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- Fourier transform infrared - attenuated total reflexion (FTIR-ATR) spectroscopy (2)
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Eingeladener Vortrag
- nein (7)
The main wood degraders in aerobic terrestrial ecosystems belong to the white- and brown-rot fungi, where their biomass can be created on wood decay only. However, total sulfur (S) concentration in wood is very low and only little is known about the different sulfur compounds in wood today. Sulfur-starved brown-rot fungi Gloeophyllum trabeum and Oligoporus placenta were incubated on sterilized pine wood blocks whereas Lentinus cyathiformis and the white-rot fungi Trametes versicolor were incubated on sterilized beech wood blocks. After 19 weeks of incubation, the S oxidation status was analyzed in wood, in degraded wood, and in biomass of wood-degrading fungi by synchrotron based S K-edge XANES, and total S and sulfate were quantified. Total sulfur and sulfate content in pine wood blocks were approximately 50 and 1 µg g-1, respectively, while in beech wood approximately 100 and 20 µg g-1 were found, respectively. Sulfur in beech was dominated by sulfate-esters. In contrast, pine wood also contained larger amounts of reduced S. Three out of four selected fungi caused a reduction of the S oxidation state in wood from oxidized S (sulfate-ester, sulfate) to intermediate S (sulfonate, sulfoxide) or reduced S (thiols, e.g., proteins, peptides, enzyme cofactors). Only O. placenta shifted thiol to sulfonate. Growth experiments of these fungi on selective minimal media showed that in particular cysteine (thiol), sulfonates, and sulfate enhanced total mycelium growth. Consequently, wood-degrading fungi were able to utilize a large variety of different wood S sources for growth but preferentially transformed in vivo sulfate-esters and thiol into biomass structures.
The microbial community structure was investigated together with the path of methane production in Italian rice field soil incubated at moderate (35 °C) and high (45 °C) temperature using terminal restriction fragment length polymorphism and stable isotope fractionation. The structure of both the archaeal and bacterial communities differed at 35 °C compared with 45 °C, and acetoclastic and hydrogenotrophic methanogenesis dominated, respectively. Changing the incubation of the 45 °C soil to different temperatures (25, 30, 35, 40, 45, 50 °C) resulted in a dynamic change of both microbial community structure and stable isotope fractionation. In all treatments, acetate first accumulated and then decreased. Propionate was also transiently produced and consumed. It is noteworthy that acetate was also consumed at thermophilic conditions, although archaeal community composition and stable isotope fractionation indicated that acetoclastic methanogenesis did not operate. Instead, acetate must have been consumed by syntrophic acetate oxidizers. The transient accumulation and subsequent consumption of acetate at thermophilic conditions was specifically paralleled by terminal restriction fragments characteristic for clostridial cluster I, whereas those of clostridial clusters I and III, Acidaminococcaceae and Heliobacteraceae, paralleled the thermophilic turnover of both acetate and propionate.
Das Interesse für erneuerbare Energieträger ist in den letzten Jahren stark angestiegen.
Im Bereich Biomasse als erneuerbarer Energieträger wird besonders Holz ein großes
Wachstum auf dem Energiesektor prognostiziert (NITSCH 2007). Die Speicherung dieser
Energie erfolgt meist durch Holzhackschnitzelhalden in der Umwelt. Um ein tieferes Verständnis
der in der Halde ablaufenden mikrobiologischen Prozesse erhalten zu können,
wurden in einer neu aufgebauten Kiefernholzhackschnitzelhalde mit den Ausmaßen
15 m x 20 m x 6 m folgende Messungen durchgeführt: a.) Messung der Gaskonzentration
von Sauerstoff, Kohlendioxid als auch der Temperaturentwicklung innerhalb der Halde; b.)
Messung der Veränderung der Holzzusammensetzung innerhalb der Halde über die Zeit;
c.) Charakterisierung der Veränderung der Zusammensetzung der bakteriellen als auch
der pilzlichen Lebensgemeinschaften über die Zeit; d.) Charakterisierung von dominanten
Vertretern der bakteriellen als auch der pilzlichen Lebensgemeinschaften. Die Ergebnisse
zeigen, dass sich die Funktion und die Zusammensetzung der Lebensgemeinschaften
über die Dauer der Holzhackschnitzellagerung ändern, und dass diese Änderungen nur
zum Teil mit den Prozessen bei Kompostierungsanlagen vergleichbar sind.
Fast growing softwood species such as pine are preferred for biomass-based heat as well as electricity production and stored in large quantities. A newly established outdoor pile of freshly cut pine-wood chips was monitored to analyze exothermic processes. Inside the pile, a mean temperature increase of up to 44 °C was measured after six days of piling which was paralleled by a decrease of O2-concentration and an increase of CO2-concentration. Thereafter four additional CO2 maxima were observed, while O2-concentration remained at ambient concentration. The fungal community structure remained almost unchanged after four weeks, while the bacterial community structure was characterized by continuous shifts over time. The rapid heating in the early stage of storage corresponded to high relative abundance of microbial strains belonging to the genera Pseudomonas, Luteibacter and Caulobacter, ascomycetous genera Sphaeropsis and Cadophora and basidiomycetous order Polyporales and genus Sistotremastrum. The late stage was composed by a broader diversity of microorganisms, and heating processes inside the wood pile were attributed mainly to physicochemical processes. Taken together, these observations suggest that the early bacterial and fungal communities are key players in exothermic processes and were replaced by a broader diversity of highly adapted microorganisms.
Exothermic processes in outdoor pine wood chip piles are linked to microbial community shifts
(2009)
The microbial community in anoxic rice field soil produces CH4 over a wide temperature range up to 55°C. However, at temperatures higher than about 40°C, the methanogenic path changes from CH4 production by hydrogenotrophic plus acetoclastic methanogenesis to exclusively hydrogenotrophic methanogenesis and simultaneously, the methanogenic community consisting of Methanosarcinaceae, Methanoseataceae, Methanomicrobiales, Methanobacteriales and Rice Cluster I (RC-1) changes to almost complete dominance of RC-1. We studied changes in structure and function of the methanogenic community with temperature to see whether microbial members of the community were lost or their function impaired by exposure to high temperature. We characterized the function of the community by the path of CH4 production measuring δ13C in CH4 and CO2 and calculating the apparent fractionation factor (αapp) and the structure of the community by analysis of the terminal restriction fragment length polymorphism (T-RFLP) of the microbial 16S rRNA genes. Shift of the temperature from 45°C to 35°C resulted in a corresponding shift of function and structure, especially when some 35°C soil was added to the 45°C soil. The bacterial community (T-RFLP patterns), which was much more diverse than the archaeal community, changed in a similar manner upon temperature shift. Incubation of a mixture of 35°C and 50°C pre-incubated methanogenic rice field soil at different temperatures resulted in functionally and structurally well-defined communities. Although function changed from a mixture of acetoclastic and hydrogenotrophic methanogenesis to exclusively hydrogenotrophic methanogenesis over a rather narrow temperature range of 42-46°C, each of these temperatures also resulted in only one characteristic function and structure. Our study showed that temperature conditions defined structure and function of the methanogenic microbial community.