Degradation of isoproturon in biobeds

The fate of isoproturon {N,N-dimethyl-N'-[4-(1-methylethyl)phenyl]urea} in biobeds with and without inoculation with the white rot fungus Phanerochaete chrysosporium was studied. Total extractable isoproturon, its metabolites and formation of non-extractable residues were evaluated. Studies with ¹⁴C-isoproturon were also included. A strong decrease in isoproturon was observed in non-inoculated biobeds. Total extractable isoproturon decreased by 76% after 100 days. The decrease was even larger in biobeds inoculated with the white rot fungus P. chrysosporium. After 28 days, total extractable isoproturon decreased by 78%, and after 100 days >99% had disappeared in the inoculated biobeds. However, the studies with ¹⁴C-isoproturon showed that 30% of the initially recovered ¹⁴C-isoproturon remained in the non-inoculated biobeds as non-extractable residues. As no studies with ¹⁴C-isoproturon were performed in inoculated biobeds, it is unclear if the higher rate of disappearance was due to higher biodegradation or higher formation of bound residues.     

Comparative Analysis of Azo Dye Biodegradation by Aspergillus oryzae and Phanerochaete chrysosporium

The paper reports ultraviolet matrix-assisted laser desorption/ionization mass spectroscopy (UVMALDI-MS) protocol for determination of complex heterogeneous emulsion or suspension formulations. The active agents and surfactants are morpholine fungicide fenpropimorph (1), amorolfine (2), tridemorph (mixture of 2,6-dimethyl-4-alkylmorpholins 3–6), 2,6-dimethyl-4-[2-methyl-3-(6-methyl-decahydro-naphthalen-2-yl)-propyl]-morpholine (7), dodemorph (8), main metabolite of 1 fenpropimorph acid (9), sodium dodecyl sulfate (10), and stearate (11). The full method and techniques validation as well as method performance parameters are discussed in terms of their maximal representativeness toward real environmental and foodstuff assay problems. These are additionally complicated by heterogeneous laterally, vertically, and time distribution of pesticide contaminants and their major metabolites in environmental samples. The real environmental heterogeneous distribution is elucidated, studying sterilized soil fractions with particle size 2.0 μm, clay content 11.5 %, silt 23.0 %, sand 8.1 %, and pH?∈ 6.0–8.1. A statistical sampling cluster approach is used. The method performance parameters are concentration LODs of 0.026 mg kg^?1 (res. LOQs 0.08666 mg kg^?1). Concentration linear dynamic ranges are ∈?0.025–7.3 mg kg^?1 (r ²?=?0.99822 and 0.99421) and ∈?2.3–7.4 mg kg^?1 (level of confidence of 99.33₁?%) for complex spiked heterogeneous soil samples. The data illustrates the great capability of method and its promising application for environmental contamination monitoring and controlling programs for assessment.     

Detoxification of corn stover and corn starch pyrolysis liquors by ligninolytic enzymes of Phanerochaete chrysosporium

Phanerochaete chrysosporium (ATCC 24725) shake flask culture with 3 mM veratryl alcohol addition on day 3 was able to grow and detoxify different concentrations of diluted corn stover (Dcs) and diluted corn starch (Dst) pyrolysis liquors [10, 25, and 50% (v/v)] in defined media. GC-MS analysis of reaction products showed a decrease and change in some compounds. In addition, the total phenolic assay with Dcs samples demonstrated a decrease in the phenolic compounds. A bioassay employing Lactobacillus casei growth and lactic acid production was developed to confirm the removal of toxic compounds from 10 and 25% (v/v) Dcs and Dst by the lignolytic enzymes, but not from 50% (v/v) Dcs and Dst. The removal did not occur when sodium azide or cycloheximide was added to Ph. chrysosporium culture media, confirming the participation of lignolytic enzymes in the detoxification process. A concentrated enzyme preparation decreased the phenolic compounds in 10% (v/v) corn stover and corn starch pyrolysis liquors to the same extent as the fungal cultures.     

Ligninolytic enzyme production by Phanerochaete chrysosporium in plastic composite support biofilm stirred tank bioreactors

Phanerochaete chrysosporium (ATCC 24725) produced lignin peroxidase (LiP) and manganese peroxidase (MnP) in defined medium in plastic composite support (PCS) biofilm stirred tank reactors. Laccase was not detected. The formation of the Ph. chrysosporium biofilm on the PCS was essential for the production of MnP and LiP. The bioreactor was operated as a repeat batch, and no reinoculation was required between batches. Peroxidase production was influenced by 5 min purging of the bioreactor with pure oxygen or continuous aerating with a mixture of air and oxygen at a flow rate of 0.005 vvm. Continuous aeration and 300 rpm agitation with 3 mM veratryl alcohol addition on days 0 and 3 demonstrated the highest lignin peroxidase production on day 6 with means of 50.0 and 47.0 U/L. Addition of veratryl alcohol and MnSO(4) on day 0 with 300 rpm agitation and continuous aeration at 0.005 vvm (air flow rate in L/min divided by the reactor working volume in liters) hastens the production of MnP with final yield of 63.0 U/L after 3 days. Fourteen repeated batches fermentation were performed without contamination due to low pH (4.5) and aseptic techniques employed.     

Solid-substrate fermentation of corn fiber by Phanerochaete chrysosporium and subsequent fermentation of hydrolysate into ethanol

The goal of this study was to develop a fungal process for ethanol production from corn fiber. Laboratory-scale solid-substrate fermentation was performed using the white-rot fungus Phanerochaete chrysosporium in 1 L polypropylene bottles as reactors via incubation at 37 degrees C for up to 3 days. Extracellular enzymes produced in situ by P. chrysosporium degraded lignin and enhanced saccharification of polysaccharides in corn fiber. The percentage biomass weight loss and Klason lignin reduction were 34 and 41%, respectively. Anaerobic incubation at 37 degrees C following 2 day incubation reduced the fungal sugar consumption and enhanced the in situ cellulolytic enzyme activities. Two days of aerobic solid-substrate fermentation of corn fiber with P. chrysosporium, followed by anaerobic static submerged-culture fermentation resulted in 1.7 g of ethanol/100 g of corn fiber in 6 days, whereas yeast ( Saccharomyces cerevisiae) cocultured with P. chrysosporium demonstrated enhanced ethanol production of 3 g of ethanol/100 g of corn fiber. Specific enzyme activity assays suggested starch and hemi/cellulose contribution of fermentable sugar.     

Co-remediation of DDT-contaminated soil using white rot fungi and laccase extract from white rot fungi

Purpose

2,2-Bis(p-chlorophenyl)-1,1,1-trichloroethane (DDT), one of the most widely used organochlorine pesticides in soil, was banned in the 1970s for agricultural use because of its detrimental impacts on wildlife and harmful effects on human health via the food chain. However, high levels of DDT are frequently detected in agricultural soils in China. Considering this situation, this study investigated the use of white rot fungi and laccase derived from white rot fungi to co-remediate DDT-contaminated soil.

Materials and methods

A culture of white rot fungi was used to inoculate soil samples and also to extract laccase from. Soil was contaminated with four components of DDT (p,p′-DDE, o,p′-DDT, p,p′-DDD, and p,p′-DDT). Individual DDT components and the sum of the DDT components (p,p′-DDE, o,p′-DDT, p,p′-DDD, and p,p′-DDT—collectively referred to as DDTs) were both analyzed by GC at various stages during the incubation period. The efficacy of co-remediating DDT-contaminated soil using white rot fungi and laccase was tested by investigating how degradation varied with varying amounts of white rot fungi, sterilizing soil, temperature, soil pH, concentrations of DDT, and concentration of the heavy metal ion Cd²⁺.

Results and discussion

“”It was concluded that the reduction of DDTs in soil using white rot fungi and laccase was higher than reduction using only white rot fungi or laccase by nearly 14 and 16 %, respectively. Five milliliters fungi per 15 g soil and 6 U laccase per gram soil were the optimal application rates for remediation, as shown by a reduction in DDTs of 66.82 %. The difference in the reduction of individual DDT components and DDTs between natural and sterilized soils was insignificant. The optimal temperature and pH in the study were 28 °C and 4.5, respectively. In addition, reduction of individual DDT components and DDTs increased with increasing concentrations of DDT and decreased with increasing concentrations of Cd²⁺.

Conclusions

Compared with the remediation of DDT using only white rot fungi or laccase, the co-remediation of DDT using white rot fungi and laccase degraded DDT in soil more rapidly and efficiently; the highest reduction of DDTs was 66.82 %.     

Biological control of onion white rot

Six bacteria and one fungus isolated from sclerotia of Sclerotium cepivorum, the causal agent of white rot of onions, produced diffusible antibiotics antagonistic to growth of S. cepivorum on potato dextrose agar. Three of the bacterial isolates applied as seed treatments to onions grown in non-sterile muck soil in a controlled environment chamber reduced the proportion of infections by S. cepivorum. Antagonists were further evaluated as seed treatments for field control of white rot on two onion cultivars grown on muck soil containing high levels of natural inoculum. Four of the bacterial isolates provided significant season-long protection on the partially-resistant cultivar Festival, and the best of these also provided significant protection on the susceptible cultivar Autumn Spice. The fungal antagonist has been identified as Penicillium nigricans, and all bacterial isolates appear to be Bacillus subtilis. The levels of protection provided by some of these latter isolates were comparable to those provided by chemical treatments and represent practical potential for field control of white rot.     

Degradation of ioxynil by a soil fungus, Fusarium solani

A fungus, Fusarium solani, isolated from the soil, degraded ioxynil (3,5-diiodo-4-hydroxyben-zonitrile) in pure culture into at least eight products. Five products were detected in the organic fractions extracted from a culture grown in [¹⁴C]cyano-labeled ioxynil. Three additional products were separated by ion-exchange chromatography of the acidified aqueous phase. Cultures grown in the presence of [¹⁴C]ring-labeled ioxynil produced the same products in the organic extract and four to five products in the aqueous phase. The cyano-carbon of ioxynil was released as CO₂ at a faster rate than that of ring-carbons and was released after the initial ring cleavage. Two of the metabolites were identified as 3,5-diiodo-4-hydroxybenzamide and 3,5-diiodo-4-hydroxybenzoic acid.     

Mineralization of hydroxylated isoproturon metabolites produced by fungi

When exposed to the herbicide isoproturon, some soil fungi in pure culture metabolize the substance to hydroxylated metabolites. Hydroxylated metabolites of isoproturon have also been detected in soil studies. In an agricultural soil not previously exposed to isoproturon we found that the hydroxylated isoproturon metabolite N-(4-(2-hydroxy-1-methylethyl)phenyl)-N′,N′-dimethylurea mineralized faster than both isoproturon and its N-demethylated metabolite N-(4-isopropylphenyl)-N′-methylurea (MDIPU), thus indicating that mineralization of isoproturon is stimulated by fungal hydroxylation in this soil. In soils previously treated with isoproturon, in contrast, isoproturon and both its hydroxylated and demethylated metabolites mineralized at almost the same rate with up to 52% of the ¹⁴C-ring-carbon being degraded to ¹⁴CO₂ within 63 days. Thus hydroxylated metabolites of isoproturon do not seem to be more persistent than isoproturon, and hence may degrade before they can leach from topsoil and contaminate the aquatic environment. While an isoproturon-mineralizing bacterium Sphingomonas sp. SRS2 and a MDIPU-mineralizing mixed bacterial culture were able to deplete the medium of hydroxylated metabolites, little or no mineralization took place. This indicates that other bacteria must be present in the soil that are able to benefit from isoproturon being made available to mineralization by fungal hydroxylation.     

Biological control of the charcoal root rot fungus Macrophomina phaseolina on slash pine seedlings by a hyperparasite

Macrophomina phaseolina. the cause of damping-off and charcoal root rot disease on slash pine seedlings (Pinus elliottii Engelm var. elliottii), was antagonized by an unidentified basidiomycete species under laboratory and nursery conditions. Aseptically-grown slash pine seedlings died 3 days after inoculation with M. phaseolina, whereas seedlings inoculated with the basidiomycete sp., or basidiomycete sp. plus M. phaseolina, and uninoculated controls were alive after 6 months. In nursery studies, survival of slash pine seedlings in plots inoculated with M. phaseolina was significantly lower (57 per cent) than survival resulting from inoculations with the basidiomycete sp. (90 per cent), or basidiomycete sp. plus M. phaseolina (84 per cent), and the uninoculated controls (81 per cent). Electron microscopy showed that the basidiomycete sp. is a hyperparasite on mycelia of M. phaseolina. Preliminary evidence indicates that the hyperparasite is not host-specific but will infect other fungal pathogens. Two ectomycorrhizal fungi were not parasitized by the basidiomycete.     

采用白腐菌对难降解有机污染物的生物净化

白腐菌对难降解污染物的生物降解作用已引起世界范围内的普遍关注，它可通过其分泌的特殊的降解酶系或其他机制将各种难降解的有机污染物彻底降解为CO₂和H₂O。该文介绍了白腐真菌的生物学特性及其分泌的酶系，阐述了白腐菌所分泌的酶在降解各种难降解有机物中的作用机制，分析了提高白腐菌降解能力的方法，总结了白腐菌在治理环境污染方面的应用现状与研究进展，探讨了白腐菌在实际应用方面的不足以及今后的研究方向，对白腐菌在解决环境污染方面的问题具有实际意义。     

银耳微波真空干燥特性及动力学模型

利用微波真空干燥技术,对银耳微波真空干燥特性进行研究,探讨不同微波强度、真空度及初始含水率对失水速率的影响,其中微波强度对失水速率影响最大。根据试验数据建立银耳微波真空干燥的水分比与干燥时间关系的动力学模型,并对模型进行拟合检验。结果发现银耳微波真空干燥过程符合Page模型,该模型预测值与实测值拟合良好。该模型可以准确预测银耳在微波真空干燥过程中的含水率和失水速率。     

Sphingobium属细菌土壤中降解异丙隆的特性

通过在不同环境条件的土壤中接入异丙隆降解菌悬液,研究了Sphingobium属的3株细菌—YBL1、YBL2和YBL3在土壤中降解异丙隆的特性,分析了土壤类型、温度、碳氮源、土壤含水量和菌株接种量等因素对3株细菌降解土壤中异丙隆的影响。结果表明,3株细菌在马肝土(pH 6.7)中能够高效降解异丙隆,在红壤(pH 4.5)中不能降解异丙隆,菌株YBL3在潮土(pH 8.2)中也有较好的降解效果;当接种量低于105CFU g-1土时,3株细菌均不能降解马肝土中的异丙隆,接种量高于106CFU g-1土时,菌株可以高效地降解土壤中的异丙隆;马肝土含水量低于40%时,3株细菌降解土壤中异丙隆的速率与土壤含水量呈正相关关系;在16~37℃范围内,菌株降解马肝土中异丙隆的速率与温度亦呈正相关关系。     

Biotransformation of vinclozolin by the fungus Cunninghamella elegans

This study investigated the biotransformation of the dicarboximide fungicide vinclozolin [3-(3,5-dichlorophenyl)-5-methyl-5-vinyl-1,3-oxazolidine-2,4-dione] by the fungus Cunninghamella elegans. Experiments with phenyl-[U-ring-14C]vinclozolin showed that after 96 h incubation, 93% had been transformed to four major metabolites. Metabolites were separated by HPLC and characterized by mass and NMR spectroscopy. Biotransformation occurred predominantly on the oxazolidine-2,4-dione portion of vinclozolin. The metabolites were identified as the 3R- and 3S- isomers of 3',5'-dichloro-2,3,4-trihydroxy-2-methylbutyranilide, N-(2-hydroxy-2-methyl-1-oxobuten-3-yl)-3,5-dichlorophenyl-1-carbamic acid, and 3',5'-dichloro-2-hydroxy-2-methylbut-3-enanilide. The enanilide compound has been reported previously as a plant and mammalian metabolite and is implicated to contain antiandrogenic activity. The 3R- and 3S- isomers of 3',5'-dichloro-2,3,4-trihydroxy-2-methylbutyranilide are novel metabolites.     

Initial white rot type dominance of wood decomposition and its functional consequences in a regenerating tropical dry forest

Efforts to model woody debris dynamics are limited by our empirical understanding of the patterns and drivers of decomposition. This knowledge gap is significant in tropical forests, particularly in the dry tropics where research has been minimal and where forest regeneration is a management priority. Here, we coupled trait-function relationships in decomposing logs with indices of microbial and insect activity in a regenerating Costa Rican dry forest. We cut and placed logs (∼18 cm dia) of eight tree species in ground contact at two sites. We assessed density loss and element dynamics in sapwood and heartwood twice annually over two years. At time 0 and year 2, we measured lignin, nitrogen, structural carbohydrates, extractives, insect galleries, and two residue ‘signatures’ of fungal rot type: dilute alkali solubility (DAS; higher for brown rot) and lignin:glucan loss (higher for white rot). After two years, sapwood mean density losses ranged from 11.6 to 44.4% among tree species (excluding one thoroughly-degraded species). The best predictor of sapwood density loss was initial pH, but this correlation was negative, contrasting positive correlations proposed for temperate forests. Mean heartwood density losses were consistently less than those in sapwood, and although heartwood extractives contents were as high as 16.4%, trait correlations were insignificant. Insect galleries contributed little to density loss (<3%), and DAS and lignin loss patterns indicated dominance by white rot fungi. This was often matched by dense fungal zone line patterns (spalting), outlining many small territories. Perhaps as a consequence, element patterns were spatially variable, with overall trends roughly similar to those from temperate studies (e.g., Ca gain, P, K loss). Estimated CO₂ fluxes from logs ranged from ∼25 to 75% percent of annual fluxes from litter fall. This collectively implies an important role for wood decomposition in dry forest carbon cycling, and in our case, it shows an interesting pattern suggesting high decomposer spatial complexity but low functional diversity.     

Aspects of the adsorption and degradation of isoproturon in a heavy clay soil

Abstract. Degradation of isoproturon in a heavy clay soil followed first-order reaction kinetics with half-lives at 15 °C of 27 and 208 days in the topsoil and subsoil, respectively. Adsorption when shaken with 3 mm sieved samples of the soil fitted the empirical Freundlich relationship with k values of 3.25 in the topsoil and 1.06 in the subsoil. Adsorption in a static system with different sized aggregates of soil did not reach equilibrium, even after 24 hours contact, and the rate of adsorption was slower with larger aggregates. Following an adsorption period of 24 hours, desorption equilibrium was reached more rapidly with larger (6–10 mm) than with smaller (<3 mm) aggregates. Adsorption isotherms measured in a static system with a soil:water ratio typical of field conditions in winter also indicated less adsorption than that measured in shaken, laboratory systems with low soil:water ratios. The rate of change in water extractable residues of the herbicide was more rapid than that of total extract-able residues following application of isoproturon to the heavy clay soil in the field. The implications of the results for isoproturon leaching under field conditions are discussed.     

Spatial heterogeneity in the metabolism and dynamics of isoproturon degrading microbial communities in soil

The characteristics of isoproturon [3-(4-isopropylphenyl)-1,1-dimethylurea] metabolism were investigated in soil taken from two transects within a single field. Along transect 1, complete degradation of the parent compound occurred within 18 days, and over 40% of ring C had been metabolised after 65 days. In these soils, both side chain and ring metabolism had a short lag phase, followed by a period of rapid degradation. Along transect 2, the rate of side chain metabolism was highly variable, and 20% of ring C had been metabolised after 65 days. The dynamics of isoproturon ring C metabolism were typical of cometabolic degradation, even at sites in which enhanced side chain metabolism occurred. Isoproturon degrading organisms were found in similar numbers in soil from the two transects prior to isoproturon application. In soils from transect 1, there was considerable proliferation of degrader organisms during the lag phase, in which 40% of the isoproturon was degraded. In most soils from transect 2, there had been no proliferation of isoproturon metabolising organisms at the point of 40% metabolism. Before enhanced degradation could develop, there was clearly a requirement for the isoproturon metabolising community to reach a threshold size. Immobilisation of isoproturon ring C into the microbial biomass and formation of bound residues was lower in soil from transect 2 relative to soil from transect 1. We conclude that the in-field spatial heterogeneity of isoproturon side chain and ring metabolism, the formation of bound residues and the immobilisation of pesticide residues in the biomass, results from variation in the development and significance of growth linked and cometabolic degradation.     

微生物降解阿特拉津的研究进展

除草剂阿特拉津长期使用所造成环境污染问题的日益加重,受污染土壤、水体的生物降解、生态修复等诸多问题也受到人们的广泛关注,本文综述了降解阿特拉津的微生物类群、阿特拉津降解酶以及微生物对阿特拉津的作用方式和降解途径,并对其应用前景进行了展望。     

Degradation of Sevin by soil microorganisms

Microorganisms capable of transforming the pesticide 1-naphthyl N-methyl-carbamate (Sevin) were isolated from soil. Three isolates were able to accelerate the hydrolysis of Sevin to 1-naphthol. Several unidentified intermediates were separated by thin-layer chromatography and also by following the decomposition of Sevin-methyl-¹⁴C. Since 1-naphthol is a biological as well as a chemical decomposition product of Sevin, its transformation by the isolated microbes was also studied. A fungus, identified as Fusarium solani, altered 1-naphthol rapidly. Whereas one strain of bacterium degraded the hydrolysis product gradually, another strain accumulated it under certain conditions. Mixed cultures of the investigated microbes were more effective in transforming Sevin than pure cultures, and this phenomenon was also observed with 1-naphthol as substrate with the exception of one bacterial strain.     

Degradation of ochratoxin a by Brevibacterium species

The ability to degrade ochratoxin A was studied in different bacteria with a well-known capacity to transform aromatic compounds. Strains belonging to Rhodococcus, Pseudomonas, and Brevibacterium genera were grown in liquid synthetic culture medium containing ochratoxin A. Brevibacterium spp. strains showed 100% degradation of ochratoxin A. Ochratoxin α was detected and identified by high-performance liquid chromatography-mass spectrometry (HPLC-MS) as a degradation product in the cell-free supernatants. The degradation of ochratoxin A is of public concern for food and environmental safety, because it could contribute to the development of new biological ochratoxin A detoxification systems in foodstuffs. In this study, the degradation of ochratoxin A by bacteria belonging to the food chain was demonstrated for the first time.