Biocalorimetry-aided monitoring of fungal pretreatment of lignocellulosic agricultural residues.

The present study aimed to investigate whether and how non-invasive biocalorimetric measurements could serve for process monitoring of fungal pretreatment during solid-state fermentation (SSF) of lignocellulosic agricultural residues such as wheat straw. Seven filamentous fungi representing different lignocellulose decay types were employed. Water-soluble sugars being immediately available after fungal pretreatment and those becoming water-extractable after enzymatic digestion of pretreated wheat straw with hydrolysing (hemi)cellulases were considered to constitute the total bioaccessible sugar fraction. The latter was used to indicate the success of pretreatments and linked to corresponding species-specific metabolic heat yield coefficients (YQ/X) derived from metabolic heat flux measurements during fungal wheat straw colonisation. An YQ/X range of about 120 to 140 kJ/g was seemingly optimal for pretreatment upon consideration of all investigated fungi and application of a non-linear Gaussian fitting model. Upon exclusion from analysis of the brown-rot basidiomycete Gloeophyllum trabeum, which differs from all other here investigated fungi in employing extracellular Fenton chemistry for lignocellulose decomposition, a linear relationship where amounts of total bioaccessible sugars were suggested to increase with increasing YQ/X values was obtained. It remains to be elucidated whether an YQ/X range being optimal for fungal pretreatment could firmly be established, or if the sugar accessibility for post-treatment generally increases with increasing YQ/X values as long as "conventional" enzymatic, i.e. (hemi)cellulase-based, lignocellulose decomposition mechanisms are operative. In any case, metabolic heat measurement-derived parameters such as YQ/X values may become very valuable tools supporting the assessment of the suitability of different fungal species for pretreatment of lignocellulosic substrates. KEY POINTS: • Biocalorimetry was used to monitor wheat straw pretreatment with seven filamentous fungi. • Metabolic heat yield coefficients (YQ/X) seem to indicate pretreatment success. • YQ/X values may support the selection of suitable fungal strains for pretreatment.

Continuous operation of fungal wheel reactor based on solid-state fermentation for the removal of pharmaceutical and personal care products.

Wood-rotting fungi and their enzymatic systems represent promising biocatalysts for the removal of pharmaceuticals and personal care products (PPCPs) from wastewater. We designed a fungal wheel reactor (FWR) based on solid-state fermentation (SSF) of Trametes versicolor and a lignocellulosic substrate, which was used as an immobilization carrier for fungal biomass and the sole initial nutrient source for producing fungal oxidative enzymes. Three pharmaceutical and personal care products, acetaminophen, bisphenol A and carbamazepine, were spiked into the synthetic wastewater and the treatment was carried out under non-sterile conditions. Acetaminophen was completely removed from the FWR until laccase was observed. The acetaminophen removal efficiency was retrieved by replacing the fungal wheel with fresh SSF products. Bisphenol A and carbamazepine were removed via enzymatic activity and adsorption. When the fungal wheel was replaced, acetaminophen began to be completely removed, even after laccase depletion. The microbial community analysis indicated that the continuous removal of acetaminophen was mainly due to the high proportion of T. versicolor. The relative abundance of the co-occurring microbial community might be responsible for the divergence in acetaminophen removal between two of fungal wheel-replaced reactors. Overall, FWRs are promising tools for the removal of PPCPs by highly reactive enzymatic mechanisms as well as adsorption on the carrier surface. By replacing SSF and settled microbial communities, FWRs may continuously contribute to bioremediation over a long-term period.

Fungal Lignocellulose Utilisation Strategies from a Bioenergetic Perspective: Quantification of Related Functional Traits Using Biocalorimetry.

In the present study, we investigated whether a non-invasive metabolic heat flux analysis could serve the determination of the functional traits in free-living saprotrophic decomposer fungi and aid the prediction of fungal influences on ecosystem processes. For this, seven fungi, including ascomycete, basidiomycete, and zygomycete species, were investigated in a standardised laboratory environment, employing wheat straw as a globally relevant lignocellulosic substrate. Our study demonstrates that biocalorimetry can be employed successfully to determine growth-related fungal activity parameters, such as apparent maximum growth rates (AMGR), cultivation times until the observable onset of fungal growth at AMGR (tAMGR), quotients formed from the AMGR and tAMGR (herein referred to as competitive growth potential, CGP), and heat yield coefficients (YQ/X), the latter indicating the degree of resource investment into fungal biomass versus other functional attributes. These parameters seem suitable to link fungal potentials for biomass production to corresponding ecological strategies employed during resource utilisation, and therefore may be considered as fungal life history traits. A close connection exists between the CGP and YQ/X values, which suggests an interpretation that relates to fungal life history strategies.

pH Distribution along Growing Fungal Hyphae at Microscale.

Creating unique microenvironments, hyphal surfaces and their surroundings allow for spatially distinct microbial interactions and functions at the microscale. Using a microfluidic system and pH-sensitive whole-cell bioreporters (Synechocystis sp. PCC6803) attached to hyphae, we spatially resolved the pH along surfaces of growing hyphae of the basidiomycete Coprinopsis cinerea. Time-lapse microscopy analysis of ratiometric fluorescence signals of >2400 individual bioreporters revealed an overall pH drop from 6.3 ± 0.4 (n = 2441) to 5.0 ± 0.3 (n = 2497) within 7 h after pH bioreporter loading to hyphal surfaces. The pH along hyphal surfaces varied significantly (p < 0.05), with pH at hyphal tips being on average ~0.8 pH units lower than at more mature hyphal parts near the entrance of the microfluidic observation chamber. Our data represent the first dynamic in vitro analysis of surface pH along growing hyphae at the micrometre scale. Such knowledge may improve our understanding of spatial, pH-dependent hyphal processes, such as the degradation of organic matter or mineral weathering.

Extracellular degradation of a polyurethane oligomer involving outer membrane vesicles and further insights on the degradation of 2,4-diaminotoluene in Pseudomonas capeferrum TDA1.

The continuing reports of plastic pollution in various ecosystems highlight the threat posed by the ever-increasing consumption of synthetic polymers. Therefore, Pseudomonas capeferrum TDA1, a strain recently isolated from a plastic dump site, was examined further regarding its ability to degrade polyurethane (PU) compounds. The previously reported degradation pathway for 2,4-toluene diamine, a precursor and degradation intermediate of PU, could be confirmed by RNA-seq in this organism. In addition, different cell fractions of cells grown on a PU oligomer were tested for extracellular hydrolytic activity using a standard assay. Strikingly, purified outer membrane vesicles (OMV) of P. capeferrum TDA1 grown on a PU oligomer showed higher esterase activity than cell pellets. Hydrolases in the OMV fraction possibly involved in extracellular PU degradation were identified by mass spectrometry. On this basis, we propose a model for extracellular degradation of polyester-based PUs by P. capeferrum TDA1 involving the role of OMVs in synthetic polymer degradation.

Applicability and information value of biocalorimetry for the monitoring of fungal solid-state fermentation of lignocellulosic agricultural by-products.

The applicability of biocalorimetry for monitoring fungal conversion of lignocellulosic agricultural by-products during solid-state fermentation (SSF) was substantiated through linking the non-invasive measurement of metabolic heat fluxes to conventional invasive determination of fungal activity (growth, substrate degradation, enzyme activity) parameters. For this, the fast-growing, cellulose-utilising ascomycete Stachybotrys chlorohalonata and the comparatively slow-growing litter-decay basidiomycete Stropharia rugosoannulata were investigated as model organisms during growth on solid wheat straw. Both biocalorimetric and non-calorimetric data may suggest R (ruderal)- and C (combative)-selected life history strategies in S. chlorohalonata and S. rugosoannulata, respectively. For both species, a strong linear correlation of the released metabolic heat with the corresponding fungal biomass was observed. Species-specific YQ/X values (metabolic heat released per fungal biomass unit) were obtained, which potentially enable use of biocalorimetric signals for the quantification of fungal biomass during single-species SSF processes. Moreover, YQ/X values may also indicate different fungal life history strategies and therefore be considered as useful parameters aiding fungal ecology research.

Evidence for Lignocellulose-Decomposing Enzymes in the Genome and Transcriptome of the Aquatic Hyphomycete Clavariopsis aquatica.

Fungi are ecologically outstanding decomposers of lignocellulose. Fungal lignocellulose degradation is prominent in saprotrophic Ascomycota and Basidiomycota of the subkingdom Dikarya. Despite ascomycetes dominating the Dikarya inventory of aquatic environments, genome and transcriptome data relating to enzymes involved in lignocellulose decay remain limited to terrestrial representatives of these phyla. We sequenced the genome of an exclusively aquatic ascomycete (the aquatic hyphomycete Clavariopsis aquatica), documented the presence of genes for the modification of lignocellulose and its constituents, and compared differential gene expression between C. aquatica cultivated on lignocellulosic and sugar-rich substrates. We identified potential peroxidases, laccases, and cytochrome P450 monooxygenases, several of which were differentially expressed when experimentally grown on different substrates. Additionally, we found indications for the regulation of pathways for cellulose and hemicellulose degradation. Our results suggest that C. aquatica is able to modify lignin to some extent, detoxify aromatic lignin constituents, or both. Such characteristics would be expected to facilitate the use of carbohydrate components of lignocellulose as carbon and energy sources.

Cultivation of filamentous fungi for attack on synthetic polymers via biological Fenton chemistry.

Environmental pollution with synthetic polymers (commonly named plastics) nowadays poses serious threats to the environment and human health. Unfortunately, most conventional plastics are highly recalcitrant even under conditions known to be favorable for microbial degradation. Expanding the knowledge regarding opportunities and limitations of the microbial degradability of plastics would largely contribute to the development of adequate decontamination and management strategies for plastic pollution. This chapter provides cultivation approaches to be applied for the characterization of eco-physiologically diverse asco- and basidiomycete fungi with respect to their ability to attack solid and water-soluble synthetic polymers with the help of quinone redox cycling-based Fenton-type reactions, which result in the production of highly reactive hydroxyl radicals. These reactive oxygen species are the strongest oxidants known from biological systems. However, their potential employment by fungi dwelling in diverse habitats as a biodegradation tool to attack synthetic polymers is still insufficiently explored.

Illuminate the hidden: in vivo mapping of microscale pH in the mycosphere using a novel whole-cell biosensor.

The pH of an environment is both a driver and the result of diversity and functioning of microbial habitats such as the area affected by fungal hyphae (mycosphere). Here we used a novel pH-sensitive bioreporter, Synechocystis sp. PCC6803_peripHlu, and ratiometric fluorescence microscopy, to spatially and temporally resolve the mycosphere pH at the micrometre scale. Hyphae of the basidiomycete Coprionopsis cinerea were allowed to overgrow immobilised and homogeneously embedded pH bioreporters in an agarose microcosm. Signals of >700 individual cells in an area of 0.4 × 0.8 mm were observed over time and used to create highly resolved (3 × 3 µm) pH maps using geostatistical approaches. C. cinerea changed the pH of the agarose from 6.9 to ca. 5.0 after 48 h with hyphal tips modifying pH in their vicinity up to 1.8 mm. pH mapping revealed distinct microscale spatial variability and temporally stable gradients between pH 4.4 and 5.8 over distances of ≈20 µm. This is the first in vivo mapping of a mycosphere pH landscape at the microscale. It underpins the previously hypothesised establishment of pH gradients serving to create spatially distinct mycosphere reaction zones.

Biotransformation of Phthalate Plasticizers and Bisphenol A by Marine-Derived, Freshwater, and Terrestrial Fungi.

Phthalate esters (PEs, Phthalates) are environmentally ubiquitous as a result of their extensive use as plasticizers and additives in diverse consumer products. Considerable concern relates to their reported xenoestrogenicity and consequently, microbial-based attenuation of environmental PE concentrations is of interest to combat harmful downstream effects. Fungal PE catabolism has received less attention than that by bacteria, and particularly fungi dwelling within aquatic environments remain largely overlooked in this respect. We have compared the biocatalytic and biosorptive removal rates of di-n-butyl phthalate (DBP) and diethyl phthalate (DEP), chosen to represent two environmentally prominent PEs of differing structure and hydrophobicity, by marine-, freshwater-, and terrestrial-derived fungal strains. Bisphenol A, both an extensively used plastic additive and prominent environmental xenoestrogen, was included as a reference compound due to its well-documented fungal degradation. Partial pathways of DBP metabolization by the ecophysiologically diverse asco- and basidiomycete strains tested were proposed with the help of UPLC-QTOF-MS analysis. Species specific biochemical reaction steps contributing to DBP metabolism were also observed. The involved reactions include initial cytochrome P450-dependent monohydroxylations of DBP with subsequent further oxidation of related metabolites, de-esterification via either hydrolytic cleavage or cytochrome P450-dependent oxidative O-dealkylation, transesterification, and demethylation steps - finally yielding phthalic acid as a central intermediate in all pathways. Due to the involvement of ecophysiologically and phylogenetically diverse filamentous and yeast-like fungi native to marine, freshwater, and terrestrial habitats the results of this study outline an environmentally ubiquitous pathway for the biocatalytic breakdown of plastic additives. Beyond previous research into fungal PE metabolism which emphasizes hydrolytic de-esterification as the primary catabolic step, a prominent role of cytochrome P450 monooxygenase-catalyzed reactions is established.

Does glucose affect the de-esterification of methyl ferulate by Lactobacillus buchneri?

Silage, the fermented product from anaerobic storage of forage crops with high water contents (50%-70%), is normally used as animal feed but also for the production of biofuels and value-added products. To improve the utilization of plant fibers during ensiling, previous attempts have aimed at breaking linkages between lignin and hemicellulose by use of Lactobacillus buchneri LN 4017 (ATCC PTA-6138), a feruloyl esterase (FAE)-producing strain, but results have been inconsistent. Normally, there are sufficient amounts of readily available substrates for bacterial growth in silage. We thus hypothesized that the inconsistent effect of L. buchneri LN 4017 on the digestibility of silage fibers is due to the catabolic repression of FAE activity by substrates present in silage (e.g., glucose). To test this hypothesis, we analyzed the effect of glucose on the de-esterification of methyl ferulate (MF), a model substrate used for FAE activity assays. At three glucose:MF ratios (0:1, 1:1, and 13:1), the bacteria continued hydrolyzing MF with increasing glucose:MF ratios, indicating that the de-esterification reaction was not repressed by glucose. We therefore conclude that the de-esterification activity of L. buchneri LN 4017 is not repressed by silage substrates during ensiling.

The degradative activity and adaptation potential of the litter-decomposing fungus Stropharia rugosoannulata.

The ability of the litter-decomposing basidiomycete Stropharia rugosoannulata DSM 11372 to degrade a wide range of structurally different environmental pollutants such as polycyclic aromatic hydrocarbons (PAHs: phenanthrene, anthracene, fluorene, pyrene, and fluoranthene), synthetic anthraquinone dyes containing condensed aromatic rings, environmentally relevant alkylphenol and oxyethylated alkylphenol representatives, and oil was demonstrated within the present study. 9,10-Anthraquinone, phenanthrene-9,10-quinone, and 9-fluorenone were identified as products of anthracene, phenanthrene, and fluorene degradation, respectively. Fungal degradation was accompanied by the production of the ligninolytic enzymes: laccase and Mn peroxidase, suggesting their involvement in pollutant degradation. Extracellular polysaccharide(s) (EPS) and emulsifying compound(s) were concomitantly produced. EPS composed of mannose, glucose, and galactose was isolated from the cultivation medium, and its effects on catalytic properties of purified laccase from S. rugosoannulata (the dominating ligninolytic enzyme under the applied conditions) were studied. A simultaneous decrease of KM and Vmax values observed for the enzymatic oxidation of non-phenolic (2,2-azino-bis-(3-ethylbenzthiazoline-6-sulphonic acid) diammonium salt; ABTS) and phenolic compounds (2,6-dimethoxyphenol) in presence of EPS suggest an interaction of EPS and laccase resulting in a modulation of the catalytic performance of the enzyme, which has, to the best of our knowledge, not been reported before. In line with such a modulation, the laccase-catalyzed oxidation of natural aromatic compounds (veratryl alcohol, adlerol) and environmental pollutants (the alkylphenol representative nonylphenol, the diphenylmethane derivative bisphenol A, and the PAH representative anthracene) was found to be enhanced in presence of EPS. The relevance of such effects for real environmental processes and their implications remain to be investigated.

Characterisation of electron beam irradiation-immobilised laccase for application in wastewater treatment.

Laccase from Phoma sp. UHH 5-1-03 was cross-linked to polyvinylidene fluoride membranes by electron beam irradiation. Immobilised laccase displayed a higher stability than the non-immobilised enzyme with respect to typical wastewater temperatures, and pH at a range of 5 to 9. Batch tests addressed the removal of pharmaceutically active compounds (PhACs; applied as a mixture of acetaminophen, bezafibrate, indometacin, ketoprofen, mefenamic acid, and naproxen) by both immobilised and non-immobilised laccase in municipal wastewater. High removal rates (>85%) of the most efficiently oxidised PhACs (acetaminophen and mefenamic acid) indicated a high efficiency of the immobilised laccase in wastewater. Continuous elimination of the aforementioned PhACs by the immobilised enzyme in a continuously operated diffusion basket reactor yielded a PhAC removal pattern qualitatively similar to those observed in batch tests. Clearly higher apparent Vmax values and catalytic efficiencies (in terms of both Vmax/S0.5 as well as Vmax/Km values obtained from data fitting according to the Hill and the Michaelis-Menten model, respectively) observed for acetaminophen oxidation by the immobilised compared to the non-immobilised enzyme are in support of a considerably higher functional stability of the immobilised laccase especially in wastewater. The potential influence of acetaminophen on the removal of comparatively less laccase-oxidisable water pollutants such as the antimicrobial triclosan (TCS) was investigated. TCS was increasingly removed upon increasing the initial acetaminophen concentration in immobilised as well as non-immobilised laccase reaction systems until saturation became evident. Acetaminophen was consumed and not recycled during laccase reactions, which was accompanied by the formation of various acetaminophen-TCS cross-coupling products. Nevertheless, the simultaneous presence of acetaminophen (and potentially even more pollutant removal-enhancing laccase substrates) and more recalcitrant pollutants in wastewater represents an interesting option for the efficiency enhancement of enzyme-based wastewater treatment approaches.

Evaluation of the applicability of the aquatic ascomycete Phoma sp. UHH 5-1-03 for the removal of pharmaceutically active compounds from municipal wastewaters using membrane bioreactors.

Membrane bioreactors (MBRs) augmented with terrestrial white-rot basidiomycetes have already been tested for the removal of pharmaceutically active compounds (PhACs) from wastewaters. Within the present study, an aquatic ascomycete (Phoma sp.) was initially demonstrated to efficiently remove several PhACs at their real environmental trace concentrations from nonsterile municipal wastewater on a laboratory scale. Then, a pilot MBR was bioaugmented with Phoma sp. and successively operated in two configurations (first treating full-scale MBR effluent as a posttreatment, and then treating raw municipal wastewater). Treatment of influent wastewater by the Phoma-bioaugmented pilot MBR was more efficient than influent treatment by a concomitantly operated full-scale MBR lacking Phoma sp and posttreatment of full-scale MBR permeate using the pilot MBR. A stable removal of the PhACs carbamazepine (CBZ) and diclofenac (DF) (39 and 34% on average, respectively) could be achieved throughout the pilot MBR influent treatment period of 51 days, without the need for additional nutrient supplementation (full-scale MBR: on average, 15% DF but no CBZ removed during 108 days). The long-term presence of Phoma sp. in the pilot MBR could be demonstrated using fluorescence in situ hybridization analysis, but still open questions regarding its long-term activity maintenance remain to be answered.

Exploitation of Trametes versicolor for bioremediation of endocrine disrupting chemicals in bioreactors.

Endocrine disrupting chemicals (EDCs) are environmental contaminants causing increasing concerns due to their toxicity, persistence and ubiquity. In the present study, degradative capabilities of Trametes versicolor, Pleurotus ostreatus and Phanerochaete chrysosporium to act on five EDCs, which represent different classes of chemicals (phenols, parabens and phthalate) and were first applied as single compounds, were assessed. T. versicolor was selected due to its efficiency against target EDCs and its potentialities were exploited against a mixture of EDCs in a cost-effective bioremediation process. A fed-batch approach as well as a starvation strategy were applied in order to reduce the need for input of 'fresh' biomass, and avoid the requirement for external nutrients. The fungus was successfully operated in two different bioreactors over one week. Semi-batch cultures were carried out by daily adding a mixture of EDCs to the bioreactors in a total of five consecutive degradation cycles. T. versicolor was able to efficiently remove all compounds during each cycle converting up to 21 mg L-1 day-1 of the tested EDCs. The maintained ability of T. versicolor to remove EDCs without any additional nutrients represents the main outcome of this study, which enables to forecast its application in a water treatment process.

Degradation of polystyrene and selected analogues by biological Fenton chemistry approaches: Opportunities and limitations.

Conventional synthetic polymers typically are highly resistant to microbial degradation, which is beneficial for their intended purpose but highly detrimental when such polymers get lost into the environment. Polystyrene is one of the most widespread of such polymers, but knowledge about its biological degradability is scarce. In this study, we investigated the ability of the polymer-degrading brown-rot fungus Gloeophyllum trabeum to attack polystyrene via Fenton chemistry driven by the redox-cycling of quinones. Indications of superficial oxidation were observed, but the overall effects on the polymer were weak. To assess factors constraining biodegradation of polystyrene, the small water-soluble model compounds ethylbenzene and isopropylbenzene (cumene) were also subjected to biodegradation by G. trabeum. Likewise, ethylbenzene sulfonate, cumene sulfonate and the dimer 1,3-diphenylbutane sulfonate were used as model compounds for comparison with polystyrene sulfonate, which G. trabeum can substantially depolymerise. All model compounds but cumene were degraded by G. trabeum and yielded a large variety of oxidised metabolites, suggesting that both the very poor bioavailability of polystyrene and its inert basic structure play important roles constraining biodegradability via biologically driven Fenton chemistry.

Laccase- and electrochemically mediated conversion of triclosan: Metabolite formation and influence on antibacterial activity.

Metabolite formation from radical-based oxidation of the environmental pollutant triclosan (TCS) was compared using an ascomycete (Phoma sp. UHH 5-1-03) and a basidiomycete (Trametes versicolor) laccase, laccase-redox mediator systems, and electrochemical oxidation (EC). Laccase oxidation predominantly yielded TCS di- and trimers, but notably also caused TCS ether bond cleavage. The latter was more prominent during EC-catalysed TCS oxidation, which generally resulted in a broader and more divergent product spectrum. By contrast, only quantitative but not qualitative differences in TCS metabolite formation were observed for the two laccases. Application of the presumable natural laccase redox mediator syringaldehyde (SYD) shifted the TCS-transforming reactions of laccase systems from oligomerization more towards ether bond cleavage. However, the observed rapid removal of SYD from reaction systems caused by predominant adduct formation from SYD and TCS, and concomitant conversion of SYD into 2,6-dimethoxy-1,4-benzoquinone (DMBQ) clearly demonstrates that SYD does not function as a "true" laccase redox mediator in the sense of being recycled during TCS oxidation. Laccase treatment of TCS without SYD decreased the anti-bacterial TCS activity more than treatment employing SYD in addition, indicating that SYD and/or its transformation products contribute to bacterial toxicity. DMBQ was found to be about 80% more active in a bacterial growth inhibition test than its parent compound SYD in terms of IC20 values. These observations establish DMBQ as a potential cause of toxicity effects of SYD-laccase systems. They further illustrate that a natural origin of a redox mediator does not automatically qualify its use as environmentally benign or non-hazardous.

Widespread ability of fungi to drive quinone redox cycling for biodegradation.

Wood-rotting fungi possess remarkably diverse extracellular oxidation mechanisms, including enzymes, such as laccase and peroxidases, and Fenton chemistry. The ability to biologically drive Fenton chemistry by the redox cycling of quinones has previously been reported to be present in both ecologically diverging main groups of wood-rotting basidiomycetes. Therefore, we investigated whether it is even more widespread among fungal organisms. Screening of a diverse selection of a total of 18 ascomycetes and basidiomycetes for reduction of the model compound 2,6-dimethoxy benzoquinone revealed that all investigated strains were capable of reducing it to its corresponding hydroquinone. In a second step, depolymerization of the synthetic polymer polystyrene sulfonate was used as a proxy for quinone-dependent Fenton-based biodegradation capabilities. A diverse subset of the strains, including environmentally ubiquitous molds, white-rot fungi, as well as peatland and aquatic isolates, caused substantial depolymerization indicative for the effective employment of quinone redox cycling as biodegradation tool. Our results may also open up new paths to utilize diverse fungi for the bioremediation of recalcitrant organic pollutants.

Biochemical and physicochemical processes contributing to the removal of endocrine-disrupting chemicals and pharmaceuticals by the aquatic ascomycete Phoma sp. UHH 5-1-03.

The environmentally widespread micropollutants bisphenol A (BPA), carbamazepine (CBZ), 17α-ethinylestradiol (EE2), diclofenac (DF), sulfamethoxazole (SMX), technical nonylphenol (t-NP) and triclosan (TCS) were used to assess the potential of the laccase-producing freshwater ascomycete Phoma sp. strain UHH 5-1-03 for micropollutant removal and to provide quantitative insights into the mechanisms involved. Biotransformation rates observed with whole fungal cells followed the rank order EE2 ≫ BPA > TCS > t-NP > DF > SMX > CBZ. Biosorption onto fungal mycelia was prominent for BPA, EE2, TCS and t-NP and insignificant for CBZ, DF and SMX. Enzymatic removal rates investigated with cell-free, laccase-containing culture supernatants of Phoma sp. followed the rank order EE2 > BPA > DF > t-NP > TCS and were insignificant for SMX and CBZ. Mass spectrometry-assisted investigations addressing metabolite formation from unlabelled and (13)C6-labelled DF and SMX yielded DF metabolites indicating hydroxylation, cyclisation and decarboxylation reactions, as well as oxidative coupling typical for laccase reactions. For SMX, several products characterised by lower molecular masses than the parent compound were found, and indications for deamination and formamide formation were obtained. Summarising, the obtained results suggest that the extracellular laccase of Phoma sp. largely contributes to fungal biotransformation of EE2, BPA, DF, TCS and t-NP, together with cell-associated enzymes such as, e.g. cytochrome P450 monooxygenases suggested by the appearance of hydroxylated metabolites from DF. Laccase does not seem to play any role in the metabolisation of SMX and CBZ, where yet to be identified cell-associated enzymes have to be considered instead.

Prospects for microbiological solutions to environmental pollution with plastics.

Synthetic polymers, commonly named plastics, are among the most widespread anthropogenic pollutants of marine, limnic and terrestrial ecosystems. Disruptive effects of plastics are known to threaten wildlife and exert effects on natural food webs, but signs for and knowledge on plastic biodegradation are limited. Microorganisms are the most promising candidates for an eventual bioremediation of environmental plastics. Laboratory studies have reported various effects of microorganisms on many types of polymers, usually by enzymatic hydrolysis or oxidation. However, most common plastics have proved to be highly recalcitrant even under conditions known to favour microbial degradation. Knowledge on environmental degradation is yet scarcer. With this review, we provide a comprehensive overview of the current knowledge on microbiological degradation of several of the most common plastic types. Furthermore, we illustrate the analytical challenges concerning the evaluation of plastic biodegradation as well as constraints likely standing against the evolution of effective biodegradation pathways.