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1.
《Journal of biotechnology》1999,67(2-3):113-134
The mixed culture system was considered in the present research where sugars such as glucose were converted to lactate by Lactobacillus delbrueckii and the lactate was converted to poly β-hydroxybutyrate (PHB) by Alcaligenes eutrophus in one fermentor. For the modeling of the effect of NH3 concentration on the cell growth of A. eutrophus and PHB production rates, metabolic flux distributions were computed at two culture phases of cell growth and PHB production periods. It was found that the NADPH, generated through isocitrate dehydrogenate in TCA cycle, was predominantly utilized for the reaction from α-ketoglutalate to glutamate when NH3 was abundant, while it tended to be utilized for the PHB production through acetoacetyl CoA reductase as NH3 concentration decreased. This phenomenon was reflected in the development of mathematical model. In the mixed culture experiments, the two phases were observed, namely the lactate production phase due to L. delbrueckii and the lactate consumption phase due to A. eutrophus. The lactate concentration could be estimated on-line by the amount of NaOH solution and HCl solution supplied to keep the culture pH at constant level. Several mixed culture experiments were conducted to see the dynamics of the system. Finally, a mathematical model which can describe the dynamic behavior of the present mixed culture was developed and the model parameters were tuned for fitting the experimental data. The model may be used for several purposes such as control, optimization, and understanding process dynamics etc. 相似文献
2.
Competitive Exclusion of Salmonella enterica serovar Enteritidis by Lactobacillus crispatus and Clostridium lactatifermentans in a Sequencing Fed-Batch Culture
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Paul W. J. J. van der Wielen Len J. A. Lipman Frans van Knapen Steef Biesterveld 《Applied microbiology》2002,68(2):555-559
Competitive exclusion of Salmonella enterica serovar Enteritidis by a mixed culture of Lactobacillus crispatus and Clostridium lactatifermentans was studied in a sequencing fed-batch reactor mimicking the cecal ecophysiology of broiler chickens. Growth of serovar Enteritidis was inhibited by a mixed culture of L. crispatus and C. lactatifermentans at pH 5.8 but not by a monoculture of L. crispatus at the same pH. Moreover, experiments performed at pH 7.0 did not show growth inhibition of serovar Enteritidis. L. crispatus fermented lactose to lactate, and C. lactatifermentans fermented the lactate to acetate and propionate in a mixed culture of L. crispatus and C. lactatifermentans growing on lactose. In contrast, only lactate was produced from lactose by a monoculture of L. crispatus. At pH 5.8 considerable concentrations of acetate and propionate were present as undissociated acids, whereas only trace levels of undissociated lactate were present at pH 5.8 due to the low pKa of lactate. At pH 7.0 all three acids were present in their dissociated forms. We conclude that a mixed culture of L. crispatus and C. lactatifermentans inhibits growth of serovar Enteritidis under cecal growth conditions. The undissociated forms of acetate and propionate produced in the mixed culture inhibited the growth of serovar Enteritidis. 相似文献
3.
Bo Kong Xiandong Zeng Xiaoying Liu Xuefang Li Jun Li Shenglian Luo Wanzhi Wei 《Current microbiology》2009,59(5):565-571
The kinetics of chromium(VI) reduction by Pseudomonas aeruginosa (P. aeruginosa) and Escherichia coli (E. coli) was studied under both pure and mixed cultures. Initially, the study of kinetics was performed in pure culture. It was observed that the growth of the two bacteria was both inhibited in the presence of chromium(VI). The maximum specific growth rate (μ m ) of P. aeruginosa decreased from 2.3942 h?1 (without Cr(VI)) to 1.8551 h?1 (with Cr(VI)). Under the mixed culture, the growth of E. coli was inhibited by P. aeruginosa. The maximum specific growth rate (μ m ) of E. coli decreased form 0.871 h?1 (in pure culture) to 0.153 h?1 (in mixed culture). When the concentration of each bacterium was 4.5 × 108 cells ml?1, the half-velocity reduction rate constant (K C) and the maximum specific reduction rate constant (v max) of chromium(VI) were 80.05 mg chromium(VI) l?1 and 3.674 mg chromium(VI) cells?1 h?1, respectively. The results showed that the simulation appeared in good agreement with the experimental data, supporting the series of mathematical models represented the bacteria growth and chromium(VI) reduction in both pure and mixed cultures usefully. 相似文献
4.
Commensalistic Interaction Between Lactobacillus acidophilus and Propionibacterium shermanii 总被引:1,自引:0,他引:1
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Propionibacterium shermanii and Lactobacillus acidophilus were grown in batch mixed culture in a 5-liter fermenter under controlled conditions of pH 5.8 and 35°C on a semisynthetic medium with glucose as an energy source. Cellular efficiencies and fermentation balances were developed for this pair and compared with P. shermanii grown in pure culture on glucose, lactate, and a mixture of these substrates and with L. acidophilus grown on glucose. P. shermanii had ATP yield coefficient values of 17 for each substrate alone but had an average value of 30 for substrate mixtures. Growth rates were similar for P. shermanii on glucose or lactate but higher cell yields were observed for glucose. P. shermanii used both lactate and glucose in mixed substrate until lactate was exhausted, and growth rates slowed thereafter. L. acidophilus had a similar ATP yield coefficient of 15 but produced lower cell yields than did P. shermanii on glucose. Mixed culture of both microorganisms on glucose resulted in much faster and nearly equal growth rates for both and no lactate accumulation in the medium. Acetic acid production rates per generation were lower in mixed culture, suggesting use by the growing culture. The cause of the synergistic effect was not determined but may be due to the rapid production and removal of lactate or CO2 enhancement in mixed culture. 相似文献
5.
A simple method for the calculation of kinetic parameters (Km, Vmax) under conditions of changing substrate concentrations is presented. An application of the method to detect shifts in groups involved in the utilization of a substrate in a mixed microbial culture is given. 相似文献
6.
J. P. Salanitro L. A. Diaz M. P. Williams H. L. Wisniewski 《Applied microbiology》1994,60(7):2593-2596
We have isolated a mixed bacterial culture (BC-1) which is capable of degrading the gasoline oxygenate methyl t-butyl ether (MTBE). BC-1 was developed from seed microorganisms present in a chemical plant biotreater sludge. This enrichment culture has been maintained in continuous culture treating high concentrations of MTBE (120 to 200 mg/liter) as the sole carbon source in a simple feed containing NH4+, PO43-, Mg2+, and Ca2+ nutrients. The unit had a stable MTBE removal rate when maintained with a long cell retention time (ca. 80 to 90 days); however, when operated at a ≤50-day cell waste rate, loss of MTBE-degrading activity was observed. The following three noteworthy experimental data show that MTBE is biodegraded extensively by BC-1: (i) the continuous (oxygen-sparged) culture was able to sustain a population of autotrophic ammonia-oxidizing bacteria which could nitrify influent NH4+ concentrations at high rates and obtain CO2 (sole carbon source for growth) from the metabolism of the alkyl ether, (ii) BC-1 metabolized radiolabeled either (14CH3O-MTBE) to 14CO2 (40%) and 14C-labeled cells (40%), and (iii) cell suspensions of the culture were capable of degrading (substrate depletion experiments) MTBE to t-butyl alcohol, a primary metabolite of MTBE. BC-1 is a mixed culture containing several bacterial species and is the first culture of its kind which can completely degrade an alkyl ether. 相似文献
7.
In this study, chlorophyll fluorescence parameters (?F/F m′, F v/F m) and oxygen evolution of female vegetative tissues of Porphyra katadai var. hemiphylla in unisexual culture (FV) and in mixed culture with male vegetative tissues (FV-M) were followed at 5–20 °C, 10 and 80 μmol photons m?2 s?1. The formation of reproductive tissues was closely correlated with decreasing photosynthetic activities. At the same temperature the tissues cultured under 80 μmol photons m?2 s?1 showed a greater extent of maturation than those under 10 μmol photons m?2 s?1, and their decrease in photosynthesis was also larger. Under the same light intensity the extent of maturation increased with increasing temperature, and both cultures showed higher values of ?F/F m′ and F v/F m at 10 and 15 °C, while their oxygen evolution became negative at 15–20 °C during the later period. Under the same culture condition the maturation of FV-M culture was relatively faster than that of FV culture, while their photosynthetic activity, especially ?F/F m′, was lower. 相似文献
8.
Oxidative Dissolution of Arsenopyrite by Mesophilic and Moderately Thermophilic Acidophiles 总被引:8,自引:1,他引:7
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Olli H. Tuovinen Tariq M. Bhatti Jerry M. Bigham Kevin B. Hallberg Oswaldo Garcia Jr. E. Brje Lindstrm 《Applied microbiology》1994,60(9):3268-3274
The purpose of this work was to determine solution- and solid-phase changes associated with the oxidative leaching of arsenopyrite (FeAsS) by Thiobacillus ferrooxidans and a moderately thermoacidophilic mixed culture. Jarosite [KFe3(SO4)2(OH)6], elemental sulfur (S0), and amorphous ferric arsenate were detected by X-ray diffraction as solid-phase products. The oxidation was not a strongly acid-producing reaction and was accompanied by a relatively low redox level. The X-ray diffraction lines of jarosite increased considerably when ferrous sulfate was used as an additional substrate for T. ferroxidans. A moderately thermoacidophilic mixed culture oxidized arsenopyrite faster at 45°C than did T. ferroxidans at 22°C, and the oxidation was accompanied by a nearly stoichiometric release of Fe and As. The redox potential was initially low but subsequently increased during arsenopyrite oxidation by the thermoacidophiles. Jarosite, S0, and amorphous ferric arsenate were also formed under these conditions. 相似文献
9.
A. G. Kisten’ I. K. Kurdish Z. T. Bega I. Yu. Tsarenko 《Applied Biochemistry and Microbiology》2006,42(3):278-283
We studied the effect of a clay mineral, palygorskite, on the physiological activity of Azotobacter chroococcum and the phosphate-mobilizing bacterium Bacillus subtilis, as well as their mixed cultures, under various oxygen supply conditions during the utilization of phosphorus from readily and poorly soluble compounds (K2HPO4 · 3H2O) and (Ca3(PO4)2), respectively. During cultivation of the bacteria in a nutrient medium with Ca3(PO4)2, the number of microorganisms was higher than that observed in a medium with K2HPO4. An increase in oxygen mass transfer in the nutrient medium was followed by a rise in the number of Bacillus subtilis cells and an inhibition of Azotobacter chroococcum growth. An addition of palygorskite (5 g/l) into the nutrient medium stimulated the growth of both bacteria and stopped the decreasing growth of Azotobacter chroococcum at high values of oxygen mass transfer. The number of Bacillus and, particularly, Azotobacter cells was two to five times lower in a mixed culture than in a monoculture. These differences were less significant during the cultivation of mixed cultures in medium with palygorskite. 相似文献
10.
Th. E. Cappenberg 《Microbial ecology》1975,2(1):60-72
Ecological relationships between sulfate-reducing and methane-producing bacteria in mud of Lake Vechten have been studied by continuous culture studies using the chemostat technique. The maximum specific growth rate (μ max) and saturation constant (K s) were, respectively, 0.36 hr−1 and 0.047 mM for lactate-limited growth ofDesulfovibrio desulfuricans and 0,011 hr−1 and 0.17 mM for acetate-limited growth ofMethanobacterium sp. Calculated values for the true molar growth yieldsY G) and maintenance coefficients (m) were 30.6 g bacterial mass/mole of lactate and 0.53 g substrate/g dry wt hr forD. desulfuricans and 37.8 g bacterial mass/mole of acetate and 0.54 g substrate/g dry wt hr forMethanobacterium. No growth ofMethanobacterium was observed at apS2− value (the hydrogen sulfide potential) of more than 11 and there was no effect on the growth atpS2− values above 13. In mixed continuous culture experiments the concentration of acetate decreased in the secondstage growth vessel, whereas that of methane increased stoichiometrically. If the substrate concentration in the reservoirs (S r) was increased from 0.1 to 0.5 mg/ml, the population ofDesulfovibrio increased and that ofMethanobacterium was washed out of the culture vessel, since the concentration of hydrogen sulfide reached apS2− value of 10.5. From the mixed continuous culture experiments a commensalism between the two species can be described, i.e., the acetate-fermentingMethanobacterium benefits from the acetate released byDesulfovibrio which is, in turn, not affected in the presence of the former. 相似文献
11.
Modeling Reduction of Uranium U(VI) under Variable Sulfate Concentrations by Sulfate-Reducing Bacteria 总被引:4,自引:2,他引:2
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The kinetics for the reduction of sulfate alone and for concurrent uranium [U(VI)] and sulfate reduction, by mixed and pure cultures of sulfate-reducing bacteria (SRB) at 21 ± 3°C were studied. The mixed culture contained the SRB Desulfovibrio vulgaris along with a Clostridium sp. determined via 16S ribosomal DNA analysis. The pure culture was Desulfovibrio desulfuricans (ATCC 7757). A zero-order model best fit the data for the reduction of sulfate from 0.1 to 10 mM. A lag time occurred below cell concentrations of 0.1 mg (dry weight) of cells/ml. For the mixed culture, average values for the maximum specific reaction rate, Vmax, ranged from 2.4 ± 0.2 μmol of sulfate/mg (dry weight) of SRB · h−1) at 0.25 mM sulfate to 5.0 ± 1.1 μmol of sulfate/mg (dry weight) of SRB · h−1 at 10 mM sulfate (average cell concentration, 0.52 mg [dry weight]/ml). For the pure culture, Vmax was 1.6 ± 0.2 μmol of sulfate/mg (dry weight) of SRB · h−1 at 1 mM sulfate (0.29 mg [dry weight] of cells/ml). When both electron acceptors were present, sulfate reduction remained zero order for both cultures, while uranium reduction was first order, with rate constants of 0.071 ± 0.003 mg (dry weight) of cells/ml · min−1 for the mixed culture and 0.137 ± 0.016 mg (dry weight) of cells/ml · min−1 (U0 = 1 mM) for the D. desulfuricans culture. Both cultures exhibited a faster rate of uranium reduction in the presence of sulfate and no lag time until the onset of U reduction in contrast to U alone. This kinetics information can be used to design an SRB-dominated biotreatment scheme for the removal of U(VI) from an aqueous source. 相似文献
12.
E. A. Saratovskikh V. A. Shcherbakova R. N. Yarullin 《Applied Biochemistry and Microbiology》2018,54(1):45-52
The degradation of native and pretreated nitrocellulose (NC) by the microscopic fungus Fusarium solani VKM F-819 and a mixed culture of the fungus with a sulfate-reducing bacterium Desulfovibrio desulfuricans VKM B-1388 has been studied. It has been shown that NC pretreatment with UV radiation and ozone promoted its subsequent biodegradation. The degradation of the thus treated NC by a mixed culture of F. solani and D. desulfuricans was the most effective as compared to all other treatment options. The NC nitrogen content decreased from 13.38 to 10.03%; the number average (Mn) and weight average (Mw) molecular masses decreased by three and two times, respectively. These magnitudes were achieved after 5 days of incubation of the pretreated NC. The obtained data can be used to further develop NC degradation technology. 相似文献
13.
《Process Biochemistry》2007,42(4):570-579
Growth and kefiran production rates of Lactobacillus kefiranofaciens were significantly enhanced in a mixed culture with Saccharomyces cerevisiae as compared with those in a pure culture. Because a positive effect on growth and kefiran production of L. kefiranofaciens in a mixed culture was observed, the elucidation of interaction between L. kefiranofaciens and S. cerevisiae may lead to higher productivity. Hence, microbial performance of each strain was investigated and analyzed by a mathematical model. The mathematical model for kefiran fermentation in a mixed culture of L. kefiranofaciens and S. cerevisiae was established, and the impact of S. cerevisiae on cell growth, kefiran formation, and substrate assimilation of L. kefiranofaciens were considered. The behavior of L. kefiranofaciens in a mixed culture was predicted using a developed mathematical model in this work, and the predictions were compared with the results from mixed culture experiments. The overall mathematical model is capable of describing the behavior of S. cerevisiae in a mixed culture as a lactic acid consumer, nitrogen source competitor and protective function inducer for L. kefiranofaciens. Furthermore, the constructed model described the phenomena in mixed cultures under aerobic and anaerobic conditions. Finally, the optimal inoculation ratios of S. cerevisiae to L. kefiranofaciens at 7-fold and 10-fold under aerobic and anaerobic conditions were obtained by applying the mixed culture model, respectively. 相似文献
14.
《Journal of Fermentation and Bioengineering》1992,73(3):219-224
Four bacteria isolated from peat biofilters, Thiobacillus thioparus DW44, Thiobacillus sp. HA43, Xanthomonas sp. DY44 and Hyphomicrobium sp. I55, were selected to enhance the removal ratios of hydrogen sulfide (H2S), methanethiol (MT) and dimethyl sulfide (DMS) in a mixed gas system. Two bacteria, DW44 and I55, which degrade H2S, MT, DMS and dimethyl disulfide (DMDS), were mixed with DY44 or HA43 which degrade only H2S and MT. Although DMS removal was significantly inhibited by the presence of H2S and MT in a peat biofilter inoculated with the single bacterium, enhanced removability of H2S, MT and DMS was observed by mixing Hyphomicrobium sp. I55 either with Thiobacillus sp. HA43 or Xanthomonas sp. DY44. The removal rate (g-S-kg-dry peat−1·d−1) by I55 after 8 d was 0.664 in total sulfur load, 0.827 g-S·kg-dry g-S·-kg-dry peat−1·d−1, but the rates by the mixed cultures of I55 plus HA43, and I55 plus DY44 were 0.760 and 0.801, respectively. In particular, DMS removability in mixed gases by a mixed culture of I55 and DY44 was almost equivalent to that by I55 when only DMS was supplied, suggesting that removal of H2S and MT, which inhibited DMS removal, was preferentially conducted by DY44 and led to improved DMS removability by I55. 相似文献
15.
《Biochemical Engineering Journal》2002,10(3):157-173
The unstructured mathematical model was developed in the present investigation for the mixed culture, where the metabolites produced by one microorganism is assimilated by the other microorganism. For this, we specifically employed such model system in which sugars such as glucose were converted to lactate by Lactobacillus delbrueckii and the lactate was converted in turn to poly-β-hydroxybutyrate (PHB) by Ralstonia eutropha in one fermentor. Several batch and fed-batch culture experiments were conducted using each microorganism at different dissolved oxygen (DO) concentrations. Those experimental data were then fitted to the mathematical model, which can describe the dynamics of a mixed culture. Some of the model parameters were expressed as functions of DO concentrations, and some of the other model parameters were tuned based on the mixed culture experiments. The model developed describes the effects of such concentrations of glucose, lactate, DO, and NH3 on the dynamic behavior of such concentrations as both microorganisms, glucose, lactate, and PHB. Optimal operating condition was then investigated using the model developed. It was found that the periodic change in DO concentration improved such performance as PHB yield, and it was verified by experiments. The optimal NH3 concentration profile was also obtained for the efficient PHB production by the application of the maximum principle. 相似文献
16.
The influence of inoculum size on the colony-forming units, production of aflatoxin B1 (AFB1) and ochratoxin A (OTA) was determined when Aspergillus flavus and A. niger aggregate strains were cultured alone and in pairs on irradiated peanut grains at 28°C and 0.97 water activity (aW). The results showed a marked influence of inoculum factor on fungal counts, AFB1 and OTA production in single and paired cultures. Fungal counts of the A. niger aggregate strain in interacting cultures at 7, 14 and 21?days of incubation were significantly higher than those observed in the A. flavus strain, except in the mixed culture with 102 spores/ml of both strains. In all mixed culture assays, the AFB1 production was significantly reduced in comparison with the accumulation of mycotoxin in single cultures. A total inhibition in AFB1 production was observed in some interactions as 102 spores/ml of A. flavus and 103 spores/ml of A. niger aggregate strain at 7 and 14?days, among others. With regard to OTA production, a stimulation in the interacting cultures was observed at all inoculum sizes and incubation period. The highest levels of OTA accumulation were observed at 14?days for all interacting cultures. The maximum level was reach in the culture 103 spores/ml of A. niger aggregate and 104 spores/ml of A. flavus (p?<?0.001). These results suggest that, under optimal environmental conditions in peanut grains, the interaction between A. flavus and A. niger aggregate strains could result in an inhibition of AFB1 and in a stimulation of OTA production. 相似文献
17.
Comparison of Two Cellulomonas Strains and Their Interaction with Azospirillum brasilense in Degradation of Wheat Straw and Associated Nitrogen Fixation 总被引:2,自引:1,他引:1
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A mutant strain of Cellulomonas sp. CS1-17 was compared with Cellulomonas gelida 2480 as the cellulolytic component of a mixed culture which was responsible for the breakdown of wheat straw to support asymbiotic nitrogen fixation by Azospirillum brasilense Sp7 (ATCC 29145). Cellulomonas sp. strain CSI-17 was more efficient than was C. gelida in cellulose breakdown at lower oxygen concentrations and, in mixed culture with A. brasilense, it supported higher nitrogenase activity (C2H2 reduction) and nitrogen fixation with straw as the carbon source. Based on gravimetric determinations of straw breakdown and total N determinations, the efficiency of nitrogen fixation was 72 and 63 mg of N per g of straw utilized for the mixtures containing Cellulomonas sp. and C. gelida, respectively. Both Cellulomonas spp. and Azospirillum spp. exhibited a wide range of pH tolerance. When introduced into sterilized soil, the Cellulomonas sp.-Azospirillum brasilense association was more effective in nitrogen fixation at a pH of 7.0 than at the native soil pH (5.6). This was also true of the indigenous diazotrophic microflora of this soil. The potential implications of this work to the field situation are discussed. 相似文献
18.
19.
Inhibition of Chemoautotrophic Nitrification by Sodium Chlorate and Sodium Chlorite: a Reexamination 总被引:3,自引:5,他引:3
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The oxidation of NH4+ by Nitrosomonas europaea was insensitive to 10 mM NaClO3 (sodium chlorate) but was strongly inhibited by NaClO2 (sodium chlorite; Ki, 2 μM). The oxidation of NO2− by Nitrobacter winogradskyi was inhibited by both ClO3− and ClO2− (Ki for ClO2−, 100 μM). N. winogradskyi reduced ClO3− to ClO2− under both aerobic and anaerobic conditions, and as much as 0.25 mM ClO2− was detected in the culture filtrate. In mixed N. europaea-N. winogradskyi cell suspensions, the oxidation of both NH4+ and NO2− was inhibited in the presence of 10 mM ClO3− after a 2-h lag period, despite the fact that, under these conditions, ClO2− was not detected in the filtrate. The data are consistent with the hypothesis that, in mixed culture, NH4+ oxidation is inhibited by ClO2− produced by reduction of ClO3− by the NO2− oxidizer. The use of ClO3− inhibition of NO2− oxidation in assays of nitrification by mixed populations necessitates cautious interpretation unless it can be shown that the oxidation of NH4+ is not affected. 相似文献
20.
Lactococcus lactis SpOx Spontaneous Mutants: a Family of Oxidative-Stress-Resistant Dairy Strains
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Tatiana Rochat Jean-Jacques Gratadoux Gérard Corthier Bérard Coqueran Maria-Elena Nader-Macias Alexandra Gruss Philippe Langella 《Applied microbiology》2005,71(5):2782-2788
Numerous industrial bacteria generate hydrogen peroxide (H2O2), which may inhibit the growth of other bacteria in mixed ecosystems. We isolated spontaneous oxidative-stress-resistant (SpOx) Lactococcus lactis mutants by using a natural selection method with milk-adapted strains on dairy culture medium containing H2O2. Three SpOx mutants displayed greater H2O2 resistance. One of them, SpOx3, demonstrated better behavior in different oxidative-stress situations: (i) higher long-term survival upon aeration in LM17 and milk and (ii) the ability to grow with H2O2-producing Lactobacillus delbrueckii subsp. delbrueckii strains. Furthermore, the transit kinetics of the SpOx3 mutant in the digestive tract of a human flora-associated mouse model was not affected. 相似文献