bluuebunny/crossref_metadata_2025_split huggingface dataset:
Oxygen supply to immobilized cells: 5. Theoretical calculations and experimental data for the oxidation of glycerol by immobilized Gluconobacter oxydans cells with oxygen or p‐benzoquinone as electron acceptor
Authors: Adlercreutz Patrick 
Published: December 2004

AbstractTheoretical calculations of reaction kinetics were done for one‐step reactions catalyzed by cells immobilized in spherical beads. The reactions catalyzed by free cells were assumed to obey Michaelis–Menten kinetics for a one‐substrate reaction. Both external (outside the beads) and internal (inside the beads) mass transfer of the substrate were considered for the immobilized preparations. The theoretical calculations were compared with experimental data for the oxidation of glycerol to dihydroxyacetone by Gluconobacter oxydans cells immobilized in calcium alginate gel. Glycerol was present in excess so that the reaction rate was limited by oxygen. The correlation between experimental data and theoretical calculations was quite good. The calculations showed how the overall effectiveness factor was influenced by, for example, the particle size and the cell density in the beads. In most cases the reaction rate was mainly limited by internal mass transfer of the substrate (oxygen). As shown previously, p‐benzoquinone can replace oxygen as the electron acceptor in this reaction. The same equations for reaction kinetics and mass transfer were used with p‐benzoquinone as the rate‐limiting substrate. Parameters such as diffusivity, maximal reaction rate, and K were, of course, different. In this case also, the correlation between the model and the experimental results was quite good. Much higher production rates were obtained with p‐benzoquinone as the electron acceptor compared to when oxygen was used. The reasons for this fact were that p‐benzoquinone gave a higher maximal reaction rate for free cells and the solubility of p‐benzoquinone was higher than for oxygen. Different methods of increasing the rate of microbial oxidation reactions are discussed.
Methane recovery from water hyacinth through anaerobic activated sludge process
Authors: Saraswat N. , Khanna P. 
Published: December 2004

AbstractThe concepts of phase separation, anaerobic activated sludge process, and alkali pretreatment have been incorporated in this investigation with the objective of developing rational and cost‐effective designs of diphasic anaerobic activated sludge systems, with and without alkali treatment, for methane recovery from water hyacinth (WH). Evaluation of process kinetics and optimization analyses of laboratory data reveal that a diphasic system with alkali treatment could be designed with an alkali pretreatment step (3.6% Na2CO3 + 2.5% Ca(OH)2 (w/w) of WH, 24 h duration) followed by an open acid phase (2.1 days HRT) and closed methane reactor with sludge recycle (5.7 days HRT, 7.7 days MCRT) for gas yield of 50 L/kg WH/d at 35–37°C. Likewise, a diphasic system without alkali treatment could be designed with an open acid phase (2 days HRT) followed by closed methane reactor with sludge recycle (3.2 days HRT, 6 days MCRT) for gas yield of 32.5 L/kg WH/d at 35–37°C. Detailed economic analyses bring forth greater cost‐efficacy of the diphasic system without alkali treatment and reveal that the advantage accrued in terms of higher gas yield is overshadowed by the cost of chemicals in the diphasic system with alkali treatment.
Mathematical model for internal pH control in immobilized enzyme particles
Authors: Liou J. K. , Rousseau I. 
Published: December 2004

AbstractA mathematical model has been developed for the internal pH control in immobilized enzyme particles. This model describes the kinetics of a coupled system of two enzymes, immobilized in particles of either planar, cylindrical, or spherical shape. The enzyme kinetics are assumed to be of a mixed type, including Michaelis–Menten kinetics, uncompetitive substrate inhibition, and competitive and noncompetitive product inhibition. In a case study we have considered the enzyme combination urease and penicillin acylase, whose kinetics are coupled through the pH dependence of the kinetic parameters. The hydrolysis of urea by urease yields ammonia and carbon dioxide, whereas benzylpenicillin (Pen‐G) is converted to 6‐amino penicillanic acid and phenyl acetic acid by penicillin acylase. The production of acids by the latter enzyme will cause a decrease in pH. Because of the presence of the ammonia–carbon dioxide system, however, the pH may be kept under control. In order to obtain information about the optimum performance of this enzymatic pH controller, we have computed the effectiveness factor and the conversion in a CSTR at different enzyme loadings. The results of the computer simulations indicate that a high conversion of Pen‐G may be achieved (80–90%) at bulk pH values of about 7.5–8.
Effect of nickel on biological methane generation from a laboratory poultry waste digester
Authors: Williams C. M. , Shih J. C. H. , Spears J. W. 
Published: December 2004

AbstractNickel added in concentrations as low as 10μM significantly increased biogas production in a laboratory poultry waste digester utilizing excreta from laying hens as the organic energy source. It was shown that the initial rate of biogas production increased as early as 4 h after the addition of nickel to the laboratory cultures. Analysis of the excreta for nickel content prior to addition of exogenous NiCl2 showed appreciable amounts of nickel present. The data indicate that nickel naturally present in layer excreta is suboptimal or unavailable to the bacteria for biogas production purposes.
In situ determination of kinetic parameters for biofilms: Isolation and characterization of oligotrophic biofilms
Authors: Rittmann Bruce E. , Crawford LouAnn , Tuck Cynthia K. , Namkung Eun 
Published: December 2004

AbstractThis article develops and utilizes an in situ technique to estimate the Monod half‐maximum rate concentration, Ks and the maximum specific utilization rate constant, k, for biofilms. The technique employs a curve‐matching method with kinetic results from several short‐term experiments with completely mixed biofilm reactors. Use of the in situ method eliminates the two drawbacks of using conventional suspended‐growth measurements to characterize biofilm: possible alteration of cell physiology and a major investment to run the suspended‐growth tests. Results with five cultures of biofilm‐forming oligotrophs demonstrated the in situ technique and supported the hypothesis that Ks values were lower for the biofilm oligotrophs than for typical copiotrophs.
Flow and oxygen transfer in a plunging water jet system using inclined short nozzles and performance characteristics of its system in aerobic treatment of wastewater
Authors: Ohkawa Akira , Kusabiraki Daisuke , Shiokawa Yoshihiro , Sakai Nobuyuki , Fujii Michihiro 
Published: December 2004

AbstractFor the plunging water jet system using inclined short nozzles, the flow characteristics such as the bubble penetration depth and the gas entrainment rate, which changed depending on the jet velocity, the nozzle diameter, the jet length, and the jet angle were first evaluated in an air‐water system. A comparable investigation between our results and those of existing studies used the long nozzles on those characteristics revealed that both the bubble penetration depth and the gas entrainment rate differed depending on the nozzle length; that is, the nozzle‐length‐to‐diameter ratio LN/DN and that of these characteristics the gas entrainment rate affected considerably by its magnitude and tended to be high when the nozzle of a large LN/DN ratio was used. It was also confirmed from the oxygen transfer experiments that the transfer efficiency at low jet velocities in the present water jet system was not inferior to the ones of other types of existing aeration systems; that is, the utilization of this jet aeration system to a high rate reactor for wastewater treatment or fermentation was sufficiently possible. The applicability of the plunging jet aeration method to microbial processes was then examined. As a typical example of microbial processes to be tested, the continuous treatment of an organic wastewater using activated sludge microorganisms was carried out, and the performance and related problem when this type of aeration system was applied to such a microbial process were investigated. Experimental results showed that, when viewed from the removal ability of dissolved organic matters, the plunging jet aeration system was capable of treating a wastewater of considerable high loading without the rate of oxygen transfer becoming the biooxydation‐rate‐limiting factor. Special attention was necessary for the choice of the liquid pump to be employed, however, due to the increased amount of fine suspended solids in the treated water caused by the shearing action between sludge flocks and pump blades.
Biodehalogenation of bromotrichloromethane and 1,2‐dibromo‐3‐chloropropane by Pseudomonas putida PpG‐786
Authors: Lam Tinyin , Vilker Vincent L. 
Published: December 2004

AbstractBiodehalogenation of 10−5 M concentrations of bromotrichloromethane (BTM) and 1,2‐dibromo‐3‐chloropropane (DBCP) was studied in static cultures of Pseudomonas putida PpG‐786. The experimental cultures were prepared by growing P. putida on camphor, which is known to induce the synthesis of high concentrations of cytochrome P‐450 in this bacterium. Measurements of bromide ion release were found to be approximately consistent with the amounts of halocarbon degraded. Gas chromatography/elctron capture detection (GC/ECD) measurements of hydrocarbon degradation products as a function of incubation time showed the transitory appearance of chloroform and bromodichloromethane from BTM and the transitory appearance of lower boiling but unidentified products from DBCP. The degradation of BTM to trihalomethanes and the halide ion is consistent with the enzymatic reductive dehalogenation by cytochrome P‐450 reported by others. The dependence of initial conversion rates on halocarbon concentration (0.1–2 ppm) and cell mass concentration (1–28 g cell/L) was determined by measuring the decline of parent halocarbon in stirred batch cell suspensions. The rate of DBCP conversion was up to 10‐fold higher than the rate of BTM conversion. When the intracellular, enzyme‐catalyzed conversion BTM is analyzed by the effectiveness factor of heterogeneous catalysis, the initial conversion rates measured suggest that intrinsic enzyme kinetics, rather than halocarbon permeation of the cell membrane or other diffusive processes, is rate limiting.
Fractionation of Aspergillus niger cellulases by combined ion exchange affinity chromatography
Authors: Boyer R. F. , Allen T. L. , Dykema P. A. 
Published: December 2004

AbstractEight chemically modified cellulose supports were tested for their ability to absorb components of the Aspergillus niger cellulase system. At least two of the most effective adsorbents, aminoethyl cellulose and carboxymethyl cellulose, were shown to be useful for the fractionation of cellulases. These supports apparently owe their resolving capacity to both ion exchange and biospecific binding effects; however, the relative importance of each effect is unknown. These observations form the basis for a new cellulase fractionation technique, combined ion exchange–affinity chromatography.
Evaluation of bisubstrate secondary utilization kinetics by biofilms
Authors: Namkung Eun , Rittmann Bruce E. 
Published: December 2004

AbstractA bisubstrate system having Ss1 > Smin 1 was tested with phenol and acetate as model compounds in completely mixed biofilm reactors. Two series of experiments compared the kinetics of phenol removal as a single substrate and as part of a bisubstrate system having a fixed total feed COD. Experimental results showed that, although the rate of utilization of either substrate was almost the same in a bisubstrate system as in a single substrate system, the utilization rate of either compound always was slightly greater in a bisubstrate system than in a single‐substrate system. This slight enhanced removal of an individual compound in a bisubstrate system was attributed to the extra biomass accumulated from the utilization of the other substrate. As the fraction of the feed COD contributed by an individual compound decreased in a bisubstrate system, the effluent concentration of that compound decreased and its fractional removal efficiency increased. The bisubstrate secondary‐utilization model successfully described the experimental results and explained the differences that occurred as phenol became a smaller fraction of the fixed total feed COD.
Adsorption of enzymes on krill chitin modified with carbon disulfide
Authors: Synowiecki Józef , Sikorska‐Siondalska Anna , El‐Bedawey Abo El‐Fath 
Published: December 2004

AbstractKrill chitin modified with carbon disulfide was used as a support of enzymes. The dithiocarbamino groups created after reaction of CS2 with chitinous NH2 can participate in binding the enzymes without denaturation and loss in activity. The stability of these bonds depends on pH and decreases gradually at ionic strengths higher than 0.01. Chitin modified with CS2 can be used as a support for enzymes having high activity at mild conditions of pH and ionic strength.
Biomass and lipids from lactose or whey by Trichosporon beigelii
Authors: Tahoun M. K. , El‐Merheb Z. , Salam A. , Youssef A. 
Published: December 2004

AbstractThe yeast Trichosporon beigelii produced the highest amount of biomass when grown in chemical‐defined medium with a ratio of carbon source to nitrogen source of 30:1. On the other hand, carbon‐limited medium (C–N ratio 2:1) enhanced unsaturated fatty acids synthesis. The yeast efficiently converted unsalted whey lactose to biomass, while sodium chloride in whey raised lactose assimilation to single‐cell oil (SCO).
The effect of medium composition on the acetone–butanol fermentation in continuous culture
Authors: McNeil B. , Kristiansen B. 
Published: December 2004

AbstractThe effects of growing Clostridium acetobutylicum NCIB 8052 in a chemostat under conditions of glucose, NH, PO, Mg2+, and Fe2+ limitation were examined. It was noted that limitation of any major nutrient resulted in the same fermentation pattern. Conditions where minor nutrient levels were reduced appeared to stimulate solvent production. Under conditions of Mg2+ restriction, a productive solventogenic culture was produced, with a yield of total solvents on glucose of 35.5%.
Low‐pressure airlift fermenter for single cell protein production: II. Continuous culture of pichia yeast
Authors: Chen N. Y. , Srinivasan S. , Leavitt R. I. , Coty V. F. , Kondis E. F. 
Published: December 2004

AbstractExperiments using Pichia yeast grown on n‐paraffins have been conducted in laboratory 10‐L airlift fermenters and in a 640‐L module of commercial scale. Results confirmed the design concept of combining oxygen transfer and fermenter cooling with low‐pressure air. However, in the absence of mass transport constraints, the build up of toxic factors in the fermenter appeared to be a major variable limiting cell productivity. Foaming in the large fermenter also presented a serious problem, which must be solved before low‐pressure airlift fermenters become practical.
Analysis of continuous cultures of recombinant methylotrophs
Authors: Parulekar Satish J. , Chang Yong K. , Modak Jayant M. , Lim Henry C. 
Published: December 2004

AbstractStatic and dynamic characteristics of continuous cultures of recombinant methylotrophs, which are designed to improve the selectivity of plasmid‐bearing cells and the plasmid stability, are investigated in detail. Operational regions in which coexistence (survival of plasmid‐bearing and plasmid‐free cells) operation is feasible have been identified in the entire space of kinetic parameters and operating variables. The stability characteristics of each steady state are examined. The existence of oscillatory states around the coexistence steady state is investigated using the dynamic (Hopf) bifurcation analysis. For proper startup of the continuous culture operation, it is critical to identify the sets of initial conditions, if any, which lead to transients that ultimately result in washout of plasmid‐bearing cells and avoid such conditions. For the numerical illustrations presented, the coexistence steady state happens to be locally stable over much of its region of existence, particular for the operating conditions corresponding to maximum productivity.
Suppression of pyritic sulphur during flotation tests using the bacterium Thiobacillus ferrooxidans
Authors: Townsley C. C. , Atkins A. S. , Davis A. J. 
Published: December 2004

AbstractEnvironmental concern about sulphur dioxide emissions has led to the examination of the possibility of removing pyritic sulphur from coal prior to combustion during froth flotation, a routine method for coal cleaning at the pit‐head. The bacterium Thiobacillus ferrooxidans was effective in leaching 80% and 63% −53 μm pyrite at 2% and 6% pulp density in shake flasks in 240 and 340 h, respectively.The natural floatability of pyrite was significantly reduced in the Hallimond tube following 2.5 min of conditioning in membrane‐filtered bacterial liquor prior to flotation. The suppression effect was greatly enhanced in the presence of Thiobacillus ferrooxidans. A bacterial suspension in pH 2.0 distilled water showed 85% suppression, whereas in spent growth liquor this value was 95%. The optimum bacterial density was 3.25 × 1010 cells/g pyrite in 230‐ml distilled water (2% pulp density) in the Hallimond tube. The degree of suppression by the cells was related to particle size but not to pH or temperature. The sulphur content of a synthetic coal/pyrite mixture was reduced from 10.9 to 2.1% by flotation after bacterial preconditioning. It is postulated that pyrite removal in coals which are cleaned by froth flotation could be significantly reduced using a bacterial preconditioning stage with a short residence time of 2.5 min.
Effect of activation energy microheterogeneity on first‐order enzyme deactivation
Authors: Malhotra Arun , Sadana Ajit 
Published: December 2004

AbstractThe influence of microheterogeneity on enzyme inactivation kinetics is examined. A continuous normal distribution of the thermal activation energy is assumed, and using this, a simple mathematical model is developed to find the activity–time trajectories for a microheterogeneous enzyme. Using an example, the model is used to show the quantitative effects of microheterogeneity such as increased order and stability observed during an enzyme inactivation. Experimental measurement of the extent of microheterogeneity in an enzyme sample is also discussed.
Continuous assay of neuraminidase activity by a bienzyme system immobilized in an artificial membrane
Authors: Kolisis Fragiskos N. , Thomas Daniel 
Published: December 2004

AbstractLactate dehydrogenase and NANA‐lyase were immobilized in an artificial gelantine membrane. This bienzyme system was used for continuous assay of neuraminidase activity. The K′m of the active membrane for lactate dehydrogenase and NANA‐lyase using NADH, pyruvic acid, and N‐acetylneuraminic acid as substrates were found to be 0.25mM, 0.75mM, and 2.1mM, respectively. The Km of soluble neuraminidase using sialyllactose as substrate was found to be 0.13 mM. The pH optimum for neuraminidase activity was 6.0. At 45°C the reaction rate was higher, and no denaturation phenomena of the immobolized enzymes have been observed. This bienzyme membrane was stable for several weeks stored in the reaction buffer at 4°C.
Novel anaerobic gas‐lift reactor (AGLR) with retention of biomass: Start‐up routine and establishment of hold up
Authors: Beeftink H. H. , van den Heuvel J. C. 
Published: December 2004

AbstractA start‐up routine for a novel type of anaerobic gas‐lift reactor using sand as support particles for Bacterial adhesion and involving a dilution rate shift‐up is shown to result in rapid formation of mixed‐culture aggregates from freely suspended cells. Formation of aggregates changed the general metabolism from acetate–butyrate production to acetate–propionate production. This change is attributed to a selection by washout, favoring propionate‐producing bacteria with superior adhesive properties. Sand is shown to be essential in establishing, but not in sustaining, elevated holdup ratios. The importance of maintenance processes and cellular lysis in deeper parts of aggregates are manifest from a reduced effluent biomass concentration and a pronounced production of valeric acid.
Enzymatic hydrolysis of beer brewers' spent grain and the influence of pretreatments
Authors: Beldman G. , Hennekam J. , Voragen A. G. J. 
Published: December 2004

AbstractThe enzymatic saccharification of plant material has been shown to be of interest in various fields, such as the production of fruit juices1,2 and the utilization of biomass.3 A combination of cellulase, pectinase, and hemicellulases is usually used because of the chemical composition of the matrix of plant cell walls.For apples, beet pulp, and potato fiber, almost a complete hydrolysis of polysaccharides is obtained by combining cellulose and pectinase. For nonparenchymatic tissue, the situation is somewhat different: pectin is a minor component and the hemicellulose content is much higher. Enzyme action is restricted by the lignin barrier and by the high crystallianity of cellulose in this material. For such materials, mechanical, thermal, or chemical pretreatments are necessary to achieve hydrolysis.4,5This communication describes various enzymatic treatements and chemical and physical pretreatemtn, using brewers' spent grain as substrate. Spent grain is the residue of malt and grain which remains in the mash‐kettle after the liquefied and saccharified starch has been removed by filtration.
Affinity liquid‐liquid extraction of lactate dehydrogenase on a large scale
Authors: Tjerneld Folke , Johansson Göte , Joelsson Monica 
Published: December 2004

AbstractRapid liquid‐liquid extraction of lactate dehydrogenase from muscle by using a low‐cost aqueous bipolymer two‐phase system was achieved by using a centrifugal separator. Extraction of the target enzyme into the upper phase was enhanced by including the dye Procion yellow HE‐3G (bound to polyethylene glycol). The dye acted as an affinity ligand for the enzyme. The isolation of the enzyme was carried out either by using a cell extract or by homogenizing the muscle directly in the system. The latter approach reduced the preparation time with a factor of 0.25. The two methods gave, respectively, 310 and 360 kU lactate dehydrogenase/kg muscle (measured at 22°C). By using a small centrifugal separator, Alfa Laval LAPX 202, 3–5 kg muscle could be processed/h in a 30‐L, two‐phase system.
Effect of culture phasing and a polysaccharide on production of xylanase by mixed culture of trichoderma reesei D1‐6 and aspergillus wentii Pt 2804
Authors: Panda T. , Bisaria V. S. , Ghose T. K. 
Published: December 2004

AbstractA significant increase in extracellular xylanase activity was observed in the mixed culture fermentation of Trichoderma reesei D1‐6 and Aspergillus wentii Pt 2804 when A. wentii inoculation was phased by 15 h. A. wentii produced a polysaccharide, chiefly consisting of glucose monomeric units, which was required for expression of maximum xylanase activity. Expression of high activity of xylanase in the A. wentii phased mixed culture compared to that in either T. reesei or A. wentii single cultures appeared to be controlled by the combined action of a polysaccharide produced by A. wentii and the relative growth of the two fungi in the mixed culture.