| 1. |
- Navrátil, Marián, et al.
(författare)
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On-line multisensor monitoring of yogurt and Filmjolk fermentations on production scale
- 2004
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Ingår i: Journal of Agricultural and Food Chemistry. - : American Chemical Society (ACS). - 0021-8561 .- 1520-5118. ; 52:3, s. 415-420
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Tidskriftsartikel (refereegranskat)abstract
- Near-infrared (NIR) spectrometry and electronic nose (EN) data were used for on-line monitoring of yogurt and filmjölk (a Swedish yogurt-like sour milk) fermentations under industrial conditions. The NIR and EN signals were selected by evaluation of principal component analysis loading vectors and further analyzed by studying the variability of the selected principal components. First principal components for the NIR and the EN signals were used for on-line generation of a process trajectory plot visualizing the actual state of fermentation. The NIR signals were also used to set up empirical partial least-squares (PLS) models for prediction of the cultures' pH and titratable acidity (expressed as Thorner degrees, °T). By using five or six PLS factors the models yielded acceptable predictions that could be further improved by increasing the number of reliable and precise calibration data. The presented results demonstrate that the fusion of the NIR and EN signals has a potential for rapid on-line monitoring and assessment of process quality of yogurt fermentation.
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| 2. |
- Taherzadeh Esfahani, Mohammad, 1965, et al.
(författare)
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Continuous Cultivation of Dilute-Acid Hydrolysates to Ethanol by Immobilized Saccharomyces cerevisiae
- 2001
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Ingår i: Applied Biochemistry and Biotechnology. - 0273-2289 .- 1559-0291. ; 95:1, s. 45-57
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Tidskriftsartikel (refereegranskat)abstract
- The continuous cultivation of immobilized Saccharomyces cerevisiae CBS 8066 on dilute-acid hydrolysates of forest residuals was investigated. The yeast cells were immobilized in 2–4% Ca-alginate beads. The 2% beads were not stable. However, the 3 and 4% beads were stable for at least 3 wk when an extra resource of calcium ions was available in the medium. The continuous cultivation of a dilute-acid hydrolysate by the immobilized cells at dilution rates of 0.3, 0.5, and 0.6 h−1 resulted in 86, 83, and 79% sugar consumption, respectively, and an ethanol yield between 0.45 and 0.48 g/g. The hydrolysate was fermentable at a dilution rate of 0.1 h−1 in a free-cell system but washed out at a dilution rate of 0.2 h−1. The continuous cultivation of a more inhibiting hydrolysate was not successful by either free- or immobilized-cell systems even at a low dilution rate of 0.07 h−1. However, when the hydrolysate was overlimed, it was fermentable by the immobilized cells at a dilution rate of 0.2 h−1.
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| 3. |
- Jagers, Peter, 1941, et al.
(författare)
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Branching processes in near-critical random environments
- 2004
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Ingår i: Journal of Applied Probability. - : Cambridge University Press (CUP). - 0021-9002 .- 1475-6072. ; 41A, s. 17-23
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Tidskriftsartikel (refereegranskat)abstract
- Branching processes are studied in random environments that are influenced by the population size and approach criticality as the population gets large. Results are applied to the polymerase chain reaction (PCR), which is empirically known to exhibit first exponential and then linear growth of molecule numbers.
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| 4. |
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| 5. |
- Vendel, M., et al.
(författare)
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Initiation of incrustation by crystal collision
- 2000
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Ingår i: Chemical engineering research & design. - : Elsevier BV. - 0263-8762 .- 1744-3563. ; 78:A5, s. 749-755
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Tidskriftsartikel (refereegranskat)abstract
- Initiation of incrustation by collision between crystals and a solid surface is investigated. The suspension flow towards the vessel wall in a crystallizer is simulated by laboratory experiments. A liquid jet of supersaturated suspension impinges on a plate at well defined hydrodynamics, supersaturation and parent crystal size. Experiments have been carried out with succinic acid/water. The results indicate that crusts may be initiated at supersaturation well below the metastable limit. Crusts are initiated on both Teflon(TM) and steel. More crust nuclei are formed by collision initiation on sanded stainless steel than on polished stainless steel or Teflon(TM). The results support the hypothesis that collision initiation of crusts is of industrial importance, and suggest that attention should be devoted to the hydrodynamics of crystallizers.
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| 6. |
- Agarwal, Parminder, et al.
(författare)
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Effect of polymeric additives on calcium carbonate crystallization as monitored by nephelometry
- 2004
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Ingår i: Crystal Growth & Design. - : American Chemical Society (ACS). - 1528-7483 .- 1528-7505. ; 4:3, s. 479-483
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Tidskriftsartikel (refereegranskat)abstract
- The effect of polymaleimide polymers on calcium carbonate crystallization was studied using nephelometry. Induction time and percent growth inhibition were determined for polymeric additives from the nephelometric data. The polymaleimide synthesized by KOH-initiated polymerization exhibited the greatest growth inhibition and longest nucleation time among the polymers investigated. Raman spectroscopy was used to determine the calcium carbonate polymorph formed in the presence of these polymeric additives.
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| 7. |
- Agarwal, Parminder, et al.
(författare)
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In situ monitoring of calcium carbonate polymorphs during batch crystallization in the presence of polymeric additives using Raman spectroscopy
- 2003
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Ingår i: Crystal Growth & Design. - : American Chemical Society (ACS). - 1528-7483 .- 1528-7505. ; 3:6, s. 941-946
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Tidskriftsartikel (refereegranskat)abstract
- Polycarboxylic acids are well-known to affect calcium carbonate crystallization. Agarwal et al. (Ind. Eng. Chem. Res. 2003, in press) reported previously the synthesis of polymaleimide by a variety of techniques and initiators. In the present work, the effect of these polymers on calcium carbonate crystallization was studied by a variety of techniques. Crystallization experiments were carried out in a 1-L LABMAX automated batch reactor, and the concentration of calcium in solution was determined in real time. Raman spectroscopy was used to determine the relative amount of various calcium carbonate polymorphs as the crystallization occurred. However, Raman spectroscopy is a scattering technique, which may make it surface selective, and therefore results from solids may not be representative of bulk of sample. X-ray diffraction (XRD) was used to compare the results obtained by Raman spectroscopy. Peak intensity ratios were used for both Raman spectroscopy and XRD for calibration and measurement purposes. The results obtained by these two techniques for final percent vaterite for calcium carbonate crystallization in the presence of polymeric additives were in agreement within 2%. Therefore, use of Raman spectroscopy for in situ measurement of polymorph composition during calcium carbonate crystallization appears accurate. Scanning electron microscopy (SEM) data were useful in understanding the crystal morphology and to determine crystal size.
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| 8. |
- Agarwal, Parminder, et al.
(författare)
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Synthesis and characterization of polymaleimide
- 2003
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Ingår i: Industrial & Engineering Chemistry Research. - : American Chemical Society (ACS). - 0888-5885 .- 1520-5045. ; 42:13, s. 2881-2884
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Tidskriftsartikel (refereegranskat)abstract
- Simplified syntheses of polymaleimide employing anionic polymerization (from the melt and from solution) and metal compound-alcohol initiators such as PbO, SnO, tin bis(2-ethyl hexanoate) in the presence of tert-butyl benzyl alcohol are presented. The resulting polymers contain a combination of C-N- and C-C-connected monomers. Preliminary structures of the polymers were determined using NMR spectroscopy. The ratio of C-N- and C-C-connected monomers was determined, and the percentage of C-N-connected monomer units was found to vary from 40 to 80%, with the higher percentage resulting from anionic polymerization. The molecular weights of the polymers, as determined by gel permeation chromatography (GPC) with aqueous mobile phase and sodium polyacrylates standards, ranged between 1100 and 4200 for anionic polymerization and were about 11 500 for metal oxide-alcohol initiated polymerization. Solution-phase properties of the polymaleimides were evaluated by calcium chelation and precipitation inhibition studies. On the basis of the measured properties of these polymers, they are proposed as biodegradable, low-impact detergent additives to substitute currently used compounds.
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| 9. |
- Andraous, Johnny I., et al.
(författare)
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Effect of liquefaction enzymes on methanol concentration of distilled fruit spirits
- 2004
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Ingår i: American Journal of Enology and Viticulture. - 0002-9254 .- 1943-7749. ; 55:2, s. 199-201
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Tidskriftsartikel (refereegranskat)abstract
- Liquefaction enzymes are often used during fermentation of fruit mashes to improve the yield of ethanol and the ability to pump the mash. The liquefaction enzymes hydrolyze pectin, but in addition to the desired pectin hydrolysis activity, the enzymes also have pectinesterase activity which hydrolyzes the methyl ester in pectin resulting in methanol formation. Fermentations of various apple varieties and Bartlett pears were conducted using liquefaction enzymes. The resulting distilled products contained concentrations of methanol above the legal limit of 280 mg/100 mL of 40% ethanol, with the observed methanol concentrations in a range between 320 and 656 mg/100 mL of 40% ethanol. In contrast to the undesired increase in methanol concentration, the enzymes provide only a marginal increase in ethanol yield. The results indicate that liquefaction enzymes should be used with caution for pomace fruit and that methanol monitoring should be implemented if these enzymes are used for commercial products.
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| 10. |
- Falcon, Javier A., et al.
(författare)
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In situ monitoring of antisolvent addition crystallization with principal components analysis of Raman spectra
- 2004
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Ingår i: Crystal Growth & Design. - : American Chemical Society (ACS). - 1528-7483 .- 1528-7505. ; 4:3, s. 457-463
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Tidskriftsartikel (refereegranskat)abstract
- Fiber optic Raman spectroscopy was used for in situ monitoring of antisolvent addition crystallization of progesterone. Raman spectral features of the solute and the antisolvent were subjected to principal components analysis (PCA) to attempt to obtain information that is not readily apparent from the raw spectral data. For the system utilized, PCA was able to distinguish spectral features from the solute in solution, the solute crystals, and the antisolvent. Furthermore, PCA was capable of detecting subtle changes in the spectral data (as the addition of antisolvent progressed) that could be used as a warning for the onset of crystallization. The current study demonstrates the advantages that can be gained by combining PCA with Raman spectroscopy for monitoring crystallizations in situ.
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| 11. |
- Falcon, Javier A., et al.
(författare)
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Monitoring of antisolvent addition crystallization with Raman spectroscopy
- 2003
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Ingår i: Crystal Growth & Design. - : American Chemical Society (ACS). - 1528-7483 .- 1528-7505. ; 3:6, s. 947-952
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Tidskriftsartikel (refereegranskat)abstract
- Fiber optic Raman spectroscopy was used for in situ monitoring of antisolvent addition crystallization of cortisone acetate. Raman spectral features of the solvent, the antisolvent, and the solute were monitored to measure the relative concentration of the components. Different rates of antisolvent addition were monitored and the resulting solid-state form was characterized using Raman spectroscopy and DSC. Raman spectroscopy was used to monitor dehydration during storage of the product crystals. The current study demonstrates the advantages of using Raman spectroscopy to monitor the solution phase during crystallization and simultaneously monitoring the solid-state form.
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| 12. |
- Feng, Lili, et al.
(författare)
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ATR-FTIR for determining optimal cooling curves for batch crystallization of succinic acid
- 2002
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Ingår i: Crystal Growth & Design. - : American Chemical Society (ACS). - 1528-7483 .- 1528-7505. ; 2:5, s. 449-452
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Tidskriftsartikel (refereegranskat)abstract
- The temperature profile applied during batch cooling crystallization affects the supersaturation level, which in turn affects the crystal size distribution. It is possible, in principle, to calculate the optimal cooling profile; however, the nucleation and growth kinetics are rarely known to the degree of accuracy necessary for this calculation. The current study demonstrates an alternative approach to determination of the optimal cooling profile without any prior knowledge of kinetic data or subsequent modeling. An attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectrometer was used to monitor the supersaturation level during batch cooling crystallization. The ATR-FTIR was interfaced to a LABMAX automatic reactor system that was used in a feedback mode to control the cooling rate so that the supersaturation level remained close to the solubility throughout the cooling process. The resulting temperature profile corresponds to the optimal operating conditions for the maximum in the mean crystal size.
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| 13. |
- Schwartz, Albert M., et al.
(författare)
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Comparison of supersaturation profiles employed on lysozyme crystallization from a hanging drop
- 2001
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Ingår i: Crystal Growth & Design. - : American Chemical Society (ACS). - 1528-7483 .- 1528-7505. ; 1:1, s. 81-85
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Tidskriftsartikel (refereegranskat)abstract
- Fiber optic Raman spectroscopy combined with a partial least-squares regression model was used as a monitor of lysozyme concentration during crystallization in a hanging-drop experiment in real time. Raman spectral features of the buffer and protein were employed to build the regression model. The use of fiber optic technology coupled with Raman spectroscopy, which is ideal for use with aqueous solutions, results in a powerful, noninvasive probe of the changing environment within the solution. Monitoring the concentration changes of the lysozyme within the hanging drop permits a measurement of the level of supersaturation of the system and provides for the potential of dynamic control of the crystallization process. Previously, hanging-drop experiments have been monitored in real time. These experiments have given insight into the changing environment of the hanging drop as the lysozyme within the hanging drop concentrates and nucleates and as crystal growth continues. Upon alteration of the ionic strength of the reservoir, the number, size, and quality of the resultant crystals has been affected. This investigation compares the resultant supersaturation of the lysozyme crystallization within the hanging drop by employing various reservoir conditions. These conditions include a constant ionic strength reservoir, a step change in reservoir ionic strength, and a differential change in reservoir ionic strength.
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| 14. |
- Schwartz, Albert M., et al.
(författare)
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In situ monitoring and control of lysozyme concentration during crystallization in a hanging drop
- 2000
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Ingår i: Journal of Crystal Growth. - 0022-0248 .- 1873-5002. ; 210:4, s. 753-760
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Tidskriftsartikel (refereegranskat)abstract
- Fiber optic Raman spectroscopy combined with a partial least-squares regression model was demonstrated as a monitor of lysozyme concentration during crystallization in a hanging drop experiment in real time. Raman spectral features of the buffer and protein were employed to build the regression model. The use of fiber optic technology coupled with Raman spectroscopy, which is ideal for use with aqueous solutions, results in a powerful noninvasive probe of the changing environment within the solution. Lysozyme concentrations were monitored in experiments at a constant reservoir ionic strength. Data from these uncontrolled experiments were used to determine rates of supersaturation, induction times, and the number and size of the resultant lysozyme crystals. Control experiments were performed by introducing step changes in the reservoir ionic strength. The step changes were initiated by comparing in situ rates of supersaturation with the rates of supersaturation calculated from the uncontrolled data. Monitoring the concentration changes of the lysozyme within the hanging drop permits a measurement of the level of supersaturation of the system and enhances the possibility of dynamic control of the crystallization process.
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| 15. |
- Tamagawa, Rosana E., et al.
(författare)
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Raman spectroscopic monitoring and control of aprotinin supersaturation in hanging-drop crystallization
- 2002
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Ingår i: Crystal Growth & Design. - : American Chemical Society (ACS). - 1528-7483 .- 1528-7505. ; 2:4, s. 263-267
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Tidskriftsartikel (refereegranskat)abstract
- Fiber optic Raman spectroscopy is used for in situ monitoring of supersaturation during the hanging-drop crystallization of aprotinin. Schwartz and Berglund (1999) previously demonstrated this technique for lysozyme crystallization and showed it combines two critical elements for protein crystallization studies: real-time monitoring/control of supersaturation and small amounts of sample. Experiments were carried out using 10 L of protein solution. A partial-least-squares (PLS) calibration based on Raman spectra of standard solutions allowed an accurate measurement of aprotinin in a range of 2-100 mg/mL with a standard error of 0.54 mg/mL determined by a leave-one-out cross validation. A 10× microscope attached to a Raman fiber optic probe allowed the monitoring of the hanging-drop liquid phase in a noninvasive and real-time mode. Aprotinin solubility determined by measuring the protein concentration of drop solution at equilibrium decreased with increase in NaCl concentration. By continuously collecting Raman spectra of the liquid phase in the drop, the protein concentration was monitored in real time during the whole process. Control of supersaturation by manipulating the evaporation rate of the drop solution allowed the optimization of the process, leading to an increase in the resulting crystal size.
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| 16. |
- Tamagawa, Rosana E., et al.
(författare)
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Simultaneous monitoring of protein and (NH4)(2)SO4 concentrations in aprotinin hanging-drop crystallization using Raman spectroscopy
- 2002
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Ingår i: Crystal Growth & Design. - : American Chemical Society (ACS). - 1528-7483 .- 1528-7505. ; 2:6, s. 511-514
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Tidskriftsartikel (refereegranskat)abstract
- In the present study the use of fiber optic Raman spectroscopy for the in situ monitoring of aprotinin supersaturation in a hanging-drop crystallization is described. The crystallizing agent, (NH4)2SO4, is Raman active, which allows monitoring of the salt concentration in the drop during the whole hanging-drop crystallization process in addition to monitoring of the aprotinin concentration. Through the continuous measuring of protein and salt concentrations, supersaturation in the drop solution was measured in real time. Moreover, through the monitoring of protein and salt concentrations, the cocrystallization of aprotinin and (NH4)2SO4 was observed.
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| 17. |
- Wang, F., et al.
(författare)
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An investigation of solvent-mediated polymorphic transformation of progesterone using in situ Raman spectroscopy
- 2000
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Ingår i: Organic Process Research & Development. - : American Chemical Society (ACS). - 1083-6160 .- 1520-586X. ; 4:5, s. 391-395
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Tidskriftsartikel (refereegranskat)abstract
- Many analytical techniques, such as differential scanning calorimetry (DSC), X-ray diffraction (XRD), infrared spectroscopy (IR) and Raman spectroscopy can be used to differentiate between crystalline polymorphs of the same chemical entity. While all of these techniques are routinely applied to off-line analysis of materials, Raman spectroscopy has the advantage over these other techniques in that Raman technology currently exists for in situ monitoring of the solid-phase behavior within a mixed suspension of liquid and solid. In this work, we present our results from an in situ Raman study, demonstrating the solvent-mediated polymorphic phase transformation of progesterone. In situ Raman analysis has shown that the appearance of Form I progesterone is always preceded by the formation of Form II progesterone. Phase transformation rates were found to increase monotonically as the temperature increases, which indicates that the polymorphic system is monotropic. Form I was found to be thermodynamically more stable than Form II, while Form II was found to be kinetically favored over Form I. The results from this study are consistent with Ostwald's law of stages and lead to an in-depth understanding of the polymorphic transformation process of progesterone. The in situ monitoring capabilities of Raman spectroscopy have allowed us to define the processing parameters required to control the morphology of crystalline progesterone.
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| 18. |
- Wang, F., et al.
(författare)
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Monitoring pH swing crystallization of nicotinic acid by the use of attenuated total reflection Fourier transform infrared spectrometry
- 2000
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Ingår i: Industrial & Engineering Chemistry Research. - : American Chemical Society (ACS). - 0888-5885 .- 1520-5045. ; 39:6, s. 2101-2104
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Tidskriftsartikel (refereegranskat)abstract
- Nicotinic acid is crystallized by adding hydrochloric acid (HCl) to a sodium nicotinate aqueous solution. An attenuated total reflection Fourier transform infrared spectrometer is used to monitor the crystallization process of nicotinic acid. The partial least squares method is employed for IR data analysis. The solubility of nicotinic acid varies with the pH and the concentration of sodium nicotinate. The ability to measure the concentration and solubility of nicotinic acid in situ in aqueous mixtures of nicotinic acid and sodium nicotinate provides the possibility of controlling the degree of supersaturation of the solution and in turn optimizing the crystallization conditions for nicotinic acid.Nicotinic acid is crystallized by adding hydrochloric acid (HCl) to a sodium nicotinate aqueous solution. An attenuated total reflection Fourier transform infrared spectrometer is used to monitor the crystallization process of nicotinic acid. The partial least squares method is employed for IR data analysis. The solubility of nicotinic acid varies with the pH and the concentration of sodium nicotinate. The ability to measure the concentration and solubility of nicotinic acid in situ in aqueous mixtures of nicotinic acid and sodium nicotinate provides the possibility of controlling the degree of supersaturation of the solution and in turn optimizing the crystallization conditions for nicotinic acid.
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| 19. |
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| 20. |
- Nandakumar, M. P., et al.
(författare)
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Variations in plasmid content during Escherichia coli cultivations detected by on-line flow injection processing
- 2001
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Ingår i: Biotechnology Letters. - 0141-5492. ; 23:14, s. 1135-1140
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Tidskriftsartikel (refereegranskat)abstract
- An integrated flow injection process for analysis of intracellular components of microbes has been used to monitor plasmid content in Escherichia coli cultivations inoculated with cells subcultured in the presence or absence of ampicillin. The system allows sampling, sample handling, cell disruption, separation of intracellular components, and analysis in a semi-on-line mode of operation. The time scale for the assay is in the range 15 min (plasmid peak) to 25 min (complete assay cycle). As expected, lower initial plasmid content was found using an inoculum subcultured in the absence of ampicillin. More importantly, significant decrease in plasmid content was detected in the later stages of the cultivations (grown in ampicillin containing medium) even when using inoculum subcultured in the presence of ampicillin. This illustrates the versatility of the system, which allows monitoring of plasmid content as the cultivation proceeds.
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