bluuebunny/crossref_metadata_2025 huggingface dataset:
The construction and operation of a low‐cost poultry waste digester
Authors: Steinsberger Scott C. , Shih Jason C. H.
Published: December 2004

A simple and low‐cost poultry waste digester (PWD) was constructed to treat the waste from 4000 caged laying hens on University Research Unit No. 2 at North Carolina State University. The system was built basically of a plastic lining with insulation, a heating system, a hot‐water tank, and other metering equipment. It was operated at 50°C and pH 7.5–8.0. The initiation of methane production was achieved using the indigenous microflora in the poultry waste. At an optimal loading rate (7.5 kg volatile solids/m3 day), the PWD produced biogas (55% methane) at a rate of 4.0 m3/m3 day. The PWD was biologically stable and able to tolerate temporary overloads and shutdowns. A higher loading rate failed to maintain a high gas production rate and caused drops in methane content and pH value. Under optimal conditions, a positive energy balance was demonstrated with a net surplus of 50.6% of the gross energy. For methane production, the PWD system was proved to be technically feasible. The simple design and inexpensive materials used for this model could significantly reduce the cost of digestion compared to more conventional systems. More studies are needed to determine the durability, the required maintenance of the system, and the most economical method of biogas and solid residue utilization.
Oxidative assimilation treatment of a nitrogen‐deficient toxic waste
Authors: Rozich A. F. , Lowe W. L.
Published: December 2004

Batch growth tests were performed under both replicating and nonproliferating (no nitrogen source in medium) conditions with acclimated heterogenous populations that utilized phenol as a sole source of carbon and energy. It was shown that the acclimated populations could efficiently remove the toxic waste component phenol under nonproliferating conditions by utilizing an oxidative assimilation mechanism. The phenol was assimilated and converted into nonnitrogenous storage products. During the assimilation process, the cells had a tendency to excrete some product (nonsubstrate) chemical oxygen demand (COD). Bench‐scale oxidative assimilation units were operated by sequentially feeding a carbon source (phenol) and nitrogen source (ammonium sulfate) to heterogeneous populations. This demonstrated that, subsequent to the addition of the nitrogen source to the medium, the cells utilized the stored carbon for replication. Four of these units were operated at different phenol COD‐to‐ammonia‐nitrogen ratios of 10:1, 20:1, 40:1, and 50:1. All of these units demonstrated excellent removal of phenol using an oxidative assimilation mechanism. These results suggested the feasibility of utilizing a continuous flow oxidative assimilation process for the treatment of nitrogen‐deficient phenolic wastes. This process would be advantageous over conventional treatment processes in that it would realize a savings in chemical costs (ammonia as nitrogen source) and prevent leakage of excess ammonia from the system.
Study of models of single populations: Development of equations used in microorganism cultures
Authors: Qiwu Cui , Lawson G. J. , Deen Gao
Published: December 2004

This article derives a number of equations which can be used in both continuous and the semicontinuous cultures of microorganism populations in chemostat systems. Using these equations, some phenomena which have been known for many years can be explained reasonably in terms of chemical kinetics, and a number of analytical solutions can be obtained instead of numerical solutions previously published.
An enzyme coimmobilized with a microorganism: The conversion of cellobiose to ethanol using β‐glucosidase and Saccharomyces cerevisiae in calcium alginate gels
Authors: Hahn‐Hägerdal Bärbel
Published: December 2004

The efficiency of β‐glucosidase and Saccharomyces cerevisiae in directly converting cellobiose to ethanol was studied for various combinations of the two catalytic species, both free and immobilized, in order to elucidate the advantages of using a coimmobilized system. The coimmobilized preparation was superior to a combination of separately immobilized biocatalysts. However, in this preparation, one‐half the enzyme activity was lost within a week when incubated at the operational temperature in the absence of substrate. In continuous experiments, an 80% conversion of cellobiose to ethanol was obtained using the coimmobilized preparation, compared to 40% using separately immobilized biocatalysts when applying a dilution rate of 0.1 h−1 in a packedbed reactor. The immobilized biocatalysts showed no decline in productivity during two weeks of continuous operation.
Microbial validation of vent filters
Authors: Robertson John H. , Frieben W. R.
Published: December 2004

The Upjohn Company uses filtration to remove microorganisms and particulates from air and other gases which may come in contact with sterile products. To validate the microbial retentivity of these filters, they were challenged with an aerosol of Bacillus subtilis var niger spores. An aerosol challenge was used because it more closely simulated the use for which these filters were designed. The test apparatus was constructed of autoclavable components using a jet‐type nebulizer and heated air mixing tube. Characterization of the aerosol particle size distribution with a particle size analyzer demonstrated that 80% of the particles had a diameter of × 3.0 times;m and that the particles had a mean mass diameter of 1.9 times;m with a geometric standard deviation of 1.8 times;m. Studies conducted with aerosols of Bacillus subtilis var niger spores demonstrated that the test apparatus could recover ca. 50% of the spores that were aerosolized. Hydrophobic filters from various manufactures were challenged with an aerosol of at least 108 spores of Bacillus subtilis. All filters tested could retain at least 109 spores when physical integrity of the filter was verfield.
Electrochemical and enzymatic activity of flavin adenine dinucleotide and glucose oxidase immobilized by adsorption on carbon
Authors: Miyawaki Osato , Wingard Lemuel B.
Published: December 2004

Flavin adenine dinucleotide (FAD) and glucose oxidase were adsorbed on medium porosity spectroscopic graphite (SG) and on low porosity glassy carbon (GC) with retention of electrochemical activity, as measured by cyclic and differential pulse voltammetry. Adsorption on the SG was very strong, while that on GC was much weaker. Enzyme activity could be partially restored by the addition of the apoenzyme of glucose oxidase to the SG‐adsorbed FAD preparation. The holoenzyme of glucose oxidase also was adsorbed on SG with retention of enzyme activity. The mechanism for the reconstitution of active enzyme from adsorbed FAD and soluble apoenzyme is not clear. The data suggest that the reconstituted enzyme stays adsorbed to the SG, but it is not clear whether the FAD or protein portions (or both) are adsorbed after reconstitution. The data also indicate that substrate mass transfer resistance may be important with the reconstituted–adsorbed enzyme.
Genetically structured models for lac promoter–operator function in the chromosome and in multicopy plasmids: Lac promoter function
Authors: Lee Sun Bok , Bailey James E.
Published: December 2004

A mathematical model based on molecular mechanisms for regulation of the lactose (lac) operon in Escherichia coli has been extended and applied to investigate the lac promoter function in the chromosome and in multicopy plasmids. The model simulates the influence of certain host cell mutations and also mutations in the lac promoter sequence in the chromosome in reasonable agreement with previous experimental measurements. The effect of the plasmid copy number and the cloning vector size on the promoter function of a cloned lac regulatory sequence in multicopy plasmids has also been examined. Model results indicate that the efficiency of the cloned lac promoter function is significantly decreased as the number of promoters per cloning vector and size of the vector are increased. The simulation results predict a maximum in the cloned gene transcription rate with respect to the plasmid copy number.
Two‐phase anaerobic fermentation of liquid swine waste to methane
Authors: Cseh Tibor , Czakó Lajos , Czakó Jenö , Tengerdy Robert P.
Published: December 2004

Two‐phase anaerobic digestion of liquid swine manure has been developed with options for single‐cell protein (SCP) or methane production. In the acidogenic phase at two to four days retention time, and 2.5–7.0% dry matter (DM) concentration, 8–46% of the volatile solids was solubilized. Maximum reactor capacity was 3.86 g/L at 7.0% DM concentration, but optimal operation was achieved at 4.5% DM concentration at four days retention time. The second methanogenic phase was operated continuously and had a maximum specific methane production rate of 0.70 L/L day at 12 days retention time. With recirculation, the rate was 1.16 L/L day at 8.5 days retention time with 52.7% conversion of organic matter. Maximum digestibility was 66% of the lignin free organic matter.
Biological denitrification in a fluidized bed
Authors: Narjari N. K. , Khilar Kartick C. , Mahajan S. P.
Published: December 2004

A fluidized bed biofilm reactor using sand as the carrier particle was employed to study the effects of superficial velocity on the removal of nitrates as well as on the growth of the biofilm. Velocity was found to affect significantly both nitrate removal and biofilm growth. An analysis based on heterogenous catalysis was used to describe the denitrification process. There is good agreement between analysis and experimental measurements for startup and steady‐state operating conditions.
Kinetics of enzymatic starch liquefaction: Simulation of the high‐molecular‐weight product distribution
Authors: Rollings James E. , Thompson Robert W.
Published: December 2004

Enzymatic corn starch liquefaction with α‐amylase was carried out. Molecular weight distributions of the resulting hydrolysates are presented using aqueous size exclusion chromatographic techniques. It is demonstrated that despite the fact that the enzyme employed reacts in a random endoacting manner, the product distributions are nonrandom. The results are explained in part by a multimerization process whereby the polymeric substrate molecules preferentially associate, forming intermolecular aggregates. These aggregates are either a consequence of the manner in which the material is deposited into the native granular structure of starch or due to intrinsic physical chemical properties of the polysaccharide. In the latter case, the results are shown to correspond to known multimerized amylose, although complete characterization of the polysaccharide is currently not available. The results presented are used to develop a simplified kinetic model of starch liquefaction and shown to simulate the product distributions accurately.
Kinetic study of instability of recombinant plasmid pPLc23trpAl in E. coli using two‐stage continuous culture system
Authors: Siegel R. , Ryu Dewey D. Y.
Published: December 2004

Derepression of the phage λ pL promoter on recombinant plasmid pPLc 23‐trpAl caused a rapid increase of plasmid free segregants in the population. In continuous culture, increased production of trpA protein follwing derepression was accompanied by a continuous deceleration of specific growth rate. In the repressed condition, plasmid loss per generation in continuous culture decreased as dilution rate increased from 0.06 to 1.08 h−1. Over this range, the concentration of plasmid DNA within the cell decreased eightfold corresponding to a decrease in plasmid number from 74 to 32 molecules/cell. The use of a two‐stage continuous culture system coupled with a temperature sensitive expression system allows a high trpA productivity from the derepressed plasmid for more than 48 h and also offers a possibility of minimizing the instability problem of high expression recombinants. Such a system also permits the critical study of the effects of fermentation and other regulatory parameters on expression under better controlled conditions than is possible in a batch culture or single‐stage continous culture.
Isolation and partial characterization of a mutant of Penicillium funiculosum for the saccharification of straw
Authors: Hoffman R. M. , Wood T. M.
Published: December 2004

Clearing of agar plates containing ball‐milled, delignified straw has been used for screening mutants of Penicillium funiculosum IMI 87160 iii. The effects of glycerol and a number of sugars on the clearing were investigated for selecting derepressed mutants. The β‐glucosidase synthesis by one such mutant, C22c, in shake flasks containing straw was not repressed by 5% glycerol, whereas activities on filter paper, CM‐cellulose, and p‐nitrophenyl‐β‐xylosidase were only partially derepressed; xylanase was extensively derepressed. The evidence for separate control of the enzymes involved in the solubilization of straw is discussed.
Hydroxylation of biphenyl by Aspergillus parasiticus: Approaches to yield improvment in fermenter cultures
Authors: Cox John C. , Golbeck John H.
Published: December 2004

We carried out experiments designed to increase the rate of production of 4,4′‐dihydroxybiphenyl (biphenol) from biphenyl by Aspergillus parasiticus. We show that 0.5 mg/ml biphenyl, the substrate for the reaction, significantly inhibits growth of the organism and that at 0.04 mg/ml, 2‐hydroxybiphenyl or 4‐hydroxybiphenyl (an intermediate of the reaction) strongly inhibit oxygen uptake, probably by inhibition of mitochondrial electron transport. Both factors may contribute to the low hydroxylation rates observed previously [J. H. Golbeck and J. C. Cox, Biotechnol. Bioeng., 26, 434 (1984)]. We therefore adapted the organism to the presence of 0.08 mg/ml 2‐ and 4‐hydroxybiphenyl in the growth medium and found that cultures of adapted strains hydroxylated biphenyl at rates ca. three‐fold faster than control cultures. Once the fungal mycelia were grown, they could be recycled at least twice into fresh fermentation broth. Recycled organisms were capable of hydroxylating biphenyl more rapidly than cells in the primary fermentation culture and there was no lag period between introduction of biphenyl and the onset of hydroxylation. Cell recycle thus results in a considerable saving in carbon costs and fermentation time.
Effect of hydrogen peroxide pretreatment on the structural features and the enzymatic hydrolysis of rice straw
Authors: Wei Chia‐Jenn , Cheng Chung‐Yueh
Published: December 2004

Assessment was made to evaluate the effect of hydrogen peroxide pretreatment on the change of the structural features and the enzymatic hydrolysis of rice straw. Changes in the lignin content, weight loss, accessibility for Cadoxen, water holding capacity, and crystallinity of straw were measured during pretreatment to express the modification of the lignocellulosic structure of straw. The rates and the extents of enzymatic hydrolysis, cellulase adsorption, and cellobiose accumulation in the initial stage of hydrolysis were determined to study the pretreatment effect on hydrolysis. Pretreatment at 60°C for 5 h in a solution with 1% (w/w) H2O2 and NaOH resulted in 60% delignification, 40% weight loss, a fivefold increase in the accessibility for Cadoxen, an one times increase in the water‐holding capacity, and only a slight decrease in crystallinity as compared with that of the untreated straw. Improvement on the pretreatment effect could be made by increasing the initial alkalinity and the pretreatment temperature of hydrogen peroxide solution. A saturated improvement on the structural features was found when the weight ratio of hydrogen peroxide to straw was above 0.25 g H2O2/g straw in an alkaline H2O2 solution with 1% (w/w) NaOH at 32°C. The initial rates and extents of hydrolysis, cellulase adsorption, and cellobiose accumulation in hydrolysis were enhanced in accordance with the improved structural features of straw pretreated. A four times increase in the extent of the enzymatic hydrolysis of straw for 24 h was attributed to the alkaline hydrogen peroxide pretreatment.
Cellulase production by a solid state culture system
Authors: Kim Jung Hoe , Hosobuchi Masahiko , Kishimoto Michimasa , Seki Tatsuji , Yoshida Toshiomi , Taguchi Hisaharu , Ryu Dewey D. Y.
Published: December 2004

Production of cellulase using solid culture systems of Trichoderma reesei QM9414 and Sporotrichum cellulophilum on wheat bran was studied. By using moisture‐controlled solid culture equipment, the effect of water content of wheat bran on cell growth and cellulase production was investigated. Cellular biomass grown on solid substrate was estimated by measuring oxygen consumption rate and glucosamine content of the cells. These parameters were shown to have a good linear correlation with the specific growth rate. This reliable method of estimating the cell growth rate enabled us to simulate the enzyme production in a solid culture system by means of multiple linear regression analysis which takes into account of the water content, cell mass, and the oxygen consumption rate as variables. The cell growth and cellulase production were maximized at different water content of the medium. A high water content, 57% for T. reesei and 70% for S. cellulophilum, favored mycelial growth, while the maximum cellulase activity was obtained at a lower water content such as 50% for both fungi. It was observed that cellulase production by T. reesei depended on the culture conditions that support the optimal growth rate for the maximum enzyme production.
Serial propagation of mammalian cells on microcarriers
Authors: Hu Wei‐Shou , Giard Donald J. , Wang Daniel I. C.
Published: December 2004

For the large‐scale operation of microcarrier culture to be successful, a technically feasible method for sequential inoculation is essential. Using human foreskin fibroblasts, FS‐4, we have achieved this by detaching cells viably from microcarriers employing a selection pH trypsinization technique. Cells thus detached are able to reattach to microcarriers and grow normally after subsequent reinoculation into new cultures. However, after reinoculation cells attach to new microcarriers at a higher rate than to used microcarriers on which cells have previously grown. The effect of this differential cell attachment was analyzed and overcome by employing a low inoculum concentration. FS‐4 cells could thus be serially propagated on microcarriers and subsequently used for β‐interferon production. This technique has also been applied to the cultivation of a monkey kidney cell line, Vero. We have also shown that Vero cells directly inoculated from a seed microcarrier culture could be used for virus production.
Bacterial adsorption to smooth surfaces: Rate, extent, and spatial pattern
Authors: Nelson C. H. , Robinson J. A. , Characklis W. G.
Published: December 2004

The influence of bulk‐water bacterial cell concentration and specific growth rate history on bacterial adsorption rates to surfaces was investigated using response surface analysis. A pure culture of Pseudomonas sp. 224S was grown in a chemostat and pumped into a continuous flow reactor where the bacteria were exposed to clean, glass surfaces under turbulent flow conditions for a period of six hours. Adsorption rate decreased approximately linearly with increasing specific growth rate history. Glass surfaces became saturated with 224S at ca. 0.1% coverage and the resulting spatial pattern of the adsorbed cells deviated from random in the direction of uniformity.
Use of the UASB reactor for the anaerobic treatment of stillage from sugar cane molasses
Authors: Sánchez Riera F. , Córdoba P. , Siñeriz F.
Published: December 2004

The feasibility of applying the UASB concept for the anaerobic treatment of stillage of distilleries in the sugar producing area of Argentina was subject to study. Results obtained in a 100‐L UASB reactor treating stillages with COD values between 35 and 100 g COD/L are presented. Loading rates of up to 24 g COD/L/day were applied with an average COD removal of 75% and a biogas production of more than 9 L/L/day, with an average methane content of 58%. The settling velocity distribution of sludge particles would indicate a good formation of biomass pellets. System interruptions of months without feed and at ambient temperature (20–24°C) were well tolerated.
Analysis of protein and cell volume distribution in glucose‐limited continuous cultures of budding yeast
Authors: Ranzi Bianca Maria , Compagno Concetta , Martegani Enzo
Published: December 2004

Method of flow cytometric analysis have recently been developed that make it possible to obtain segregated data on a single cell basis. In particular, it has been previously demonstrated that protein distributions obtained by flow cytometry give information about the law of growth of the cell population and the law of growth of the single cell; thus these distribution show how the microbial population is actually growing at the moment of the analysis and may yield more accurate and predictive information. We have extended the analysis of protein distribution and cell volume distribution to continuous cultures of Saccharomyces cerevisiae growing in a glucose‐limited chemostat. We have found that: (1) to each dilution rate corresponds a given protein and volume distribution that does not change with time in steady state cultures; (2) there is a good proportionality between the average cell volume and the average protein content; (3) the protein distribution obtained can be easily analyzed with the model of growth of yeast previously developed in our laboratory; (4) the analysis of perturbed states shows that both protein distribution and volume distribution change very quickly; thus they are very sensitive parameters and can be used for monitoring and controlling industrial fermentation.
Application of immobilized heparins for isolation of human antithrombin III
Authors: Mitra G. , Hall E. , Mitra I.
Published: December 2004

Immobilized heparins were prepared by six different methods, and these were utilized for affinity purification of human antithrombin III (AT‐III). Affinity support capacities (mg AT‐III/g support) were strongly influenced by immobilized active heparin concentrations. In the temperature range 5–37°C, colder temperatures favored affinity adsorption of AT‐III as well as nonspecific interactions of all proteins. For representative human‐plasma‐derived feed solutions the selectivity for AT‐III on the affinity support was dependent on relative concentrations of non‐AT‐III proteins as well as the specific mode of adsorption and elution (batch/continuous).
Coupling of concanavalin A to cellulose hollow fibers for use in glucose affinity sensor
Authors: Srinivasan Keeran R. , Mansouri Sohrab , Schultz Jerome S.
Published: December 2004

This article describes a method for the chemical immobilization of concanavalin A (Con A) on the inside wall of a single hollow cellulose fiber for use in glucose affinity sensor. Periodate oxidation of cellulose fiber followed by a spacer for Con A attachment was deemed to be the most optimal procedure for achieving the highest sensitivity of the sensor without compromising its physical integrity. The effects of variables like the duration of periodate oxidation and its concentration and pH of the spacer coupling step and its duration have been examined. The mechanical strength of the hollow fiber as well as its permeability to the analyte (glucose) have been evaluated prior to and after Con A coupling process.

It has been demonstrated that Con A bound hollow fiber prepared according to the procedure outlined here can be successfully used to construct glucose affinity sensor for operation in the physiological range of glucose concentrations.
Use of lipid solvents for viral inactivation in factor VIII concentrates
Authors: Mitra G. , Wong M.
Published: December 2004

Model virus inactivation studies with lipid solvents were carried our in antihemophilic factor concentrates. The procoagulant activity obtained was ≥80% recovery with 20% amyl acetate–0.1% deoxycholate. A concurrent reduction of four logs of virus titer was obtained for model viruses provided the viral mass contained significant amounts (≥20%) of lipid. From this preliminary study it appears that further investigations in animal models may be warranted to demonstrate the inactivation of hepatitis B virus, non‐A–non‐B virus, and AIDS virus with 20% amyl acetate–0.1% deoxycholate in antihemophilic factor concentrates.
Rheometry of fermentation liquids
Authors: Kemblowski Z. , Kristiansen B.
Published: December 2004

This article is concerned with the measurements of rheological properties of nonhomogeneous fermentation liquids. In order to determine the flow curves of such liquids, an impeller measuring system of own design was used, and the method of calibration of the system is presented. The experimental verification was carried out using samples of fermentation broth of Aureobasidium pullulans and it has been shown that the applied measuring technique gives internally consistent results. The sensitivity of the technique proves its applicability for monitoring and control purposes in fermentation technology.
Growth kinetics of Dioscorea deltoidea and Catharanthus roseus in batch culture
Authors: Drapeau D. , Blanch H. W. , Wilke C. R.
Published: December 2004

Sugar‐limited batch growth of Dioscorea deltoidea and Catharanthus roseus plant cell cultures was studied in a 14‐L stirred tank fermentor. With dissolved oxygen concentration monitored and maintained at nonlimiting levels, growth rates and ratios of dry weight to fresh weight were found to be strongly influenced by sugar concentration. Linear relationships between respiration rate and growth rate were observed, and respiration rate was found to drop to a maintenance level after sugar had been fully depleted from the medium. Diosgenin biosynthesis by D. deltoidea was shown to be independent of growth rate. Ajmalicine biosynthesis in C. roseus was negligible during sugar‐limited growth but was induced by inoculation into an 80‐g/L glucose solution.
Biotreatment of s‐triazine‐containing wastewater in a fluidized bed reactor
Authors: Hogrefe W. , Grossenbacher H. , Cook A. M. , Hütter R.
Published: December 2004

Mixed cultures of microorganisms immobilized on sand were used to degrade s‐triazine‐containing industrial wastewater in a fluidized bed reactor. Immobilized cell concentrations of up to 18 g/L volatile suspended solids could be achieved with the s‐triazines as sole nitrogen source for growth and carbon sources added at a CN ratio of about 12. Maximal removal efficiencies of 80% of the s‐triazines could be maintained only if (a) the bio‐film thickness was limited to avoid oxygen deficiency and (b) the carbon source and complete wastewater (⩽50% v/v in the feed) were supplied continuously at a mean hydraulic residence time of ≥20–25 h.
Kinetics and mechanism of dissimilative Fe(III) reduction by Pseudomonas sp. 200
Authors: Arnold Robert G. , Olson Terese M. , Hoffmann Michael R.
Published: December 2004

The kinetics and mechanism of Fe(III) reduction to Fe(II) were studied in pure batch cultures of Pseudomonas sp. 200. The rate of iron reduction has been mechanistically related to aqueous phase iron speciation. In the absence of microbial activity the iron reduction rate was negligible. Initial rates of microbial iron reduction were accelerated more than 20‐fold by the addition of equimolar quantities of nitrilotriacetic acid (NTA) to media initially containing 1.86 × 10−3M total Fe(III). Numerical techniques were utilized to quantify relationships between the observed rate of Fe(II) production and the calculated (equilibrium) aqueous phase speciation. These results indicate that soluble ferric iron species are not equivalent in terms of their susceptibility to bacterial (dissimilative) iron reduction. The concentration of Fe(NTA)(OH) correlated strongly with observed iron reduction rates. Ferrous iron species appeared to inhibit the reduction process.
Phosphorylation of yeast protein: Reduction of ribonucleic acid and isolation of yeast protein concentrate
Authors: Huang Y.‐T. , Kinsella J. E.
Published: December 2004

Yeast nucleoproteins were chemically phosphorylated with phosphorus oxychloride (POCL3). Studies using 31P nuclear magnetic resonance (NMR) spectroscopy, stability to pH and lysine estimation all indicated that the ϵ‐amino group of lysine was the principal functional group phosphorylated. Phosphorylation of ca. 30% of the lysine residues resulted in removal of more than 85% of contaminant ribonucleic acid from protein precipitated at pH 4.2. Phosphorylation did not alter the amino acid composition of yeast proteins and was reversible under acidic conditions. Based on the data, a method for the preparation of phosphorylated yeast protein with low levels of nucleic acid is proposed.
Modeling active mass in aerobic sludge digestion
Authors: Droste R. L. , Sanchez W. A.
Published: December 2004

Aerobic digestion of waste‐activated sludge was carried out in lab‐scale reactors for both batch and semicontinuous flow patterns. The reactors were monitored at three different temperatures: 10, 20, and 30°C. During the course of digestion, significant solubilization of volatile suspended solids was observed, and its effect on the magnitude of kinetic coefficients was examined. Differences in metabolic activity and sludge stabilization were found between batch and semicontinuous flow patterns. An Arrhenius‐type relationship was not found to apply to rate constants for the semicontinuous reactors.
Anaerobic calorimetry of Zymomonas mobilis using a heat‐flux sensor
Authors: Silman Robert W.
Published: December 2004

A relatively simple and inexpensive anaerobic calorimeter was designed and evaluated by using a Hy‐Cal Engineering BI‐7 bidirectional heat‐flux sensor to measure heat output from magnetically stirred I‐L flask fermentations. The production of ethanol and cumulative heat output by Zymomonas mobilis were both linearly proportional to glucose concentrations up to 160 g/L.
Mode of action and properties of xylanase and β‐Xylosidase from Neurospora crassa
Authors: Deshpande Vasanti , Lachke Anil , Mishra Chittra , Keskar Sulbha , Rao Mala
Published: December 2004

Extracellular β‐xylosidase (1,4‐β‐D‐xylan xylohydrolase, EC 3.2.1.37) from culture filtrates of Neurospora crassa was purified to homogeneity by preparative isoelectric focusing followed by gel electrophoresis. The molecular weight of the purified xylosidase was 83,000 D and the Km on p‐nitrophenyl‐β‐D‐xyloside was 0.047mM. The homogeneous xylanase (1,4‐β‐D‐xylan xylanohydrolase, EC 3.2.1.8) and β‐xylosidase showed differences in their mode of action towards xylooligosaccharides. The degree of hydrolysis of D‐xylan by xylanase of N. crassa was 18%. Supplementation of β‐xylosidase from the same organism resulted in 48% hydrolysis. The synergistic effect was more pronounced, with the hydrolysis of 68%, when a homogeneous preparation of β‐xylosidase from Sclerotium rolfsii was added to the saccharification system.
The kinetics of growth of Proteus vuigaris in nicotinic acid‐limited cultures
Authors: Tseng Murray M‐C. , Phillips Colin R.
Published: December 2004

Proteus vulgaris is shown to take up nicotinic acid in the early stage of growth in amounts greater than needed for growth. The time variation of the specific nicotinic acid content of the cells, calculated by dividing the amount of nicotinic acid taken up from the liquid medium by the mass of cells present at that time, is interpreted to define two parameters, the maximum specific nicotinic acid content, f1, and the minimum content required for growth, f2 The difference, E, between these parameters is the specific nicotinic acid content capable of supporting growth for three doublings after depletion of nicotinic acid from the medium. A kinetic model for the system is developed based upon two stages of growth, a stage in which the cells accumulate from the medium their maximum nicotinic acid content, and a stage in the nicotinic acid‐depleted medium in which cell growth occurs at the expense of the cell‐bound nicotinic acid.
Kinetics of alcohol fermentations carried out in rotating biological surface reactors
Authors: Converti Attilio , Del Borghi Marco , Zilli Mario , Ferraiolo Giuseppe
Published: December 2004

This article aims at deriving kinetic models for the RBS reactor operating with and without cell porous support. Since derivation of the kinetic equations from the Monod model is very complex, an empirical derivation from experimental data of continuous alcohol fermentations is used in this work.
Improvement in separation characteristics of protein precipitates by acoustic conditioning
Authors: Hoare M. , Titchener N. J. , Foster P. R.
Published: December 2004

The effect of acoustic conditioning on the particle size distribution of isoelectric and calcium‐ion‐precipitated soya protein has been examined in low‐residence‐time chambers. In a previous study a beat frequency of 5 Hz obtained using a dual‐source system of opposing vibrators was determined as giving optimal improvement in particle‐settling characteristics for isoelectric soya protein precipitate. In this study the effect of amplitude of vibration, a measure of acoustic power input, and residence time of acoustic conditioning has been examined.

Acoustic power input changed the flow pattern in the conditioning chamber from laminar streamline flow to a well‐mixed, turbulent pattern. Such a mixing effect promoted the rapid aggregation of fine particles, a process that was modeled on the basis of orthokinetically controlled collisions. The rate of removal of fine particles due to acoustic conditioning was shown to be proportional to a mixing effect that was releated to the acoustic power dissipated per unit volume.

The consequences of fine‐particle aggregation on the centrifugal recovery of the precipitate are discussed.
Pretreatment of lignocellulosic materials with hydrogen peroxide in presence of manganese compounds
Authors: Takagi M.
Published: December 2004

Pretreatment of lignocellulosic materials such as newspaper, rice straw, pulp waste, and municipal solid waste with hydrogen peroxide in the presence of manganese compounds greatly enhances their susceptibility to enzymatic saccharification. This pretreatment can be achieved using rather mild conditions with only a minimal decrease in the recovery and little change in composition. Manganese salts in this hydrogen peroxide pretreatment works effectively in particular when the concentration of hydrogen peroxide is relatively low. The susceptibility of hydrogen‐peroxide‐pretreated substrate to enzymatic saccharification increases with increasing the molar ratio of manganes to hydrogen peroxide up to 1 : 100.
Effect of growth rate and expression level on plasmid stability in Saccharomyces cerevisiae
Authors: Parker C. , DiBiasio D.
Published: December 2004

An auxotrophic mutant of Saccharomyces cerevisiae, containing a recombinant 2‐μ‐based plasmid, was grown in selective media in continuous culture. The plasmid retained the ability to synthesize acid phosphatase as product, which was deleted from the host. Plasmid loss was followed at various dilution rates, and the level of plasmid expression was controlled by changing the β‐glycero/inorganic phosphate ratio.

Some interesting trends were observed. As the level of plasmid expression was raised, the stability dropped markedly. Since acid phosphatase expression is regulated at the level of transcription, it is possible that increased transcription interfered with plasmid replication, hindered segregation, or overburdened the cell's DNA repair capability. It was also observed that plasmid stability was substantially increased at high growth rates. At dilution rates of 0.3 and 0.37 h−1, feeding only inorganic phosphate, the plasmid was completely stable.
Steroid conversions by Flavobacterium dehydrogenans in two‐liquid‐phase systems
Authors: Boeren Sjef , Laane Colja
Published: December 2004

The production of 4‐androstene‐3, 17‐dione by Flavobacterium dehydrogenans from androstenolone–acetate in octane/culture (v/v = 1:1) two‐liquid phase systems was compared with the conversion rate in a Tween‐containing medium commonly used in industry, and in a culture where no organic solvent or detergent was added. Variation of the cell density of the cultures at the moment of steroid, Tween, and/or organic solvent addition showed that the highest conversion rate in the three systems was reached with cells which were in the late exponential growth stage. The rate of 4‐androstene‐3, 17‐dione production at the optimal cell density in the two‐liquid‐phase system and Tween medium were ca. 6 and 1½ times as high, respectively, as in the aqueous medium without addition. The beneficial effect of octane on the rate of steroid conversion during growth could be explained by viability changes as measured by a new method to determine viability. Furthermore, our results show that a very high degree of conversion can be reached in the two‐liquid‐phase system [more than 98% (w/w)] which cannot be obtained in an aqueous medium. An easy way to recover the product in high purity is proposed.
Kinetics of milk coagulation: III. Mathematical modeling of the kinetics of curd formation following enzymatic hydrolysis of κ‐casein—parameter estimation
Authors: Carlson Alfred , Hill Charles G. , Olson Norman F.
Published: December 2004

A step function model of milk micelle agglomeration is proposed to explain the observed kinetics of milk clotting following rennet addition. The model ties together the primary and secondary phases of coagulation. The basis of the model is that no micelle flocculation takes place until ca. 75% of the κ‐casein in the milk is hydrolyzed, at which time flocculation occurs rapidly and the rate limiting step for the clotting process shifts to the κ‐casein hydrolysis reaction. Using such a model, it is possible to explain the clotting kinetics for both rapidly denaturing enzymes and stable enzyme systems. The average rate of the flocculation reaction can be obtained from clotting time‐versus‐reciprocal‐enzyme‐concentration data by extrapolating the data to infinite enzyme concentration. The critical conversion required for imminent flocculation can be found by extrapolating the enzyme concentration to zero. This approach indicates that the critical conversion necessary for gelation is temperature dependent changing from a limiting value of essentially 100% hydrolysis at temperatures below 15°C to only 60% conversion at temperatures above 30°C.
Preparation of various glucose esters via lipase‐catalyzed hydrolysis of glucose pentaacetate
Authors: Shaw Jei‐Fu , Klibanov Alexander M.
Published: December 2004

β‐D(+)‐Glucose pentaacetate was hydrolyzed both chemically and enzymatically. In contrast to the alkaline hydrolysis, esterase‐catalyzed deacetylations afforded significant accumulation of intermediate glucose esters at different degrees of substrate conversion. Aspergillus niger lipase, the most suitable of the four enzymes tested, was used for preparative hydrolysis of glucose pentaacetate. As a result, gram quantities of pure glucose‐2,3,4,6‐tetraacetate, glucose triacetate (a mixture of two positional isomers, 2,4,6‐ and 3,4,6‐), and glucose‐4,6‐diacetate were prepared.
Aerobic oxidation of hydrogen sulfide by Thiobacillus denitrificans
Authors: Subletta Kerry L.
Published: December 2004

It has been demonstrated that Thiobacillus denitrificans may be readily cultured aerobically in batch and continuous flow reactors on H2S(g) under sulfide limiting conditions. Under these conditions sulfide concentrations in the culture medium were less than 1μM resulting in very low concentrations of H2S in the reactor outlet gas. Biomass yield under aerobic conditions was much lower than previously reported for anaerobic conditions, presumably because of oxygen inhibition of growth. However, biomass yield was not affected by steady state oxygen concentration in the range of 45μM–150μM. Biomass yield was also observed to be essentially independent of specific growth rate in the range of 0.030–0.053 h−1. Indicators of reactor upset were determined and recovery from upset conditions demonstrated. Maximum loading of the biomass for H2S oxidation under aerobic conditions was observed to be 15.1–20.9 mmol/h/g biomass which is much higher than previously reported for aerobic conditions. Other aspects of the stoichiometry of aerobic H2S oxidation are also reported.
Optimization of steam explosion as a method for increasing susceptibility of sugarcane bagasse to enzymatic saccharification
Authors: Morjanoff P. J. , Gray P. P.
Published: December 2004

The technique of autohydrolysis steam explosion was examined as a means for pretreatment of sugarcane bagasse. Treatment conditions were optimized so that following enzymatic hydrolysis, pretreated bagasse would give 65.1 g sugars/100 g starting bagasse. Released sugars comprised 38.9 g glucose, 0.6 g cellobiose, 22.1 g xylose, and 3.5 g arabinose, and were equivalent to 83% of the anhydroglucan and 84% of the anhydroxylan content of untreated bagasse. Optimum conditions were treatment for 30 S with saturated steam at 220°C with a water‐to‐solids ratio of 2 and the addition of 1 g H2SO4/100 g dry bagasse. Bagasse treated in this manner was not inhibitory to fermentation by Saccharomyces uvarum except at low inoculum levels when fermentation time was extended by up to 24 h. Pretreated saccharified bagasse was inhibitory to Pachysolen tannophilus and this was attributed to the formation of acetate from the hydrolysis of acetyl groups present in hemicellulose. The major advantage of the pretreatment is the achievement of high total sugar yield with moderate enzyme requirement and only minor losses due to sugar decomposition.
Kinetics of growth and phosphate uptake in pure culture studies of Acinetobacter species
Authors: Hao Oliver J. , Chang C. H.
Published: December 2004

Acinetobacter has been found to be the major species responsible for mediating biological phosphate removal. The growth kinetics and phosphate uptake were investigated for an isolated Acinetobacter strain growing in a defined medium. The phosphate uptake is dependent on growth rate, temperature, and pH. Polyphosphate granules occurred in a balanced growth stage. The maximum phosphorus content in cells was 4.8% at the dilution rate of 12 day−1. The specific phosphate uptake rate was found to be a quadratic polynomial function of the dilution rate. Increased calcium (up to 36 mg/L) and magnesium (up to 15 mg/L), and the addition of yeast extract (100 mg/L), primary effluent (20%), and fluoride (10 mg/L) did not affect phosphate uptake. Anaerobic conditioning (N2 stripping), low pH (CO2 stripping), and addition of sodium acetate under anaerobic conditions failed to stimulate immediate phosphate release. Nevertheless, After 21–24 h, the phosphate release was ca. 3, 5, and 15 mg P/g cell, respectively, for N2 purging, the addition of acetate, and CO2 purging. For two‐stage completely stirred reactor operation, there was negligible phosphate overplus at the second reactor when phosphate was added, when the first reactor was subjected to phosphate limitation. When both phosphate and carbon limited the growth in the first reactor, there was slight phosphate accumulation under endogenous respiration conditions in the second reactor.
Kinetics of ethanol production during the reactor feeding phase in constant feb‐batch fermentation of molasses
Authors: Borzani Walter
Published: December 2004

During the fermentor feeding phase in constant fed‐batch ethanol fermentation of molasses, the ethanol production rates are constant and are correlated to the sugar feeding rates by a Monod‐like equation. The parameters of this Monod‐like correlation depend on the sugars concentration of the feeding mash. A model is proposed to explain the constancy of the ethanol production rate experimentally observed. From the Monod‐like correlation it is possible to evaluate the maximum value of the mash feeding rate to be used in order to have a completely fermented medium just at the end of the feeding phase.
Evaluation of true kinetic parameters for reversible immobilized enzyme reactions
Authors: Ishikawa Haruo , Tanaka Takenori , Kurose Katsuo , Hikita Haruo
Published: December 2004

For a reversible one‐substrate reaction system that follows the Haldane reaction mechanism, a new and effective method has been proposed to extract true or intrinsic kinetic parameters of immobilized enzymes from diffusion limited rate data. The method utilizes the effectiveness factors correlated in terms of the general modulus defined by Aris and Bischoff, and a new modulus defined in the present study. It requires a trial‐and‐error calculation, but only a few data points. Furthermore, it provides a saving of materials such as substrates and enzymes, and takes less time for experiments compared to the initial rate methods. The usefulness of the method is demonstrated by determining the kinetic parameters for membrane bound fumarase which catalyzes the reaction of the conversion of fumarate to L‐malate, for which the equilibrium constant is ca. 4.
Regulation of lac operon expression in mixed sugar chemostat cultures
Authors: Ray N. G. , Vieth W. R. , Venkatasubramanian K.
Published: December 2004

Expression of the lactose (lac) operon in the Escherichia coli chromosome has been studied in mixed‐sugar chemostat cultures under steady‐state and transient conditions. A unified model has been formulated which involves regulation of active inducer (lactose) transport, promoter–operator regulated expression of the lac operon, glucose‐mediated inducer exclusion, and catabolite repression. The model of the lac operon control system focuses on the molecular interactions among the regulatory species and the genetic control elements for the initiation of transcription. The role of catabolite modulator factor (CMF) in the regulation of transcription is described. The modeling of glucose‐mediated regulation of intracellular cyclic adenosine monophosphate (cAMP) and inducer exclusion is based on the recently elucidated mechanisms of the involvement of the PTS (phosphoen‐olpyruvate dependent sugar transport system) enzymes, in the presence of glucose, in regulation of adenylate cyclase and non‐PTS sugar transport proteins (i.e. per‐meases). The adequacy of the unified model was verified with experimental data.
Modeling biofilm kinetics for a low‐loaded expanded‐bed anaerobic reactor
Authors: Wang Yi‐Tin , Suidan Makram T. , Rittmann Bruce E.
Published: December 2004

The effect of surface coverage of biomass on biofilm kinetics in an expanded‐bed, granular activated carbon an aerobic reactor was evaluated. Acetate was used as the sole organic carbon source. An assumption of 10% surface coverage of biofilm was examined and compared to 100% coverage. Best estimated values of ka and Ksa did not differ significantly from one case to the other. The confidence region analysis also showed that the biofilm was fully penetrated in the expanded‐bed reactor for the case of 10% coverage, as well as when 100% coverage was assumed. Because the biofilm was fully penetrated, a model having no internal diffusion resistance and using the best estimates of ka and Ksa obtained from the 10 and 100% coverage assumptions was capable of giving good predictions of effluent acetate concentrations for an in dependent experiment having a reduced liquid detention time. Consideration of biofilm surface‐loading criteria demonstrated how the results can be applied to other reactors for the purpose of predicting when the extent of surface coverage and internal diffusion resistance are not significant factors in biofilm modeling.