O. Rubilar

Transformation of Chlorinated Phenolic Compounds by White Rot Fungi

Chlorinated phenolic compounds are among the most abundant recalcitrant wastes produced by the paper and pulp industry, being accumulated in the effluents after secondary treatments. Due to their high toxicity to a wide range of organisms, chlorinated phenolic compounds pose a big concern to human and environmental health. These compounds are produced upon the partial degradation of lignin during bleaching process, and as such they are degradable by white rot fungi, the only organisms capable of degrading lignin to CO2 and H2O. White rot fungi are a group of organisms very suitable for the removal of chlorinated phenolic compounds from the environment. Indeed, they are robust, ubiquitous organisms and may survive also in the presence of high concentrations of various pollutants, even with a low bioavailability. The activity of white rot fungi is mainly due to the action of oxidoreductive enzymes, i.e., laccase, manganese peroxidase and lignin peroxidase, which are deliberately released by fungal cells into their nearby environment. In cases of secondary metabolism and oxidative stress, the fungi produce other intra- and extracellular enzymes to provide substrates for the key enzymes just mentioned. Phanerochaete chrysosporium is one of the most widely studied fungi, for which intermediary products and reactions involved in the degradation of chlorophenols have been identified. Extracellular laccases and peroxidases carry out the first productive step in the oxidation of chlorophenols, forming para-quinones and consequently releasing a chlorine atom. Further degradative steps involving several enzymes and highly reactive, nonspecific redox mediators produced by the fungus render it capable of efficiently degrading several toxic compounds. In soil environment, chlorophenols may be involved in physical–chemical processes such as polymerization and/or adsorption of/on humic substances that may hinder their degradation by microbial cells, even though both processes can result in dehalogenation of the chlorinated compounds. This review analyzes the presence of chlorophenols in the environment, their main chemical and physical properties, and the main processes in their degradation by white rot fungi with particular attention to soil environment. The reactions involved in the process, the intermediary products, the factors that may affect the fungal transformation of chlorophenols, and the possible applications for environmental purposes of both the whole fungal cells and/or their enzymes as isolated catalytic agents are also addressed.

Biogenic nanoparticles: copper, copper oxides, copper sulphides, complex copper nanostructures and their applications.

Copper nanoparticles have been the focus of intensive study due to their potential applications in diverse fields including biomedicine, electronics, and optics. Copper-based nanostructured materials have been used in conductive films, lubrification, nanofluids, catalysis, and also as potent antimicrobial agent. The biogenic synthesis of metallic nanostructured nanoparticles is considered to be a green and eco-friendly technology since neither harmful chemicals nor high temperatures are involved in the process. The present review discusses the synthesis of copper nanostructured nanoparticles by bacteria, fungi, and plant extracts, showing that biogenic synthesis is an economically feasible, simple and non-polluting process. Applications for biogenic copper nanoparticles are also discussed.

Bioremediation of soil contaminated with pentachlorophenol by Anthracophyllum discolor and its effect on soil microbial community.

Bioaugmentation is a promising technology to clean up sites contaminated with recalcitrant chemicals. White-rot fungi have proven to be effective in the degradation of pentachlorophenol. Here, we report the bioremediation of soil contaminated with pentachlorophenol (PCP) by Anthracophyllum discolor and its impact on the soil microbial community. In this study three types of microcosms were established: fresh soil (C(0)), fresh soil plus wheat straw (WS(0)) and, fresh soil plus wheat straw inoculated with A. discolor (WSAD(0)). Additionally, similar treatments and a control of sterile soil spiked with PCP (C(250), WS(250) and WSAD(250)) were used to evaluate the remediation and adsorption of PCP. The PCP removal, total microbial activity, and enzymatic activities were evaluated. This study also investigated the structure of soil microbial community by denaturing gradient gel electrophoresis (DGGE), identifying some of the dominant bacterial and fungal species. The results showed that PCP was effectively degraded in soils by A. discolor and by indigenous soil microorganisms. The addition of wheat straw increased the PCP degradation and enzymatic activities. Only laccase activity was negatively affected by PCP contamination. The PCP degradation was associated with changes in microbial communities, mainly stimulation of members of bacterial phylum Proteobacteria (Xanthomonadaceae, Burkholderiaceae and Enterobacteriaceae), and fungal phylum Ascomycota and Basidiomycota. This study shows the ability of A. discolor to degrade PCP from contaminated soil, and demonstrates that agricultural residues, such as wheat straw, can be used as growth substrate by microorganisms in PCP-contaminated soil, demonstrating a great potential of autochthonous microorganisms for soil remediation.

Chlorpyrifos degradation in a biomixture of biobed at different maturity stages

The biomixture is a principal element controlling the degradation efficacy of the biobed. The maturity of the biomixture used in the biobed affects its overall performance of the biobed, but this is not well studied yet. The aim of this research was to evaluate the effect of using a typical composition of Swedish biomixture at different maturity stages on the degradation of chlorpyrifos. Tests were made using biomixture at three maturity stages: 0 d (BC0), 15 d (BC15) and 30 d (BC30); chlorpyrifos was added to the biobeds at final concentration of 200, 320 and 480 mg kg(-1). Chlorpyrifos degradation in the biomixture was monitored over time. Formation of TCP (3,5,6-trichloro-2-pyrinidol) was also quantified, and hydrolytic and phenoloxidase activities measured. The biomixture efficiently degraded chlorpyrifos (degradation efficiency >50%) in all the evaluated maturity stages. However, chlorpyrifos degradation decreased with increasing concentrations of the pesticide. TCP formation occurred in all biomixtures, but a major accumulation was observed in BC30. Significant differences were found in both phenoloxidase and hydrolytic activities in the three maturity stages of biomixture evaluated. Also, these two biological activities were affected by the increase in pesticide concentration. In conclusion, our results demonstrated that chlorpyrifos can be degraded efficiently in all the evaluated maturity stages.

Atrazine dissipation and its impact on the microbial communities and community level physiological profiles in a microcosm simulating the biomixture of on-farm biopurification system

The effects of repeated atrazine application (40 mg a.i.kg(-1)) on its degradation, microbial communities and enzyme activities were studied in a peat based biomixture composed by straw, soil and peat in the volumetric proportions of 2:1:1 that can be used in on-farm biopurification system. Atrazine removal efficiency was high (96%, 78% and 96%) after each atrazine application and did not show a lag phase. Microbial enzyme activities were reduced significantly with atrazine application but rapidly recovered. Microbial diversity obtained by BiologEcoplate was similar after the first and second atrazine application. However, an inhibitory effect was observed after the third application. After each atrazine application, culturable fungi were reduced, but rapidly recovered without significant changes in culturable bacteria and actinomycetes compared to the control. Denaturing gradient gel electrophoresis (DGGE) patterns demonstrated that microbial community structure remained relatively stable in time when compared to the controls. In conclusion, our results demonstrated that after successive ATZ applications, the peat based biomixture had a good degradation capacity. Moreover, microbiological assays demonstrated the robustness of the peat based biomixture from a microbiological point of view to support pesticide degradation.

Carbendazim dissipation in the biomixture of on-farm biopurification systems and its effect on microbial communities.

The impact of repeated carbendazim (CARB) applications on the extent of CARB dissipation, the microbial diversity, the community level physiological profile (CLPP), and the enzymatic activity within the biomixture of an on-farm biopurification system was evaluated. After three successive CARB applications, the CARB dissipation efficiency was high; the efficiency of dissipation was 87%, 94% and 96% after each application, respectively. Although microbial enzymatic activity was affected significantly by CARB application, it could recover after each CARB pulse. Likewise, the numbers of cultivable bacteria, fungi and actinomycetes (as measured in CFUs) were slightly affected by the addition of CARB, but the inhibitory effect of the pesticide application was temporary. Denaturing gradient gel electrophoresis (DGGE) and Biolog Ecoplate assays demonstrated that the microbial populations remained relatively stable over time when compared to the control. The results obtained herein therefore demonstrate the high dissipation capacity of this biomixture and highlight the microbiological robustness of this biological system.

Extracellular biosynthesis of copper and copper oxide nanoparticles by Stereum hirsutum , a native white-rot fungus from Chilean forests

The white-rot fungus Stereum hirsutum was studied to evaluate its applicability for use in the biosynthesis of copper/copper oxide nanoparticles under different pHconditions and in the presence of three different copper salts (CuCl2, CuSO4, and Cu(NO3)2). The nanoparticle formation was evaluated by UV-visible spectroscopy, electron microscopy (TEM), X-ray diffraction analysis (XRD), and Fourier transforms infrared spectroscopy (FTIR). The nanoparticles biosynthesis in presence of all copper salts demonstrated higher formation with 5 mM CuCl2 under alkaline conditions. TEM analysis confirmed that the nanoparticles were mainly spherical (5 to 20 nm). The presence of amine groups attached to nanoparticles was confirmed by FTIR, which suggests that extracellular protein of fungus is responsible for the formation of the nanoparticles. Therefore, the white-rot fungus S. hirsutum was found to exhibit potential for use in the synthesis of copper/copper oxide nanoparticles.

BIOSTIMULATION OF AGRICULTURAL BIOBEDS WITH NPK FERTILIZER ON CHLORPYRIFOS DEGRADATION TO AVOID SOIL AND WATER CONTAMINATION

Degradation of the insecticide chlorpyrifos (160 a.i mg kg -1 ) using a biomix of a biobed system biostimulated with inorganic fertilizer (NPK) was investigated. Three concentrations of the fertilizer (0.1%, 0.5% and 1.0% ww -1 ) were evaluated on chlorpyrifos degradation, TCP (3, 5, 6-trichloro-2-pyrinidol) accumulation and biological activity of the biomix. The chlorpyrifos was dissipated efficiently (>75%) after 40 days of incubation and no additional dissipation was obtained with increasing concentration of NPK after 20 days of incubation. TCP accumulation occurred in all evaluated NPK concentrations and its concentration increased with the increment of NPK addition raising the probability of leaching of this compound. Biological activity (FDA and ligninolytic enzyme activity) in the biomix increased by the NPK presence in all evaluated concentrations. The DGGE analyses showed that combined treatments with lower amounts of NPK (0% and 0.1%) and chlorpyrifos showed no significant modifications in the microbial community in the biomix. However, combined overdoses of NPK (0.5 and 1.0%) and chlorpyrifos caused significant modifications in the bacterial communities that could be associated with TCP degradation reduction in the biomix. In conclusion, the obtained results demonstrated that the biomix prepared with Andisol and biostimulated with NPK nutrient can be recommended in biobeds as a viable alternative of chlorpyrifos dissipation avoiding soil and water contamination probability.

Are white-rot fungi a real biotechnological option for the improvement of environmental health?

Abstract The use of white-rot fungi as a biotechnological tool for cleaning the environment of recalcitrant pollutants has been under evaluation for several years. However, it is still not possible to find sufficiently detailed investigations of this subject to conclude that these fungi can decontaminate the environment. In the present review, we have summarized and discussed evidence about the potential of white-rot fungi to degrade such pollutants as polycyclic aromatic hydrocarbons, dyes or antibiotics as an example of the complex structures that these microorganisms can attack. This review also discusses field experiment results and limitations of white-rot fungi trials from contaminated sites. Moreover, the use of catabolic potential of white-rot fungi in biopurification systems (biobeds) is also discussed. The current status and future perspectives of white-rot fungi, as a viable biotechnological alternative for improvement of environmental health are noted.

Performance of an enzymatic extract in Botrycoccus braunii cell wall disruption.

Microalgae can produce and contain lipids, proteins and carbohydrates, which can be extracted and marketed as potential novel added-value bio-products. However, microalgae cell wall disruption is one of the most important challenges involved while processing this type of biomass. In this context, white-rot fungi, responsible for the biodegradation of lignin present in wood due to non-specific extracellular enzymes, could be applied for promoting microalgae cell wall degradation. Therefore, the aim of this study was to evaluate the use of an enzymatic extract produced by the white-rot fungi Anthracophyllum discolor as a biotechnological tool for Botryococcus braunii cell wall disruption. The fungus was inoculated in wheat grains and manganese peroxidase (MnP) activity was monitored while obtaining the enzymatic extract. Then, cell wall disruption trials with different MnP activity were evaluated by the biochemical methane potential (BMP). In relation to cell wall disruption, it was observed that the optimal value was obtained with enzymatic concentration of 1000 U/L with a BMP of 521 mL CH4/g VS. Under these conditions almost 90% of biomass biodegradability was observed, increasing in 62% compared to the microalgae without treatment. Therefore, the results indicate that enzymes secreted by A. discolor promoted the attack of the different cell wall components finally weakening it. Therefore, the application of this treatment could be a promissory biotechnological approach to decrease the energetic input required for the cell wall disruption step.