bluuebunny/crossref_metadata_2025_split huggingface dataset:
Mass transfer in a rectangular air‐lift reactor: Effects of geometry and gas recirculation
Authors: Siegel Marc H. , Merchuk Jose C. 
Published: December 2004

AbstractThe interrelationships between the three parts of the air lift reactor, the riser, the downcomer, and gas–liquid separator, were examined with relation to the overall mass transfer in the reactor. This involved studying the mass transfer of oxygen from the gas phase to the liquid phase for 20 different reactor geometries. Both one‐ and two‐sparger systems were studied. It was demonstrated that the gas–liquid separator plays a major role in reactor behavior and must be considered in reactor design. It was found that the overall reactor mass transfer coefficient KLA could be correlated to the pneumatic power of gas input per total dispersion volume (P/VD) and to the true riser superficial gas velocity JGR for all experimental conditions examined. The KLA is directly related to the P/VD with an exponent of approximately 1. “Two‐sparger” systems, where an auxiliary gas sparger is placed near the downcomer entrance, have higher ab solute values for KLA than single‐sparger systems.
The kinetics and mechanism of shear inactivation of lipase from Candida cylindracea
Authors: Lee Yuan‐Kun , Choo Choon‐Liang 
Published: December 2004

AbstractShearing experiments were conducted in a stirred tank reactor with 0.1% lipase solutions of Candida cylindracea. Inactivation of the lipase solutions were observed at various shear rates from 50 to 150 s−1 after continuous shearing for ca. 30‐240 min under optimal pH and temperature conditions. However, there was no shear stress denaturation of the lipase when it was subjected to shear stresses of 0.72‐109.2 kg/m/s2 and shear rate of 100 s−1. In the presence of polypropylene glycol, the rate of denaturation of the lipase decreased by 93%. When the lipase solution was filled to the brim, the rate of denaturation of the lipase decreased by 97% compared to that when reactor was half‐filled. The rate of denaturation of the lipase decreased by 61% when probes in the fermentor were removed. There was no significant difference in the rate of denaturation of the lipase under ambient conditions compared with that in the absence of oxygen, or in the absence of free metal ions. Recovery of lipase activity from the first hour of shearing was observed at a shear rate of 150 s−1. The native lipase and the lipase which had recovered its activity showed similar pH profiles, temperature profiles, and activation energies. Temperature was found to have no effect in the rate of shear‐induced denaturation of the lipase in the range 20 to 30°C during shearing at 100 s −1and optimal pH. Above 30°C, the rate of denaturation of the lipase increased drastically as a function of temperature. The significance of the findings in the de sign of reactor systems for hydrolysis or esterification of oils by lipase will be discussed.
The use of the maharanobis and modified distances for the improvement of simulation of glutamic acid production
Authors: Kishimoto Michimasa , Alfafara Catalino G. , Nakajima Mikio , Yoshida Toshiomi , Taguchi Hisaharu 
Published: December 2004

AbstractA modified simulation procedure based on a statistical approach was investigated. The procedure predicts the time course of fed‐batch culture for glutamic acid production by a temperature‐sensitive strain of Brevibacterium flavum. The statistical approach requires only a data base of state points obtained in experiments, and not perfect identification of fermentation models. The simulation procedure is based on regression analysis to estimate specific rate parameters of system equations using the data points selected with reference to the Euclid distance. It was modified in that the data selection procedure included the use of the Maharanobis distance as well as a modified distance defined in this study. Simulation results using the modified procedure allow reasonable prediction of the time course of fed‐batch culture for glutamic acid compared to that involving the Euclid distance alone.
Estimating cell and product yields
Authors: Andrews G. 
Published: December 2004

AbstractThe balance equations for carbon, reduction potential, and energy during cell growth and product formation are rederived in a general form. Cells are treated simply as a very complex product, and the YATP concept is extended to products. Limitations on the theoretical yield are discussed for different product types. Simple aerobic products cannot be energy limited unless the maintenance requirement is large, while complex products cannot be reduction limited. A maximum yield is defined for products much more oxidized than their substrate (carbon limited) because the theoretical yield conditions may violate the energy balance. For reduced complex products the yield on available electrons is related to YATP, the P/O ratio, and the product composition. Narrow bounds are established on the actual yields in simple anaerobic fermentations, and the significance of the yields in the linear growth equation is discussed.
Immobilization of endo‐polygalacturonase from Aspergillus niger on various types of macromolecular supports
Authors: Pifferi Pier Giorgio , Tramontini Maurilio , Malacarne Alberto 
Published: December 2004

AbstractEndo‐polygalacturonase (endo‐PG) was immobilized on a wide range of natural and synthetic macromolecular supports and their modified derivatives representing many chemical classes, including esters, amides, phenols, alkyl‐ and arylamines, and carboxyl derivatives. The immobilization entailed methods of adsorption alone as well as covalent bond formation using glutaraldehyde or carbodiimide or via the diazo‐coupling reaction. The most promising system proved to be immobilization on trimalehylchitosan (TMC) via adsorption followed by treatment with glutaraldehyde (GA). The binding capacity of the support is on the order of 13,000 IU/g, half of which is active. Various properties of immobilized endo‐PG were evaluated. The optimum pH of the enzyme shifted to the alkaline side. The relative catalytic activity was considerably high even at room temperature and remained so above 70°C. The thermal stability at pH 3‐4 was notably improved by immobilization, the half‐time doubling. Finally, the apparent Km was greater for immobilized endo‐PG than for native enzyme, while the Vmax was smaller for the immobilized enzyme.
High enthalpy and low enthalpy death in Saccharomyces cerevisiae induced by acetic acid
Authors: Pinto Isabel , Cardoso Helena , Leão Cecélia , van Uden N. 
Published: December 2004

AbstractAcetic acid at concentrations as may occur during vinification and other alcoholic yeast fermentations induced death of glucose‐grown cell populations of Saccharomyces cerevisiae IGC 4072 at temperatures at which thermal death was not detectable. The Arrhenius plots of specific death rates with various concentrations of acetic acid (0–2%, w/v) pH 3.3 were linear and could be decomposed into two distinct families of parallel straight lines, indicating that acetic acid induced two types of death: (1) High enthalpy death (HED) predominated at lower acetic acid concentrations (> 0.5%, w/v) and higher temperatures; its enthalpy of activation (ΔH≠) approached that of thermal death (12.4 × 104 cal/mol); (2) Low enthalpy death (LED) predominated at higher acetic acid concentrations and lower temperatures with ΔH≠ of 3.9 × 104 cal/mol. While the ΔH≠ values for HED induced by acetic acid were similar with those reported earlier for HED induced by other fermentation endproducts, the values for the entropy coefficients were different: 127–168 entropy units mol−1L for acetic acid as compared with 3.6–5.1 entropy units mol−1L for ethanol, which agreed with experimental results indicating that acetic acid is over 30‐times more toxic than ethanol with respect to yeast cell viability at high process temperatures.
Automatic on‐line growth estimation method for outdoor algal biomass production
Authors: Guterman H. , Ben‐Yaakov S. , Vonshak A. 
Published: December 2004

AbstractAn on‐line measuring procedure for estimating productivity in outdoor algal cultures was developed and tested experimentally. The procedure is based on a previously described method for on‐line measuring net O2 production rate (OPR). The data obtained by this method was found to correlate well with the conventional procedures for estimation productivity by measuring the changes in biomass concentration in the culture. The new procedure seems to be superior to the latter since it can be carried out in an almost continuous way and can give immediate indication on the productivity. OPR could be used to monitor on‐line the photosynthetic and/or respiration activity in small research fermentors or in large‐scale open systems outdoors.
Oxidation of benzyl alcohol by whole cells of Pichia pastoris and by alcohol oxidase in aqueous and nonaqueous reaction media
Authors: Duff Sheldon J. B. , Murray William D. 
Published: December 2004

AbstractThe low substrate specificity of alcohol oxidase from Pichia pastoris makes this enzyme system of potential biotechnological interest. Whole cells of Pichia pastoris are able to oxidize benzyl alcohol to benzaldehyde in aqueous reaction media. The low water solubility of the reactant and product of this bioconversion, combined with the ability of both to strongly inhibit the reaction, favor the use of nonaqueous reaction fluids. Purified alcohol oxidase was shown to function in a number of 2‐phase reaction systems of varied aqueous to organic phase ratios (0.01–0.05 v/v). The apparent Vmax and Km were 5.26 g/Lh and 7.41 g/L respectively, for the oxidation of benzyl alcohol to benzaldehyde in hexane containing 3% aqueous phase. The volume of the aqueous phase had a strong effect on the reaction, with an aqueous: organic ratio of 3–5% found to be optimum. The enzyme could be firmly immobilized on DEAE‐Biogel (Biorad) to enhance stability and biocatalyst recovery.
On‐line analysis of avermectin fermentation cell growth kinetics in an industrial pilot plant
Authors: Gbewonyo K. , Jain D. , Hunt G. , Drew S. W. , Buckland B. C. 
Published: December 2004

AbstractExperimental data are presented which show that on‐line calculation of oxygen uptake rate can be used to estimate the cell concentration of Streptomyces avermitilis during the active growth phase of this fermentation. Moreover, by dividing the oxygen uptake rate by the total oxygen consumed, an on‐line estimate of specific growth rate of this culture can be generated. A theoretical basis is provided for this model. Use of a mass spectrometer for vent gas analysis coupled with computer data acquisition has made this information both very accurate and readily available. Examples are given which illustrate the kinetics of the avermectin fermentation as well as the effect of a temperature shift on the specific growth rate.
Characteristics of tyrosinase in AOT–isooctane reverse micelles
Authors: Bru Roque , Sanchez‐Ferrer Alvaro , García‐Carmona Francisco 
Published: December 2004

AbstractIsooctane–AOT–H2O is a suitable system for studying enzyme behavior in organic solvents. Tyrosinase was able to catalyze a well‐known reaction in aqueous medium: oxidation of 4‐methylcatechol to yield 4‐methyl‐o‐benzoquinone. This reaction was studied using the preceding ternary system with adequate amounts of each component to make up reverse micelles. 4‐Methyl‐o‐benzoquinone stability was demonstrated in isooctane even at alkaline pH values. Apparent Km and Vmax were similar to those in water, but substrate inhibition was more evident. The pH and temperature appear to be shifted toward high and low values, respectively. Characteristic parameters of reverse micelles, ω0 (= H2O/AOT) and percentage of H2O (v/v), were investigated. The results obtained showed that the steady‐state rate varies either with ω0 or with percentage of H2O. The variation observed with ω0 showed an optimal value while an increase in percentage of H2O can lead to decreased or increased activity depending on substrate concentration.
A flow injection analysis system for fermentation monitoring and control
Authors: Garn Morten , Gisin Marcus , Thommen Christian , Cevey Pierre 
Published: December 2004

AbstractAn automated analysis system for on‐line fermentation monitoring is presented. The modular system consists of an in‐line sterilizeable crossflow microfilter, a selection valve that allows injection of sample or standards, a degassing unit, a dilution module, and a FIA manifold with a spectrophotometric UV/VIS detector. In the dilution module samples are conditioned and diluted depending upon concentration of analyte and the working range of the analyzer. Methods for the monitoring of glucose, ethanol, ammonia and phosphate are described. Results from the monitoring of glucose and their use in fermentation control are presented. The maximal analysis frequency is 30 samples per hour including the dilution of 1 : 200. Detection limits are 5 mg/L for ethanol and glucose, 1 mg/L for phosphate and 50 mg/L for ammonia.
Cross‐flow membrane microfiltration of a bacteriol fermentation broth
Authors: Nagata Naohiko , Herouvis Kay J. , Dziewulski David M. , Belfort Georges 
Published: December 2004

AbstractAlthough cross‐flow membrane filtration is a very attractive option for harvesting cells and recovering enzymes from cell homogenates, the process is not without its problems. Foremost of these is the deposit of dissolved and suspended solutes onto the membrane surface during operation. The formation of these dense and sometimes compressive sublayers (often called cakes) offers additional resistance to axial and permeate flows and often affects the retention characteristics of the process. In view of the complex nature of the sublayer formation process and its sensitivity to cross‐flow velocity, this investigation was undertaken to determine the main factors responsible for the decline in performance during the harvesting of B. polymyxa broth by membrane microfiltration. System parameters varied include axial flow rate, concentration of cells, proteins and other components in the feed, membrane materials (ceramic, polypropylene, and stainless steel), and cleaning methods. To help explain the observed results, a new mass transport model—the solids flux model—based on the assumptions that back migration of particles from the sublayer or membrane surface is negligible and that particles that reach the solid–solution interface attach (stick) completely, is tested. Using a variety of diagnostic methods, magnesium ammonium phosphate precipitate is formed during steam sterilization of the medium and is implicated as the major foulant in this study.
Improvement of proteolytic resistance of immunoadsorbents by chemical modification with polyethylene glycol
Authors: Kondo Akihiko , Kishimura Masaaki , Katoh Shigeo , Sada Eizo 
Published: December 2004

AbstractImmunoadsorbents were modified with monomethoxy‐polyethylene glycol (PEG; average molecular weights of 5000 (PEG‐5000) and 1900 (PEG‐1900)) activated with cyanuric acid (activated PEG) by four different methods. In the two methods, anti‐BSA antibodies were modified with activated PEG with and without protection of antigen binding sites with BSA and then were coupled to CNBr‐activated Sepharose 4B. In the other two methods, Immunoadsorbents, which were prepared by coupling anti‐BSA antibodies to CNBr‐activated Sepharose 4B, were modified with activated PEG with and without the protection. The effects of PEG modification by these four methods on the binding ratio (the ratio of the numbers of moles of antigen adsorbed to the numbers of moles of binding sites of antibody coupled), the antigen binding property and the resistance to proteolytic digestion of immunoadsorbents were studied. The decrease in the binding ratio by the modification with activated PEG was small enough to use modified immunoadsorbents for industrial purification processes. The resistance to proteolytic digestion of immunoadsorbents was improved by modification with activated PEG. The modification without protection of antigen binding sites gave higher resistance to proteolytic digestion than that with protection, while the former caused larger decrease in the binding ratio of modification. The immunoadsorbents modified with activated PEG‐5000 showed higher resistance to proteolytic digestion than those modified with activated PEG‐1900.
Transcription from plasmid genes, macromolecular stability, and cell‐specific productivity in Escherichia coli carrying copy number mutant plasmids
Authors: Peretti S. W. , Bailey J. E. , Lee James J. 
Published: December 2004

AbstractExperiments were performed to evaluate, qualitatively and quantitatively, the adaptation of Escherichia coli to plasmid maintenance and cloned gene expression. Experimental findings indicate that the metabolic response to low plasmid levels is an increase of the biosynthetic capacity of both transcription and translation. At high copy number levels the gene‐specific transcription rate continues to increase but the stability of plasmid‐derived mRNA drops sharply. Protein levels are maintained, but translation efficiency decreases. These results indicate that cellular biosynthetic capacity may not be limiting productivity in recombinant systems. If macromolecular stability is the bottleneck, then current efforts to increase gene expression that focus on enhancing synthesis rates will be ineffective.
Covalent immobilization of lipase in organic solvents
Authors: Stark Maj‐Britt , Holmberg Krister 
Published: December 2004

AbstractLipase from Rhizopus sp. has been immobilized covalently on tresyl activated silica. Three different coupling media were evaluated: aqueous buffer, n‐hexane, and a microemulsion based on n‐hexane, aqueous buffer, and the nonionic surfactant triethylene glycol monododecyl ether. In addition, coupling via a very long, hydrophilic spacer arm, polyethylene glycol 1500 (PEG 1500), was compared with attachment to the silica via a short silane bridge only. The enzyme preparations were tested in hydrolysis and transesterification reactions. In the hydrolysis no marked differences in activity were found between the coupling media used. In the transesterification, on the other hand, the choice of immobilization medium had a very large effect on lipase activity, the preparation from microemulsion being the most active one. The use of the hydrophilic spacer had a large effect on activity in the hydrolysis reaction. Whereas direct coupling gave an activity of immobilized lipase of 26–34% of that of free enzyme, depending on the reaction medium, lipase bound via the spacer exhibited 56–67% activity. The latter values are considerably higher than previously reported in the literature for covalently immobilized lipase. The hydrophilic spacer had no effect on enzyme activity in the transesterification, however, a fact which is attributed to the hydrophobic medium of this reaction. The spacer is incompatible with the reaction medium and will, therefore, adsorb on the particles rather than stretch out into the bulk phase. The stability of the bound lipase was extremely good, no loss in activity being observed after a period of three weeks in aqueous solution of 37°C.
Growth of microbial populations in nonminimal media: Some considerations for modeling
Authors: Pavlou Stayros , Fredrickson A. G. 
Published: December 2004

AbstractRamkrishna and his co‐workers have developed so‐called cybernetic models which purport to describe, among other things, how microorganisms make choices when presented with two or more functionally equivalent, or substitutable, nutrients that are sources of carbon and available energy. In general, however, organisms are presented with choices not just between nutrients that are substitutable for one another, but also between sets of nutrients some of which are by no means substitutable for one another. It is postulated herein that the main ideas of cybernetic modeling apply to these more general choices as they seem to apply to the choices considered by Ramkrishna and his co‐workers. Some consequences of the postulate are worked out for steady‐state growth situations where two, or in one case three, nutrients limit or potentially limit growth rate. If predicted phenomena are observed experimentally so as to verify the postulate, a significantly improved basis for understanding growth of microorganisms in practical fermentation media as well as in natural situations will be provided by this application of cybernetic modeling ideas.
Growth and gas production for hyperthermophilic archaebacterium, Pyrococcus furiosus
Authors: Malik B. , Su W.‐w. , Wald H. L. , Blumentals I. I. , Kelly R. M. 
Published: December 2004

AbstractPyrococcus furiosus represents one of the most important hyperthermophilic bacteria isolated thus far because of its relatively high cell yields and rapid growth rates. Pyrococcus furiosus exhibits several interesting growth characteristics, especially in terms of biotic gas production, which were examined in this study. In the presence of elemental sulfur, both carbon dioxide and hydrogen sulfide production appeared to be strongly growth associated, while no significant hydrogen production was observed. In the absence of sulfur, hydrogen and carbon dioxide were produced by the organism and hydrogen inhibition was observed. The addition of elemental sulfur to the medium apparently eliminated, hydrogen inhibition as growth proceeded normally even when hydrogen was added to the gas phase. Also, no apparent substrate limitation or toxic product could be attributed to the cessation of growth as cell growth in spent media was at least as good as in fresh media. An unstructured growth model was used to correlate growth and gas production for P. furiosus in complex seawater‐based media at 98° C both in the absence and presence of elemental sulfur. The model was shown to be useful for examining some of the observations made in this study.
Microfiltration cell‐recycle pilot system for continuous thermoanaerobic production of exo‐β‐amylase
Authors: Nipkow André , Zeikus J. Gregory , Gerhardt Philipp 
Published: December 2004

AbstractA microfiltration cell‐recycle pilot‐scale system was developed comprised of a conventional continuous‐flow fermentor connected to an in situ steam‐sterilizable cross‐flow ceramic filter with a backflushing device. A microcomputer was used to control filtration pressure, tangential flow velocity, and backflushing. Performance of the system was tested with the anaerobic production of thermostable extracellular β‐amylase at 60°C by Clostridium thermosulfurogenes on maltose or malto‐dextrin media. Filtration rates during continuous cultivation were between 20 and 60 L/m2/h. The maltodextrin and cell debris occurring at high retentate flow rates or filtration pressures impaired the performance of the filter. Backflushing initially improved the permeate flux to 42% in a maltose medium and to 10% in a maltodextrin medium, but the effect diminished with time. The productivity of β‐amylase (as much as 48 U/mL/h) and concentration of biomass (as much as 14 g/L) were increased 11‐ and 12‐fold, respectively, if compared to values obtained in a chemostat. The concentration of β‐amylase rose to 220 U/mL in the reactor, which was 5.5‐fold more than under comparable conditions in a chemostat.