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1.
Phyto/zooplankton composition, chlorophyll a, and some water quality parameters were investigated in a spring-originated pond in Central Anatolia between February 2001
and January 2002. Water temperature, pH, dissolved oxygen, Secchi depth, total and calcium hardness, nitrate-nitrogen, nitrite-nitrogen,
ammonia-nitrogen, total phosphorus, and soluble reactive phosphorus levels were analyzed. A total of 49 species belonging
to Bacillariophyceae, Chlorophyceae, Cyanophyceae, Cryptophyceae, and Dinophyceae were identified. The highest phytoplankton
abundance was found in August, whereas the lowest was determined in January. Phytoplankton abundance increased from February
to August and declined in the following months. The Bacillariophyceae were dominant in the phytoplankton community. A total
of 21 species of Rotifera, 2 species of Cladocera, and 1 genus of Copepoda were found. The zooplankton community was dominated
by Rotifera. The highest abundance of zooplankton was recorded in July and the lowest value in November. The annual mean concentration
of chlorophyll a was measured as 1.90 μg l−1. In spite of these eutrophic levels (mean values of total phosphorus and nitrate-nitrogen: 0.069 mg P l−1 and 0.68 mg N l−1), phytoplankton cannot grow satisfactorily because of the short water retention time (0.6 day−1). The shallowness of the pond together with the low phytoplankton biomass and the high concentrations of nutrients are discussed. 相似文献
2.
In order to provide a better understanding of the dynamics of phytoplankton in the coastal regions of high latitudes, a study
was carried out to estimate the dynamics of carbon biomass of autotrophic and heterotrophic algal groups over the austral
spring-summer 1997/1998 period. At a fixed station located in the central basin (Paso Ancho) of the Straits of Magellan (53°S),
surface water samples were collected at least once a week from September 1997 (early spring) to March 1998 (late summer).
Quantitative analysis of biomass of phytoplankton was estimated from geometric volumes, using non-linear equations, and converted
to biomass. The pattern of chlorophyll a showed a strong temporal variability, with maximum values (mean 2.8 mg m−3) at the austral spring phytoplankton increase or bloom (October/November) and minimum values during early spring (September:
<0.5 mg m−3) and summer (January/March: 0.5–1.0 mg m−3). During the spring bloom, diatoms made up to 90% of the total phytoplankton carbon (0.01–189 μg l−1), followed by a maximum of thecate dinoflagellates (0.08–34 μg l−1), and sporadic high biomass of phytoflagellates during summer. Heterotrophic algal groups such as Gymnodinium and Gyrodinium spp. dominated (70%, in the 5- to 25-μm size range) shortly before the main diatom bloom, and small peaks were observed within
spring and early summer periods (0–0.4 μg l−1). Phytoflagellates dominated earlier (spring) with higher carbon biomass (8 μg l−1) and post-bloom periods (summer) when carbon biomass ranged between 1 and 4 μg l−1.
Accepted: 6 September 2000 相似文献
3.
Xiuyun Cao Chunlei Song Yiyong Zhou Alena Štrojsová Petr Znachor Eliška Zapomělová Jaroslav Vrba 《Limnology》2009,10(2):95-104
Extracellular phosphatases are an important part of the phosphorus cycle in aquatic environments. Phosphatase activity (PA)
in plankton was studied in seven subtropical shallow lakes of different exploitation management and trophic status in the
urban area of Wuhan City. Bulk PA was rather high (range 1.1–11 μmol l−1 h−1), although concentrations of soluble reactive phosphorus (SRP) were also high (range 27 μg P l−1 to ~1.5 mg P l−1) in all lakes. Cell-associated extracellular PA in phytoplankton was detected using the fluorescence-labelled enzyme activity
technique. Phytoplankton species partly contributed to the bulk PA. We found explicit differences in the presence of cell-associated
phosphatase within the main phytoplankton groups; species belonging to Chlorophyta and Dinophyta were regularly phosphatase-positive,
while Cyanophyta and Bacillariophyceae were phosphatase-negative in all but one case. Furthermore, there is a certain potential
of extracellular phosphatases produced by heterotrophic nanoflagellates in most of the lakes. This new finding compromises
the ‘traditional’ interpretation of bulk phosphatase data as being due to overall phytoplankton or bacterial P regeneration. 相似文献
4.
During January 1989, phytoplankton biomass and species composition were studied in a north / south transect at the Weddell / Scotia
Confluence (47°W), between 57° and 61°30′S. Results showed a diatom bloom in the Scotia Sea (chlorophyll a 1.9 μg l−1, particulate organic carbon 239 μg l−1), dominated by Fragilariopsis cylindrus, Dactyliosolen antarcticus and Chaetoceros dichaeta. Low chlorophyll a / phaeopigments ratios (about 1.4) and silicate concentrations (15 μmol l−1) suggested that this was an advanced bloom phase, probably linked to high grazing pressure. Minimum chlorophyll a values of 0.1–0.2 μg l−1 and particulate organic carbon 46 μg l−1 were found at the Weddell / Scotia Front and in a subsurface layer of the Weddell Sea Water. In the southern part of the
transect (61°30′S), in the Weddell Sea, a second surface maximum was found (chlorophyll a 0.9 μg l−1, particulate organic carbon 120 μg l−1), but with a different species composition, with Cryptomonas sp. dominant. Our results show a succession within the diatom community in the Weddell / Scotia Confluence Waters when comparing
the three EPOS legs. In the Weddell Sea from spring to summer, nanoflagellates, with only a minor contribution from diatoms,
persist over a long period with little change in the community structure. We suggest that the frontal system, together with
the receding ice edge and the grazing pressure of either krill or protozooplankton, are mainly responsible for the phytoplankton
distribution patterns found.
Received: 3 July 1996 / Accepted: 3 November 1996 相似文献
5.
Luz Allende Guillermo Tell Horacio Zagarese Ana Torremorell Gonzalo Pérez José Bustingorry Roberto Escaray Irina Izaguirre 《Hydrobiologia》2009,624(1):45-60
Shallow lakes often alternate between two possible states: one clear with submerged macrophytes, and another one turbid, dominated
by phytoplankton. A third type of shallow lakes, the inorganic turbid, result from high contents of suspended inorganic material,
and is characterized by low phytoplankton biomass and macrophytes absence. In our survey, the structure and photosynthetic
properties (based on 14C method) of phytoplankton were related to environmental conditions in these three types of lakes in the Pampa Plain. The
underwater light climate was characterized. Clear-vegetated lakes were more transparent (K
d 4.5–7.7 m−1), had high DOC concentrations (>45 mg l−1), low phytoplankton Chl a (1.6–2.7 μg l−1) dominated by nanoflagellates. Phytoplankton productivity and photosynthetic efficiency (α ~ 0.03 mgC mgChla
−1 h−1 W−1 m2) were relatively low. Inorganic-turbid lakes showed highest K
d values (59.8–61.4 m−1), lowest phytoplankton densities (dominated by Bacillariophyta), and Chl a ranged from 14.6 to 18.3 μg l−1. Phytoplankton-turbid lakes showed, in general, high K
d (4.9–58.5 m−1) due to their high phytoplankton abundances. These lakes exhibited the highest Chl a values (14.2–125.7 μg l−1), and the highest productivities and efficiencies (maximum 0.56 mgC mgChla
−1 h−1 W−1 m2). Autotrophic picoplankton abundance, dominated by ficocianine-rich picocyanobacteria, differed among the shallow lakes independently
of their type (0.086 × 105–41.7 × 105 cells ml−1). This article provides a complete characterization of phytoplankton structure (all size fractions), and primary production
of the three types of lakes from the Pampa Plain, one of the richest areas in shallow lakes from South America.
Handling editor: J. Padisak 相似文献
6.
Batch and continuous cultivation of Anaerobiospirillum succiniciproducens for the production of succinic acid from whey 总被引:3,自引:0,他引:3
Batch and continuous cultivation of Anaerobiospirillum succiniciproducens were systematically studied for the production of succinic acid from whey. Addition of 2.5 g l−1 yeast extract and 2.5 g l−1 polypeptone per 10 g l−1 whey was most effective for succinic acid production from both treated and nontreated whey. When 20 g l−1 nontreated whey and 7 g l−1 glucose were used as cosubstrates, the yield and productivity of succinic acid reached at the end of fermentation were 95%
and 0.46 g (l h)−1, respectively. These values were higher than those obtained using nontreated whey alone [93% and 0.24 g (l h)−1 for 20 g l−1 whey]. Continuous fermentation of A. succiniciproducens at an optimal dilution rate resulted in the production of succinic acid with high productivity [1.35 g (l h)−1], high conversion yield (93%), and higher ratio of succinic acid to acetic acid (5.1:1) from nontreated whey.
Received: 23 July 1999 / Received revision: 17 November 1999 / Accepted: 24 December 1999 相似文献
7.
Numerous studies have demonstrated alternative regimes in shallow lake ecosystems around the world, with one state dominated
by submerged macrophytes and the other by phytoplankton. However, the stability of each regime, and thresholds at which lakes
shift to the alternative regime, are poorly known. We used a cross-sectional analysis of 72 shallow lakes located in prairie
and parkland areas of Minnesota, USA, during 2005 and 2006 to assess the occurrence of alternative regimes and shifts between
them. Cluster analysis revealed two distinct groups of lakes characterized not only by different macrophyte abundance and
chlorophyll a levels but also by different total phosphorus–chlorophyll a relationships. Thirty-nine lakes were macrophyte- and 23 lakes phytoplankton-dominated in both years, whereas 10 sites shifted
sharply between those regimes. We failed to detect a universal shifting threshold in terms of chlorophyll a or total phosphorus. However, 95% of the lakes with chlorophyll a concentrations less than 22 μg l−1 were in a clear-water regime, whereas 95% of the lakes with chlorophyll a higher than 31 μg l−1 were in a turbid regime. Total phosphorus less than 62 μg l−1 was an accurate predictor of lakes in a stable clear-water regime, whereas a large change in biomass of planktivores and
benthivores between years was the only variable weakly related to regime shifts. Our results support the theoretical prediction
that regime thresholds vary among lakes. We recommend that lake managers focus on improving resilience of clear regimes in
shallow lakes by reducing nutrient loading, rather than attempting to identify and manage complex triggers of regime shifts.
Author contributions KDZ, MAH, BRH, and MLK all contributed to the design of the study, performed the research, analyzed data, and helped write
the article. 相似文献
8.
The objective of this study is to describe the biogeochemical characteristics in the waters of Mongolian lakes, particularly
those related to parameters limiting phytoplankton growth and the trophic state. Investigations into the distribution of chemical
and biological parameters were carried out in the following 18 lakes: Har Us, Har, Hovsgol, Achit, Dalai, Bayan, Tolbo, Holboo,
Bust, Sangiyn Dalai, Tunamal, Dorgon, Uureg, Telmen, Hyargas, Uvs, Erkhel and Oygon, all of which showed a wide range of salinity
between 0.16 and 24.9 g l−1. Lake water was classified into four types: six fresh (less than 0.5 g l−1 salinity), three subsaline (0.5–3 g l−1), seven hyposaline (3–20 g l−1) and two mesosaline (20–50 g l−1) lakes. Predominant cations and anions in the order of dominance were Ca, Mg > Na > K and HCO3 > SO4, Cl in freshwater lakes, Na > Mg > Ca, K and HCO3, Cl > SO4 in subsaline lakes, and Na > Mg > K, Ca and Cl, SO4 > HCO3 in hyposaline and mesosaline lakes. Nitrogenous and phosphorus nutrients in the waters were low, seemingly caused by the
low loads from their watersheds, where the ground was free of vegetation with an extremely low level of human activity. The
present investigations revealed some 234 taxa of phytoplankton and 38 of zooplankton. The PC:PN:PP stoichiometric ratio by
weight was (22–202):(3–27):1. Phosphorus was assessed as the potential limiting parameter in eight lakes, nitrogen in six
and both nutrients in four others. Twelve lakes showed an oligotrophic character, while six were mesotrophic type. The six
oligotrophic lakes seemed to be subject to phosphorus limiting phytoplankton growth, four to nitrogen and two to both limitations.
In the mesotrophic lakes, on the other hand, phosphorus limitation was verified in two lakes, nitrogen in two others and both
in two lakes. 相似文献
9.
Inhibition of Clostridium butyricum by 1,3-propanediol and diols during glycerol fermentation 总被引:3,自引:0,他引:3
1,3-Propanediol inhibition during glycerol fermentation to 1,3-propanediol by Clostridium butyricum CNCM 1211 has been studied. The initial concentration of the 1,3-propanediol affected the growth of the bacterium more than
the glycerol fermentation. μ
max was inversely proportional to the initial concentration of 1,3-propanediol (0–65 g l−1). For glycerol at 20 g l−1, the growth and fermentation were completely stopped at an initial 1,3-propanediol concentration of 65 g l−1. However, for an initial 1,3-propanediol concentration of 50 g l−1 and glycerol at 70 g l−1, the final concentration (initial and produced) of 1,3-propanediol reached 83.7 g l−1(1.1 M), with complete consumption of the glycerol. Therefore, during the fermentation, the strain tolerated a 1,3-propanediol
concentration higher than the initial inhibitory concentration (65 g l−1). The addition of 1,2-propanediol or 2,3-butanediol (50 g l−1) in the presence of glycerol (50–100 g l−1), showed that 2-diols reduced the μ
max in a similar way to 1,3-propanediol. The measurement of the osmotic pressure of glycerol solutions, diols and diol/glycerol
mixtures did not indicate any differences between these compounds. The hypothesis of diol inhibition was discussed. Taking
into account the strain tolerance of highly concentrated 1,3-propanediol during fermentation, the fermentation processes for
optimising production were considered.
Received: 15 November 1999 / Revision received: 1 February 2000 / Accepted: 4 February 2000 相似文献
10.
M. De Pirro G. Santini G. Chelazzi 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1999,169(7):501-506
Cardiac activity of two Mediterranean limpets was tested at different salinities. Patella caerulea inhabits the lower midlittoral where it is exposed to variations in salinity, while P. aspera experiences more stable salinity conditions in the infralittoral fringe. When exposed to moderate hypo- and hypersalinity
(23 g l−1 and 43 g l−1) for 24 min, P. caerulea showed no significant variation in heart rate with respect to the control salinity (33 g l−1), while P. aspera exhibited a significant increase in heart rate in both conditions. This suggests a rise in metabolic rate due to activation
of behavioural responses or physiological regulation. When exposed to extremely low salinity (3 g l−1) for 24 min, heart contractions ceased in most specimens of P. caerulea. A smaller number of specimens also displayed cessation of heart beat when exposed to extremely high salinity (63 g l−1). The heart beat resumed quickly in all specimens when they were returned to control salinity conditions. In contrast, cardiac
activity was not interrupted in any of the P. aspera specimens at the 3 g l−1 and 63 g l−1 salinity levels, but strong bradycardia was evident. Contractile activity of the heart ceased in all specimens of P. caerulea and P. aspera when they were exposed to prolonged hypo-osmotic stress (3 g l−1 for 24 h). This acardia was largely reversible in P. caerulea, but most specimens of P. aspera did not recover from the treatment.
Accepted: 3 July 1999 相似文献
11.
A two-phase aqueous/organic partitioning bioreactor scheme was used to degrade mixtures of toluene and benzene, and toluene
and p-xylene, using simultaneous and sequential feeding strategies. The aqueous phase of the partitioning bioreactor contained
Pseudomonas sp. ATCC 55595, an organism able to degrade benzene, toluene and p-xylene simultaneously. An industrial grade of oleyl alcohol served as the organic phase. In each experiment, the organic
phase of the bioreactor was loaded with 10.15 g toluene, and either 2.0 g benzene or 2.1 g p-xylene. The resulting aqueous phase concentrations were 50 mg/l, 25 mg/l and 8 mg/l toluene, benzene and p-xylene respectively. The simultaneous fermentation of benzene and toluene consumed these compounds at volumetric rates of
0.024 g l−1 h−1 and 0.067 g l−1 h−1, respectively. The simultaneous fermentation of toluene and p-xylene consumed these xenobiotics at volumetric rates of 0.066 g l−1 h−1 and 0.018 g l−1 h−1, respectively. A sequential feeding strategy was employed in which toluene was added initially, but the benzene or p-xylene aliquot was added only after the cells had consumed half of the initial toluene concentration. This strategy was shown
to improve overall degradation rates, and to reduce the stress on the microorganisms. In the sequential fermentation of benzene
and toluene, the volumetric degradation rates were 0.056 g l−1 h−1 and 0.079 g l−1 h−1, respectively. In the toluene/p-xylene sequential fermentation, the initial toluene load was consumed before the p-xylene aliquot was consumed. After 12 h in which no p-xylene degradation was observed, a 4.0-g toluene aliquot was added, and p-xylene degradation resumed. Excluding that 12-h period, the microbes consumed toluene and p-xylene at volumetric rates of 0.074 g l−1 h−1 and 0.025 g l−1 h−1, respectively. Oxygen limitation occurred in all fermentations during the rapid growth phase.
Received: 16 November 1998 / Received revision: 29 March 1999 / Accepted: 9 April 1999 相似文献
12.
Takashi Nemoto Taisuke Watanabe Yutaka Mizogami Jun-ichi Maruyama Katsuhiko Kitamoto 《Applied microbiology and biotechnology》2009,82(6):1105-1114
The recombinant Pichia pastoris harboring an improved methionine adenosyltransferase (MAT) shuffled gene was employed to biosynthesize S-adenosyl-l-methionine (SAM). Two l-methionine (l-Met) addition strategies were used to supply the precursor: the batch addition strategy (l-Met was added separately at three time points) and the continuous feeding strategies (l-Met was fed continuously at the rate of 0.1, 0.2, and 0.5 g l−1 h−1, respectively). SAM accumulation, l-Met conversion rate, and SAM productivity with the continuous feeding strategies were all improved over the batch addition
strategy, which reached 8.46 ± 0.31 g l−1, 41.7 ± 1.4%, and 0.18 ± 0.01 g l−1 h−1 with the best continuous feeding strategy (0.2 g l−1 h−1), respectively. The bottleneck for SAM production with the low l-Met feeding rate (0.1 g L−1 h−1) was the insufficient l-Met supply. The analysis of the key enzyme activities indicated that the tricarboxylic acid cycle and glycolytic pathway
were reduced with the increasing l-Met feeding rate, which decreased the adenosine triphosphate (ATP) synthesis. The MAT activity also decreased as the l-Met feeding rate rose. The reduced ATP synthesis and MAT activity were probably the reason for the low SAM accumulation when
the l-Met feeding rate reached 0.5 g l−1 h−1. 相似文献
13.
Biosurfactants containing rhamnose and β-hydroxydecanoic acid and called rhamnolipids are reviewed with respect to microbial
producers, their physiological role, biosynthesis and genetics, and especially their microbial overproduction, physicochemical
properties and potential applications. With Pseudomonas species, more than 100 g l−1 rhamnolipids were produced from 160 g l−1 soybean oil at a volumetric productivity of 0.4 g l−1 h−1. The individual rhamnolipids are able to lower the surface tension of water from 72 mN m−1 to 25–30 mN m−1 at concentrations of 10–200 mg l−1. After initial testing, rhamnolipids seem to have potential applications in combating marine oil pollution, removing oil
from sand and in combating zoosporic phytopathogens. Rhamnolipids are also a source of l-rhamnose, which is already used for the industrial production of high-quality flavor components.
Received: 1 July 1998 / Received revision: 11 September 1998 / Accepted: 13 September 1998 相似文献
14.
Continuous production of l(+)-lactic acid by Lactobacillus casei in two-stage systems 总被引:2,自引:0,他引:2
Bruno-Bárcena JM Ragout AL Córdoba PR Siñeriz F 《Applied microbiology and biotechnology》1999,51(3):316-324
A two-stage two-stream chemostat system and a two-stage two-stream immobilized upflow packed-bed reactor system were used
for the study of lactic acid production by Lactobacillus casei subsp casei. A mixing ratio of D
12/D
2 = 0.5 (D = dilution rate) resulted in optimum production, making it possible to generate continuously a broth with high lactic acid
concentration (48 g l−1) and with a lowered overall content of initial yeast extract (5 g l−1), half the concentration supplied in the one-step process. In the two-stage chemostat system, with the first stage at pH
5.5 and 37 °C and a second stage at pH 6.0, a temperature change from 40 °C to 45 °C in the second stage resulted in a 100%
substrate consumption at an overall dilution rate of 0.05 h−1. To increase the cell mass in the system, an adhesive strain of L. casei was used to inoculate two packed-bed reactors, which operated with two mixed feedstock streams at the optimal conditions
found above. Lactic acid fermentation started after a lag period of cell growth over foam glass particles. No significant
amount of free cells, compared with those adhering to the glass foam, was observed during continuous lactic acid production.
The extreme values, 57.5 g l−1 for lactic acid concentration and 9.72 g l−1 h−1 for the volumetric productivity, in upflow packed-bed reactors were higher than those obtained for free cells (48 g l−1 and 2.42 g l−1 h−1) respectively and the highest overall l(+)-lactic acid purity (96.8%) was obtained in the two-chemostat system as compared with the immobilized-cell reactors (93%).
Received: 4 December 1997 / Received revision: 23 February 1998 / Accepted: 14 March 1998 相似文献
15.
Simultaneous bioconversion of glucose and xylose to ethanol by Saccharomyces cerevisiae in the presence of xylose isomerase 总被引:3,自引:0,他引:3
Simultaneous isomerisation and fermentation (SIF) of xylose and simultaneous isomerisation and cofermentation (SICF) of a
glucose/xylose mixture was carried out by Saccharomyces cerevisiae in the presence of xylose isomerase. The SIF of 50 g l−1 xylose gave an ethanol concentration and metabolic yield of 7.5 g l−1 and 0.36 g (g xylose consumed)−1. These parameters improved to 13.4 g l−1 and 0.40 respectively, when borate was added to the medium. The SICF of a mixture of 50 g l−1 glucose and 50 g l−1 xylose gave an ethanol concentration and metabolic yield of 29.8 g l−1 and 0.42 respectively, in the presence of borate. Temperature modulation from 30 °C to 35 °C during fermentation further
enhanced the above parameters to 39 g l−1 and 0.45 respectively. The approach was extended to the bioconversion of sugars present in a real lignocellulose hydrolysate
(peanut-shell hydrolysate) to ethanol, with a fairly good yield.
Received: 14 May 1999 / Received revision: 27 September 1999 / Accepted: 2 October 1999 相似文献
16.
Smita Srivastava Ashok Kumar Srivastava 《In vitro cellular & developmental biology. Plant》2012,48(1):73-84
Azadirachtin, a well-known biopesticide, is a secondary metabolite extracted from the seeds of Azadirachta indica. In the present study, azadirachtin was produced in hairy roots of A. indica, generated by Agrobacterium rhizogenes-mediated transformation of leaf explants. Liquid cultures of A. indica hairy roots were developed with a liquid-to-flask volume ratio of 0.15. The kinetics of growth and azadirachtin production
were established in a basal plant growth medium containing MS medium major and minor salts, Gamborg’s medium vitamins, and
30 g l−1 sucrose. The highest azadirachtin accumulation in the hairy roots (up to 3.3 mg g−1) and azadirachtin production (∼44 mg l−1) was obtained on Day 25 of the growth cycle, with a biomass production of 13.3 g l−1 dry weight. To enhance the production of azadirachtin, a Plackett–Burman experimental design protocol was used to identify
key medium nutrients and concentrations to support high root biomass production and azadirachtin accumulation in hairy roots.
The optimal nutrients and concentrations were as follows: 40 g l−1 sucrose, 0.19 g l−1 potassium dihydrogen phosphate, 3.1 g l−1 potassium nitrate, and 0.41 g l−1 magnesium sulfate. Concentrations were determined by a central composite design protocol and verified in shake-flask cultivation.
The optimized medium composition yielded a root biomass production of 14.2 g l−1 and azadirachtin accumulation of 5.2 mg g−1, which was equivalent to an overall azadirachtin production of 73.84 mg l−1, 68% more than that obtained under non-optimized conditions. 相似文献
17.
E. J. Bormann M. Leißner M. Roth B. Beer K. Metzner 《Applied microbiology and biotechnology》1998,50(5):604-607
Polyhydroxybutyrate (PHB) was produced by Ralstonia eutropha DSM 11348 (formerly Alicaligenes eutrophus) in media containing 20–30 g l−1 casein peptone or casamino acids as sole sources of nitrogen. In fermentations using media based on casein peptone, permanent
growth up to a cell dry mass of 65 g l−1 was observed. PHB accumulated in cells up to 60%–80% of dry weight. The lowest yields were found in media without any trace
elements or with casamino acids added only. The residual cell dry masses were limited to 10–15 g l−1 and did not contain PHB. The highest productivity amounted to 1.2 g PHB l−1 h−1. The mean molecular mass of the biopolymer was determined as 750 kDa. The proportion of polyhydroxyvalerate was less than
0.2% in PHB. The bioprocess was scaled up to a 300-l plant. During a fermentation time of 39 h the cells accumulated PHB to
78% w/w. The productivity was 0.98 g PHB l−1 h1.
Received: 8 July 1998 / Accepted: 26 August 1998 相似文献
18.
The principal environmental factors influencing the seasonal dynamics of phytoplankton were examined from September 1997 to
July 1998 in three stations along a 26-km stretch of the lowland course of River Adige (northeast Italy). Nutrient concentrations
did not appear to be limiting for the phytoplankton growth. Annual minimum concentrations of reactive and total phosphorus,
and dissolved inorganic nitrogen were 22 μg P l−1, 63 μg P l−1 and 0.9 mg N l−1, respectively. The most critical forcing factors were physical variables, mainly water discharge and other variables related
to hydrology, i.e. suspended solids and turbidity, which acted negatively and synchronously by diluting phytoplankton cells
and decreasing light availability. Higher algal biomass was recorded in early spring, in conditions of lower flow velocity
and increasing water temperature. In late spring and summer, higher water discharge caused a decrease in phytoplankton biomass.
Conversely, low algal biomass in late autumn and winter, during low discharge, was mainly related to low water temperatures
and shorter photoperiod. Physical constraints had a significant and measurable effect not only on the development of total
biomass, but also on the temporal dynamics of the phytoplankton community. Abiotic and biotic variables showed a comparable
temporal development in the three sampling stations. The small number of instances of spatial differences in phytoplankton
abundance during the period of lower flow velocity were related to the increasing importance of biological processes and accumulation
of phytoplankton biomass. 相似文献
19.
Development of a cost-effective glucose-corn steep medium for production of butanol by Clostridium beijerinckii 总被引:1,自引:0,他引:1
M Parekh J Formanek H P Blaschek 《Journal of industrial microbiology & biotechnology》1998,21(4-5):187-191
Corn steep water (CSW) medium (1.6% solids plus 6% glucose) was evaluated for growth and butanol production by Clostridium beijerinckii NCIMB 8052 wild-type and hyper-amylolytic, hyper-butanol-producing mutant strain BA101. CSW alone was not a suitable substrate,
whereas addition of glucose supported growth and butanol production by both strains. In a batch-scale fermentation using an
optimized 6% glucose-1.6% solids CSW medium, C. beijerinckii NCIMB 8052 and strain BA101 produced 10.7 g L−1 and 14.5 g L−1 of butanol, respectively. The total solvents (acetone, butanol, and ethanol) produced by C. beijerinckii NCIMB 8052 and strain BA101 were 14 g L−1 and 20 g L−1, respectively. Initial fermentation in small-scale flasks containing 6% maltodextrin-1.6% solids concentration CSW medium
resulted in 6 g L−1 and 12.6 g L−1 of butanol production by C. beijerinckii NCIMB 8052 and strain BA101, respectively. CSW can serve as an economic source of nitrogen, vitamins, amino acids, minerals,
and other nutrients. Thus, it is feasible to use 6% glucose-1.6% solids CSW medium in place of semi-defined P2 medium.
Received 9 February 1998/ Accepted in revised form 1 September 1998 相似文献
20.
Our previous study showed that an activated-sludge process broke down at the phenol-loading rate of 1.5 g l−1 day−1, when non-flocculating bacteria (called R6T and R10) overgrew the sludge, resulting in a sludge washout. In this study, we
attempted to circumvent this breakdown problem by reclaiming the consortium structure. Activated sludge was fed phenol, and
the phenol-loading rate was increased stepwise from 0.5 g l−1 day−1 to 1.0 g l−1 day−1 and then to 1.5 g l−1 day−1. Either galactose or glucose (at 0.5 g l−1 day−1) was also supplied to the activated sludge from the phenol-loading rate of 1.0 g l−1 day−1. Pure culture experiments have suggested galactose to be a preferential substrate for a floc-forming bacterium (R6F) that
predominantly degrades phenol under low phenol-loading conditions. Supplying galactose allowed sustainment of the R6F population
and suppression of the overgrowth of R6T and R10 at the phenol-loading rate of 1.5 g l−1 day−1. This measure allowed the activated-sludge process to treat phenol at a phenol-loading rate up to 1.5 g l−1 day−1, although it broke down at 2.0 g l−1 day−1. In contrast, supplying glucose reduced the R6F population and allowed the activated-sludge process to break down at the
phenol-loading rate of 1.0 g l−1 day−1. This study demonstrated that reclamation of the activated-sludge consortium by selective biostimulation of the floc-forming
population improved the phenol-treating ability of the process.
Received: 13 January 2000 / Received revision: 10 March 2000 / Accepted: 7 April 2000 相似文献