Formulation of essential oils-loaded solid lipid nanoparticles-based chitosan/PVA hydrogels to control the growth of Botrytis cinerea and Penicillium expansum

Botrytis cinerea and Penicillium expansum are phytopathogenic fungi that produce the deterioration of fruits. Thus, essential oil (EO) has emerged as a sustainable strategy to minimize the use of synthetic fungicides, but their volatility and scarce solubility restrict their application. This study proposes the EO of Oreganum vulgare and Thymus vulgaris-loaded solid lipid nanoparticles (SLN) based chitosan/PVA hydrogels to reduce the infestation of fungi phytopathogen. EO of O. vulgare and T. vulgaris-loaded SLN had a good homogeneity (0.21-0.35) and stability (-28.8 to -33.0 mV) with a mean size of 180.4-188.4 nm. The optimization of EO-loaded SLN showed that the encapsulation of 800 and 1200 μL L-1 of EO of O vulgare and T. vulgaris had the best particle size. EO-loaded SLN significantly reduced the mycelial growth and spore germination of both fungi pathogen. EO-loaded SLN into hydrogels showed appropriate physicochemical characteristics to apply under environmental conditions. Furthermore, rheological analyses evidenced that hydrogels had solid-like characteristics and elastic behavior. EO-loaded SLN-based hydrogels inhibited the spore germination in B. cinerea (80.9 %) and P. expansum (55.7 %). These results show that SLN and hydrogels are eco-friendly strategies for applying EO with antifungal activity.

The Catalytic Role of Superparamagnetic Iron Oxide Nanoparticles as a Support Material for TiO2 and ZnO on Chlorpyrifos Photodegradation in an Aqueous Solution

Chlorpyrifos (CP) is a globally used pesticide with acute toxicity. This work studied the photocatalytic degradation of CP using TiO2, ZnO nanoparticles, and nanocomposites of TiO2 and ZnO supported on SPIONs (SPION@SiO2@TiO2 and SPION@SiO2@ZnO). The nanocomposites were synthesized by multi-step incipient wetness impregnation. The effects of the initial pH, catalyst type, and dose were evaluated. The nanocomposites of SPION@SiO2@TiO2 and SPION@SiO2@ZnO showed higher CP photodegradation levels than free nanoparticles, reaching 95.6% and 82.3%, respectively, at pH 7. The findings indicate that iron oxide, as a support material for TiO2 and ZnO, extended absorption edges and delayed the electron-hole recombination of the nanocomposites, improving their photocatalytic efficiency. At the same time, these nanocomposites, especially SPION@SiO2@TiO2, showed efficient degradation of 3,5,6-trichloropyridinol (TCP), one of the final metabolites of CP. The stability and reuse of this nanocomposite were also evaluated, with 74.6% efficiency found after six cycles. Therefore, this nanomaterial represents an eco-friendly, reusable, and effective alternative for the degradation of chlorpyrifos in wastewater treatment.

The efficient activity of plant essential oils for inhibiting Botrytis cinerea and Penicillium expansum: Mechanistic insights into antifungal activity

Botrytis cinerea and Penicillium expansum produce deterioration in fruit quality, causing losses to the food industry. Thus, plant essential oils (EOs) have been proposed as a sustainable alternative for minimizing the application of synthetic fungicides due to their broad-spectrum antifungal properties. This study investigated the efficacy of five EOs in suppressing the growth of B. cinerea and P. expansum and their potential antifungal mechanisms. EOs of Mentha × piperita L., Origanum vulgare L., Thymus vulgaris L., Eucalyptus globules Labill., and Lavandula angustifolia Mill., were screened for both fungi. The results showed that the EO of T. vulgaris and O. vulgare were the most efficient in inhibiting the growth of B. cinerea and P. expansum. The concentration increase of all EO tested increased fungi growth inhibition. Exposure of fungi to EOs of T. vulgaris and O. vulgare increased the pH and the release of constituents absorbing 260 nm and soluble proteins, reflecting membrane permeability alterations. Fluorescence microscopic examination revealed that tested EOs produce structural alteration in cell wall component deposition, decreasing the hypha width. Moreover, propidium iodide and Calcein-AM stains evidenced the loss of membrane integrity and reduced cell viability of fungi treated with EOs. Fungi treated with EOs decreased the mitochondria activity and the respiratory process. Therefore, these EOs are effective antifungal agents against B. cinerea and P. expansum, which is attributed to changes in the cell wall structure, the breakdown of the cell membrane, and the alteration of the mitochondrial activity.

Metabolic Profiling and Comparative Proteomic Insight in Respect of Amidases during Iprodione Biodegradation

The fungicide iprodione (IPR) (3-(3,5-dichlorophenyl) N-isopropyl-2,4-dioxoimidazolidine-1-carboxamide) is a highly toxic compound. Although IPR has been restricted, it is still being applied in many places around the world, constituting an environmental risk. The biodegradation of IPR is an attractive option for reducing its residues. In this study, we isolated thirteen IPR-tolerant bacteria from a biopurification system designed to treat pesticides. A study of biodegradation using different strains was comparatively evaluated, and the best degradation rate of IPR was presented by Achromobacter sp. C1 with a half-life (T1/2) of 9 days. Based on a nano-LC-MS/MS analysis for the strains, proteins solely expressed in the IPR treatment were identified by highlighting the strain Achromobacter sp. C1, with 445 proteins primarily involved in the biosynthesis of secondary metabolites and microbial metabolism in diverse environments. Differentially expressed protein amidases were involved in six metabolic pathways. Interestingly, formamidase was inhibited while other cyclases, i.e., amidase and mandelamide hydrolase, were overexpressed, thereby minimizing the effect of IPR on the metabolism of strain C1. The dynamic changes in the protein profiles of bacteria that degrade IPR have been poorly studied; therefore, our results offer new insight into the metabolism of IPR-degrading microorganisms, with special attention paid to amidases.

The Impact of 2-Ketones Released from Solid Lipid Nanoparticles on Growth Modulation and Antioxidant System of Lactuca sativa

2-Ketones are signal molecules reported as plant growth stimulators, but their applications in vegetables have yet to be achieved. Solid lipid nanoparticles (SLNs) emerge as a relevant nanocarrier to develop formulations for the controlled release of 2-ketones. In this sense, seedlings of Lactuca sativa exposed to 125, 375, and 500 µL L-1 of encapsulated 2-nonanone and 2-tridecanone into SLNs were evaluated under controlled conditions. SLNs evidenced a spherical shape with a size of 230 nm. A controlled release of encapsulated doses of 2-nonanone and 2-tridecanone was observed, where a greater release was observed as the encapsulated dose of the compound increased. Root development was strongly stimulated mainly by 2-tridecanone and leaf area (25-32%) by 2-nonanone. Chlorophyll content increased by 15.8% with exposure to 500 µL L-1 of 2-nonanone, and carotenoid concentration was maintained with 2-nonanone. Antioxidant capacity decreased (13-62.7%) in L. sativa treated with 2-ketones, but the total phenol concentration strongly increased in seedlings exposed to some doses of 2-ketones. 2-Tridecanone strongly modulates the enzymatic activities associated with the scavenging of H2O2 at intra- and extracellular levels. In conclusion, 2-ketones released from SLNs modulated the growth and the antioxidant system of L. sativa, depending on the dose released.

Eco-Efficient Systems Based on Nanocarriers for the Controlled Release of Fertilizers and Pesticides: Toward Smart Agriculture

The excessive application of pesticides and fertilizers has generated losses in biological diversity, environmental pollution, and harmful effects on human health. Under this context, nanotechnology constitutes an innovative tool to alleviate these problems. Notably, applying nanocarriers as controlled release systems (CRSs) for agrochemicals can overcome the limitations of conventional products. A CRS for agrochemicals is an eco-friendly strategy for the ecosystem and human health. Nanopesticides based on synthetic and natural polymers, nanoemulsions, lipid nanoparticles, and nanofibers reduce phytopathogens and plant diseases. Nanoproducts designed with an environmentally responsive, controlled release offer great potential to create formulations that respond to specific environmental stimuli. The formulation of nanofertilizers is focused on enhancing the action of nutrients and growth stimulators, which show an improved nutrient release with site-specific action using nanohydroxyapatite, nanoclays, chitosan nanoparticles, mesoporous silica nanoparticles, and amorphous calcium phosphate. However, despite the noticeable results for nanopesticides and nanofertilizers, research still needs to be improved. Here, we review the relevant antecedents in this topic and discuss limitations and future challenges.

Nanotechnology advances for sustainable agriculture: current knowledge and prospects in plant growth modulation and nutrition

Advances in nanotechnology make it an important tool for improving agricultural production. Strong evidence supports the role of nanomaterials as nutrients or nanocarriers for the controlled release of fertilizers to improve plant growth. Scientific research shows that nanotechnology applied in plant sciences is smart technology. Excessive application of mineral fertilizers has produced a harmful impact on the ecosystem. Furthermore, the projected increase in the human population by 2050 has led to the search for alternatives to ensure food security. Nanotechnology is a promising strategy to enhance crop productivity while minimizing fertilizer inputs. Nanofertilizers can contribute to the slow and sustainable release of nutrients to improve the efficiency of nutrient use in plants. Nanomaterial properties (i.e., size, morphology and charge) and plant physiology are crucial factors that influence the impact on plant growth. An important body of scientific research highlights the role of carbon nanomaterials, metal nanoparticles and metal oxide nanoparticles to improve plant development through the modulation of physiological and metabolic processes. Modulating nutrient concentrations, photosynthesis processes and antioxidant enzyme activities have led to increases in shoot length, root development, photosynthetic pigments and fruit yield. In parallel, nanocarriers (nanoclays, nanoparticles of hydroxyapatite, mesoporous silica and chitosan) have been shown to be an important tool for the controlled and sustainable release of conventional fertilizers to improve plant nutrition; however, the technical advances in nanofertilizers need to be accompanied by modernization of the regulations and legal frameworks to allow wider commercialization of these elements. Nanofertilizers are a promising strategy to improve plant development and nutrition, but their application in sustainable agriculture remains a great challenge. The present review summarizes the current advance of research into nanofertilizers, and their future prospects.

Enzyme activities and microbial functional diversity in metal(loid) contaminated soils near to a copper smelter

The monitoring of soil metal(loid) contamination is of global significance due to deleterious effects that metal(loid)s have on living organisms. Soil biological properties such as enzyme activities (EAs) are good indicators of metal(loid) contamination due to their high sensitivity, fast response, and low-cost. Here, the effect of metal(loid) contamination on physicochemical properties and microbial functionality in soils sampled from within 10 km of a Cu smelter is investigated. Soil composite samples were randomly taken within 2, 4, 6, 8 and10 km zones from a mining industry Cu smelter. The EAs of dehydrogenase (DHA), arylsulfatase (ARY), β-glucosidase, urease, and arginine ammonification (AA) were studied as indicators of metal(loid) contamination, which included the ecological dose (ED₅₀) with respect to Cu and As contents. The community level physiological profile (CLPP), functional diversity, and catabolic evenness were evaluated based on the C-substrate utilisation. All EAs decreased in zones with high degrees of metal(loid) contamination, which also had low TOC and clay contents, reflecting long term processes of soil degradation. Positive and strong relationships between EAs and TOC were found. DHA and ARY activities decreased by approximately 85-90% in highly metal(loid) contaminated soils. DHA and AA showed significant ED₅₀ values associated with available Cu (112.8 and 121.6 mg Cu_DTPA kg^-1, respectively) and total As contents (30.8 and 31.8 mg As kg^-1, respectively). The CLPP showed different metabolic profiles along the metal(loid) contamination gradients. Long-term stress conditions in soils close to industrial areas resulted in the decreasing of general biological activity, catabolic capacity, and functional diversity.

Silver, copper and copper oxide nanoparticles in the fight against human viruses: progress and perspectives

The rapid development of nanomedicine has created a high demand for silver, copper and copper oxide nanoparticles. Due to their high reactivity and potent antimicrobial activity, silver and copper-based nanomaterials have been playing an important role in the search for new alternatives for the treatment of several issues of concern, such as pathologies caused by bacteria and viruses. Viral diseases are a significant and constant threat to public health. The most recent example is the pandemic caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). In this context, the object of the present review is to highlight recent progress in the biomedical uses of these metal nanoparticles for the treatment and prevention of human viral infections. We discuss the antiviral activity of AgNPs and Cu-based NPs, including their actions against SARS-CoV-2. We also discuss the toxicity, biodistribution and excretion of AgNPs and CuNPs, along with their uses in medical devices or on inert surfaces to avoid viral dissemination by fomites. The challenges and limitations of the biomedical use of these nanoparticles are presented.

Bioconversion of potato solid waste into antifungals and biopigments using Streptomyces spp

Potato waste was processed and used as a sole substrate for simultaneously producing antifungals and biopigments using Streptomyces spp. Out of three different Streptomyces isolates, strain SO6 stood out due to its ability to produce antifungals against economically important fungal phytopathogens and intracellular biopigments using potato waste powders without additional nutrients. This strain also showed the potential to secrete a broad range of enzymes for fermentation of eight sugars that could be involved in potato waste bioconversion. The results of the fermentation assay indicated that Streptomyces sp. strain SO6 degrades potato wastes during submerged fermentation, diminishing total dry weight and increasing reducing sugars from 0.3 to 3.6 mg·mL⁻¹ and total proteins from 70.6 to 187.7 μg·mL⁻¹. The results showed that Streptomyces strain SO6 was able to convert the potato waste into 0.96 mg·g⁻¹ of diffusible antifungals and 1.75 mg·g⁻¹ of reddish-purple biopigments. On the contrary, an absence of pigment production was observed during the fermentation of the commercial medium used as reference. According to our results, replacement of commercial culture media with available low-cost agroindustrial wastes for producing bioactive chemicals is a real opportunity to enhance the Streptomyces pigment production and antibiotic sustainability with cost-competitiveness. To our knowledge, this is the first report on the simultaneous production of biopigments and diffusible antifungal antibiotics produced by Streptomyces spp. using potato solid waste as the sole nutrient source.

Advanced Material Against Human (Including Covid-19) and Plant Viruses: Nanoparticles As a Feasible Strategy

The SARS-CoV-2 virus outbreak revealed that these nano-pathogens have the ability to rapidly change lives. Undoubtedly, SARS-CoV-2 as well as other viruses can cause important global impacts, affecting public health, as well as, socioeconomic development. But viruses are not only a public health concern, they are also a problem in agriculture. The current treatments are often ineffective, are prone to develop resistance, or cause considerable adverse side effects. The use of nanotechnology has played an important role to combat viral diseases. In this review three main aspects are in focus: first, the potential use of nanoparticles as carriers for drug delivery. Second, its use for treatments of some human viral diseases, and third, its application as antivirals in plants. With these three themes, the aim is to give to readers an overview of the progress in this promising area of biotechnology during the 2017-2020 period, and to provide a glance at how tangible is the effectiveness of nanotechnology against viruses. Future prospects are also discussed. It is hoped that this review can be a contribution to general knowledge for both specialized and non-specialized readers, allowing a better knowledge of this interesting topic.

Current advances in plant-microbe communication via volatile organic compounds as an innovative strategy to improve plant growth

Volatile organic compounds (VOCs) emitted by microorganisms have demonstrated an important role to improve growth and tolerance against abiotic stress on plants. Most studies have used Arabidopsis thaliana as a model plant, extending to other plants of commercial interest in the last years. Interestingly, the microbial VOCs are characterized by its biodegradable structure, quick action, absence of toxic substances, and acts at lower concentration to regulate plant physiological changes. These compounds modulate plant physiological processes such as phytohormone pathways, photosynthesis, nutrient acquisition, and metabolisms. Besides, the regulation of gene expression associated with cell components, biological processes, and molecular function are triggered by microbial VOCs. Otherwise, few studies have reported the important role of VOCs for confer plant tolerance to abiotic stress, such as drought and salinity. Although VOCs have shown an efficient action to enhance the plant growth under controlled conditions, there are still great challenges for their greenhouse or field application. Therefore, in this review, we summarize the current knowledge about the technical procedures, study cases, and physiological mechanisms triggered by microbial VOCs to finally discuss the challenges of its application in agriculture.

Pesticide-tolerant bacteria isolated from a biopurification system to remove commonly used pesticides to protect water resources

In this study, we selected and characterized different pesticide-tolerant bacteria isolated from a biomixture of a biopurification system that had received continuous applications of a pesticides mixture. The amplicon analysis of biomixture reported that the phyla Proteobacteria, Firmicutes, Bacteroidetes and Actinobacteria were predominant. Six strains grew in the presence of chlorpyrifos and iprodione. Biochemical characterization showed that all isolates were positive for esterase, acid phosphatase, among others, and they were identified as Pseudomonas, Rhodococcus and Achromobacter based on molecular and proteomic analysis. Bacterial growth decreased as both pesticide concentrations increased from 10 to 100 mg L^-1 in liquid culture. The Achromobacter sp. strain C1 showed the best chlorpyrifos removal rate of 0.072–0.147 d^-1 a half-life of 4.7–9.7 d and a maximum metabolite concentration of 2.10 mg L^-1 at 120 h. On the other hand, Pseudomonas sp. strain C9 showed the highest iprodione removal rate of 0.100–0.193 d^-1 a half-life of 4–7 d and maximum metabolite concentration of 0.95 mg L^-1 at 48 h. The Achromobacter and Pseudomonas strains showed a good potential as chlorpyrifos and iprodione-degrading bacteria.

Performance of a continuous stirred tank bioreactor employing an immobilized actinobacteria mixed culture for the removal of organophosphorus pesticides

In this study, we evaluated polyurethane foam (PF), volcanic rock (VR), and a modified plastic cap (MPC) as supports for the immobilization of organophosphorus (OP) pesticide-degrading actinobacterial strains. The colonization and activity of four streptomycetes were favoured by PF, which was selected as the carrier to use in a continuous stirred tank bioreactor (CSTR) that can be operated at increasing inflows of a pesticide mixture that contains the insecticides chlorpyrifos (CP) and diazinon (DZ). Our results demonstrate that the CSTR can be operated at flow rates of 10 and 40 mL h^-1 with greater than 85% removal of the pesticides in the short term. A significant decrease in the efficiency of CP removal was observed at the highest inflows into the reactor. The CP and DZ loading rates in the bioreactor ranged from 0.44 to 1.68 mg L^-1 h^-1 and from 0.50 to 2.17 mg L^-1 h^-1, respectively. Although the treated wastewater exhibited moderate toxicity for Raphanus sativus, a bioreactor inoculated with a mixed culture formed by Streptomyces spp. strains AC5, AC9, GA11 and ISP13 may provide an effective biotechnological strategy for the reduction of OP pesticide residues produced during agronomic and manufacturing practices and therefore prevent environmental pesticidal pollution.

Silver nanoparticles: Toxicity in model organisms as an overview of its hazard for human health and the environment

Silver nanoparticles (AgNPs) have attracted remarkable attention due to their powerful antimicrobial action as well as their particular physicochemical properties. This has led to their application in a wide variety of products with promising results. However, their interaction with the environment and toxicity in live terrestrial or aquatic organisms is still a matter of intense debate. More detailed knowledge is still required about the toxicity of AgNPs, their possible uptake mechanisms and their adverse effects in live organisms. Several studies have reported the interactions and potential negative effects of AgNPs in different organisms. In this review, we report and discuss the current state of the art and perspectives for the impact of AgNPs on different organisms present in the environment. Recent progress in interpreting uptake, translocation and accumulation mechanisms in different organisms and/or living animals are discussed, as well as the toxicity of AgNPs and possible tolerance mechanisms in live organisms to cope with their deleterious effects. Finally, we discuss the challenges of accurate physicochemical characterization of AgNPs and their ecotoxicity in environmentally realistic conditions such as soil and water media.

Biodegradation inducers to enhance wheat straw pretreatment by Gloeophyllum trabeum to second-generation ethanol production

The native state of lignocellulosic biomass is highly resistant to enzymatic hydrolysis and the fermentation process of biofuel production. Brown-rot fungi use an extracellular Fenton system to degrade lignocellulosic biomass in the initial stages of decay. In this work, the combined effects of Mn²⁺, Fe²⁺, and NO₃^- inducers were evaluated based on the activities of hydrolytic enzymes and Fe³⁺ reduction as well as the catechol-type compound production during wheat straw pretreatment by the brown-rot fungus Gloeophyllum trabeum. Weight loss and chemical changes were evaluated to establish the culture conditions for stimulating wheat straw degradation using a central composite design. The results showed that weight loss and the Fe³⁺-reducing activity were promoted at the highest concentrations of Fe²⁺. A positive effect on catechol compound production by the addition of Mn²⁺ and NO₃^- was observed. Cellulase activity was increased at the highest concentration of NO₃^-. The multiple optimizations of G. trabeum culture conditions in wheat straw resulted in 11.3% weight loss and 0.47 total crystallinity index at 0.24 M NO₃^-, 0.95 mM Fe²⁺, and 0.85 mM Mn²⁺ after 40 days. The wheat straw pretreatment by G. trabeum for 10 days increased glucose recovery. The results indicated that the wheat straw pretreatment using G. trabeum with biodegradation inducers could be a complementary step to physicochemical pretreatment of lignocellulosic biomass for production of second-generation ethanol.

Green synthesis of silver nanoparticles: effect of synthesis reaction parameters on antimicrobial activity

In this work, the biosynthesis of silver nanoparticles by Galega officinalis extract using AgNO₃ as a precursor was reported. The reaction parameters for the biosynthesis and efficiency in their antimicrobial control against Escherichia coli, Staphylococcus aureus and Pseudomonas syringae were determined. For biosynthesis, a central composite design combined with response surface methodology was used to optimize the process parameters (pH, AgNO₃ and extract concentration), and the design was assessed through the size distribution, zeta potential and polydispersity index of the nanoparticles. The results demonstrated that at pH 11, 1.6 mM of AgNO₃ and 15% vv^-1 of G. officinalis extract were the optimal reaction parameters. Transmission electron microscope (TEM) images and X-ray diffraction (XRD) confirmed the formation of small spherical silver nanoparticles. Antimicrobial assays showed a high inhibitory effect against E. coli, S. aureus and P. syringae, and that effect was larger with silver nanoparticles of a smaller size (23 nm). This work demonstrates that G. officinalis extract is a feasible medium for the synthesis of silver nanoparticles and that the control of the reaction parameters can determine the nanoparticle characteristics and therefore their antimicrobial effectiveness.

Combined pollution of copper nanoparticles and atrazine in soil: Effects on dissipation of the pesticide and on microbiological community profiles

Copper nanoparticles (NCu) have been proposed as an antimicrobial agent in agriculture. Therefore, NCu may interact with numerous pollutants including pesticides. Little is known about the combined effects of NCu and pesticides in soil. This study aimed at assessing the impact of NCu combined with the herbicide atrazine (ATZ) on soil. We focused on assessing the adsorption and dissipation of ATZ in the presence of NCu and the changes in microbial community profiles. First, ATZ adsorption isotherms (described using the Freundlich equation) were evaluated. After that, soil samples were spiked with NCu (40-60 nm) at 0.05 and 0.15% w/w and ATZ (3 mg a.i kg^-1) and incubated for 30 days. The results showed that ATZ adsorption is favored by the presence of NCu. On the other hand, NCu at 0.15% w/w caused a significant decrease in ATZ dissipation, increasing its half-life from 6 to 37 days. Microbial community profiles (bacteria, fungi and nitrifying bacteria) remained relatively stable throughout the evaluated period. Therefore, our findings suggest that NCu can increase the persistence of ATZ in soil, which may be mostly associated to physical-chemical interaction with soil particles more than a microbial impact.

Sequential white-rot and brown-rot fungal pretreatment of wheat straw as a promising alternative for complementary mild treatments

White-rot and brown-rot fungi have complementary mechanisms to selectively degrade lignin and holocellullose, respectively. Thereby, a fungal co-culture of a white-rot and a brown-rot fungal could result in efficient strategy for a mild lignocellulosic biomass pretreatment. In this work, single, sequential and co-inoculation of the selective-lignin degrading white-rot fungus Ganoderma lobatum and the brown-rot fungus Gloeophyllum trabeum were evaluated as biological pretreatments of wheat straw to enhance enzymatic hydrolysis of cellulose. The single cultures of G. lobatum and G. trabeum exhibited preferential degradation of lignin and hemicellulose, respectively. The total crystallinity index decreased in samples pretreated with G. trabeum but not with G. lobatum. The pretreatment with single cultures of G. lobatum or G. trabeum increased glucose yields by 43.6% and 26.1% respectively compared to untreated straw. Although co-inoculation resulted in higher yields of glucose when compared with single cultures, only a slight synergistic effect between fungi was observed. Contrary, the sequential inoculation of G. lobatum incubated for 10 days followed by G. trabeum incubated for 10 days more showed a strong synergic effect on enzymatic hydrolysis. This sequential culture showed the highest glucose yield (191.5 mg g^-1 wheat straw), 2.8-fold higher than untreated wheat straw, and 140-150% higher than the single-cultures of G. lobatum and G. trabeum, respectively.

Organophosphorus pesticide mixture removal from environmental matrices by a soil Streptomyces mixed culture

The current study aimed to evaluate the removal of a pesticide mixture composed of the insecticides chlorpyrifos (CP) and diazinon (DZ) from liquid medium, soil and a biobed biomixture by a Streptomyces mixed culture. Liquid medium contaminated with 100 mg L^-1 CP plus DZ was inoculated with the Streptomyces mixed culture. Results indicated that microorganisms increased their biomass and that the inoculum was viable. The inoculum was able to remove the pesticide mixture with a removal rate of 0.036 and 0.015 h^-1 and a half-life of 19 and 46 h^-1 for CP and DZ, respectively. The sterilized soil and biobed biomixture inoculated with the mixed culture showed that Streptomyces was able to colonize the substrates, exhibiting an increase in population determined by quantitative polymerase chain reaction (q-PCR), enzymatic activity dehydrogenase (DHA) and acid phosphatase (APP). In both the soil and biomixture, limited CP removal was observed (6-14%), while DZ exhibited a removal rate of 0.024 and 0.060 day^-1 and a half-life of 29 and 11 days, respectively. Removal of the organophosphorus pesticide (OP) mixture composed of CP and DZ from different environmental matrices by Streptomyces spp. is reported here for the first time. The decontamination strategy using a Streptomyces mixed culture could represent a promising alternative to eliminate CP and DZ residues from liquids as well as to eliminate DZ from soil and biobed biomixtures.

Combined effect of enzyme inducers and nitrate on selective lignin degradation in wheat straw by Ganoderma lobatum

Lignin is one of the main barriers to obtaining added-value products from cellulosic fraction of lignocellulosic biomass due to its random aromatic structure and strong association with cellulose and hemicellulose. Inorganic and organic compounds have been used as enzyme inducers to increase the ligninolytic potential of white-rot fungi, without considering their effect on the selectivity of degradation. In this study, the selective lignin degradation in wheat straw by Ganoderma lobatum was optimized using a central composite design to evaluate the combined effect of Fe²⁺ and Mn²⁺ as inducers of ligninolytic enzymes and NO₃^- as an additional nitrogen source. Selective lignin degradation was promoted to maximize lignin degradation and minimize weight losses. The optimal conditions were 0.18 M NO₃^-, 0.73 mM Fe²⁺, and 1 mM Mn²⁺, which resulted in 50.0% lignin degradation and 18.5% weight loss after 40 days of fungal treatment. A decrease in absorbance at 1505 and 900 cm^-1 in fungal-treated samples was observed in the FTIR spectra, indicating lignin and cellulose degradation in fungal-treated wheat straw, respectively. The main ligninolytic enzymes detected during lignin degradation were manganese-dependent and manganese-independent peroxidases. Additionally, confocal laser scanning microscopy revealed that lignin degradation in wheat straw by G. lobatum resulted in higher cellulose accessibility. We concluded that the addition of enzyme inducers and NO₃^- promotes selective lignin degradation in wheat straw by G. lobatum.

Pesticide dissipation and microbial community changes in a biopurification system: influence of the rhizosphere

The dissipation of atrazine, chlorpyrifos and iprodione in a biopurification system and changes in the microbial and some biological parameters influenced by the rhizosphere of Lolium perenne were studied in a column system packed with an organic biomixture. Three column depths were analyzed for residual pesticides, peroxidase, fluorescein diacetate activity and microbial communities. Fungal colonization was analyzed by confocal laser scanning microscopy to assess the extent of its proliferation in wheat straw. The L. perenne rhizosphere enhanced pesticide dissipation and negligible pesticide residues were detected at 20-30 cm column depth. Atrazine, chlorpyrifos and iprodione removal was 82, 89 and 74% respectively in the first 10 cm depth for columns with vegetal cover. The presence of L. perenne in contaminated columns stimulated peroxidase activity in all three column depth sections. Fluorescein diacetate activity decreased over time in all column sections with the highest values in biomixtures with vegetal cover. Microbial communities, analyzed by PCR-DGGE, were not affected by the pesticide mixture application, presenting high values of similarity (>65%) with and without vegetal cover. Microbial abundance of Actinobacteria varied according to treatment and no clear link was observed. However, bacterial abundance increased over time and was similar with and without vegetal cover. On the other hand, fungal abundance decreased in all sections of columns after 40 days, but an increase was observed in response to pesticide application. Fungal colonization and straw degradation during pesticide dissipation were verified by monitoring the lignin autofluorescence loss.

Bioaugmentation and rhizosphere-assisted biodegradation as strategies for optimization of the dissipation capacity of biobeds

Biobeds are on-farm biodepuration systems whose efficiency rely on their high pesticide biodegradation capacity. We evaluated two optimization strategies, bioaugmentation and/or rhizosphere-assisted biodegradation, to maximize the dissipation capacity of biobeds. Iprodione was used as a model pesticide. Its dissipation and metabolism was determined in a biobed packing material inoculated with an iprodione-degrading Arthrobacter strain C1 (bioaugmentation, treatments B+C1) and/or seeded with ryegrass (rhizosphere-assisted biodegradation, treatments B+P). The impact of those strategies on the activity and composition of the microbial community was determined. Bioaugmentation accelerated the dissipation of iprodione which was further enhanced in the bioaugmented, rhizosphere-assisted treatment (treatment B+P+C1, Half-life (DT₅₀) = 3.4 d), compared to the non-bioaugmented, non rhizosphere-assisted control (DT₅₀ = 9.5 d, treatment B). Bioaugmentation resulted in the earlier formation of intermediate formation of metabolites I (3,5-dichlorophenyl-carboxamide), II (3,5-dichlorophenylurea acetate) and 3,5-dichloroaniline (3,5-DCA). The latter was further dissipated by the indigenous microbial community. Acid phosphatase (AP) and β-glucosidase (GLU) were temporarily stimulated in rhizosphere-assisted treatments, whereas a stimulation of the fluorescein diacetate (FDA) hydrolytic activity in the bioaugmented treatments coincided with the hydrolysis of iprodione. q-PCR showed that changes in the abundance of alpha-proteobacteria and firmicutes was driven by the presence of rhizosphere while bioaugmentation had no significant effect.

Aging of biomixtures: Effects on carbofuran removal and microbial community structure

The aim of this work was to determine the efficiency of a straw/compost/soil biomixture for pesticide depuration during its aging and continuous use, for a period of over a year, based on its capacity to remove carbofuran (CFN), while simultaneously monitoring the variations in microbial community structure. Successive CFN spikings were applied in the biomixture at 6-week intervals, and the removal efficiency was determined 48 h post-application. Initially, only a discrete degradation performance was observed (9.9%), but one CFN application was sufficient to induce efficient elimination (>88.5%) of the pesticide at subsequent influxes for a period of over 6 months. A statistically significant reduction on CFN removal efficiency after this time was detected, reaching levels similar to the fresh-prepared biomixture (14.8%) at the end of the experiment. Simultaneous DGGE analyses showed only modest changes on microbial community patterns through time for both, bacteria and fungi. The clustering of genetic fingerprints in chronological groups corresponding to significantly different CFN degradation efficiencies indicates that biomixture aging changes not only the composition of microbial communities, but also their suitability to engage in pesticide degradation. Periodic substitution of straw/compost/soil biomixture in biopurification systems or regular provision of easily-degradable organic substrates should be considered to maintain an adequate depuration capacity on this system.

Increased diazinon hydrolysis to 2-isopropyl-6-methyl-4-pyrimidinol in liquid medium by a specific Streptomyces mixed culture

Actinobacteria identified as Streptomyces spp. were evaluated for their ability to remove diazinon as the only carbon source from a liquid medium. Single cultures of Streptomyces strains were exposed to diazinon at a concentration of 50 mg L(-1). After 96 h incubation, six of the eight cultures grew and five strains showed an increase in their total protein concentrations and changes in their protein profile. Up to 32% of the diazinon was removed by the single Streptomyces cultures. A compatibility assay showed that the different Streptomyces species were not antagonistic. Twenty-six mixed cultures were then prepared. Diazinon removal was increased when mixed cultures were used, and maximum diazinon removal of 62% was observed when the Streptomyces spp. strains AC5, AC9, GA11 and ISP13 were mixed; this was defined as the selected mixed culture (SMC). Diazinon removal was positively influenced by the addition of glucose into the liquid medium. Our study showed a diazinon degradation rate of 0.025 h(-1), half-life of 28 h(-1) and 2-isopropyl-6-methyl-4-pyrimidinol (IMHP) production of 0.143 mg L h(-1). Rapid diazinon hydrolysis to IMHP was associated with a decrease in the pH of the medium as a consequence of microbial glucose metabolism and organic acid exudation. Moreover, the SMC of Streptomyces was able to remove IMHP. This work constitutes a new, if not the only, report on diazinon degradation by mixed cultures of Streptomyces spp. Given the high levels of diazinon removal, the SMC formed by four Streptomyces strains has the potential to be used to treat the diazinon present in environmental matrices.

Probing non polar interstellar molecules through their protonated form: Detection of protonated cyanogen (NCCNH+)

Cyanogen (NCCN) is the simplest member of the series of dicyanopolyynes. It has been hypothesized that this family of molecules can be important constituents of interstellar and circumstellar media, although the lack of a permanent electric dipole moment prevents its detection through radioastronomical techniques. Here we present the first solid evidence of the presence of cyanogen in interstellar clouds through the detection of its protonated form toward the cold dark clouds TMC-1 and L483. Protonated cyanogen (NCCNH+) has been identified through the J = 5 - 4 and J = 10 - 9 rotational transitions using the 40m radiotelescope of Yebes and the IRAM 30m telescope. We derive beam averaged column densities for NCCNH+ of (8.6 ± 4.4) × 1010 cm-2 in TMC-1 and (3.9 ± 1.8) × 1010 cm-2 in L483, which translate to fairly low fractional abundances relative to H2, in the range (1-10) × 10-12. The chemistry of protonated molecules in dark clouds is discussed, and it is found that, in general terms, the abundance ratio between the protonated and non protonated forms of a molecule increases with increasing proton affinity. Our chemical model predicts an abundance ratio NCCNH+/NCCN of ~ 10-4, which implies that the abundance of cyanogen in dark clouds could be as high as (1-10) × 10-8 relative to H2, i.e., comparable to that of other abundant nitriles such as HCN, HNC, and HC3N.

Evaluation of biodegradable polymers as encapsulating agents for the development of a urea controlled-release fertilizer using biochar as support material

Biochar constitutes a promising support material for the formulation of controlled-release fertilizers (CRFs). In this study we evaluated the effect of different polymeric materials as encapsulating agents to control nitrogen (N) leaching from biochar based CRFs. Nitrogen impregnation onto biochar was performed in a batch reactor using urea as N source. The resulting product was encapsulated by using sodium alginate (SA), cellulose acetate (CA) and ethyl cellulose (EC). Leaching potential was studied in planted and unplanted soil columns, monitoring nitrate, nitrite, ammonium and urea concentrations. After 90 days, plants were removed from the soil columns and plant yield was evaluated. It was observed that the ammonium concentration in leachates presented a maximum concentration for all treatments at day 22. The highest concentration of N in the leachates was the nitrate form. The crop yield was negatively affected by all developed CRFs using biochar compared with the traditional fertilization.

Enzymes as useful tools for environmental purposes

In the environment enzymes may play important and different roles at least in three cases: as main agents (as isolated, cell-bound or immobilized enzymes) in charge of either the transformation and/or degradation of compounds polluting the environment and the restoration of the polluted environment; as reliable and sensitive tools to detect and measure the amount and concentration of pollutants before, during and after the restoration process; as reliable, easy and sensitive indicators of quality and health status of the environment subjected to the restoration process. To our knowledge papers or reviews integrating findings on these three functions of enzymes are missing in literature. Therefore the main scope of the present paper is to briefly encompass general and specific concepts about roles of enzymes as decontaminating agents, pollutant assaying agents and indicators of environment safety. Examples chosen among those published very recently, supporting and confirming peculiarities, features, and performance of enzymatic agents will be illustrated.

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.

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.

Degradation of pesticide mixture on modified matrix of a biopurification system with alternatives lignocellulosic wastes

The biobed systems were designed to retain and to degrade pesticides through the properties of a biomixture composed of straw (ST), topsoil and peat (PT) 2:1:1 v/v. The ST is the main substrate in the biomixture, as it allows the proliferation of fungi that promotes pesticide degradation. The use of readily available components in the biomixture is an important aspect to build a biobed. Therefore, potential use of readily available wastes as barley husk (BH), sawdust (SW) and oat husk (OH), as total or partial substitutes of ST were tested in pesticide degradation studies. Metabolite formation and the biological activities were also evaluated. Biomixture composed of OH was highly efficient in pesticide degradation, with t½ values of 28.6, 58.9 and 26.8 d for atrazine (ATZ), chlorpyrifos (CHL) and isoproturon (ISP). On the other hand, comparable for degrading capacities with the ST based biomixture were obtained with SW and BH, but only as partial replacement. Contrarily, high t½ values (more than 100 d) were obtained in biomixtures with total substitution of ST by SW or BH. Metabolite formation was observed in all biomixtures tested, but without clear formation patterns. Moreover, high and stable biological activity was observed in the biomixtures composed of OH. Therefore, our results demonstrated that ST can be partial or totally replaced by OH in the biomixture allowing an efficient degradation of pesticide mixture. However, it is recommended that ST can be only partially replaced by BH and SW in the biomixture to allow efficient pesticide degradation.

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.

Effect of pulp mill sludge on soil characteristics, microbial community and vegetal production of Lolium Perenne

The effect of pulp mill sludge addition (10-30 Mg/ha) to soil derived from volcanic ash (Andisol) on soil characteristics, microbial community and Lolium perenne L. cv quartet. biomass production was evaluated in field assays. Soil without sludge was used as a control treatment. The sludge addition improved the chemical properties of the soil. Organic matter and phosphorous content increased in the soil with increasing amounts of sludge, obtaining 35% more organic matter content with the application of 30 Mg/ha than the control soil. The phosphorous was accumulated into the soil after the end of cultivation improving the phosphorous pool in the soil. When 30 Mg/ha sludge was added to the soil, a biomass of Lolium perenne, was 60% more than the control soil at the end of the experiment. The analysis of soil microbial community showed that the application of sludge did not modify greatly the microbial community of fungi and bacteria even when high doses were applied.

Chlorophenol degradation in soil columns inoculated with Anthracophyllum discolor immobilized on wheat grains

The white-rot fungus Anthracophyllum discolor immobilized on wheat grains was evaluated for chlorophenol (2,4-dichlorophenol, 2,4,6-trichlorophenol and pentachlorophenol) degradation in allophanic soil columns activated by acidification. Columns without inoculation were used as the control to evaluate the adsorption capacity of the soil columns. The chlorophenols were removed efficiently in soil columns by both adsorption and degradation processes. In inoculated soil columns, 2,4-dichlorophenol was highly degraded and this degradation is associated with a high production of manganese peroxidase. 2,4,6-trichlorophenol was degraded to a lesser extent compared with 2,4-dichlorophenol. Pentachlorophenol was first removed by adsorption and then through degradation by the fungus. Manganese peroxidase activity was lowest when the column was fed with pentachlorophenol and highest when the column was fed with 2,4-dichlorophenol. Laccase was also produced by the fungus but to a lesser degree.

Degradation of polycyclic aromatic hydrocarbons by the Chilean white-rot fungus Anthracophyllum discolor

The degradation of three- and four-ring polycyclic aromatic hydrocarbons (PAHs) in Kirk medium by Anthracophyllum discolor, a white-rot fungus isolated from the forest of southern Chile, was evaluated. In addition, the removal efficiency of three-, four- and five-ring PAHs in contaminated soil bioaugmented with A. discolor in the absence and presence of indigenous soil microorganisms was investigated. Production of lignin-degrading enzymes and PAH mineralization in the soil were also determined. A. discolor was able to degrade PAHs in Kirk medium with the highest removal occurring in a PAH mixture, suggesting synergistic effects between PAHs or possible cometabolism. A high removal capability for phenanthrene (62%), anthracene (73%), fluoranthene (54%), pyrene (60%) and benzo(a)pyrene (75%) was observed in autoclaved soil inoculated with A. discolor in the absence of indigenous microorganisms, associated with the production of manganese peroxidase (MnP). The metabolites found in the PAH degradation were anthraquinone, phthalic acid, 4-hydroxy-9-fluorenone, 9-fluorenone and 4,5-dihydropyrene. A. discolor was able to mineralize 9% of the phenanthrene. In non-autoclaved soil, the inoculation with A. discolor did not improve the removal efficiency of PAHs. Suitable conditions must be found to promote a successful fungal bioaugmentation in non-autoclaved soils.

Effect of soya lecithin on the enzymatic system of the white-rot fungi Anthracophyllum discolor

The present work optimized the initial pH of the medium and the incubation temperature for ligninolytic enzymes produced by the white-rot fungus Anthracophyllum discolor. Additionally, the effect of soya lecithin on mycelial growth and the production of ligninolytic enzymes in static batch cultures were evaluated. The critical micelle concentration of soya lecithin was also studied by conductivity. The effects of the initial pH (3, 4, and 5) and incubation temperature (20, 25, and 30°C) on different enzymatic activities revealed that the optimum conditions to maximize ligninolytic activity were 26°C and pH 5.5 for laccase and manganese peroxidase (MnP) and 30°C and pH 5.5 for manganese-independent peroxidase (MiP). Under these culture conditions, the maximum enzyme production was 10.16, 484.46, and 112.50 U L(-1) for laccase, MnP, and manganese-independent peroxidase MiP, respectively. During the study of the effect of soya lecithin on A. discolor, we found that the increase in soya lecithin concentration from 0 to 10 g L(-1) caused an increase in mycelial growth. On the other hand, in the presence of soya lecithin, A. discolor produced mainly MnP, which reached a maximum concentration of 30.64 ± 4.61 U L(-1) after 25 days of incubation with 1 g L(-1) of the surfactant. The other enzymes were produced but to a lesser extent. The enzymatic activity of A. discolor was decreased when Tween 80 was used as a surfactant. The critical micelle concentration of soya lecithin calculated in our study was 0.61 g L(-1).

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.

Degradation of polycyclic aromatic hydrocarbons by free and nanoclay-immobilized manganese peroxidase from Anthracophyllum discolor

Manganese peroxidase (MnP) produced by Anthracophyllum discolor, a Chilean white rot fungus, was immobilized on nanoclay obtained from volcanic soil and its ability to degrade polycyclic aromatic hydrocarbons (PAHs) compared with the free enzyme was evaluated. At the same time, nanoclay characterization was performed. Nanoclay characterization by transmission electronic microscopy showed a particle average size smaller than 100 nm. The isoelectric points (IEP) of nanoclay and MnP from A. discolor were 7.0 and 3.7, respectively, as determined by micro electrophoresis migration and preparative isoelectric focusing. Results indicated that 75% of the enzyme was immobilized on the nanoclay through physical adsorption. As compared to the free enzyme, immobilized MnP from A. discolor achieved an improved stability to temperature and pH. The activation energy (Ea) value for immobilized MnP (51.9 kJ mol(-1)) was higher than that of the free MnP (34.4 kJ mol(-1)). The immobilized enzyme was able to degrade pyrene (>86%), anthracene (>65%), alone or in mixture, and to a less extent fluoranthene (<15.2%) and phenanthrene (<8.6%). Compared to free MnP from A. discolor, the enzyme immobilized on nanoclay enhanced the enzymatic transformation of anthracene in soil. Overall results indicate that nanoclay, a carrier of natural origin, is a suitable support material for MnP immobilization. In addition, immobilized MnP shows an increased stability to high temperature, pH and time storage, as well as an enhanced PAHs degradation efficiency in soil. All these characteristics may suggest the possible use of nanoclay-immobilized MnP from A. discolor as a valuable option for in situ bioremediation purposes.

Kinetic and thermodynamic study of chlorophenol sorption in an allophanic soil

The sorption of 2,4-dichlorophenol, 2,4,6-trichlorophenol, and pentachlorophenol by a allophanic soil was studied in a series of batch experiments. Chlorophenol sorption behavior was evaluated as a function of reaction time (0-96h) and input concentration at a fixed ionic strength (0.1mol L(-1) KCl) at 25, 35, and 45 degrees C. Sorption results for the various reaction temperatures were used in calculating thermodynamic parameters. Chlorophenol sorption increased with temperature, suggesting an endothermic process. The Elovich equation was used to describe the kinetic data. Data from the isotherm experiments were described by the Triple-Layer Model in which monodentate outer- and inner-sphere complexes were formed between deprotonated organic molecules and active sites on the variable-charge soil. The calculated thermodynamic parameters suggest that chlorophenol sorption is a spontaneous (DeltaG<0), endothermic (DeltaH>0) and entropy-driven reaction (DeltaS>0).

Using lignimerin (a recovered organic material from Kraft cellulose mill wastewater) as sorbent for Cu and Zn retention from aqueous solutions

Adsorption of copper and zinc in lignimerin (an organic material mainly composed by lignin, carbohydrate fragments and some extractives) and its acid derivative (H-lignimerin), recovered from Kraft cellulose mill wastewater was examined. A Box-Behnken experiment design, used to optimize lignimerin recovery process, revealed that the type of solvent used for precipitation is a determining factor in the amount of substance obtained. Conversely, batch adsorption studies at pH 4.0 revealed that the maximum adsorption capacities, modeled by the Langmuir equation, were 666.7 and 370.4 mmol kg(-1) for Cu(II) and Zn(II), respectively in lignimerin and 232.6 and 312.5 mmol kg(-1) for Cu(II) and Zn(II), respectively in H-lignimerin. The adsorption of Cu(II) and Zn(II) through deprotonated hydroxyl and carboxylic groups was the dominant mechanism that may explain the adsorption in both materials. The adsorption capacities indicated that lignimerin, with a molecular mass between 50 and 70 kDa, has a potential use as an organic sorbent for removing copper and zinc from liquid resources.

Recovery and characterization of the humate-like salified polymeric organic fraction (lignimerin) from Kraft cellulose mill wastewater

A dark and complex salified organic polymeric mixture, named lignimerin, was for the first time recovered from Kraft cellulose mill wastewater (KCMW) and characterized by chemical, spectroscopic and relative molecular weight (RMW) analysis. Lignimerin proved to be composed of polyphenols (57.00%), carbohydrates (22.26%) and proteins (7.42%). It also contained metals (6.93%), mainly Ca and, to much lower extent, Mg, Na, Al, Fe, K, Mn, Zn and Cu, bound to the carboxylate and phenate groups. The distribution of lignimerin RMW was assessed to be approximately between 1000 and 8600Da, as well as to consist of lignin and tannin, protein and polysaccharide moieties, strongly aggregated each other. H-lignimerin, its acid derivative, revealed a chemical composition and a RMW distribution very close to that of lignimerin, but a marked metal cations decreasing (1.60%) with respect to lignimerin (6.93%). The humic acid-like nature of both the polymers was assessed. Their potential use as bio-adsorbents of heavy metals is briefly discussed.

Adsorption behavior of 2,4-dichlorophenol and pentachlorophenol in an allophanic soil

The adsorption of 2,4-dichlorophenol (2,4-DCP) and pentachlorophenol (PCP) by a variable-charge soil from southern Chile was studied in a series of batch equilibration experiments. 2,4-DCP and PCP adsorption behavior was evaluated as a function of pH (pH values of 4.5, 6.0 and 7.5) in a 0.1M KCl (25 degrees C) background solution for soil material collected at three different depths (0-20 cm, 20-40 cm, and 40-60 cm). 2,4-DCP and PCP adsorption decreased with increasing soil pH, suggesting that the undissociated species were adsorbed more readily and that electrostatic repulsion may inhibit partitioning as pH increases. The PCP adsorption was greater than observed for 2,4-DCP and decreased with soil depth. Multiple regression analysis between K(d) and various soil properties indicated that the soil organic carbon content is a strong indicator of chlorophenol adsorption, and in addition to organic carbon, the soil pH is an important property controlling adsorption behavior.

Kraft mill sludge to improve vegetal production in Chilean Andisol

The effect of kraft mill sludge addition (25 to 75 ton/ha) to soil derived from volcanic ashes (Andisol) on wheat (Triticum aestivum L.cv. Puken) biomass production, and in the nutrient absorption by the plants was evaluated. Respiration activity and seed germination tests were carried out on the soil/sludge mixtures, in order to evaluate possible toxic effects due to the sludge addition to the soil. Soil without sludge was used as a control treatment. The plants were grown in a greenhouse (25 degrees C, 14 h-photoperiod) during 120 days, then the plants were collected and dried at 65 degrees C for 72 h for the determination of biomass production (root and aerial) and analyzed for mineral content (Ca, Mg, K and P). The mixtures of soil/sludge showed no toxicity. Seed germination and respiration activity increased with the increment of the sludge. The accumulated CO2 in the soil without sludge was 41.66 mg CO2/100; this value shows a low microbial activity. The biomass increased with the increment of sludge addition to the soil and five times more biomass was obtained when 75 ton/ha sludge was added to the soil. The nutrient absorption efficiency was also improved with the sludge addition.

Irrigation model of bleached Kraft mill wastewater through volcanic soil as a pollutants attenuation process

An irrigation process through volcanic soil columns was evaluated for bleached Kraft mill effluent pollutants retention. The system was designed to remove color and phenolic compounds and a simple kinetic model for determining the global mass transfer coefficient and the adsorption rate constant was used. The results clearly indicate that the global mass transfer coefficient values (K(c)a) and the adsorption rate constants are higher for the irrigation processes onto acidified soil. This means that the pretreatment of washing the volcanic soil with an acid solution has a positive effect on the adsorption rate for both pollutant groups. The enhanced adsorption capacity is partially explained by the activation of the metal oxides present in the soil matrix during the acid washing process. Increasing the flow rate from 1.5 to 2.5 ml/min yielded higher (K(c)a) values and adsorption rate constants for both pollutant groups. For instance, regarding color adsorption onto acidified soil, there is an increment of 43% in the (K(c)a) value for the experiment with a flow rate of 2.5 ml/min. Increasing the porosity of the column from 0.55 to 0.59, yielded a decrease in the (K(c)a) values for color and phenolic compounds adsorption processes. Onto natural soil for example, these decreases reached 21% and 24%, respectively. Therefore, the (K(c)a) value is dependent on both the liquid-phase velocity (external resistance) and the soil fraction in the column (internal resistance); making forced convection and diffusion to be the main transport mechanisms involved in the adsorption process. Analyzing the adsorption rate constants (K(c)a)/m, phenolic compounds and color adsorption rates onto acidified soil of 2.25 x 10(-6) and 2.62 x 10(-6) l/mg min were achieved for experiment 1. These adsorption rates are comparable with other adsorption systems and adsorbent materials.

Describing chlorophenol sorption on variable-charge soil using the triple-layer model

The sorption of 2,4-dichlorophenol, 2,4,6-trichlorophenol, and pentachlorophenol by a variable-charge soil from southern Chile was studied in a series of batch experiments. The chlorophenol sorption behavior was evaluated as a function of pH (pH range 4-8) at two different ionic strengths, 0.01 and 0.1 M KCl (25 degrees C). Chlorophenol sorption depended on pH and a downward shift in the soil PZC was observed with increasing chlorophenol concentration. Chlorophenol sorption decreased with increasing pH, suggesting that the undissociated species is sorbed more readily and that electrostatic repulsion may inhibit partitioning as pH increases. Data from the sorption experiments were fitted by the triple-layer model, in which monodentate outer- and inner-sphere complexes were formed between deprotonated organic molecules and active sites on the variable-charge soil.