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1.
Quantification of oxygen production and respiration rates in mixotrophic cultivation of microalgae in nonstirred photobioreactors 下载免费PDF全文
Online monitoring and controlling of different cellular parameters are key issues in aerobic bioprocesses. Since mixotrophic cultivation, in which we observe a mixture of cellular respiration and oxygen production has gained more popularity, there is a need for an on‐process quantification of these parameters. The presented and adapted double gassing‐out method applied to a mixotrophic cultivation of Galdieria sulphuraria , will be a tool for monitoring and further optimization of algal fermentation in nonstirred photobioreactors (PBR). We measured the highest net specific oxygen production rate (opr net) as 5.73 · 10?3 molO2 g?1 h?1 at the lowest oxygen uptake rate (OUR) of 1.00 · 10?4 molO2 L?1 h?1. Due to higher cell densities, we also demonstrated the increasing shading effect by a decrease of opr net, reaching the lowest value of 1.25 10?5 molO2 g?1 h?1. Nevertheless, with this on process measurement, we can predict the relation between the zone in which oxygen is net produced to the area where cell respiration dominates in a PBR, which has a major impact to optimize cell growth along with the formation of different products of interest such as pigments. 相似文献
2.
An-Ping Zeng Hanno Biebl Wolf-Dieter Deckwer 《Applied microbiology and biotechnology》1990,33(3):264-268
Summary The influence of oxygen on growth and production of 2,3-butanediol and acetoin by Enterobacter aerogenes was studied in continuous culture. At all dilution rates (D) studied cell mass increased steadily with increasing oxygen uptake rate (OUR), hence the micro-aerobic cultivation was energy-limited. The biomass yield on oxygen increased with D which suggests that cells need more energy for maintenance functions at lower D. At each D an optimal OUR giving highest volumetric productivity for the sum of butanediol and acetoin was found. The optimal OUR increased with D. The occurrence of optimal OURs results from the various effects of O2 on growth and specific productivity. The latter was found to be a linear function of the specific OUR irrespective of D. At optimal OUR the cells proved to have equal specific OURs and equal specific productivities representing a fixed relationship between fermentative and respiratory metabolism. The product yield based on glucose and corrected for biomass formation was 80%. A product concentration as high as 43 g/l was obtained at D =0.1 h–1 while the volumetric productivity was the highest at D =0.28 h–1 (5.6 g/l and hour). The findings further indicate that growth and product generation are obviously non-associated phenomena. Hence, high productivities may be achievable by cell recycling and cell immobilisation systems.
Offprint requests to: W.-D. Deckwer 相似文献
3.
D. M. Alongi 《Oecologia》1994,98(3-4):320-327
Benthic oxygen consumption and primary production were measured using the bell jar technique in deltaic and fringing mangrove forests of tropical northeastern Australia. In a deltaic forest, rates of sediment respiration ranged from 197 to 1645 mol O2 m–2 h–1 (mean=836), but did not vary significantly with season or intertidal zone. Gross primary production varied among intertidal zones and seasons, ranging from –281 to 1413 mol O2 m–2 h–1 (mean=258). Upon tidal exposure, rates of gross primary production increased, but respiration rates did not change significantly. In a fringing mangrove forest, benthic respiration and gross primary production exhibited strong seasonality. In both forests, rates of oxygen consumption and production were low compared to salt marshes, but equivalent to rates in other mangrove forests. The production:respiration (P/R) ratio varied greatly over space and time (range:–0.61 to 1.76), but most values were «1 with a mean of 0.15, indicating net heterotrophy. On a bare creek bank and a sandflat, rates of gross primary production and P/R ratios were generally higher than in the adjacent mangroves. Low microalgal standing stocks, low light intensity under the canopy, and differences in gross primary production between mangroves and tidal flats, and with tidal status, indicate that benthic microalgae are light-limited and a minor contributor to primary productivity in these tropical mangrove forests. 相似文献
4.
A mass spectrometric 16O2/18O2-isotope technique was used to analyse the rates of gross O2 evolution, net O2 evolution and gross O2 uptake in relation to photon fluence rate by Dunaliella tertiolecta adapted to 0.5, 1.0, 1.5, 2.0 and 2.5 M NaCl at 25°C and pH 7.0.At concentrations of dissolved inorganic carbon saturating for photosynthesis (200 M) gross O2 evolution and net O2 evolution increased with increasing salinity as well as with photon fluence rate. Light compensation was also enhanced with increased salinities. Light saturation of net O2 evolution was reached at about 1000 mol m-2s-1 for all salt concentrations tested. Gross O2 uptake in the light was increased in relation to the NaCl concentration but it was decreased with increasing photon fluence rate for almost all salinities, although an enhanced flow of light generated electrons was simultaneously observed. In addition, a comparison between gross O2 uptake at 1000 mol photons m-2s-1, dark respiration before illumination and immediately after darkening of each experiment showed that gross O2 uptake in the light paralleled but was lower than mitochondrial O2 consumption in the dark.From these results it is suggested that O2 uptake by Dunaliella tertiolecta in the light is mainly influenced by mitochondrial O2 uptake. Therefore, it appears that the light dependent inhibition of gross O2 uptake is caused by a reduction in mitochondrial O2 consumption by light.Abbreviations DCMU
3-(3, 4-dichlorophenyl)-1, 1-dimethylurea
- DHAP
dihydroxy-acetonephosphate
- DIC
dissolved inorganic carbon
- DRa
rate of dark respiration immediately after illumination
- DRb
rate of dark respiration before illumination
- E0
rate of gross oxygen evolution in the light
- NET
rate of net oxygen evolution in the light
- PFR
photon fluence rate
- RubP
rubulose-1,5-bisphosphate
- SHAM
salicyl hydroxamic acid
- U0
rate of gross oxygen uptake in the light 相似文献
5.
In an 18 year old Japanese larch stand, leaf characteristics such as area, weight, gross photosynthetic rate and respiration
rate were studied in order to obtain basic information on estimating canopy photosynthesis and respiration. The leaf growth
courses in area and weight from bud opening were approximated by simple logistic curves. The growth coefficient for the area
growth curve was 0.155–0.175 day−1, while that for the weight growth was 0.112–0.117 day−1. The larger growth coefficient in area growth caused the seasonal change in specific leaf area (SLA) that increased after bud opening to its peak early in May at almost 300 cm2 g−1 and then decreased until it leveled off at about 140 cm2g−1. The change inSLA indicates the possibility that leaf area growth precedes leaf thickness growth. The relationship between the coefficientsa andb of the gross photosynthetic rate (p)-light flux density (1) curve (p=bI/(1+aI)) and the mean relative light flux density (I′/I
0) at each canopy height were approximated by hyperbolic formulae:a=A/(I′/I
0)+B andb=C/(I′/I
0)+D. Leaf respiration rate was also increased with increasingI′/I
0. Seasonal change of gross photosynthetic rate and leaf respiration rate were related to mean air temperature through linear
regression on semilogarithmic co-ordinates. 相似文献
6.
The effect of growth rate on the physiology of Beneckea natriegens was studied in chemostat culture. The molar growth yields (Y) from glucose and oxygen, the specific rates of oxygen (q
O
2) and glucose (q
glc) consumption and the specific rate of CO2 production (q
CO
2) were linearly dependent on the growth rate over the dilution rate 0.17 h-1 to 0.60 h-1. Further increase in the dilution rate resulted in a decrease in growth yield and respiration rate and these changes were coincident with increases in the specific rate of glucose utilisation and of acetate production. The affinity of Beneckea natriegens for glucose was similar when measured either directly in chemostat culture or in a closed oxygen electrode system using harvested bacteria. The total content of cytochromes decreased with increasing growth rate. However, the quantity of CO-binding cytochromes remained independent of growth rate and correlated with the potential respiration rate. 相似文献
7.
J. A. Rodriguez Leon L. Sastre J. Echevarria G. Delgado W. Bechstedt 《Engineering in Life Science》1988,8(4):307-310
The oxygen uptake rate (OUR) was studied in a solid state fermentation process of dried citrus peel with the strain Aspergillus niger QH-2 in order to obtain the growth estimation of the microorganism in the system. The relationship between OUR, the maintenance coefficient (m) and the yield for oxygen consumption YO2 allows the estimation of the biomass rate if we consider that both parameters are not constants in some periods of the process. It was estimated that in the first 24th the strain has an specific growth rate of 0.174 h?1 with values for YO2 and m in the order of 2.84 g-cell/g-oxygen and 0.006 g-oxygen/g-cell ·h respectively. 相似文献
8.
1. River metabolism was measured over an annual cycle at three sites distributed along a 1000 km length of the lowland Murray River, Australia. 2. Whole system metabolism was measured using water column changes in dissolved oxygen concentrations while planktonic and benthic metabolism were partitioned using light‐dark bottles and benthic chambers. 3. Annual gross primary production (GPP) ranged from 775 to 1126 g O2 m?2 year?1 which in comparison with rivers of similar physical characteristics is moderately productive. 4. Community respiration (CR) ranged from 872 to 1284 g O2 m?2 year?1 so that annual net ecosystem production (NEP) was near zero, suggesting photosynthesis and respiration were balanced and that allochthonous organic carbon played a minor role in fuelling metabolism. 5. Planktonic rates of gross photosynthesis and respiration were similar to those of the total channel, indicating that plankton were responsible for much of the observed metabolism. 6. Respiration rates correlated with phytoplankton standing crop (estimated as the sum of GPP plus the chlorophyll concentration in carbon units), yielding a specific respiration rate of ?1.1 g O2 g C?1 day?1. The respiration rate was equivalent to 19% of the maximum rate of phytoplankton photosynthesis, which is typical of diatoms. 7. The daily GPP per unit phytoplankton biomass correlated with the mean irradiance of the water column giving a constant carbon specific photon fixation rate of 0.35 gO2 g Chl a?1 day?1 per μmole photons m?2 s?1 (ca. 0.08 per mole photons m?2 on a carbon basis) indicating that light availability determined daily primary production. 8. Annual phytoplankton net production (NP) estimates at two sites indicated 25 and 36 g C m?2 year?1 were available to support riverine food webs, equivalent to 6% and 11% of annual GPP. 9. Metabolised organic carbon was predominantly derived from phytoplankton and was fully utilised, suggesting that food‐web production was restricted by the energy supply. 相似文献
9.
Jian-Guang Liang Xiao-He Chu Zhi-Qiang Xiong Ju Chu Yong-Hong Wang Ying-Ping Zhuang Si-Liang Zhang 《World journal of microbiology & biotechnology》2011,27(11):2639-2644
Avermectin B1a batch fermentation of Streptomyces avermitilis in a 2 m3 fermentor was investigated by oxygen uptake rate (OUR) regulation during cell growth phase. OUR was controlled by adjusting
of aeration and agitation. Result showed that OUR strongly affected cell growth and antibiotics production. Avermectin B1a biosynthesis could be effectively enhanced when OUR was stably regulated at an appropriate level in batch fermentation of
S. avermitilis. Avermectin B1a yield reached 5568 ± 111 mg/l by controlling maximal OUR between 15 and 20 mmol/l/h during cell growth phase, which was increased
by 21.8% compared with the control (maximal OUR above 20 mmol/l/h). The stimulation effect on avermectin B1a production could be attributed to the improved supply of propionic acid and acetic acid, the precursors of avermectin B1a, in the cells. Hence, this OUR control method during cell growth phase may be a simple and applicable way to improve industrial
production of avermectin. 相似文献
10.
Marieke Koopmans Dirk Martens Rene H. Wijffels 《Marine biotechnology (New York, N.Y.)》2010,12(3):340-349
To obtain more knowledge about carbon requirements for growth by sponges, the growth rate, respiration rate, and clearance
rate was measured in situ in Haliclona oculata. We found that only 34% of the particulate carbon pumped through the sponge was used for both respiration and growth. The
net growth efficiency, being the ratio of carbon incorporated in biomass and the total carbon used by the sponge for respiration
and growth, was found to be 0.099 ± 0.013. Thus, about 10% of the total used carbon was fixed in biomass, and over 90% was
used for generating energy for growth, maintenance, reproduction, and pumping. H. oculata had 2.5 μmol C available for every micromole O2 consumed. A value of 0.75 for respiratory quotient (RQ in micromole CO2 micromole O2−1) was used for H. oculata, which is the average value reported in literature for different marine invertebrates. Thus, carbon was available
in excess to meet the respiratory demand. Oxygen was found not to be the limiting factor for growth, since only 3.3% of the
oxygen pumped through the sponge body was used. Our results indicate that both oxygen and carbon availability are not limiting.
The low growth efficiency agrees with the low growth rates found for the species used in this study. 相似文献
11.
The effect of steady-state nitrogen limitation on photo-synthetic characteristics and growth efficiency was examined in the marine haptophyte Isochrysis galbana Green. Nitrate limited chemostats were maintained at nine dilution rates, ranging from 0.18-0.96 d?1, under continuous irradiance levels of 175 μmole quanta·m?2·s?1, an irradiance level which saturated photosynthesis at all growth rates. Nitrogen limitation led to an overall reduction in pigmentation and a decrease in the cellular concentration of reaction centers; however, the optical absorption cross section, normalized to Chl a, increased. Moreover, Chl c/a ratios were higher in nitrogen-limited cells: the change in Chl c/a ratios were correlated with an increase in the functional size of Photosystem II. Both light saturated photosynthetic rates normalized per cell and specific respiratory losses were positively linearly correlated with growth rate. Light saturated photosynthetic rates normalized to Chl a remained relatively insensitive to the rate of nitrogen supply. The minimum quantum requirement for gross photosynthetic oxygen evolution increased from 12.4 to 17.0 quanta/O2. At the growth irradiance, the quantum requirement increased 88%, from 19.9 to 37.5 quauta/O2 Photosynthesis/respiration ratios remained relatively constant at dilution rates greater than 35% of the maximum relative growth rate. Consequently, net growth efficiency, defined as the ratio of the specific growth rate, μ, to specific gross photosynthesis, P, also remained relatively constant over this range of growth rates averaging 85 ± 3%. 相似文献
12.
The oxygen and nutrient dynamics of the zooxanthellate, upside down jellyfish (Cassiopea sp.), were determined both in situ and during laboratory incubations under controlled light conditions. In the laboratory,
Cassiopea exhibited a typical Photosynthesis–Irradiance (P–I) curve with photosynthesis increasing linearly with irradiance, until
saturation was reached at an irradiance of ~400 μE m−2 s−1, with photosynthetic compensation (photosynthesis = respiration) being achieved at an irradiance of ~50 μE m−2 s−1. Under saturating irradiation, gross photosynthesis attained a rate of almost 3.5 mmol O2 kg WW−1 h−1, whereas the dark respiration rate averaged 0.6 mmol O2 kg WW−1 h−1. Based upon a period of saturating irradiance of 9 h, the ratio of daily gross photosynthesis to daily respiration was 2.04.
Thus, photosynthetic carbon fixation was not only sufficient to meet the carbon demand of respiration, but also to potentially
support a growth rate of ~3% per day. During dark incubations Cassiopea was a relatively minor source of inorganic N and P, with the high proportion of NO
X
(nitrate + nitrite) produced indicating that the jellyfish were colonised by nitrifying bacteria. Whereas, under saturating
irradiance the jellyfish assimilated ammonium, NO
X
and phosphate from the bathing water. However, the quantities of inorganic nitrogen assimilated were small by comparison
to carbon fixation rates and the jellyfish would need to exploit other sources of nitrogen, such as ingested zooplankton,
in order to maintain balanced growth. During in situ incubations the presence of Cassiopea had major effects on benthic oxygen and nutrient dynamics, with jellyfish occupied patches of sediment having 3.6-fold higher
oxygen consumption and 4.5-fold higher ammonium regeneration rates than adjacent patches of bare sediment under dark conditions.
In contrast at saturating irradiance, jellyfish enhanced benthic photosynthetic oxygen production almost 100-fold compared
to the sediment alone and created a small sink for inorganic nutrients, whereas unoccupied sediment patches were sources of
inorganic nutrients to the water column. Overall, Cassiopea greatly enhanced the spatial and temporal heterogeneity of benthic fluxes and processes by creating “hotspots” of high activities
which switched between being sources or sinks for oxygen and nutrients over diurnal irradiance cycles, as the metabolism of
the jellyfish swapped between heterotrophy and net autotrophy. 相似文献
13.
Gross photosynthesis and respiration rates of leaves at different canopy heights in a Rhizophora stylosa Griff. stand were measured monthly over 1 year at Manko Wetland, Okinawa Island, Japan, which is the northern limit of its
distribution. The light-saturated net photosynthesis rate for the leaves at the top of the canopy showed a maximum value of
17 μmol CO2 m−2 s−1 in warm season and a minimum value of 6 μmol CO2 m−2 s−1 in cold season. The light-saturated gross photosynthesis and dark respiration rates of the leaves existing at the top of the
canopy were 2−7 times and 3–16 times, respectively, those of leaves at the bottom of the canopy throughout the year. The light
compensation point of leaves showed maximum and minimum peaks in warm season and cold season, respectively. The annual canopy
gross photosynthesis, foliage respiration, and surplus production were estimated as 117, 49, and 68 t CO2 ha−1 year−1, respectively. The energy efficiency of the annual canopy gross photosynthesis was 2.5%. The gross primary production GPP fell near the regression curve of GPP on the product of leaf area index and warmth index, the regression curve which was established for forests in the Western
Pacific with humid climates. 相似文献
14.
Romain Fromanger S. E. Guillouet J. L. Uribelarrea C. Molina-Jouve X. Cameleyre 《Journal of industrial microbiology & biotechnology》2010,37(5):437-445
Carbon distribution and kinetics of Candida shehatae were studied in fed-batch fermentation with xylose or glucose (separately) as the carbon source in mineral medium. The fermentations were carried out in two phases, an aerobic phase dedicated to growth followed by an oxygen limitation phase dedicated to ethanol production. Oxygen limitation was quantified with an average specific oxygen uptake rate (OUR) varying between 0.30 and 2.48 mmolO2 g dry cell weight (DCW)?1 h?1, the maximum value before the aerobic shift. The relations among respiration, growth, ethanol production and polyol production were investigated. It appeared that ethanol was produced to provide energy, and polyols (arabitol, ribitol, glycerol and xylitol) were produced to reoxidize NADH from assimilatory reactions and from the co-factor imbalance of the two-first enzymatic steps of xylose uptake. Hence, to manage carbon flux to ethanol production, oxygen limitation was a major controlled parameter; an oxygen limitation corresponding to an average specific OUR of 1.19 mmolO2 g DCW?1 h?1 allowed maximization of the ethanol yield over xylose (0.327 g g?1), the average productivity (2.2 g l?1 h?1) and the ethanol final titer (48.81 g l?1). For glucose fermentation, the ethanol yield over glucose was the highest (0.411 g g?1) when the specific OUR was low, corresponding to an average specific OUR of 0.30 mmolO2 g DCW?1 h?1, whereas the average ethanol productivity and ethanol final titer reached the maximum values of 1.81 g l?1 h?1 and 54.19 g l?1 when the specific OUR was the highest. 相似文献
15.
Klaus S. Larsen Andreas Ibrom Claus Beier Sven Jonasson Anders Michelsen 《Biogeochemistry》2007,85(2):201-213
We measured net ecosystem CO2 flux (F
n) and ecosystem respiration (R
E), and estimated gross ecosystem photosynthesis (P
g) by difference, for two years in a temperate heath ecosystem using a chamber method. The exchange rates of carbon were high
and of similar magnitude as for productive forest ecosystems with a net ecosystem carbon gain during the second year of 293 ± 11 g C m−2 year−1 showing that the carbon sink strength of heather-dominated ecosystems may be considerable when C. vulgaris is in the building phase of its life cycle. The estimated gross ecosystem photosynthesis and ecosystem respiration from October
to March was 22% and 30% of annual flux, respectively, suggesting that both cold-season carbon gain and loss were important
in the annual carbon cycle of the ecosystem. Model fit of R
E of a classic, first-order exponential equation related to temperature (second year; R
2 = 0.65) was improved when the P
g rate was incorporated into the model (second year; R
2 = 0.79), suggesting that daytime R
E increased with increasing photosynthesis. Furthermore, the temperature sensitivity of R
E decreased from apparent Q
10 values of 3.3 to 3.9 by the classic equation to a more realistic Q
10 of 2.5 by the modified model. The model introduces R
photo, which describes the part of respiration being tightly coupled to the photosynthetic rate. It makes up 5% of the assimilated
carbon dioxide flux at 0°C and 35% at 20°C implying a high sensitivity of respiration to photosynthesis during summer. The
simple model provides an easily applied, non-intrusive tool for investigating seasonal trends in the relationship between
ecosystem carbon sequestration and respiration. 相似文献
16.
Knowledge of how energetic parameters relate to fluctuating factors in the natural habitat is necessary when evaluating the
role of gelatinous zooplankton in the carbon flow of coastal waters. In laboratory experiments, we assessed feeding, respiration
and growth of the ctenophore, Pleurobrachia pileus, and constructed carbon budgets. Clearance rates (F, l d−1) of laboratory-reared Acartia tonsa as prey increased as a function of ctenophore polar length (L, mm) as F = 0.17L
1.9. For ctenophores larger than about 11 mm, clearance rate was depressed in containers of 30–50 l volume. Clearance rates on
field-collected prey were highest on the copepod, Centropages typicus, intermediate on the cladoceran, Evadne
nordmanni and low on the copepods, Acartia clausi and Temora longicornis. Specific growth rates of 8–10 mm P. pileus increased with increasing prey concentrations to a maximum of 0.09 d−1 attained at prey carbon densities of 40 and 100 μg C l−1 of Artemia salina and A. tonsa, respectively. Weight-specific respiration rates increased hyperbolically with prey concentration. From experiments in which
growth, ingestion and respiration were measured simultaneously, a carbon budget was constructed for individuals growing at
maximum rates; from the measured parameters, the assimilation efficiency and net growth efficiency were estimated to be 22
and 37%, respectively. We conclude that the predation rates of P. pileus depend on ctenophore size, prey species, prey density and experimental container volume. Because the specific growth rates,
respiration, assimilation and net growth efficiencies all were affected by food availability, knowledge of the ambient prey
field is critical when evaluating the role of P.
pileus in the carbon flow in coastal waters. 相似文献
17.
Kazuharu Ogawa Akio Furukawa Akio Hagihara Ahmad Makmom Abdullah Muhamad Awang 《Trees - Structure and Function》1995,9(5):241-246
We examined the in situ CO2 gas-exchange of fruits of a tropical tree, Durio zibethinus Murray, growing in an experimental field station of the Universiti Pertanian Malaysia. Day and night dark respiration rates were exponentially related to air temperature. The temperature dependent dark respiration rate showed a clockwise loop as time progressed from morning to night, and the rate was higher in the daytime than at night. The gross photosynthetic rate was estimated by summing the rates of daytime dark respiration and net photosynthesis. Photosynthetic CO2 refixation, which is defined as the ratio of gross photosynthetic rate to dark respiration rate in the daytime, ranged between 15 and 45%. The photosynthetic CO2 refixation increased rapidly as the temperature increased in the lower range of air temperature T
c (T
c <28.5 °C), while it decreased gradually as the temperature increased in the higher range (T
c 28.5 °C). Light dependence of photosynthetic CO2 refixation was approximated by a hyperbolic formula, where light saturation was achieved at 100 mol m–2 s–1 and the asymptotic CO2 refixation was determined to be 37.4%. The estimated gross photosynthesis and dark respiration per day were 1.15 and 4.90 g CO2 fruit–1, respectively. Thus the CO2 refixation reduced the respiration loss per day by 23%. The effect of fruit size on night respiration rate satisfied a power function, where the exponent was larger than unity. 相似文献
18.
Stöckmann C Maier U Anderlei T Knocke C Gellissen G Büchs J 《Journal of industrial microbiology & biotechnology》2003,30(10):613-622
Screening cultures are usually non-monitored and non-controlled due to a lack of appropriate measuring techniques. A new device for online measurement of oxygen transfer rate (OTR) in shaking-flask cultures was used for monitoring the screening of Hansenula polymorpha. A shaking frequency of 300 rpm and a filling volume of 20 ml in 250-ml flasks ensured a sufficient oxygen transfer capacity of 0.032 mol (l h)–1 and thus a respiration not limited by oxygen. Medium buffered with 0.01 mol phosphate l–1 (pH 6.0) resulted in pH-inhibited respiration, whereas buffering with 0.12 mol phosphate l–1 (pH 4.1) resulted in respiration that was not inhibited by pH. The ammonium demand was balanced by establishing fixed relations between oxygen, ammonium, and glycerol consumption with 0.245±0.015 mol ammonium per mol glycerol. Plate precultures with complex glucose medium reduced the specific growth rate coefficient to 0.18 h–1 in subsequent cultures with minimal glycerol medium. The specific growth rate coefficient increased to 0.26 h–1 when exponentially growing precultures with minimal glycerol medium were used for inoculation. Changes in biomass, glycerol, ammonium, and pH over time were simulated on the basis of oxygen consumption. 相似文献
19.
Johnston W Cooney M Schorlemmer A Pohl S Karl DM Bidigare R 《Bioprocess and biosystems engineering》2005,27(3):163-174
A carbon mass balance methodology employing minimal measurements was applied to heterotrophic and photoheterotrophic marine bacteria grown under constant dilution and exposed to 12-h intervals of light or darkness. Carbon mass balance calculations using measurements taken every 3 h closed to within 93–103% using dissolved organic carbon, biomass carbon and CO2 production data only, indicating that background interference from dissolved inorganic carbon variations in the amended seawater medium was not significant. Neither strain was observed to sustain a net CO2 fixation using paramagnetic measurement of oxygen uptake rates (OUR), indicating a need for more sensitive on-line measurement techniques for OUR. Photoheterotrophic growth demonstrated lower carbon-mole biomass yields (0.41±0.026 vs. 0.64±0.013 mol mol–1) despite higher specific glucose uptake rates (0.025 vs. 0.02 mol mol–1 h–1), suggesting that bioreactor-based study of marine bacteria can present growth modes that are different from those encountered in the marine environment. 相似文献
20.
Pseudomonas putida and Pseudomonas fluorescens present as a coculture were studied for their abilities to degrade benzene, toluene, ethylbenzene, and xylenes (collectively known as BTEX) under various growth conditions. The coculture effectively degraded various concentrations of BTEX as sole carbon sources. However, all BTEX compounds showed substrate inhibition to the bacteria, in terms of specific growth, degradation rate, and cell net yield. Cell growth was completely inhibited at 500mgl–1 of benzene, 600mgl–1 of o-xylene, and 1000mgl–1 of toluene. Without aeration, aerobic biodegradation of BTEX required additional oxygen provided as hydrogen peroxide in the medium. Under hypoxic conditions, however, nitrate could be used as an alternative electron acceptor for BTEX biodegradation when oxygen was limited and denitrification took place in the culture. The carbon mass balance study confirmed that benzene and toluene were completely mineralized to CO2 and H2O without producing any identifiable intermediate metabolites. 相似文献