共查询到20条相似文献,搜索用时 15 毫秒
1.
Cohen R Persky L Hazan-Eitan Z Yarden O Hadar Y 《Applied biochemistry and biotechnology》2002,102(1-6):415-429
The white-rot fungus Pleurotus ostreatus produces two types of extracellular peroxidases: manganese-dependent peroxidase (MnP) and versatile peroxidase (VP). The
effect of Mn2+ on fungal growth, peroxidase activity profiles, and lignin degradation by P. ostreatus was studied in liquid culture and under solid-state fermentation conditions on perlite, the latter resembling the natural
growth conditions of this fungus. The fungus was grown in either a defined asparagine-containing basidiomycete selective medium
(BSM) or in a rich peptone medium (PM). Biomass production, as determined by respiration experiments in solid-state fermentation
and liquid cultures and fungal growth on Petri dishes, was higher in the PM than in the BSM. Mn2+ affected biomass production only in the PM on Petri dishes. In the nonamended PM, high levels of MnP and VP activity were
detected relative to the nonamended BSM. Nevertheless, a higher rate of 14C-lignin mineralization was measured in the Mn2+-amended BSM, as determined during the course of 47 d of fermentation. Mn2+ amendment of the PM increased mineralization rate to that obtained in the Mn2+-amended BSM. The enzyme activity profiles of MnP and VP were studied in the BSM using anion-exchange chromatography. In the
nonamended BSM, only minute levels of MnP and VP were detected. On Mn2+ amendment, two MnP isoenzymes (B1 and B2) appeared. Isoenzyme B2 was purified and showed 100% identity with the MnP isoenzyme
purified in our previous study from PM-solid-state fermentation (P6). P6 was found to be the dominant isoenzyme in terms of
activity level and gene expression compared with the VP isoenzymes. Based on these results, we concluded that Mn2+ plays a key role in lignin degradation under different nutritional and growth conditions, since it is required for the production
of MnP in P. ostreatus. 相似文献
2.
Stajic M Persky L Hadar Y Friesem D Duletic-Lausevic S Wasser SP Nevo E 《Applied biochemistry and biotechnology》2006,128(1):87-96
Copper (Cu2+) and manganese (Mn2+) ions influenced laccase (Lac) and peroxidase production in Pleurotus eryngii, Pleurotus ostreatus, and Pleurotus pulmonarius. In P. eryngii, the optimum Cu2+ concentration for Lac production was 1 mM and for peroxidases 10mM, and Mn2+ concentration of 5mM led to peaks of Lac and peroxidase activity. In P. ostreatus HAI 493, the highest level of Lac activity was at Cu2+ concentrations of 1 and 10 mM and Mn2+ concentration of 1mM, respectively. The absence of Cu2+ and Mn2+ caused the highest levels of peroxidase production. In P. ostreatus HAI 494, the highest level of Lac activity was at a Cu2+ concentration of 5 mM and at Mn2+ concentration of 1 mM, respectively. High levels of peroxidase activity were found in the medium without and with 1mM Cu2+, and at 1 and 5 mM Mn2+, respectively. In P. pulmonarius, the highest Lac activity was found in the presence of 5 mM Cu2+ and 5 mM Mn2+, respectively. The absence of Cu2+ and Mn2+ as well as their presence at a concentration of 1 mM led to the peaks of peroxidase activities. 相似文献
3.
Thompson David N. Hames Bonnie R. Reddy C. A. Grethlein Hans E. 《Applied biochemistry and biotechnology》1998,(1):967-982
The abilities of lignin peroxidase (LIP) and manganese peroxidase (MNP) fromPhanerochaete chrysosporium to degrade an insoluble hardwood lignin in vitro in aqueous media were tested. Neither LIP nor MNP appreciably changed the
mass or lignin content, although both produced small amounts of unique solubilized lignin fragments. Treatment with both LIP
and MNP, however, decreased the mass by 11%, decreased the lignin content by 5.1% (4.2% as total weight), and solubilized
unique lignin-derived molecules. These results suggest that LIP and MNP synergistically degrade high molecular weight insoluble
lignin, but singly, neither enzyme is sufficient to effect lignin degradation. 相似文献
4.
Heloiza Ferreira Alves-Prado Eleni Gomes Roberto Da Silva 《Applied biochemistry and biotechnology》2006,129(1-3):234-246
Cyclodextrin glycosyltransferase (CGTase) is an enzyme that produces cyclodextrins from starch by an intramolecular transglycosylation
reaction. Cyclodextrins have been shown to have a number of applications in the food, cosmetic, pharmaceutical, and chemical
industries. In the current study, the production of CGTase by Paenibacillus campinasensis strain H69-3 was examined in submerged and solid-state fermentations. P. campinasensis strain H69-3 was isolated from the soil, which grows at 45°C, and is a Gramvariable bacterium. Different substrate sources
such as wheat bran, soybean bran, soybean extract, cassava solid residue, cassava starch, corn starch, and other combinations
were used in the enzyme production. CGTase activity was highest in submerged fermentations with the greatest production observed
at 48–72 h. The physical and chemical properties of CGTase were determined from the crude enzyme produced from submerged fermentations.
The optimum temperature was found to be 70–75°C, and the activity was stable at 55°C for 1 h. The enzyme displayed two optimum
pH values, 5.5 and 9.0 and was found to be stable between a pH of 4.5 and 11.0. 相似文献
5.
Polypropylene powders as the adsorbent for organic solution containing n-hexadecane and olive oil were employed as the carbon source for producing an alkaline lipase from Acinetobacter radioresistens. The best volumetric ratio of n-hexadecane to olive oil around 5 for lipase production was determined from shake-flask and fermentation cultivations. The
existence of a maximum time course lipase activity of the aqueous phase was attributed to the compensation effects of olive
oil on cell growth and lipase production, repression of lipase synthesis by oleic acid, and lipase adsorption on the supports.
A linear relationship between the average cell growth rate in the exponential phase and the ratio of surface areas of the
supports was found. The benefits of using the present fermentation process include less foaming and emulsion of the broth,
less organic phase used, higher lipase production, and easy recovery of the lipase in the centrifugation step. 相似文献
6.
Anthony C. .Grabski Patrick L. Coleman Gary J. Drtina Richard R. Burgess 《Applied biochemistry and biotechnology》1995,55(1):55-73
Manganese peroxidase (MnP) purified fromLentinula edodes was covalently immobilized on 3M’s azlactone-functional copolymer, 3M EmphazeTM AB1 Biosupport Medium. Tethered MnP is capable
of generating Mn3+ from Mn2+ and H2O2. Mn3+, properly chelated, can be used as a nonspecific oxidant of organopollutants. A variety of conditions designed to maximize
coupling efficiency while maintaining Mn3+ -generating catalytic activity were tested. Biochemical characteristics of the MnP enzyme, including amino acid composition,
pH and temperature stability, and concentration of its Mn2+ substrate, influenced chemical conditions necessary for the coupling reaction. The physical parameters of immobilization
reaction time, protein concentration, ionic conditions, pH, and temperature were examined. Results of these experiments indicated
maximum coupling efficiency and enzyme activity were achieved by immobilizing at MnP concentrations < 2 mg/mL for at least
2 h using pH 7.0 buffer containing 1.0M sodium sulfate and 1.0 mM Mn2+. Increasing coupling reaction temperature also improved coupling efficiency. A synthesis of these optimized immobilizations
yielded MnP coupling efficiencies of 40–50% with 35% of the coupled protein retaining enzymatic activity. Results of MnP immobilizations
on nonporous azlactone-functional dispersion polymers more hydrophobic than Emphaze are also reported, and coupling efficiencies
> 65% with 100% of the coupled enzyme active have been measured. 相似文献
7.
Lemos Judith L. S. Fontes Maria C. de A. Pereira Nei 《Applied biochemistry and biotechnology》2001,91(1-9):681-689
The use of purified xylan as a substrate for bioconversion into xylanases increases the cost of enzyme production. Consequently,
there have been attempts to develop a bioprocess to produce such enzymes using different lignocellulosic residues. Filamentous
fungi have been widely used to produce hydrolytic enzymes for industrial applications, including xylanases, whose levels in
fungi are generally much higher than those in yeast and bacteria. Considering the industrial importance of xylanases, the
present study evaluated the use of milled sugarcane bagasse, without any pretreatment, as a carbon source. Also, the effect
of different nitrogen sources and the C∶N ratio on xylanase production by Aspergillus awamori were investigated, in experiments carried out in solid-state fermentation. High extracellular xylanolytic activity was observed
on cultivation of A. awamori on milled sugarcane bagasse and organic nitrogen sources (45 IU/mL for endoxylanase and 3.5 IU/mL for β-xylosidase). Endoxylanase
and β-xylosidase activities were higher when sodium nitrate was used as the nitrogen source, when compared with peptone, urea,
and ammonium sulfate at the optimized C∶N ratio of 10∶1. The use of yeast extract as a supplement to the these nitrogen sources
resulted in considerable improvementin the production of xylanases, showing the importance of this organic nitrogen source
on A. awamori metabolism. 相似文献
8.
Aguilar CN Favela-Torres E Viniegra-González G Augur C 《Applied biochemistry and biotechnology》2002,102(1-6):407-414
Undesirable protease production by Aspergillus niger Aa-20 in submerged culture and solid-state culture was evaluated using different concentrations of tannic acid as sole carbon
source in a model system designed for tannase production. Protease production was found to be dependent on the culture system
used (submerged culture or solid-state culture) and on the initial tannic acid concentration. Expression of protease activity
in submerged culture was higher (up to 10 times) than activity obtained in solid-state culture, using identical culture medium
composition. In submerged culture, the lowest final protease activity (0.13 IU) was obtained with the highest tannic acid
concentration, while in solid-state culture protease activity was not affected by changes in initial substrate concentration.
Absence of detectable proteolytic activity in solid-state culture is related to high production of tannase enzyme. Hence,
the use of solid-state culture for fungal enzyme production may allow for higher and more stable enzyme titers present in
culture extracts. 相似文献
9.
Savini I Santucci R Di Venere A Rosato N Strukul G Pinna F Avigliano L 《Applied biochemistry and biotechnology》1999,82(3):227-241
In this study, we investigated the optical features of the redox metal-dependent proteins cytochrome-c, horseradish peroxidase (HRP), and ascorbate oxidase embedded in a sol-gel-processed silica matrix as a function of gelation
time. Circular dichroism, absorbance, and fluorescence spectroscopies revealed that the sol-gel process affects the complex
structure of the dimeric ascorbate oxidase (although the prosthetic coppers still remain bound to the enzyme) but not that
of monomeric cytochrome-c and HRP. Any modifications in ascorbate oxidase occurred in the initial gelation phase; the drying process induced no further
alterations and the enzyme remained stable for months. Unfolding-refolding experiments on cytochrome-c revealed severely restricted motility in the protein moiety in the xerogel, the concentrated matrix that forms after drying. The diffusion time of the solvent within the matrix, which regulated the
enzyme-substrate reaction rate, depended on the thickness of the monolith, not on the dryness of the specimen. 相似文献
10.
Yakov I. Estrin 《Central European Journal of Chemistry》2004,2(1):52-81
Bimodal molecular mass distribution (MWD) of polymers, obtained upon polymerization of hydrocarbon monomers in the nonpolar
media under the action of dilithium initiators, is the consequence of separation of the reaction mixture into two phases.
Bifunctional /living/ oligomers produce the insoluble sediment due to tetrameric association of the lithium active sites (the
swollen gel-fraction). Part of the active site remains in the solution (the solfraction). Difference in the concentrations
of the active sites into the phases leads to difference between the propagation rates of the /living/ chains and, as a result,
to Bimodal MWD. The mathematical model of polymerization in the two-phase system is proposed. Satisfactory agreement between
the calculations and the experiments is shown for butadiene polymerization in heptane under the action of 1,4-dilithiumpentane.
Regulation of MWD up to the complete elimination of bimodality is possible via the programmed dosage of monomer and solvent
into the reactor. 相似文献
11.
Xiangheng Niu Yanfang He Jianming Pan Xin Li Fengxian Qiu Yongsheng Yan Libo Shi Hongli Zhao Minbo Lan 《Analytica chimica acta》2016
Nanosized materials acting as substitutes of natural enzymes are currently attracting significant research due to their stable enzyme-like characteristics, but some flaws of these nanozymes, including their limited catalytic rate and efficiency, need to be remedied to enable their wider applications. In this work, we verify for the first time the catalytic behavior of uncapped nanobranch-based CuS clews as a peroxidase mimic. XRD, XPS, SEM, and TEM proofs demonstrate that high-purity CuS clews composed of intertwined wires with abundant nanodendrites outside are successfully produced via a facile one-pot hydrothermal synthesis approach, with thiourea as both the sulfion source and the structure-directing agent. The synthesized CuS can catalytically oxidize 3,3′,5,5′-tetramethylbenzidine (TMB) by H2O2 to trigger a visible color reaction with rapid response (reaching a maximum change within 5 min). The proposed CuS nanozyme exhibits preferable catalytic kinetics over natural horseradish peroxidase (HRP). This outstanding activity primarily results from the large surface area and rich sites exposed by the uncapped unique structure. Under optimized conditions, the fabricated sensing system provides linear absorbance (652 nm) changes in the H2O2 concentration range of 0.2˜130 μM, with a detection limit of as low as 63 nM. When coupled with glucose oxidase (GOD), the system is demonstrated to be capable of monitoring glucose in blood samples with excellent performance. 相似文献
12.
Tatýana E. Glotova Nadezhda I. Protsuk Alexander I. Albanov Valentin A. Lopyrev Gennadii V. Dolgushin 《Central European Journal of Chemistry》2003,1(3):222-232
The nucleophilic addition of 2,4-dithiobiurete, 1- and 1,4-substituted 2,4-dithiobiuretes (2 a-e) with benzoylacetylene (1) has been studied. 2-(Benzoylmethyl)-4-(R1-imino)-6-(R2-imino)dihydro-4H-1,3,5-dithiazinium perchlorates (3 a-e) are obtained in glacial acetic acid (AcOH) in the presence of equimolar quantities of HClO4. The reaction of benzoylacetylene with 1,5-diphenyl-2,4-dithiobiurete in either of MeOH, C6H6, or MeCN solvents proceeds non-selectively to give a mixture of products such as 2-(benzoylmethyl)-4,6-di(phenylimino)dihydro-4H-1,3,5-dithiazine
(5), 2-(benzoylmethyl)-4-(β-benzoylvinyl)thio-3-phenyl-6-(phenylimino)-3,6-dihydro-2H-1,3,5-thiadiazine (8), 2-(benzoylmethyl)-1,3-diphenylhexahydro-1,3,5-triazine-4,6-dithione (7) and N-(β-benzoylvinyl)-N-phenylthioureas (6). 相似文献
13.
《Journal of Molecular Structure》2001,560(1-3)
The molecular structure of the endogenous plant hormone (auxin) conjugate, N-(indol-3-ylacetyl)-
-glutamic acid, is deduced by comparison with N2-(indol-3-ylacetyl)glutamine (IAA-Gln), N2-(indol-3-ylacetyl)asparagine (IAA-Asn) and N-(indol-3-ylacetyl)-
-aspartic acid using X-ray structure analysis, 1H-NMR spectroscopy (NOE measurements) and molecular modelling. The significance of the overall molecular shape, and of the resulting amphiphilic properties, of the compounds studied are discussed in terms of possible implications for trafficking between cell compartments. Both in the solid state and in solution, the molecules are in the hair-pin (folded) conformation in which the side chain is folded over the indole ring. While extended conformations can be detected by molecular dynamics simulations, they are so short-lived that any major influence on the biological properties of the compounds studied is unlikely. 相似文献
14.
Production of l-glutamate oxidase (GluOx) by Streptomyces sp. N1 was investigated by controlling culture pH at 6.2, 6.7, 7.0, and 7.3 in a 5-l stirred fermentor. The corresponding GluOx activities obtained were 2.8, 4.2, 6.0, and 5.3 U/mL, respectively. Microbial
growth was inhibited by increasing the medium pH from 6.2 to 7.0. The inhibitory effect was also observed in plate colony
growth under incubation with a different initial pH value. The effect of calcium on GluOx production was also studied in the
pH-controlled bioreactor. When the culture pH was controlled at 6.2 or 7.0, GluOx production could not be improved or was
only improved slightly by initial addition of calcium to the medium. However, when the culture pH was kept at 6.7, initial
Ca2+ addition (60 mM) conspicuously enhanced GluOx production up to 9.3 U/mL, which was about twofold of that without Ca2+ addition. The enzyme production level was the highest ever reported in the literature. During fermentation the inhibition
of cell growth by Ca2+ addition was observed. For the morphological changes, the cells mostly existed as pellets in the medium without Ca2+ addition, whereas few pellets were found and almost all the cells were dispersed mycelia in the broth with Ca2+ addition. 相似文献
15.
Keqiang Ding 《Russian Journal of Electrochemistry》2009,45(3):320-324
For the first time, the electrochemical oxygen reduction reaction (ORR), was investigated using cyclic voltammetry (CV) on
the electrodeposited manganese oxide (MnO
x
)-modified glassy carbon (MnO
x
-GC) electrode in the room temperature ionic liquids (RTILs) of EMIBF4, i.e. 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIBF4). The results demonstrated that, after being modified by MnO
x
on a GC electrode, the reduction peak current of oxygen was increased to some extent, while the oxidation peak current, corresponding
to the oxidation of superoxide anion, i.e., O2− was attenuated in some degree, suggesting that MnO
x
could catalyze ORR in RTILs of EMIBF4, which is consistent with the results obtained in aqueous solution. To accelerate the electron transfer rate, multi-walled
carbon nanotubes (MWCNTs) was modified the GC electrode, and then MnO
x
was electrodeposited onto the MWCNTs-modified GC electrode to give rise to a MnO
x
/MWCNTs-modified GC electrode, consequently, the improved standard rate constant, ks, originated from the modified MWCNTs, along with the modification of electrodeposited MnO
x
, showed us a satisfactory electrocatalysis for ORR in RTILs of EMIBF4.
Published in Russian in Elektrokhimiya, 2009, Vol. 45, No. 3, pp. 340–345.
The article is published in the original. 相似文献
16.
The volumes, heat capacities, and enthalpies of solution of adamantane in cycloxane,n-hexane, and carbon tetrachloride have been measured as a function of concentration at 25°C (15, 25, and 35°C for the volumes). The results extrapolated to infinite dilution have been resolved into cavity formation and interaction terms. The former have been calculated from the equations of the scaled-particle theory. To estimate the contribution from the latter, we have assumed some proportionality between adamantane-solvent and cyclohexane-solvent interactions. This assumption has been verified with the three different solvents for the three studied thermodynamic functions. The diameter of adamantane in solution has been determined to be 6.36 Å. 相似文献
17.
Neslihan Saki Burcak Icli Orkun Cevheroglu Engin U. Akkaya 《Journal of inclusion phenomena and macrocyclic chemistry》2006,55(3-4):219-222
In an attempted synthesis of peripherally pyridine-substituted cucurbituril, an unexpected cyclized product was obtained. A careful NMR analysis followed by mass spectrometry and preliminary crystallographic analyses, helped us in resolving the structure. The structure has two quaternized pyridine functionalities and a groove suitable as a potential receptor site. In addition, just like the parent glycoluril structure, two remaining urea-derived nitrogens can be alkylated by alkyl halides. Thus, we believe this high yielding reaction may become an entry point to a new class of anion receptors. 相似文献
18.
I. M. Gella N. S. Pivnenko L. A. Kutulya T. G. Drushlyak A. Yu. Kulikov N. B. Novikova 《Russian Chemical Bulletin》2005,54(10):2406-2416
Methylenation of (3R,6R)-2-(4-X-benzylidene)-6-isopropyl-3-methylcyclohexanones (X = F, Cl, Ph) with dimethylsulfoxonium methylide occurs stereoselectively
to give 1(S)-(4-X-phenyl)-5(R)-isopropyl-8(R)-methyl-3(R)-spiro[2.5]octanones, whose stereochemistry was established by 1H NMR spectroscopy. The configuration of the chiral centers in the cyclohexanone fragment and its preferred conformation (methyl
is axial and isopropyl is equatorial) in the products do not change with respect to the starting enones. The mutual trans-arrangement of the carbonyl and aryl groups at the newly formed three-membered ring was established; the aryl group also
occupies the trans-position with respect to the axial methyl group of the cyclohexanone fragment. Using methylenation of the compound with X
= Ph as an example, a mixture of by-products resulting from oxidative hydroxylation at the α-position relative to the carbonyl
group was isolated. The resulting chiral spiro[2.5]octanones induce a helical supramolecular ordering in the nematic mesophase
of 4-pentyl-4′-cyanobiphenyl and exhibit a twisting power only somewhat (by 20–30%) lower than the starting enones.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 2331–2341, October, 2005. 相似文献
19.
Ashok K. Ganguli Shalabh Gupta Jing-Tae Zhao E. Alejandro Leon-Escamilla 《Journal of solid state chemistry》2005,178(10):2959-2972
A particular pathology of certain W5Si3-type A5B3 structures (I4/mcm) appears to arise because of unduly close approaches of the A1-type atoms on the cell faces at , 0, () that occur with the larger and more electropositive A and/or in the presence of smaller B atoms. A structure refinement of binary Ba4.81Pb3 indicates such a marginal stability in that the Ba atoms in the facial Ba0.81 chains exhibit an extreme displacement ellipsoid along . Although Ca5Sn3 and La5Ga3 binaries are unknown in this structure type, five stable ternary derivatives of these have been synthesized via substitution reactions and characterized by single crystal X-ray diffraction means: Ca4Sn3.223(4)Mg0.777, Ca4Sn3Cu1.30(4), Ca4.66(6)Sn3Zn0.704(4), La4.81(1)Ga1.38(2)Al1.62, and La4.762(5)Ga1.5(1)Zn1.5. Only the Ca-Sn-Zn phase exhibits lower symmetry, P4/mbm. The problematic A1 sites exhibit diverse changes in these, whereas the surrounding B2 tetrahedra are largely unaltered. The Ca-Sn results are, respectively: direct Mg/Sn substitution at the Ca1 site; mixed fractional distribution of the smaller Cu at two sites around the A1 position with an unresolved disorder; a pair of apparently independent modes, fractional Ca in the normal position and fractional Zn rectangles thereabout. The two La-Sn phases contain normal Ga,Al (Ga,Zn) tetrahedral chains with pairs of fractional disordered La atoms along , 0, z. Each can be rationalized in terms of a reasonable incommensurate structure. Electronic effects may also be operable. 相似文献
20.
A. Yu. Lepeshkin K. F. Turchin E. G. Gal’pern I. V. Stankevich K. A. Lyssenko V. S. Velezheva 《Russian Chemical Bulletin》2007,56(7):1447-1455
Based on the results of studies of the deuterium exchange and dehydration of 4-hydroxy-Δ2-thiazolines and 2-R-4-acetyl-8b-hydroxy-3a,8b-dihydro-4H-thiazolo[5,4-b]indoles containing the α-methylene (methine) unit at the C(2) atom, the mechanism of dehydration of these compounds generated
as intermediates in the Hantzsch synthesis of thiazoles and 2-R-4-acetyl-4H-thiazolo[5,4-b]indoles was proposed. This mechanism includes an additional step of the formation of the corresponding Δ3-thiazolines. According to the results of quantum chemical calculations, this is energetically more favorable than the dehydration
in terms of the commonly accepted mechanism. In some cases, an acidic medium impedes the dehydration of 4-hydroxy-Δ2-thiazolines or their cyclic analogs. The proposed mechanism provides an explanation for the empirical data on the differences
in the reactivities of both thioamides and α-haloketones, which have remained unexplained in terms of the commonly accepted
mechanism. The spontaneous thiazole synthesis is virtually impossible starting from thioamides of aromatic or heteroaromatic
acids and α-haloketones bearing electron-withdrawing α′ substituents or cyclic bromoindoxyl-type haloketones. In the thiazole
synthesis from these starting components, it is expedient to perform dehydration under basic catalysis.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1394–1402, July, 2007. 相似文献