bluuebunny/crossref_metadata_2025_split huggingface dataset:
Integration of bioconversion and downstream processing: Starch hydrolysis in an aqueous two‐phase system
Authors: Larsson Mats , Arasaratnam Vasanthy , Mattiasson Bo 
Published: May 2005

AbstractIntegration of bioconversion and the first step(s) of down stream processing can be used as a means to increase the productivity of bioprocesses. This integration also gives the possibility to run the bioconversion in a continuous mode. We demonstrate the use of an aqueous two‐phase system in combination with ultrafiltration to accomplish this. Conversion of native starch to glucose by α‐amylase and glucoamylase was carried out in an aqueous two‐phase system in connection with a membrane filtration unit. In this way, a continuous stream of glucose in buffer solution was obtained; the phase‐forming polymers as well as the starch‐degrading enzymes were recycled, and clogging of the ultrafiltration membrane was avoided. The process was carried out continuously in a mixer‐settler reactor for a period of 8 days. The enzyme activities in the top and bottom phases and in the mixing chamber were monitored intermittently throughout the experiment. The optimum pH, temperature, and ionic strength for the activity of the enzyme mixture were determined. The settling time of phase systems containing varying amounts of PEG, crude dextran, and solid starch was studied. The activity and stability of enzyme mixtures was studied both in buffer medium and in the medium containing the polymers. The enzymes were found to be more active and stable in medium containing polymers than in the buffer solutions.
Desorption of cobalt‐laden algal biosorbent
Authors: Kuyucak N. , Volesky B. 
Published: May 2005

AbstractFollowing an effective accumulation of cobalt by nonliving algal biomass of Ascophyllum nodosum, the desorption release of the metal from the biosorbent was examined using H2SO4, HCl, NH4OH, KHCO3, EDTA, KSCN, KCl, and CaCl2 solutions. The solution of CaCl2 (0.05M) in HCl appeared to be the best eluant capable of desorbing more than 96% of the sequestered cobalt at the optimum pH 2–3. The optimum solid‐to‐liquid ratio was more than 10 with the cobalt reuptake capacity of the biosorbent undiminished. The effect of temperature on the elution process and the elution rate was not significant up to 60°C. The infrared (IR) spectra of the native and the eluted biomass did not show significant differences. The electron micrographs of the algal biomass taken after washing it with the CaCl2 (0.1M) eluant solution indicated no damage to the cells and cell walls, while strong acid, alkaline, and KSCN treatment resulted in some changes in the cellular structure. The kinetics of the cobalt stripping process was quite rapid. The required contact time for the complete metal removal from the biomass was shorter than 2 h, even for the highest levels of cobalt initially deposited on the biomass.
The mechanism of cobalt biosorption
Authors: Kuyucak N. , Volesky B. 
Published: May 2005

AbstractNonliving biomass of the common seaweed Ascophyllum nodosum is capable of accumulating cobalt from aqueous solutions to the extent of 160 mg Co2+/g. Successful desorption of cobalt from the biomass by acidic CaCl2 solutions revealed that the metal uptake phenomenon is reversible, implying physical sorption of cobalt. Chemical and instrumental analysis including electron microscopy, infrared (IR) spectroscopy, X‐ray dispersion and diffraction analysis provided supporting evidence that the biosorption mechanism involves predominantly ion exchange. Alginates of the cell wall (‐COOH groups) play an important role in cobalt binding. Coordination and sorption in the cell wall structure occur simultaneously and rapidly whereas penetration of cobalt into the cell occurs at a lower rate.
Stability of immobilized maltotetraose‐forming amylase from Pseudomonas stutzeri
Authors: Kimura Takashi , Ogata Masafumi , Yoshida Masahiro , Nakakuki Teruo 
Published: May 2005

AbstractThe stability of immobilized maltotetraose (G4)‐forming amylase (1,4‐α‐D‐glucan maltoteraohydrolase, EC 3.2.1.60) from Pseudomonas stutzeri was investigated in both batch and continous processes. The inactivation process of the immobilized enzyme seemed to obey first‐order kinetics, and the immobilized enzyme became more stable when coexisting with 20–30 wt % substrate and calcium ions. From intensive studies on the operational stability in the continuous process, the apparent half‐life of G4 productivity in a constant‐flow system was mainly affected by the reaction temperature, substrate concentration, and initial immobilized enzyme activity. A new factor, immobilized enzyme stability factor fs, was proposed to evaluate the half‐life of the immobilized enzyme system.
Viscous reduction of turbulent damage in animal cell culture
Authors: Croughan Matthew Shane , Sayre Elizabeth S. , Wang Daniel I. C. 
Published: May 2005

AbstractAnimal cells are exposed to turbulent fluid flow in many cell culture processes. If the turbulence in the flow is sufficiently strong, the cells will be damaged or killed by fluid‐mechanical forces. Through an increase in viscosity, the turbulence can be damped and the hydro‐dynamic damage can be reduced. In this article, new experimental results are presented which illustrate the protective effect of thickening agents. The results follow the prediction of a model based on Kolmogorov's theory of universal equilibrium in turbulent flow fields.
Ruthenium red adsorption method for measurement of extracellular polysaccharides in sludge flocs
Authors: Figueroa Linda A. , Silverstein Jo Ann 
Published: May 2005

AbstractA nondestructive method of measuring extracellular polysaccharides (ECP) in activated sludge floes using Ruthenium Red dye adsorption was developed at the Environmental Engineering Laboratory at the University of Colorado at Boulder. The effects of pH, buffer solution, dye concentration, sludge mass, temperature, and incubation time on dye adsorption was determined. Ruthenium Red dye adsorption to bacterial floes was found to fit a Brunauer–Emmett–Teller (BET) isotherm model. Of the other environmental conditions in the system, pH was found to have the strongest effect on dye adsorption to bacterial flocs. The amount of extra cellular polysaccharides (ECP) measured by Ruthenium Red adsorption was compared with extracellular polysaccharides measured by two chemical extraction methods. Of all methods considered Ruthenium Red dye adsorption measured the highest amount of extracellular polysaccharide with the lowest amount of bacterial cell disruption. Thus, Ruthenium Red dye adsorption was more effective than extraction procedures for measurement of extracellular polysaccharides in activated sludge flocs.
Tetracycline production with sweet potato residue by solid state fermentation
Authors: Yang Shang‐Shyng , Ling Meei‐Yueh 
Published: May 2005

AbstractFor saving energy in antibiotic production and reducing the amount of agricultural wastes, solid state fermentation was used in this study to produce tetracycline with sweet potato residue by Streptomyces viridifaciens ATCC 11989. It was found that the optimal media for tetracycline production were sweet potato residue 100 g, organic nitrogen (rice bran, wheat bran, or peanut meal) 20 g, (NH4)2SO4 2.4 g, KH2PO4 0.4 g, CaCO3 1.8 g, NaCl 0.6 g, MgCl2 0.8 g, soluble starch 10 g, methionine 0.2 g, histidine 0.8 g, and monosodium glutamate 1.6 g with initial moisture content 68–72%, and initial pH 5.8–6.0. Each gram of dry weight substrate was inoculated with 1.0 × 108 conidia and incubated at 26°C for 5–7 days, producing 4720 μg of total tetracycline equivalent potency. When incubated at 26°C with the initial moisture content 68%, the conidia in solid media germinated on the second day, mycelia grew abundantly on the third day and reached stationary phase on the sixth day. The antibiotic production was consistent with the morphogenesis of S. viridifaciens: activity could be detected on the third day, had the maximal potency on the sixth day, and decreased slightly on the tenth day. (11‐3‐88 tly).
Biological phenol degradation in a gas‐liquid‐solid fluidized bed reactor
Authors: Wisecarver Keith D. , Fan Liang‐Shih 
Published: May 2005

AbstractBiological phenol degradation was performed experimentally in a gas‐liquid‐solid fluidized bed bioreactor using a mixed culture of living cells immobilized on activated carbon particles. A comprehensive model was developed for this system utilizing double‐substrate limiting kinetics. The model was used to simulate the effects of changing inlet phenol concentration and biofilm thickness on the rate of biodegradation for two different types of support particles. The model shows that gas‐liquid mass transfer is the limiting step in the rate of phenol biodegradation when the phenol loading is high.
Solubilization of fish proteins using immobilized microbial cells
Authors: Venugopal V. , Alur M. D. , Nerkar D. P. 
Published: May 2005

AbstractCells of Bacillus megaterium, Aeromonas hydrophila, and Pseudomonas marinoglutinosa were immobilized in calcium alginate. The immobilized cells secreted protease when held in fish meat suspension in water. The enzyme synthesis by the entrapped cells was supported by small amounts of soluble nutrients present in the meat. The secreted protease solubilized the fish meat, solubilization being optimum at pH range of 7.5 to 9.5 and at 50°C. Under these conditions immobilized B. megaterium was most efficient giving 30% solubilization of the meat, followed by A. hydrophila (18%), while immobilized P. marinoglutinosa was less effective. The optimum ratio of fish meat to beads was about 4:3 for B. megaterium and A. hydrophila. The beads had a storage life of 30 days at 4°C. The results suggested potential for use of immobilized microbial cells having extracellular protease activity to enhance solubility of waste proteins. A prototype reactor with beads holding assembly was fabricated which could recover the beads from the meat slurry after the treatment.
Mechanism of thermoinactivation of immobilized glucose isomerase
Authors: Volkin David B. , Klibanov Alexander M. 
Published: May 2005

AbstractIrreversible thermoinactivation of immobilized glucose isomerase from Streptomyces olivochromogenes has been mechanistically investigated at the pH‐optimum of enzymatic activity (pH 8.0). Ligands (high fructose corn syrup and the competitive inhibitor xylitol) greatly stabilize the immobilized enzyme at high temperatures. At 90°C in the presence of 2M xylitol, irreversible inactivation of immobilized glucose isomerase is caused by deamidation of its asparagine/glutamine residues. On the basis of the data obtained, it appears that the time‐dependent decay of glucose isomerase activity in industrial bioreactors is brought about by oxidation of the enzyme's cysteine residue and/or heat‐induced deleterious reactions with high fructose corn syrup or its impurities.
Selective adsorption/desorption of nucleic acids on submicron‐sized polymeric particles
Authors: Kim Chan Wha , Rha ChoKyun 
Published: May 2005

AbstractDNA can be removed or separated by the selective adsorption/desorption on positively charged submicronsized polymeric particles (SSPP). The selective adsorption of DNA, in the presence of protein, on positively charged SSPP was accomplished by increasing the concentration of potassium phosphate or sodium phosphate. The adsorption of DNA was not affected by the concentration of potassium phosphate or sodium phosphate up to 1.2M. On the other hand, the adsoprtion of a protein (bovine serum albumin) was completely impeded by 170mM potassium phosphate. DNA adsorbed on SSPP could be desorbed by increasing the concentration of NaCl or KCl, thus it can be recovered. DNA desorbed from SSPP when the concentration of NaCl or KC was higher than 0.6M. A complete desorption of DNA was achieved at the concentration of NaCl or KCl above 1.2M.
Surface effects of solvents in hydrolysis of water‐soluble lipids by candidal lipase
Authors: Uçar Tamer , Ekiz H. Ibrahim , Caglar M. Arif 
Published: May 2005

AbstractIn the study of hydrolysis of tributyrin by the lipase of Candida cylindracea, it is shown that initial rates of hydrolysis are directly proportional to the amount of enzyme adsorbed at the substrate‐water interface. As a consequence of understanding the role of the physical state of the substrate in aqueous reaction media, it was hypothesized that the inclusion of synthetic (nonsubstrate) surfaces into the reaction media may enhance the hydrolysis rate of simple liquid lipids which are partly soluble in water, like triacetin. Nonpolar n‐hydrocarbons having 5–11 carbon atoms were used to create interfaces in the hydrolysis of triacetin in the soluble range. All of the C5‐C11 hydrocarbons showed an activating effect. For quantitative evaluation of the effects of n‐hydrocarbons, n‐heptane was chosen as the model n‐hydrocarbon. Interrelations between the reaction kinetics and adsorption of the enzyme at the n‐heptane‐water interface were experimentally determined by the use of the same in‐line filtration device used for the tributyrin‐water system. At 35°C and pH 6 the relative values of the rate constants for the decomposition of enzyme‐interface‐substrate complexes were calculated as 12 and 1 for the tributyrin and n‐heptane‐triacetin systems, respectively. The nature of activation at the solvent surfaces were accounted for by a kinetic model which assumes simultaneous adsorption of enzyme and triacetin molecules at the n‐heptane‐water interface. Making use of the proposed model, the value of a the apparent Michaelis constant for the soluble triacetin‐n‐heptane system at constant n‐heptane concentration, 2 vol %, was calculated as 0.044 mol/L.
Acetone–butanol–ethanol (ABE) fermentation in an immobilized cell trickle bed reactor
Authors: Park Chang‐Ho , Okos Martin R. , Wankat Phillip C. 
Published: May 2005

AbstractAcetone–butanol–ethanol (ABE) fermentation was successfully carried out in an immobilized cell trickle bed reactor. The reactor was composed of two serial columns packed with Clostridium acetobutylicum ATCC 824 entrapped on the surface of natural sponge segments at a cell loading in the range of 2.03–5.56 g dry cells/g sponge. The average cell loading was 3.58 g dry cells/g sponge. Batch experiments indicated that a critical pH above 4.2 is necessary for the initiation of cell growth. One of the media used during continuous experiments consisted of a salt mixture alone and the other a nutrient medium containing a salt mixture with yeast extract and peptone. Effluent pH was controlled by supplying various fractions of the two different types of media. A nutrient medium fraction above 0.6 was crucial for successful fermentation in a trickle bed reactor. The nutrient medium fraction is the ratio of the volume of the nutrient medium to the total volume of nutrient plus salt medium. Supplying nutrient medium to both columns continuously was an effective way to meet both pH and nutrient requirement. A 257‐mL reactor could ferment 45 g/L glucose from an initial concentration of 60 g/L glucose at a rate of 70 mL/h. Butanol, acetone, and ethanol concentrations were 8.82, 5.22, and 1.45 g/L, respectively, with a butanol and total solvent yield of 19.4 and 34.1 wt %. Solvent productivity in an immobilized cell trickle bed reactor was 4.2 g/L h, which was 10 times higher than that obtained in a batch fermentation using free cells and 2.76 times higher than that of an immobilized CSTR. If the nutrient medium fraction was below 0.6 and the pH was below 4.2, the system degenerated. Oxygen also contributed to the system degeneration. Upon degeneration, glucose consumption and solvent yield decreased to 30.9 g/L and 23.0 wt %, respectively. The yield of total liquid product (40.0 wt %) and butanol selectivity (60.0 wt %) remained almost constant. Once the cells were degenerated, they could not be recovered.
Diffusivity of oxygen into carriers entrapping whole cells
Authors: Sun Yan , Furusaki Shintaro , Yamauchi Aizo , Ichimura Kunihiro 
Published: May 2005

AbstractThe effective diffusivity of oxygen, De, in Ca‐alginate and PVA–SbQ gels was measured using a two‐chamber vessel with a membrane between the two chambers. The effect of cell density, Cc, on De in Ca‐alginate gels was studied. The effective diffusivity of oxygen decreased with increasing cell density, to Cc = 170 kg dry cells/m3 gel. The dependency of De on cell density was discussed in terms of a random‐pore model. The model correlated well with experimental data, i.e., kDe/D0 = 0.86(1 − 1.47 × 10−3 Cc)2. Here, k is the partition coefficient, and D0 is diffusivity in water.
Optimization of fed‐batch penicillin fermentation: A case of singular optimal control with state constraints
Authors: San Ka‐Yiu , Stephanopoulos Gregory 
Published: May 2005

AbstractThe determination of the optimal feeding profile of a fed‐batch fermentation requires the solution of a singular optimal control problem that is often complicated by constraints imposed on the state variables. Such constraints can be a maximum allowable biomass concentration beyond which oxygen transfer is severely limited or maximum substrate concentration to avoid side reactions. Due to these state constraints and the singular nature of the problem, complete solutions are especially hard to obtain and almost nonexistent in the literature. In this work the feed concentration is employed as the control variable in a solution approach that first determines the optimal reactor substrate concentration and subsequently solves for the feed concentration profile that results in the optimal reactor profile. Calculations for the fed‐batch penicillin fermentation indicate sharp increases in productivity over frequently employed strategies.
ESR investigations of free and immobilized glutamate dehydrogenase
Authors: O'Connor Kim C. , Bailey James E. 
Published: May 2005

AbstractThe structure of bovine liver glutamate dehydrogenase was examined with 2,2,6,6‐tetramethyl‐4‐oxopiperidine‐1‐oxyl (TEMPO I) and 4‐((4‐(chloromercurio)benzoyl) amino)‐2, 2, 6, 6‐tetramethyl‐1‐piperidinyloxy (TEMPO II). ESR spectra from TEMPO I show that enzyme structure in the vicinity of this spin label was not distorted during immobilization to a Sepharose support. Deactivation studies with pyridoxal 5′‐phosphate indicate that immobilization did not expose additional binding sites to TEMPO I. Spectra from TEMPO II reveal that immobilization profoundly altered conformational change induced by α‐ketoglutarate and suppressed that induced by GTP and NADPH. This structural investigation provides insight into the altered kinetic properties of Sepharose‐immobilized glutamate dehydrogenase and suggests a fundamental difference between monomers and allosteric oligomers in their structural response to immobilization.
Modified extended aeration process for removal and recovery of cadmium from wastewaters
Authors: Lowe William L. , Gaudy Anthony F. 
Published: May 2005

AbstractIt has been reported in the literature that several microbial species have a considerable sorption capacity for heavy metals. Work herein reported, accomplished using a heterogeneous microbial population developed in a modified extended aeration activated sludge process, indicates sorption capabilities as good as, or better than, those for individual microbial species. The process herein described may have several advantages over pure or controlled culture processes and it offers the possibility for reuse of organic matter needed to regenerate metal‐sorbing biomass, as well as autodigestion of excess biomass. The work also indicates that acclimation to high levels of a specific heavy metal (Cd) does not confer acclimation to another heavy metal (Cu).
Gas–liquid dispersion with dual Rushton impellers
Authors: Hudcova V. , Machon V. , Nienow A. W. 
Published: May 2005

AbstractAerated and unaerated power consumption and flow patterns in a 0.56 m diameter agitated vessel containing water with dual Rushton turbines have been studied. Under unaerated conditions with a liquid height‐to‐diameter ratio of 2, an impeller spacing of 2 to 3 times the impeller is required for each to draw an amount of power equal to a single impeller. For aerated conditions, if a similar spacing is used, equations for the flooding‐loading transition and for power consumption for a single Rushton impeller can be extended relatively easily to dual systems. All results for this spacing are explained by reference to bulk flow patterns and gassed‐filled cavity structures and the proportion of sparged gas flowing through the upper impeller is also estimated. Such a spacing is generally recommended since it maximizes the power draw and hence the potential for oxygen mass transfer. Data are presented for other spacings but the results do not fit in easily with single agitator studies because strong impeller‐impeller flow pattern interactions occur.
Induced flocculation of animal cells in suspension culture
Authors: Aunins John G. , Wang Daniel I. C. 
Published: May 2005

AbstractRecycle unit operations for suspension cell cultures may be improved by flocculation of the cells. A flocculant search was conducted, and it was found that where strongly cationic polymers were severly toxic to the cells, neutral and anionic polymers were nontoxic and ineffective at flocculating the cells. A weak and poorly soluble polycation, poly‐L‐histidine, was capable of flocculating cultures of CHO, HeLa, U‐937, and CRL 1606 hybridoma cells with no toxicity to the majority of cells. In addition to the lowered acute toxicity, the polymer treatment left the cells in a growing state for recycle. Flocculation was found to be mediated by precipitates of the polymer. The low toxicity of poly‐L‐histidine is probably due to its low solubility and charge at physiological pH. Nonelectrostatic interactions may also play a role.
Interaction of infectious viral particles with a quaternary ammonium chlorid (QAC) surface
Authors: Tsao I‐Fu , Wang Henry Y. , Shipman Charles 
Published: May 2005

AbstractThe antiviral activity of a surface‐bonded quaternary ammonium chloride (QAC) was examined in this study. The mechanism of inactivation was elucidated by a combination of infectivity assay, radioactive labeling assay, and sedimentation analysis. Although the virions are still infectious when attached onto the chemically modified surface, we found these viruses are inactivated if they are eluted from the surface. The inactivation is caused by the disruption of the viral envelope with subsequent release of the nucleocapsid. No evidence indicates the released nucleocapsid is further disrupted. An enveloped virus shows a much higher affinity for the QAC‐treated surface than a nonenveloped one due to hydrophobic interaction. The QAC‐treated beads can effectively remove the enveloped viruses at low protein concentrations. The titer of herpes simplex virus was reduced by a factor of nearly 5 logarithm units in a 0.5 wt % bovine serum albumin solution with less that 10% protein loss. However, the presence of proteins in the solution reduced both the rate and capacity of this nonspecific adsorption–inactivation process. As a consequence, the removal efficiency is relatively poor in solutions with high protein content.
Subsite mapping of Aspergillus niger glucoamylases I and II with malto‐ and isomaltooligosaccharides
Authors: Meagher Michael M. , Nikolov Zivko L. , Reilly Peter J. 
Published: May 2005

AbstractGlucoamylase, industrially derived from Aspergillus niger, was chromatographically separated into forms I and II and purified to near homogeneity. Preparations were proved to be free of D‐glucosyltransferase by electrophoretic and differential inhibition tests. Maximum rates and Michaelis constants were obtained for both glucoamylases I and II with maltooligosaccharides from maltose to maltoheptaose and with isomaltooligosac‐charides from isomaltose to isomaltohexaose. Subsite maps were calculated from these kinetic data and were not significantly different for the two forms. Subsites in both forms had lower affinities for D‐glucosyl residues contained in isomaltooligosaccharides than for D‐glucosyl residues in maltooligosaccharides.