bluuebunny/crossref_metadata_2025_split huggingface dataset:
A mechanistic model of the aerobic growth of Saccharomyces cerevisiae
Authors: Bijkerk A. H. E. , Hall R. J. 
Published: December 2004

AbstractA two‐stage deterministic model of the growth of Saccharomyces cerevisiae is presented. The cell cycle of this organism was used to suggest the basic model structure. The model represents the preparatory processes of substrate uptake and conversion separately from replication and division. The regulation of the fraction of the culture devoted to each of these broad areas of metabolism, and the overall growth rate, is related to the nature and availability of the energy substrate.The simulation of respiration and glycolysis is achieved by including two alternative energy producing pathways. The regulation of these pathways is described in terms of the postulated primary regulation of the proportion of the culture required for substrate uptake and conversion, and the overall kinetic constants for each pathway. This regulation is dictated primarily by the growth rate rather than the nature or concentration of the energy substrate.The model successfully describes both batch and continuous growth of S. cerevisiae under conditions of glucose limitation and oxygen excess. A preliminary assessment indicates that adjustment of the relevant parameters will allow the model to describe the growth of S. cerevisiae on other sugars and under oxygen limitation. Similarly the model could be expected to describe the growth characteristics of other yeast species.
The tubular loop fermentor: Oxygen transfer, growth kinetics and design
Authors: Ziegler H. , Meister D. , Dunn I. J. , Blanch H. W. , Russell T. W. F. 
Published: December 2004

AbstractOxygen transfer measurements using a dynamic method and evaluated with an appropriate mathematical model have been made on a tubular loop bioreactor. Correlations of the type used in tank systems are used to describe the influence of power and aeration rate on the mass transfer coefficient. Yeast cultures grown on hydrocarbon and glucose substrates show growth characteristics similar to conventional tank results. Model considerations for large‐scale tubular fermentors allow for the prediction of the steady‐state oxygen profiles and maximum reactor length. Combination with two‐phase flow and oxygen transfer correlations yields a design procedure for commercial scale tubular loop fermentors.
Mechanism of disintegration of biological cells in ultrasonic cavitation
Authors: Doulah M. S. 
Published: December 2004

AbstractOn the basis of elastic waves released by imploding cavitation bubbles, a mechanism for biological cell disintegration in high intensity ultrasounds has been proposed. Comparison of this mechanism with the published results on yeast cells shows many points of agreement suggesting that yeast cell disintegration in ultrasonic cavitation occurs by shear stresses developed by viscous dissipative eddies arising from shock waves.
Oxygen transfer coefficients by dynamic model moment analysis
Authors: Dang N. D. P. , Karrer D. A. , Dunn I. J. 
Published: December 2004

AbstractA new method to estimate the oxygen transfer coefficient (KLa) from the experimental dynamic response data is presented. Employing a linear model which allows for gas phase, diffusion film, and oxygen electrode dynamics, the first moment of the response curve is simply related to the sum of the model parameters. Two separate experiments are used to characterize the measurement dynamics and to measure the unknown KLa parameter. The simple calculation procedure involves only measuring the area above the response curves.
Isolation of a yeast‐lyzing Arthrobacter species and the production of the lytic enzyme complex in batch and continuous‐flow fermentors
Authors: Rowley B. I. , Bull A. T. 
Published: December 2004

AbstractA gram‐negative bacterium strongly lytic toward living cells of the food yeast Saccharomyces fragilis was isolated by continuous‐flow enrichment from compost. The organism was identified as a species of Arthrobacter. The extracellular lytic enzyme complex produced by this bacterium contained β‐1,3‐glucanase, mannan mannohydrolase, and proteolytic activities. The polysaccharases were inducible by whole yeast cells. In chemostat cultures on chemically defined media, synthesis of the polysaccharases was very slight and only detectable at dilution rates below 0.02 hr−1. Enzyme production in defined media was not solely dependent on growth rate but also was influenced by the growth limiting substrate and the culture history. The production of individual depolymerases and of the lytic activity was studied in batch and chemostat cultures containing yeast as the limiting substrate. The maximum specific growth rate of the Arthrobacter under these conditions was 0.22 hr−1. β‐1,3‐Glucanase and proteolytic activities were synthesized by exponentially growing bacteria but maximum lytic titers did not develop until the specific growth rate was declining, at which time mannan mannohydrolase syntheses was induced. In yeast limited chemostats polysaccharase syntheses were greatest at the lowest dilution rates examined, namely 0.02 hr−1. Further optimization of enzyme production was achieved by feeding the Arthrobacter culture to a second‐stage chemostat. A comparison of lytic enzyme productivities in batch and chemostat cultures has been made.
Characteristics of unbuffered gel‐immobilized urease particles. II. Overall rate of reaction
Authors: Atkinson B. , Rousseau I. 
Published: December 2004

AbstractThe overall rates of reaction of unbuffered gel‐immobilized urease particles have been investigated with the aid of a packed‐bed differential recycle reactor. Both substrate and enzyme concentrations have received attention. Cylindrical gel particles contained within impermeable tubelets were used to provide the physical strength necessary for the packed‐bed arrangement and a one dimensional diffusion path to aid understanding of the complex interactions between substrate and product diffusion, and their effect on the reactions taking place. The experimental data have been interpreted with the aid of an enzyme rate equation (ERE) which relates the free solution characteristics of the enzyme to the conditions within a diffusion limited particle. The internal hydrogen ion profiles have been accommodated by a lumped parameter, the apparent pH (pHapp). Two methods have been suggested for the calculation of pHapp and the loss of activity on particle preparation, these methods are based on the use of the ERE in conjunction with experimental data.
Hydrolysis of cellulose in a cellulase‐bead fluidized bed reactor
Authors: Karube Isao , Tanaka Shigeru , Shirai Takashi , Suzuki Shuichi 
Published: December 2004

AbstractCellulase was immobilized in a collagen fibril matrix, and no leakage of cellulase from the collagen fibril matrix was observed. The immobilized cellulase was more stable than the native cellulase. The substrate cellulose was hydrolyzed quantitatively with immobilized cellulase. The final reaction product was identified as glucose. Immobilized cellulase was used in a fluidized bed reactor where the pressure drop of the fluidized bed reactor was low and constant. Cellulose was hydrolyzed to glucose by the cellulase‐bead fluidized bed reactor. The minimum flow velocity (Umf) was 0.5 cm/sec and the optimum flow velocity of the cellulose hydrolysis was 1 cm/sec.
Competition for mixed substrates by microbial populations
Authors: Yoon H. , Klinzing G. , Blanch H. W. 
Published: December 2004

AbstractA model for the growth of an organism on multiple substrates was developed, assuming that each substrate has a competitive inhibition effect on the uptake of other substrates. The model was extended to examine mixed substrates, showing that the coexistence of several species at steady state in continuous cultures is possible, even when all the organisms all strongly prefer the one substrate. The diversity of nutrient sources in a real system may be a key factor in supporting a heterogeneous microbial population.
Emulsifying and surface active agents from Corynebacterium hydrocarboclastus
Authors: Zajic J. E. , Guignard Hélène , Gerson D. F. 
Published: December 2004

AbstractA Corynebacterium hydrocarboclastus culture isolated in our laboratory (see, Zajic and Knettig, Developments in Industrial Microbiology, 1971, p. 87) has been shown to produce an extracellular biopolymer with emulsifying properties when grown on a mixture of linear hydrocarbons. This microorganism was found to grow well on a variety of carbohydrates and hydrocarbons. However, the best substrates were pure linear hydrocarbons and particularly, n‐C12, n‐C13, and n‐C14. The substrates supporting good growth gave good polymer production. Maximum cell mass of 10–11 g/liter and a maximum amount of polymer of 5–6 g/liter were recorded. The polymers recovered from the different substrates were found to be complex molecules or mixtures with a protein, a lipid, and a carbohydrate moiety. All the polymers are surface active and have two critical micelle concentrations.
Some observations on oscillatory changes in the growth rate of Saccharomyces cerevisiae in aerobic continuous undisturbed culture
Authors: Borzani Walter , Gregori Rosana E. , Vairo Marina L. R. 
Published: December 2004

AbstractOscillatory changes in the growth rate were observed in undisturbed continuous culture of Saccharomyces cerevisiae on sugar‐cane molasses media when nitrogen sources (2.56 to 6.17 g/liter of ammonium sulfate or 1.22 g/liter of urea) were added to the feeding mash and when the air rate was 1.3 to 1.6 v/v/m. The oscillations were not affected by the addition of yeast extract. The suppression of the nitrogen source during the continuous test leads to a nonoscillatory transient state. No oscillations occurred at all when no nitrogen source was added to the medium and/or the air rate was equal to zero or equal to about 3.3 v/v/m. The oscillatory responses of the system were affected by a previous anaerobic continuous cultivation of the yeast.
Thirty liter tower‐type pilot plant for the mass cultivation of light‐ and motion‐sensitive planktonic algae
Authors: Jüttner Friedrich 
Published: December 2004

AbstractA simple, low‐priced 30 liter tower‐type algal pilot plant for the cultivation of light‐ and motion‐sensitive species is described. Two hundred g wet weight of Microcystis aeruginosa were obtained per harvest. Since the self‐shading of denser cultures could be compensated for only to a limited extent by increasing the light intensity without damaging the cells, the efficiency of various culture‐vessel widths was determined for the growth of Microcystis : the best results were obtained with a width of 3.5 cm. Light requirements of Microcystis were studied in shadowless suspensions. The compensation point of photosynthesis varied between 200 and 300 lx, depending on the preillumination, whereas the light saturation point was found to be near 4000 Ix. The light optimum for photosynthesis was not identical with that for good growth.
Influence of lactose hydrolysis and solids concentration on alcohol production by yeast in acid whey ultrafiltrate
Authors: O'leary V. S. , Sutton C. , Bencivengo M. , Sullivan B. , Holsinger V. H. 
Published: December 2004

AbstractAlcohol yields of 6.5% were obtained with Saccharomyces cerevisiae in lactasehydrolyzed acid whey permeate containing 30–35% total solids. Maximum alcohol yields obtained with Kluyveromyces fragilis were 4.5% in lactase‐hydrolyzed acid whey permeate at a solids concentration of 20% and 3.7% in normal permeate at a solids concentration of 10%. Saccharomyces cerevisiae efficiently converted the glucose present in lactase‐hydrolyzed whey permeates containing 5–30% total solids (2–13% glucose) to alcohol. However, the galactose, which comprised about half the available carbohydrate in lactase‐hydrolyzed whey, was not utilized by S. cerevisiae, so that even though alcohol yields were higher when this organism was used, the process was wasteful in that a substantial proportion of the substrate was not fermented. For the process to become commercially feasible, an efficient means of rapidly converting both the galactose and glucose to alcohol must be found.
CO2 Transport and photosynthetic productivity of a continuous culture of algae
Authors: Märkl H. 
Published: December 2004

AbstractThe photosynthetic activity of a continuous culture of the microalga Chlorella vulgaris as it is influenced by the CO2 concentration in the aerating air at different light levels is discussed. It is shown that the characteristic of this behavior is mainly determined by the CO2 transport from the air to the algal cell. Therefore the critical CO2 concentration necessary for optimal growth of a particular alga cannot be given in general, as it differs over a very wide range depending on the dispersion system used in the culture vessel. By analyzing experimental data by means of a mathematical model the overall transport coefficient in a well stirred system for the CO2 transport from the air bubble to the algal cell and the “actual” CO2 kinetics, can be calculated within reasonable limits of accuracy.
Poly(methoxygalacturonide) lyase immobilized via titanium onto solid supports
Authors: Hanisch W. H. , Rickard Pamela A. D. , Nyo S. 
Published: December 2004

AbstractPoly(methoxygalacturonide) lyase (PMGL) (E.C. 4.2.2.10) was purified from a commercial preparation and immobilized by the metal link method. The properties of DEAE‐cellulose‐Ti‐PMGL and of porous glass‐Ti‐PMGL were compared with those of the native enzyme; despite the presence of the metal and the heterogeneity of the substrate, pectin, typical substrate–enzyme‐support interactions were demonstrated by shifts in pH optima and KM values. The possible industrial application of DEAE‐cellulose‐Ti‐PMGL is discussed.
Process for the aerobic conversion of poultry manure into high‐protein feedstuff
Authors: Shuler M. L. , Roberts E. D. , Mitchell D. W. , Kargi F. , Austic R. E. , Henry A. , Vashon R. , Seeley H. W. 
Published: December 2004

AbstractA two‐stage aerobic continuous process is suggested for the conversion of poultry waste into a single‐cell protein (SCP) product. The technical feasibility of the process is examined in this paper. Using bench‐scale apparatus the approximate growth kinetics have been discovered. Possible modes of product recovery have been examined. The product consists primarily of a strain of Pseudomonas fluorescens which has a lysine‐rich (∼9.3%) amino acid profile that could make this product an attractive feed ingredient for poultry diets.
Steroid bioconversion in water‐insoluble organic solvents: Δ1‐Dehydrogenation by free microbial cells and by cells entrapped in hydrophilic or lipophilic gels
Authors: Yamané Tsuneo , Nakatani Hideki , Sada Eizo , Omata Tetsuo , Tanaka Atsuo , Fukui Saburo 
Published: December 2004

AbstractA cell suspension in a water‐insoluble organic solvent (benzene: n‐heptane, 1 : 1 by volume) of Nocardia rhodocrous (previously induced to synthesize steroid Δ1dehydrogenase) rapidly catalyzed the stoichiometric oxidation of 4‐androstene‐3,17‐dione (4‐AD) to androst‐l,4‐diene‐3,17‐dione (ADD) in the presence of phenazine methosulfate (PMS). High levels of 4‐AD or PMS reduced the conversion rates. No appreciable decrease in the conversion rate was observed on adding aqueous buffer solution to the thawed ceils (up to 9.4 g water/g dry cell). The whole cells were immobilized by entrapment in a hydrophilic gel (H‐gel) or a lipophilic gel (L‐gel) by use of a water‐soluble or water‐insoluble photocrosslinkable prepolymer. The reticula of H‐ and L‐gel matrices were impregnated with water and organic solvent, respectively. Both the H‐ and L‐gels could convert 4‐AD to ADD in the presence of PMS, the L‐gel showing a slightly higher conversion rate. Various lines of evidence indicate that the limiting factor is the penetration rate of 4‐AD into gel particles for the H‐gel, and the penetration rate of PMS for the L‐gel. The catalytic activities decreased considerably after several successive runs with the free cell suspension system, while the immobilized cells were more stable, the stability of H‐gel and L‐gel being almost the same.
The role of interphase nitrogen transport in the dynamic measurement of the overall volumetric mass transfer cefficient in air‐sparged systems
Authors: Linek V. , Beneš P. , Hovorka F. 
Published: December 2004

AbstractIt has been shown both theoretically and experimentally that interphase nitrogen transport may have a significant influence on the rate of interphase oxygen transport, and thereby also on the value of the volumetric mass transfer coefficient of oxygen, kla, determined in mechanically agitated bubble fermentors using the variants of dynamic method presented in the literature. The experiments were carried out in 1M KCI solution at five stirrer frequencies and two gas inlet levels. The gas interchanges were performed either without interrupting the aeration and agitation of the charge (A) or with the aeration and agitation of the charge turned on at the same time (B). The applied variants of the interchange were N2→ O2→, O2→ N2, N2→ air, air→ N2, O→ O2, and O→ air. In the two last variants the oxygen dissolved in the charge was removed by reacting with sulfite ions. The kla values calculated by allowing for the nitrogen transport for procedure A were approximately equal to the values obtained by disregarding the nitrogen transport, whereas those for procedure B were higher (up to 40%), than the values obtained disregarding the nitrogen transport.
Use of immobilized cells of Rhizopus nigricans for the 11α‐hydroxylation of progesterone
Authors: Maddox I. S. , Dunnill P. , Lilly M. D. 
Published: December 2004

AbstractThe filamentous fungus, Rhizopus nigricans, was immobilized in polyacrylamide, alginate, and agar gels and its ability to 11α‐hydroxylate progesterone was examined. No activity was detected using polyacrylamide gel but both agar and alginate gels have proved capable of hydroxylation. Agar gels displayed faster rates and higher yields. It was possible to induce hydroxylase synthesis within agar and alginate gels, and microscopical examination provided evidence for hyphal growth within these gels. The concept of increased biomass was used to explain the observed increase in the rates of hydroxylase activity of the immobilized cells. Conversely, hyphal overcrowding was postulated for the rapid inactivation observed under some operating conditions.
The dynamics of commensalism
Authors: Stephanopoulos Gregory 
Published: December 2004

AbstractThe outcome of the interaction of two commensal populations growing in a continuous bioreactor depends on the operating conditions (dilution rate and feed concentration) and the shape and mutual disposition of the specific growth rate curves of the two populations. The stability of the possible steady states is analyzed by a new method based on the Poincaré index and a comprehensive portrait of the dynamics of the interaction of commensalism is presented. Potential operating difficulties and associated control problems are discussed.
Shear disruption of soya protein precipitate particles and the effect of aging in a stirred tank
Authors: Bell D. J. , Dunnill P. 
Published: December 2004

AbstractAn improvement in the resistance of isoelectric soya protein precipitate to capillary shear disruption was achieved by aging in a stirred tank. The aggregate strength was found to depend on the extent and duration of agitation prior to exposure to shear. An optimum value of an aging parameter Gt ∼ 105 was determined, where G is the rms velocity gradient in the aging vessel and tis the time of aging. The disruption of precipitate aggregates by exposure to high rates of shear for short times was dependent on the rate of shear and time of exposure. The dominant mechanism of aggregate breakup was fragmentation, with erosion occurring to a lesser extent. The size of the fragments produced by shear disruption was weakly dependent on the rate of shear, with higher rates of shear producing smaller fragments.
The immobilizaton of enzymes, bovine serum albumin, and phenylpropylamine to poly(acrylic acid)–polyethylene‐based copolymers
Authors: Beddows C. G. , Gil M. H. , Guthrie J. T. 
Published: December 2004

AbstractA poly(acrylic acid)–polyethylene graft copolymer was prepared and used initially to couple to acid phosphatase, using soluble carbodiimides. Yields which were quite good were obtained with CMC but not with EDAC. The copolymers was used to couple trypsin using EEDQ. Several organic solvents were investigated for the preparation of the “activated” poly(acrylic acid) intermediate. Using the activated system, high concentrations of trypsin were bound but the relative activities were not very high. The yield was good with bovine serum albumin (BSA). When the method was used for invertase, acid phosphatase, and alkaline phosphatase, the yields were poor and the copolymer was shown to absorb protein by an ion‐exchange mechanism. However, the activated system gave a good yield of coupling to phenylpropylamine. A polyethylene‐coacrylic‐acid polymer containing 13% of acrylic acid (by weight) was then converted to the acid chloride by refluxing with thionyl chloride. The chlorinated copolymer which contained 0.7% chlorine and a thionyl‐chloride‐treated polyethylene control which contained no chlorine were investigated in immobilization studies. Such coupling involved bovine serum albumin (BSA), alkaline phosphatase, trypsin, β‐galactosidase, and invertase. Bovine serum albumin coupled well to the support, but none of the enzymes gave high levels of enzymes activity. Phenylpropylamine coupled well and all of the acid chloride groups were involved. Tyrosine reacted with 63% of the available acid chloride groups.
Enzymatic hydrolysis of cellulose and various pretreated wood fractions
Authors: Saddler J. N. , Brownell H. H. , Clermont L. P. , Levitin N. 
Published: December 2004

AbstractThree strains of Trichoderma—T. reesei C30, T. reesei QM9414, and Trichoderma species E‐58—were used to study the enzymatic hydrolysis of pretreated wood substrates. ach of the culture filtrates was incubated with a variety of commercially prepared cellulose substrates and pretreated wood substrates. Solka floc was the most easily degraded commercial cellulose. The enzyme accessibility of steam‐exploded samples which had been alkali extracted and then stored wet decreased with the duration of the steam treatment. Air drying reduced the extent of hydrolysis of all the samples but had a greater effect on the samples which had previously shown the greatest hydrolysis. Mild pulping using 2% chlorite increased the enzymatic hydrolysis of all the samples. Steam explosion was shown to be an excellent pretreatment. The results indicate that the distribution of the lignin as well as the surface area of the cellulosic substrate are important features in enzymatic hydrolysis.