bluuebunny/crossref_metadata_2025 huggingface dataset:
Fungal treatment of mechanical pulps—its effect on paper properties
Authors: Pilon L. , Barbe M. C. , Desrochers M. , Jurasek L. , Neumann P. J.
Published: December 2004

Refiner mechanical pulp was biologically treated with several higher fungi in order to test their potential for increasing the strength of paper. It was among the white‐rot fungi that the best results were obtained. Polyporus versicolor gave the best overall improvement in handsheet properties with no reduction in tear. The strength improvement is due to attack on lignin and to an increase in fiber flexibility as measured by water retention values and by acidic group content of the treated pulps. The brown‐rot fungi had a detrimental effect on paper properties.
Activated sludge system design for large variations or organic loading
Authors: Vasiliev V. B. , Vavilin V. A.
Published: December 2004

An aeration tank/sedimentation tank system is considered for large variations of organic loading. In this case, it is important to take into account the variability of the characteristics describing the oxidation of activated sludge as well as its sedimentation. The minimum cost of the treatment system is also evaluated.
Sorption of Talaromyces emersonii cellulase on cellulosic substrates
Authors: Moloney Aidan , Coughlan Michael P.
Published: December 2004

The sorption characteristics of the cellulase system of Talaromyces emersonii on various cellulosic substrates were examined. Analysis of reaction mixture supernatants by electrophoresis and enzyme assay showed that all components of the cellulase system were rapidly adsorbed by cellulose and then gradually returned to the liquid phase as the hydrolysis of the substrate progressed. The extent of adsorption in the rapid phase was influenced by pH, temperature, the nature of the substrate, and its concentration.
Isolation and functional characterization of hydrocarbon emulsifying and solubilizing factors produced by a Pseudomonas species
Authors: Reddy P. G. , Singh H. D. , Pathak M. G. , Bhagat S. D. , Baruah J. N.
Published: December 2004

Pseudomonas PG‐1 cultivated on pristane produced in good amount a heat‐stable polymeric substance which showed strong hydrocarbon emulsifying and solubilizing properties. The substance was isolated in crude form and was found to contain 34% protein, 16% carbohydrate, and 40% lipid. The hydrocarbon solubilizing activity of the isolate was strongly inhibited by EDTA but the chelating agent had no effect on the hydrocarbon emulsifying activity. Both activities of the isolate were strongly inhibited by chymotrypsin treatment indicating the importance of the protein moiety for its activity. Hydrocarbon solubilization by the isolate showed a certain degree of specificity to pristane in modest agitation generally used in microbial cultivation, but this specificity was lost by vigorous agitation in a Waring blender. It was proposed that in the first case, solubilization was effected by a solubilizing factor specific to pristane, whereas in the latter case, nonspecific solubilization occurred due to the action of the emulsifying factor. The rate of pristane solubilization by heat‐treated culture broth under the conditions of agitation used in cultivation (rotary shaker, 120 rpm) was found to be ca. 750 mg L−1 h−1 which was much larger than the maximal pristane uptake rate of 170 mg L−1 h−1 observed during microbial growth on the substrate. It was concluded that hydrocarbon solubilization could satisfactorily account for the substrate uptake and growth.
A kinetic model of starch hydrolysis by α‐ and β‐amylase during mashing
Authors: Marc A. , Engasser J. M. , Moll M. , Flayeux R.
Published: December 2004

Kinetics of malt starch hydrolysis by endogeneous α‐ and β‐amylases has been experimentally investigated in laboratory‐, pilot‐ and industrial‐scale reactors. The production rates of glucose, maltose, maltotriose and total extract, and the separate α‐ and β‐amylases deactivation rates are measured at varying mashing temperature and different initial starch concentrations and qualities. Based on the experimental results, a model is proposed that takes into account the initial carbohydrates and enzymes dissolution, the starch gelatinization, the separate hydrolytic action of α‐and β‐amylases on insoluble and soluble starch and dextrins, and the influence of temperature both on enzyme activities and thermal denaturation rate. The model can predict, at the three scales, the final sugars concentrations in the wort for given initial malt concentrations and enzymatic contents, and for a fixed temperature profile during the mashing process.
Characterization of cellobiose fermentations to ethanol by yeasts
Authors: Freer S. N. , Detroy R. W.
Published: December 2004

Twenty‐two different yeasts were screened for their ability to ferment both glucose and cellobiose. The fermentation characteristics of Candida lusitaniae (NRRL Y‐5394) and C. wickerhamii (NRRL Y‐2563) were selected for further study because their initial rate of ethanol production from cellobiose was faster than the other test cultures. C. lusitaniae produced 44 g/L ethanol from 90 g/L cellobiose after 5–7 days. When higher carbohydrate concentrations were employed, fermentation ceased when the ethanol concentration reached 45–60 g/L. C. lusitaniae exhibited barely detectable levels of β‐glucosidase, even though the culture actively fermented cellobiose. C. wickerhamii produced ethanol from cellobiose at a rate equivalent to C. lusitaniae; however, once the ethanol concentration reached 20 g/L, fermentation ceased. Using p‐nitrophenyl‐β‐D‐glucopyranoside (pNPG) as substrate, β‐glucosidase (3–5 U/mL) was detected when C. wickerhamii was grown anaerobically on glucose or cellobiose. About 35% of the β‐glucosidase activity was excreted into the medium. The cell‐associated activity was highest against pNPG and salicin. Approximately 100‐fold less activity was detected with cellobiose as substrate. When empolying these organisms in a simultaneous saccharification‐fermentation of avicel, using Trichoderma reesei cellulase as the saccharifying agent, 10–30% more ethanol was produced by the two yeasts capable of fermenting cellobiose than by the control, Saccharomyces cerevisiae.
Estimation of true growth and product yields in aerobic cultures
Authors: Oner M. D. , Erickson L. E. , Yang S. S.
Published: December 2004

In the microbial production of useful products, it is important to understand the allocation of substrate energy for maintanance, growth, and product formation. Methods are presented to obtain point and 95% confidence interval estimates for the true growth yield parameter, true product yield parameter, and the maintenance parameter. Methods are presented which allow all data to be used simultaneously for those cases where more than the minimum number of measurements are made at each specific growth rate (or dilution rate). Three estimation methods and two forms of the energy allocation equations are investigated. Point estimates are similar for the three methods, but interval estimates are considerably larger for one of the three methods. The results depend on the form of the equations.
Preparative separation of α‐ and β‐naphthols catalyzed by immobilized sulfatase
Authors: Pelsy Gilles , Klibanov Alexander M.
Published: December 2004

It has been found that sulfatase from Helix pomatia hydrolyzes β‐naphthyl sulfate much faster than α‐naphthyl sulfate; e.g., at pH 7.8, while the former is readily hydrolyzed, the latter undergoes no appreciable hydrolysis. Kinetic investigations of both enzymatic and acid hydrolysis of naphthyl sulfates and their analogs indicate that in the enzymatic reaction the difference in reactivities is due to steric hindrances exerted in α‐naphthyl sulfate by the benzene ring adjacent to the one bearing the sulfate group. (In the β‐ester this ring is remote from the site of hydrolysis.) The enzyme was immobilized and employed for the preparative resolution of α‐ and β‐naphthols: a mixture of the isomers was first sulfated with chlorosulfonic acid and then incubated with sulfatase covalently attached to alumina. The β‐naphthol produced was extracted with benzene, followed by acid hydrolysis of α‐naphthyl sulfate in the remaining aqueous solution and extraction of the α‐naphthol formed. Helix pomatia sulfatase also expresses a marked regiospecificity in the hydrolysis of ortho and para substituted phenyl sulfates. Therefore, the enzyme can be used for the preparative separation of naphthols as well as a variety of isomeric phenols.
Structure‐function relationships in immobilized chymotrypsin catalysis
Authors: Clark Douglas S. , Bailey James E.
Published: December 2004

Specific activities and the amounts of active immobilized enzyme were determined for several different preparations of α‐chymotrypsin immobilized on CNBr‐activated Sepharose 4B. Electron paramagnetic resonance (EPR) spectroscopy of free and immobilized enzyme with a spin label coupled to the active site was used to probe the effects of different immobilization conditions on the immobilized enzyme active site configuration. Specific activity of active enzyme decreased and rotational correlation time of the spin label increased with increasing immobilized enzyme loading. Enzyme immobilized using an intermediate six‐carbon spacer arm exhibited greater specific activity and spin label mobility than directly coupled enzyme. The observed activity changes due to immobilization were completely consistent with corresponding active site structure alterations revealed by EPR spectroscopy.
Immobilization of the exo‐maltohexaohydrolase by the irradiation method
Authors: Nakakuki Teruo , Hayashi Toru , Monma Mitsuru , Kawashima Koji , Kainuma Keiji
Published: December 2004

Exomaltohexaohydrolase (E.C.3.2.1.98) was immobilized by radiocopolymerization of some synthetic monomers which were mixed in various combinations. Irradiation was carried out while the mixture of monomers and enzymes was frozen in petroleum ether–dry‐ice bath. Recovery of the immobilized enzyme was 44–75%.

The optimum pH of the enzyme slightly shifted to the acidic side. The pH stability was improved remarkably by immobilization. The enzyme was stable retaining more than 90% of its original activity in the range pH 4–11. The optimum reaction temperature of the enzyme increased about 2°C. Heat stability was also improved by immobilization, and that the enzyme retained about 40% of its original activity after treatment at 75°C for 15 min. The immobilized enzyme was stable to the repeated use of 20 cycles. The Km value of the enzyme for short‐chain amylose was almost the same as that of native enzyme. When soluble starch was used as the substrate, the Km, value of the enzyme was three times as large as that of native enzyme. Effects of various metal ions and inhibitors on the immobilized enzyme were also studied compared to the native enzyme.
Fermentation air filtration upgrading by use of membrane cartridge filters
Authors: Bruno C. F. , Szabo Louis A.
Published: December 2004

The evolution of the use of improved, hydrophobic air filters in industrial plant germinators and fermentors is described, with the improved filters replacing Fiberglas media. The history and problems associated with use of Fiberglas media are described, as are the advantages of the hydrophobic filter.
Anaerobic filters for the treatment of coal gasification wastewater
Authors: Suidan Makram T. , Siekerka Gerald L. , Kao Shu‐Wen , Pfeffer John T.
Published: December 2004

A process train consisting of the following sequence of unit processes, a berl‐saddle‐packed anaerobic filter, an expanded bed, granular activated carbon anaerobic filter, and an activated sludge nitrification system was evaluated for the treatment of a synthetically prepared coal gasification wastewater. The first‐stage anaerobic filter resulted in very little removal of organic matter and no methane production. Excellent reduction in organic matter occurred in the granular activated carbon anaerobic filter. The removal mechanism was initially adsorptive and near the end of the study, removal of organic matter was primarily through conversion to methane gas. It is felt that the success of the activated carbon anaerobic filter was due to the ability of the activated carbon to sequester some components of the wastewater that were toxic to the mixed culture of anaerobic microorganisms. The activated sludge nitrification system resulted in complete ammonia oxidation and was very efficient in final effluent polishing.
Effects of the inability of suspension‐feeding protozoa to collect all cell sizes of a bacterial population
Authors: Pavlou Stavros , Fredrickson A. G.
Published: December 2004

The effects of the inability of suspension‐feeding protozoa to collect bacteria over the whole range of sizes in the bacterial size distribution were examined by constructing mathematical models based on this assumption. Systems of suspension‐feeding protozoa grown on both growing and nongrowing bacteria were examined in both batch and continuous culture. The models were able to predict three experimental observations common in such systems. Some additional features of the systems which should be useful in interpreting results of experiments with suspension feeding protozoa and in designing new experiments were predicted, also.
Removal of color from kraft mill wastewaters with cultures of white‐rot fungi and with immobilized mycelium of Coriolus versicolor
Authors: Livernoche D. , Jurasek L. , Desrochers M. , Dorica J. , Veliky I. A.
Published: December 2004

Screening fifteen strains of white‐rot fungi for their ability to decolorize combined bleached kraft effluent showed that Coriolus versicolor in liquid culture removed over 60% of the color of the effluent within six days in the presence of sucrose. Treatment of the same effluent with this fungus, immobilized in beads of calcium alginate gel, resulted in 80% decolorization after three days in the presence of sucrose. Caustic extraction E1 effluent was also decolorized by the immobilized fungus. Decolorization was achieved more rapidly at pH 5.0 than at pH 7.0. Recycled beads could remove color efficiently and repeatedly in the presence of air but not under anaerobic conditions.
Chemical and gamma‐ray‐modified bagasse as substrates for bioproduction of cellulases and protein
Authors: Lillehoj E. B. , Han Y. W.
Published: December 2004

Production of enzymes in the cellulolytic complex was determined in culture filtrates of six fungal isolates grown on chemically treated or gamma‐irradiated bagasse. The enzymatic activities of the filtrates were determined by measurement of glucose release from cotton, filter paper, carboxymethylcellulose, cellobiose, and cellobiose octaacetate. Cultures grown on base‐treated and gamma‐irradiated plus acid‐treated bagasse provided culture filtrates with the highest enzymatic activities whereas α‐cellulose, untreated, and acid‐treated bagasse were the poorest substrates for enzyme production. Filtrates of Trichoderma reesei QM 9414 yielded the highest cellulolytic activity in all test media. The largest accumulation of fungal‐derived, extracellular protein was observed in media containing gamma‐irradiated bagasse as the carbon substrate.
A simple algal production system designed to utilize the flashing light effect
Authors: Laws E. A. , Terry K. L. , Wickman J. , Chalup M. S.
Published: December 2004

Arrays of foils similar in design to airplane wings have been placed in an algal culture flume to create systematic mixing. Vortices are produced in the culture due to the pressure differential created as water flows over and under the foils. In a flume having a flow rate of 30 cm/s, the foil arrays produced vortices with rotation rates of ca. 0.5−1.0 Hz. This rotation rate is satisfactory to take advantage of the flashing light effect if the culture is sufficiently dense. Solar energy conversion efficiencies in an experimental culture of P. tricornutum increased 2.2–2.4 fold with the foil arrays in place versus controls with no foil arrays and solar energy conversion efficiencies averaged 3.7% over a three‐month period. Five‐day running means of solar energy conversion efficiencies reached as high as 10% during the three‐month period. The use of foil arrays appears to be an effective and inexpensive way to utilize the flashing light effect in a dense algal culture system.
Productions of cellulase from Pestalotiopsis versicolor
Authors: Rao M. N. A. , Mithal B. M. , Thakur R. N. , Sastry K. S. M.
Published: December 2004

Production of cellulase from Pestalotiopsis versicolor was studied in a shake flask culture. The cellulase system was found to be rich in β‐glucosidase. Kinetic parameters such as pH and temperature have been optimized for the various enzyme components.
Automatic on‐line fermentation headspace gas analysis using a computer‐controlled gas chromatograph
Authors: Comberbach D. Martin , Bu'lock John D.
Published: December 2004

A computer‐controlled headspace gas chromatograph was used to monitor the progress of ethanol production from both aerobic batch and anaerobic continuous fermentations. Using an automatic, electropneumatic sampling system, aliquots of fermentation headspace gas were injected directly onto the column for quantitative ethanol determinations every six minutes. A sample volume of 1 mL permitted liquid ethanol concentrations from 2 to 100 g/L to be measured with better than 3% standard deviation on five repeated injections. Provided fermenter liquid temperature and ionic strength were maintained constant, the signal‐tohyphen;concentration ratio remained linear to 80 g/L ethanol. This quantitative gas chromatographic (GC) method is suitable for accurate, precise analysis of multiple solvent fermentations, and is limited only by the elution rate and separating capacity of the GC column.
Mathematical description of anaerobic treatment of wastewater in upflow reactors
Authors: Van Der Meer R. R. , Heertjes P. M.
Published: December 2004

A quantitative description has been presented of anaerobic treatment in an upflow reactor of dilute wastewater containing lower fatty acids as the main pollutant. It contains as its principal elements mathematical descriptions of the dynamic behavior and the distribution of both the fluid and the anaerobic sludge in the reactor, and a quantification of the kinetics of the anaerobic conversion of the organic waste and of the formation of bacterial products and methane. These elements have been taken together in mass (organic carbon) balances for the substrate, the methane, and the bacterial products, over the two most important reactor parts: the sludge bed and the sludge blanket. In the second part of this article, the description has been used for prediction and determination of the optimum reactor dimensions and process conditions. These optimum values can be used for the design of new reactors and for the establishment of the best suited process operation, which is important for obtaining the best purification results and process reliability at minimum investment and operation costs.
Sodium cyanoborohydride in the immobilization of proteins to glutaraldehyde‐activated aminoalkyl silica
Authors: Miller Arthur W. , Robyt John F.
Published: December 2004

No Absrtact.
Factors effecting cell attachment, spreading, and growth on derivatized microcarriers: II introduction of hydrophobic elements
Authors: Reuveny Shaul , Mizrahi Avshalom , Kotler Moshe , Freeman Amihay
Published: December 2004

In a previous publication, the authors described the establishment of a working system for studing effects of factors involved in the chemical nature of a microcarrier on cell attachment, spreading, and growth. The first part of the rsearch dealt with the influence of the type and amount of the positively charged groups. In the present article, the authors will describe the effect of the introduction of hydrophobic elements onto primary amino derivatized polyacrylamide microcariers. It was found that cell attachement kinetics were gradually enhanced in parallel to a gradual increase in hydrophobicity via elongation of the hydrocarbon side‐chain carrying the primary amino charged group. A threshold effect of the amount of charge required for cell attachment spreading and growth was exhibited on all the tested primary amino derivatized microcarriers. Optimum cell growth was recorded for the butylamine and hexylamine polyacrylamide microcarris. Lowre cell yields were recorded for ethylamine and octylamine derivatives. The location of the introduced hydrophobic element has a profound effect on cell propagation. Introduction of hydrophobicity onto the polymeric backbone of the microcarrier (via copolymerization of hydrophobic comonomer) lead to negative influence on cell attachement and growth yields. Out of the series of derivatized polyacrylamide microcarriers tested, it seems that the hexylamine derivative may be a potential alternative for the commonly used tertiary amine microcariers.
Isoelectric precipitation of soy protein: I. Factors affecting particle size distribution
Authors: Petenate Angela M. , Glatz Charles E.
Published: December 2004

The particle size distribution (PSD) of soyabean protein aggregates obtained by acid precipitation in a continuous stirred reactor was measured with a Coulter Counter model TA II. Effects of changes in the operating variables pH, concentration, mean residence time, power input, and ionic strength were investigated. Power input affects both growth and breakup while pH and ionic strength seem to exert their influence through solubility and aggregate strength. Changes in ζ‐potential can explain most of these observations.
Effect of air supplement on the performance of continuous ethanol fermentation system
Authors: Ryu Dewey D. Y. , Kim Y. J. , Kim J. H.
Published: December 2004

For the purpose of improving ethanol productivity, the effect of air supplement on the performance of continuous ethanol fermentation system was studied. The effect of oxygen supplement on yeast concentration, cell yield, cell viability, extracellular ethanol concentration, ethanol yield, maintenance coefficient, specific rates of glucose assimilation, ethanol production, and ethanol productivity have been evaluated, using a high alcohol tolerant Saccharomyces cerevisiae STV89 strain and employing a continuous fermentor equipped with an accurate air metering system in the flow rate range 0–11 mL air/L/h. It was found that, when a small amount of oxygen up to about 80μ mol oxygen/L/h was supplied, the ethanol productivity was significantly enhanced as compared to the productivity of the culture without any air supplement. It was also found that the oxygen supplement improved cell viability considerably as well as the ethanol tolerance level of yeast. As the air supply rate was increased, from 0 to 11 mL air/L/h while maintaining a constant dilution rate at about 0.06 h−1, the cell concentration increased from 2.3 to 8.2 g/L and the ethanol productivity increased from 1.7 to 4.1 g ethanol/L/h, although the specific ethanol production rate decreased slightly from 0.75 to 0.5 g ethanol/g cell/h. The ethanol yield was slightly improved also with an increase in air supply rate, from about 0.37 to 0.45 ethanol/g glucose. The maintenance coefficient increased by only a small amount with the air supplement. This kind of air supplement technique may very well prove to be of practical importance to a development of a highly productive ethanol fermentation process system especially as a combined system with a high density cell culture technique.
A rapid and simplified procedure for purification of a cellulase from Fusarium lini
Authors: Vaidya Madhavi , Seeta R. , Mishra Chittra , Deshpande Vasanti , Rao Mala
Published: December 2004

An endo‐β‐1,4‐glucanase (EC 3.2.1.4) was obtained in high yields in purified form a culture filtrate of Fusarium lini by an extremely simple method. The method consists of precipitation of the culture filtrate with ammonium sulphate (290 g/L), followed by chromatography of the precipitated fraction on Biogel P‐150. The purification is based on the unusual property of the enzyme being eluted after cytochrome C, even though it molecular weight is 2.8 × 104 (by SDS PAGE). The yield of pure enzyme was 6.8 mg/L culture broth. The homogeneity of the enzyme was established by ultracentrifugation, isoelectric focusing, and electrophoresis in polyacrylamide gels containing SDS. The enzyme was isoelectric at pH 8.3 and contained 2.9% carbohydrate. The Km value for carboxymethyl (CM) cellulose was 11.6 mg/mL. The enzyme showed high viscosity reducing activity towards CM cellulose but very low activity with Walseth cellulose and crystalline celluloses such as Avicel and cotton. The purified enzyme has activity towards xylan. The amino acid analysis showed a predominance of acidic and neutral amino acids and low contents of histidine, arginine, and methionine. One‐half of the cysteine content was 11 residues/mol enzyme, and no free–SH group was detectable.
Diffusion characteristics of substrates in Ca‐alginate gel beads
Authors: Tanaka Hideo , Matsumura Masatoshi , Veliky I. A.
Published: December 2004

The diffusion characteristics of several substrates of varying molecular sizes into and from Ca‐alginate gel beads in well‐stirred solutions were investigated. The values of the diffusion coefficient (D) of substrates such as glucose, L‐tryptophan, and α‐lactoalbumin [with molecular weight (MW) less than 2 × 104] into and from the gel beads agreed with those in the water system. Their substrates could diffuse freely into and from the gel beads without disturbance by the pores in the gel beads. The diffusion of their substrates into and from the gel beads was also not disturbed by increasing the Ca‐alginate concentration in the beads and the CaCl2 concentration used in the gel preparation. In the case of higher molecular weight substances such as albumin (MW = 6.9 × 104), γ‐globulin (MW = 1.54 × 105) and fibrinogen (MW = 3.41 × 105), the diffusion behaviors of the substrates into and from the gel beads were very different. No diffusion of their substrates into the gel beads from solutions was observed, and only albumin was partly absorbed on the surface of the gel beads. The values of D of their substrates from the gel beads into their solutions were smaller than their values in the water system, but all their substrates could diffuse from the gel beads. The diffusion of high molecular weight substrates was limited more strongly by the increase of Ca‐alginate concentration in the gel beads than by the increase of the CaCl2 concentration used in the gel preparation. Using these results, the capacity of Ca‐alginate gel as a matrix of immobilization was discussed.
Effect of dissolved oxygen on nitrogen fixation by A. vinelandii. II. Ionically adsorbed cells
Authors: DiLuccio Robert C. , Kirwan Donald J.
Published: December 2004

Continuous culture studies of Azotobacter vinelandii cells immobilized by ionic adsorption to Cellex E anion exchange resin were conducted under oxygen‐limited conditions for comparison to free‐cell cultures. Immobilization had little effect upon the specific respiration and sucrose consumption rates as compared to free cells. However, maxima in specific nitrogen fixation rate and nitrogenase activity as a function of dissolved oxygen occurred at a C value of approximately 0.005 mM as opposed to 0.02 mM for free cells. Further, in contrast to free‐cell culture, most of the fixed nitrogen appeared in the medium rather than within intact cells. There were strong indications that reproduction of bound cells often resulted in cell lysis accounting for the fixed nitrogen content in solution.
Continuous bacterial coal desulfurization employing Thiobacillus ferrooxidans
Authors: Myerson Allan S. , Kline Paul C.
Published: December 2004

The leaching of pyrite sulfur from coal employing Thiobacillus Ferrooxidans was studied in a continuous stirred tank reactor at a variety of dilution rates (0.02–0.11 h−1) and coal surface areas (0.25–1.0 m2/mL). The bacterial leaching rate was found to increase with increasing coal surface area concentration and increasing dilution rate. The bacterial concentration on the coal surface was related to the bacterial concentration in solution by a irreversible second‐order (of the second kind) kinetic equation. The concentration of bacteria on the coal in all experiments was the concentration at saturation. Step changes in the coal concentration were observed to result in dramatic declines in bacterial concentration in solution. A bacterial mass balance model was employed to calculate the specific growth rate on the solid which was observed to increase with increasing dilution rate.
Immobilized cell cross‐flow reactor
Authors: Chotani G. K. , Constantinides A.
Published: December 2004

A cross‐current flow reactor was operated using sodium alginate gel entrapped yeast cells under growth conditions. Micron‐sized silica, incorporated into the biocatalyst particles (1 mm mean diameter) improved mechanical strength and internal surface adhesion. The process showed decreased productivity and stability at 35°C compared to the normal study done at 30°C. The increased number of cross flows diminish the product inhibition effect. The residence time distribution shows that the cross‐flow bioreactor system can be approximated to either a train of backmixed fermentors in series or a plug flow fermentor with moderate axial dispersion.
Application of immobilized invertase to continuous hydrolysis of concentrated sucrose solutions
Authors: Monsan P. , Combes D.
Published: December 2004

Invertase immobilized onto corn grits was utilized in the hydrolysis of highly concentrated sucrose solutions producting liquid sugar solutions containing glucose and fructose. Comparisons of conversion efficiencies of this immobilized invertase in a continuous stirredtank reactor and a plug‐flow reactor indicated that the plug‐flow reactor has an higher efficiency. Continuous sucrose hydrolysis was then performed in 0.1‐ and 1‐L tubular reactors. This tenforld scaling‐up was achieved without any noticeable loss in efficiency. This process thus was scaled‐up to a 17.6‐L pilot reactor set in a cane sugar refinery. This reactor was fed with highly concentrated sucrose solutions [71% (w/w)] to produce invert sugar syrup with the desired inversion degree. It allows a productivity equal to 9.1 kg sucrose hydrolyzed/h in the case of a 69% (w/w) sucrose initial concentration with a 72% conversion rate.
Instability kinetics of trp operon plasmid ColEl‐trp in recombinant Escherichia coli MV 12[pVH5] and MV 12trp R [pVH5]
Authors: Kim Sung H. , Ryu Dewey D. Y.
Published: December 2004

In studying plasmid instability in recombinant microorganisms, Escherichia coli MV 12[p VH5] and MV 12 trpR[p VH5] harboring trp operon were used as experimental model systems. The host with the trp repression system was partially derepressed by 3‐beta‐indoleacrylic acid. The results from kinetic analysis of plasmid instability showed that the stability of p VH5 and the growth rate of MV 12[p VH5] decreased rapidly in presence of 3‐beta‐indoleacrylic acid at a concentration higher than 10 μg/mL, but beyond 30 g/mL no significant change was observed. This suggests that Trp− variants from MV 12[p VH5] could be produced from the host cells at a different frequency depending on the physiological condition. In another system, MV 12 trpR[p VH5] which was constructed by conjugation of E. coli MV 12[p VH5] with E. coli CSH61, the plasmid stability was much lower and the frequency of Trp− cell production was about 10 times higher as compared with the MV 12[p VH5] when treated with 3‐beta‐indoleacrylic acid. A kinetic model representing the plasmid instability was derived, and a fairly good agreement with the experimental results was found. The fraction of plasmid‐free cell (or negative variant) shows a different time course profile depending on the segregation coefficient (a, production rate of negative variants from positive cells during one generation), growth ratio (G, the ratio of growth rates of negative variants to positive cells), and other parameters. The negative variant fraction continues to increase (“run away” type) or it approaches to a finite value (“settling” type) depending on the relative values of a and G.
Streptomyces flavogriseus cellulase: Evaluation under various hydrolysis conditions
Authors: MacKenzie C. R. , Bilous D. , Johnson K. G.
Published: December 2004

Streptomyces flavogriseus CMCase and Avicelase were very stable at 30°C but not at 40°C or higher. β‐Glucosidase was less stable at all temperatures tested. Stabilities were similar at pH values between 5.5 and 7, the optimal range for enzyme activity. Cellulose solubilizing activity was reduced by 40% at a cellobiose concentration of 150mM but glucose inhibited activity by only 10% at this concentration. β‐Glucosidase was inhibited by 40% at a glucose concentration of 10mM (ten times the substrate concentration). Relatively dilute S. flavogriseus cellulase extensively hydrolysed acid‐swollen cellulose at concentrations as high as 10%. More highly crystalline forms of cellulose were more resistant to attack.
A finite representation model for an asynchronous culture of E. coli
Authors: Domach M. M. , Shuler M. L.
Published: December 2004

A computer model is described which models an asynchronous population of E. coli by using a large, but finite number of representative single cells. Asynchrony generation and maintenance occurs at the single cell level by modulating the activity of an enzyme responsible for septum formation. Such modulation introduces cycle time imprecision and does not require the introduction of any new parameters into the single‐cell model. Based on comparisons to experiment, reasonable predictions are possible for changes of cellular dry weight during exponential growth and turbidostat washout, and overall chemostat cell yields and changes in cell number, glucose concentration, and cell size distribution for a chemostat subject to a step change in dilution rate. Additionally, a correlation between cell RNA content and size is predicted as is an inertial effect when chemostat residence time is decreased under conditions of initially high glucose concentrations. Limitations imposed by the model's finite nature and their solutions are discussed.
The estimation of growth yield and maintenance parameters for photoautotrophic growth
Authors: Lee H. Y. , Erickson L. E. , Yang S. S.
Published: December 2004

Methods are presented for examining the consistency of experimental data for microbial growth where light energy is converted to chemical energy through photosynthesis. True growth yield and maintenance parameters are estimated for several sets of available experimental data. Methods of parameter estimation are presented which allow all of the measured variables to be used simultaneously for parameter estimation. The results show that a wide range of values have been found for the true growth yield and maintenance parameters. Values of the true growth yield range from 0.04 to values above those predicted by the Z‐scheme model for photosynthesis.
Production of ethyl acetate from dilute ethanol solutions by Candida utilis
Authors: Armstrong David W. , Martin Stanley M. , Yamazaki Hiroshi
Published: December 2004

The conversion of ethanol to ethyl acetate has an advantage as a method of ethanol recovery since ethyl acetate is amenable to simple solvent extraction. The potential of Candida utilis in this conversion was studied. The kinetics of accumulation of ethanol and ethyl acetate in glucose‐grown C. utilis showed that ester formation resulted from ethanol utilization under appropriate aeration and was inhibited by Fe3+ supplementation. Candida utilis converted ethanol to ethyl acetate optimally at pH 5.0–7.0. The five‐hour rate of ester production increased as the ethanol concentration increased to 10 g/L, and rapidly declined to zero at concentrations exceeding 35 g/L. Thus, C. utilis has potential to recover dilute ethanol in the form of ethyl acetate.
An evaluation of single‐ and separated‐phase anaerobic industrial wastewater treatment in fluidized bed reactors
Authors: Bull Michael A. , Sterritt Robert M. , Lester John N.
Published: December 2004

Four fluidized bed reactors were used to evaluate single‐and separated‐phase anaerobic treatments of a high strength wastewater. Two reactors were fed with a synthetic wastewater, containing glucose as the primary carbon source, with a COD of 1.2 × 104 mg/L while the remaining pair were fed with a wastewater with a COD of 6000 mg/L. AT each influent strength, one fluidized bed reactor was operated as a single‐phase system while the other was operated as a methanogenic reactor which was preceded by an acidification reactor in a separatedphase system. The reactors were operated under steady‐state and variable process conditions. The separated‐phase system consistently gave a better quality effluent with lower effluent suspended solids and total COD, and the methane yield was also improved. Under variable process conditions, the separated‐phase system was inherently more stable and recovered more rapidly following a shock loading. Propionate and acetate degradation studies indicated that the biomass in the methanogenic fluidized beds of the two‐phase systems was more adapted to volatile acid degradation than the biomass in the single‐phase fluidized beds.
A continuous, farm‐scale, solid‐phase fermentation process for fuel ethanol and protein feed production from fodder beets
Authors: Gibbons William R. , Westby Carl A. , Dobbs Thomas L.
Published: December 2004

Fuel ethanol (95%) was produced from fodder beets in two farm‐scale processes. In the first process, involving conventional submerged fermentation of the fodder beets in a mash, ethanol and a feed (PF) rich in protein, fat, and fiber were produced. Ethanol yields of 70 L/metric ton (7 gal/ton) were obtained; however, resulting beers had low ethanol concentrations [3–5% (v/v)]. The high viscosity of medium and low sugar, beet mashes caused mixing problems which prevented any further increase of beet sugar in the mash. The severely limited the maximum attainable ethanol concentration during fermentation, thereby making the beer costly to distill into fuel ethanol and the process energy inefficient. In order to achieve distillably worthwhile ethanol concentrations of 8–10% (v/v), we developed and tested a solid‐phase fermentation process (continuous). In preliminary trials, this system produced fermented pulp with over 8% (v/v) ethanol corresponding to an ethanol yield of 87 L/metric ton (21 gal/ton). Production costs with this novel process are $0.47/L ($1.77/gal) and the energy balance is 2.11. These preliminary cost estimates indicate that fodder beets are potentially competitive with corn as an ethanol feedstock. Additional research, however, is warranted to more precisely refine individual costs, energy balances and the actual value of the PF.
Optimization of a reactor assembly for the production of 6‐APA from penicillin‐V
Authors: Karlsen Lars G. , Villadsen John
Published: December 2004

The design and operation of an industrial penicillin‐V deacylation reactor is simulated, using a kinetic expression and mass transport parameters for the immobilized enzyme particles which were determined experimentally in a previous study. It is desirable to use a series of equalsized plug flow reactors with pH control at the entrance to each reactor, and with a possibility of recycling reactant in each reactor. These measures are necessary to avoid a steep pH profile through the reactor; the deacylation reaction is accompanied by an increase of acidity of the reaction medium, and H+ is a strong inhibitor and may deactivate the enzyme. The optimization study which is carried out at a fixed penicillin conversion of x = 0.99 shows that it is uneconomical to use penicillin feed concentrations above 150mM–175mM, and that the buffer concentration in the reaction medium should not be less than 50mM–75mM. Increasing the number of reactors from 4 to 8 or 10 leads to higher productivity of 6‐APA, and a moderate recycle in the first couple of reactors diminishes the sharp decrease in pH which will be found in a straight plug flow reactor operation of the equipment. Higher pumping costs and lower productivity are unavoidable drawbacks of an operation mode where the separation costs for the product mixture are desired to be low.
Mixing characteristics and startup of anaerobic downflow stationary fixed film (DSFF) reactors
Authors: Samson Rejean , van den Berg L. (Bert) , Kennedy Kevin J.
Published: December 2004

Tests to determine the mixing characteristics of the anaerobic downflow stationary fixed film (DSFF) reactor during startup showed that mixing characteristics affected performance. Different mixing profiles were obtained by keeping the same flow distribution system and by varying the number of clay channels (1, 4, and 25) in the DSFF reactors (2–32 L). Results with a clean bed reactor indicated a plug flow pattern with a relatively large extent of dispersion. Recirculation dramatically improved the mixing and the residence time distribution (RTD) changed to that of the completely mixed type. Multiple‐channel reactors exhibited a dead space of ca. 12% of the total volume, likely a result of a less than optimally designed flow distributor. A startup period of 90 days was necessary to achieve a maximum loading rate of between 10 and 15 kg COD/m3 day, a volumetric methane production rate of up to 3 m3 (STP)/m3 day and a COD reduction efficiency of up to 90%. For the first 50 days of operation, the difference in achievable volumetric loading rate and volumetric methane production rate was only related to the surface‐to‐volume ratio of the reactors and was not affected by the number of channels present. After 90 days, the bacterial growth on the support material was sufficient to dramatically increase the amount of dead space in the reactors, especially in multiple‐channel reactors (up to 55% of their volume). As a result, the performance of these reactors deteriorated and overloading characteristics were observed. Other results showed that biogas production alone was not sufficient to improve reactor mixing and that little or no shortcircuiting or channelling occurred. Furthermore, the nonmethanogenic bacterial activity in the liquid phase was not affected by the degree of mixing but acetoclastic methanogenic and hydrogenophilic methanogenic activity in the liquid phase were reduced as the fluid flow pattern in the reactor improved.
Stability and performance of mesophilic anaerobic fixed‐film reactors during organic overloading
Authors: Kennedy K. J. , Muzar M. , Copp G. H.
Published: December 2004

The stability of downflow stationary fixed‐film (DSFF) reactors was evaluated under extreme organic shock loads. Reactors could handle five‐ to sevenfold increases in organic loading and recover to normal performance in a relatively short period of time (usually 24–72 h) during treatment of well‐buffered sucrose and acetic acid wastewater at 27 and 35°C. Overloading was characterized by elevated volatile‐acid concentrations, decreased reactor pH, and excess biofilm sloughing. Reactors could not cope with extreme organic shocks during treatment of poorly buffered sucrose wastewater. The pH of the mixed liquor was observed to be a more important factor than the volatile‐acid concentration in determining whether DSFF reactors would recover in a reasonable period of time.
State analysis of fermentation using a mass spectrometer with membrane probe
Authors: Heinzle E. , Kramer H. , Dunn I. J.
Published: December 2004

A new method of continuous process analysis in fermentation using a mass spectrometer (MS) membrane probe is described. A number of samples from industrial fermentations were analyzed for the occurrence of volatiles detectable with a silicone membrane probe connected to a quadrupole MS. In all fermentations, characteristic spectra were observed which were found to change systematically during the batch process. Factor analysis was used to treat the data. The factor scores were compared with the actual product concentrations (antibiotics, toxins, etc.), which were measured using other analytical methods and were found to correlate with them. On‐line analysis was also carried out on a fermentation with an MS and an Apple II microcomputer. Direct monitoring of products, which are not directly measurable with the membrane MS probe requires a new calibration each time conditions such as medium composition are changed.
Kinetics of condensation of glucose into maltose and isomaltose in hydrolysis of starch by glucoamylase
Authors: Shiraishi Fumihide , Kawakami Koei , Kusunoki Koichiro
Published: December 2004

Kinetics of the condensation of glucose into maltose and isomaltose in the hydrolysis of starch by two types of glucoamylase (from Aspergillus niger and Rhizopus niveus) was studied both experimentally and theoretically. A kinetic model for the hydrolysis of starch by glucoamylase from A. niger was proposed. In this model the reversible hydrolysis of maltose and isomaltose and the kinetic parameters change were taken into consideration. Calculated values agreed approximately with the experimental results, and this simple kinetic model was found to have practical use. The rate of condensation of glucose into isomaltose by enzyme from A. niger was about three times larger than that by enzyme from R. niveus. At a higher initial concentration of starch a large amount of isomaltose was reversed, and the glucose yield was reduced significantly after very long reaction times.
Optimizing alcohol production from whey using computer technology
Authors: Zertuche Leticia , Zall Robert R.
Published: December 2004

This study was undertaken with the major goal of optimizing the ethanol production from whey using computer technology. To reach this goal, a mathematical model that would describe the fermentation and that could be used for the optimization was developed. Kluyveromyces fragilis was the microorganism used to ferment the lactose in the whey into ethanol. Preliminary studies showed that K. fragilis produced about 90% of the theoretical ethanol yield when grown in whey‐complemented media. However, when this yeast is grown in nonsupplemented whey media, it does not produce more than 32% of that yield. Comparative batch fermentations of lactose and whey‐complemented media showed that whey possibly contains enhancing components for yeast growth and ethanol production. To obtain the mathematical model, the one‐to‐one effect of the process variables (lactose and yeast extract concentrations, air flowrate, pH, and dilution rate) on the ethanol production were first investigated. Experiments on the pH effect showed that a decrease in pH from 7 to 4 produced an increase in ethanol concentration from 16.5 to 26.5 g/L (50 g/L initial lactose). The results obtained from modeling of the continuous fermentation using the previously listed variables showed that air flowrate, pH, and dilution rate were the process variables that most influence the production of ethanol.
Covalent coupling of microorganisms to a cellulosic support
Authors: Okita W. Blair , Bonham D. Bivings , Gainer John L.
Published: December 2004

Methods for the covalent coupling of microorganisms to a solid support were investigated. Both bacteria and yeast were attached to cellulose particles using cyanuric chloride as the coupling agent, although different experimental procedures were needed for the two types of microbes. This general technique for whole‐cell immobilization offers an advantage over entrapment methods in that the cells are attached to the outer surface of the solid, thus eliminating the resistance of a gel to the transfer of nutrients and products. There are also indications that such immobilized cells show high productivities.