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1.
Shigematsu T Era S Mizuno Y Ninomiya K Kamegawa Y Morimura S Kida K 《Applied microbiology and biotechnology》2006,72(2):401-415
Abstract
We constructed a mesophilic anaerobic chemostat that was continuously
fed with synthetic wastewater containing propionate as the sole source
of carbon and energy. Steady-state conditions were achieved below the
critical dilution rate of 0.3 d
−1
with almost complete substrate degradation. The propionate-degrading
methanogenic communities in the chemostat at dilution rates of 0.01,
0.08, and 0.3 d
−1
were analyzed using molecular biological techniques. Fluorescence in
situ hybridization with archaeal and bacterial domain-specific probes
showed that archaeal cells predominated throughout the three dilution
rates. Archaeal-16S rRNA gene clone library analysis and quantitative
real-time polymerase chain reaction studies showed that hydrogenotrophic
methanogen rRNA genes closely related to
Methanoculleus
was detected at a dilution rate of 0.01 d
−1
, whereas rRNA genes closely related to the
Methanoculleus
and
Methanospirillum
genera were detected at dilution rates of 0.08 and 0.3 d
−1
. The aceticlastic methanogen,
Methanosaeta
, was detected throughout the three dilution rates. Bacterial-rRNA gene
clone library analysis and denaturing gradient gel electrophoresis
demonstrated that rRNA genes affiliated with the genus
Syntrophobacter
predominated at the low dilution rate, whereas rRNA genes affiliated
with the phylum
Firmicutes
predominated at the higher dilution rates. A significant number of rRNA
genes affiliated with the genus
Pelotomaculum
were detected at dilution rate of 0.3 d
−1
. The diversity of genes encoding acetate kinase agreed closely with the
results of the rRNA gene analysis. The dilution rates significantly
altered the archaeal and bacterial communities in the propionate-fed
chemostat. 相似文献
2.
Dynamic Transition of a Methanogenic Population in Response to the Concentration of Volatile Fatty Acids in a Thermophilic Anaerobic Digester 总被引:4,自引:1,他引:4
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Tomoyuki Hori Shin Haruta Yoshiyuki Ueno Masaharu Ishii Yasuo Igarashi 《Applied microbiology》2006,72(2):1623-1630
In this study, the microbial community succession in a thermophilic methanogenic bioreactor under deteriorative and stable conditions that were induced by acidification and neutralization, respectively, was investigated using PCR-mediated single-strand conformation polymorphism (SSCP) based on the 16S rRNA gene, quantitative PCR, and fluorescence in situ hybridization (FISH). The SSCP analysis indicated that the archaeal community structure was closely correlated with the volatile fatty acid (VFA) concentration, while the bacterial population was impacted by pH. The archaeal community consisted mainly of two species of hydrogenotrophic methanogen (i.e., a Methanoculleus sp. and a Methanothermobacter sp.) and one species of aceticlastic methanogen (i.e., a Methanosarcina sp.). The quantitative PCR of the 16S rRNA gene from each methanogen revealed that the Methanoculleus sp. predominated among the methanogens during operation under stable conditions in the absence of VFAs. Accumulation of VFAs induced a dynamic transition of hydrogenotrophic methanogens, and in particular, a drastic change (i.e., an approximately 10,000-fold increase) in the amount of the 16S rRNA gene from the Methanothermobacter sp. The predominance of the one species of hydrogenotrophic methanogen was replaced by that of the other in response to the VFA concentration, suggesting that the dissolved hydrogen concentration played a decisive role in the predominance. The hydrogenotrophic methanogens existed close to bacteria in aggregates, and a transition of the associated bacteria was also observed by FISH analyses. The degradation of acetate accumulated during operation under deteriorative conditions was concomitant with the selective proliferation of the Methanosarcina sp., indicating effective acetate degradation by the aceticlastic methanogen. The simple methanogenic population in the thermophilic anaerobic digester significantly responded to the environmental conditions, especially to the concentration of VFAs. 相似文献
3.
4.
A psychrotolerant microbial consortium from a low-temperature anaerobic EGSB bioreactor was grown separately on acetate, propionate,
butyrate, and H2/CO2 at 30 and 10°C in glass flasks. In the course of the experiments, the cultivation temperature was changed at different time
intervals. The initial rates of substrate utilization were higher at 30 than at 10°C. However, the microbial consortium was
found to be well adapted to low temperatures; when grown at 10°C for 1.5–5 months, the rates of butyrate, propionate, and
H2/CO2 utilization increased steadily. When grown at 30°C for 1.5–2.5 months, this consortium retained its ability to degrade VFA
and H2/CO2 at 10°C. However, after long-term (150 days) cultivation at 10°C, its ability to utilize the substrates at 30°C decreased.
In the consortium grown in the acetate-containing medium, a Methanosaeta-like methanogen was predominant; in media with propionate and butyrate, besides VFA-degrading bacteria, acetoclastic Methanosaeta-like and hydrogenotrophic Methanospirillum-like methanogenic archaea prevailed. A Methanospirillum-like strain predominated in the H2/CO2-containing medium. The Methanospirillum strain of this microbial community was presumably psychrotolerant. A method based on changes in the cultivation temperature
is of practical interest and can be used to start up new bioreactors. 相似文献
5.
Juho So Krishna R. Pagilla Hyungjin Kim Benjamin C. Stark 《Biotechnology and Bioprocess Engineering》1999,4(3):176-180
The gene (vgb) encoding the hemoglobin (VHb) ofVitreoscilla sp. was cloned intoBurkholderia sp. and the effect of VHb on the growth characteristics of genetically engineeredBurkholderia (YV1) were compared with wild typeBurkholderia (R34) using continuous flow reactors (chemostat) at various dilution rates under aerobic conditions. Batch oxygen uptake
rate showed that YV1 has much higher oxygen uptake rate than R34 (i.e. 0.63 mg O2/g biomass/min vs. 1.43 mg O2/g biomass/min for R34 and YV1 respectively at a dilution rate of 1.2 day−1). Monod parameters, maximum growth rate (μmax) and half saturation coefficient (Ks) were found to be 7.03 day−1 and 691 mg/L for R34 respectively, compared to 5.49 day−1 and 404 mg/L for YV1 respectively. At low dilution rates (<2.5 day−1), when the substrate is present in low concentrations, the growth yield was much higher in YV1 (0.52) than in R34 (0.37).
Although substrate utilization rates were similar between R34 and YV1, the latter showed much higher oxygen uptake rate than
did R34 at all dilution rates. When the stability of VHb was tested on agar plates containing 40 μg/L of kanamycin and 100
μg/L of ampicillin,vgb gene containing VHb plasmid in YV1 was stable over 82 days. When survivability under oxygen limited conditions was tested,
R34 survived only for 11 days whereas YV1 survived over 25 days in liquid media; in agar plate experiments, R34 did not survive
more than 40 days whereas more than 75% of YV1 survived over 110 days. 相似文献
6.
Bacteria and archaea involved in anaerobic digestion of distillers grains with solubles 总被引:1,自引:0,他引:1
Ziganshin AM Schmidt T Scholwin F Il'inskaya ON Harms H Kleinsteuber S 《Applied microbiology and biotechnology》2011,89(6):2039-2052
Cereal distillers grains, a by-product from bioethanol industry, proved to be a suitable feedstock for biogas production in
laboratory scale anaerobic digesters. Five continuously stirred tank reactors were run under constant conditions and monitored
for biogas production and composition along with other process parameters. Iron additives for sulfide precipitation significantly
improved the process stability and efficiency, whereas aerobic pretreatment of the grains had no effect. The microbial communities
in the reactors were investigated for their phylogenetic composition by terminal restriction fragment length polymorphism
analysis and sequencing of 16S rRNA genes. The bacterial subcommunities were highly diverse, and their composition did not
show any correlation with reactor performance. The dominant phylotypes were affiliated to the Bacteroidetes. The archaeal
subcommunities were less diverse and correlated with the reactor performance. The well-performing reactors operated at lower
organic loading rates and amended with iron chloride were dominated by aceticlastic methanogens of the genus Methanosaeta. The well-performing reactor operated at a high organic loading rate and supplemented with iron hydroxide was dominated by
Methanosarcina ssp. The reactor without iron additives was characterized by propionate and acetate accumulation and high hydrogen sulfide
content and was dominated by hydrogenotrophic methanogens of the genus Methanoculleus. 相似文献
7.
This study was conducted to analyze the methanogen population in a corrosive marine biofilm based on 16S rDNA analysis, using a PCR-cloning-sequencing approach. There were 80 methanogen clones developed from the PCR-amplified DNA extracted from the biofilm on the mild steel surface. All clones were categorized into one of five operational taxonomy units (OTUs). Two OTUs (comprising 57 clones) were affiliated with the acetotrophic Methanosaeta genus; the remaining three OTUs (23 clones) were affiliated with the hydrogenotrophic genera of Methanogenium, Methanoplanus and Methanocalculus. The hydrogenotrophic methanogens could directly cause metal corrosion through cathodic depolarization, whereas the acetotrophic methanogens grew syntrophically with corrosion-causing sulfate-reducing bacteria, as observed by fluorescent in situ hybridization, and thus contribute indirectly to metal corrosion. 相似文献
8.
Sánchez Fernández JF González-López CV Acién Fernández FG Fernández Sevilla JM Molina Grima E 《Applied microbiology and biotechnology》2012,94(3):613-624
This paper focuses on modelling the growth rate and exopolysaccharides production of Anabaena sp. ATCC 33047, to be used in carbon dioxide removal and biofuels production. For this, the influence of dilution rate, irradiance
and aeration rate on the biomass and exopolysaccharides productivity, as well as on the CO2 fixation rate, have been studied. The productivity of the cultures was maximum at the highest irradiance and dilution rate
assayed, resulting to 0.5 gbio l−1 day−1 and 0.2 geps l−1 day−1, and the CO2 fixation rate measured was 1.0 gCO2 l−1 day−1. The results showed that although Anabaena sp. was partially photo-inhibited at irradiances higher than 1,300 μE m−2 s−1, its growth rate increases hyperbolically with the average irradiance inside the culture, and so does the specific exopolysaccharides
production rate. The latter, on the other hand, decreases under high external irradiances, indicating that the exopolysaccharides
metabolism hindered by photo-damage. Mathematical models that consider these phenomena have been proposed. Regarding aeration,
the yield of the cultures decreased at rates over 0.5 v/v/min or when shear rates were higher than 60 s−1, demonstrating the existence of thus existence of stress damage by aeration. The behaviour of the cultures has been verified
outdoors in a pilot-scale airlift tubular photobioreactor. From this study it is concluded that Anabaena sp. is highly recommended to transform CO2 into valuable products as has been proved capable of metabolizing carbon dioxide at rates of 1.2 gCO2 l−1 day−1 outdoors. The adequacy of the proposed equations is demonstrated, resulting to a useful tool in the design and operation
of photobioreactors using this strain. 相似文献
9.
Extracellular human granulocyte-macrophage colony stimulating factor (hGM-CSF) expression was studied under the control of
the GAP promoter in recombinant Pichia pastoris in a series of continuous culture runs (dilution rates from 0.025 to 0.2 h−1). The inlet feed concentration was also varied and the steady state biomass concentration increased proportionally demonstrating
efficient substrate utilization and constancy of the biomass yield coefficient (Yx/s) for a given dilution rate. The specific product formation rate (qP) showed a strong correlation with dilution rates demonstrating growth associated product formation of hGM-CSF. The volumetric
product concentration achieved at the highest feed concentration (4×) and a dilution rate of 0.2 h−1 was 82 mg l−1 which was 5-fold higher compared to the continuous culture run with 1× feed concentration at the lowest dilution rate thus
translating to a 40 fold increase in the volumetric productivity. The specific product yield (YP/X) increased slightly from 2 to 2.5 mg g−1, with increasing dilution rates, while it remained fairly invariant, for all feed concentrations demonstrating negligible
product degradation or feed back inhibition. The robust nature of this expression system would make it easily amenable to
scale up for industrial production. 相似文献
10.
Zamalloa C De Vrieze J Boon N Verstraete W 《Applied microbiology and biotechnology》2012,93(2):859-869
The biomass of industrially grown Phaeodactylum tricornutum was subjected in a novel way to bio-methanation at 33°C, i.e., in an anaerobic membrane bioreactor (AnMBR) at a hydraulic
retention time of 2.5 days, at solid retention times of 20 to 10 days and at loading rates in the range of 2.6–5.9 g biomass-COD L−1 day−1 with membrane fluxes ranging from 1 to 0.8 L m−2 h−1. The total COD recovered as biogas was in the order of 52%. The input suspension was converted to a clear effluent rich in
total ammonium nitrogen (546 mg TAN L−1) and phosphate (141 mg PO4-P L−1) usable as liquid fertilizer. The microbial community richness, dynamics, and organization in the reactor were interpreted
using the microbial resource management approach. The AnMBR communities were found to be moderate in species richness and
low in dynamics and community organization relative to UASB and conventional CSTR sludges. Quantitative polymerase chain reaction
analysis revealed that Methanosaeta sp. was the dominant acetoclastic methanogen species followed by Methanosarcina sp. This work demonstrated that the use of AnMBR for the digestion of algal biomass is possible. The fact that some 50% of
the organic matter is not liquefied means that the algal particulates in the digestate constitute a considerable fraction
which should be valorized properly, for instance as slow release organic fertilizer. Overall, 1 kg of algae dry matter (DM)
could be valorized in the form of biogas (€2.07), N and P in the effluent (€0.02) and N and P in the digestate (€0.04), thus
totaling about €2.13 per kilogram algae DM. 相似文献
11.
Microbial community structure in anaerobic co-digestion of grass silage and cow manure in a laboratory continuously stirred tank reactor 总被引:1,自引:0,他引:1
Hong Wang Katariina Tolvanen Annimari Lehtomäki Jaakko Puhakka Jukka Rintala 《Biodegradation》2010,21(1):135-146
The impacts of feeding ratio and loading rate on the microbial community during co-digestion of grass silage with cow manure
in an anaerobic laboratory continuously stirred tank reactor were investigated by 16S rRNA gene-based fingerprints. The microbial
community remained stable when the reactor was fed with cow manure alone and with up to 20% of grass silage in feedstock at
an organic loading rate (OLR) of 2 kg VS m−3 day−1. Large changes in the bacterial community were observed when the loading ratio of grass was increased to 40%, while there
was little change in the archaeal community. During the increase in OLR from 2 to 4 kg VS m−3 day−1 the bacterial community structure showed few differences, whereas Archaea was undetectable. Sequencing of the major DGGE bands indicated that the phylum Bacteriodetes predominated in the bacterial community. Two unclassified bacteria with high abundance survived throughout the operation
of the reactor. 相似文献
12.
Enrichment of Thermophilic Propionate-Oxidizing Bacteria in Syntrophy with Methanobacterium thermoautotrophicum or Methanobacterium thermoformicicum 总被引:7,自引:5,他引:2
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Alfons J. M. Stams Katja C. F. Grolle Carla T. M. Frijters Jules B. Van Lier 《Applied microbiology》1992,58(1):346-352
Thermophilic propionate-oxidizing, proton-reducing bacteria were enriched from the granular methanogenic sludge of a bench-scale upflow anaerobic sludge bed reactor operated at 55°C with a mixture of volatile fatty acids as feed. Thermophilic hydrogenotrophic methanogens had a high decay rate. Therefore, stable, thermophilic propionate-oxidizing cultures could not be obtained by using the usual enrichment procedures. Stable and reproducible cultivation was possible by enrichment in hydrogen-pregrown cultures of Methanobacterium thermoautotrophicum ΔH which were embedded in precipitates of FeS, achieved by addition of FeCl2 to the media. The propionate-oxidizing bacteria formed spores which resisted pasteurization for 30 min at 90°C or 10 min at 100°C. Highly purified cultures were obtained with either M. thermoautotrophicum ΔH or Methanobacterium thermoformicicum Z245 as the syntrophic partner organism. The optimum temperature for the two cultures was 55°C. Maximum specific growth rates of cultures with M. thermoautotrophicum ΔH were somewhat lower than those of cultures with M. thermoformicicum Z245 (0.15 and 0.19 day-1, respectively). Growth rates were even higher (0.32 day-1) when aceticlastic methanogens were present as well. M. thermoautotrophicum ΔH is an obligately hydrogen-utilizing methanogen, showing that interspecies hydrogen transfer is the mechanism by which reducing equivalents are channelled from the acetogens to this methanogen. Boundaries of hydrogen partial pressures at which propionate oxidation occurred were between 6 and 34 Pa. Formate had a strong inhibitory effect on propionate oxidation in cultures with M. thermoautotrophicum. Inhibition by formate was neutralized by addition of the formate-utilizing methanogen or by addition of fumarate. Results indicate that formate inhibited succinate oxidation to fumarate, an intermediate step in the biochemical pathway of propionate oxidation. 相似文献
13.
Hydrogen production with high yield and high evolution rate by self-flocculated cells of Enterobacter aerogenes in a packed-bed reactor 总被引:6,自引:1,他引:5
M. A. Rachman Y. Nakashimada T. Kakizono N. Nishio 《Applied microbiology and biotechnology》1998,49(4):450-454
Continuous hydrogen gas evolution by self-flocculated cells of Enterobacter aerogenes, a natural isolate HU-101 and its mutant AY-2, was performed in a packed-bed reactor under glucose-limiting conditions in
a minimal medium. The flocs that formed during the continuous culture were retained even when the dilution rate was increased
to 0.9 h−1. The H2 production rate increased linearly with increases in the dilution rate up to 0.67 h−1, giving maximum H2 production rates of 31 and 58 mmol l−1 h−1 in HU-101 and AY-2 respectively, at a dilution rate of more than 0.67 h−1. The molar H2 yield from glucose in AY-2 was maintained at about 1.1 at dilution rates between 0.08 h−1 and 0.67 h−1, but it decreased rapidly at dilution rates more than 0.8 h−1.
Received: 27 August 1997 / Received revision: 11 November 1997 / Accepted: 14 December 1997 相似文献
14.
The effects of seasonality and dilution stress on the functioning of Rambla Salada, a hypersaline Mediterranean stream in
SE Spain, were evaluated. The stream is subject to diffuse freshwater inputs from the drainage of intensively irrigated agriculture
in the catchment and periodic losses of water through an irrigation channel. Metabolic rates and the biomass of primary producers
and consumers were estimated over a 2-year period. During the first year several dilution events occurred, while during the
second year the salinity recovery reached predisturbance levels. Functional indicators were compared in the disturbance and
recovery salinity periods. Primary production and respiration rates in the Rambla Salada ranged between 0.07–21.05 and 0.19–17.39 g
O2 m−2 day−1, respectively. The mean values for these variables were 7.35 and 5.48 g O2 m−2 day−1, respectively. Mean net daily metabolism rate was 1.87 ± 0.52 g O2 m−2 day−1 and mean production/respiration ratio was 2.48 ± 1.1, reflecting autotrophic metabolism. The metabolic rates showed the typical
seasonal pattern of Mediterranean open canopy streams. Therefore, gross primary production (GPP) and ecosystem respiration
(ER) registered maximum values in summer, intermediate values in spring and autumn and minimum values in winter. The metabolic
rates and biomass of consumers were greater in the disturbance period than in the recovery period. However, they did not show
significant differences between periods due to their important dependence on seasonal cycle. Seasonality accounted for much
of the temporal variability in GPP and ER (76% and 83% in the multiregression models, respectively). Light availability seems
to be the most important factor for GPP and ER in the Rambla Salada. Autotrophic biomass responded more to variations in discharge
and conductivity than to seasonal variations. In fact, it was severely affected by freshwater inputs after which the epipelic
biomass decreased significantly and Cladophora glomerata proliferated rapidly. Epipelic algal biomass was the most sensitive parameter to dilution disturbance.
Handling editor: Luigi Naselli-Flores 相似文献
15.
Fish <1 year old were sampled during 1 year using nets inshore at South Georgia. Some fish were kept in aquaria. Growth rates
were estimated using the exponential model. During June to October 1980, field growth rates of Parachaenichthys georgianus and Champsocephalus gunnari were 0.33 and 0.48% SL day−1, respectively. Gobionotothen marionensis (1979 cohort) grew at 0.40% SL day−1 during June to November in the field, and 0.34% SL day−1 in the laboratory from September to March. Notothenia coriiceps grew at 0.28% SL day−1 in the laboratory during September to March. During November to December, Artedidraco mirus grew at 0.82% SL day−1 in the field. The 1980 cohort of G. marionensis grew at 1.39% SL day−1 during November to January in the field. During January, the field growth rate of G. gibberifrons was 1.39% SL day−1. Growth rates increased three-fold from winter to summer. Temperature can only explain one-half of this range in growth rates,
whereas all of this range can be explained by food availability. Therefore, seasonal food resource limitation has a major
effect on Antarctic fish growth.
Received: 30 June 1997 / Accepted: 7 September 1997 相似文献
16.
Vavilin VA Qu X Mazéas L Lemunier M Duquennoi C He P Bouchez T 《Antonie van Leeuwenhoek》2008,94(4):593-605
Taking into account isotope 13C value a mathematical model was developed to describe the dynamics of methanogenic population during mesophilic anaerobic
digestion of putrescible solid waste and waste imitating Chinese municipal solid waste. Three groups of methanogens were considered
in the model including unified hydrogenotrophic methanogens and two aceticlastic methanogens Methanosaeta sp. and Methanosarcina sp. It was assumed that Methanosaeta sp. and Methanosarcina sp. are inhibited by high volatile fatty acids concentration. The total organic and inorganic carbon concentrations, methane
production, methane and carbon dioxide partial pressures as well as the isotope 13C incorporation in PSW and CMSW were used for the model calibration and validation. The model showed that in spite of the
high initial biomass concentration of Methanosaeta sp. Methanosarcina sp. became the dominant aceticlastic methanogens in the system. This prediction was confirmed by FISH. It is concluded that
Methanosarcina sp. forming multicellular aggregates may resist to inhibition by volatile fatty acids (VFAs) because a slow diffusion rate
of the acids limits the VFA concentrations inside the Methanosarcina sp. aggregates. 相似文献
17.
Robert G. Björk Leif Klemedtsson Ulf Molau Jan Harndorf Anja Ödman Reiner Giesler 《Plant and Soil》2007,294(1-2):247-261
The spatial distribution of organic soil nitrogen (N) in alpine tundra was studied along a natural environmental gradient,
covering five plant communities, at the Latnjajaure Field Station, northern Swedish Lapland. The five communities (mesic meadow,
meadow snowbed, dry heath, mesic heath, and heath snowbed) are the dominant types in this region and are differentiated by
soil pH. Net N mineralization, net ammonification, and net nitrification were measured using 40-day laboratory incubations
based on extractable NH4+ and NO3−. Nitrification enzyme activity (NEA), denitrification enzyme activity (DEA), amino acid concentrations, and microbial respiration
were measured for soils from each plant community. The results show that net N mineralization rates were more than three times
higher in the meadow ecosystems (mesic meadow 0.7 μg N g−1 OM day−1 and meadow snowbed 0.6 μg N g−1 OM day−1) than the heath ecosystems (dry heath 0.2 μg N g−1 OM day−1, mesic heath 0.1 μg N g−1 OM day−1 and heath snowbed 0.2 μg N g−1 OM day−1). The net N mineralization rates were negatively correlated to organic soil C/N ratio (r = −0.652, P < 0.001) and positively correlated to soil pH (r = 0.701, P < 0.001). Net nitrification, inorganic N concentrations, and NEA rates also differed between plant communities; the values
for the mesic meadow were at least four times higher than the other plant communities, and the snowbeds formed an intermediate
group. Moreover, the results show a different pattern of distribution for individual amino acids across the plant communities,
with snowbeds tending to have the highest amino acid N concentrations. The differences between plant communities along this
natural gradient also illustrate variations between the dominant mycorrhizal associations in facilitating N capture by the
characteristic functional groups of plants.
Responsible Editor: Bernard Nicolardot 相似文献
18.
Seungyong Lee Bowon Lee Gyuseong Han Heechul Yoon 《Bioscience, biotechnology, and biochemistry》2013,77(8):1378-1383
In this study, dual-cylindrical anaerobic digesters were designed and built on the pilot plant scale for the improvement of anaerobic digestion efficiency. The removal efficiency of organics, biogas productivity, yield, and microbial communities was evaluated as performance parameters of the digester. During the stable operational period in the continuous mode, the removal efficiencies of chemical oxygen demand and total solids were 74.1 and 65.1%, respectively. Biogas productivities of 63.9 m3/m3-FWW and 1.3 m3/kg-VSremoved were measured. The hydrogenotrophic methanogen orders, Methanomicrobiales and Methanobacteriales, were predominant over the aceticlastic methanogen order, Methanosarcinaceae, probably due to the tolerance of the hydrogenotrophs to environmental perturbation in the field and their faster growth rate compared with that of the aceticlastics. 相似文献
19.
Kaarel Adamberg Petri-Jaan Lahtvee Kaspar Valgepea Kristo Abner Raivo Vilu 《Antonie van Leeuwenhoek》2009,95(3):219-226
Quasi steady state growth of Lactococcus
lactis IL 1403 was studied in glucose-limited A-stat cultivation experiments with acceleration rates (a) from 0.003 to 0.06 h−2 after initial stabilization of the cultures in chemostat at D = 0.2–0.3 h−1. It was shown that the high limit of quasi steady state growth rate depended on the acceleration rate used—at an acceleration
rate 0.003 h−2 the quasi steady state growth was observed until μ
crit = 0.59 h−1, which is also the μ
max value for the culture. Lower values of μ
crit were observed at higher acceleration rates. The steady state growth of bacteria stabilized at dilution rate 0.2 h−1 was immediately disrupted after initiating acceleration at the highest acceleration rate studied—0.06 h−2. Observation was made that differences [Δ(μ − D)] of the specific growth rates from pre-programmed dilution rates were the lowest using an acceleration rate of 0.003 h−2 (< 4% of preset changing growth rate). The adaptability of cells to follow preprogrammed growth rate was found to decrease
with increasing dilution rate—it was shown that lower acceleration rates should be applied at higher growth rates to maintain
the culture in the quasi steady state. The critical specific growth rate and the biomass yields based on glucose consumption
were higher if the medium contained S
0 = 5 g L−1 glucose instead of S
0 = 10 g L−1. It was assumed that this was due to the inhibitory effect of lactate accumulating at higher concentrations in the latter
cultures. Parallel A-stat experiments at the same acceleration and dilution rates showed good reproducibility—Δ(μ − D) was less than 5%, standard deviations of biomass yields per ATP produced (Y
ATP), and biomass yields per glucose consumed (Y
XS) were less than 15%. 相似文献
20.
Kanesa May Duncan 《Environmental Biology of Fishes》2006,76(2-4):139-149
Juvenile scalloped hammerhead sharks, Sphyrna lewini, are apex predators within their nursery ground in Kāne‘ohe Bay, Ō‘ahu, Hawai‘i. Understanding daily maintenance requirements of a top-level predator is an important step toward understanding its ecological impact within a nursery ecosystem. Juvenile S. lewini were fed a range of daily ration levels to examine the effect of feeding rate on growth and gross conversion efficiency. The von Bertalanffy growth model yielded the best fit to the data, predicting a maintenance ration of 115 kJ kg−1 day−1 (3.4% body weight (BW) day−1) and a maximum growth rate of 38 kJ kg−1 day−1. This finding is in agreement with the previous prediction of high energetic requirements for S. lewini. In combination with the hypothesized food limitation within Kāne‘ohe Bay, this result may explain the observed high mortality rates of S. lewini. Gross conversion efficiency, K
1, ranged from −36% to 34%, with maximum efficiency at feeding levels of 5.1% BW day−1. The growth conversion efficiency of S.␣lewini is similar to that of lemon sharks and teleost fishes. Growth rates of juvenile S. lewini are possibly restricted by their high metabolic rate, limited food availability and foraging inexperience. By directly examining the effect of ration size on growth and food conversion, it was possible to resolve discrepancies between earlier studies, which used respiratory metabolism and gut content analyses. 相似文献