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Chemical degradation of lignin has attracted increasing interest due to its potential for producing chemicals from renewable resources. Herein, we present a new transition metal free degradation procedure utilizing DDQ-oxidation and boryl radical mediated degradation, followed by reconnection of a monomer intermediate to a new dimer in a domino process. Our results include the selective degradation of oxidized β-O-4 model compounds by a boryl radical initiated with a catalytic amount of 4-(4-pyridinyl)benzonitrile and bispinacolborane B2(pin)2 as well as its application to organosolv lignin. This sequential procedure expands the toolbox for lignin degradation from simple depolymerization to high-value products by incorporating bond forming transformations within the process, and also provides a new transition-metal free method for the construction of 1,6-diketone fragments.

The impressive ability of the fungus Xylaria longipes to transform the highly persistent fluoroquinolone ciprofloxacin into microbiologically less active degradation products was demonstrated. Fluoroquinolones are used extensively in both human and veterinary medicine. Poor metabolization and high chemical stability of these synthetic antibiotics led to their presence in several environmental compartments. This undesirable behavior may promote the spread of resistance mechanisms due to concomitant exposure to bacteria. Therefore, the biotransformation of ciprofloxacin, one of the most prescribed fluoroquinolones in human medicine, by the ascomycetous soft rot fungus X. longipes was investigated in detail. Submerged cultivation of the fungus allowed for high-yield formation of four biotransformation products. These compounds were subsequently purified by preparative high-performance liquid chromatography. Applying accurate mass spectrometry and nuclear magnetic resonance spectroscopy, desethylene-ciprofloxacin, desethylene-N-acetyl-ciprofloxacin, N-formyl-ciprofloxacin and N-acetyl-ciprofloxacin were unambiguously identified. N-acetylation and N-formylation of the drug led to a 75-88% reduction of the initial antibacterial activity, whereas a breakdown of the piperazine substituent resulted in almost inactive products. These findings suggest an important role in the inactivation and degradation of this and other synthetic compounds in the environment.

Ergosterol, a precursor of vitamin D(2), is present in the cell membrane of all fungi. It can be transformed into vitamin D(2) by UV-B exposure. In this study, a basidiomycete, Pleurotus sapidus, cultivated in liquid malt extract medium was exposed to UV-B light. In addition, autoclaved, abiotic mycelium was put through UV-B exposure for the first time. The effects of different UV-B exposure times, surface areas and temperatures on vitamin D(2) formation were analyzed. The conversion of ergosterol to vitamin D(2) at ambient temperature almost reached completion within 10 min resulting in vitamin D(2) concentrations of 365 µg (g dry matter)(−1). Prolonged exposure of the biotic mycelium for up to 60 min resulted in a reduced vitamin D(2) concentration with stagnation at about 280 µg (g dry matter)(−1). Exposure of the abiotic mycelium showed a slower increase but also leveled off at the same concentration. Furthermore, it could be shown that vitamin D(2) formation depends on the temperature and the exposed surface area. The vitamin D(2) concentration augmented after increasing the exposed surface from 65.0 to 298.6 cm(2). The ergosterol content of P. sapidus was analyzed in a way similar to vitamin D(2) and resulted in 3.75 ± 0.06 mg (g dry matter)(−1) ergosterol. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (10.1007/s13197-018-3290-z) contains supplementary material, which is available to authorized users.

Twenty-nine basidiomycetes were screened in surface and liquid cultures for their capability to biotransform the chloroacetamide herbicide Dimethenamid-P (DMTA-P). The basidiomycete Irpex consors converted 70% of the herbicide (0.5 g L-1 DMTA-P) in liquid cultures within 6 days, applying a minimal medium under non-ligninolytic conditions. Nine transformation products of DMTA-P were identified by liquid chromatography-mass spectrometry analysis of the culture supernatants. The four main metabolites were isolated and subjected to GC-MS analysis and NMR spectroscopy. The analyses revealed that the thiophene ring was oxidized at three different positions. Metabolite M1 was identified as the S-oxide, which was isolable and relatively stable at room temperature. In metabolite M2, one methyl substituent of the thiophene ring was hydroxylated. The two metabolites M3A and M3B were diastereomers, but fully separated by HPLC. Here, oxidation of the aromatic CH carbon resulted in prototropic rearrangement to an αβ-unsaturated thiolactone. None of the three major metabolites of DMTA-P has been described before.

Dimethylsulfoniopropionate (DMSP), a sulfur containing osmolyte and antioxidant, is suggested to take over the role of nitrogen-containing osmolytes under nitrate-depleted conditions. But other factors like time of day or limitation by nutrients can influence the cellular DMSP content as well. Especially in diatoms the complex dynamics of this central metabolite are still poorly understood. Therefore, we monitored the DMSP content in batch cultures of the diatom Skeletonema marinoi over the entire culture development, using a detailed sampling protocol on a diurnal basis to investigate the influence of the day/night cycle and limitation by nitrogen and other nutrients on cellular DMSP. Cultures were inoculated with initial high nitrate (N +) or low nitrate (N −) concentrations to evaluate the effects of nitrogen availability. The DMSP content per cell varied significantly with a 4-fold increase over the entire experiment. For N + conditions a pronounced diurnal pattern was found with increasing DMSP contents per cell during the light and decreasing DMSP contents during the dark period. However, when DMSP was normalized to cell volume, the highest concentrations occurred near the beginning of the light period. For N − cultures no such pronounced pattern was found. DMSP values of N − cultures increased within a few hours after the medium became nitrate depleted, while no such connection between nitrogen-concentration and DMSP could be observed in the N + cultures, where possibly an overflow mechanism or limitation of other nutrients such as Si might affect DMSP concentrations. Based on this data set we can conclude that DMSP formation in S. marinoi is under a pronounced diurnal control and depends in a rather complex manner on other factors such as growth limitation by nutrients.

Dimethylsulfoniopropionate (DMSP) is a metabolite involved in central processes of phytoplankton physiology and ecology. Due to its high abundance, this molecule plays also a major role in global sulfur cycling. DMSP concentrations are usually indirectly determined via the base mediated release of dimethylsulfide (DMS) using gas chromatography (GC). However, because other potential precursors of DMS have been reported from macroalgae and phytoplankton, there is a substantial risk for an overestimation using an indirect method. We improve and validate a protocol for the derivatization and determination of DMSP in phytoplankton cultures. The improved method includes derivatization with 1-pyrenyldiazomethane (PDAM) and analysis via ultra performance liquid chromatography coupled with a mass selective detector (UPLC/MS). The protocol allows simultaneous qualitative and quantitative analysis of DMSP, other putative DMS precursors and osmolytes like glycine betaine (GBT). Detection limits are around 100 fmol on column allowing the quantification of DMSP from plankton field samples as well as from phytoplankton cultures. The DMSP content of several phytoplankton cultures was determined using the method involving derivatization of DMSP as well as an indirect headspace method determining DMS. For several algae strains, significant higher concentrations were obtained with the indirect determination. These results underscore the importance of other potential DMS precursors in phytoplankton samples that are not considered when using indirect methods for DMSP determination.

A simple, derivatization free method for the direct determination of dimethylsulfoniopropionate (DMSP) using hydrophilic interaction liquid chromatography (HILIC)/mass spectrometry is introduced. DMSP is a zwitterionic osmolyte which is produced from marine plankton, macro algae and higher plants. Due to its central role in climate relevant geochemical processes as well as in plant physiology and chemical ecology there is a great interest in methods for its quantification. Since DMSP is labile and difficult to extract currently most protocols for quantification are based on indirect methods. Here we show that ultra performance liquid chromatography/mass spectrometry using a HILIC stationary phase is suitable for the direct quantification of DMSP from aqueous samples and microalgal extracts. The protocol requires minimal sample preparation and phytoplankton samples can be investigated after filtration of small volumes. The limit of detection is 20 nM and the calibration curve is linear in the range of 60 nM to 50 μM. The use of [2H6]-DMSP as internal standard allows prolonged sample storage since it is transformed with the same kinetics as natural DMSP. This makes the method suitable for both laboratory and field studies.

4-Vinylsyringol, also referred to as canolol, is a highly active antioxidant and potent lipidperoxyl radical scavenger found in rapeseed. The canolol content of rapeseed can be increased through the decarboxylation of sinapic acid via roasting treatments. Different roasting conditions were tested and compared and an optimum for the canolol formation was found at 160 °C. The canolol content of the rapeseed samples with optimal roasting increased by a factor of 120 in relation to the unroasted sample. The rapeseed was ground, extracted and analysed by normal-phase HPLC/UV. The structure of canolol was confirmed by NMR and MS techniques. Several rapeseed oils were purchased in German food stores and analysed. No differences in canolol content were observed in both cold-pressed and rape kernel oil samples tested. Dehulled rapeseed samples demonstrated no significant difference in canolol content when compared to unpeeled rapeseed samples.

Fluoroquinolones are considered as critically important antibiotics. However, they are used in appreciable quantities in veterinary medicine. Liquid manure and feces can contain substantial amounts of unmetabolized antibiotics and, thus, antibiotics can enter the environment if manure is used for soil fertilization. In this study, the microbial biotransformation of the synthetic veterinary fluoroquinolone danofloxacin by the ascomycete Xylaria longipes was investigated. Fungal submerged cultures led to a regioselective and almost quantitative formation of a single metabolite within 3 days. The metabolite was unequivocally identified as danofloxacin N-oxide by high-resolution mass spectrometry and one- and two-dimensional nuclear magnetic resonance spectroscopic techniques. An oxidation of the terminal nitrogen of the substituted piperazine moiety of the substance led to a remarkable reduction of 80% of the initial antibacterial activity. Thus, fungal enzymes involved in the biotransformation process might possess the potential to reduce the entrance of antibiotics via biotransformation of these compounds.

The sulfur metabolite dimethylsulfoniopropionate (DMSP) is the most important precursor of the climate relevant metabolite dimethylsulfide (DMS). It has thus gained interest in the context of climate change and several studies investigated the influence of elevated temperature and/or CO2 on DMSP in complex plankton communities. However, only little information about changes in response to these factors in single species is available. Therefore, we analyzed DMSP in different phytoplankton cultures (Thalassiosira pseudonana, Phaeodactylum tricornutum, Emiliania huxleyi) under the influence of increased temperature by 6 °C and elevated CO2 to 790 ppmv. In addition, we addressed glycine betaine (GBT) that fulfills a similar function as osmolyte like DMSP. In all cultures GBT concentrations increased at higher temperature and decreased at elevated CO2. In contrast, diatoms and prymnesiophytes revealed opposite trends for DMSP. In diatoms increased CO2 and temperature led to decreased DMSP concentrations, while rather elevated levels of this metabolite under the influence of these parameters were observed for E. huxleyi.

No change here: Analysis with doubly labeled [(13)C(2)D(6)]DMSP and LC/MS revealed that dissolved DMSP is taken up and stored intracellularly by diverse phytoplankton species without transformation. This is even true for species that produce no quantifiable amounts of DMSP themselves.