bluuebunny/crossref_metadata_2025 huggingface dataset:
Structure–activity studies on magainins and other host defense peptides
Authors: Maloy W. Lee , Kari U. Prasad
Published: December 2004

Host defense peptides are widely distributed in nature, being found in species from bacteria to humans. The structures of these peptides from insects, horseshoe crabs, frogs, and mammals are known to have the common features of a net cationic charge due to the presence of multiple Arg and Lys residues and in most cases the ability to form amphipathic structures. These properties are important for the mechanism of action that is thougln to be a nonreceptor‐mediated interaction with the anionic phospholipids of the target cell followed by incorporation into the membrane and disruption of the membrane structure. Host defense peptides have been shown to have broad spectrum antimicrobial activity, able to kill most strains of bacteria as well as some fungi, protozoa, and in addition, many types of tumor cells. Specificity for pathogenic cells over host cells is thought to be due to the composition of the cell membranes, with an increased proportion of anionic phospholipids making the pathogen more susceptible and the presence of cholesterol making the host membranes more resistant. Structure–activity relationship studies have been performed on insect cecropins and apidaecins. horseshoe crab tachyplesins and polyphemusins. and the frog magainins. CPFs (caerulein precursor fragments) and PGLa. In general, changes that increased the basicity and stabilized the amphipathic structure have increased the antimicrobial activity: however, as the peptides become more hydrophobic the degree of specificity decreases. One magainin‐2 analogue. MSI‐78. has been developed by Magainin Pharmaceuticals as a topical antiinefective and is presently in clinical trials for the treatment of infected diabetic foot ulcers. © 1994 John Wiley & Sons, Inc.
Design of metal ion binding peptides
Authors: Fattorusso R. , Morelli G. , Lombardi A. , Nastri F. , Maglio O. , D'Auria G. , Pedone C. , Pavone V.
Published: December 2004

Two cyclic and branched peptides (PLA and AZU) were synthesized with the aim of reproducing the active site of the blue copper proteins plastocyanin and azurin. Both peptides, designed on the basis of the x‐ray structures of Poplar plastocyanin and Alcaligenes denitrificans azurin. contain the same coordinating residues of the parent native proteins. The visible spectra of PLA in the presence of equimolar amount of Cu(II) strongly support the interaction between the peptide and copper(II) ion. The CD titration of AZU with the Hg(II) ion indicates for the formation of two species. [A ZUHg]+ and [A ZUHg2]3+ having binding constants (Keq) of 3.106 and 2–104M−1, respectively. © 1994 John Wiley & Sons, Inc.
Enzymatic flavor enhancement in food products: A commercial view
Authors: Marshall W. E.
Published: December 2004

This study illustrates approaches using botanical proteinases and a pancreatic lipase to improve the palatability of two types of food. A third example is presented to illustrate the use of a chelating agent in growing corn to increase the sugar content by over 50%, presumably by influencing enzyme activity in the corncob itself. The purpose is to show that one is not limited to using only the microbial approach for producing flavors but to point out the broader concept of food palatability which includes texture and flavor.
Pore diffusion model for a two‐substrate enzymatic reaction: Application to galactose oxidase immobilized on porous glass particles
Authors: Dahodwala S. K. , Humphrey A. E. , Weibel M. K.
Published: December 2004

An analysis of the pore diffusion model involving a two‐substrate enzymatic reaction is presented. The resulting equations have been applied to the case of galactose oxidase catalyzed oxidation of galactose when the enzyme is immobilized on porous glass particles. The physical constants of the system were obtained by theoretical predictions and the enzyme concentration in the porous medium was derived from the experimental results. The calculations were performed with the assumption that the kinetic parameters of the enzyme remain unchanged upon immobilization. The theoretically calculated effectiveness factors were compared with the experimental effectiveness factors determined from the batch kinetic experiments and were found to be in agreement. The results are presented as effectiveness factor plots graphed as functions of bulk galactose and oxygen concentrations. The model was extended in order to study the effect of external mass transfer coefficients and pore enzyme concentrations on the effectiveness factors.
Immobilization of a cephalosporin acetylesterase by containment within an ultrafiltration device
Authors: Abbott Bernard J. , Cerimele Benito , Fukuda David S.
Published: December 2004

A cephalosporin acetylesterase produced by Bacillus subtilis catalyzes the deacetylation of 7‐aminocephalosporanic acid (7‐ACA). Previous reports from our laboratory described the kinetic constants that characterize the reaction: Km = 2.8 × 10−3M, Kia acetate = 5 × 10−2M, and Kid deacetyl‐7‐ACA = 3.6 × 10−2M. These constants were used to predict the time course of the reaction using the following equation for dual competitive product inhibition.

where St = mg/ml 7‐ACA, At = mg/ml acetate, Dt = mg/ml deacetyl‐7‐ACA. The predicted time course closely matched the time course measured experimentally. The equation also was solved without the inhibition terms and the solution indicated that product inhibition caused about a 30% increase in the time required for complete (>97%) hydrolysis of a 24 mg/ml 7‐ACA solution. The esterase was immobilized by containment within an ultrafiltration device. With this technique the enzyme was reused 20 times over an 11 day span to deacetylate 7‐ACA solutions containing 4 to 24 mg/ml 7‐ACA. The specific activity after the 20th use was the same as the activity prior to the first use, indicating little enzyme inactivation occurred.
Computer assistance in multiparameter flow microphotometry of mammalian cells
Authors: Stoehr Michael , Gebhardt Ulrich , Goerttler Klaus
Published: December 2004

Flow system technology enables the biological and medical experimenter to investigate the distribution spectra of various cellular characteristics separately or in parameter combination on the basis of ultrarapid single cell measurements. A typical rate of recognition is about 1000 to 5000 cells per second and the precision of measurements and their statistical relevance has been previously unobtainable. According to the approach of the multiparameter analysis and high data rate, computer assistance in flow system technology is given primary consideration. In this study three different kinds of software controlled modes in data acquisition are demonstrated: normal acquisition and linear accumulation of single parameters, spectra accumulation of two correlated parameters of each single cell and documentation as linear, two‐ or three‐dimensional distribution pattern, and linear accumulation of two correlated parameters simultaneously with their actual signal‐to‐signal ratio. A first attempt to analyze distribution spectra was the application of the entropy of the structure routinely used in cybernetics. This function seems to be a measure for determining the degree of synchrony in an appropriate pretreated cell population. A special mathematical strategy has been applied to the linear spectra of cellular DNA content, whose advantage is the quantitative extraction of the fractions concerning the various phases of the life cycle cells. The validity of this special curve fitting procedure has been proven on various experimental cell populations.
Microbiological leaching of a chalcopyrite concentrate by Thiobacillus ferrooxidans
Authors: Sakaguchi Hiromichi , Silver Marvin , Torma Arpad E.
Published: December 2004

The microbiological leaching of a chalcopyrite concentrate has been investigated using a pure strain of Thiobacillus ferrooxidans. The optimum leaching conditions regarding pH, temperature, and pulp density were found to be 2.3, 35°C, and 22%, respectively. The energy of activation was calculated to be 16.7 kcal/mol. During these experiments the maximum rate of copper dissolution was about 215 mg/liters/hr and the final copper concentration was as high as 55 g/liter. This latter value is in the range of copper concentrations which may be used for direct electrorecovery of copper. Jarosite formation was observed during the leaching of the chalcopyrite concentrate. When the leach residue was reground to expose new substrate surface, subsequent leaching resulted in copper extractions up to about 80%. On the basis of this experimental work, a flow sheet has been proposed for commercial scale biohydrometallurgical treatment of high‐grade chalcopyrite materials.
Dual control of invertase Biosynthesis in chemostat culture
Authors: Toda K.
Published: December 2004

In a previous study on the chemostat culture of Saccharomyces carlsbergensis, maximum invertase specific activity was observed at an intermediate dilution rate. A possible regulation mechanism, assuming there are simultaneous effects of induction and repression on two sites of the operator loci for invertase formation, is proposed which might account for the observed curve of the dilution rate effect.
Continuous regeneration of NAD(P)+ by flavins covalently bound to sepharose
Authors: Månsson M. O. , Mattiasson B. , Gestrelius S. , Mosbach K.
Published: December 2004

Various flavins, FMN, FAD, and acriflavin, were immobilized to Sepharose using several different coupling methods. The only product stable enough to permit extended studies was acriflavin coupled to epoxy‐substituted Sepharose. The nonenzymic oxidizing capacity towards NAD(P)H was investigated and a 25% specific activity, compared to that of free acriflavin, was observed. The reduced acriflavin was immediately auto‐reoxidized in air and could thus be reused. It was shown that acriflavin‐Sepharose preparations function as NAD(P)H oxidizing agents in a number of different dehydrogenase systems including lactate dehydrogenase (LDH), alcohol dehydrogenase (ADH), malate dehydrogenase (MDH), alanine dehydrogenase (alaDH), and glutamate dehydrogenase (GDH). The amount of expensive coenzyme necessary for high product formation of such systems was thereby markedly reduced.
Kinetics of substrate removal in a completely mixed anaerobic filter
Authors: Dewalle F. B. , Chian E. S. K.
Published: December 2004

A completely mixed anaerobic filter, in which the influent organic matter concentration is diluted with recirculated effluent, was found to effectively remove organic matter concentrations in high strength acidic wastewater, at a range of organic loadings and shock loads. Increases in organic loading had a substantial effect on the relative organic matter composition of the effluent and the magnitude of the fatty acid fraction showed a pattern inverse to that of the nitrogenous organics. A fixed film model was formulated which indicated that at high substrate concentrations the substrate removal rate is proportional to the square root of the substrate concentration and the specific area of the filter medium. A comparison of the biofilm model and the measured effluent concentrations tended to indicate that the substrate removal rate is primarily affected by substrate concentration, specific surface area, flow rate, and temperature of the unit.
Characteristics of hydrocarbon uptake in cultures with two liquid phases
Authors: Nakahara T. , Erickson L. E. , Gutierrez J. R.
Published: December 2004

In hydrocarbon fermentation, the efficiency of hydrocarbon uptake by cells ins one of the keys to the economical production of single‐cell protein. This work is concerned with characterization of cultures with two liquid phases for understanding the hydrocarbon uptake process by cells. Batch cultivation of Candida lipolytica was carried out in shaking flasks and in a tower fermentor with motionless mixers. Micorscopic observation and cell and hydrocarbon concentration distribution in batch cultivation showed that some cells are attached to the large oil drops ad others are free from them. Interfacial tension between oil and water and Sauter mean drop size decreased as cultivation proceeded. On the basis of the experimental results, the process of hydrocarbon uptake by cells is discussed.
Glucoamylase and glucose oxidase preparations and their combined application for conversion of maltose to gluconic acid
Authors: Cho Y. K. , Bailey J. E.
Published: December 2004

The kinetic behavior of a system of multiple enzyme in solution has been studied in a variable volume batch reactor at pH 5, controlled dissolved oxygen concentration, and T = 30°C. The enzymes used were glucoamylase (R. delemar), glucose oxidase (A. niger), and gluconolactonase (A. niger), all of which are important commercial biocatalysts, and a disaccharide was employed as the starting substrate. This study includes the basic kinetic properties of individual enzymes and interactions between components of the reaction mixture. Classical Michaelis–Menten single substrate or two substrate kinetic with parameters based on initial rate data predict correctly the batch time course of the sequential reaction network.
Pressure drop, gas hold‐up, and oxygen transfer in tower systems
Authors: Hsu K. H. , Erickson L. E. , Fan L. T.
Published: December 2004

Pressure drop, gas hold‐up, and oxygen transfer were investigated in a sieve tray column, a column with Koch motionless mixers, and a bubble column. The oxygen transfer experiments were conducted using cocurrent flow of gas and liquid under steady‐state conditions with oxygen transfer from the gas to the liquid phase. The oxygen transfer rates and efficiencies of the sieve tray column and the column with Koch mixers were found to be superior to those of the conventional bubble column. Gas hold‐up was also greater when sieve trays or Koch mixers were inserted in the tower. The pressure drop was found to be primarily due to the liquid head in all three columns.
Bacteriolysis by immobilized enzymes
Authors: Karube Isao , Suganuma Toshiro , Suzuki Shuichi
Published: December 2004

Bacteriolytic enzymes produced by Achromobacter lunatus were immobilized in collagen membrane. Intact bacteria such as Pseudomonas solanacearum, Xanthomonas oryzae, Staphylococcus aureus, and Pseudomonas aeruginosa were lyzed with the bacteriolytic enzyme–collagen membrane. Relative activity of the bacteriolytic enzyme–collagen membrane against Pseu. solanacearum was about 2% of that of native bacteriolytic enzymes. No difference in the optimum pH was observed between immobilized enzymes and native enzymes. The bacteriolytic enzymes in the collagen membrane were stable in the pH range from 4 to 11. The enzyme–collagen membrane was stable against sodium chloride which was an inhibitor of the native bacteriolytic enzymes. Xanthomonas oryzae and Pseu. aeruginosa were continuously lyzed by a reactor containing the rolled bacteriolytic enzyme–collagen membrane.
Pretreatment of cellulosic wastes to increase enzyme reactivity
Authors: Nesse Norvald , Wallick Jack , Harper Judson M.
Published: December 2004

The enzymatic hydrolysis of cellulose to glucose is generally a slow reaction. Different pretreatments, such as ball milling to a −200 mesh or swelling in 1–2% NaOH are reported to increase the reactivity considerably.

In this work a fiber fraction from cattle manure was treated in an autoclave for 5–30 min at temperatures ranging from 130–200°C. The reactivity of the cellulose, measured by incubating samples with a commercial cellulase preparation for one hour at 50°C and pH 4.8, was increased by a factor of 4–6 compared to NaOH treatment and 10–12 compared to untreated fiber. The increased reaction rate is probably mostly due to an increase in cellulose availability to enzymatic attack, as structural hemicellulose is hydrolyzed and removed during the treatment.

Sugars, produced by hemicellulosis, hydrolysis, will react further to give caramelization products. These side reactions were shown to be suppressed by short treatment times. The treated fiber could support growth of a mixed culture of Trichoderma viride and Candida utilis only after washing, indicating the formation of water soluble inhibitory products during treatment.

The treatment with high‐temperature steam can probably be used also with other cellulosic materials to increase reactivity. This may be an attractive way to prepare low‐valued wastes such as manure fibers, straw, stalks, or corn cobs for fermentation processes to increase the protein content or for use directly as ruminant animal feed.
Continuous cultivation of Trichoderma viride on cellulose
Authors: Peitersen Nicolai
Published: December 2004

Using ball milled cellulose as the only carbon source Trichoderma viride was grown in a continuous flow culture at pH = 5.0 and T = 30°C. Steady‐state values for cell protein, cellulose, and cellulase for different substrate concentrations (4–11 g/liter) and dilution rates (0.033–0.080 hr−1) were obtained. Under steady‐state conditions, 50–75% of the cellulose was consumed indicating a critical dilution rate on 0.17 hr−1.

Cellulase activity (U/ml) in the fermentation broth increased slightly with increasing substrate concentration and decreased with increasing dilution rate, while the specific cellulase productivity (U/mg cell protein·hr) was fairly independent of the dilution rate, with a maximum around D = 0.05 hr−1.

Following step changes in substrate concentration and dilution rate, new steady‐state values were reached after three to five residence times (cell protein and cellulose) and four to six residence times (celullase activity).
Enzymatic treatment of primary municipal sludge with Trichoderma viride cellulase
Authors: Cinq‐Mars Gerald V. , Howell John
Published: December 2004

Enzymatic hydrolysis of the cellulose in raw primary settled municipal sludge by Trichoderma viride cellulase achieved conversions of up to 75% of the cellulose, primarily to cellobiose, in 24 hr. Simultaneously the gel‐like characteristic of raw primary sludge was changed to that of a slurry of fine particles in less than 2 hr, causing a radical change in the ability to ultrafilter the sludge.

The use of raw primary sludge as a growth medium for T. viride cellulase production was also investigated. It was possible, with nitrogen supplements, to obtain an enzyme with a filter paper activity (FPA) of two compared to over four which is attainable on defined medium of similar strength.

The potential use of cellulase treatment as a pretreatment or integral part of waste treatment processes is discussed and the alternatives evaluated.
Aeration without air: Oxygen supply by hydrogen peroxide
Authors: Schlegel H. G.
Published: December 2004

Oxygen has been supplied to suspensions of microorganisms kept under nitrogen by the addition of hydrogen peroxide. If catalase was present in the suspension and the flow was adjusted to the rate of oxygen consumption, the cells grew at rates identical to the controls incubated under air. The applicability of oxygen supply by hydrogen peroxide and its limits are discussed.
Kinetics of phosphate limited algal growth
Authors: Nyholm Niels
Published: December 2004

The kinetics of phosphate limited growth of two green algae Chorella pyrenoidosa and Selenastrum capricornutum have been studied in chemostats. Several kinetic models which express the specific growth rate as a function of the intracellular phosphours content have been examined, and one of the models was found to be significantly better than the other models. The principles of this model were described in a recent paper by Nyholm.

The kinetics of phosphate uptake have been investigated by adding pulses of phosphate to the chemostats. The uptake by phosphours deficient cells could be described by Michaelis–Menten kinetics for phosphate concentrations below approximately 500 μg P/liter. Further, with the assumption of a discontinuous adjustment of the uptake rate at the onset of phosphours deficiency, a complete kinetic model for growth and phosphate removal is proposed.

The mean cell size and the contents of chlorophyll and RNA per unit dry weight have been measured for C. pyrenoidosa as a function of the dilution rate.
Oxygen transfer and axial dispersion in an aeration tower containing static mixers
Authors: Maclean G. T. , Erickson L. E. , Hsu K. H. , Fan L. T.
Published: December 2004

Oxygen transfer from gas to liquid under steady‐state cocurrent flow conditions was modeled using the dispersion model, and the oxygen transfer coefficients were estimated from available data for a column with Koch motionless mixers. The dispersion in the column was estimated for several different gas and liquid flow rates using steady‐state tracer experiments. The estimated oxygen transfer coefficients were compared with those estimated using complete mixing and plug flow models. The results indicate that the dispersion model is the most appropriate model for estimating the mass transfer coefficient from the available data.
Growth characteristics of Candida utilis on volatile substrate in a multistage tower fermentor
Authors: Páca Jan , Grégr Vratislav
Published: December 2004

The influence of increasing ethanol concentration in the feed on growth and physiological activity of the yeast Candida utilis was studied. The measurements were made at steady states of continuous culture under constant values of dilution rate, temperature, and pH in all stages of the fermentor. Synthetic ethanol was used as the sole source of carbon and energy in the concentration range 10–100 g/liter.

The maximum biomass concentration in the effluent and maximum productivity was achieved at 75 g ethanol/liter in the feed. In respect to ethanol losses in the outlet and biomass yield, the optimum ethanol concentration in the input of the growth medium was found to be about 50 g/liter using a four‐stage system.
Pepsin immobilized on inorganic supports for the continuous coagulation of skim milk
Authors: Taylor M. J. , Cheryan M. , Richardson T. , Olson N. F.
Published: December 2004

The milk‐clotting enzyme pepsin was immobilized onto beads of alumina, titania, glass, stainless steel, iron oxide, and Teflon for treating skim milk in a fluidized‐bed reactor. Two covalent attachment procedures using silanized supports and glutaraldehyde and two adsorption procedures were evaluated. The three best catalysts were titania and glass, using the covalent attachment procedure, and alumina, using the adsorption procedure at pH 1.2. The pepsin adsorbed on alumina catalyst has commercial potential compared to the previously used glass catalyst. Attempts to increase the stability of pepsin adsorbed on alumina by cross‐linking with glutaraldehyde were unsuccessful owing to the low pH necessary for optimum pepsin adsorption. Desorption of pepsin from alumina during reactor operation was determined. Regeneration of spent catalysts was only partially successful.
Growth kinetics and cellulase biosynthesis in the continuous culture of Trichoderma viride
Authors: Brown D. E. , Zainudeen M. A.
Published: December 2004

Continuous culture studies have been carried out growing Trichoderma viride QM 9123 in a 10 liter stirred fermentor on a medium containing commercial glucose as the carbon source. Experiments were carried out at 30°C and at three controlled pH values of 2.5, 3.0, and 4.0, over a range of dilution rates from 0.01 to 0.11 hr−1. Steady‐state values of cell, glucose, and cellulase concentration oxygen tension, and outlet gas oxygen partial pressure were recorded. Values of maximum specific growth rate, endogenous metabolism coefficient, Michaelis‐Menten coefficient, yield and maintenance coefficient for glucose were derived and correlated the effect of the hydrogen ion concentration. Specific oxygen uptake rates were correlated with specific growth rates and absorption coefficients were shown to be a function of dilution rate independent of pH. Some data on cellulase biosynthesis were examined and correlated in terms of a maturation time model.
Photocontrol of immobilized trypsin activity
Authors: Nakmoto Yoshiaki , Nishida Morie , Karube Isao , Suzuki Shuichi
Published: December 2004

Trypsin was coupled on an agarose gel which was modified with a spiropyran compound. The trypsin–spiropyran (agarose) gel showed reverse photochromism. The activity of the trypsin–spiropyran gel in the dark was 12% of that of native trypsin, and it was higher than that under visible light. The apparent Michaelis constant of the trypsin–spiropyran gel in the dark was larger than that under visible light. On the other hand, the maximum velocity in the dark was higher than that under visible light. The optimum pH of the trypsin–spiropyran gel in the dark was the same as that under visible light. Immobilized trypsin was stable in the pH range from 3 to 9. The trypsin–spiropyran gel was more stable against heat than the native trypsin.
Biological kinetic behaviors and operational performances in aerated and oxygenated systems
Authors: Yang P. Y.
Published: December 2004

Biological kinetic behaviors of the oxygenated and aerated activated sludge process were studied and compared in both once‐through and constant sludge recycle systems. The models derived by Herbert, Elsworth, and Telling [J. Gen. Microbiol., 14, 601 (1956)] and Ramanathan and Gaudy [Biotechnol. Bioeng., 11, 207 (1969)] were used for the studies of once‐through and constant sludge recycle systems, respectively. Soft drink waste water was used for the growth limiting substrate. Temperature was controlled within 30 ± 2°C. The influent substrate concentration was maintained at 1,000 mg/liter. The experiments were conducted at various dilution rates (from \documentclass{article}\pagestyle{empty}\begin{document}$ \frac{1}{9} $\end{document}
to 1/1.0 hr−1), and recycle solids concentration values (from 5,000 to 10,000 mg/liter), with hydraulic recycle ratio, α, at 0.3.

Biological kinetic constants were evaluated and compared. It was found that these constants were different for the aerated and oxygenated systems within a certain range of dilution rates studied. The critical dilution rates for diluting out effluent chemical oxygen demand (COD) occurred at 0.1 and 0.2 hr−1in the once‐through operation, and 0.2 and 0.4 hr−1in the sludge recycle operation for aerated and oxygenated systems, respectively. Observed sludge yield values and specific growth rate were varied with the type of aeration and with and without constant sludge recycle concentration applied. Sludge carbohydrates and proteins content in the oxygenation system (cell recycle) were 10.1–21.6% and 35.6–52.2%. Sludge volume index in the air and oxygenation systems varied from 41.4 to 354 and 31.9 to 58.5, respectively.
1,4‐α‐Glucan phosphorylase from Klebsiella pneumoniae covalently coupled on porous glass
Authors: Wengenmayer Friedrich , Linder Dietmar , Wallenfels Kurt
Published: December 2004

A simplified procedure for the preparation of 1,4‐α‐glucan phosphorylase from Klebsiella pneumoniae is described. An 80‐fold purification is achieved in two steps with an overall yield of about 50%. The specific activity of the homogeneous enzyme protein is 17.7 units/mg. Compared with glycogen phosphorylase from rabbit muscle the enzyme from K. pneumoniae shows a markedly higher stability against deforming and chaotropic agents. The 1,4‐α‐glucan phosphorylase was covalently bound to porous glass particles by three different methods. Coupling with glutaraldehyde gave the highest specific activity, i.e., 5.6 units/mg of bound protein or 133 units/g of glass with maltodextrin as substrate. This corresponds to about 30% of the specific activity of the soluble enzyme. With substrates of higher molecular weight, such as glycogen or amylopectin, lower relative activity was observed. The immobilized enzyme preparations showed pH activity profiles which were slightly displaced to higher values and exhibited an increased temperature stability.
Electric field control of lipase membrane activity
Authors: Karube Isao , Yugeta Yoichi , Suzuki Shuichi
Published: December 2004

Lipase (EC 3.1.1.3., from Pseudomonas sp.) was entrapped in collagen membrane containing liquid crystal (4‐methoxybenzilidene‐4′‐n‐butylaniline). The activity of the lipase–liquid crystal membrane at an applied voltage of 4 V was 3.4 compared to a membrane tested without imposition of an external electric field. A linear relationship was observed between the activity of the lipase–liquid crystal membrane and the current. The apparent Michaelis constant (K′m) of the lipase–liquid crystal membrane under electric field was identical to that of the membrane under ordinary condition. Activation of the lipase–liquid crystal membrane was observed repeatedly, i.e., activation in the presence of an electric field and reversion to a basal level upon removal of the field occurred cyclically. Activity control of immobilized enzymes is desirable for switching devices of a bioreactor. Possible mechanisms of the lipase activation by electric field are discussed.
Electrochemical evaluation of lactate dehydrogenase immobilized in polyacrylamide gels
Authors: Chen A. K. , Liu C. C.
Published: December 2004

Lactate dehydrogenase (EC 1.1.1.27) has been immobilized in polyacrylamide gels over a platinum grid matrix. The immobilized enzyme is used to oxidize L‐lactate in the presence of nicotinamide adenine dinucleotide (NAD+) and femcyanide. The NADH produced is then chemically oxidized back to NAD+by ferricyanide. The coupled reduction of ferricyanide ions to ferrocyanide ions results in a measurable electrochemical potential. This measurable zero‐current potential is found to be Nernstian in nature and directly proportional to the logarithm values of L‐Iactate concentration over the range of 2 × 10−5to 5 × 10−2M. The results indicate that immobilized lactate dehydrogenase can be incorporated into a system to detect L‐Lactate acid in aqueous solutions.
Mechanistic model for microbial growth on hydrocarbons
Authors: Mallee F. M. , Blanch H. W.
Published: December 2004

Based on available information describing the transport and consumption of insoluble alkanes, a mechanistic model is proposed for microbial growth on hydrocarbons. The model describes the atypical growth kinetics observed, and has implications in the design of large scale equipment for single cell protein (SCP) manufacture from hydrocarbons. The model presents a framework for comparison of the previously published experimental kinetic data.
Preliminary cost estimates for commercial fermentation of straw as animal feed
Authors: Grant G. A. , Anderson A. W. , Han Y. W.
Published: December 2004

A preliminary cost estimate was made for two fermentation processes that increase the feed value of grass straw. In one method, straw hydrolyzed with dilute sulfuric acid is fermented by yeast. In the second method, the straw is treated with alkali, then inoculated with cellulolytic bacteria. Both processes increase the digestibility, protein content, and fat content of straw. Production costs estimated for plants processing 100 tons of straw/day by the two methods, were 80 to 88 dollars/ton. Capital costs were estimated at 5.2 million dollars for the acidhydrolysis yeast‐fermentation process and at 3.1 million dollars for the alkalicellulolytic bacteria process. Labor, capital, and energy were significant cost factors for both processes. Caustic costs were important in the alkaline‐treatment cellulolytic bacteria process.
Rapid biodegradation of calcium lignosulfonate by means of a mixed culture of microorganisms
Authors: Ban S. , Glanser‐Šoljan Margareta , Smailagić M.
Published: December 2004

In this paper we discuss the aerobic biodegradation of calcium libnosulfonate (CLS) in a beechwood sulfite waste liquor by means of a mixed culture of microorganisms consisting of two Trichosporn Years and bacteria in the Arthrobacter (two species), Psedomonas, and Chromobacterium genera. Under the established parameters 50% CLS was biodegraded in 24 hr accompanied by the demethylation of methoxyl groups, the splitting of sulpher–carbon bonds, and the appearance of carbonyl and carboxyl groups. The achieved results by determination of phenolic OH groups, as well as established changes of the absorption bands of IR spectra of the CLS molecule and the results of the shortening of the analyses of the C, H, O, and S, show that the degradation of the aromatic nuclei‐culture biodegradation, which confirms the increase in the concentration of conjugated carbonyl groups and carboxyl groups.
Enzymatic lysis of yeast cell walls
Authors: Knorr D. , Shetty K. J. , Kinsella J. E.
Published: December 2004

Lysis of yeast cell walls using zymolase and lysozyme was studied. During coupled zymolase–lysozyme treatment, nearly three times more reducing sugars were released from the yeast cells compared to controls. Enzyme treatment followed by extraction at pH 9 resulted in a yield of more than 80% of the total nitrogen of the yeast cell. Protein degradation occurred during enzyme treatment. The precipitation of proteins was significantly increased by succinylation after enzyme treatment. This also reduced the nucleic acid content of the yeast proteins to less than 2% and enhanced the extractability of nitrogenous material.
Dynamic measurement of the overall volumetric mass‐transfer coefficient in air‐sparged systems
Authors: van Leeuwen C.
Published: December 2004

The determination of the overall volumetric mass‐transfer coefficient with the dynamic measurement technique involves modeling, parameter estimation, and experimental design. The combination and extension of previous efforts lead to some suggestions for improvements.
Comparison of dynamic oxygen electrode methods for the measurement of KLa
Authors: Ruchti G. , Dunn I. J. , Bourne J. R.
Published: December 2004

The dynamic oxygen electrode method for measuring KLa requires the use of a dynamic process model. Six models from the literature are described and compared with respect to their accuracy and ease of use. It is shown theoretically that for sufficient accuracy KLa should be less than the inverse electrode response time. Experimental measurements demonstrate their application to viscous and nonviscous systems. The liquid diffusion film is shown to cause an important measurement lag that can be accounted for by a first‐order time delay. Investigation on the influence of the experimental starting conditions show the importance of the gas and hold‐up dynamics. A new method is proposed to simplify the KLa calculation and to eliminate errors caused by starting conditions. This method, which accounts for gas, film, and electrode dynamical effects, requires only a simple semilog plot of the response data.
Determination of the specific growth of molds on semi‐solid cultures
Authors: Carrizalez V. , Rodríguez H. , Sardiña I.
Published: December 2004

The determination of growth constant of Aspergillus niger were obtained for semisolid cultures on cassava flour, Manihot esculenta, as a sole carbon source. As a consequence, a technique was developed that consisted of the use of a packed‐bed microfermentor with a working volume of 16 cm3. The bed consisted of gelatinized and granulated cassava flour containing mineral nutrients and mold spores. The carbon dioxide produced during the respiration was drawn off with a current of air and then absorbed in a solution of sodium hydroxide. The absorption of CO2, P, was correlated with the specific growth rate μ, by means of the equation P=Keμt, where t is time and K is a constant. Ammonium nitrogen was used as a limiting substrate and its concentration was varied from 0.039 to 2.5% in dry base. The maximum growth rate, μmax, and the saturation constant, Ks, were 0.31 hr−1 and 0.065 mmol (NH4)2SO4/g total dry solids. Substrate inhibition was presented and the constant ki gave a value of 1.5 mmol (NH4)2SO4/g total dry solids. The proposed method is highly recommended for the evaluation of the semisolid fermentation of molds and for strictly aerobic bacteria and yeasts. It can be used especially in the evaluation of the growth of microorganisms on peanut shells, coffee residues, sugar cane bagasse, and other agricultural wastes.
Utilization of partially N‐succinylated derivatives of chitosan and glycolchitosan as supports for the immobilization of enzymes
Authors: Yamaguchi Ryuji , Arai Yuji , Kaneko Takeshi , Itoh Tatsuro
Published: December 2004

Polymer ampholites, partially N‐succinylated chitosans (PSC), and partially N‐succinylated glycolchitosans (PSGC) were prepared from chitosan (an N‐deacetylated chitin) and glycolchitosan (a partially O‐2‐hydroxyethylated chitosan), and they were utilized as novel supports for the immobilization of enzymes. The immobilization was conducted simultaneously with gelation of PSC and PSGC by reaction with water‐soluble carbodiimide in the presence of enzymes. Enzymes were covalently bonded on PSC and PSGC chains. Maximum activity yields of glucoamylase, β‐fructosidase, and D‐glucose isomerase were 58.8, 64.3, and 65.2%, respectively. Favorable activity yields of glucoamylase and β‐fructosidase were attained with PSC and PSGC having high degree of N‐succinylation, but those of D‐glucose isomerase were not affected by the degree of N‐succinylation (DS). The activity of immobilized glucoamylase was retained up to 85.5% over 30 batch reactions.
Continuous‐culture studies on the regulation of tylosin biosynthesis
Authors: Vu‐Trong K. , Gray P. P.
Published: December 2004

The metabolic regulation of tylosin synthesis by Streptomyces fradiae NRRL 2702 was studied in batch and chemostat cultures using a soluble synthetic medium. In batch culture a medium which diminished the trophophase‐idiophase kinetic pattern was used to assess the activities of the enzymes involved in tylosin synthesis. The enzymes methylmalonyl‐coenzyme A carboxyltransferase (EC 2.1.3.1) and propionyl‐coenzyme A carboxylase (EC 6.4.1.3) showed early enzymatic derepression, both enzymes reaching their highest specific activities after 72–96 fermentation. The activity of macrocin 3′ ‐O‐methyltransferase, the enzyme catalyzing the conversion of macrocin (tylosin C) to tylosin (tylosin A). also peaked at 72 h. The specific activities of the three enzymes showed close correlation with the qtylosin value. In chemostat cultures the activities of the enzymes and the intracellular level of the adenylate pool and energy charge were studied as a function of dilution rate. Under steady‐state conditions, increases in the specific growth rate repressed the enzymes activities with a concomitant increase in the intracellular level of the adenylate pool, while the adenylate energy charge remained almost constant and in the range 0.5–0.52. The highest specific activities of the enzymes were observed when D = 0.008 h −1. The specific rate of tylosin synthesis was inversely proportional to the specific growth rate and the intracellular level of adenylate pool. The pool of adenylate could be a nutritional parameter which had a considerable influence on the biosynthesis of tylosin.
Immobilized microbes and a high‐rate, continuous waste processor for the production of high Btu gas and the reduction of pollutants
Authors: Messing R. A.
Published: December 2004

Microbes capable of degrading organic wastes (sewage) are densely packed (immobilized) within the pores of controlled‐pore ceramics. When the ceramic displays the optimum pore range for the reproduction of these microbes, the minimum volume for a very efficient reactor is required. A two‐stage, anaerobic, immobilized microbe reactor has been designed, and laboratoryscale units have been constructed. A few of these units have been operated continuously for two years. These reactors were designed for the efficent conversion of carbon to methane in biodegradable molecules and for the effective transfer of that gas. The reactors were operated at 20, 30, and 40°C at residence times of 2–5.5 h. The total chemical oxygen demand (COD) of the sewage varied from 800–2600 mg/L. The resulting gas contained greater than 90% methane and less than 5% CO2. Approximately 32–54% of the influent total carbon was recovered as methane. The reduction in COD varied from 63 to 89%.
Growth characteristics of bakers' yeast in ethanol
Authors: Wasungu Kowda M. , Simard Ronald E.
Published: December 2004

The influence of temperature (15° −40°C) and pH (2.5–6.0) on the continuous growth of bakers' yeast (Saccharomyces cerevisiae) at steady state in 1% ethanol was investigated. Optimal temperature and pH were 30°C and 4.5, respectively. The short‐term effect of ethanol concentration (0.1–10.0%) on the yeast growth was assessed in batch culture. Up to 1% of ethanol, the yeast growth increased in function of the ethanol concentration in the medium. The biomass reached a maximum within the interval of 1–4% of ethanol (7.9 and 31.6 g/L, respectively) and decreased at higher concentrations. The residual ethanol concentration in the medium increased rapidly when the initial ethanol concentration exceeded 4%. The best‐fit model obtained for growth inhibition as a function of ethanol concentrations was that of Tseng and Wayman: μmS/)K + S( − i (S − Sθ). With this model, the specific growth rate (μ) decreased linearly as the ethanol concentration increased between the threshold value (Sθ) of 11.26 g/L to be fully inhibited at 70.00 g/L (S;) an inhibition constant (i) of 0.0048 g L−1 h−1, a maximum specific growth rate (μm) of 0.284 h−1, and a saturation constant (K) of 0.611 g/L were obtained.
Diffusive and hydraulic transfer of solutes through homogeneous membranes
Authors: Sada Eizo , Katoh Shigeo , Miyai Kiyosato , Terashima Masaaki , Yoshida Shuichi
Published: December 2004

Rates of hydraulic transport of water, solute permeabilities, and sieving coefficients of homogeneous κ‐carrageenan and bovine serum albumin membranes were measured. These values increased with the water content of membranes. The data show good agreement with the predictions based on the pore model.
Studies on Scenedesmus acutus growth II. Effect of autotrophic and mixotrophic growth on the amino acid and the carbohydrate composition of Scenedesmus acutus
Authors: Shamala T. R. , Drawert F. , Leupold G.
Published: December 2004

As a general rule an increase in carbohydrates occurs during the light phase of the cell cycle and that of protein during phase, although variations were found in these components under autotrophic and mixotrophic growth conditions. The results are based on the quantitative determination of carvohydrates as trimethylsilyl (TMS) derivatives and amino acids as N‐trifluoroacetyl‐n‐butyl (TAB) esters in algal cells cultured in light and dark periods by gas‐liquid chromatography (LC). Cells harvested during the dark period contained more amino acids as compared to similar cultures harvested during the light phase. In light, the production of amino acids of the aspartate family increased in cells cultivated with glucose and carbon dioxide. With glucose as sole carbon source, the carbohydrate content was higher in the dark than in the light period. Under continuous light conditions, in the presence of carbon dioxide, there was a decrease in the carbohydrate content also. Gas–liquid chromatography analysis of the extract of the purified cell walls showed that they are made up of 0.076% carbohydrates and 0.28% amino acids on the dry weight (DW) basis of whole cells. The results on the metabolism of cells, under autotrophic and mixotrophic conditions, are discussed in this article.
The kinetics of yeast growth and nicotinic acid production
Authors: Tseng Murray M‐C. , Phillips Colin R.
Published: December 2004

Production of nicotinic acid from Saccharomyces cerevisiae in exponential growth on glucose was found to be growth associated, and in the stationary and decline phase was found to be death associated. A kinetic model was developed to describe the kinetics of growth of S. cerevisiae and the production of nicotinic acid.
A collagen–alkaline phosphatase conjugate membrane: Enzymatic kinetics in‐vitro stability
Authors: Jefferies Steven R. , Gutmann James L.
Published: December 2004

Collagen‐alkaline phosphatase membranes have been prepared, and their enzymatic kinetics and in‐vitro stability analyzed. Collagen–alkaline phosphatase dispersions were prepared by complexation in aqueous alkaline solution and cast into membranes by controlled dehydration. These membranes were then crosslinked in glutaraldehyde solution, washed thoroughly, and dried. Crosslinking in glutaraldehyde confers increased stability of catalytic activity to these collagen–enzyme membranes, especially when compared to uncrosslinked collagen–alkaline phosphatase membranes assayed in a similar fashion. Crosslinking in glutaraldehyde also appears to inhibit gross leaching of the soluble enzyme from the carrier matrix. Apparent intrinsic kinetic properties of the collagen–alkaline phosphatase conjugate were analyzed in membranes of various thickness in order to determine the effect of internal diffusion resistances on the kinetics of the immobilized enzyme. The apparent Michaelis constant of the immobilized enzyme decreased as a function of decreasing membrane thickness, reaching an observed apparent Michaelis constant of 1.6mM at a membrane thickness of 0.2 mm. Extrapolation of the apparent Michaelis constant to zero membrane thickness, using a linear plot of the natural logarithm of the apparent Michaelis constant versus membrane thickness, allowed estimation of the true Michaelis constant of the immobilized enzyme. The estimated value for the true Michaelis constant of the collagen–alkaline phosphatase complex was 0.7mM. This value agrees closely with reported values for several purified mammalian alkaline phosphatase. The apparent Michaelis constant for the 0.2mm collagen‐enzyme membrane agrees closely with the Michaelis constant reported for an alkaline phosphate purified from chondrocyte matrix vesicles. The intrinsic maximum reaction velocity (Vm) of the collagen–enzyme complex was estimated b plotting the observed reaction rate as a function of decreasing membrane thickness and extrapolating such plots, at various substrate concentrations, to the limiting case of zero membrane thickness. The maximum reaction velocity was obtained by the common intercept of these plots as they approached zero membrane thickness.
Mathematical description of competition between two and three bacterial species under dual substrate limitation in the chemostat: A comparison with experimental data
Authors: Gottschal Jan C. , Thingstad T. Frede
Published: December 2004

A mathematical model is presented which describes the growth of two bacterial species in mixed chemostat cultures under dual substrate limitation. Competition experiments between a facultatively chemolithotrophic Thiobacillus and either a heterotroph or an obligately chemolithotrophic Thiobacillus served as an experimental model system [Gottschal, de Vries, and Kuenen, Archives of Microbiology, 121, 241–249 (1979)]. Furthermore, the introduction of Monod‐type growth kinetics in the model allowed an assessment of the relative importance of the growth parameters for the outcome of the competition. In addition, it is shown how the results of the mathematical description of the two‐membered mixed cultures can be used to predict the outcome of the competition between the three species competing for the two growth‐limiting substrates acetate and thiosulfate in a three‐membered mixed culture. In contrast to the experimental data of Gottschal, de Vries, and Kuenen it is predicted that two of the three species or only one of them (the “mixotroph”) will survive in the culture. Within the framework of the proposed mathematical model, two possible explanations for the experimentally observed coexistence of three species are suggested: either the very slow dynamics of the system did not allow the attainment of a true steady state within the time scale of the present experiments or some parameters describing the mixed culture were extremely sensitive towards minor fluctuations in dilution rate. The results of the present mathematical model support the view that facultatively chemolithotrophic bacteria are able to survive under appropriate limiting mixed substrate conditions in the presence of more “specialized” heterotrophs and obligately chemolitotrophs, in spite of their relatively low specific growth rate.