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1.
The main purpose of this article is to demonstrate that principal component analysis (PCA) and partial least squares regression (PLSR) can be used to extract information from particle size distribution data and predict rheological properties. Samples from commercially relevant Aspergillus oryzae fermentations conducted in 550 L pilot scale tanks were characterized with respect to particle size distribution, biomass concentration, and rheological properties. The rheological properties were described using the Herschel-Bulkley model. Estimation of all three parameters in the Herschel-Bulkley model (yield stress (tau(y)), consistency index (K), and flow behavior index (n)) resulted in a large standard deviation of the parameter estimates. The flow behavior index was not found to be correlated with any of the other measured variables and previous studies have suggested a constant value of the flow behavior index in filamentous fermentations. It was therefore chosen to fix this parameter to the average value thereby decreasing the standard deviation of the estimates of the remaining rheological parameters significantly. Using a PLSR model, a reasonable prediction of apparent viscosity (micro(app)), yield stress (tau(y)), and consistency index (K), could be made from the size distributions, biomass concentration, and process information. This provides a predictive method with a high predictive power for the rheology of fermentation broth, and with the advantages over previous models that tau(y) and K can be predicted as well as micro(app). Validation on an independent test set yielded a root mean square error of 1.21 Pa for tau(y), 0.209 Pa s(n) for K, and 0.0288 Pa s for micro(app), corresponding to R(2) = 0.95, R(2) = 0.94, and R(2) = 0.95 respectively. 相似文献
2.
During a batch cultivation on D-glucoseAgrobacterium radiobacter produces an extracellular polysaccharide agrobacteran. The rheological character of the culture broth is non-Newtonian and
can be described by a power-law model or by the Hershel-Bulkley equation. Correlations were obtained between the parameters
of these equations and the concentration of agrobacteran in the medium. For the given mixing system the rheological properties
of the medium can be used to approximately estimate the qualitative changes in the intensity of mixing and to employ these
data for regulating mixing during cultivation. 相似文献
3.
用旋转黏度计测定了自絮凝颗粒酵母悬浮液的流变特性,并考察了其流变特性的影响因素,如菌体生物量、葡萄糖质量浓度、温度等。结果表明:自絮凝颗粒酵母悬浮液呈假塑性非牛顿流体,其流变特性服从幂律指数模型,随着菌体浓度的增大,稠度系数增大,流动行为指数减小;絮凝悬浮液的表观黏度随着糖浓度的增加有所增加,同一生物量下稠度系数k随着糖浓度的增加而增加,流动行为指数n随着糖浓度的增加变化很小,悬浮液的表观黏度随着温度的升高而降低;相同生物量下的流变指数随温度的升高而升高,而稠度系数随温度升高有所下降。 相似文献
4.
The objective of this study was to determine whether rheological properties of the vaginal fluid at the time of insemination could be used as an indicator of potential fertility in dairy cows. Thixotropy and flow behavior were evaluated. Vaginal samples were collected from 347 cows at the time of insemination, within a 12- to 24-h interval after the onset of a natural estrus. Logistic regression analysis showed no significant effects of thixotropy measurements on the pregnancy rate, while flow behavior and the index of consistency (K) had a significant effect. The decrease in the consistency index (K) was related to the increase in the pregnancy rate (odds ratio = 0.99; P = 0.014), and the risk of nonpregnancy was higher (odds ratio = 0.46; P = 0.024) in cows in which vaginal fluid had a Newtonian behavior. Non-Newtonian behavior was recorded in 294 samples (85%) while 53 behaved as Newtonian fluids. For samples from all cows, the mean value of the consistency index was 310 +/- 28.2 milliPascals.second(n) (x +/- SEM) and ranged from 0 to 3881 milliPascals.second(n). In Newtonian samples, the consistency index mean was 2.6 +/- 0.6 milliPascals.second(n) and 367.6 +/- 30.4 milliPascals.second(n) for non-Newtonian samples. Of the 347 cows, 131 (38%) became pregnant. For flow behavior classification, 15 (28.3%) cows in which samples had Newtonian behavior and 116 (39.5%) cows with non-Newtonian samples became pregnant. Therefore, the highest probability of pregnancy was shown by cows in which samples had non-Newtonian behavior and the lowest consistency index values. Our data suggest that flow behavior measurements of the vaginal fluid at the time of insemination may be an indicator of potential fertility in cattle. 相似文献
5.
The effect of increasing water composition on the rheological and microstructural behavior of a ternary cellulose acetate (CA)/N,N-dimethylacetamide (DMA)/water system is examined. Addition of water to the CA/DMA system results in enhanced steady shear viscosity and dynamic viscoelastic properties and ultimately to phase-separated gel formation. The changes in dynamic rheological behavior of the system during gelation correlate well with the combined solubility parameter (delta) and, in particular, the Hansen hydrogen-bonding solubility parameter index (delta(h)) of the solvent system, suggesting hydrogen-bonding interactions may be the major route initiating the sol-gel process. For all gels studied, the elastic modulus and the critical stress to yield shifts to higher values with increasing CA concentration and/or water content. In addition, the elastic modulus exhibits a power-law behavior with water content, with the same power-law exponent observed for gels containing different CA concentrations. Addition of water leads to formation of a denser gel network, as evidenced from direct visualization of the gel microstructure through confocal microscopy. 相似文献
6.
The rheological properties of an exopolysaccharide, EPS-R, produced by the marine bacteriumHahella chejuensis strain 96CJ10356 were investigated. The E24 of 0.5% EPS-R was 89.2%, which was higher than that observed in commercial polysaccharides such as xanthan gum (67.8%), gellan
gum (2.01%) or sodium alginate (1.02%). Glucose and galactose are the main sugars in EPS-R, with a molar ratio of ∼1∶6.8,
xylose and ribose are minor sugar components. The average molecular mass, as determined by gel filtration chromatography,
was 2.2×103 KDa. The intrinsic viscosities of EPS-R were calculated to be 16.5 and 15.9 dL/g using the Huggins and Kraemer equations,
respectively, with a 2.3 dL/g overlap. In terms of rigidity, the conformation of EPS-R was similar to that of caboxymethyl
cellulose (5.0×10−2). The rheological behavior of EPS-R dispersion indicated that the formation of a structure intermediate between that of a
random-coil polysaccharide and a weak gel. The aqueous dispersion of EPS-R at concentrations ranging from 0.25 to 1.0% (w/w)
showed a marked shear-thinning property in accordance with Power-law behavior. In aqueous dispersions of 1.0% EPS-R, the consistency
index (K) and flow behavior index (n) were 1,410 and 0.73, respectively. EPS-R was stable to pH and salts. 相似文献
7.
In an attempt to resolve the difficult problem of on-line determination of the viscosity of non-Newtonian fermentation media, the authors have used a vibrating rod sensor mounted on a bioreactor. The sensor signal decreases nonlinearly with increased apparent viscosity. Electronic filtering of the signal damps the interfering effect of aeration and mechanical agitation. Sensor drift is very low (0.03% of measured value per hour).On the rheological level the sensor is primarily an empirical tool that must be specifically calibarated for each fermentation process. Once this is accomplished, it becomes possible to establish linear or second-degree correlations between the electrical signal from the sensor and the essential parameters of the ferementation process in question (pH of a feremented milk during acidification, concentration of extra cellular polysaccharide). In addition, by applying the power law to describe the rheological behavior of fermentation media, we observe a second-order polynomial correlation between the sensor signal and the behavior index (n). 相似文献
8.
Influence of microbial concentration on the rheology of non-Newtonian fermentation broths 总被引:2,自引:0,他引:2
The objective of this study was to quantify the effect of fungal biomass concentration on the rheology of non-Newtonian fermentation
systems. Batch fermentations of Penicillium chrysogenum were carried out with glucose as the sole carbon source. The flow behavior of the system was characterized at various fermentation
times and was adequately described by the power-law model. The apparent viscosity of the fermentation broth was significantly
affected by biomass concentrations in the fermenter. Fermentation broths containing 17.71 g/l biomass as dry weight were characterized
by an apparent viscosity of 0.25 Pa s at a shear rate of 50 s−1. Microbial concentration also affected the power-law flow-behavior index and the consistency index. The value of the consistency
index ranged from 0.002 Pa s
n
at a biomass concentration of 0.1 g/l to 6.14 Pa s
n
at a biomass concentration of 17.71 g/l. The flow-behavior index decreased from an initial value of 1 to a final value of
0.17. Simple empirical correlations have been proposed to quantify the dependence of the power-law parameters on fungal biomass
concentration. Experimental data obtained in this study were accurately described by these correlations. The general applicability
of these relationships was tested, using previously published rheological data on Aspergillus awamori and Aspergillus niger fermentation broths, and good agreement was seen between experimental data and the predictions from the empirical correlations.
Received: 24 March 1998 / Received revision: 10 September 1998 / Accepted: 16 October 1998 相似文献
9.
《Journal of Fermentation Technology》1987,65(3):319-323
By culture of Saccharomyces cerevisiae with cell recycle using tangential microfiltration, high cell concentrations are obtained (in the range of 0 to 345 gl−1 dry-weight). The rheological properties of the cell suspension during the cell growth were studied. Over a wide range of biomass concentration (X<275 gl−1D.W.) the power-law model was found adequate to describe the rheological behaviour of the broth. Pronounced non-Newtonian (pseudoplastic) behaviour occurred for X > 75 gl−1. Experimental correlations for apparent viscosity (na, mPa.s) and power-law index vs. biomass concentration (X, gl−1) were established: na = (1+0.012X)2 suitable over the whole range of concentration up to 275 gl−1 D.W. na = 1+0.04X in the low concentration range; X<100 gl−1D.W. Beyond the cell concentration of 275 gl−1 D.W. the viscosity increases suddenly. 相似文献
10.
The present study was conducted to determine whether there is any correlation between sperm motion and rheological behavior of the anterior vaginal fluid of superovulated dairy heifers. Vaginal fluid samples were collected from 16 superovulated dairy heifers from 12 to 20 h after estrus detection. Flow behavior was evaluated. The mean consistency index was 56.6 +/- 23.9 miliPascals per second(n) (mPa.s(n)) and ranged from 2.2 to 278 mPa.s(n). Of 16 samples of anterior vaginal fluid, 11 (69%) behaved as Newtonian fluids, while 5 (31%) behaved as non-Newtonian fluids. Concentrations and motility parameters of bull spermatozoa were evaluated into vaginal fluid samples after 30 min of incubation. The sperm concentrations were lower (P=0.01) in non-Newtonian than in Newtonian samples and were negatively correlated (P=0.009; r = - 0.62) with the index of consistency. The motility parameters such as average path velocity (VAP), curvilinear velocity (VCL) and linear velocity (VSL) were significantly higher in non-Newtonian than in Newtonian samples and were positively correlated with the index of consistency. Our data show that as mechanical resistance of vaginal fluid to sperm increases, the motility parameters increase while the migration efficiency appears to decrease. 相似文献
11.
12.
A non-axenic strain of the microalga Botryococcus braunii Kützing, isolated from a small lake in Portugal, when cultured at 25°C in mineral medium and under continuous illumination, showed a poor production of hydrocarbons (5% of the dry biomass) but excreted remarkably high quantities of an exopolysaccharide (4–4·5 g litre−1) into the medium. The production of the soluble polysaccharide, which contains galactose, fucose and uronic acid residues, occurs mainly after the exponential phase of growth.The rheological properties of broth during growth were studied. The increase of polysaccharide concentration as a consequence of its continuous biosynthesis, changes the medium behaviour from Newtonian to non-Newtonian with a flow characterized by a power-law equation. This behaviour becomes Newtonian again, when the culture is maintained for a longer period of time. 相似文献
13.
The effect of shear stress on the production of a high viscosity polysaccharide, methylan, from methanol by Methylobacterium organophilum was investigated by using a multidisk mixer. It was observed in the multidisk mixer with defined shear stresses that the specific production rate of methylan increased gradually with increasing shear stress up to 30 Pa, and the production rate was constant beyond 30 Pa. This result suggested that the limited mass transfer from the medium into cells reduced methylan production. A novel bioreactor that provided the large volume of a high shear region was used to increase methylan production. Fed-batch cultures in the novel bioreactor were performed by the dissolved oxygen-stat method of methanol. When 1.13 g/L ammonium ion was added, the concentrations of cells of methylan were 31 and 20.6 g/L, respectively. The productions of cells and methylan in our designed bioreactor were 20 and 50% higher than those obtained in a conventional fermentor. The methylan content reached a maximum of 20.7 g/L in the bioreactor and the viscosity of the fermentation broth was 127 Pa . s, which corresponds to 68 g/L as a xanthan. (c) 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 54: 115-121, 1997. 相似文献
14.
Effect of biomass concentration and mycelial morphology on fermentation broth rheology 总被引:8,自引:0,他引:8
The effect of biomass concentration and mycelial morphology on fungal fermentation broth rheological properties has been investigated. In previous work it had been shown that commonly used rheological parameters, such as the power law consistency and flow behavior indices, could be correlated successfully with the broth biomass concentration and clump morphological parameters of roughness and compactness. More recent work on a broader range of data showed a correlation between roughness and compactness; consequently, it was not correct to use both of these morphological variables simultaneously in rheological parameter correlations. Furthermore, earlier correlations were only made using clump morphological parameters, as clumps were found to be around 90% of the biomass in batch fermentations. In the present work it was found that the percentage of clumps fell to around 30% to 40% of a sample during the later stages of fed-batch fermentations. No clear relationship between the flow behavior index and biomass concentration was found, at least for those phases of the fermentation in which the viscosities were high enough for the rheology to be characterized by a disk turbine rheometer. The mean value of the flow behavior index was found to be 0.35 +/- 0.1 (standard deviation) throughout both batch and fed-batch fermentations, although some significant deviations from this value were observed early and very late in the fermentations. Correlations for the consistency index, measured using a disk turbine rheometer, were based on the biomass concentration and the mycelial size (represented by the mean projected area or the mean maximum dimension of all the mycelia). These correlations were reasonably successful for both fed-batch and batch fermentations. The correlation using the mean maximum dimension was preferred to that using the mean projected area, as the former is independent of magnification. The proposed correlation is: where K is the consistency index (Pa. s(n>)), C(m) is the biomass concentration as dry cell weight (g L(-1)), and D is the mean maximum dimension (microm). It should be noted that small changes in the exponent on the biomass concentration (alpha) may dramatically affect any predictions. Consequently, caution in the use of this correlation (and that based on mean projected area) is advocated, although its accuracy may be suitable for operational or design purposes. 相似文献
15.
Maria Cristina Ricci Queiroz Maria Candida R. Facciotti Willibaldo Schmidell 《Biotechnology letters》1997,19(2):167-170
Two kinds of mathematical correlations are proposed, one between the biomass concentration and the rheological parameter consistency index (K) from the 'Power law' and another between either the specific growth rate or the specific glucoamylase production rate and K. Experimental data from Aspergillus awamori batch cultivations, with initial polysaccharide concentrations in the range of 20 to 180 g.L, were used to define these correlations. 相似文献
16.
The influence of carbon source and aeration rate on fermentation broth rheology, mycelial morphology and red pigment production of Paecilomyces sinclairii was investigated in a 5-l stirred-tank bioreactor. The characteristics of P. sinclairii grown on starch and on sucrose medium were comparatively studied: the specific growth rate in sucrose medium (0.04 h(-1)) was higher than that in starch medium, whereas the specific production rate of red pigments (0.04 gg(-1)d(-1)) was favorable in starch medium. P. sinclairii grown in sucrose medium were highly branched and showed longer hyphal lengths than that in starch medium. The consistency index (K) in sucrose medium was markedly higher than that in starch medium due to higher cell mass, while the higher values of flow behavior index (n) were indicated at the late stationary phase in starch medium. The aeration rate was varied within the ranges from 0.5 to 3.5 vvm while running the fermentation at mild agitation of 150 rpm using sucrose as the carbon source. The maximum biomass concentration of P. sinclairii was about 33 gl(-1) with an aeration rate of 1.5 vvm, whereas the maximum yield of red pigment production (4.73 gl(-1)) was achieved with 3.5 vvm. The highly branched cell morphology appeared at 1.5 vvm and the highly vacuolated cell morphology was observed in a high aeration rate (3.5 vvm). There was no significant variance in rheological parameters (K and n) between culture broths from different aeration conditions. 相似文献
17.
The objective of this study was to quantify the effect of disrupting two chitin synthases, chsB and csmA, on the morphology and rheology during batch cultivation of Aspergillus oryzae. The rheological properties were characterized in batch cultivations at different biomass concentrations (from 3.4-22.5 g kg(-1) biomass) and the power-law model adequately described the rheological properties. In the cultivations there were pellets, clumps, and freely dispersed hyphal elements. The different morphological fractions were quantified using image analysis. The apparent viscosity of the fermentation broth was significantly affected by the biomass concentration, the morphology, and also by pH. The chsB disruption strain had lower consistency index K values for all biomass concentrations investigated, which is a desirable trait for industrial Aspergillus fermentations. 相似文献
18.
19.
《Theriogenology》1996,46(1):57-63
The present study was conducted to evaluate rheological properties of the vaginal fluid in dairy cows. Thixotropy and flow behavior were evaluated. Vaginal fluid samples were collected in 8 cows at the beginning of a natural estrus and then every 8 h for 24 h. Vaginal samples were also collected from 208 cows at the time of insemination within 12 to 24 h interval after the onset of a natural estrus.Time-dependent variations were registered during the estrus. The limit shear stress for flow production (To), the shear stress of equilibrium (Te) and the consistency index (K) decreased at 8 and 16 h and markedly increased 24 h after the beginning of estrus. At the time of insemination, structural variation was registered and the fluids were considered to be thixotropic in samples of 181 cows (87%); in the remaining samples (27 cows), structural variation was not registered and the fluids were considered to be nonthixotropic. For flow behavior values, 178 samples (85.6%) presented non-Newtonian behavior, while 30 behaved as Newtonian fluids. The mean values of the TO and the Te were 6.1 ± 0.69 and 1.9 ± 0.69 pascals, respectively. Consistency index (K) mean was 364.9 ± 41.4 milipascals per secondn Our data show an increase of fluidity at the middle of the estrus period in the cow and a wide variation of rheological measurements of vaginal fluid at the time of insemination. 相似文献
20.
High prevalence of phagocytic-resistant capsular serotypes of Klebsiella pneumoniae in liver abscess
Lin JC Chang FY Fung CP Xu JZ Cheng HP Wang JJ Huang LY Siu LK 《Microbes and infection / Institut Pasteur》2004,6(13):1191-1198
To better understand the role of capsular polysaccharide (CPS) K1 or K2 in Klebsiella pneumoniae liver abscess as well as the development of metastasis to eye, neutrophil phagocytosis of 70 CPS isolates including K1 (n = 23)/K2 (n = 10), non-K1/K2 (n = 37) was evaluated by flow cytometry, fluorescence imaging, and electron microscopy. K1/K2 isolates were significantly more resistant to phagocytosis (P < 0.0001) than non-K1/K2 isolates and displayed increased resistance to intracellular killing. Although mucoid phenotype (M-type) K1/K2 isolates were significantly more resistant to phagocytosis (P = 0.0029) than M-type non-K1/K2, no significant difference in the phagocytosis rate was observed between K1/K2 isolates with M-type and non-M-type (P = 0.0924). Mucoidy is an associated factor that was predominant in K1/K2 isolates, but which itself is not an independent influence on phagocytic resistance. The K1/K2 CPS proved significantly more resistant to phagocytosis than non-K1/K2 CPS in liver abscess isolates (P < 0.0001) and non-abscess isolates (P = 0.0001), suggesting that K1/K2 isolates were generally more virulent in both liver abscess and in non-liver abscess conditions. These findings indicate that resistance of CPS K1 or K2 K. pneumoniae to phagocytosis and intracellular killing presumably contributes to their high prevalence in liver abscess and uniquely in endophthalmitis. 相似文献