Copper is an essential trace element in living systems, present in the parts per million concentration range. It is a key cofactor in a diverse array of biological oxidation-reduction reactions. These involve either outer-sphere electron transfer, as in the blue copper proteins and the Cu{sub A} site of cytochrome oxidase and nitrous oxide redutase, or inner-sphere electron transfer in the binding, activation, and reduction of dioxygen, superoxide, nitrite, and nitrous oxide. Copper sites have historically been divided into three classes based on their spectroscopic features, which reflect the geometric and electronic structure of the active site: type 1 (T1) or blue copper, type 2 (T2) or normal copper, and type 3 (T3) or coupled binuclear copper centers. 428 refs.

Multicopper Oxidases and Oxygenases

Laccases of fungi attract considerable attention due to their possible involvement in the transformation of a wide variety of phenolic compounds including the polymeric lignin and humic substances. So far, more than a 100 enzymes have been purified from fungal cultures and characterized in terms of their biochemical and catalytic properties. Most ligninolytic fungal species produce constitutively at least one laccase isoenzyme and laccases are also dominant among ligninolytic enzymes in the soil environment. The fact that they only require molecular oxygen for catalysis makes them suitable for biotechnological applications for the transformation or immobilization of xenobiotic compounds.

Fungal laccases - occurrence and properties.

In nature, cellulose, lignocellulose and lignin are major sources of plant biomass; therefore, their recycling is indispensable for the carbon cycle. Each polymer is degraded by a variety of microorganisms which produce a battery of enzymes that work synergically. In the near future, processes that use lignocellulolytic enzymes or are based on microorganisms could lead to new, environmentally friendly technologies. This study reviews recent advances in the various biological treatments that can turn these three lignicellulose biopolymers into alternative fuels. In addition, biotechnological innovations based on natural delignification and applied to pulp and paper manufacture are also outlined.

Biodegradation and biological treatments of cellulose, hemicellulose and lignin: an overview

The colonization of land by plants appears to have coincided with the appearance of mycorrhiza-like fungi. Over evolutionary time, fungi have maintained their prominent role in the formation of mycorrhizal associations. In addition, however, they have been able to occupy other terrestrial niches of which the decomposition of recalcitrant organic matter is perhaps the most remarkable. This implies that, in contrast to that of aquatic organic matter decomposition, bacteria have not been able to monopolize decomposition processes in terrestrial ecosystems. The emergence of fungi in terrestrial ecosystems must have had a strong impact on the evolution of terrestrial bacteria. On the one hand, potential decomposition niches, e.g. lignin degradation, have been lost for bacteria, whereas on the other hand the presence of fungi has itself created new bacterial niches. Confrontation between bacteria and fungi is ongoing, and from studying contemporary interactions, we can learn about the impact that fungi presently have, and have had in the past, on the ecology and evolution of terrestrial bacteria. In the first part of this review, the focus is on niche differentiation between soil bacteria and fungi involved in the decomposition of plant-derived organic matter. Bacteria and fungi are seen to compete for simple plant-derived substrates and have developed antagonistic strategies. For more recalcitrant organic substrates, e.g. cellulose and lignin, both competitive and mutualistic strategies appear to have evolved. In the second part of the review, bacterial niches with respect to the utilization of fungal-derived substrates are considered. Here, several lines of development can be recognized, ranging from mutualistic exudate-consuming bacteria that are associated with fungal surfaces to endosymbiotic and mycophagous bacteria. In some cases, there are indications of fungal specific selection in fungus-associated bacteria, and possible mechanisms for such selection are discussed.

Living in a fungal world: impact of fungi on soil bacterial niche development⋆

This review focuses on some important and challenging aspects of soil extracellular enzyme research. We report on recent discoveries, identify key research needs and highlight the many opportunities offered by interactions with other microbial enzymologists. The biggest challenges are to understand how the chemical, physical and biological properties of soil affect enzyme production, diffusion, substrate turnover and the proportion of the product that is made available to the producer cells. Thus, the factors that regulate the synthesis and secretion of extracellular enzymes and their distribution after they are externalized are important topics, not only for soil enzymologists, but also in the broader context of microbial ecology. In addition, there are many uncertainties about the ways in which microbes and their extracellular enzymes overcome the generally destructive, inhibitory and competitive properties of the soil matrix, and the various strategies they adopt for effective substrate detection and utilization. The complexity of extracellular enzyme activities in depolymerising macromolecular organics is exemplified by lignocellulose degradation and how the many enzymes involved respond to structural diversity and changing nutrient availabilities. The impacts of climate change on microbes and their extracellular enzymes, although of profound importance, are not well understood but we suggest how they may be predicted, assessed and managed. We describe recent advances that allow for the manipulation of extracellular enzyme activities to facilitate bioremediation, carbon sequestration and plant growth promotion. We also contribute to the ongoing debate as to how to assay enzyme activities in soil and what the measurements tell us, in the context of both traditional methods and the newer techniques that are being developed and adopted. Finally, we offer our collective vision of the future of extracellular enzyme research: one that will depend on imaginative thinking as well as technological advances, and be built upon synergies between diverse disciplines.

Soil enzymes in a changing environment: Current knowledge and future directions

Nocardia autotrophica was grown in a medium containing ferulic acid and 14C-ferulic acid, labelled in various parts of a particle as a main carbon source. After incubation, the products were analyzed by thin layer, high performance liqid and gas chromatography and by IR and NMR spectra methods. The products detected were caffeic acid, catechol, coniferyl alcohol, eugenol, guaiacol, hydrocaffeic acid, isoeugenol, isoferulic acid, isovanillic acid, p-hydroxybenzoic acid, protocatechuic acid and aldehyde, vanillic acid, and vinylguaiacol. A liberation of 14CO2 during cultivation was noticed.

Transformation of ferulic acid by soil bacteria Nocardia provides various valuable phenolic compounds

Fungal laccases from Trametes hirsuta and Cerrena unicolor were immobilized on spectroscopic graphite electrodes using physical absorption. The laccase-modified graphite electrodes were mounted as ...

Characterization of graphite electrodes modified with laccases from Trametes hirsuta and Cerrena unicolor and their use for flow injection amperometric determination of some phenolic compounds

The influence of cadmium chloride and/or high temperature on the level of selected parameters were examined in both medium and mycelium of some Basidiomycetes belonging to white-rot fungi: Abortiporus biennis, Trametes versicolor and Cerrena unicolor. We investigated changes in the formaldehyde (FA) level and in the level of superoxide radical anions (SR). Accordingly, the capacity of three enzymes was also studied: two enzymes of the cellular antioxidative system — superoxide dismutase (SOD; EC 1.15.1.1), and catalase (CAT; EC 1.11.1.6), and laccase (LAC; EC 1.10.3.2) — the main lignin-modifying enzyme, which is produced by white-rot fungi. During the first 24 hours after application of separate stressors, or jointly with two stressors to 10-day-old cultivation, changes in all selected parameters were observed. Moreover, we found significant changes in the levels of extracellular SR, FA and extra- and intracellular activity of LAC. Simultaneous action of two stressors in the fungal cultures decreased the extracellular LAC level, intracellular CAT activity and the level of SR in the medium compared to the control values, while using the two stress factors separately would strongly make these values increase. Stressful conditions brought a rapid increase in the level of FA in all fungal species. The results of our study, carried out on selected strains of Basidiomycetes, seem to have shown that: (1) LAC, the lignin-modifying enzyme, may have an important application in fungal stress response, and take part in the cross-protection between responses to heat shock and cadmium resistance; (2) the oxidative burst as a result of cadmium and high temperature treatment is an additional factor to damage fungal cells; (3) FA may be a determining factor in the phases of fungal stress syndrome.

Formaldehyde as a proof and response to various kind of stress in some Basidiomycetes.

The effect of coniferyl alcohol on removal of chlorinated phenols from a water environment byRhizoctonia praticola andCerrena unicolor laccases was studied. At optimal conditions in which 7 mM coniferyl alcohol and laccase were added to chlorinated phenols over 20h, about 34% of the radioactivity of 4-chlorophenol, 57% of 2,4-dichlorophenol, 66% of 2,4,5-trichlorophenol, and 85% of pentachlorophenol were removed from the supernatants, compared to the level without laccase activity. After 12-h incubation periods at the optimal concentrations of coniferyl alcohol and laccase (added simultaneously), the fast first phase of chlorophenol removal was complete in 1 h, and eventually coniferyl alcohol enhanced the removal of 4-chlorophenol by 40%, 2,4-dichlorophenol by 54%, 2,4,5-trichlorophenol by 60%, and pentachlorophenol by 76%.

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Effect of coniferyl alcohol addition on removal of chlorophenols from water effluent by fungal laccase

/pdf/effect-of-various-compounds-on-the-activity-of-laccases-from-4kr4o3jmpb.pdf

Andrzej Leonowicz

Papers

Transformation of ferulic acid by soil bacteria Nocardia provides various valuable phenolic compounds

Characterization of graphite electrodes modified with laccases from Trametes hirsuta and Cerrena unicolor and their use for flow injection amperometric determination of some phenolic compounds

Formaldehyde as a proof and response to various kind of stress in some Basidiomycetes.

Effect of coniferyl alcohol addition on removal of chlorophenols from water effluent by fungal laccase

Effect of various compounds on the activity of laccases from Basidiomycetes and their oxidative and demethoxylating activities