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1.
Conversion of organic wastes to syngas is an attractive way to utilize wastes. The produced syngas can be further used to produce a variety of chemicals. In this study, a hollow-fiber membrane biofilm reactor with mix cultures was operated at 55 °C to convert syngas (H2/CO2) into acetate. A high concentration of acetate (42.4 g/L) was reached in batch experiment while a maximum acetate production rate of 10.5 g/L/day was achieved in the continuous-flow mode at hydraulic retention time (HRT) of 1 day. Acetate was the main product in both batch and continuous-flow experiments. n-Butyrate was the other byproduct in the reactor. Acetate accounted for more than 98.5 and 99.1% of total volatile fatty acids in batch and continuous modes, respectively. Illumina Miseq high-throughput sequencing results showed that microorganisms were highly purified and enriched in the reactor. The main genus was Thermoanaerobacterium (66% of relative abundance), which was usually considered as H2 producer in the literature, however, likely played a role as a H2 consumer in this study. This study provides a new method to generate the high producing rate and purity of acetate from syngas. 相似文献
2.
Summary
Aspergillus terreus NRRL 1960 was grown on porous disks rotating intermittently in and out of the liquid phase. This immobilized fungal cell bioreactor was used to produce itaconic acid from glucose in a continuous operation. The effect of temperature, pH, disk rotation speed, and feed rate on the itaconic acid concentration and volumetric productivity were studied. The highest itaconic acid concentration and volumetric productivity obtained were 18.2 g/l and 0.73 g/l·h, respectively, under the following conditions: temperature at 36°C, pH 3.0, disk rotation speed at 8 rpm, and feed rate at 60 ml/h. These results are better than those by conventional fermentation or by other immobilized method.Nomenclature
F
feed rate (l/h)
-
K
1s
saturation constant for immobilized cells (g/l)
-
K
2s
saturation constant for suspended cells (g/l)
-
M
1
increased mass of immobilized cells (g)
-
M
2
total mass of immobilized cells (g)
-
P
concentration of itaconic acid (g/l)
-
S
substrate concentration in and out of the reactor (g/l)
-
S
0
substrate concentration in the feed (g/l)
-
V
liquid volume of the reactor (1)
-
X
concentration of the suspended cells (g/l)
-
Y
1
apparent yield of the immobilized cells (g cells/g substrate)
-
Y
2
apparent yield of the suspended cells (g cell/g substrate)
-
Y
3
apparent yield of itaconic acid (g itaconic acid/g substrate)
-
m
1
maintenance and by-products coefficient of the immobilized cells (g substrate/g cell·h)
-
m
2
maintenance and by-products coefficient of the suspended cells (g substrate/g cell·h)
- µ 1max
maximum specific growth rate of the immobilized cells (h -1)
- µ 2max
maximum specific growth rate of the suspended cells (h -1) 相似文献
3.
A reactor-scale hydrogen (H 2) production via the water-gas shift reaction of carbon monoxide (CO) and water was studied using the purple nonsulfur bacterium, Rhodopseudomonas palustris P4. The experiment was conducted in a two-step process: an aerobic/chemoheterotrophic cell growth step and a subsequent anaerobic
H 2 production step. Important parameters investigated included the agitation speed, inlet CO concentration and gas retention
time. P4 showed a stable H 2 production capability with a maximum activity of 41 mmol H 2 g cell −1h −1 during the continuous reactor operation of 400 h. The maximal volumetric H 2 production rate was estimated to be 41 mmol H 2 L 1h −1, which was about nine-fold and fifteen-fold higher than the rates reported for the photosynthetic bacteria Rhodospirillum rubrum and Rubrivivax gelatinosus, respectively. This is mainly attributed to the ability of P4 to grow to a high cell density with a high specific H 2 production activity. This study indicates that P4 has an outstanding potential for a continuous H 2 production via the water-gas shift reaction once a proper bioreactor system that provides a high rate of gas-liquid mass transfer is developed. 相似文献
4.
In this study, (S)-3-hydroxy-3-phenylpropionate was prepared continuously by coupling microbial transformation and membrane
separation. The effect of several factors on membrane flux, reactor capacity, and reaction conversion were investigated. A
kinetic model of the continuous reduction process was also developed. The appropriate molecular weight cut-off of the ultrafiltration
membrane was 30 kDa. The reactor capacity reached a maximum of 0.136/h at a biomass concentration and membrane flux of 86
g/L (dry weight/reaction volume) and 20 mL/h, respectively. The (S)-3-hydroxy-3-phenylpropionate yield was 3.68 mmol/L/day
after continuous reduction over seven days. The enantiometric excess of (S)-3-hydroxy-3-phenylpropionate reached above 99.5%.
The kinetic constants of continuous reduction were as follows: r
m = 3.00 × 10 −3 mol/L/h, k
cat = 3.49 × 10 −4 mol/L/h, k
1 = 3.09 × 10 −2 mol/L, and k
2 = 5.00 × 10 −7 mol/L. The kinetic model was in good agreement with the experimental data obtained during continuous reduction. Compared
with batch reduction, continuous reduction can significantly improve the catalytic efficiency of microbial cells and increase
the reactor capacity. 相似文献
5.
This research for the first time investigated hydrogen production from the fresh leachate originated from municipal solid wastes. We found that fermentation of the leachate generated H 2 and was very much enhanced in the presence of extra phosphate in the batch reactor. The continuous expanded granular sludge bed (EGSB) reactor started to generate H 2 at day 20 and continued to 176 days with 120 mg/l of extra phosphate present. The highest chemical oxygen demand (COD) removal efficiency (66.9%) was achieved at liquid up-flow velocity of 3.7 m/h and hydraulic retention time of 12 h. Under proposed optimal operation conditions, the mean H 2 production rate reached up to 2155 ml/(l day). We also found that over 80% liquid metabolites were acetic acid and ethanol, suggesting the ethanol-type fermentation was dominant in the bioreactor. These findings indicate that the fresh leachate can be used as the source for continuous hydrogen production. 相似文献
6.
When the partial pressure of H 2 was decreased by lowering the total pressure in the headspace of the reactor in a batch fermentation process from 760 mm
Hg to 380 mm Hg containing Enterobacter cloacae, the molar yield of H 2 increased from 1.9 mol to 3.9 mol H 2/mol glucose. The maximum production rate was 0.017 mmol H 2/h l at 380 mm Hg. The lag period as well as total batch time of H 2 production decreased using a decreased partial pressure. 相似文献
7.
Peptostreptococcus productus ATCC35244, a reductive acetogenic strain, was added daily over 9 successive days to the fourth vessel (ascending colon) of
the SHIME, a six-stage reactor system simulating the in vivo continuous culture conditions of the human gastro-intestinal
tract. Final numbers of organisms (cfu)/ml reactor contents ( c) were attained such that log 10 c = 6.9 ± 0.1. The addition caused the CH 4 production to decrease below the detection limit while total gas and CO 2 production in the fifth (transverse colon) and sixth reactor (descending colon) were lowered and the acetic acid concentration
was augmented. Ending the supplementation caused CH 4 production to re-establish within 4 days, while CO 2 production increased much more slowly. The concentration of acetic acid only started to decrease after 7 days. The results
indicate that P. productus, upon regular administration, is able to compete with methanogens for H 2 in the gastro-intestinal microbial ecosystem because of its reductive acetogenic character.
Received: 11 December 1996 / Received revision: 26 February 1997 / Accepted: 1 March 1997 相似文献
8.
SO 2–ethanol–water (SEW) spent liquor from spruce chips was successfully used for batch and continuous production of acetone, butanol and ethanol (ABE). Initially, batch experiments were performed using spent liquor to check the suitability for production of ABE. Maximum concentration of total ABE was found to be 8.79 g/l using 4-fold diluted SEW liquor supplemented with 35 g/l of glucose. The effect of dilution rate on solvent production, productivity and yield was studied in column reactor consisting of immobilized Clostridium acetobutylicum DSM 792 on wood pulp. Total solvent concentration of 12 g/l was obtained at a dilution rate of 0.21 h −1. The maximum solvent productivity (4.86 g/l h) with yield of 0.27 g/g was obtained at dilution rate of 0.64 h −1. Further, to increase the solvent yield, the unutilized sugars were subjected to batch fermentation. 相似文献
9.
Summary The breakdown of itaconic acid by preformed mats of a local strain of Aspergillus terreus was studied using the zone-strip technique. Low p H values restrained the uptake of itaconic acid and the accumulation of various other acids while higher p H values exerted an opposite effect. The results obtained when using various enzyme inhibitors were those anticipated on basis of the direct transformation of itaconic to aconitic acid through the fixation of CO 2 and of the existence of the T.A.C. (tricarboxylic acid cycle) as a main metabolic channel operating in this organism. 相似文献
10.
Summary Living Aspergillus niger cells were entrapped in polyacrylamide gels and employed in both replacement batch and continuous column bioreactors to produce citric acid from sucrose. With the replacement batch bioreactor, increase of citric acid was observed under conditions of higher aeration and of wider surface of immobilized cells. With the continuous bioreactor, the maximum citric acid yield was 39.1 mg/h per 40 g gels. The biocatalyst activity or half-life was 105 days. 相似文献
11.
Repeated batch cultivation was applied to enrich hydrogen fermentative microflora under extreme-thermophilic (70°C) environment.
Initial inoculums received from a hydrogen producing reactor fed with organic fraction of household solid wastes. In total
seven transfers was conducted and maximum hydrogen yield reached 296 ml H 2/g (2.38 mol/mol) glucose and 252 ml H 2/g (2.03 mol/mol) for 1 and 2 g/l glucose medium, respectively. It was found that hydrogen production was firstly decreased
and got increased gradually from third generation. Acetate was found to be the main metabolic by-product in all batch cultivation.
Furthermore, the diversity of bacterial community got decreased after repeated batch cultivation. It was proved that repeated
batch cultivation was a good method to enhance the hydrogen production by enriching the mixed cultures of dominant species. 相似文献
12.
An anaerobic granular sludge was enriched to utilize H 2/CO 2 in a continuous gas-fed up-flow anaerobic sludge reactor by applying operating conditions expected to produce acetic acid, butyric acid, and ethanol. Three stages of fermentation were found: Stage I with acetic acid accumulation with the highest concentration of 35 mM along with a pH decrease from initial 6 to 4.5. In Stage II, H 2/CO 2 was replaced by 100% H 2 to induce solventogenesis, whereas butyric acid was produced with the highest concentration of 2.5 mM. At stage III with 10 µM tungsten (W) addition, iso-valeric acid, valeric acid, and caproic acid were produced at pH 4.5–5.0. In the batch tests inoculated with the enriched sludge taken from the bioreactor (day 70), however, methane production occurred at pH 6. Exogenous 15 mM acetate addition enhanced both the H 2 and CO 2 consumption rate compared to exogenous 10, 30, and 45 mM acetate by the enriched sludge. Exogenous acetate was failed to be converted to ethanol using H 2 as electron donor by the enriched acetogens. 相似文献
13.
Methanococcus thermolithotrophicus was grown in a mineral salts medium at 65° C in a fermenter gassed with H 2 and CO 2, which were the sole carbon and energy sources. Evolution of growth parameters during batch culture experiments showed the existence of an uncoupling phenomenon. The growth was then studied using a continuous technique and steady states for various gas flow rates were obtained. Y
CH
4and the maintenance coefficient varied with the gas input. The maximum Y
CH
4 determined for Methanococcus thermolithotrophicus was 3.33 g·mol -1 CH 4. An excess of energy and carbon sources induced uncoupling of growth. 相似文献
14.
Long lasting batch cultures of Azospirillum brasilense SP 7 ATCC 29145 grown in liquid malate medium for 8–14 days without any fixed nitrogen source exhibited a biphasic nitrogenase activity, when incubated under gas atmospheres of 99.0% N 2 and 1.0% O 2 or 99.5% N 2 and 0.5% O 2 respectively. Maximum specific nitrogenase activity was 1100 nmol C 2H 4·mg protein -1·h -1. Poly-3-hydroxybutanoic acid (PHBA) synthesis and growth of the cells also showed two phases. Maxima and minima of glutamine synthetase activity developed synchronously with nitrogenase activity, whereas those of glutamate dehydrogenase and alanine aminotransferase were reverse. During a 192 h period of growth protein increased 3–4-fold and PHBA 25 fold. At maximum accumulation of the polymer the PHBA-nitrogen ratio was 6:1 or 8:1. Azospirillum brasilense was also able to fix nitrogen on agar surfaces exposed to air, but nitrogen fixation was monophasic under these conditions during a 14 d period. Specific nitrogenase activity was dependent on the type and concentration of the source of fixed nitrogen (leucine, ammonia) in solidified media. With 1 mM leucine maximum specific nitrogenase activity was 110 nmol C 2H 4·mg protein -1·h -1.Non-Standard Abbreviations PHBA
poly-3-hydroxybutanoic acid
- TAPS
tris(hydroxymethyl)methylaminopropane sulfonic acid
- TES
N-tris(hydroxymethyl)methyl-2-aminoethane sulfonic acid
- TRICINE
N-tris(hydroxymethyl)methylglycine
- TRIS
tris(hydroxymethyl)aminomethane 相似文献
15.
Summary A thermophilic methanogenic bacterium, Methanococcus thermolithotrophicus, was grown on H 2 and CO 2 in both batch and continuous culture, in a fermentor equipped with either a straight blade impeller or a Rushton impeller. Production was continued until 470 l CH 4·l -1 per day was obtained with a biomass of 3.5 g dry wt. l -1 under batch conditions. 相似文献
16.
Summary Ethanol was produced by a strain of Pichia stipitis adapted to an inhibitory acid wood hydrolysate of Pinus radiata. The best ethanol productivity for batch cultures was 0.21 g/l h at 0.7% ethanol. Varying culture conditions increased ethanol concentration to 0.76%, however the productivity decreased to 0.18 g/l h. A decrease in ethanol concentration in the culture fluid was noted late in the batch which suggested ethanol catabolism. Values of kinetic parameters ( K
m, K
s,
max, and V
max) were evaluated for this system. The use of calcium alginate immobilized cells in a continuous-flow stirred tank reactor lead to enhanced fermentative performance, namely a maximum productivity of 0.27 g/l h and 1.13% ethanol yield. The immobilized cells in continuous flow reactors represent an attractive option for fermenting sugars released by sulphuric acid hydrolysis of P. radiata wood. 相似文献
17.
In this study, the utilization of potato-juice, the organic by-product from potato-starch processing, for biogas production was investigated in batch assay and in high rate anaerobic reactors. The maximum methane potential of the potato-juice determined by batch assay was 470 mL-CH 4/gVS-added. Anaerobic digestion of potato-juice in an EGSB reactor could obtain a methane yield of 380 mL-CH 4/gVS-added at the organic loading rate of 3.2 gCOD/(L-reactor.d). In a UASB reactor, higher organic loading rate of 5.1 gCOD/(L-reactor.d) could be tolerated, however, it resulted in a lower methane yield of 240 mL-CH 4/gVS-added. The treatment of reactor effluent was also investigated. By acidification with sulfuric acid to pH lower than 5, almost 100% of the ammonia content in the effluent could be retained during the successive up-concentration process step. The reactor effluent could be up-concentrated by evaporation to minimize its volume, and later be utilized as fertilizer. 相似文献
18.
In batch culture diesel oil was degraded rapidly, with a maximum growth rate (for a consortium of microorganisms) of 0.55 h -1. The corresponding yield Y
SX
was 0.1 Cmol/Cmol. In a continuous stirred tank reactor the maximum dilution rate was about 0.25 h -1, with a yield of 0.3 Cmol/Cmol. With a residence time of 1 day 82% of the influent oil was degraded. In the batch reactor, of the mixture of linear and branched alkanes the linear alkanes were degraded fastest and with the highest yield. Only after most of the linear alkanes had disappeared were the branched alkanes consumed. In a CSTR a large part of the branched alkanes was not degraded. 相似文献
19.
Lactic acid is a green chemical that can be used as a raw material for biodegradable polymer. To produce lactic acid through
microbial fermentation, we previously screened a novel lactic acid bacterium. In this work, we optimized lactic acid fermentation
using a newly isolated and homofermentative lactic acid bacterium. The optimum medium components were found to be glucose,
yeast extract, (NH 4) 2HPO 4, and MnSO 4. The optimum pH and temperature for a batch culture of Lactobacillus sp. RKY2 was found to be 6.0 and 36°C, respectively. Under the optimized culture conditions, the maximum lactic acid concentration
(153.9 g/L) was obtained from 200 g/L of glucose and 15 g/L of yeast extract, and maximum lactic acid productivity (6.21 gL −1h −1) was obtained from 100 g/L of glucose and 20 g/L of yeast extract. In all cases, the lactic acid yields were found to be
above 0.91 g/g. This article provides the optimized conditions for a batch culture of Lactobacillus sp. RKY2, which resulted in highest productivity of lactic acid. 相似文献
20.
The study investigated the use of hollow-fiber membranes for hydrogen (H 2) delivery to support the biological reductive dechlorination of tetrachloroethene (PCE) Two experiments were performed in which H 2 was supplied through membranes placed in stirred batch reactors containing a mixed methanogenic/dechlorinating culture and PCE (≤10?µ M. Reductive dechlorination of PCE to cis-dichloroethene was sustained in the reactors receiving H 2 (1% H 2 and 50% H 2), while negligible dechlorination was observed in control reactors (100% N 2). The 1%-H 2-fed reactor outperformed the 50%-H 2-fed reactor in the first experiment. However, the dechlorinating performance in the two reactors was similar in the second experiment. Despite relatively high H 2 concentrations (4.6 to 178?µ M) that led to H 2 consumption (and CH 4 production) by methanogens, dechlorination was effectively maintained for the duration of the experiments (35 to 62 days). The results of this study are significant in that dechlorination was sustained in a minimal medium by membrane-delivered H 2. Dechlorination was also maintained at aqueous H 2 concentrations that exceeded the thermodynamic thresholds for not only dechlorination (<0.1 to 2?n M, but also methanogenesis (~10?n M) and homoacetogenesis (94 to 400?n M. The results of these experiments suggest that membranes are a promising H 2 delivery technology for stimulating the bioremediation of chlorinated ethene-contaminated aquifers. 相似文献
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