Effect of aeration on lignin peroxidase production by Streptomyces viridosporus T7A

The effect of aeration on lignin peroxidase production by Streptomyces viridosporus T7A was studied in a bench-scale bioreactor using a previously optimized growth medium (0.65% yeast extract and 0.1% corn oil, pH7.0) at 37°C and natural pH. Airflow rates of 0.3, 1.0, and 1.5 vvm and a fixed agitation of 200 rpm were initially studied followed by 1.0 vvm and 200, 300, 400, and 500 rpm. The use of 1.0 vvm and 400 rpm increased enzyme concentration 1.8-fold (100–180 U/L) and process productivity 4.8-fold (1.4–6.7 U/[L·h]) in comparison with the use of 200 rpm and 0.3 vvm. The inexpensive corn oil, used as carbon source, besides its antifoam properties, proved to be nonrepressive for enzyme production.     

Lignin peroxidase and protease production by Streptomyces viridosporus T7A in the presence of calcium carbonate

Streptomyces are good producers of enzymes of industrial interest, such as lignin peroxidase (LiP) and proteases. To optimize production of these enzymes by Streptomyces viridosporus T7A, two parameters were evaluated: carbon sources and calcium carbonate. Shake-flask fermentations were performed using culture media, with and without CaCO₃, contained yeast extract, mineral salts and either glucose, lactose, galactose, or corn oil. In the absence of calcium carbonate, the maximum values for LiP and protease activities occurred during the idiophase with LiP activity being favored by glucose, corn oil, and galactose, and protease activity being favored only by corn oil. Calcium carbonate affected the cell morphology by reducing the size of the pellets. Moreover, in the presence of the salt, LiP production was growth-associated in all media but the glucose medium. Higher enzyme levels were observed when galactose and glucose were used as carbon sources. Protease activity was repressed by both glucose and galactose, whereas corn oil was the best carbon source for the enzyme production. Calcium carbonate increased LiP production by up to 2.6-fold. Such improvement was not observed for protease production, suggesting a selective effect of CaCO₃ on LiP activity.     

Synthesis and properties of lignin peroxidase fromstreptomyces viridosporus T7A

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.

     

Mass transfer,adsorption and reaction in slurry reactors

The performance of three-phase isothermal slurry reactors with continuous gas flow and batch liquid may be affected by gas-bubble-to-liquid and liquid-to-catalyst-particle mass transfer, intraparticle diffusion in the pores of the particles, and adsorption and surface reaction. In dynamic operation, e.g. by introducing a pulse of reactant in the gas feed, the rates of adsorption and surface reaction are not necessarily equal. Equations for a first-order reaction are developed for the zeroth and first moments, in both the effluent gas and the batch liquid, in terms of the separate rate constants for adsorption and surface reaction and the other pertinent rate and equilibrium constants. The results show that under some operating conditions it should be possible to evaluate, from experimentally determined moments, the separate values of the adsorption and reaction rate constants. This would eliminate the assumption that one of the steps is rate controlling.Dynamic adsorption and reaction data are apparently unavailable at present to apply in the derived equations. However, for the special case of adsorption in the absence of reaction, for which experimental data are available, the predicted moments agree with the experimental values.     

催化氧化降解木质素的研究进展

本文从所用催化剂、反应条件、反应机理等几个方面综述了木质素催化氧化降解方面的研究,着重介绍了以O_2和H_2O_2为氧化剂的金属为催化中心的氧化降解,例如,金属有机催化氧化、金属/溴化物催化氧化、金属配合物催化氧化、金属复合氧化体系和钛矿型复合氧化物催化氧化、金属/分子筛催化氧化和以自身为氧化剂的催化氧化等,以及无金属催化氧化降解、微波辅助氧化降解、光催化氧化降解和电化学氧化降解。     

Enzymes involved in cellulose and lignin degradation

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.     

Preparation of modified hydrolysis lignin and its use for filling epoxy polymers and enhancing their flame resistance

The reaction of hydrolysis lignin with orthophosphoric acid and urea under the conditions of reactant fusion without a solvent was studied. The influence of the reactant ratio and of the reaction temperature and time on the degree of chemical binding of phosphorus and nitrogen with lignin was examined. The modification products can be used as fire-retardant fillers for epoxy compounds.     

Pathways for degradation of lignin in bacteria and fungi

Lignin is a heterogeneous aromatic polymer found as 10-35% of lignocellulose, found in plant cell walls. The bio-conversion of plant lignocellulose to glucose is an important part of second generation biofuel production, but the resistance of lignin to breakdown is a major obstacle in this process, hence there is considerable interest in the microbial breakdown of lignin. White-rot fungi are known to break down lignin with the aid of extracellular peroxidase and laccase enzymes. There are also reports of bacteria that can degrade lignin, and recent work indicates that bacterial lignin breakdown may be more significant than previously thought. The review will discuss the enzymes for lignin breakdown in fungi and bacteria, and the catabolic pathways for breakdown of the β-aryl ether, biphenyl and other components of lignin in bacteria and fungi. The review will also discuss small molecule phenolic breakdown products from lignin that have been identified from lignin-degrading microbes, and includes a bioinformatic analysis of the occurrence of known lignin-degradation pathways in Gram-positive and Gram-negative bacteria.     

In vitro degradation of insoluble lignin in aqueous media by lignin peroxidase and manganese peroxidase

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.     

鼓泡浆态反应器中低温甲醇合成的探索

为了开发低温液相甲醇合成新工艺,使用CuCr／CH3ONa催化体系,在直径40mm的鼓泡浆液反应器中考察了低温甲醇合成的反应性能。鼓泡浆液反应器使用的浆液由铜铬催化剂、甲醇钠溶液、乳化剂OP-10和液相介质二甲苯组成。实验结果表明在90℃～110℃、4．8MPa和操作气速0．2cm／s下,前9h的CO平均转化率达到78％。甲醇是反应的主要产物。与搅拌釜中的实验结果比较,鼓泡浆液反应器的反应效率为搅拌釜的80％。这是由于甲醇钠的消耗和乳化剂的负效应所致。实验结果示范了鼓泡浆态反应器中低温甲醇合成的可行性。     

Aromatic products of radiation-thermal degradation of lignin and chitin

Lignin and chitin degradation in the high-temperature radiolysis mode at ≤295°C has been investigated. Experimental conditions ensured the removal of low-molecular-weight products from the irradiation zone via volatilization. The formation of the low-molecular-weight aromatic products methoxyphenols and pyridine derivatives from lignin and chitin, respectively, has been shown. The yield of the distillable aromatic products was much higher than in the case of conventional dry distillation. It is noted that the mechanism of high-temperature radiolytic transformations of lignin and chitin differs from the mechanism of thermal transformations, which is due to the thermally stimulated degradation of radiation-induced radicals. It has been shown that high-temperature radiolysis opens a possibility for producing aromatic hydrocarbons at a lower dose rate and at lower temperature in comparison with conventional radiolysis and pyrolysis.     

GC-MS and HPLC analyses of lignin degradation products in biomass hydrolyzates

Summary The gas-chromatographic separation of lignin degradation products of hydrolytically degraded biomass (e. g. poplar wood) and their mass spectrometric identification are described. For routine analysis of lignin degradation products of biomass hydrolyzates, a time saving HPLC gradient method using a UV-detection system (280 nm), is described. In addition to reference samples, solutions of hydrothermally degraded biomass were analyzed.

---

GC-MS- und HPLC-Analytik von Ligninabbauprodukten in Biomassehydrolysaten

Zusammenfassung Die gas-chromatographische Trennung von Ligninabbauprodukten nach hydrolytischer Spaltung von Biomasse (z.B. Pappelholz) sowie die massenspektrometrische Identifizierung werden beschrieben. Für eine routinemäßige Analytik der Ligninabbauprodukte in Biomassehydrolysaten wird weiterhin die Trennung mittels einer Gradienten-HPLC-Methode aufgezeigt. Die Detektion erfolgte bei 280 nm. Neben Referenzproben wurden hydrothermale Abbaulösungen untersucht.

     

Thermal degradation of polymers and flame retardants

We have carried out simultaneous Thermal Analysis/Mass Spectrometry by use of a Netzsch STA 429 Thermal Analyzer (TG-DTG-DTA) combined with a Balzers QMG 511 quadrupole Mass Spectrometer.The combined apparatus is interfaced to a Digital Equipment PDP 11/23+ microcomputer. The complete set of the TA/MS data obtained simultaneously after each run results in detailed information about the thermal degradation of a sample material in general and in addition about the structure-temperature dependent fragmentation. Experiments by use of a Perkin-Elmer DSC 7 Thermal Analysis Station leads to quantitative determination of the characteristic data.

---

Zusammenfassung Es wurden simultane thermoanalytische — massenspektrometrische Untersuchungen mit Hilfe einer Gerätekombination Netzsch STA 429 (Thermowaage) und Balzers QMG 511 (Quadrupol Massenspektrometer) durchgeführt. Dieses Kopplungssystem ist mit einem Digital Equipment PDP 11/23+ Microcomputer verbunden. Der komplette Datensatz, der aus einer TA/MS Messung erhalten wird, charakterisiert in sehr detaillierter Weise das thermische Abbauverhalten von Substanzen und gibt Aufschluß über die temperatur-struktur-abhängige Fragmentierung der Verbindungen.

---

, /-/ - 511. 11/23. /MC, , - . , - 7, .

     

The impact of genetic engineering on the commercial production of antibiotics byStreptomyces and related bacteria

Developments inStreptomyces genetics that have laid a foundation for this field over the past ten years are reviewed and discussed to suggest how this knowledge might useful for improving the commercial production of antibiotics. This brief analysis predicts a bright future for the application ofStreptomyces genetics in antibiotic production.     

Photo- and radiation chemical induced degradation of lignin model compounds

The basic mechanistic aspects of the photo- and radiation chemistry of lignin model compounds (LMCs) are discussed with respect to important processes related to lignin degradation. Several reactions occur after direct irradiation, photosensitized or radiation chemically induced oxidation of LMCs. Direct irradiation studies on LMCs have provided supportive evidence for the involvement of hydrogen abstraction reactions from phenols, beta-cleavage of substituted alpha-aryloxyacetophenones and cleavage of ketyl radicals (formed by photoreduction of aromatic ketones or hydrogen abstraction from arylglycerol beta-aryl ethers) in the photoyellowing of lignin rich pulps. Photosensitized and radiation chemically induced generation of reactive oxygen species and their reaction with LMCs are reviewed. The side-chain reactivity of LMC radical cations, generated by radiation chemical means, is also discussed in relation with the enzymatic degradation of lignin.     

Deformation and degradation of polymers in ultra-high-pressure liquid chromatography

Ultra-high-pressure liquid chromatography (UHPLC) using columns packed with sub-2 μm particles has great potential for separations of many types of complex samples, including polymers. However, the application of UHPLC for the analysis of polymers meets some fundamental obstacles. Small particles and narrow bore tubing in combination with high pressures generate significant shear and extensional forces in UHPLC systems, which may affect polymer chains. At high stress conditions flexible macromolecules may become extended and eventually the chemical bonds in the molecules can break. Deformation and degradation of macromolecules will affect the peak retention and the peak shape in the chromatogram, which may cause errors in the obtained results (e.g. the calculated molecular-weight distributions). In the present work we explored the limitations of UHPLC for the analysis of polymers. Degradation and deformation of macromolecules were studied by collecting and re-injecting polymer peaks and by off-line two-dimensional liquid chromatography. Polystyrene standards with molecular weight of 4 MDa and larger were found to degrade at UHPLC conditions. However, for most polymers degradation could be avoided by using low linear velocities. No degradation of 3-MDa PS (and smaller) was observed at linear velocities up to 7 mm/s. The column frits were implicated as the main sources of polymer degradation. The extent of degradation was found to depend on the type of the column and on the column history. At high flow rates degradation was observed without a column being installed. We demonstrated that polymer deformation preceded degradation. Stretched polymers eluted from the column in slalom chromatography mode (elution order opposite to that in SEC or HDC). Under certain conditions we observed co-elution of large and small PS molecules though a convolution of slalom chromatography and hydrodynamic chromatography.     

A multi-analytical study of degradation of lignin in archaeological waterlogged wood

Historical or archaeological wooden objects are generally better conserved in wet environments than in other contexts. Nevertheless, anaerobic erosion bacteria can slowly degrade waterlogged wood, causing a loss of cellulose and hemicellulose and leading to the formation of water-filled cavities. During this process, lignin can also be altered. The result is a porous and fragile structure, poor in polysaccharides and mainly composed of residual lignin, which can easily collapse during drying and needs specific consolidation treatments. For this reason, the chemical characterization of archaeological lignin is of primary importance in the diagnosis and conservation of waterlogged wood artifacts. Current knowledge of the lignin degradation processes in historical and archaeological wood is extremely inadequate. In this study lignin extracted from archaeological waterlogged wood was examined using both Py-GC/MS, NMR spectroscopy and GPC analysis. The samples were collected from the Site of the Ancient Ships of San Rossore (Pisa, Italy), where since 1998 31 shipwrecks, dating from 2nd century BC to 5th century AD, have been discovered. The results, integrated by GPC analysis, highlight the depolymerization of lignin with cleavage of ether bonds, leading to an higher amount of free phenol units in the lignin from archaeological waterlogged wood, compared to sound lignin from reference wood of the same species.     

Dimeric products of the degradation of cotton lignin and rice hulls

The conditions have been developed for the GLC separation of the dimeric products of the decomposition of lignins, and dehydroisoeugenol and 1-(4-hydroxy-3-methoxyphenyl)-2-(2-methoxyphenoxy)propan-1-ol have been identified.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 93–96, January–February, 1990.     

Stability and degradation of some electrically conducting polymers

The oxidative degradation reactions of polyacetylene, prepared from a soluble precursor polymer, are described and compared with those of more common polymers and of polyacetylene prepared by the conventional method. Because the band structure of the π-electron system of the polymer allows the formation of charge-transfer complexes with oxygen, the initial process in the pristine polymer is oxygen doping, with increasing conductivity. This is followed by irreversible degradation which is much faster than that of polyolefins or polydienes and faster than that of the crystalline polymer. Doping to low levels with electron acceptors removes the electrons involved in oxygen doping and the polymer becomes much more stable in air. Doping to high levels leads to new instabilities as the polymer reacts slowly with its counter-ions. Studies of polypyrrole and polythiophene show that these polymers are much more stable than polyacetylene but still undergo degradation reactions. The general features of their degradation mechanisms are discussed.