Anaerobic digestion (AD) of microalgae is primarily inhibited by the chemical composition of their cell walls containing biopolymers able to resist bacterial degradation. Adoption of pre-treatments such as thermal, thermal hydrolysis, ultrasound and enzymatic hydrolysis have the potential to remove these inhibitory compounds and enhance biogas yields by degrading the cell wall, and releasing the intracellular algogenic organic matter (AOM). This work investigated the effect of four pre-treatments on three microalgae species, and their impact on the quantity of soluble biomass released in the media and thus on the digestion process yields. The analysis of the composition of the soluble COD released and of the TEM images of the cells showed two main degradation actions associated with the processes: (1) cell wall damage with the release of intracellular AOM (thermal, thermal hydrolysis and ultrasound) and (2) degradation of the cell wall constituents with the release of intracellular AOM and the solubilisation of the cell wall biopolymers (enzymatic hydrolysis). As a result of this, enzymatic hydrolysis showed the greatest biogas yield increments (>270%) followed by thermal hydrolysis (60-100%) and ultrasounds (30-60%).

• MeSH
• anaerobióza MeSH
• biomasa MeSH
• biopaliva MeSH
• bioreaktory mikrobiologie   MeSH
• buněčná stěna metabolismus   MeSH
• enzymy metabolismus   MeSH
• hydrolýza MeSH
• mikrořasy metabolismus   MeSH
• ultrazvukové vlny MeSH
• vysoká teplota MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

*Stabilizing selection is a key evolutionary mechanism for which there is relatively little experimental evidence. To date, stabilizing selection has never been observed at the whole-genome level. *We tested the effect of selection on genome size in a field experiment using seeds collected in a population of Festuca pallens with a highly variable genome size. Using flow cytometry, we measured the genome size in germinating seedlings and juvenile plants grown with or without high intraspecific competition (908 individuals). Above-ground biomass and leaf number were used as measurements of individual vegetative performance. The possible confounding effect of seed weight was controlled for in a separate experiment. *Growth under high competition had a significant stabilizing effect on genome size. Because no relationship was observed between genome size and vegetative performance, we assume that the elimination of plants with extreme genome sizes was the result of decreased survival as a consequence of some unrecognized stress. *Our results indicate that genome size may be under direct selection. The equal disadvantaging of either large or small genomes indicates that the selection for optimum genome size in species may be fully context dependent. This study demonstrates the power of competition experiments for the detection of weak selection processes.

• MeSH
• analýza rozptylu MeSH
• biomasa MeSH
• Festuca genetika   růst a vývoj   MeSH
• genetická variace MeSH
• genom rostlinný MeSH
• listy rostlin MeSH
• molekulární evoluce MeSH
• neparametrická statistika MeSH
• populační genetika MeSH
• selekce (genetika) MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

Antagonistic Bacillus spp. displaying in vitro production of siderophore, chitinase, and β-1,3-glucanase were identified from dual culture assays. In independent greenhouse studies, seed bacterization and soil application of Bacillus atrophaeus S2BC-2 challenge inoculated with Fusarium oxysporum f.sp. lycopersici (FOL) and Alternaria solani (AS) recorded low percent disease index of 25.3 and 28.7, respectively, over nonbacterised pathogen control (44.3 and 56.4). The low disease incidence corroborated with tomato growth promotion with high vigor index (8,041.2) and fresh plant weight (82.5 g) on challenge inoculation with FOL. Analysis of root and leaf samples in rhizobacterial treatment challenged with FOL and AS revealed maximum induction of chitinase (1.9 and 1.7 U/mg of protein, respectively) and β-1,3-glucanase (23.5 and 19.2 U/mg of protein, respectively). In native gel activity assays, the rhizobacterial treatment on challenge inoculation strongly expressed three high intensity PO isoforms along with one low intensity isoform. In studies on genetic diversity of the Bacillus strains by repetitive extragenomic palindromic-polymerase chain reaction (REP-PCR) and amplified rDNA restriction analysis (ARDRA) patterns, ARDRA was more highly discriminant than REP-PCR and allowed grouping of the strains and differentiation of the antagonistic strains from other isolates.

• MeSH
• Alternaria růst a vývoj   patogenita   MeSH
• antibióza MeSH
• Bacillus klasifikace   izolace a purifikace   metabolismus   fyziologie   MeSH
• biologická kontrola škůdců metody   MeSH
• biomasa MeSH
• chitinasy sekrece   MeSH
• DNA bakterií genetika   MeSH
• Fusarium růst a vývoj   patogenita   MeSH
• glukan-1,3-beta-glukosidasa sekrece   MeSH
• kořeny rostlin mikrobiologie   MeSH
• listy rostlin mikrobiologie   MeSH
• molekulární typizace MeSH
• nemoci rostlin mikrobiologie   MeSH
• siderofory sekrece   MeSH
• Solanum lycopersicum růst a vývoj   mikrobiologie   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

The freshwater alga Chlorella, a highly productive source of starch, might substitute for starch-rich terrestrial plants in bioethanol production. The cultivation conditions necessary for maximizing starch content in Chlorella biomass, generated in outdoor scale-up solar photobioreactors, are described. The most important factor that can affect the rate of starch synthesis, and its accumulation, is mean illumination resulting from a combination of biomass concentration and incident light intensity. While 8.5% DW of starch was attained at a mean light intensity of 215 µmol/(m2 s1), 40% of DW was synthesized at a mean light intensity 330 µmol/(m2 s1). Another important factor is the phase of the cell cycle. The content of starch was highest (45% of DW) prior to cell division, but during the course of division, its cellular level rapidly decreased to about 13% of DW in cells grown in light, or to about 4% in those kept in the dark during the division phase. To produce biomass with high starch content, it is necessary to suppress cell division events, but not to disturb synthesis of starch in the chloroplast. The addition of cycloheximide (1 mg/L), a specific inhibitor of cytoplasmic protein synthesis, and the effect of element limitation (nitrogen, sulfur, phosphorus) were tested. The majority of the experiments were carried out in laboratory-scale photobioreactors, where culture treatments increased starch content to up to about 60% of DW in the case of cycloheximide inhibition or sulfur limitation. When the cells were limited by phosphorus or nitrogen supply, the cellular starch content increased to 55% or 38% of DW, respectively, however, after about 20 h, growth of the cultures stopped producing starch, and the content of starch again decreased. Sulfur limited and cycloheximide-treated cells maintained a high content of starch (60% of DW) for up to 2 days. Sulfur limitation, the most appropriate treatment for scaled-up culture of starch-enriched biomass, was carried out in an outdoor pilot-scale experiment. After 120 h of growth in complete mineral medium, during which time the starch content reached around 18% of DW, sulfur limitation increased the starch content to 50% of DW.

• MeSH
• biomasa MeSH
• biotechnologie metody   MeSH
• Chlorella vulgaris metabolismus   MeSH
• dusík metabolismus   MeSH
• fosfor metabolismus   MeSH
• fotobioreaktory MeSH
• mikrořasy metabolismus   MeSH
• síra metabolismus   MeSH
• škrob biosyntéza   metabolismus   MeSH
• sluneční záření MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

Aerobic anoxygenic photosynthetic bacteria are an important component of marine microbial communities. They produce energy in light using bacteriochlorophyll a containing photosystems. This extra energy provides an advantage over purely heterotrophic bacteria. One of the most intensively studied AAP bacteria is Dinoroseobacter shibae, a member of the environmentally important Roseobacter clade. Light stimulates its growth and metabolism, but the effect of light intensity remains unclear. Here, we show that an increase in biomass along an irradiance gradient followed the exponential rise to the maximum curve, with saturation at about 300 µmol photons m-2 s-1 , without any inhibition at light intensities up to 600 µmol photons m-2 s-1 . The cells adapted to higher irradiance by reducing pigmentation and increasing the electron transfer rate. This additional energy allowed D. shibae to redirect the metabolism of organic carbon sources such as glucose, leucine, glutamate, acetate and pyruvate toward anabolism, resulting in a twofold increase of their assimilation rates. We provide equations that can be feasibly incorporated into the existing model of D. shibae metabolism to further advance our understanding of the role of photoheterotrophy in the ocean.

• MeSH
• bakteriochlorofyl A metabolismus   MeSH
• biomasa MeSH
• energetický metabolismus fyziologie   MeSH
• fotosyntéza fyziologie   MeSH
• organické látky metabolismus   MeSH
• Roseobacter metabolismus   MeSH
• světlo MeSH
• transport elektronů fyziologie   MeSH
• vodní organismy metabolismus   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

Yeasts Cryptococcus humicola accumulated cadmium, cobalt, and iron (~ 50, 17, and 4% of the content in the medium, respectively) from the medium containing glucose, phosphate, and 2 mmol/L of metal salts. The effects of metal absorption on the levels of orthophosphate (Pi) and inorganic polyphosphate (polyP) varied for the metals under study. The levels of Pi and polyP increased in the case of cadmium and cobalt, respectively. In the case of iron, no changes in the levels of Pi and polyP were observed. Multiple DAPI-stained polyP inclusions were observed in the cytoplasm of cadmium-containing cells. The intensity of DAPI staining of the cell wall especially increased in case of cobalt and iron accumulation.

• MeSH
• biomasa MeSH
• Cryptococcus metabolismus   MeSH
• dusík metabolismus   MeSH
• kadmium chemie   metabolismus   farmakokinetika   MeSH
• kobalt chemie   metabolismus   farmakokinetika   MeSH
• polyfosfáty chemie   metabolismus   farmakokinetika   MeSH
• sorpční detoxikace MeSH
• železo chemie   metabolismus   farmakokinetika   MeSH
• Publikační typ
• časopisecké články MeSH

Aerobic anoxygenic phototrophs contain photosynthetic reaction centers composed of bacteriochlorophyll. These organisms are photoheterotrophs, as they require organic carbon substrates for their growth whereas light-derived energy has only an auxiliary function. To establish the contribution of light energy to their metabolism, we grew the phototrophic strain Erythrobacter sp. NAP1 in a carbon-limited chemostat regimen on defined carbon sources (glutamate, pyruvate, acetate, and glucose) under conditions of different light intensities. When grown in a light-dark cycle, these bacteria accumulated 25% to 110% more biomass in terms of carbon than cultures grown in the dark. Cultures grown on glutamate accumulated the most biomass at moderate light intensities of 50 to 150 μmol m(-2) s(-1) but were inhibited at higher light intensities. In the case of pyruvate, we did not find any inhibition of growth by high irradiance. The extent of anaplerotic carbon fixation was detemined by radioactive bicarbonate incorporation assays. While the carboxylation activity provided 4% to 11% of the cellular carbon in the pyruvate-grown culture, in the glutamate-grown cells it provided only approximately 1% of the carbon. Additionally, we tested the effect of light on respiration and photosynthetic electron flow. With increasing light intensity, respiration decreased to approximately 25% of its dark value and was replaced by photophosphorylation. The additional energy from light allows the aerobic anoxygenic phototrophs to accumulate the supplied organic carbon which would otherwise be respired. The higher efficiency of organic carbon utilization may provide an important competitive advantage during growth under carbon-limited conditions.

• MeSH
• aerobióza MeSH
• biomasa MeSH
• fototrofní procesy * MeSH
• hydrogenuhličitany metabolismus   MeSH
• izotopové značení MeSH
• izotopy uhlíku metabolismus   MeSH
• koloběh uhlíku MeSH
• kultivační média chemie   MeSH
• pyruváty metabolismus   MeSH
• Sphingomonadaceae metabolismus   účinky záření   MeSH
• světlo * MeSH
• tma MeSH
• transport elektronů MeSH
• uhlík metabolismus   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

Centrifugation is the most commonly used method for harvesting autotrophically produced microalgae, but it is expensive due to high energy demands. With the aim of reducing these costs, we tested electrocoagulation with iron electrodes for harvesting Chlorella vulgaris. During extensive lab-scale experiments, the following factors were studied to achieve a high harvesting efficiency and a low iron content in the harvested biomass: electric charge, initial biomass concentration, pH, temperature, agitation intensity, residual salt content and electrolysis time. A harvesting efficiency greater than 95% was achieved over a broad range of conditions and the residual iron content in the biomass complied with legislative requirements for food. Using electrocoagulation as the pre-concentration step prior to centrifugation, total energy costs were reduced to 0.136 kWh/kg of dry biomass, which is less than 14% of that for centrifugation alone. Our data show that electrocoagulation is a suitable and cost-effective method for harvesting microalgae.

• MeSH
• biomasa MeSH
• Chlorella vulgaris * MeSH
• elektrokoagulace MeSH
• elektrolýza MeSH
• flokulace MeSH
• mikrořasy * MeSH
• Publikační typ
• časopisecké články MeSH

The trend of emerging biorefineries is to process the harvest as efficiently as possible and without any waste. From the most valuable phytomass, refined medicines, enzymes, dyes and other special reactants are created. Functional foods, food ingredients, oils, alcohol, solvents, plastics, fillers and a wide variety of other chemical products follow. After being treated with nutrient recovery techniques (for fertilizer production), biofuels or soil improvers are produced from the leftovers. Economic optimization algorithms have confirmed that such complex biorefineries can be financially viable only when a high degree of feedstock concentration is included. Because the plant material is extremely voluminous before processing, the farming intensity of special plants increases in the nearest vicinity of agglomerations where the biorefineries are built for logistical reasons. Interdisciplinary analyses revealed that these optimization measures lead to significantly increased pollen levels in neighbouring urban areas and subsequently an increased risk of allergies, respectively costs to the national health system. A new moral dilemma between the shareholder's profit and public interest was uncovered and subjected to disputation.

• MeSH
• alergie etiologie   MeSH
• analýza nákladů a výnosů MeSH
• biomasa MeSH
• biopaliva * MeSH
• biotechnologie MeSH
• etika podnikání MeSH
• lidé MeSH
• mravy MeSH
• poskytování zdravotní péče ekonomika   MeSH
• průmysl ekonomika   etika   MeSH
• průmyslová hnojiva * MeSH
• pyl škodlivé účinky   MeSH
• rostliny * MeSH
• sociální odpovědnost MeSH
• technologie * MeSH
• vystavení vlivu životního prostředí škodlivé účinky   etika   MeSH
• zemědělství ekonomika   etika   MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH

The loss of biodiversity is thought to have adverse effects on multiple ecosystem functions, including the decline of community stability. Decreased diversity reduces the strength of the portfolio effect, a mechanism stabilizing community temporal fluctuations. Community stability is also expected to decrease with greater variability in individual species populations and with synchrony of their fluctuations. In semi-natural meadows, eutrophication is one of the most important drivers of diversity decline; it is expected to increase species fluctuations and synchrony among them, all effects leading to lower community stability. With a 16-year time series of biomass data from a temperate species-rich meadow with fertilization and removal of the dominant species, we assessed population biomass temporal (co)variation under different management types and competition intensity, and in relation to species functional traits and to species diversity. Whereas the effect of dominant removal was relatively small (with a tendency toward lower stability), fertilization markedly decreased community stability (i.e., increased coefficient of variation in the total biomass) and species diversity. On average, the fluctuations of individual populations were mutually independent, with a slight tendency toward synchrony in unfertilized plots, and a tendency toward compensatory dynamics in fertilized plots and no effects of removal. The marked decrease of synchrony with fertilization, contrary to the majority of the results reported previously, follows the predictions of increased compensatory dynamics with increased asymmetric competition for light in a more productive environment. Synchrony increased also with species functional similarity stressing the importance of shared ecological strategies in driving similar species responses to weather fluctuations. As expected, the decrease of temporal stability of total biomass was mainly related to the decrease of species richness, with its effect remaining significant also after accounting for fertilization. The weakening of the portfolio effect with species richness decline is a crucial driver of community destabilization. However, the positive effect of species richness on temporal stability of total biomass was not due to increased compensatory dynamics, since synchrony increased with species richness. This shows that the negative effect of eutrophication on community stability does not operate through increasing synchrony, but through the reduction of diversity.

• MeSH
• biodiverzita * MeSH
• biomasa MeSH
• ekologie MeSH
• ekosystém * MeSH
• eutrofizace MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH