased as the amount of (-) forms (2S, 3R) increased.展开更多
This paper evaluates the thermodynamic possibility of coalbed methane formation as a result of direct reaction of coal and water during the process of hydrolytic disproportionation of carbon(HDC).Some examples of expe...This paper evaluates the thermodynamic possibility of coalbed methane formation as a result of direct reaction of coal and water during the process of hydrolytic disproportionation of carbon(HDC).Some examples of experimental and natural evidences of HDC are discussed.展开更多
Enzymes fold into three-dimensional structures for spatial arrangement of amino acid residues and formation of specific motifs within their active sites,enabling their remarkable catalytic properties.Replicating such ...Enzymes fold into three-dimensional structures for spatial arrangement of amino acid residues and formation of specific motifs within their active sites,enabling their remarkable catalytic properties.Replicating such intricate folding and functional group distribution in synthetic systems could allow for efficient and mild catalysis with significant potential in green chemistry,but achieving this remains a major challenge.Inspired by structure and function of oxyanion hole-a fundamental structural feature in hydrolases,we designed a surfactant system comprising an aza-crown ether core and an alkyl tail,which self-assembles into tail-totail bilayer nanostructures capable of catalyzing hydrolytic reactions.The theoretical and experimental results reveal that the alkyl chain enhances the protonation and organization of the aza-crown ether,promoting ester substrate access and stabilizing the transition state,reminiscent of natural oxyanion hole mechanisms.It is observed that the alkylated aza-crown ether exhibits a 43.3-fold increase in catalytic efficiency(k_(cat)/K_(m))compared to its non-alkylated counterpart.Additionally,the self-assembled alkylated aza-crown ether demonstrates efficient CO_(2) hydration activity,resembling the function of carbonic anhydrase.This work offers a model for how simple molecules can evolve sophisticated catalysts through structural and functional optimization,offering new insights for the design of bioinspired catalyst in green chemistry.展开更多
Mimetic enzymes are devised as alternates or supplements of natural enzymes in broad fields but regulating their activities in a switchable manner remains challenging.Herein,we proposed an enzymatic self-assembly/disa...Mimetic enzymes are devised as alternates or supplements of natural enzymes in broad fields but regulating their activities in a switchable manner remains challenging.Herein,we proposed an enzymatic self-assembly/disassembly strategy to address this issue.A peptide molecule Nap FFEYIH(YH) was rationally designed which,after self-assembling into nanofibers,lined up the histidine moieties to form active hydrolysis centers for mimicking hydrolase activity.Enzymatic dephosphorylation of Nap FFEYp IH(Yp H) by alkaline phosphatase to yield YH also turned “ON” the hydrolase activity.In turn,phosphorylation of YH by phosphokinase epidermal growth factor receptor to yield Yp H disassembled the nanofibers and thus turned the activity “OFF”.As such,the “ON”/“OFF” of the mimetic hydrolase activities could be regulated under physiological conditions through ALP/EGFR-mediated self-assembly/disassembly of histidine nanofibers.This work provides a feasible strategy for the on-demand fabrication of artificial enzymes with controllable and superior activities.展开更多
Laminarin oligosaccharides(LOSs)with a specific degree of polymerization prepared through the laminarin degradation via laminarinase present more significant nutritional functions and application values.Human intestin...Laminarin oligosaccharides(LOSs)with a specific degree of polymerization prepared through the laminarin degradation via laminarinase present more significant nutritional functions and application values.Human intestinal bacteria are promising potential producers of novel carbohydrate-active enzymes with unique properties.Here,a novel glycoside hydrolase family 128(GH128)laminarinase OUC-BsLam26 from the intestinal bacterium Bacteroides sp.CBA7301 was heterologously expressed and characterized.The recombinant OUC-BsLam26 with a molecular mass of 49.86 kDa exhibits highest activity(6.60 U/mg)at 45℃ and pH 6.0,which shows noticeable temperature and pH stability.The purified OUC-BsLam26 could degrade laminarin via an endo-type mode with the generation of laminaripentaose,laminaritetraose,laminaritriose,and laminaribiose,among them,laminaritetraose is the principal product,which accounts for 45.25% of the total products,which is significantly different from the reported GH128 laminarinases.The minimum recognition substrate of OUC-BsLam26 is laminarihexaose.Furthermore,OUC-BsLam26 also could catalyze the transglycosylation process with the production of some novel glycosides.Altogether,the intestinal bacterium Bacteroides sp.CBA7301 contains laminarinase with unique product composition and OUC-BsLam26 is a hopeful bio-catalyst with the potential to produce laminaritetraose and some novel glycosides.展开更多
文摘Microorganisms are omnipresent in all environments and play mainly the role of transformers, thanks to the multiple enzymes they are able to produce. In order to valorize fermented foods in the Republic of the Congo, this work aimed to characterize and study some properties of microorganisms isolated from samples of peppers sold in three markets of Brazzaville. A numeration of the total aerobic mesophilic flora (TAMF) was made in a solid medium, allowing the evaluation of each sample’s microbial concentration. The microbial mass varied from 2.8 × 105 CFU/g for the Ouénzé sample to 1.8 × 104 CFU/g for the Total sample and 2 × 104 CFU/g for the Moungali market sample. The evaluation of the enzymatic properties of the Bacillus isolates showed that 68.42% were capable of producing cellulases and 78.94% were capable of producing amylases and proteases. Antimicrobial activities revealed that 63.15% of the isolates were able to secrete inhibitory substances against E. coli and Staphylococcus aureus. Molecular analysis by PCR amplification, sequencing of the 16S rRNA gene and BLAST bioinformatics analysis provides newly identified bacteria strains with new accession numbers in GenBank: Bacillus thuringiensis MBCBR322 (OP474008), Bacillus megaterium MBCBJ1822 (OP476493), Bacillus thuringiensis MBCBR222 (OP476494), Priestia megaterium MBCBJ2022 (OP476495) and Lactobacillus paraplantarum MBCBR1522 (OP476496). Multiple sequences alignment of identified sequences with their homologs of GenBank has shown high similarities. The phylogenetic inference assay has provided the two groups of strains observed in this study, and the two groups are very coherent with the phylogeny of the reference.
基金financially supported by the National Natural Science Foundation of China(No.51473137)
文摘Plasticized poly(L-lactide)(PLLA) materials have been applied in many fields and the microstructure performance of such materials attracts much attention of researchers. However, few reports declared the hydrolytic degradation ability of the plasticized PLLA materials. In this article, a small quantity of poly(ethylene glycol)(PEG) was introduced into PLLA, which aimed to understand the hydrolytic degradation behavior of the plasticized PLLA materials. The microstructures of the plasticized samples were comparatively investigated using scanning electron microscopy(SEM), wide angle X-ray diffraction(WAXD), differential scanning calorimetry(DSC) and Flourier transform infrared spectroscopy(FTIR), etc. The results demonstrated that PEG improved the hydrophilicity of sample surface, and the relatively high content of PEG enhanced the crystallization ability of PLLA matrix. The hydrolytic degradation measurement was carried out at 60 ℃ in an alkaline solution of pH = 12. The results demonstrated that the plasticized PLLA samples exhibited accelerated hydrolytic degradation compared with the pure PLLA sample, and the hydrolytic degradation was also dependent on the PEG content. Further results demonstrated that PEG induced the change of hydrolytic degradation mechanism possibly due to the good dissolution ability of PEG in water, which provided more paths for the penetration of water. Furthermore, the microstructure evolution of the plasticized PLLA during the hydrolytic degradation process was also investigated, and the results demonstrated the occurrence of PLLA crystallization, which was possibly contributed to the decreased hydrolytic degradation rate observed at relatively long hydrolytic degradation time. This work is of great significance and may open a new way for promoting the reclamation of PLLA waste material.
文摘The effects of La on some hydrolytic enzyme activities in red soil were studied in incubation and pot culture experiments. In the incubation experiment, La slightly stimulates the activities of urease and acidic phosphatase in soil and strongly stimulates sucrase activity in soil. In the pot culture experiment, La stimulates the activities of urease, acidic phosphatase and sucrase to different degrees. The stimulative effects of rare earth elements (REE) on hydrolytic enzyme activities in soil may result in increasing yield of crops.
基金financially supported by the National Natural Science Foundation of China(No.51121001)High-Tech Research&Development Program(No.2012AA062904)the Program for Changjiang Scholars and Innovative Research Teams in Universities of China(IRT 1026)
文摘The effects of temperature and relative humidity on the hydrolytic degradation of poly（p-dioxanone）（PPDO） were investigated. The hydrolytic degradation behaviors were monitored by tracing the changes of water absorption, mechanical and crystalline properties, molecular weight and its distribution, surface morphologies, as well as infrared absorption peaks and hydrogen chemical shifts during the degradation. It is found that the water absorption increases whilst the intrinsic viscosity, tensile strength and elongation at break decrease as the temperature or relative humidity increases. With degradation time growing, the molecular weight drops and its distribution broadens. The crystallinity of PPDO has a tendency to increase at first and then to decrease, while the crystalline structure is not significantly changed. At the same time, some cracks are observed on the surface and keep growing and deepening. All results show that temperature plays more significant roles than relative humidity during the degradation. The analyses of Fourier transform infrared spectroscopy and hydrogen nuclear magnetic resonance spectroscopy reveal that the degradation of PPDO is a predominant hydrolysis of ester linkages.
文摘Lansoprazole degradation is accelerated in both acidic and basic medium in water. The present investigation deals with the hydrolytic degradation of Lansoprazole. Acidic medium degradation show all known impurities and degradation products whereas basic degradation studies show new impurity which has higher molecular weight than Lansoprazole. New impurity was identified, isolated using mass based auto purification system and characterised by 1H NMR, 13C NMR, HMBC, HSQC, NOE, COSY and HRMS experiments. Isolated impurity was showing molecular weight of 467.10, molecular formula of C23H16F3N5OS and its name is 7-(3-Methyl-4-(2,2,2-trifluoroethoxy) pyridin-2-yl)-7H-benzo[4,5]imidazo[2,1-b]benzo[4,5]imidazo[2,1-d][1,3,5]thiadiazine.
基金financially supported by the National Natural Science Foundation of China(Nos.21303157 and 51571173)the Scientific Research Projects in Colleges and Universities in Hebei Province(No.QN2016002)the Innovation Fund for the Graduate Students of Hebei Province(No.2016SJBS018)
文摘Poly(amidoamine) dendrimers-modified reduced graphene oxide nanosheets(PAMAM/rGO) composite was selected as a carrier of heterogeneous Ag0.3Co0.7nanoparticles in order to obtain an excellent catalyst for ammonia borane(AB) hydrolysis. During the synthetic processes, GO could easily assembled with PAMAM by the electrostatic and hydrogen-bonding interactions. Structural characterization revealed that Ag0.3Co0.7bimetallic nanoparticles with uniform size distribution of 5 nm are well dispersed on PAMAM/rGO composite architecture. Ag0.3Co0.7@PAMAM/rGO was found to be a highly active and reusable catalyst in hydrogen generation from the hydrolysis of AB with a turnover frequency value(TOF) of 19.79 molH2min-1molM-1at 25.0±0.1℃ and retained 75.4% of their initial activity with a complete release of hydrogen in five runs. The relatively high TOF value and low apparent activation energy(34.21 kJ mol-1) make these Ag0.3Co0.7@PAMAM/rGO NPs as a high-efficient catalyst for catalytic dehydrogenation of AB facilitating the development of practically applicable energy storage materials.
文摘The selective precipitation of zinc from zinc-nickel sulfate solution with the Zn/Ni molar ratio of20:1was studied.Dropwise addition of0.5mol/L NaOH solution into the zinc-nickel sulfate solution containing0,0.01,0.02,0.03and0.04mol/L ethylene diamine tetraacetate(EDTA)as a chelating agent was done.The equilibrium analysis of precipitation pathway was performed using Visual MINTEQ program.The equilibrium analysis showed that the presence of small amounts of EDTA can prevent nickel precipitation in alkaline conditions without any negative effect on zinc precipitation.On this basis,more than90%of zinc could be precipitated as a product with about50%Zn and only0.11%Ni at pH=9.0merely as a result of the presence of0.03mol/L EDTA in the solution.The stirring time of120min after precipitation was found to be essential for more complete separation.The X-ray diffraction studies on the precipitate revealed that the precipitated phase was Zn4(OH)6SO4.4H2O.
文摘Zinc(II) complexes of new macrocyclic tetraamines (cyclam derivatives) having a strategically appended phenolate group, have ben examined as catalyst for the hyd rolysis of 4nitrophenyl acetate(NA). It ovas proven that coordinated phenolate can serve as a good nucleophile that efficiently catalyze 4-nitrophenyl acetate(NA) hydrolysis.
基金supported by Special Fund of Chinese Central Government for Basic Scientific Research Operations in Commonweal Research Institutes[No.CAFYBB2019SY037]and National Natural Science Foundation of China[No.31901260].
文摘A tung oil-based boron-nitrogen coordination polymer(TWE-BN)was specially designed and synthesized as a highly efficient water-based lubricant additive,which has been beneficial to both energy conservation and conducive to environmental protection.Its hydrolysis stability and tribological properties in water were investigated.To better research the lubricating properties,and thus to understand the interaction between the surface and the lubricating additives.Herein,both experimental and theoretical computations based on density functional theory(DFT)were performed.The addition of TWE-BN reduces the water friction coefficient and wear scar diameter,and the maximum non-seizure load increased from 93 to 726 N.Moreover,the anti-corrosion ability on copper was classified as 1b level.The stainless-steel surface was analyzed using scanning electron microscopy(SEM)and X-ray photoelectron spectroscopy(XPS).In hydrolytic stability testing,TWE-BN was better than nitrogen-free tung oil-based lubricant additive(TWE-B)and remained non-hydrolyzed for at least 15 days,implying the feasibility of tung oil-based boron-nitrogen coordination as highly effective and hydrolytic stability lubricant additives.
基金Supported by the National Key R&D Program of China(2018YFC1604302)the"Twelfth-Five Year"National Science and Technology Plan Project(2013BAD18B03)+2 种基金Shenyang Technological Innovation Project(Y17-0-028)Liaoning Revitalization Talents Program(XLYC1902083)Liaoning Distinguished Professor Project。
文摘In this study,the hydrolytic amino acids of Chinese human and Holstein cow milk of different lactation periods were analyzed by the advanced isobaric tags for relative and absolute quantitation(iTRAQ)combined with the high performance liquid chromatography-mass spectrometry(HPLC-MS/MS)approach.The total contents of the hydrolytic amino acids in cow colostrum,cow mature milk,human colostrum and human mature milk were 5.00,4.38,2.12 and 2.48 g·L^(-1),respectively.Among these,the contents of the hydrolytic amino acids in cow milk were higher than those in human milk,indicating a decreasing trend with the prolongation of lactation.Additionally,principal component and hierarchical cluster analyses were used to further screen the differentially expressed amino acids.These results enhanced the understanding of the hydrolytic amino acids in cow and human milk across different lactation periods,which could provide potential directions for newborn dairy powder and nutritious supplementary.
文摘Sponges (Phylum: Porifera) is one of the major groups in the Lakshadweep coral reefs. These sponges harbor diverse bacteria with metabolic potentiality. From biodiversity to biotechnological prospecting, scientific investigations related to sponge associated microorganisms have expanded, but remain rather limited to few geographic locations. In this study, culturable bacteria associated with two demosponges viz Dysidea granulosa, Sigmadocia fibulata and the ambient water were screened for commercially important enzymes such as amylase, protease, gelatinase, lipase, deoxyribonucleic, phosphatase and urease. Amylase and phosphatase were the predominant enzymes produced by >80% of sponge-associated bacteria compared to the ambient water. Nearly 50% of the sponge-associated bacteria expressed multiple enzymatic activities (> 4) with variation in the percentage of expression of individual enzymes. More than 65% of the culturable heterotrophic bacteria associated with sponges were Gammaproteobacteria. The order Vibrionales was the main source for multiple enzyme production. Sponge associated bacteria formed more closely related clusters than the water isolates based upon their activity pattern. High recovery of sponge-associated bacteria with multiple enzymatic activities suggest that these versatile bacteria are yet unexploited potential for bioprospecting.
文摘It is well known that fossil fuels are one of the major pollutants that contribute to climate change and there is a need to develop alternatives to their uses.One option is the use of a renewable fuel such as biogas obtained from the breaking down of organic matter in the anaerobic digestion process.When biogas is cleaned up to a certain quality,it can substitute the use of natural gas.However,this slow process requires optimization to increase the amount of gas.There are chemical,physical and biological treatments for organic matter to increase the amount and quality of biogas.In the former research,a biological treatment was tested by adding a selection of microorganisms that showed hydrolytic activity to an anaerobic digester for its optimization.First,a selection of microorganisms with the ability to grow in fresh sewage sludge as only nutrient was selected.Then,the lipolytic,cellulolytic and PA(Proteolytic Activity)of microorganisms was tested using selective growth media.Finally,10 samples with the greatest hydrolytic activity were used to evaluate their effects in the increasing of biogas production in the anaerobic process.The results showed that 83%of the microorganisms with the ability to grow in sewage sludge were proteolytic,while the percentage of lipolytic and cellulolytic microorganisms was smaller.Furthermore,it was found that proteolytic microorganisms are the ones that increase biogas yield in a maximum of 80%with a COD(Chemical Oxygen Demand)reduction of 58%.
文摘A new metallomicelle, formed by Cu2+ Or Zn2+ ion and N-tetradecyl-2-(N-2-hydroxyethyl aminomethyl) imidazol in the presence of cetyltrimethylammonium bromide, was found to possess remarkable catalytic activity to the hydrolysis of p-nitrophenyl picolinate.
文摘The reaction of bis-[2-amino-4-pheny1-5-thiazolyl] disulfide with 5-nitro-salicylaldehyde in absolute ethanol resulted in the formation of a new Schiff base ligand H<sub>2</sub>L (1). Characterization of the ligand was performed by FT-IR, <sup>1</sup>H NMR, <sup>13</sup>C NMR, UV-Vis, elemental analysis and single crystal X-ray diffraction. The ligand, (1), possesses a disulfide –S–S– bridge of 2.1121 (3) ? length, and the molecule adopts a cis-conformation around this bond. In the crystal structure of (1), an intramolecular O–H···N hydrogen bond with D… A distance of 2.69 (3) ? was present. The reaction of (1) with Co(NO<sub>3</sub>)<sub>2</sub>·6H<sub>2</sub>O and CuCl<sub>2</sub>·2H<sub>2</sub>O in methanol afforded the corresponding metal complexes. The obtained solids were further investigated by elemental analysis and UV-Vis titration that confirmed the formation of [CoL] and [ClCuHL] complexes. However, recrystallizaion of the Co(II) complex in dimethylsulfoxide caused the complete hydrolysis of the imine bond and afforded a Co(II) complex in which two 5-nitro-salicylaldehyde and two DMSO molecules were coordinated to the central metal in an octahedral fashion. This structure (2) was also confirmed by single crystal X-ray analysis.
文摘Green tea catechins are classified as (-)-epi-forms (2R, 3R) or (-)-forms (2S, 3R) with respect to stereoisomerism. The (-)-forms (2S, 3R) in catechin preparations obtained from green tea amounts to approximately 10% of total catechins, whereas the other 90% are (-)-epiforms (2R, 3R). High temperature induces the conversion of (-)-epiforms (2R, 3R) to (-)-forms (2S, 3R). This study investigated the effect of catechin prepa-rations containing 10, 20 and 30% (-)-forms (2S, 3R) on the oxidative and hydrolytic stability of butter. For comparison, butter with δ-tocopherol and BHT and butter without stabilizer were analysed. Butter stability was examined under conditions of refrigeration (8 oC) and freezing (-22 oC) and at temperature of 50 oC and 100 oC. Catechin preparations were more efficient butter stabilizers than BHT and δ-tocopherol. Thermal modification of catechins that led to the genera-tion of 20% of (-) forms (2S, 3R) improved their antioxidative efficacy, but longer treatment lead- ing to the formation of 30% of (-) forms (2S, 3R) decreased their antioxidative activity. The hy-drolytic stability of butter, however, increased as the amount of (-) forms (2S, 3R) increased.
文摘This paper evaluates the thermodynamic possibility of coalbed methane formation as a result of direct reaction of coal and water during the process of hydrolytic disproportionation of carbon(HDC).Some examples of experimental and natural evidences of HDC are discussed.
基金supported in part by the National Natural Science Foundation of China(No.52173194)the Beijing Natural Science Foundation(No.2232017)the Fundamental Research Funds for the Central Universities(No.buctrc201902).
文摘Enzymes fold into three-dimensional structures for spatial arrangement of amino acid residues and formation of specific motifs within their active sites,enabling their remarkable catalytic properties.Replicating such intricate folding and functional group distribution in synthetic systems could allow for efficient and mild catalysis with significant potential in green chemistry,but achieving this remains a major challenge.Inspired by structure and function of oxyanion hole-a fundamental structural feature in hydrolases,we designed a surfactant system comprising an aza-crown ether core and an alkyl tail,which self-assembles into tail-totail bilayer nanostructures capable of catalyzing hydrolytic reactions.The theoretical and experimental results reveal that the alkyl chain enhances the protonation and organization of the aza-crown ether,promoting ester substrate access and stabilizing the transition state,reminiscent of natural oxyanion hole mechanisms.It is observed that the alkylated aza-crown ether exhibits a 43.3-fold increase in catalytic efficiency(k_(cat)/K_(m))compared to its non-alkylated counterpart.Additionally,the self-assembled alkylated aza-crown ether demonstrates efficient CO_(2) hydration activity,resembling the function of carbonic anhydrase.This work offers a model for how simple molecules can evolve sophisticated catalysts through structural and functional optimization,offering new insights for the design of bioinspired catalyst in green chemistry.
基金supported by the National Natural Science Foundation of China (22234002,22204019,82172097)the Postgraduate Research&Practice Innovation Program of Jiangsu Province(KYCX22_0245)。
文摘Mimetic enzymes are devised as alternates or supplements of natural enzymes in broad fields but regulating their activities in a switchable manner remains challenging.Herein,we proposed an enzymatic self-assembly/disassembly strategy to address this issue.A peptide molecule Nap FFEYIH(YH) was rationally designed which,after self-assembling into nanofibers,lined up the histidine moieties to form active hydrolysis centers for mimicking hydrolase activity.Enzymatic dephosphorylation of Nap FFEYp IH(Yp H) by alkaline phosphatase to yield YH also turned “ON” the hydrolase activity.In turn,phosphorylation of YH by phosphokinase epidermal growth factor receptor to yield Yp H disassembled the nanofibers and thus turned the activity “OFF”.As such,the “ON”/“OFF” of the mimetic hydrolase activities could be regulated under physiological conditions through ALP/EGFR-mediated self-assembly/disassembly of histidine nanofibers.This work provides a feasible strategy for the on-demand fabrication of artificial enzymes with controllable and superior activities.
基金supported by the National Natural Science Foundation of China(32072159)Natural Science Foundation of Hainan Province(322QN338)+4 种基金Young Talent of Lifting Engineering for Science and Technology in Shandong,China(SDAST2021qt18)Qingdao Science and Technology Plan Key Research and Development Project(22-3-3-hygg-28-hy)Fundamental Research Funds for the Central Universities(202262003)Taishan Scholar Project of Shandong Province(tsqn202312099)Support Program for Youth Innovation Technology in Colleges and Universities of Shandong Province(2023KJ041)。
文摘Laminarin oligosaccharides(LOSs)with a specific degree of polymerization prepared through the laminarin degradation via laminarinase present more significant nutritional functions and application values.Human intestinal bacteria are promising potential producers of novel carbohydrate-active enzymes with unique properties.Here,a novel glycoside hydrolase family 128(GH128)laminarinase OUC-BsLam26 from the intestinal bacterium Bacteroides sp.CBA7301 was heterologously expressed and characterized.The recombinant OUC-BsLam26 with a molecular mass of 49.86 kDa exhibits highest activity(6.60 U/mg)at 45℃ and pH 6.0,which shows noticeable temperature and pH stability.The purified OUC-BsLam26 could degrade laminarin via an endo-type mode with the generation of laminaripentaose,laminaritetraose,laminaritriose,and laminaribiose,among them,laminaritetraose is the principal product,which accounts for 45.25% of the total products,which is significantly different from the reported GH128 laminarinases.The minimum recognition substrate of OUC-BsLam26 is laminarihexaose.Furthermore,OUC-BsLam26 also could catalyze the transglycosylation process with the production of some novel glycosides.Altogether,the intestinal bacterium Bacteroides sp.CBA7301 contains laminarinase with unique product composition and OUC-BsLam26 is a hopeful bio-catalyst with the potential to produce laminaritetraose and some novel glycosides.
