Biomass fractionation

The objective of this master's thesis was to develop a process to increase the value of residual fungal biomass as an animal feed. The increase in value is achieved by enriching the protein content in the biomass and potentially isolating other valuable fractions for productisation. In the literature part of this thesis the composition of fungal biomass and fungal cell wall and the factors affecting them during cultivation are presented. The possible processing options are also presented and evaluated. The soy protein and single cell protein product manufacturing processes are used as examples due to the lack of fungal biomass fractionation processes found in published literature. The second part of this thesis was performed by making laboratory experiments on the developed process, which consisted of acid hydrolysis with subsequent ethanol extraction. Chitin was precipitated from the acid hydrolysate filtrate. The experiments were conducted with three different hydrolysis temperatures and three different acid concentrations. The optimal hydrolysis conditions were 60 °C with 10 %-vol acid concentration. Optimal conditions in hydrolysis resulted in 30 % increase in protein content in the final biomass. The conceptual process was modelled to scale of 10 000 t/a biomass feed. The mass and energy balances were based on the laboratory experiments. Economic calculations were performed to determine the maximal capital expense while achieving 10 % internal rate of return for the investment. For the basic case the capital expense threshold was 25.8 M€. Four optional cases and parameter sensitivity analysis were performed to determine the effects of changes in the process. The chitin sales had the greatest impact of the individual parameters.

Trading nitrogen for carbon: Nitrogen and carbon translocation in a plant/fungal (Metarhizium spp.) symbiosis

While nitrogen is critical for all plants, they are unable to utilize organically bound nitrogen in soils. Therefore, the majority of plants obtain useable nitrogen through nitrogen fixing bacteria and the microbial decomposition of organic matter. In the majority of cases, symbiotic microorganisms directly furnish plant roots with inorganic forms of nitrogen. More than 80% of all land plants form intimate symbiotic relationships with root colonizing fungi. These common plant/fungal interactions have been defined largely through nutrient exchange, where the plant receives limiting soil nutrients, such as nitrogen, in exchange for plant derived carbon. Fungal endophytes are common plant colonizers. A number of these fungal species have a dual life cycle, meaning that they are not solely plant colonizers, but also saprophytes, insect pathogens, or plant pathogens. By using 15N labeled, Metarhizium infected, wax moth larvae (Galleria mellonella) in soil microcosms, I demonstrated that the common endophytic, insect pathogenic fungi Metarhizium spp. are able to infect living soil borne insects, and subsequently colonize plant roots and furnish ts plant host with useable, insect-derived nitrogen. In addition, I showed that another ecologically important, endophytic, insect pathogenic fungi, Beauveria bassiana, is able to transfer insect-derived nitrogen to its plant host. I demonstrated that these relationships between various plant species and endophytic, insect pathogenic fungi help to improve overall plant health. By using 13C-labeled CO2, added to airtight plant growth chambers, coupled with nuclear magnetic resosnance spectroscopy, I was able to track the movement of carbon from the atmosphere, into the plant, and finally into the root colonized fungal biomass. This indicates that Metarhizium exists in a symbiotic partnership with plants, where insect nitrogen is exchanged for plant carbon. Overall these studies provide the first evidence of nutrient exchange between an insect pathogenic fungus and plants, a relationship that has potentially useful implications on plant primary production, soil health, and overall ecosystem stability.

Effect of culture conditions on the biomass determination by ergosterol of Lentinus crinitus and Psilocybe castanella

Estimating fungal growth is important in processes of soil bioremediation. It has been demonstrated that ergosterol is a good indicator of fungal biomass in solid substrata. In the present study were evaluated the effects upon the ergosterol rate of Lentinus crinitus Berk. and Psilocybe castanella Peck through the culture conditions of these fungi, which are evaluated for the bioremediation of soils contaminated by organochlorates. A good correlation between fungal biomass and ergosterol was observed for both species. The culture conditions did not influence the ergosterol rate of L. crinitus. Yet the ergosterol rate of P. castanella was influenced from 35 days of culture and when grown in the presence of 15.00 g hexachlorobenzene l(-1) of culture medium. So it is possible to estimate growth of both species using ergosterol as indicator in processes of soil bioremediation since the influences observed in the ergosterol rate of P. castanella are considered.

The breakdown of plant cell biomass by fungi

Three species of fungi Sporotrichum thermophile, Botrytis cinerea and Trichoderma viride were assessed for their ability to utilize a variety of plant cell substrates (methanol extracted), Catharanthus roseus, Daucus carota, re-autoclaved C. roseus, re-autoclaved D. carota) which preliminary studies had indicated contained the necessary nutrients for fungal growth. Incubated in a suitable manner all three fungal species were able to grow on C. roseus and D. carota plant cell biomass in addition to material which had undergone methanol extraction or a re-autoclaving process to remove soluble components. Fungal biomass yields were markedly influenced by substrate, with each fungal species demonstrating a preference for particular plant cell material. Incubation conditions i.e. static or shaken and temperature also proved important. Release of glucose (i.e. values higher than Day 0) promoted by fungal breakdown of plant cell biomass was only noted with methanol extracted, re-autoclaved C. roseus and re-autoclaved D. carota material. A re-autoclaved substrate was also generally associated with high fungal C1, Cx, B-glucosidase and endo-polygalacturonase activity. In addition for each enzyme highest values were usually obtained from a particular fungal species. Buffering cultures at pH 3 or 5 further influenced enzyme activity, however in a majority of cases when flasks were unbuffered and the pH rose naturally to alkaline values higher enzyme activity was recorded. Likewise Tween 80 addition had only a limited beneficial effect. Finally filtrates containing glucose produced both from the re-autoclaving process and through fungal activity on plant cell biomass were utilized for Fusarium oxysporum, Saccharomyces cerevisiae and C. roseus plant cell culture. Although reasonable fungal biomass was obtained the use of such filtrates proved unsuitable for plant cell growth.

Growth of subtropical ECM fungi with different nitrogen sources using a new floating culture technique

Eight species of ectomycorrhizal (ECM) fungi in the genera Amanita. Gymnoboletus, Lactarius, and Russula were isolated from subtropical plant communities in eastem Australia. Two species were isolated from each of rainforest, Nothofagus forest, Eucalyptus forest, and Eucalyptus dominated wallum (heath) forest. These communities differ strongly in their soluble soil nitrogen (N) composition. The ability of the fungi to use inorganic (nitrate, ammonium) and organic (amide, peptide, protein) nitrogen sources was determined. As the fungi did not grow in liquid culture, a 'floating culture' technique was devised that allows hyphal growth on a screen floating on liquid medium. With some exceptions, fungal biomass production in floating culture closely reflected fungal growth on solid media assessed by total colony glucosamine content. Most isolates grown in floating culture had similar glucosamine concentrations on all N sources, with isolate specific concentrations ranging from 6 to 12 mug glucosamine g(-1) DW. However, Russula spp. had up to 1.7-fold higher glucosamine concentrations when growing with glutamine or ammonium compared to nitrate, glutathione or protein. Floating cultures supplied with 0.5, 1.5. 4.5, or 10 mm N mostly produced greatest biomass with 4.5 mM N. In vitro nitrate reductase activity (NRA) ranged from very low (0.03 mumol NO2- g(-1) fw h(-1)) in Russula sp. (wallum) to high (2.16 mumol NO2- g(-1) fw h(-1)) in Gymnoboletus sp. (rainforest) and mirrored the fungi's ability to use nitrate as a N source. All Russula spp. (wallum, Nothofagus and Eucalyptus forests), Lactarills sp, (rainforest) and.4manita sp. (wallum) utilized ammonium and glutamine but had little ability to use other N sources. In contrast,Amanita species (Nothofagus and Eucalyptus forests) grew on all N sources but produced most biomass with ammonium and glutamine. Only Gymnoboletus sp. (rainforest) showed similar growth with nitrate and ammonium as N sources. Fungal N source use was not associated with taxonomic groups, but is discussed in the context of soil N sources in the different habitats.

Fungi, bacteria and soil pH: the oxalate-carbonate pathway as a model for metabolic interaction

The oxalatecarbonate pathway involves the oxidation of calcium oxalate to low-magnesium calcite and represents a potential long-term terrestrial sink for atmospheric CO2. In this pathway, bacterial oxalate degradation is associated with a strong local alkalinization and subsequent carbonate precipitation. In order to test whether this process occurs in soil, the role of bacteria, fungi and calcium oxalate amendments was studied using microcosms. In a model system with sterile soil amended with laboratory cultures of oxalotrophic bacteria and fungi, the addition of calcium oxalate induced a distinct pH shift and led to the final precipitation of calcite. However, the simultaneous presence of bacteria and fungi was essential to drive this pH shift. Growth of both oxalotrophic bacteria and fungi was confirmed by qPCR on the frc (oxalotrophic bacteria) and 16S rRNA genes, and the quantification of ergosterol (active fungal biomass) respectively. The experiment was replicated in microcosms with non-sterilized soil. In this case, the bacterial and fungal contribution to oxalate degradation was evaluated by treatments with specific biocides (cycloheximide and bronopol). Results showed that the autochthonous microflora oxidized calcium oxalate and induced a significant soil alkalinization. Moreover, data confirmed the results from the model soil showing that bacteria are essentially responsible for the pH shift, but require the presence of fungi for their oxalotrophic activity. The combined results highlight that the interaction between bacteria and fungi is essential to drive metabolic processes in complex environments such as soil.

Production of a bioherbicide agent in liquid and solid medium and in a biphasic cultivation system

The use of fungi in weeds control programs depends upon the conidia production in large scale. Therefore, this study aimed to evaluate liquid and solid culture media and the cultivation by biphasic system for the conidia production of Bipolaris euphorbiae Muchovej & Carvalho a specific pathogen of Euphorbia heterophylla. The liquid media were obtained from agro-industrial waste or by-products, and the solid media were prepared with mixtures of grains and grain derivatives. The liquid medium made with sugar cane molasses stood out from the others because it provided great sporulation (23 x 10(4) conidia mL-1 of medium), conidial viability (99.7%), and formation of mycelial fungal biomass (1.26 g 100 mL-1 of medium). On solid media conidial production was markedly higher than in liquid media, especially the medium composed by a blend of sorghum grain (40%) and soybean hulls (60%) where the fungus produced 2.3 x 10(7) conidia g-1 of medium. The cultivation of B. euphorbiae in biphasic system not promoted a significant increase in the production of conidia. The solid media were more effective for the mass production of fungus and mixtures of grains and derivatives were effective for increasing conidia production.

Wirkung von Ernterückständen transgener Pflanzen auf die mikrobielle C- und N-Transformation in landwirtschaftlich genutzten Böden am Beispiel von Bt-Mais

In der vorliegenden Arbeit ging es um die Erarbeitung, Anwendung und Beurteilung von quantitativen Analysenverfahren / Methoden für ein Monitoring von durch Bt-Mais verursachbaren Umwelteffekten im Boden. Die Ausgangsthese besagte, dass sich transgene Maisstreu beim mikrobiellen Abbau anders verhält als konventionelle. Bezugnehmend auf die These wurden zwei Freilandversuche (Freilandmikrokosmenmethode nach Raubuch 1997 über 2 Jahre, Quantifizierung des Maisstreuabbaus mit Hilfe kleiner Bodensäulen über 1 Jahr) und zwei Inkubationsversuche im Labor (INK bei drei verschiedenen Temperaturen über 49 Tage und INK mit verschiedenen landwirtschaftlich genutzten Böden über 49 Tage mit jeweils kontinuierlicher Respirationsratenermittlung nach Isermeyer 1952) sowie Inhaltsstoffbestimmungen der Maisstreu durchgeführt. Für alle Untersuchungen wurde Streu der vier Maissorten Novelis (transgen, Monsanto 810), Nobilis (Isolinie von Novelis), Valmont (transgen, Bt 176, Fa. Syngenta) und Prelude (Isolinie von Valmont) eingesetzt. Nach Beendigung der Laborversuche sowie des Freilandversuches nach der Freilandmikrokosmenmethode wurden mikrobielle Messgrößen wie Adenylategehalt, Ergosterolgehalt, Cmik- und Nmik-Gehalt am Boden-Streu-Gemisch bestimmt. Der Einsatz der Isotopentechnik (Bestimmung von 13C/12C an gemahlenem Boden-Streu-Gemisch bzw. gefriergetrocknetem K2SO4 als Extrakt aus dem Boden-Streu-Gemisch) ermöglichte eine genaue Quantifizierung der abgebauten Maisstreu und brachte dadurch Aufschluss über das Abbauverhalten verschiedener Maissorten. Bezüglich der Ermittlung der mikrobiellen Messgrößen ergab sich für die transgene Sorte Novelis* stets eine durchschnittlich geringere pilzliche Biomasse. Langfristig ergaben sich bei der Kohlenstoff- und Stickstoffdynamik keine Trends hinsichtlich transgener bzw. konventioneller Maisstreu. Sowohl im Freilandversuch nach der Mikrokosmenmethode als auch in den Inkubationsversuchen trat das Phänomen der kurzzeitigen Respirationsratenerhöhung der Mikroorganismen nach Zugabe der transgenen Maissorten auf, welches nicht bei Zugabe der konventionellen Maisstreu auszumachen war. ______________________________

Die mikrobielle Besiedlung von Wurzeloberfläche und Rhizosphäre in ihrer Bedeutung für Stoffumsätze in Böden

Im Vordergrund der Arbeit stand die Erfassung der mikrobiellen Biomasse bzw. Residualmasse an der Wurzeloberfläche, im Rhizosphärenboden und im umgebenden Boden. Durch den Vergleich von verschiedenen Methoden zur Erfassung der mikrobiellen Biomasse wurden die Gehalte von pilzlichem und bakteriellem Kohlenstoff an der Rhizoplane und in der Rhizosphäre quantifiziert. Dabei wurde die Fumigations-Extraktions-Methode zur Erfassung der mikrobiellen Biomasse eingesetzt. Ergosterol diente als Indikator für die pilzliche Biomasse und die Aminozucker Glucosamin und Muraminsäure sollten Aufschluss geben über die bakterielle und pilzliche Biomasse bzw. Residualmasse in den drei Probenfraktionen. Dazu wurden Umrechnungsfaktoren erstellt, die zur Berechnung des bakteriellen und pilzlichen Kohlenstoffs aus den Gehalten von Muraminsäure und Pilz-Glucosamin dienten. Die Bestimmung von Aminozuckern wurde insoweit modifiziert, dass sowohl in Boden- als auch in Wurzelhydrolysaten die Messung von Glucosamin, Galactosamin, Muraminsäure und Mannosamin gleichzeitig als automatisiertes Standardverfahren mit Hilfe der HPLC erfolgen konnte. Es wurden drei Gefäßversuche durchgeführt: Im ersten Versuch wurde der Einfluss der Pflanzenart auf die mikrobielle Besiedlung der Wurzeloberflächen untersucht. Dabei wurden Wurzeln und Rhizosphärenboden von 15 verschiedenen Pflanzenarten miteinander verglichen. Im zweiten Versuch stand der Einfluss der mikrobiellen Biomasse eines Bodens auf die mikrobielle Besiedlung von Wurzeloberflächen im Vordergrund. Deutsches Weidelgras (Lolium perenne L.) wurde auf sieben verschiedenen Böden angezogen. Bei den Böden handelte es sich um sechs Oberböden, die sich hinsichtlich des Bodentyps und der Bewirtschaftungsform voneinander unterschieden, und einen Unterboden. Im dritten Versuch wurde die mikrobielle Besiedlung von Wurzeln nach teilweiser und vollständiger Entfernung der oberirdischen Biomasse beobachtet. Welsches Weidelgras (Lolium multiflorum Lam.) wurde 24 Tage nach der Aussaat beschnitten. Anschließend wurde über einen Versuchszeitraum von acht Tagen die mikrobielle Besiedlung an den Wurzeln und in den Bodenfraktionen bestimmt. Es bestätigte sich, dass der Einfluss der einzelnen Pflanzenart von entscheidender Bedeutung für die mikrobielle Besiedlung von Wurzeln ist. Bei fast allen Pflanzen wurde die mikrobielle Biomasse an den Wurzeln von Pilzen dominiert. Das Verhältnis von pilzlichem zu bakteriellem Kohlenstoff an den Wurzeln der 15 Pflanzenarten lag im Mittel bei 2,6. Bei der Betrachtung verschiedener Böden zeigte sich, dass die mikrobielle Besiedlung in tieferen Bodenschichten signifikant niedriger ist als in den Oberböden. Dabei war der Pilzanteil an der mikrobiellen Biomasse im Unterboden deutlich erhöht. Der Vergleich der Oberböden untereinander ergab, dass sowohl der Bodentyp als auch die Bewirtschaftungsform einen signifikanten Einfluss auf mikrobielle Besiedlung ausüben. Durch die teilweise oder vollständige Entfernung der oberirdischen Biomasse wurde eine Veränderung der mikrobiellen Besiedlung an den Wurzeln beobachtet. Das Verhältnis von pilzlichem zu bakteriellem Kohlenstoff sank in dem Versuchszeitraum von 2,5 auf 1,4. Dabei war die Förderung der Pilze in der Variante mit teilweise entfernter oberirdischer Biomasse relativ größer als in der Variante mit vollständig entfernter oberirdischer Biomasse. Entgegen der weit verbreiteten Annahme, dass bei den wurzelbesiedelnden Mikroorganismen die Bakterien gegenüber den Pilzen dominieren, zeigten die Ergebnisse ein gegensätzliches Bild. In allen drei Versuchen ergab sich gleichermaßen, dass sowohl im Boden als auch an den Wurzeln die Pilze gegenüber den Bakterien dominieren.

Legume rotation effects on early growth and rhizosphere microbiology of sorghum in West African soils

Cereal yield increases in legume rotations on west African soils were the subject of much recent research aiming at the development of more productive cropping systems for the mainly subsistence-oriented agriculture in this region. However, little has been done to elucidate the possible contribution of soil microbiological factors to these rotation effects. Therefore a pot trial was conducted using legume rotation and continuous cereal soils each from one site in Burkina Faso and two sites in Togo where cropping system experiments had been conducted over 4 yrs. All soils were planted with seedlings of sorghum (Sorghum bicolor L. Moench). From 21 days after sowing onwards relative growth rates in rotation soils were higher than in the continuous cereal soils, resulting in between 69 and 500% higher shoot dry matter of rotation sorghum compared to sorghum growing in continuous cereal soils. Across sites rotation soils were characterized by higher pH, higher microbial N and a lower microbial biomass C/N ratio and, with the exception of one site, a higher fungal biomass in the rhizosphere. The bacterial and eukaryal community structure in the soil, assessed by denaturing gradient gel electrophoresis (DGGE), differed between sites. However, only at one site differed the bacterial and the eukaryal community structure in the rotation soil significantly from that in the continuous cereal soil. Although the results of this study confirmed the marked plantgrowth differences between sub-Saharan legume-rotation soils and their continuous cereal counterparts they also showed the difficulties to differentiate possible microbiological causes from their effects.

Salinity-induced changes in the microbial use of sugarcane filter cake added to soil

Five laboratory incubation experiments were carried out to assess the salinity-induced changes in the microbial use of sugarcane filter cake added to soil. The first laboratory experiment was carried out to prove the hypothesis that the lower content of fungal biomass in a saline soil reduces the decomposition of a complex organic substrate in comparison to a non-saline soil under acidic conditions. Three different rates (0.5, 1.0, and 2.0%) of sugarcane filter cake were added to both soils and incubated for 63 days at 30°C. In the saline control soil without amendment, cumulative CO2 production was 70% greater than in the corresponding non-saline control soil, but the formation of inorganic N did not differ between these two soils. However, nitrification was inhibited in the saline soil. The increase in cumulative CO2 production by adding filter cake was similar in both soils, corresponding to 29% of the filter cake C at all three addition rates. Also the increases in microbial biomass C and biomass N were linearly related to the amount of filter cake added, but this increase was slightly higher for both properties in the saline soil. In contrast to microbial biomass, the absolute increase in ergosterol content in the saline soil was on average only half that in the non-saline soil and it showed also strong temporal changes during the incubation: A strong initial increase after adding the filter cake was followed by a rapid decline. The addition of filter cake led to immobilisation of inorganic N in both soils. This immobilisation was not expected, because the total C-to-total N ratio of the filter cake was below 13 and the organic C-to-organic N ratio in the 0.5 M K2SO4 extract of this material was even lower at 9.2. The immobilisation was considerably higher in the saline soil than in the non-saline soil. The N immobilisation capacity of sugarcane filter cake should be considered when this material is applied to arable sites at high rations. The second incubation experiment was carried out to examine the N immobilizing effect of sugarcane filter cake (C/N ratio of 12.4) and to investigate whether mixing it with compost (C/N ratio of 10.5) has any synergistic effects on C and N mineralization after incorporation into the soil. Approximately 19% of the compost C added and 37% of the filter cake C were evolved as CO2, assuming that the amendments had no effects on the decomposition of soil organic C. However, only 28% of the added filter cake was lost according to the total C and d13C values. Filter cake and compost contained initially significant concentrations of inorganic N, which was nearly completely immobilized between day 7 and 14 of the incubation in most cases. After day 14, N re-mineralization occurred at an average rate of 0.73 µg N g-1 soil d-1 in most amendment treatments, paralleling the N mineralization rate of the non-amended control without significant difference. No significant net N mineralization from the amendment N occurred in any of the amendment treatments in comparison to the control. The addition of compost and filter cake resulted in a linear increase in microbial biomass C with increasing amounts of C added. This increase was not affected by differences in substrate quality, especially the three times larger content of K2SO4 extractable organic C in the sugarcane filter cake. In most amendment treatments, microbial biomass C and biomass N increased until the end of the incubation. No synergistic effects could be observed in the mixture treatments of compost and sugarcane filter cake. The third 42-day incubation experiment was conducted to answer the questions whether the decomposition of sugarcane filter cake also result in immobilization of nitrogen in a saline alkaline soil and whether the mixing of sugarcane filter cake with glucose (adjusted to a C/N ratio of 12.5 with (NH4)2SO4) change its decomposition. The relative percentage CO2 evolved increased from 35% of the added C in the pure 0.5% filter cake treatment to 41% in the 0.5% filter cake +0.25% glucose treatment to 48% in the 0.5% filter cake +0.5% glucose treatment. The three different amendment treatments led to immediate increases in microbial biomass C and biomass N within 6 h that persisted only in the pure filter cake treatment until the end of the incubation. The fungal cell-membrane component ergosterol showed initially an over-proportionate increase in relation to microbial biomass C that fully disappeared at the end of the incubation. The cellulase activity showed a 5-fold increase after filter cake addition, which was not further increased by the additional glucose amendment. The cellulase activity showed an exponential decline to values around 4% of the initial value in all treatments. The amount of inorganic N immobilized from day 0 to day 14 increased with increasing amount of C added in comparison to the control treatment. Since day 14, the immobilized N was re-mineralized at rates between 1.31 and 1.51 µg N g-1 soil d-1 in the amendment treatments and was thus more than doubled in comparison with the control treatment. This means that the re-mineralization rate is independent from the actual size of the microbial residues pool and also independent from the size of the soil microbial biomass. Other unknown soil properties seem to form a soil-specific gate for the release of inorganic N. The fourth incubation experiment was carried out with the objective of assessing the effects of salt additions containing different anions (Cl-, SO42-, HCO3-) on the microbial use of sugarcane filter cake and dhancha leaves amended to inoculated sterile quartz sand. In the subsequent fifth experiment, the objective was to assess the effects of inoculum and temperature on the decomposition of sugar cane filter cake. In the fourth experiment, sugarcane filter cake led to significantly lower respiration rates, lower contents of extractable C and N, and lower contents of microbial biomass C and N than dhancha leaves, but to a higher respiratory quotient RQ and to a higher content of the fungal biomarker ergosterol. The RQ was significantly increased after salt addition, when comparing the average of all salinity treatments with the control. Differences in anion composition had no clear effects on the RQ values. In experiment 2, the rise in temperature from 20 to 40°C increased the CO2 production rate by a factor of 1.6, the O2 consumption rate by a factor of 1.9 and the ergosterol content by 60%. In contrast, the contents of microbial biomass N decreased by 60% and the RQ by 13%. The effects of the inoculation with a saline soil were in most cases negative and did not indicate a better adaptation of these organisms to salinity. The general effects of anion composition on microbial biomass and activity indices were small and inconsistent. Only the fraction of 0.5 M K2SO4 extractable C and N in non-fumigated soil was consistently increased in the 1.2 M NaHCO3 treatment of both experiments. In contrast to the small salinity effects, the quality of the substrate has overwhelming effects on microbial biomass and activity indices, especially on the fungal part of the microbial community.

Effects of tillage on processes of organic matter sequestration

To increase the organic matter (OM) content in the soil is one main goal in arable soil management. The adoption of tillage systems with reduced tillage depth and/or frequency (reduced tillage) or of no-tillage was found to increase the concentration of soil OM compared to conventional tillage (CT; ploughing to 20-30 cm). However, the underlying processes are not yet clear and are discussed contradictorily. So far, few investigations were conducted on tillage systems with a shallow tillage depth (minimum tillage = MT; maximum tillage depth of 10 cm). A better understanding of the interactions between MT implementation and changes in OM transformation in soils is essential in order to evaluate the possible contribution of MT to a sustainable management of arable soils. The objectives of the present thesis were (i) to compare OM concentrations, microbial biomass, water-stable aggregates, and particulate OM (POM) between CT and MT soils, (ii) to estimate the temporal variability of water-stable aggregate size classes occurring in the field and the dynamics of macroaggregate (>250 µm) formation and disruption under controlled conditions, (iii) to investigate whether a lower disruption or a higher formation rate accounts for a higher occurrence of macroaggregates under MT compared to CT, (iv) to determine which fraction is the major agent for storing the surplus of OM found under MT compared to CT, and (v) to observe the early OM transformation after residue incorporation in different tillage systems simulated. Two experimental sites (Garte-Süd and Hohes Feld) near Göttingen, Germany, were investigated. Soil type of both sites was a Haplic Luvisol. Since about 40 years, both sites receive MT by a rotary harrow (to 5-8 cm depth) and CT by a plough (to 25 cm depth). Surface soils (0-5 cm) and subsoils (10-20 cm) of two sampling dates (after fallow and directly after tillage) were investigated for concentrations of organic C (Corg) and total N (N), different water-stable aggregate size classes, different density fractions (for the sampling date after fallow only), microbial biomass, and for biochemically stabilized Corg and N (by acid hydrolysis; for the sampling date after tillage only). In addition, two laboratory incubations were performed under controlled conditions: Firstly, MT and CT soils were incubated (28 days at 22°C) as bulk soil and with destroyed macroaggregates in order to estimate the importance of macroaggregates for the physical protection of the very labile OM against mineralization. Secondly, in a microcosm experiment simulating MT and CT systems with soil <250 µm and with 15N and 13C labelled maize straw incorporated to different depths, the mineralization, the formation of new macroaggregates, and the partitioning of the recently added C and N were followed (28 days at 15°C). Forty years of MT regime led to higher concentrations of microbial biomass and of Corg and N compared to CT, especially in the surface soil. After fallow and directly after tillage, a higher proportion of water-stable macroaggregates rich in OM was found in the MT (36% and 66%, respectively) than in the CT (19% and 47%, respectively) surface soils of both sites (data shown are of the site Garte-Süd only). The subsoils followed the same trend. For the sampling date after fallow, no differences in the POM fractions were found but there was more OM associated to the mineral fraction detected in the MT soils. A large temporal variability was observed for the abundance of macroaggregates. In the field and in the microcosm simulations, macroaggregates were found to have a higher formation rate after the incorporation of residues under MT than under CT. Thus, the lower occurrence of macroaggregates in CT soils cannot be attributed to a higher disruption but to a lower formation rate. A higher rate of macroaggregate formation in MT soils may be due to (i) the higher concentrated input of residues in the surface soil and/or (ii) a higher abundance of fungal biomass in contrast to CT soils. Overall, as a location of storage of the surplus of OM detected under MT compared to CT, water-stable macroaggregates were found to play a key role. In the incubation experiment, macroaggregates were not found to protect the very labile OM against mineralization. Anyway, the surplus of OM detected after tillage in the MT soil was biochemically degradable. MT simulations in the microcosm experiment showed a lower specific respiration and a less efficient translocation of recently added residues than the CT simulations. Differences in the early processes of OM translocation between CT and MT simulations were attributed to a higher residue to soil ratio and to a higher proportion of fungal biomass in the MT simulations. Overall, MT was found to have several beneficial effects on the soil structure and on the storage of OM, especially in the surface soil. Furthermore, it was concluded that the high concentration of residues in the surface soil of MT may alter the processes of storage and decomposition of OM. In further investigations, especially analysis of the residue-soil-interface and of effects of the depth of residue incorporation should be emphasised. Moreover, further evidence is needed on differences in the microbial community between CT and MT soils.

Effects of grassland renovation on carbon concentrations and aggregate distribution in temperate grassland soils

The effects of continuous tillage on the distribution of soil organic matter (SOM) and aggregates have been well studied for arable soils. However, less is known about the effects of sporadic tillage on SOM and aggregate dynamics in grassland soils. The objectives of the present thesis were (I) to study the longer-term effects of sporadic tillage of grassland on organic carbon (Corg) stocks and the distribution of aggregates and SOM, (II) to investigate the combined effects of sporadic tillage and fertilization on carbon and nitrogen dynamics in grassland soils, and (III) to study the temporal dynamics of Corg stocks, aggregate distribution and microbial biomass in grassland soils. Soil samples were taken in three soil depths (0 – 10 cm; 10 – 25 cm; 25 – 40 cm) from a field trial with loamy sandy soils (Cambisols, Eutric Luvisols, Stagnosols, Anthrosols) north of Kiel, Germany. For Objective I we have sampled soil two and five years after one or two tillage operation(s). Treatments consisted of (i) permanent grassland, (ii) tillage of grassland followed by a re-establishment of grassland and (iii) tillage of grassland followed by a re-establishment of grassland with one season of winter wheat in between. The tillage in grassland led to a reduction in Corg stocks, large macroaggregates (>2000 µm) and SOM in the top 10 cm soil depth. These findings were still significant two years after tillage; however, five years after tillage no longer present. Regarding the soil profile (0 – 40 cm) no significant differences in the mentioned parameters between the tilled plots and the permanent grassland existed. A second tillage event and the insertion of one season of winter wheat did not lead to any further effects on Corg stocks as well as aggregate and SOM concentrations in comparison with a single tillage event in these grassland soils. Treatments adapted for Objective II included (i) long-term grassland and (ii) tillage of grassland followed by a re-establishment of grassland with one season of winter wheat in between. The plots were split and received either 240 kg N ha-1 year-1 in the form of cattle slurry or no cattle slurry application. The application of slurry within a period of four years had no effects on the Corg and total nitrogen stocks or the aggregate distribution, but led to a reduction of free and not physically protected SOM. However, the application of cattle slurry and the grassland renovation seems to change the plant species composition and therefore generalizations on the direct effects are not yet possible. For studying Objective III a further field trial was initiated in September 2010. Soil samples were taken six times within one year (from October 2010 to October 2011) (i) after the conversion from arable land into grassland, (ii) after the tillage of grassland followed by a re-establishment of grassland and (iii) in a permanent grassland. We found an increase in the microbial and fungal biomass after the conversion of arable land into grassland, but no effect on aggregate distribution and Corg stocks. A one-time tillage operation in grassland led to a reduction in large macroaggregates and Corg stocks in the top 10 cm soil depth with no effect on the sampled soil profile. However, we found large variations in the fungal biomass and aggregate distribution within one year in the permanent grassland, presumably caused by environmental factors. Overall, our results suggest that a single tillage operation in grassland soils markedly decreased the concentrations of Corg, larger aggregates and SOM. However, this does not result in long-lasting effects on the above mentioned parameters. The application of slurry cannot compensate the negative effects of a tillage event on aggregate concentrations or Corg stocks. However, while the Corg concentration is not subject to fluctuations within a year, there are large variations of the aggregate distribution even in a permanent grassland soil. Therefore conclusions of results from a single sampling time should be handled with care.

Monitoreo microbiológico de aire, superficies y manos del personal asistencial en entidades de salud : Departamento del Meta 2007

OBJETIVO: Cuantificar Bacterias gram positivas, Bacterias gram negativas y Hongos mediante monitoreo microbiológico de aire, superficies y manos del personal asistencial en cinco entidades de salud del departamento del Meta en el año 2007. MÉTODOS: Estudio ejecutado en cinco entidades, donde se realizó el diagnostico microbiológico del entorno hospitalario, tomando muestras en cada área asistencial de: superficies horizontales antes y después de aplicar el protocolo de limpieza y desinfección de cada institución, manos de personal asistencial antes y después del lavado rutinario de manos y del aire de áreas críticas y no críticas. RESULTADOS: La IPS 3 presentó el Aire de Zona crítica con mayor contaminación bacteriana y la IPS 4 mayor contaminación fúngica. Hospitalización, Urgencias y Apoyo diagnostico evidenciaron las mayores concentraciones microbianas. Se encontraron diferencias estadísticamente significativas entre la carga microbiana antes respecto a después del lavado de manos (p<0,05) y antes y después de la aplicación del protocolo de limpieza y desinfección de superficies. CONCLUSIONES: Con el presente estudio fue posible demostrar que la capacitación, supervisión y monitorización de los procesos de lavado de manos y limpieza y desinfección de superficies pueden llegar a garantizar la reducción de la biomasa bacteriana y fúngica presente en las entidades de la salud.

Use of soybean oil fry waste for economical biosurfactant production by isolated Pseudomonas aeruginosa using response surface methodology

The present study sought biotensoactive production from soybean oil fry waste using Pseudomonas aeruginosa ATCC 10145 and Pseudomonas aeruginosa isolated from the soil of a petroleum station having undergone gasoline and diesel oil spills. The results of the experiments were analyzed using a complete factorial experimental design, investigating the concentration of soybean oil waste, ammonia sulfate and residual brewery yeast. Assays were performed in 250-mL Erlenmeyer beakers containing 50 mL of production medium, maintained on a rotary shaker at 200 rpm and a temperature of 30±1 °C for a 48-hour fermentation period. Biosurfactant production was monitored through the determination of rhamnose, surface tension and emulsification activity. The Pseudomonas aeruginosa ATCC 10145 strain and isolated Pseudomonas aeruginosa were able to reduce the surface tension of the initial mexlium from 61 mN/m to 32.5 mN/m and 30.0 mN/m as well as produce rhamnose at concentrations of 1.96 and 2.89 g/L with emulsification indices of 96% and 100%, respectively.