Preferentially Degraded Research Articles

Magnetic visible-light activated photocatalyst CuFe2O4/Bi2WO6/mpg-C3N4 for the treatment of natural organic matter

Despite growing interest in research on visible-light-driven photocatalysts, reusable photocatalysts have not been extensively developed for the treatment of natural organic matter (NOM), because such development requires an understanding of the complex NOM structures. In this study, we combined the individual benefits of CuFe2O4, Bi2WO6, and mesoporous graphitic carbon nitride (mpg-C3N4) to prepare a magnetic, visible-light-driven photocatalytic composite, CBC-5, for effectively removing NOM in a short period of time. The degradation mechanisms were further explored at the molecular level through ultra-high-resolution mass spectrometry. Broad light absorbance and charge transmission based on a dual S-scheme pathway allowed CBC-5 to generate multiple active agents, OH (49.7 %), O2− (27.6 %), and h+ (24.8 %), which ultimately led to the removal of 7.9 mgC of NOM per 0.9 g of CBC-5 in 6 h. Humic-like fluorophores were preferentially degraded, followed by the generation of simple phenolic components as by-products. Molecular-level investigation revealed that the NOM structures with high degree of unsaturation and functionalization were preferentially attacked by the radicals. Oxygenic groups were formed upon the oxidation of the unsaturated bonds and the functional groups having a low oxidation state of carbon (OSc) before the degradation of the carboxyl-rich alicyclic molecules. NOM degradation was prioritized in the following order: CHON > CHO > CHOS. Oxidative deamination is attributed to the preferential degradation of N-containing compounds, which are partially transformed to CHO compounds. CHOS compounds enriched with aliphatic organosulfates were recalcitrant to photocatalytic oxidation. Thus, CBC-5 demonstrated convenient magnetic recovery, stable performance, and high recyclability and can be applied as a promising NOM treatment agent.

Indigenous functional microbial communities for the preferential degradation of chloroacetamide herbicide S-enantiomers in soil

This study investigated indigenous functional microbial communities associated with the degradation of chloroacetamide herbicides acetochlor (ACE), S-metolachlor (S-MET) and their enantiomers in repeatedly treated soils. The results showed that biodegradation was the main process for the degradation of ACE, S-MET and their enantiomers. Eight dominant bacterial genera associated with the degradation were found: Amycolatopsis, Saccharomonospora, Mycoplasma, Myroides, Mycobacterium, Burkholderia, Afipia, and Kribbella. The S-enantiomers of ACE and S-MET were preferentially degraded, which mainly relied on Amycolatopsis, Saccharomonospora and Kribbella for the ACE S-enantiomer and Amycolatopsis and Saccharomonospora for the S-MET S-enantiomer. Importantly, the relative abundances of Amycolatopsis and Saccharomonospora increased by 146.3%–4467.2% in the S-enantiomer treatments of ACE and S-MET compared with the control, which were significantly higher than that in the corresponding R-enantiomer treatments (25.3%–4168.2%). Both metagenomic and qPCR analyses demonstrated that four genes, ppah, alkb, benA, and p450, were the dominant biodegradation genes (BDGs) potentially involved in the preferential degradation of the S-enantiomers of ACE and S-MET. Furthermore, network analysis suggested that Amycolatopsis, Saccharomonospora, Mycoplasma, Myroides, and Mycobacterium were the potential hosts of these four BDGs. Our findings indicated that Amycolatopsis and Saccharomonospora might play pivotal roles in the preferential degradation of the S-enantiomers of ACE and S-MET.

Impact of dichlorprop on soil microbial community structure and diversity during its enantioselective biodegradation in agricultural soils

Enantioselective biodegradation of racemic dichlorprop in two soils was investigated in the laboratory. Chiral separation of racemic dichlorprop was achieved by using HPLC with Phenomenex Lux Amylose-2. The first-order kinetic model fitted well the dissipation data of racemic dichlorprop and its pure R- and S-enantiomers. S-dichlorprop was preferentially degraded in both soils and enantioselectivity was affected by soil pH. The half-lives (DT50) of S-dichlorprop were 8.22 days in soil A and 8.06 days in soil D, while R-dichlorprop was more persistent with DT50 of 12.93 days in soil A and 12.38 days in soil D, respectively. Dichlorprop dissipated faster in soil D with lower organic matter content. In sterilized soils, neglected dissipation was observed and enantiomer fraction values remained constant, indicating that the enantioselective degradation was mainly controlled by soil microorganisms. Soil microbial community structure and diversity was assessed by Illumina MiSeq sequencing of 16S rRNA genes from dichlorprop and no dichlorprop contaminated microcosms. Compared with controls, dichlorprop application had no significant effect on microbial community structures at phylum level, but increased bacterial diversity and dichlorprop degradation related taxa in both soils. S-dichlorprop preferential degradation might be attributed to the S-enantiomer preferred degraders in the family of Sphingomonadaceae.

Dissolved Organic Phosphorus Utilization by Phytoplankton Reveals Preferential Degradation of Polyphosphates Over Phosphomonoesters

The nutritionally available pool of dissolved organic phosphorus (DOP) supports marine primary productivity in a range of ocean ecosystems but remains poorly resolved. Here, the relative lability of model phosphorous (P) compounds representing the major P(V) bond classes of marine DOP – phosphomonoesters (P-O-C) and phosphoanhydrides (P-O-P) – was assessed in diatom cultures of the genus Thalassiosira, as well as coastal field sites of the western North Atlantic. In diatom samples, maximum enzymatic hydrolysis rates revealed that the P-anhydride bonds of inorganic tripolyphosphate (3poly-P), followed by the P-anhydride bonds of adenosine 5’-triphosphate (ATP), were preferentially degraded relative to the P-monoesters adenosine 5’-monophosphate (AMP) and 4-methylumbelliferone phosphate (MUF-P). Consistent with these rate measurements, targeted proteomics analysis demonstrated that the underlying phosphatase diversity present in diatom samples was dominated by P-anhydride degrading enzymes (inorganic pyrophosphatases and nucleoside triphosphatases). Furthermore, biomass-normalized rates of ATP degradation were always suppressed under P-replete conditions in diatom cultures, but the effect of overall P availability on 3poly-P degradation was inconsistent among diatom strains, suggesting that inorganic polyphosphate (poly-P) degradation may persist irrespective of prevailing P levels in the marine environment. Indeed, the majority of field sites examined in the P-replete coastal western North Atlantic exhibited significantly higher maximum rates of inorganic poly-P hydrolysis relative to P-monoester hydrolysis, which was largely driven by phytoplankton dynamics. Based on these results, the possibility that P-anhydride utilization may contribute comparably or even more substantially than P-esters to community-level P demand, phytoplankton growth, and primary productivity should be considered.

Selective preservation among bacterial alkyl glycerol ether lipid structures during long term oxic and anoxic incubation

Bacterial mono- and dialkyl glycerol ether lipids (MAGEs and DAGEs) are potential powerful lipid biomarkers whose respective diagenetic fate still needs to be precisely assessed. To do so, the lipid content of cultures of an anaerobic bacterium synthesizing both MAGEs and DAGEs was analyzed at different growth stages and after long-term incubation under aerobic or anaerobic conditions. The proportions of the different lipid classes (fatty acids, MAGEs and DAGEs), as well as their structural distributions, did not significantly vary during anaerobic growth under optimal conditions until the stationary phase. Long-term exposure to oxygen (up to 480 days) induced the preferential degradation of fatty acids and MAGEs relative to DAGEs and of sn-1 relative to sn-2 positional isomers of MAGEs. The degradation of fatty acids and MAGEs appeared slower under anaerobic conditions and no specific structures appeared preferentially degraded. All DAGE structures were very well preserved whatever the redox conditions and the time of incubation considered (480 days and 13 years under oxic and anoxic conditions, respectively). The results highlight the excellent diagenetic stability of DAGEs and the much lower potential of preservation of MAGEs, warranting caution for an eventual use of the latter compounds as tracers of environmental or microbial community changes.

Preferential degradation of cognitive networks differentiates Alzheimer's disease from ageing.

Converging evidence from structural, metabolic and functional connectivity MRI suggests that neurodegenerative diseases, such as Alzheimer's disease, target specific neural networks. However, age-related network changes commonly co-occur with neuropathological cascades, limiting efforts to disentangle disease-specific alterations in network function from those associated with normal ageing. Here we elucidate the differential effects of ageing and Alzheimer's disease pathology through simultaneous analyses of two functional connectivity MRI datasets: (i) young participants harbouring highly-penetrant mutations leading to autosomal-dominant Alzheimer's disease from the Dominantly Inherited Alzheimer's Network (DIAN), an Alzheimer's disease cohort in which age-related comorbidities are minimal and likelihood of progression along an Alzheimer's disease trajectory is extremely high; and (ii) young and elderly participants from the Harvard Aging Brain Study, a cohort in which imaging biomarkers of amyloid burden and neurodegeneration can be used to disambiguate ageing alone from preclinical Alzheimer's disease. Consonant with prior reports, we observed the preferential degradation of cognitive (especially the default and dorsal attention networks) over motor and sensory networks in early autosomal-dominant Alzheimer's disease, and found that this distinctive degradation pattern was magnified in more advanced stages of disease. Importantly, a nascent form of the pattern observed across the autosomal-dominant Alzheimer's disease spectrum was also detectable in clinically normal elderly with clear biomarker evidence of Alzheimer's disease pathology (preclinical Alzheimer's disease). At the more granular level of individual connections between node pairs, we observed that connections within cognitive networks were preferentially targeted in Alzheimer's disease (with between network connections relatively spared), and that connections between positively coupled nodes (correlations) were preferentially degraded as compared to connections between negatively coupled nodes (anti-correlations). In contrast, ageing in the absence of Alzheimer's disease biomarkers was characterized by a far less network-specific degradation across cognitive and sensory networks, of between- and within-network connections, and of connections between positively and negatively coupled nodes. We go on to demonstrate that formalizing the differential patterns of network degradation in ageing and Alzheimer's disease may have the practical benefit of yielding connectivity measurements that highlight early Alzheimer's disease-related connectivity changes over those due to age-related processes. Together, the contrasting patterns of connectivity in Alzheimer's disease and ageing add to prior work arguing against Alzheimer's disease as a form of accelerated ageing, and suggest multi-network composite functional connectivity MRI metrics may be useful in the detection of early Alzheimer's disease-specific alterations co-occurring with age-related connectivity changes. More broadly, our findings are consistent with a specific pattern of network degradation associated with the spreading of Alzheimer's disease pathology within targeted neural networks.

Structural modification of hemicelluloses and lignin based on the biorefinery process with white-rot fungal

On the concept of biorefinery, hemicellulosic and lignin fractions were isolated from white-rot fungal Trametes velutina D10149 biodegraded poplar, and the structural modification was elucidated in detail according to the different incubation duration. Transversal-section Raman images showed that the fiber secondary walls were preferentially degraded, whereas the compound middle lamellae, including the cell corner regions, were mainly intact after 16 weeks incubation. More importantly, lignin and carbohydrates were simultaneously removed within the fiber secondary wall. From wet chemistry analysis, the yields and structural properties for both hemicellulosic and lignin fractions were not significantly altered. The synergistic effect of ligninolytic system finally obviously appeared after 16 weeks incubation, evidenced by the remarkable decrement of hemicellulose and lignin molecular weights. Additionally, the preferential degradation of S units in lignin biomacromolecule was further confirmed by composition analysis of cell wall phenolics and the integration of 2D NMR correlations in the aromatic region.

Cytochemical and immunocytochemical characterization of wood decayed by the white rot fungus Pycnoporus sanguineus I. preferential lignin degradation prior to hemicelluloses in Norway spruce wood

Degradation of lignin and non-cellulosic polysaccharides (pectins and hemicelluloses) in Norway spruce wood (softwood) by the white rot fungus Pycnoporus sanguineus was investigated using transmission electron microscopy coupled with immunocytochemistry. P. sanguineus produced selective decay in xylem cells including tracheids, ray tracheids and ray parenchyma cells. Lignin was preferentially removed first from cell walls with hemicelluloses (xylan and mannan) and cellulose remaining. Lignin in compound middle lamella (CML) regions of tracheids was also preferentially degraded prior to degradation of xyloglucan (hemicellulose). This differs from the previous concept of wood decay by selective white rot fungi demonstrating concomitant degradation of lignin and hemicelluloses. In contrast, no clear preferential degradation of lignin prior to pectins and hemicelluloses was observed in middle lamella cell corner (MLcc) regions of tracheids which were the last regions to be attacked by the fungus. Micromorphologically, prominent cell separation between tracheids by delignification of CML regions before complete degradation of secondary cell walls was observed as evidence of selective decay. Variations in resistance to decay by the fungus depending on cell wall orientation (radial vs. tangential) of tracheids and between cell types were also observed.

Structure-dependent degradation of polar compounds in weathered oils observed by atmospheric pressure photo-ionization hydrogen/deuterium exchange ultrahigh resolution mass spectrometry

The resin fractions of fresh mixtures of three oils spilled during the M/V Hebei Spirit oil spill, as well as weathered oils collected at weathering stages II and IV from the oil spill site were analyzed and compared by atmospheric pressure photo-ionization hydrogen/deuterium exchange mass spectrometry (HDX MS). The significantly decreased abundance of N+ and [N−H+D]+ ions suggested that secondary and tertiary amine-containing compounds were preferentially degraded during the early stage of weathering. [N+H]+ and [N+D]+ ions previously attributed to pyridine-type compounds degraded more slowly than secondary and tertiary amine-containing compounds. The preferential degradation of nitrogen-containing compounds was confirmed by photo-degradation experiments using 15 standard compounds. In addition, significant increases of [S1O1+H]+ and [S1O1+D]+ ions with higher DBE values were observed from fresh oil mixtures as compared to stages II and IV samples, and that could be linked with the decrease of higher DBE compounds of the S1 class. This study presented convincing arguments and evidence demonstrating that secondary and tertiary amines were more vulnerable to photo-degradation than compounds containing pyridine, and hence, preferential degradation depending on chemical structures must be considered in the production of hazardous or toxic components.

Preferential degradation of polyphenols from Sphagnum – 4-Isopropenylphenol as a proxy for past hydrological conditions in Sphagnum-dominated peat

The net accumulation of remains of Sphagnum spp. is fundamental to the development of many peatlands. The effect of polyphenols from Sphagnum on decomposition processes is frequently cited but has barely been studied. The central area of the Rödmossamyran peatland (Sweden) is an open lawn that consists mostly of Sphagnum spp. with a very low contribution from vascular plants. In order to determine the effects of decay on sphagnum phenols, 53 samples of a 2.7m deep core from this lawn were analysed with pyrolysis gas chromatography–mass spectrometry (pyrolysis-GC–MS) and compared with more traditional decomposition proxies such as C/N ratio, UV light transmission of alkaline peat extracts, and bulk density. Factor analysis of 72 quantified pyrolysis products suggested that the variation in 4-isopropenylphenol was largely determined by aerobic decomposition instead of Sphagnum abundance. In order to evaluate the effects of aerobic decay in Sphagnum peat, down-core records from different climatic regions were compared using molecular markers for plant biopolymers and C/N ratio. These included markers for lignin from vascular plants ((di)methoxyphenols), polyphenols from Sphagnum spp. (4-isopropenylphenol), and cellulose (levoglucosan). Our results indicate that polyphenols from Sphagnum are preferentially degraded over polysaccharides; consequently the variability of the marker for sphagnum acid, 4-isopropenylphenol, was found indicative of decomposition instead of reflecting the abundance of Sphagnum remains. The fact that 4-isopropenylphenol is aerobically degraded in combination with its specificity for Sphagnum spp. makes it a consistent indicator of past hydrological conditions in Sphagnum-dominated peat. In contrast, the variability of C/N records in Sphagnum-dominated peat was influenced by both vegetation shifts and decomposition, and the dominant effect differed between the studied peatlands. Our results provide direction for modelling studies that try to predict possible feedback mechanisms between peatlands and future climate change, and indicate that the focus in Sphagnum decay studies should be on carbohydrates rather than on phenolic compounds.

Degradation of swept-parameter VEP responses by neutral density filters in amblyopic and normal subjects.

To determine whether objective visual function, measured by swept-parameter visual evoked potential (sVEP), is preferentially degraded by neutral density filtration (NDF) in normal control and fellow eyes compared to amblyopic eyes, and to determine whether the response to NDF is a function of stimulus type, using grating and vernier stimuli. Monocular Snellen acuity and both grating and vernier sVEP responses were measured in each eye of 23 children or adolescents with amblyopia and 21 visually and neurologically normal children or adolescents. Acuity and sVEP responses were measured with and without a 2.0 log unit neutral density filter before the viewing eye. Suprathreshold sVEP grating responses were more sensitive than vernier to degradation by amblyopia in the unfiltered state and to NDF-induced preferential degradation of responses from fellow and normal control eyes. For threshold measurements, on the other hand, vernier responses were more sensitive to degradation by amblyopia in the unfiltered state and to NDF-induced preferential depression. Threshold vernier responses of amblyopic eyes were paradoxically enhanced by NDF. Neutral density filtration causes preferential degradation of both threshold and suprathreshold sVEP responses in normal control eyes and fellow eyes of amblyopes, compared to amblyopic eyes. The degradation is stimulus specific and dependent upon whether threshold or suprathreshold responses are measured. Grating responses are more likely to identify suprathreshold abnormalities, while vernier stimuli are more likely to detect threshold abnormalities. These findings may be used to optimize the stimulus parameters and design of future studies utilizing evoked potential techniques in amblyopic subjects.

Stereoselective transformation of triadimefon to metabolite triadimenol in wheat and soil under field conditions

Racemic triadimefon (TF) was applied to wheat and soil at three sites (Beijing, Huaibei, and Zhengzhou in China) under open field conditions. Its enantioselective degradation and stereoselective transformation to the major metabolite, triadimenol (TN), in wheat straw, grain and soil were investigated. At all sites, the degradation of TF enantiomers in straw and soil followed first-order kinetics. In soil from Beijing and Zhengzhou R-(−)-TF was preferentially degraded; however, preferential enantioselective degradations were not recorded in soil from Huaibei or in the straw from all sites. There were noticeable differences in the stereoselective formation of TN stereoisomers in all straw and soil samples. TN diastereomer A with high animal toxicity was preferentially produced via a reductive reaction in straw. In contrast, diastereomer B, was preferential in soil across the experimental period. Different TN concentrations were found in the order of SR-(−)-TN>RR-(+)-TN>RS-(+)-TN>SS-(−)-TN in straw, and RR-(+)-TN>SS-(−)-TN>SR-(−)-TN>RS-(+)-TN in soil. Neither TF nor TN was found in wheat grain at harvest. Because of differences in degradation, formation, and toxicity, the characterization of enantiomers and stereoisomers in this study contributes toward comprehensively assessing the fate and risk of chiral agrochemicals in the environment and food.

Comparison of abiotic and biotic degradation of PDLLA, PCL and partially miscible PDLLA/PCL blend

Important differences between the biotic and abiotic hydrolysis of neat poly(dl-lactide) (PDLLA), poly(ε-caprolactone) (PCL) and a partially miscible PDLLA/PCL blend were found in this work. In abiotic conditions, the degradation process of all the studied specimens mainly proceeded by a bulk degradation mechanism and the diffusion rate of degradation products into the medium was relatively slow after 18weeks. The hydrophobic and semi-crystalline nature of PCL matrix made this polymer very stable against abiotic hydrolysis, whereas the degradation of PDLLA proceeded much faster due to its amorphous structure. In the first stages of degradation, PDLLA/PCL blend showed that its rich continuous PDLLA phase catalyzed the hydrolysis of the PCL phase, while the low content of PCL molecules partially delayed hydrolysis of PDLLA matrix. In compost, higher levels of degradation were found for all the studied systems during the first 12weeks of degradation, indicating an important effect of enzymes from microbes in compost on the degradation of PDLLA and PCL. Neat PDLLA and PDLLA/PCL blend seemed to degrade mainly by a bulk degradation mechanism, at least during the first 12weeks, such as previously observed in abiotic conditions, whereas PCL was preferentially degraded by a surface mechanism due to a very strong catalytic effect of microorganisms on its degradation. Contrary to the abiotic degradation, it was observed that the presence of a low content of PCL molecules in the rich-PDLLA blend did not interfere with the degradation trend of PDLLA in compost, and that the continuous PDLLA phase could partially suppress the biotic degradation of PCL molecules.In general, abiotic and biotic hydrolysis of PDLLA/PCL blends seems to be a complex phenomenon depending not only on the mixing ratio of both polymers but also on their crystallinity, miscibility level of polymer phases and the preferential degradation mechanism of each polymer component. If blends of PDLLA/PCL present a similar level of miscibility, it would be possible to estimate if the presence of the PDLLA or PCL phase could have a general catalytic or delaying role in the blend during the initial degradation stages, depending on which environment they are subjected to and the content of each polymer phase in the blend.

Bacterial community dynamics during the preferential degradation of aromatic hydrocarbons by a microbial consortium

The aims of this study were to identify the bacteria responsible for the rapid degradation of aromatic hydrocarbons, and to determine the roles of bacterial species in the microbial consortium. The population changes of the four major bacterial groups, namely Burkholderia spp., Achromobacter spp./Alcaligenes spp., Cupriavidus spp., and Rhodanobacter spp. in the Y consortium that preferentially degraded petroleum oil-derived aromatic hydrocarbons were assessed using quantitative real-time polymerase chain reaction (q-PCR). P-xylene was used as a representative aromatic compound, decane as a representative aliphatic compound, p-xylene-decane as a representative hydrocarbon mixture, and kerosene as a representative petroleum-based oil. The results showed that the remarkable increase of Burkholderia spp. coincided with the rapid degradation of aromatic hydrocarbons in kerosene, and p-xylene in single and dual-substrate cultures. Cupriavidus spp. significantly increased when decane was rapidly depleted. Achromobacter spp.,/Alcaligenes spp., and Rhodanobacter spp. were initially inhibited by the presence of aromatic hydrocarbons and seemed not to be active in hydrocarbon degradation, but utilized the metabolic products. This work provided an alternative way to explain the contribution of different microbial species in the degradation of hydrocarbon fractions. The behavior of the consortium is of interest in the context of the bioremediation of the more toxic aromatic hydrocarbons in environments contaminated by petroleum products.

Enantioselective Degradation of Indoxacarb in Cabbage and Soil under Field Conditions

The enantioselective degradation of indoxacarb in cabbage and soil has been investigated in Beijing and Anhui under open conditions. Indoxacarb enantiomers in samples were extracted with acetonitrile, cleaned up by florisil SPE column, separated on high performance liquid chromatography with a cellulose-tris-(3, 5-dimethylphenylcarbamate)-based chiral stationary phase (CDMPC-CSP), and determined by a photodiode array detector. The validation of the developed method by fortification rac-indoxcarb in cabbage and soil showed good accuracy and precision. The results of field trials indicated that the dissipation of indoxacarb enantiomers followed pseudo-first-order kinetics or first-order kinetics in cabbage and soil at two locations. The half-lives of two enantiomers in cabbage ranged from 2.8 to 4.6 d which were shorter than those in soil ranging from 23 to 35 d. The changes of enantiomeric fraction values proved that enantioselective degradation of indoxacarb happened in cabbage and soil. The (-)-indoxacarb showed faster degradation in the Beijing cabbage, whereas in the Anhui cabbage, (+)-indoxacarb preferentially degraded. In soil, preferential degradation of (+)-indoxacarb was observed at two locations.

Micromorphological characteristics and lignin distribution in bamboo (Phyllostachys pubescens) degraded by the white rot fungus Lentinus edodes

Abstract Little is known about the decay pattern of bamboo by wood decay fungi, and the information available on fungal degradation of wood from other plant taxa cannot form the basis for understanding wood decay in bamboo because of differences in lignin composition and distribution. The present work was undertaken to elucidate the degradation pattern of bamboo by a lignin-degrading white rot fungus Lentinus edodes using various microscopic techniques, with a particular focus on the relation of bamboo lignin composition to the decay patterns produced by this fungus. Small blocks of bamboo, Phyllostachys pubescens, were examined after 16 weeks of incubation with the white rot fungus L. edodes. The compound middle lamellae (CML), including the cell corner regions, were preferentially degraded at an early stage of decay, whereas the fiber secondary walls remained largely intact at this point. Bamboo fiber walls were also eroded from the cell lumen side but the extent of degradation was limited. The FT-IR bands assigned to lignin exhibited a significant decrease. Cellular ultraviolet microspectrophotometric investigation showed that CML and vessel walls were composed of not only guaiacyl and syringyl unit (GS lignin) but also grass lignin. In contrast, the secondary wall of fibers consisted mainly of the GS lignin. Even though the CML and vessel walls exhibited higher lignin concentration, these cell walls were nevertheless degraded. The preferential degradation of the CML over the fiber secondary walls strongly suggested the involvement of not only enzyme systems of the white rot fungus but also a relationship to physicochemical properties of bamboo cell walls, particularly the influence of lignin composition and distribution.

Diastereomer selectivity in the degradation of a lignin model compound of the arylglycerol β-aryl ether type by white-rot fungi

Mixtures of about equal amounts of the diastereomers of arylglycerol β-aryl ether 1-(3,4-dimethoxyphenyl)-2-(2-methoxyphenoxy)-1,3-propanediol ( 1) were added to cultures of Trametes versicolor, Phanerochaete chrysosporium, and Pycnoporus cinnabarinus. Samples taken from the fungal cultures were analyzed with respect to the fraction of 1 degraded, the erythro: threo ratio in the remaining 1, and the product profile, using HPLC and UV-diode array detector. The P. cinnabarinus cultures exhibited laccase activity and partially decolorized Remazol Brilliant Blue R (RBBR), but they did not degrade 1 under the conditions studied. Cultures of T. versicolor and P. chrysosporium preferentially degraded the threo isomer of 1. This is consistent with the fact that the product profiles showed larger amounts of threo- than erythro-veratrylglycerol. The results can be discussed in relation to the diastereomer selectivity of various oxidants implicated in lignin degradation by white-rot fungi. Preferential degradation of the threo isomer of arylglycerol β-aryl ethers is not in agreement with the action of Fenton's reagent, since this reagent does not exhibit any stereopreference.

Degradation and modification of fats, oils and grease by commercial microbial supplements

Fats, oils and greases (FOGs) in wastewater create problems including the production of foul odours, the blockage of sewer lines and may interfere with the proper operation of sewage treatment works. Removal of FOG from wastewater is thus critically important to ensure that wastewater is disposed of efficiently and economically. In this study, the ability of commercial microbial supplements to degrade fat/oil under laboratory conditions was investigated. One of the multi-species supplements examined was capable of significantly enhancing the degradation of several fats and oils by 37–62%, in contrast to all of the single-species supplements which had no significant effect. The multi-species supplement showed no preferential cleavage or degradation of fatty acids in a range of FOGs, whilst wastewater-associated bacteria preferentially degraded octadecatrienoic acid (18:3ω3) and octadecadienoic acid (18:2ω6). A semi-solid, sticky material, likely to cause blockages in pipework and sewer lines formed when the oil was incubated in the presence of wastewater bacteria. The sticky material was enriched in saturated and mono-unsaturated fatty acids and depleted in polyunsaturated fatty acids relative to the original oil, most likely reflecting preferential fatty acid usage by the bacteria. The production of this semi-solid material by the wastewater bacteria was significantly reduced by the presence of the multi-species product, indicating that commercial supplements have the potential to minimize FOG accumulation and blockages in grease traps and sewer lines as well as enhancing FOG degradation.

Sources and composition of hydrolysable aliphatic lipids and phenols in soils from western Canada

The hydrolyzable lipid composition of grassland and forest soils, and their overlying vegetation (i.e., prairie grasses, aspen, and pine) were analyzed by alkaline hydrolysis and gas chromatography–mass spectrometry (GC–MS). Prior to hydrolysis, samples were pre-extracted with organic solvents to remove free lipids. The hydrolysis products from soils and plants consisted of series of aliphatic lipids (alkanoic acids, alkanols, alkanedioic acids, ω-hydroxyalkanoic acids, α-hydroxyalkanoic acids, mid-chain-substituted hydroxy and epoxy acids), benzyls and phenols. Cutin, suberin and plant waxes are believed to be the major sources for the detected lipids. The composition of cutin and suberin monomers in the soils is similar to the patterns observed in the corresponding vegetation reflecting the preservation of plant biomolecules such as cutin and suberin. The long-chain ω-hydroxyalkanoic and α,ω-alkanedioic acids (>C 16) as observed in the grass roots are typical biomarkers for suberin and indicate a major input of root biomass to the soils. Mid-chain-substituted hydroxy and epoxy acids (C 14–C 18) derived from the cutin of leaves were detected in the soils but in low abundance, indicating only a minor input of leaf material. A parameter to estimate the input of leaf vs. root organic matter is developed and applied based on the pattern and distribution of observed cutin and suberin biomarkers. The cutin/suberin ratios decrease from plant material to the mineral horizons likely due to the steady input of fresh root material in the soil horizons rather than the preferential degradation of cutin. The decrease of total hydrolysis products from the overlying vegetation to the soil is consistent with the degradation of hydrolysable biomarkers. Long-chain ω-hydroxyalkanoic and α,ω-alkanedioic acids derived from suberin are observed to decompose without preference of specific constituents. In contrast, mid-chain-substituted hydroxy and epoxy acids appear to be preferentially degraded in soils compared to other cutin and suberin monomers such as ω-hydroxyalkanoic acids. However, the steady input of roots which are rich in ω-hydroxyalkanoic acids and low in mid-chain-substituted acids may in part influence the degradation parameters resulting in an apparent higher rate of degradation.

Why Are Young and Old Repetitive Elements Distributed Differently in the Human Genome?

Alu elements are not distributed homogeneously throughout the human genome: old elements are preferentially found in the GC-rich parts of the genome, while young Alus are more often found in the GC-poor parts of the genome. The process giving rise to this differential distribution remains poorly understood. Here we investigate whether this pattern could be due to a preferential degradation of Alu elements integrated in GC-poor regions by small indel mutations. We aligned 5.1 Mb of human and chimpanzee sequences and examined whether the rate of insertion and deletion inside Alu elements differed according to the base composition surrounding them. We found that Alu elements are not preferentially degraded in GC-poor regions by indel events. We also looked at whether very young L1 elements show the same change in distribution compared to older ones. This analysis indicated that L1 elements also show a shift in their distribution, although we could not assess it as precisely as for Alu elements. We propose that the differential distribution of Alu elements is likely to be due to a change in their pattern of insertion or their probability of fixation through evolutionary time.