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1.
Yoshihisa Ogawa Miki Akamatsu Yudai Hotta Akifumi Hosoda Hiroto Tamura 《Bioorganic & medicinal chemistry letters》2010,20(7):2111-2114
The effect of essential oils, such as raspberry ketone, on androgen (AR) receptor was investigated using a MDA-kb2 human breast cancer cell line for predicting potential AR activity. Among them, eugenol had the highest AR antagonistic activity with its IC50 value of 19 μM. Raspberry ketone, which has threefold higher anti-obese activity than that of capsaicin, also had AR antagonist activity with its IC50 value of 252 μM. Based on these findings, a more precise CoMFA model was proposed as follows: pIC50 [log (1/IC50)] = 3.77 + [CoMFA field terms] (n = 39, s = 0.249, r2 = 0.834, scv = 0.507, q2 = 0.311 (three components). 相似文献
2.
Narsimha Reddy Penthala Purushothama Rao Ponugoti Justin R. Nickell Agripina G. Deaciuc Linda P. Dwoskin Peter A. Crooks 《Bioorganic & medicinal chemistry letters》2013,23(11):3342-3345
Central heterocyclic ring size reduction from piperidinyl to pyrrolidinyl in the vesicular monoamine transporter-2 (VMAT2) inhibitor GZ-793A and its analogs resulted in novel N-propane-1,2(R)-diol analogs 11a–i. These compounds were evaluated for their affinity for the dihydrotetrabenazine (DTBZ) binding site on VMAT2 and for their ability to inhibit vesicular dopamine (DA) uptake. The 4-difluoromethoxyphenethyl analog 11f was the most potent inhibitor of [3H]-DTBZ binding (Ki = 560 nM), with 15-fold greater affinity for this site than GZ-793A (Ki = 8.29 μM). Analog 11f also showed similar potency of inhibition of [3H]-DA uptake into vesicles (Ki = 45 nM) compared to that for GZ-793A (Ki = 29 nM). Thus, 11f represents a new water-soluble inhibitor of VMAT function. 相似文献
3.
Andrea Ludwig Marty Matlock Brian E. Haggard Monty Matlock Eric Cummings 《Ecological Engineering》2008,32(2):178-186
The objective of the study was to identify nutrient impacts, if any, on stream periphyton growth in Black Bear Creek (north central Oklahoma) and its tributaries. Passive diffusion periphytometers were deployed at ten study sites within the Black Bear Creek basin to evaluate periphyton growth in response to nutrient enrichment. These sites were selected to represent a gradient of land uses, from predominantly agricultural to predominantly urban. Periphytometer treatments included phosphorus (P) (1.0 mg/L PO4-P, n = 10), nitrogen (N) (10.0 mg/L NO3-N, n = 10), N plus P (n = 10) and control (reverse osmosis-treated water, n = 10). Results indicated that average dissolved inorganic N (DIN, PQL = 0.04 mg/L) concentrations were significantly correlated (R2 = 0.63, p < 0.01) with chlorophyll a production on the periphytometer control treatments in the Black Bear Creek basin. Periphytic growth was nutrient-limited (increased chlorophyll a was measured on nutrient-enriched growth media) at four of the ten sites sampled; two sites were limited by N and two sites were co-limited by both N and P. The lotic ecosystem trophic status index (LETSI), the ratio of C to N + P chlorophyll a, was calculated to compare treatment responses across sites. At nutrient-limited sites, LETSI was positively correlated to ambient DIN values (R2 = 0.97, p < 0.01). However, some sites that were not nutrient-limited had ambient nutrient concentrations similar to sites with observed nutrient limitation, indicating other factors were limiting periphyton growth at those sites. 相似文献
4.
Retrieving leaf chlorophyll content at a range of spatio-temporal scales is central to monitoring vegetation productivity, identifying physiological stress and managing biological resources. However, estimating leaf chlorophyll over broad spatial extents using ground-based traditional methods is time and resource heavy. Satellite-derived spectral vegetation indices (VIs) are commonly used to estimate leaf chlorophyll content, however they are often developed and tested on broadleaf species. Relatively little research has assessed VIs for different leaf structures, particularly needle leaves which represent a large component of boreal forest and significant global ecosystems. This study tested the performance of 47 published VIs for estimating foliar chlorophyll content from different leaf and canopy structures (broadleaf and needle). Coniferous and deciduous sites were selected in Ontario, Canada, representing different dominant vegetation species (Picea mariana and Acer saccharum) and a variety of canopy structures. Leaf reflectance data was collected using an ASD Fieldspec Pro spectroradiometer (400–2500 nm) for over 300 leaf samples. Canopy reflectance data was acquired from the medium resolution imaging spectrometer (MERIS). At the canopy level, with both leaf types combined, the DD-index showed the strongest relationship with leaf chlorophyll (R2 = 0.78; RMSE = 3.56 μg/cm2), despite differences in leaf structure. For needleleaf trees alone the relationship with the top VI was weaker (D[red], R2 = 0.71; RMSE = 2.32 μg/cm2). A sensitivity study using simulated VIs from physically-modelled leaf (PROSPECT) and canopy (4-Scale) reflectance was performed in order to further investigate these results and assess the impacts of different background types and leaf area index on the VIs’ performance. At the leaf level, the MNDVI8 index showed a strong linearity to changing chlorophyll and negligible difference to leaf structure/type. At canopy level, the best performing VIs were relatively consistent where LAI ≥ 4, but responded strongly to differences in background at low canopy coverage (LAI = 2). This research provides comprehensive assessments for the use of spectral indices in retrieval of spatially-continuous leaf chlorophyll content at the leaf (MTCI: R2 = 0.72; p < 0.001) and canopy (DD: R2 = 0.78; p < 0.001) level for resource management over different spatial and temporal scales. 相似文献
5.
6.
《Aquatic Botany》2005,81(4):326-342
The effects of NH4+ or NO3− on growth, resource allocation and nitrogen (N) uptake kinetics of two common helophytes Phragmites australis (Cav.) Trin. ex Steudel and Glyceria maxima (Hartm.) Holmb. were studied in semi steady-state hydroponic cultures. At a steady-state nitrogen availability of 34 μM the growth rate of Phragmites was not affected by the N form (mean RGR = 35.4 mg g−1 d−1), whereas the growth rate of Glyceria was 16% higher in NH4+-N cultures than in NO3−-N cultures (mean = 66.7 and 57.4 mg g−1 d−1 of NH4+ and NO3− treated plants, respectively). Phragmites and Glyceria had higher S/R ratio in NH4+ cultures than in NO3− cultures, 123.5 and 129.7%, respectively.Species differed in the nitrogen utilisation. In Glyceria, the relative tissue N content was higher than in Phragmites and was increased in NH4+ treated plants by 16%. The tissue NH4+ concentration (mean = 1.6 μmol g fresh wt−1) was not affected by N treatment, whereas NO3− contents were higher in NO3− (mean = 1.5 μmol g fresh wt−1) than in NH4+ (mean = 0.4 μmol g fresh wt−1) treated plants. In Phragmites, NH4+ (mean = 1.6 μmol g fresh wt−1) and NO3− (mean = 0.2 μmol g fresh wt−1) contents were not affected by the N regime. Species did not differ in NH4+ (mean = 56.5 μmol g−1 root dry wt h−1) and NO3− (mean = 34.5 μmol g−1 root dry wt h−1) maximum uptake rates (Vmax), and Vmax for NH4+ uptake was not affected by N treatment. The uptake rate of NO3− was low in NH4+ treated plants, and an induction phase for NO3− was observed in NH4+ treated Phragmites but not in Glyceria. Phragmites had low Km (mean = 4.5 μM) and high affinity (10.3 l g−1 root dry wt h−1) for both ions compared to Glyceria (Km = 6.3 μM, affinity = 8.0 l g−1 root dry wt h−1). The results showed different plasticity of Phragmites and Glyceria toward N source. The positive response to NH4+-N source may participates in the observed success of Glyceria at NH4+ rich sites, although other factors have to be considered. Higher plasticity of Phragmites toward low nutrient availability may favour this species at oligotrophic sites. 相似文献
7.
《Saudi Journal of Biological Sciences》2017,24(2):410-420
A study was conducted to understand the potential of Landsat-8 in the estimation of gross primary production (GPP) and to quantify the productivity of maize crop cultivated under hyper-arid conditions of Saudi Arabia. The GPP of maize crop was estimated by using the Vegetation Photosynthesis Model (VPM) utilizing remote sensing data from Landsat-8 reflectance (GPPVPM) as well as the meteorological data provided by Eddy Covariance (EC) system (GPPEC), for the period from August to November 2015. Results revealed that the cumulative GPPEC for the entire growth period of maize crop was 1871 g C m−2. However, the cumulative GPP determined as a function of the enhanced vegetation index – EVI (GPPEVI) was 1979 g C m−2, and that determined as a function of the normalized difference vegetation index – NDVI (GPPNDVI) was 1754 g C m−2. These results indicated that the GPPEVI was significantly higher than the GPPEC (R2 = 0.96, P = 0.0241 and RMSE = 12.6%). While, the GPPNDVI was significantly lower than the GPPEC (R2 = 0.93, P = 0.0384 and RMSE = 19.7%). However, the recorded relative error between the GPPEC and both the GPPEVI and the GPPNDVI was −6.22% and 5.76%, respectively. These results demonstrated the potential of the landsat-8 driven VPM model for the estimation of GPP, which is relevant to the productivity and carbon fluxes. 相似文献
8.
《Bioorganic & medicinal chemistry》2016,24(19):4723-4730
In this paper, 13 4-N-nitrophenyl substituted amino-4H-1,2,4-triazole derivatives were synthesized and their aromatase inhibitory activities were measured. The results show that the substitution of the groups on benzyl group can further improve their bioactivity and the compound with Cl on the para position of benzyl has the highest bioactivity (IC50 = 9.02 nM). A QSAR model was constructed from the 13 compounds with genetic function approximation using DS 2.1 package. This model can explain 90.09% of the variance (R2Adj), while it can predict 84.95% of the variance (R2cv) with the confidence interval of 95%. 相似文献
9.
There is a world-wide trend for deteriorating water quality and light levels in the coastal zone, and this has been linked to declines in seagrass abundance. Localized management of seagrass meadow health requires that water quality guidelines for meeting seagrass growth requirements are available. Tropical seagrass meadows are diverse and can be highly dynamic and we have used this dynamism to identify light thresholds in multi-specific meadows dominated by Halodule uninervis in the northern Great Barrier Reef, Australia. Seagrass cover was measured at ∼3 month intervals from 2008 to 2011 at three sites: Magnetic Island (MI) Dunk Island (DI) and Green Island (GI). Photosynthetically active radiation was continuously measured within the seagrass canopy, and three light metrics were derived. Complete seagrass loss occurred at MI and DI and at these sites changes in seagrass cover were correlated with the three light metrics. Mean daily irradiance (Id) above 5 and 8.4 mol m−2 d−1 was associated with gains in seagrass at MI and DI, however a significant correlation (R = 0.649, p < 0.05) only occurred at MI. The second metric, percent of days below 3 mol m−2 d−1, correlated the most strongly (MI, R = −0.714, p < 0.01 and DI, R = −0.859, p = <0.001) with change in seagrass cover with 16–18% of days below 3 mol m−2 d−1 being associated with more than 50% seagrass loss. The third metric, the number of hours of light saturated irradiance (Hsat) was calculated using literature-derived data on saturating irradiance (Ek). Hsat correlated well (R = 0.686, p < 0.01; and DI, R = 0.704, p < 0.05) with change in seagrass abundance, and was very consistent between the two sites as 4 Hsat was associated with increases in seagrass abundance at both sites, and less than 4 Hsat with more than 50% loss. At the third site (GI), small seasonal losses of seagrass quickly recovered during the growth season and the light metrics did not correlate (p > 0.05) with change in percent cover, except for Id which was always high, but correlated with change in seagrass cover. Although distinct light thresholds were observed, the departure from threshold values was also important. For example, light levels that are well below the thresholds resulted in more severe loss of seagrass than those just below the threshold. Environmental managers aiming to achieve optimal seagrass growth conditions can use these threshold light metrics as guidelines; however, other environmental conditions, including seasonally varying temperature and nutrient availability, will influence seagrass responses above and below these thresholds. 相似文献
10.
Anthropogenic modifications of sediment load can cause ecological degradation in stream and river ecosystems. However, in practice, identifying when and where sediment is the primary cause of ecological degradation is a challenging task. Biological communities undergo natural cycles and variation over time, and respond to a range of physical, chemical and biological pressures. Furthermore, fine sediments are commonly associated with numerous other pressures that are likely to influence aquatic biota. The use of conventional, non-biological monitoring to attribute cause and effect would necessitate measurement of multiple parameters, at sufficient temporal resolution, and for a significant period of time. Biomonitoring tools, which use low-frequency measurements of biota to gauge and track changes in the environment, can provide a valuable alternative means to detecting the effects of a given pressure. In this study, we develop and test an improved macroinvertebrate, family-level and mixed-level biomonitoring tool for fine sediment. Biologically-based classifications of sediment sensitivity were supplemented by using empirical data of macroinvertebrate abundance and percentage fine sediment, collected across a wide range of temperate river and stream ecosystems (model training dataset n = 2252) to assign detailed individual sensitivity weights to taxa. An optimum set of weights were identified by non-linear optimisation, as those that resulted in the highest Spearman’s rank correlation coefficient between the index (called the Empirically-weighted Proportion of Sediment-sensitive Invertebrates index; E-PSI) scores and deposited fine sediment in the model training dataset. The family and mixed-level tools performed similarly, with correlations with percentage fine sediment in the test dataset (n = 84) of rs = −0.72 and rs = −0.70 p < 0.01. Testing of the best performing family level version, over agriculturally impacted sites (n = 754) showed similar correlations to fine sediment (rs = −0.68 p < 0.01). The tools developed in this study have retained their biological basis, are easily integrated into contemporary monitoring agency protocols and can be applied retrospectively to historic datasets. Given the challenges of non-biological conventional monitoring of fine sediments and determining the biological relevance of the resulting data, a sediment-specific biomonitoring approach is highly desirable and will be a useful addition to the suite of pressure-specific biomonitoring tools currently used to infer the causes of ecological degradation. 相似文献
11.
Altaf Hussain Muhammad Hamid Rashid Raheela Perveen Muhammad Ashraf 《Plant Physiology and Biochemistry》2009,47(3):188-194
We report for the first time kinetic and thermodynamic properties of soluble acid invertase (SAI) of sugarcane (Saccharum officinarum L.) salt sensitive local cultivar CP 77-400 (CP-77). The SAI was purified to apparent homogeneity on FPLC system. The crude enzyme was about 13 fold purified and recovery of SAI was 35%. The invertase was monomeric in nature and its native molecular mass on gel filtration and subunit mass on SDS-PAGE was 28 kDa. SAI was highly acidic having an optimum pH lower than 2. The acidic limb was missing. Proton transfer (donation and receiving) during catalysis was controlled by the basic limb having a pKa of 2.4. Carboxyl groups were involved in proton transfer during catalysis. The kinetic constants for sucrose hydrolysis by SAI were determined to be: km = 55 mg ml?1, kcat = 21 s?1, kcat/km = 0.38, while the thermodynamic parameters were: ΔH* = 52.6 kJ mol?1, ΔG* = 71.2 kJ mol?1, ΔS* = ?57 J mol?1 K?1, ΔG*E–S = 10.8 kJ mol?1 and ΔG*E–T = 2.6 kJ mol?1. The kinetics and thermodynamics of irreversible thermal denaturation at various temperatures 53–63 °C were also determined. The half -life of SAI at 53 and 63 °C was 112 and 10 min, respectively. At 55 °C, surprisingly the half -life increased to twice that at 53 °C. ΔG*, ΔH* and ΔS* of irreversible thermal stability of SAI at 55 °C were 107.7 kJ mol?1, 276.04 kJ mol?1 and 513 J mol?1K?1, respectively. 相似文献
12.
Two tetracyanometalate building blocks, [Fe(5,5′-dmbipy)(CN)4]? (2) and [Fe(4,4′-dmbipy)(CN)4]? (3) (5,5′-dmbipy = 5,5′-dimethyl-2,2′-bipyridine; 4,4′-dmbipy = 4,4′-dimethyl-2,2′-bipyridine), and two cyano-bridged heterobimetallic complexes, [Cu2(bpca)2(H2O)2Fe2(5,5′-dmbipy)2(CN)8] · 2[Cu(bpca)Fe(5,5′-dmbipy)(CN)4] · 4H2O (4) and [Cu(bpca)Fe(4,4′-dmbipy)(CN)4]n (5) (bpca = bis(2-pyridylcarbonyl)amidate), have been synthesized and structurally characterized. Complex 4 contains two dinuclear and one tetranuclear heterobimetallic clusters in an asymmetric unit whereas the structure of complex 5 features a one-dimensional heterobimetallic zigzag chain. The Cu(II) ion is penta-coordinated in the form of a distorted square-based pyramid. Magnetic studies show ferromagnetic coupling between Cu(II) and Fe(III) ions with g = 2.28, J1 = 2.64 cm?1, J2 = 5.40 cm?1 and TIP = ?2.36 × 10?3 for complex 4, and g = 2.17, J = 4.82 cm?1 and zJ′ = 0.029 cm?1 for complex 5. 相似文献
13.
《Inorganica chimica acta》2006,359(11):3549-3556
A series of cationic trispyrazolylmethane complexes of the general form [TmRM(CH3CN)3]2+ (Tm = tris(pyrazolyl)methane, 1, R = 3,5-Me2, M = Fe(II); 2, R = 3-Ph, M = Fe(II); 3, R = 3,5-Me2, M = Co(II); 4, R = 3-Ph, M = Co(II)) with ‘piano-stool’ structures was prepared by the reaction of the N3tripodal ligands (TmR)with [(CH3CN)6M](BF4)2 in a 1:1 stoichiometric ratio. Magnetic susceptibility measurements indicate that all four complexes with BF4− counter anions are paramagnetic, high-spin systems in the solid state with μeff at high temperatures of 5.2 (1, S = 2), 5.4 (2, S = 2), 4.9 (3, S = 3/2) and 4.6 (4, S = 3/2) BM, respectively. Comparisons of bond lengths from the metal centre to the TmR nitrogen donors, and from the metal centre to the acetonitrile nitrogen donors indicate that the neutral tripodal ligands appear to be more weakly coordinated to the metal centre than are the acetonitrile ligands. Reactions of these tripodal complexes with bidentate phosphine ligands, such as 1,2-diphosphinoethane or 1,2-bis(diallylphosphino)ethane leads to displacement of the tripodal ligand, or to the formation of more thermally stable bis-ligand complexes M(TmR)2 (R = 3,5-dimethyl). 相似文献
14.
Patrick L. Feng Christopher C. Beedle Changhyun Koo Jon Lawrence Stephen Hill David N. Hendrickson 《Inorganica chimica acta》2008,361(12-13):3465-3480
We review an extensive body of single-crystal high-frequency electron paramagnetic resonance (HFEPR) data in order to determine the transverse spin Hamiltonian parameters that control the tunneling of the direction of magnetization in a variety of integer and half-integer-spin single-molecule magnets (SMMs). The SMMs studied are members of the following families: S = 9/2 [Mn4O3Cl]6+; S = 5 [Mn3NiO4]6+; S = 6 [Mn3ZnO4]6+; and S = 4 [Ni4(OR)4]4+. HFEPR spectra for the half-integer S = 9/2 Mn4 complexes that have C3 symmetry do not provide measurable evidence for transverse spin Hamiltonian terms. This finding is consistent with the relatively large coercive field seen in the magnetization hysteresis loops for these complexes. On the other hand, a low symmetry S = 9/2 complex exhibits a much faster rate of ground-state magnetization tunneling, in agreement with HFEPR spectra for a powder sample that gives a rhombic zero-field splitting (ZFS) parameter of E = 0.140 cm?1. The S = 5 Mn3Ni systems exhibit magnetization tunneling that is much faster than seen for the high-symmetry S = 9/2 Mn4 complexes. This can be attributed to their integer-spin ground states. Like the C3 symmetry Mn4 SMMs, the HFEPR spectra for high-symmetry Mn3Ni complexes do not provide measurable evidence for transverse ZFS terms. However, the spectra exhibit broad peaks, suggesting distributions in the local molecular environments brought about by disordered solvate molecules. This disorder likely explains the fast tunneling in the high-symmetry S = 5 Mn3Ni systems, though one cannot rule out fourth- (and higher-) order interactions that cannot be detected by HFEPR due to the broad resonances. The one S = 6 Mn3Zn complex shows an even faster rate of tunneling compared to the isostructural S = 5 Mn3Ni complex. Finally, the S = 4 [Ni(hmp)(dmb)Cl]4 complex provides unique insights into the origin of fourth- (and higher-) order interactions found for many SMMs on the basis of analysis using a giant spin Hamiltonian (GSH) approximation. We conclude that the fourth-order anisotropy found for the S = 4 ground state of [Ni(hmp)(dmb)Cl]4 originates from the second-order ZFS interactions associated with the individual NiII ions, but only as a result of higher-order processes that occur via S-mixing between the ground state and higher-lying (S < 4) spin-multiplets. The S-mixing is relatively strong in this system because of comparable exchange and anisotropy energy scales. The relatively fast tunneling is a direct consequence of this S-mixing, as opposed to any intrinsic fourth-order (spin–orbit) anisotropy associated with NiII. 相似文献
15.
Wetland vegetation is a core component of wetland ecosystems. Wetland vegetation structural parameters, such as height and leaf area index (LAI) are important variables required by earth-system and ecosystem models. Therefore, rapid, accurate, objective and quantitative estimations of wetland vegetation structural parameters are essential. The airborne laser scanning (also called LiDAR) is an active remote sensing technology and can provide accurate vertical vegetation structural parameters, but its accuracy is limited by short, dense vegetation canopies that are typical of wetland environments. The objective of this research is to explore the potential of estimating height and LAI for short wetland vegetation using airborne discrete-return LiDAR data.The accuracies of raw laser points and LiDAR-derived digital elevation models (DEM) data were assessed using field GPS measured ground elevations. The results demonstrated very high accuracy of 0.09 m in raw laser points and the root mean squared error (RMSE) of the LiDAR-derived DEM was 0.15 m.Vegetation canopy height was estimated from LiDAR data using a canopy height model (CHM) and regression analysis between field-measured vegetation heights and the standard deviation (σ) of detrended LiDAR heights. The results showed that the actual height of short wetland vegetation could not be accurately estimated using the raster CHM vegetation height. However, a strong relationship was observed between the σ and the field-measured height of short wetland vegetation and the highest correlation occurred (R2 = 0.85, RMSE = 0.14 m) when sample radius was 1.50 m. The accuracy assessment of the best-constructed vegetation height prediction model was conducted using 25 samples that were not used in the regression analysis and the results indicated that the model was reliable and accurate (R2 = 0.84, RMSE = 0.14 m).Wetland vegetation LAI was estimated using laser penetration index (LPI) and LiDAR-predicted vegetation height. The results showed that the vegetation height-based predictive model (R2 = 0.79) was more accurate than the LPI-based model (the highest R2 was 0.70). Moreover, the LAI predictive model based on vegetation height was validated using the leave-one-out cross-validation method and the results showed that the LAI predictive model had a good generalization capability. Overall, the results from this study indicate that LiDAR has a great potential to estimate plant height and LAI for short wetland vegetation. 相似文献
16.
《Inorganica chimica acta》2006,359(5):1421-1426
Synthesis, structural characterization, and spectroscopic and magnetic properties of three new cyano-bridged 3d–4f bimetallic complexes, LnIII(DMF)4(H2O)3CrIII (CN)6 · nH2O (Ln = Nd, Sm, Gd), have been described. The Nd–Cr complex crystallizes in the monoclinic P21/n space group with the following unit cell parameters: a = 20.063(7) Å, b = 8.967(4) Å, c = 18.023(6) Å, b = 96.12(3)°, V = 3224(2) Å3, and Z = 4. The neodymium (III) ion, which adopts anti-prism eight-coordination environment, is linked to the [CrIII(CN)6]3− moiety through a bridging cyanide ligand with Nd–N = 2.550(4) Å and Nd–N–C = 164.4(4)°. The variable-temperature (0.5 T at 2–300 K) and variable-field (0–5 T at 2 and 5 K) magnetic measurements reveal that the weak interaction of Gd–Cr complexes differs from that of Nd–Cr and Sm–Cr ones mainly because of the lack of orbital angular momentum. The XPS and diffuse reflectance electronic spectra were also measured to discuss charge transfer transitions concerning π-backdonation from the viewpoint of magneto-optical functions. 相似文献
17.
Marcelo C. Matsudo Raquel P. Bezerra Sunao Sato Patrizia Perego Attilio Converti João Carlos M. Carvalho 《Biochemical Engineering Journal》2009,43(1):52-57
Arthrospira (Spirulina) platensis (Nordstedt) Gomont was autotrophically cultivated for biomass production in repeated fed-batch process using urea as nitrogen source, with the aim of making large-scale production easier, increasing cell productivity and then reducing the production costs. It was investigated the influence of the ratio of renewed volume to total volume (R), the urea feeding time (tf) and the number of successive repeated fed-batch cycles on the maximum cell concentration (Xm), cell productivity (Px), nitrogen-to-cell conversion yield (Yx/n), maximum specific growth rate (μm) and protein content of dry biomass. The experimental results demonstrated that R = 0.80 and tf = 6 d were the best cultivation conditions, being able to simultaneously ensure, throughout the three fed-batch cycles, the highest average values of three of the five responses (Xm = 2101 ± 113 mg L?1, Px = 219 ± 13 mg L?1 d?1 and Yx/n = 10.3 ± 0.8 g g?1). 相似文献
18.
This paper reports development and implementation of superior fermentation strategies for β-galactosidase production by Lactobacillus acidophilus in a stirred-tank bioreactor. Process parameters (aeration and agitation) were optimized for the process by application of Central Composite Design. Aeration rate of 0.5 vvm and agitation speed of 250 rpm were most suitable for β-galactosidase production (2001.2 U/L). Further improvement of the operation in pH controlled environment resulted in 2135 U/L of β-galactosidase with productivity of 142.39 U/L h. Kinetic modeling for biomass and enzyme production and substrate utilization were carried out at the aforementioned pH controlled conditions. The logistic regression model (X0 = 0.01 g/L; Xmax = 2.948 g/L; μmax = 0.59/h; R2 = 0.97) was used for mathematical interpretation of biomass production. Mercier's model proved to be better than Luedeking–Piret model in describing β-galactosidase production (P0 = 0.7942 U/L; Pmax = 2169.3 U/L; Pr = 0.696/h; R2 = 0.99) whereas the latter was more efficient in mathematical illustration of lactose utilization (m = 0.187 g/g h; Yx/s = 0.301 g/L; R2 = 0.98) among the two used in this study. Strategies like fed-batch fermentation (3694.6 U/L) and semi-continuous fermentation (5551.9 U/L) further enhanced β-galactosidase production by 1.8 and 2.8 fold respectively. 相似文献
19.
《Enzyme and microbial technology》2005,36(2-3):307-313
Aerobic granulation is a process in which suspended biomass aggregate and form discrete well-defined granules in aerobic systems. To investigate the properties and kinetics of aerobic granular sludge, aerobic granules were cultivated with glucose synthetic wastewater in a series of sequencing batch reactors (SBR). The spherical shaped granules were observed on 8th day with the mean diameter of 0.1 mm. With the organic loading rate (OLR) being increased to 4.0 g COD L−1 d−1, aerobic granules grew matured with spherical shape. The size of granules ranged from 1.2 to 1.8 mm, and the corresponding settling velocity of individual granule was 24.2–36.4 m h−1. The oxygen utilization rate (OUR) of mature granules was 41.90 g O2 kg MLSS−1 h−1, which was two times higher than that of activated sludge (18.32 g O2 kg MLSS−1 h−1). The experimental data indicated that the substrate utilization and biomass growth kinetics generally followed Monod's kinetics model. The corresponding kinetic coefficients of k (maximum specific substrate utilization rate), Ks (half velocity coefficient), Y (growth yield coefficient) and Kd (decay coefficient) were determined as follows, kc = 23.65 d−1, Kc = 3367.05 mg L−1, KN = 0.038 d−1, KN = 29.65 mg L−1, Y = 0.1927–0.2022 mg MMLS (mg COD)−1 and Kd = 0.00845–0.0135 d−1, respectively. Those properties of aerobic granules made aerobic granules system had a short setup period, high substrate utilization rate and low sludge production. 相似文献
20.
Marcus W. Beck Lorin K. Hatch Bruce Vondracek Ray D. Valley 《Ecological Indicators》2010,10(5):968-979
Traditional approaches for managing aquatic resources have often failed to account for effects of anthropogenic disturbances on biota that are not directly reflected by chemical and physical proxies of environmental condition. The index of biotic integrity (IBI) is a potentially effective assessment method to integrate ecological, functional, and structural aspects of aquatic systems. A macrophyte-based IBI was developed for Minnesota lakes to assess the ability of aquatic plant communities to indicate environmental condition. The index was developed using quantitative point intercept vegetation surveys for 97 lakes that represent a range of limnological and watershed characteristics. We followed an approach similar to that used in Wisconsin to develop the aquatic macrophyte community index (AMCI). Regional adaptation of the AMCI required the identification of species representative of macrophyte communities in Minnesota. Metrics and scaling methods were also substantially modified to produce a more empirically robust index. Regression analyses indicated that IBI scores reflected statewide differences in lake trophic state (R2 = 0.57, F = 130.3, df = 1, 95, p < 0.005), agricultural (R2 = 0.51, F = 83.0, df = 1, 79, p < 0.005), urban (R2 = 0.22, F = 23.0, df = 1, 79, p < 0.005), and forested land uses (R2 = 0.51, F = 84.7, df = 1, 79, p < 0.005), and county population density (R2 = 0.14, F = 16.6, df = 1, 95, p < 0.005). Variance partitioning analyses using multiple regression models indicated a unique response of the IBI to human-induced stress separate from a response to natural lake characteristics. The IBI was minimally affected by differences in sample point density as indicated by Monte Carlo analyses of reduced sampling effort. Our analysis indicates that a macrophyte IBI calibrated for Minnesota lakes could be useful for identifying differences in environmental condition attributed to human-induced stress gradients. 相似文献