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1.
Microbially produced extracellular polymeric substances (EPS) have been linked with many important ecological functions in
natural sediments; yet, most information has been derived from marine systems. The present paper is the first comprehensive
study on EPS (i.e., carbohydrates and proteins) dynamics in riverine sediments addressing spatial (six reservoirs and four
groyne fields across three European rivers), temporal (all seasons in 2003–2005), and vertical (over a 50-cm sediment depth
transect) pattern. The variation in hydrodynamic regime found in the reservoirs and groyne fields was reflected in the biomass
and composition of the benthic microorganisms that produce EPS. The microphytobenthic communities consisted mainly of diatoms
and a higher algal biomass (up to 248 μg g−1 dry weight, DW) seemed to be indicative for higher amounts of secreted colloidal carbohydrates. Consequently, the model proposed
by Underwood and Smith (1998) for the relation chlorophyll–colloidal carbohydrates was also applicable for upper riverine sediment layers. The close relation
between algal biomass and bacterial cell counts (108–109 cells g−1 DW) supports the idea of bacterial use of the secreted EPS. However, the data also suggest a contribution to the EPS pool
through bacterial secretion of proteins/extracellular enzymes and possibly carbohydrates. Over depth, the relationships between
microorganisms and EPS became increasingly decoupled along with increasing ratios of bound (refractory) to colloidal (labile)
EPS. These data suggest fresh production of polymeric substances in upper sediment layers and mainly accumulation of refractory,
biodegraded material in deeper layers. The high contents of EPS colloidal and bound carbohydrates (0.1–1.8 and 1.3–6.7 mg
g−1 DW, respectively) and EPS proteins (0.4–12.9 mg g−1 DW) at the freshwater study sites might indicate an important role in sediment ecology. 相似文献
2.
Formation of extracellular polymeric substances from acidogenic sludge in H<Subscript>2</Subscript>-producing process 总被引:1,自引:0,他引:1
In this study, the formation of extracellular polymeric substances (EPS) and surface characteristics of an acidogenic sludge
in anaerobic H2-producing process was investigated. Results show that carbohydrates, proteins, and humic substances were the dominant components
in bound EPS (BEPS), while in soluble EPS (SEPS), carbohydrates were the main component. The total content of BEPS initially
increased but then kept almost unchanged during fermentation from 25 to 35 h; after that, it slightly decreased. The total
content of SEPS increased to 172.5 ± 0.05 mg C g−1 volatile suspended solid with the time that increased to 23.5 h, and then rapidly decreased until 43 h; thereafter, it kept
almost unchanged. The SEPS had good correlations with the specific H2 production rate, substrate degradation rate, and specific aqueous products formation rate, but the BEPS seemed to have no
such correlations with these specific rates. Results also confirm that part of EPS could be utilized by the H2-producing sludge. As the substrate was in short supply, the EPS would be hydrolyzed to sever as carbon and energy source. 相似文献
3.
Single-culture aerobic granules with <Emphasis Type="Italic">Acinetobacter calcoaceticus</Emphasis> 总被引:1,自引:0,他引:1
Aerobic granules are cultivated by a single bacterial strain, Acinetobacter calcoaceticus, in a sequencing batch reactor (SBR). This strain presents as a good phenol reducer and an efficient auto coagulator in the
presence of phenol, mediated by heat-sensitive adhesins proteins. Stable 2.3-mm granules were formed in the SBR following
a 7-week cultivation. These granules exhibit excellent settling attributes and degrade phenol efficiently at concentrations
of 250–2,000 mg l−1. The corresponding phenol degradation rate reached 993.6 mg phenol g−1 volatile suspended solids (VSS) day−1 at 250 mg l−1 phenol and 519.3 mg phenol g−1 VSS day−1 at 2,000 mg l−1 phenol concentration. Meanwhile, free A. calcoaceticus cells were fully inhibited at phenol >1,500 mg l−1. Denaturing gradient gel electrophoresis fingerprint profile demonstrated no genetic modification in the strain during aerobic
granulation. The present single-strain granules showed long-term structural stability and performed high phenol degrading
capacity and high phenol tolerance. The confocal laser scanning microscopic test revealed that live A. calcoaceticus cells principally distributed at 200–250 μm beneath the outer surface, with an extracellular polymeric substance layer covering
them to defend phenol toxicity. Autoaggregation assay tests demonstrated the possibly significant role of secreted proteins
on the formation of single-culture A. calcoaceticus granules. 相似文献
4.
Extracellular enzymes in a polyhumic lake: important regulators in detritus processing 总被引:6,自引:3,他引:3
Eight extracellular enzymes and their corresponding natural substrates were studied in an acid polyhumic lake. Highest activities
were found for phosphatases (100–150 nmol 1−1 h−1), glucosidase (70–120 nmol 1−1 h−1), and aminopeptidases (20–30 nmol l−1 h−1), Significant relationships were found for natural polymeric substrate composition, variation and enzyme activities. Identified
carbohydrates and amino acids contributed 1–5% to the DOC pool and are assumed to undergo significant processing by microbial
glycosidases and aminopeptidases. Measured enzymes are partially modified in their activity by lake water acidity, temperature
and humic matter. Extracellular enzymes are regarded as important regulators in microbial detritus processing and substrate
utilization. 相似文献
5.
Production of extracellular polymeric substances from Rhodopseudomonas acidophila in the presence of toxic substances 总被引:2,自引:0,他引:2
A hydrogen-producing photosynthetic bacteria strain, Rhodopseudomonas acidophila, was used to investigate the production of extracellular polymeric substances (EPS) in the presence of toxic substances and the effect of toxicants on bacterial surface characteristics. Addition of the toxic substances including Cu(II), Cr(VI), Cd(II) and 2,4-dichlorophenol (2,4-DCP) stimulated the production of EPS but reduced the cell dry weight. At concentrations of 30 mg l−1 Cu(II), 40 mg l−1 Cr(VI), 5 mg l−1 Cd(II) and 100 mg l−1 2,4-DCP, the EPS content increased by 5.5, 2.5, 4.0 and 1.4 times, respectively, than the control. These toxic substances also greatly influenced the proteins/carbohydrates ratio of EPS. The ratios in the presence of toxic substances were always higher than that of control. Furthermore, under toxic conditions, the increase in the protein content far exceeded than that of others in EPS, suggesting that extracellular proteins could protect cells against toxic substances. The toxic substances significantly changed the surface characteristics and flocculation ability of R. acidophila, such as surface energy, relative hydrophobicity and free energy of adhesion. 相似文献
6.
Sunil S. Adav Duu-Jong Lee Juin-Yih Lai 《Applied microbiology and biotechnology》2009,84(6):1181-1189
Efficient nitrification and denitrification of wastewater containing 1,700 mgl−1 of ammonium-nitrogen was achieved using aerobic granular sludge cultivated at medium-to-high organic loading rates. The cultivated
granules were tested in a sequencing batch reactor (SBR) fed with 6.4 or 10.2 kg NH4+-N m−3 day−1, a loading significantly higher than that reported in literature. With alternating 2 h oxic and 2 h anoxic operation (OA)
modes, removal rate was 45.5 mg NH4+-N g−1 volatile suspended solids−1 h−1 at 6.4 kg NH4+-N m−3 day−1 loading and 41.3 ± 2.0 at 10.2 kg NH4+-N m−3 day−1 loading. Following the 60 days SBR test, granules were intact. The fluorescence in situ hybridization and confocal laser
scanning microscopy results indicate that the SBR-OA granules have a distribution with nitrifers outside and heterotrophs
outside that can effectively expose functional strains to surrounding substrates at high concentrations with minimal mass
transfer limit. This microbial alignment combined with the smooth granule surface achieved nitrification–denitrification of
wastewaters containing high-strength ammonium using aerobic granules. Conversely, the SBR continuous aeration mode yielded
a distribution with nitrifers outside and heterotrophs inside with an unsatisfactory denitrification rate and floating granules
as gas likely accumulated deep in the granules. 相似文献
7.
Sunil S. Adav Duu-Jong Lee Juin-Yih Lai 《Applied microbiology and biotechnology》2010,85(5):1601-1610
Aerobic sludge granules are compact, strong microbial aggregates that have excellent settling ability and capability to efficiently
treat high-strength and toxic wastewaters. Aerobic granules disintegrate under high organic loading rates (OLR). This study
cultivated aerobic granules using acetate as the sole carbon and energy source in three identical sequencing batch reactors
operated under OLR of 9–21.3 kg chemical oxygen demand (COD) m−3 day−1. The cultivated granules removed 94–96% of fed COD at OLR up to 9–19.5 kg COD m−3 day−1, and disintegrated at OLR of 21.3 kg COD m−3 day−1. Most tested isolates did not grow in the medium at >3,000 mg COD l−1; additionally, these strains lost capability for auto-aggregation and protein or polysaccharide productivity. This critical
COD regime correlates strongly with the OLR range in which granules started disintegrating. Reduced protein quantity secreted
by isolates was associated with the noted poor granule integrity under high OLR. This work identified a potential cause of
biological nature for aerobic granules breakdown. 相似文献
8.
In order to understand the fate of PCP in upflow anaerobic sludge blanket reactor (UASB) more completely, the sorption and
biodegradation of pentachlorophenol (PCP) by anaerobic sludge granules were investigated. The anaerobic granular sludge degrading
PCP was formed in UASB reactor, which was seeded with anaerobic sludge acclimated by chlorophenols. At the hydraulic retention
time (HRT) of 20–22 h, and PCP loading rate of 200–220 mg l−1 d−1, UASB reactor exhibited good performance in treating wastewater which containing 170–180 mg l−1 PCP and the PCP removal rate of 99.5% was achieved. Sequential appearance of tetra-, tri-, di-, and mono-chlorophenol was
observed in the reactor effluent after 20 mg l−1 PCP introduction. Sorption and desorption of PCP on the anaerobic sludge granules were all fitted to the Freundlich isotherm
equation. Sorption of PCP was partly irreversible. The Freundlich equation could describe the behavior of PCP amount sorbed
by granular sludge in anaerobic reactor reasonably well. The results demonstrated that the main mechanism leading to removal
of PCP on anaerobic granular sludge was biodegradation, not sorption or volatization. 相似文献
9.
High-rate biological conversion of sulfide and nitrate in synthetic wastewater to, respectively, elemental sulfur (S0) and nitrogen-containing gas (such as N2) was achieved in an expanded granular sludge bed (EGSB) reactor. A novel strategy was adopted to first cultivate mature granules
using anaerobic sludge as seed sludge in sulfate-laden medium. The cultivated granules were then incubated in sulfide-laden
medium to acclimate autotrophic denitrifiers. The incubated granules converted sulfide, nitrate, and acetate simultaneously
in the same EGSB reactor to S0, N-containing gases and CO2 at loading rates of 3.0 kg S m−3 d−1, 1.45 kg N m−3 d−1, and 2.77 kg Ac m−1 d−1, respectively, and was not inhibited by sulfide concentrations up to 800 mg l−1. Effects of the C/N ratio on granule performance were identified. The granules cultivated in the sulfide-laden medium have
Pseudomonas spp. and Azoarcus sp. presenting the heterotrophs and autotrophs that co-work in the high-rate EGSB-SDD (simultaneous desulfurization and denitrification)
reactor. 相似文献
10.
FTIR-spectral analysis of two photosynthetic H2-producing strains and their extracellular polymeric substances 总被引:2,自引:0,他引:2
The Fourier transform infrared (FTIR) spectra of the cells of two photosynthetic H2-producing strains, Rhodoblastus acidophilus and Rhodobacter capsulatus, as well as their extracellular polymeric substances (EPS), were evaluated. The FTIR spectra of R.
capsulatus and its EPS during its cultivation were also recorded. The main peaks in the spectra, including 1,080 cm−1 (carbohydrates), 1,250 cm−1 (nucleic acids), 2,830–2,930 cm−1 (lipids), 1,660–1,535 cm−1 (Amide I and II of proteins), were observed. The relative heights of these peaks in the spectra of the two strains were different, showing the difference in contents of various components in the cells or EPS. The ratios among the main components in the EPS obtained from the FTIR spectra were in good agreement with those from a conventional quantitative chemical analysis. As an easy, rapid, and direct technique, the FTIR spectroscopy could be used to characterize the components and their relative contents of EPS of photosynthetic bacteria.An erratum to this article can be found at 相似文献
11.
Nitrifying granules cultivation in a sequencing batch reactor at a low organics-to-total nitrogen ratio in wastewater 总被引:4,自引:0,他引:4
It is possible to cultivate aerobic granular sludge at a low organic loading rate and organics-to-total nitrogen (COD/N) ratio
in wastewater in the reactor with typical geometry (height/diameter = 2.1, superficial air velocity = 6 mm/s). The noted nitrification
efficiency was very high (99%). At the highest applied ammonia load (0.3 ± 0.002 mg NH4+–N g total suspended solids (TSS)−1 day−1, COD/N = 1), the dominating oxidized form of nitrogen was nitrite. Despite a constant aeration in the reactor, denitrification
occurred in the structure of granules. Applied molecular techniques allowed the changes in the ammonia-oxidizing bacteria
(AOB) community in granular sludge to be tracked. The major factor influencing AOB number and species composition was ammonia
load. At the ammonia load of 0.3 ± 0.002 mg NH4+–N g TSS−1 day−1, a highly diverse AOB community covering bacteria belonging to both the Nitrosospira and Nitrosomonas genera accounted for ca. 40% of the total bacteria in the biomass. 相似文献
12.
Mannan Hajimahmoodi Mohammad Ali Faramarzi Najmeh Mohammadi Neda Soltani Mohammad Reza Oveisi Nastaran Nafissi-Varcheh 《Journal of applied phycology》2010,22(1):43-50
Antioxidant activities of both cells and extracellular substances were evaluated in 12 soil-isolated strains of microalgae
according to FRAP and DPPH-HPLC assays. Their total phenolic contents were also determined by Folin–Ciocalteu method. Extractions
were performed with hexane, ethyl acetate, and water. The results of FRAP assay showed that algal cells contained considerable
amounts of antioxidants from 0.56 ± 0.06 to 31.06 ± 4.00 μmol Trolox g−1 for Microchaete tenera hexane extract and Chlorella vulgaris water extract, respectively. In water fractions of extracellular substances, the antioxidants were from 1.30 ± 0.15 μmol
Trolox g−1 for Fischerella musicola to 73.20 ± 0.16 μmol Trolox g−1 for Fischerella ambigua. Also, DPPH-HPLC assay represented high antioxidant potential of water fractions. The measured radical-scavenging activities
of the studied microalgae were at least 0.15 ± 0.02 in Nostoc ellipsosporum cell mass to a maximum of 109.02 ± 8.25 in C. vulgaris extracellular substance. The amount of total phenolic contents varied in different strains of microalgae and ranged from
zero in hexane extract to 19.15 ± 0.04 mg GAE g−1 in C. vulgaris extracellular water fraction. Significant correlation coefficients between two measured parameters indicated that phenolic
compounds were a major contributor to the microalgal antioxidant capacities. 相似文献
13.
A 700 ml membrane-aerated, stirred glass reactor equipped with four vertical baffles was constructed. Biodesulfurization of
model oil (n-dodecane containing dibenzothiophene—DBT) and hydrodesulfurized diesel was carried out using Pseudomonas delafieldii strain R-8. Microbubble aeration gave an activity of 1.3 mg DBT removed g−1 h−1 and 277 μg sulfur g−1 h−1 for model oil and hydrodesulfurized diesel, respectively. These values were 1.9- and 1.6-times higher than using a traditional
bubble aeration process. This is a promising method for the biodesulfurization of petroleum feedstocks. 相似文献
14.
Enhanced nitrogen (N) levels accelerate expansion of Calamagrostis epigejos and Arrhenatherum elatius, highly aggressive expanders displacing original dry acidophilous grassland vegetation in the Podyjí National Park (Czech
Republic). We compared the capability of Calamagrostis and Arrhenatherum under control and N enhanced treatments to (i) accumulate N and phosphorus (P) in plant tissues, (ii) remove N and P from
above-ground biomass during senescence and (iii) release N and P from plant material during decomposition of fresh formed
litter. In control treatment, significantly higher amounts of total biomass and fresh aboveground litter were observed in
Calamagrostis than in Arrhenatherum. Contrariwise, nutrient concentrations were significantly higher (11.6–14.3 mg N g−1 and 2.3 mg P g−1) in Arrhenatherum peak aboveground biomass than in Calamagrostis (8.4–10.3 mg N g−1 and 1.6–1.7 mg P g−1). Substantial differences between species were found in resorption of nutrients, mainly P, at the ends of growing seasons.
While P concentrations in Arrhenatherum fresh litter were twice and three times higher (1.6–2.5 mg P g−1) than in Calamagrostis (0.7–0.8 mg P g−1), N concentrations were nearly doubled in Arrhenatherum (13.1–15.6 mg N g−1) in comparison with Calamagrostis (7.4–8.7 mg N g−1). Thus, the nutrients (N and mainly P) were retranslocated from the aboveground biomass of Calamagrostis probably more effectively in comparison with Arrhenatherum at the end of the growing season. On the other hand, Arrhenatherum litter was decomposed faster and consequently nutrient release (mainly N and P) was higher in comparison with Calamagrostis which pointed to different growth and nutrient use strategies of studied grass species. 相似文献
15.
Degrading high-strength phenol using aerobic granular sludge 总被引:1,自引:0,他引:1
Kuo-Ling Ho Yu-You Chen Bin Lin Duu-Jong Lee 《Applied microbiology and biotechnology》2010,85(6):2009-2015
Aerobic granules were adopted to degrade high-strength phenol wastewater in batch experiments. The acclimated granules effectively
degraded phenol at a concentration of up to 5,000 mg l−1 without severe inhibitory effects. The biodegradation of phenol by activated sludge was inhibited at phenol concentrations
>3,000 mg l−1. The granules were composed of cells embedded in a compact extracellular matrix. After acid or alkaline pretreatment, the
granules continued to degrade phenol at an acceptable rate. The polymerase chain reaction-denaturing gradient gel electrophoresis
technique was employed to monitor the microbial communities of the activated sludge and the aerobic granules following their
being used to treat high concentrations of phenol in batch tests. 相似文献
16.
The quantitative importance of photosynthetically produced dissolved organic carbon (PDOC) released from phytoplankton as
a source of carbon for pelagic, heterotrophic bacteria was investigated in four temperate Swedish lakes, of which two had
low (≈20 mg Pt 1−1), and two moderately high (60–80 mg Pt 1−1) humic content. The bacterial assimilation of PDOC was estimated with the 14C method, and the total production of the heterotrophic bacteria was estimated with the [3H]thymidine incorporation method.
The release of PDOC from natural communities of phytoplankton was not restricted to periods of photosynthesis, but often continued
during periods of darkness. Heterotrophic bacteria often assimilated the labile components of the PDOC at high rates (up to
73% of the released PDOC was assimilated during the incubation in our experiments). The contribution of PDOC to bacterial
production exhibited large within-lake seasonal variations, but PDOC was at certain times, both in humic and non-humic lakes,
a quantitatively very important carbon source for the heterotrophic bacteria. Under periods of comparatively low primary production,
heterotrophic bacteria in humic lakes appear to utilize allochthonous, humic substances as a substrate. 相似文献
17.
Effect of feed composition and upflow velocity on aggregate characteristics in anaerobic upflow reactors 总被引:4,自引:0,他引:4
V. O'Flaherty P. N. L. Lens D. de Beer E. Colleran 《Applied microbiology and biotechnology》1997,47(2):102-107
Two upflow anaerobic hybrid reactors treated lactose and a mixture of ethanol, propionate and butyrate, respectively, at
a volumetric loading rate of 3.7 kg chemical oxygen demand (COD) m−3day−1, a hydraulic retention time of 5 days and a liquid upflow velocity of 0.01 m/h. Under steady-state conditions, the lactose-fed
sludge had much higher (20%–100%) specific methanogenic conversion rates than the volatile-fatty acid␣(VFA)/ethanol-fed sludge
for all substrates tested, including VFA. In both reactors, a flocculant sludge developed, although a much higher content
of extracellular polysaccharide was measured in the lactose-fed sludge [1900 μg compared to 305 μg uronic acid/g volatile
suspended solids (VSS)]. When the liquid upflow velocity of a third, VFA/ethanol-fed reactor was increased to 0.5 m/h, granulation
of the sludge occurred, accompanied by a large increase (200%–500%) in the specific methanogenic conversion rates for the
syntrophic and methanogenic substrates studied. Granulation reduced the susceptibility of the sludge to flotation. Glucose
was degraded at a high rate (100 mg glucose gVSS−1h−1) by the sludge from the third reactor, despite not having been exposed to a sugar-containing influent for 563␣days.
Received: 7 June 1996 / Received revision: 23 September 1996 / Accepted: 29 September 1996 相似文献
18.
Enzyme activities in activated sludge flocs 总被引:9,自引:0,他引:9
This study quantified the activities of enzymes in extracellular polymeric substances (EPS) and in pellets. Seven commonly
adopted extraction schemes were utilized to extract from aerobic flocs the contained EPS, which were further categorized into
loosely bound (LB) and tightly bound (TB) fractions. Ultrasonication effectively extracted the EPS from sludge flocs. Enzyme
assay tests showed that the protease activity was localized mainly on the pellets, α-amylase and α-glucosidase activities
were largely bound with LB-EPS, and few protease, α-amylase, or α-glucosidase activities were associated with the TB-EPS fraction.
There exists no correlation between the biochemical compositions of EPS and the distribution of enzyme activities in the sludge
matrix. The 44–65% of α-amylase and 59–100% of α-glucosidase activities noted with the LB-EPS indicate heterogeneous hydrolysis
patterns in the sludge flocs with proteins and carbohydrates. 相似文献
19.
The main goal of this research was to investigate how different factors influence membrane fouling. The impact of the different concentrations of activated sludge and the amount of extracellular polymer substances (EPS) were monitored. Two pilot plants with submerged membrane modules (hollow fiber and flat sheet) were operated and the raw wastewater was used.Humic substances were identified as the major components of EPS in the activated sludge (more than 34%) in both pilot plants. As the basic constituent in permeate, humic substances were identified as the most dominant components in the effluent (61%) in both pilot plants. Conversely, proteins were mostly analyzed in permeate and supernatant below the detection limit. The total amount of EPS [mg g−1 (VSS)] was similar for concentrations of activated sludge 6, 10 and 14 g L−1. Carbohydrates were identified as the component of EPS which tends most to clog membranes. 相似文献
20.
To investigate the nutritional value of the diatom Cyclotella cryptica as an alternative feed for aquaculture, its heterotrophic growth characteristics were studied. First, the proximate biochemical
composition and fatty acid profiles were studied under a controlled heterotrophic growth condition. The approximate total
ash, carbohydrate, lipid, and protein content were 245 mg g−1 (dry weight), 360 mg g−1, 165 mg g−1 and 260 mg g−1, respectively. Polyunsaturated fatty acids accounted for 24.5, 31.3, 45.1 and 17.3% of the total lipids in the phospholipid,
sterol, free fatty acid and triglyceride classes. Secondly, the effect of aeration and agitation rates on the specific growth
rate of C. cryptica under heterotrophic conditions was studied. The maximum specific growth rate was not significantly affected (P > 0.05) by the rate of agitation within the range of 100 to 160 rpm, but it was significantly affected (P > 0.05) by the rate of aeration. Optimal growth occurred when the aeration rate was within the range of 0.44 to 1.07 v/v/min. Viability measurements throughout the growth period showed that the C. cryptica cells remained viable in spite of the varied cultivation conditions. Hydrodynamic forces are an important parameter within
biological systems, and optimisation is crucial for the successful scale-up of microalgal cultivation systems. Whilst the
investigation was preliminary in nature, the information gained in this study will be useful for the continual development
of an alternative and cost-effective feed for bivalve spat rations. 相似文献