首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 531 毫秒
1.
It is well known that lignin degradation is a key step in the natural process of biomass decay whereby oxidative enzymes such as laccases and high redox potential ligninolytic peroxidases and oxidases play a central role. More recently, the importance of these enzymes has increased because of their prospective industrial use for the degradation of the biomass lignin to increase the accessibility of the cellulose and hemicellulose moieties to be used as renewable material for the production of fuels and chemicals. These biocatalysts also present potential application on environmental biocatalysis for the degradation of xenobiotics and recalcitrant pollutants. However, the cost for these enzymes production, separation, and concentration must be low to permit its industrial use. This work studied the concentration of lignin peroxidase (LiP), produced by Streptomyces viridosporus T7A, by ultrafiltration, in a laboratory-stirred cell, loaded with polysulfone (PS) or cellulose acetate (CA) membranes with molecular weight cutoffs (MWCO) of 10, 20, and 50 KDa. Experiments were carried out at 25 °C and pH 7.0 in accordance to the enzyme stability profile. The best process conditions and enzyme yield were obtained using a PS membrane with 10 KDa MWCO, whereby it was observed a tenfold LiP activity increase, reaching 1,000 U/L and 90% enzyme activity upholding.  相似文献   

2.
In the white-rot basidiomycete,Phanerochaete chrysosporium, ligninolytic activity appears with the transition from primary to secondary metabolism brought on by depletion of fixed nitrogen. To explore changes in cellular physiology during this transition two aspects of cell metabolism have been studied. Firstly, proteins associated with the fungus were separated by twodimensional polyacrylamide gel electrophoresis according to their isoelectric point and molecular weight. Ribosomal, cytoplasmic, and cell wall-associated proteins were separated and the protein patterns compared after growing the fungus under lignin degrading (nitrogen limited) and nonlignin-degrading (nitrogen excess) conditions. We find major differences in the protein populations of nonligninolytic and ligninolytic cultures; in the case of the cytoplasmic proteins there are approximately 20 novel proteins in the latter, but other protein species disappear. Attempts to identify some of the novel secondary phase proteins will be described. The patterns from some mutants of P.chrysosporium defective in ligninolytic activity or other aspects of secondary metabolism will also be discussed. We have also studied the intracellular cyclic AMP levels during the onset of ligninolytic activity. These increased sixfold between days 3 and 5 and were maximal as the culture became ligninolytic. In control cultures (nitrogen excess), there was no ligninolytic activity and cAMP levels merely reflected growth. To determine the effect of added nitrogen on cAMP levels 0.72M glutamate (final conc.) was added to ligninolytic cultures. The level of cAMP was halved between 4 and 8 h after glutamate addition, and ligninolytic activity was also suppressed as expected. Some of the mutants of P.chrysosporium defective in ligninolytic activity showed decreased levels of intracellular cAMP. We thank the Agricultural Research Council and the British Petroleum Venture Research Unit for support.  相似文献   

3.
The white rot fungus Phanerochaete chrysosporium has been identified to be an environmentally useful microorganism for the degradation of various hazardous pollutants, mainly because of its ligninolytic enzyme system, particularly the lignin peroxidase (LiP) secreted by the fungus. In the present work, the behavior of the fungus in liquid medium due to variation in physico-chemical parameters, i.e., glucose concentration, nitrogen concentration, agitation, etc., was studied. Increment of the initial concentration of glucose in the medium increases the biomass growth and LiP activity, when cultured under controlled conditions. The biomass growth and LiP activity by the fungus was modeled following stochastic approach. The behavior of growth and enzyme activity of the fungus observed from the model were found to be in agreement with the experiments qualitatively.  相似文献   

4.
Lignocellulosic wastes such as neem hull, wheat bran, and sugarcane bagasse, available in abundance, are excellent substrates for the production of ligninolytic enzymes under solid-state fermentation by white-rot fungi. A ligninolytic enzyme system with high activity showing enhanced decomposition was obtained by cocultivation of Pleurotus ostreatus and Phanerochaete chrysosporium on combinations of lignocellulosic waste. Among the various substrate combinations examined, neem hull and wheat bran wastes gave the highest ligninolytic activity. A maximum production of laccase of 772 U/g and manganese peroxidase of 982 U/g was obtained on d 20 and lignin peroxidase of 656 U/g on d 25 at 28±1 °C under solid-state fermentation. All three enzymes thus obtained were partially purified by acetone fractionation and were exploited for decolorizing different types of acid and reactive dyes.  相似文献   

5.
Marine-derived fungi are prone to produce structurally unique secondary metabolites, a considerable number of which display the promising biological properties and/or industrial applications. Among those, ligninolytic enzymes have attracted great interest in recent years. In this work, about 20 strains were isolated from sea mud samples collected in the East China Sea and then screened for their capacity to produce lignin-degrading enzymes. The results showed that a strain, named J63, had a great potential to secrete a considerable amount of laccase. Using molecular method, it was identified as an endophytic fungus, Pestalotiopsis sp. which was rarely reported as ligninolytic enzyme producer in the literature. The production of laccase by Pestalotiopsis sp. J63 was investigated under submerged fermentation (SF) and solid state fermentation (SSF) with various lignocellulosic by-products as substrates. The SSF of rice straw powder accumulated the highest level of laccase activity (10,700 IU/g substrate), whereas the SF of untreated sugarcane bagasse provided the maximum amount of laccase activity (2,000 IU/ml). The value was far higher than those reported by other reports. In addition, it produced 0.11 U/ml cellulase when alkaline-pretreated sugarcane bagasse was used as growth substrate under SF. Meanwhile, the growth of fungi and laccase production under different salinity conditions were also studied. It appeared to be a moderately halo-tolerant organism.  相似文献   

6.
Species of the genus Pleurotus are among the most efficient natural species in lignin degradation belonging to the subclass of ligninolytic organisms that produce laccase (Lac), Mn-dependent peroxidase (MnP), versatile peroxidase (VP), and the H2O2-generating enzyme aryl-alcohol oxidase, but not lignin peroxidases. Production of Lac and oxidation of 2,6-dimethoxyphenol (DMP) in the presence and absence of Mn2+ were detected both in submerged fermentation (SF) of dry ground mandarine peels and in solid-state fermentation (SSF) of grapevine sawdust in all investigated Pleurotus species and strains. Evidence of cultivation methods having a distinct influence on the level of enzyme activities has been demonstrated. Most of the species and strains had higher Lac activity under SSF conditions than under SF conditions. DMP oxidation in the presence and absence of Mn2+ was detected in all investigated species and strains, but was lower under SF conditions than under SSF conditions for most of them. However, relative activities of DMP oxidation in the absence of Mn2+, as percentages of activity agasint DMP in the presence of Mn2+, were higher under conditions of SF than in SSF cultures in most of the investigated species and strains. The obtained results showed that strains of different origins have different efficiently ligninolytic systems and that conditions of SSF are more favorable for ligninolytic activity than those in SF owing to their similarity to natural conditions on wood substrates.  相似文献   

7.
Four isoforms of the extracellular lignin peroxidase of the ligninolytic actinomyceteStreptomyces viridosporus T7A (ALip-P1, P2, P3, and P4) were individually purified by ultrafiltration and ammonium sulfate precipitation, followed by electro-elution using polyacrylamide gel electrophoresis. Three of the purified peroxidases were compared for their immunologic relatedness by Western blot analysis using a polyclonal antibody preparation produced in rabbits against pure isoform P3. The anti-P3 antibody was also tested for its reactivity towards a lignin peroxidase from the white-rot fungusPhanerochaete chrysosporium and another ligninolytic actinomyceteStreptomyces badius 252. Results showed that peroxidases ALip-P1 through ALip-P3 are immunologically related to one another. The peroxidases ofS. badius, but not the peroxidase ofP. chrysosporium, also reacted with the antibody, thus indicating that the lignin peroxidases ofS. viridosporus andS. badius are immunologically related. Based upon its specific affinity, lignin peroxidase isoform ALip-P3 ofS. viridosporus was readily purified using an anti-P3 antibody affinity column.  相似文献   

8.
Structure and Action Mechanism of Ligninolytic Enzymes   总被引:2,自引:0,他引:2  
Lignin is the most abundant renewable source of aromatic polymer in nature, and its decomposition is indispensable for carbon recycling. It is chemically recalcitrant to breakdown by most organisms because of the complex, heterogeneous structure. The white-rot fungi produce an array of extracellular oxidative enzymes that synergistically and efficiently degrade lignin. The major groups of ligninolytic enzymes include lignin peroxidases, manganese peroxidases, versatile peroxidases, and laccases. The peroxidases are heme-containing enzymes with catalytic cycles that involve the activation by H2O2 and substrate reduction of compound I and compound II intermediates. Lignin peroxidases have the unique ability to catalyze oxidative cleavage of C–C bonds and ether (C–O–C) bonds in non-phenolic aromatic substrates of high redox potential. Manganese peroxidases oxidize Mn(II) to Mn(III), which facilitates the degradation of phenolic compounds or, in turn, oxidizes a second mediator for the breakdown of non-phenolic compounds. Versatile peroxidases are hybrids of lignin peroxidase and manganese peroxidase with a bifunctional characteristic. Laccases are multi-copper-containing proteins that catalyze the oxidation of phenolic substrates with concomitant reduction of molecular oxygen to water. This review covers the chemical nature of lignin substrates and focuses on the biochemical properties, molecular structures, reaction mechanisms, and related structures/functions of these enzymes. Reference to a company and/or products is only for purposes of information and does not imply approval of recommendation of the product to the exclusion of others that may also be suitable. All programs and services of the US Department of Agriculture are offered on a nondiscriminatory basis without regard to race, color, national origin, religion, sex, age, marital status, or handicap.  相似文献   

9.
Ligninolytic enzymes are well-known to play the crucial roles in lignin biodegradation and have potential applications in industrial processes. The filamentous white-rot fungus, Phanerochaete chrysosporium, has been widely used as a model organism for studying these ligninolytic enzymes that are able to degrade the lignin during the secondary metabolism. To study the gene expression in secondary metabolism and metabolic switching phase of P. chrysosporium, we constructed a metabolic-switching phase suppression subtractive hybridization (SSH) cDNA library and a secondary metabolic phase SSH cDNA library to compare their mRNA expression profiles. We isolated the genes that are specially expressed and subsequently identified four genes that specially expressed during metabolic-switching phase while 22 genes in secondary metabolic phase. Accordingly, these specially expressed genes might play key roles in different metabolic stages, which would offer more new insights into the shift from nitrogen to lignin metabolism.  相似文献   

10.
The possibility has been shown of the rational use of lignocellulose wastes as components of a nutrient medium for the deep cultivation of some wood-destroying basidial fungi isolated from various sources and actively breaking down natural polysaccharides and lignin with the formation of ligninolytic enzymes and biologically valuable products. An active producing agent of ligninolytic enzymes (laccase, peroxidase, lignin peroxidase, polyphenoloxidase, Mn-dependent peroxidase) has been revealed as Pleuroms ostreatus, strain UzBI-I108. The optimum conditions have been determined for the formation of enzymes and the secretion of total ligninase preparations with a fairly high specific activity of lignin peroxidase.Institute of Microbiology Academy of Sciences, Republic of Uzbekistan, Tashkent, fax (3712) 41 7129. Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 739–747, September–October, 1995. Original article submitted November 11, 1994.  相似文献   

11.

The production of lignin peroxidase byStreptomyces viridosporus T7A was studied in shake flasks and under aerobic conditions in a 7.5-L batch fermentor. Lignin peroxidase synthesis was found to be strongly affected by catabolite repression. Lignin peroxidase was a non-growth-associated, secondary metabolite. The maximum lignin peroxidase activity was 0.064 U/mL at 36 h.

In order to maximize lignin peroxidase activity, optimal conditions were determined. The optimal incubation temperature, pH, and substrate (2,4-dichlorophenol) concentration for the enzyme assays were 45°C, 6, and 3 mM, respectively. Stability of lignin peroxidase was determined at 37, 45, and 60°C, and over the pH range 4–9.

  相似文献   

12.
A detailed presentation was given of the discovered and studied enzymes involved in degradation of cellulose and lignin by the white-rot fungus,Sporotrichum pulverulentum (Phanerochaete chrysosporium). The fungus utilizes, for the degradation of cellulose: (a) Five different endo-1,4-Β-glucanases (b) One exo-1,4-Β-glucanase (acting synergistically with the endoglucanases) (c) Two 1,4-Β-glucosidases The regulation, induction, and catabolite repression of the endoglucanases have been studied in depth and the results of these studies were also presented. In addition to the hydrolytic enzymes,S. pulverulentum also produces the oxidative enzyme cellobiose oxidase that is of importance for cellulose degradation. Another unconventional enzyme is cellobiose: quinone oxidoreductase, which is of importance for both cellulose and lignin degradation. It reduces quinones from the lignin under oxidation of cellobiose from the cellulose. It has recently been discovered thatS. pulverulentum produces two acidic proteases of importance for cellulose degradation since they enhance the endoglucanase activity, particularly in young cultures of the fungus grown on cellulose. The enzymes involved in lignin degradation are not known nearly as well as these involved in cellulose degradation. However, extracellular phenol oxidases, laccase, and peroxidase have been shown to be involved in and necessary for lignin degradation to take place. A phenol oxidase-less mutant ofS. pulverulentum cannot degrade lignin unless a phenol oxidase is added to the medium. Recently, an enzyme splitting the α—Β bond in the propane side chain has been discovered by Kirk and coworkers. Several enzymes involved in the metabolism of vanillic acid, always a metabolite in lignin degradation, have been discovered and studied in our laboratory. Presentations of the enzymes for decarboxylation, demethoxylation, methanol oxidation, ring cleavage, and intracellular quinone reduction by NAD(P)H: quinone oxidoreductase were given. A discussion of possibilities for a specific enzymic primary attack on the native lignin, as well as of the likeliness for an unspecific radical nature of this attack, was also given.  相似文献   

13.
The wood-rotting basidiomyceteCoriolus versicolor has been grown under a variety of conditions ranging from stationary cultures on spruce wood chips or milled-wood lignin, known to be actively ligninolytic, to agitated submerged cultures, with glucose or carboxymethylcellulose as the main carbon source, that had no ligninolytic activity. Extracellular proteins have been recovered from the growth medium by ammonium sulfate precipitation and fractionated into their polypeptide components by a combination of ion exchange, affinity column chromatography, and polyacrylamide gel electrophoresis, thus providing a “fingerprint” technique for different growth conditions. Characterization of some of the polypeptide components on the PAGE plates can be made by the use of selected staining techniques for proteins, glycoproteins, peroxidase activity, and heme-containing polypeptides. Variations in the “fingerprints” from different cultures can be demonstrated, in addition to showing the development of the extracellular protein population in an actively ligninolytic culture during the change from primary to secondary growth phases. The effect of some of the extracellular enzymes on polymeric lignin has been demonstrated. A crude protein extract isolated from rotting wood chips was incubated with milled-wood lignin extracted from spruce sapwood. Analysis of the lignin after 48 h incubation by UV and NMR spectroscopy showed there to be an increase in aromatic hydroxyl groups with a decrease in aliphatic hydroxyl groups in comparison with sound milled-wood lignin. There was also a small reduction in the mean molecular weight of the lignin, analyzed by HPLC size-exclusion chromatography. By contrast, lignin that had been incubated with purified laccase A showed a considerable increase in the mean molecular weight, almost doubling over a 48-h period of incubation.  相似文献   

14.
The formation and decay of lignolytic enzymes, along with the generation of other extracellular metabolites in submerged cultures ofPhanerochaete chrysosporium, were studied under different physiological conditions. Whereas lignin peroxidase (LiP) was detectable only in a narrow range of O2 tension and nitrogen concentration, manganese peroxidase (MnP) reached considerable levels over a broad range. The decay of LiP and MnP activities under lignolytic conditions paralleled that of heme and total proteins. The conditions that decrease or suppress LiP or MnP activities resulted in high levels of extracellular protease activity and/or polysaccharides.  相似文献   

15.
The extracellular fluid of ligninolytic cultures of the white-rot wooddestroying fungus,Phanerochaete chrysosporium Burds., contains an enzyme that degrades lignin model compounds as well as lignin itself (1). Like ligninolytic activity, the enzyme appears during idiophasic metabolism, which is triggered by nitrogen starvation. The enzyme has been purified to homogeneity by DEAE-Biogel A chromatography, as assessed by SDS polyacrylamide gel electrophoresis, isoelectric focusing, and gel filtration chromatography. These techniques also revealed a molecular weight of 42,000 daltons, and an isoelectric point of 3.4. The purified enzyme exhibits low substrate specificity. It is an oxygenase, but requires hydrogen peroxide for activity. The activity is optimum at 0.15 mM H2O2; at concentrations above 0.5 mM, H2O2is inhibitory. Model compound studies have shown that the enzyme catalyzes cleavage between Cα and Cß in compounds of the type aryl-CαHOH—CßHR-(R = -aryl or -O-aryl), and in the Cα-hydroxyl-bearing propyl side chains of lignin. This cleavage produces an aromatic aldehyde moiety from the Cα-portion, and a Cß-hydroxylated moiety from the Cα-portion. Cleavage between Cα and Cß in arylglycerol-Β-aryl ether structures leads indirectly to cleavage of the Β-aryl ether linkage, which is the most abundant intermonomer linkage in lignin. The Cß-hydroxyl oxygen comes from molecular oxygen, and not from H2O2, as determined by18O isotope studies. The pH optimum for these reactions is between 2.5 and 3.0; no activity is observed above pH 5. Formation of the expected aldehydes from spruce and birch lignins, and partial depolymerization of the lignins results from the action of the purified enzyme. In addition to Cα—Cß cleavage, the enzyme catalyzes aromatic alcohol oxidation, aryl methylene oxidation, hydroxylation at Cα and Cß in models containing a Cα—Cß double bond, intradiol cleavage in phenylglycol structures, and phenol oxidations.  相似文献   

16.
The effects of low and ultra-low doses of X-ray radiation and neutron fluxes produced by continuous-wave and pulsed sources of different nature and power on the activity of plant peroxidases and the bovine lung angiotensin-converting enzyme were studied. Certain ranges of doses (including ultra-low), the exposure to which under particular conditions causes the in vitro activation and/or inactivation of the enzymes, were found. Possible factors responsible for this phenomenon are discussed.  相似文献   

17.
The phthalocyanine dyes, Remazol Turquoise Blue G133, Everzol Turquoise Blue and Heligon Blue S4 are found to be biosorbed by Phanerochaete chrysosporium (white-rot fungi) and also metabolised by its ligninolytic extracellular enzymes resulting in dye decolourisation, formation of free copper ions and organic metabolites with ultimate extensive phthalocyanine ring breakdown. It is believed that the ligninolytic extracellular enzyme laccase is involved in the early production of a metabolite M8 which involves break-up of the conjugated phthalocyanine ring structure but which retains multi-negative charge. Another ligninolytic extracellular enzyme, manganese peroxidase, is believed to be involved in the release of Cu2+ from the phthalocyanine structure to give a non-copper-containing phthalocyanine metabolite M1 with a slightly longer migration time than the parent dye and absorption at 666 nm. The phthalocyanine ring structure is also broken up by metabolic processes that involve desulphonation and oxidation to give phthalimide (M3) and an unidentified electroactive metabolite M2. Other minor, unidentified metabolites are observed using capillary electrophoresis and liquid chromatography.  相似文献   

18.
Lignin degradation by white-rot fungi proceeds via free radical reaction catalyzed by oxidative enzymes and metabolites. Basidiomycetes called selective white-rot fungi degrade both phenolic and non-phenolic lignin substructures without penetration of extracellular enzymes into the cell wall. Extracellular lipid peroxidation has been proposed as a possible ligninolytic mechanism, and radical species degrading the recalcitrant non-phenolic lignin substructures have been discussed. Reactions between the non-phenolic lignin model compounds and radicals produced from azo compounds in air have previously been analysed, and peroxyl radical (PR) is postulated to be responsible for lignin degradation (Kapich et al., FEBS Lett., 1999, 461, 115-119). However, because the thermolysis of azo compounds in air generates both a carbon-centred radical (CR) and a peroxyl radical (PR), we re-examined the reactivity of the three radicals alkoxyl radical (AR), CR and PR towards non-phenolic monomeric and dimeric lignin model compounds. The dimeric lignin model compound is degraded by CR produced by reaction of 2,2'-azobis(2-amidinopropane) dihydrochloride (AAPH), which under N(2) atmosphere cleaves the α-β bond in 1-(4-ethoxy-3-methoxyphenyl)-2-(2-methoxyphenoxy)-1,3-propanediol to yield 4-ethoxy-3-methoxybenzaldehyde. However, it is not degraded by the PR produced by reaction of Ce(4+)/tert-BuOOH. In addition, it is degraded by AR produced by reaction of Ti(3+)/tert-BuOOH. PR and AR are generated in the presence and absence of veratryl alcohol, respectively. Rapid-flow ESR analysis of the radical species demonstrates that AR but not PR reacts with the lignin model compound. Thus, AR and CR are primary agents for the degradation of non-phenolic lignin substructures.  相似文献   

19.
Most glucosyltransferase (GTF) activity in sucrose-grown cultures of some strains of Leuconostoc mesenteroides is found with the cell pellet after centrifugation. GTFs are known to bind to dextrans, and it was traditionally assumed that cell-associated GTFs were bound to those dextrans that cosedimented with the cells. We used a mutant strain (LC-17), derived from strain NRRL B-1355, which produced dextransucrase in the absence of dextrans, to investigate the extent to which GTFs were bound to cells or dextrans. Much of the GTF activity in glucose-grown cultures of strain LC-17, which do not produce dextran, was located in the cell pellets. Soluble enzyme activity increased when cell suspensions from glucose- or sucrose-grown cultures were incubated with mild nonionic detergents or zwitterionic reagents. Alternansucrase produced by the parent strain B-1355 was almost entirely associated with cells under conditions in which dextrans were or were not produced. Alternansucrase, but not dextransucrase, tended to be enriched in the particulate fraction of B-1355 cells that had been broken in a French press. The distribution of alternansucrase and the effects of detergents on the distribution of GTFs suggest that soluble GTFs sequestered in the cytoplasm, and GTFs bound or adsorbed to the cell membrane are probably the major contributors to the cell-associated GTF activity.  相似文献   

20.
Screening thermotolerant white-rot fungi for decolorization of wastewaters   总被引:2,自引:0,他引:2  
To select a thermotolerant fungal strain for decolorization of wastewaters, ligninolytic enzyme production (lignin peroxidase, manganese peroxidase [MnP], and laccase), decolorization, and removal of total phenol and chemical oxygen demand (COD) were detected. Thirty-eight fungal strains were studied for enzyme production at 35 and 43°C on modified Kirk agar medium including 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) and MnCl2. Thirteen strains grew on manganese-containing agar and provided green color on ABTS-containing agar plates under culture at 43°C. Decolorization of wastewater from alcohol distillery (WAD) by these strains was compared under static culture at 43°C, and Pycnoporus coccineus FPF 97091303 showed the highest potential. Thereafter, immobilized mycelia were compared with free mycelia for WAD decolorization under culture conditions of 43°C and 100 rpm. The immobilized mycelia on polyurethane foam enhanced the ligninolytic enzyme production as well as total phenol and color removal. At about the same COD removal, MnP and laccase produced by immobilized mycelia were 2 and 19 times higher than by free mycelia; the simultaneous total phenol and color removal were 3.1 and 1.5 times higher than the latter. Moreover, decolorization of synthesis dye wastewater was carried out at 43°C and 100 rpm. More than 80% of 300 mg/L of reactive blue-5 was decolorized by the immobilized mycelia within 1 to 2 d for four cycles.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号