bluuebunny/crossref_metadata_2025 huggingface dataset:
Bubble flow in the downflow section of an airlift tower
Authors: Orazem M. E. , Fan L. T. , Erickson L. E.
Published: December 2004

Characterization of the two‐phase flow in the downflow section of the airlift tower is necessary for accurate modeling of the airlift tower. A Split‐cylinder airlift tower was investigated for superficial gas velocities ranging from 0.0683 to 0.3315 m/sec for an air–water system. Statistical cross‐covariance techniques were used to yield velocities, void fractions, and flow rates corresponding to upward and downward components of bubble flow in the downflow section of the airlift tower. From these results the fraction of incoming air entrained in the downflow section was determined as a function of superficial gas velocity and position.
Whole‐cell hollow‐fiber reactor: Effectiveness factors
Authors: Webster I. A. , Shuler M. L. , Rony P. R.
Published: December 2004

Analytical expressions, which allow the generation of effectiveness factor graphs for a reactor system employing immobilized whole cells a biocatalyst, are presented. In particular hollow‐fiber devices (such as dialysis or ultrafiltration units) are considered. Such devices are analogs to a shell‐and‐tube heat exchanger. Whole cells are entrapped on the shell side: a nutrient solution is circulated through the tubes, substrate diffuses from the tube side, across the fiber, and into the cell mass on the shell side, where it irreversibly reacts to form product. The product back‐diffuses into the circulating nutrient solution. The overall substrate mass‐transfer process is hypothesized to be either diffusion limited in the hollow‐fiber tube wall and/or the shell‐side cell suspension and/or reaction limited at the enzyme sites within the whole cells. The first‐ and zero‐order limits of the Michaelis‐Menten rate law are used in generating effectiveness factor expressions. The effectiveness factor is a function of reaction order, Thiele modulus, diffusion coefficient ratio (defined as the effective substrate diffusivity in the hollow‐fiber membrane wall divided by the effective substrate diffusivity in the cell suspension), partition coefficient, volume of the cell suspension, and hollow‐fiber width. Equations for the effectiveness factor are also detailed when the hollow‐fiber mass‐transfer resistance is far greater than the cell suspension mass‐transfer resistance. An effectiveness factor chart is presented specifically for the commercially available C‐DAK 4 dialyzer (Cordis Dow Co., Miami, Florida). In general terms the effectiveness factor expressions are applicable for characterizing diffusion and reaction within a catalytically active cylindrical annulus, Whose inner surface offers a diffusional resistance and whose outer surface is impermeable to reactants. Some generalization of the Thiele modulus is undertaken which serves to draw the asymptotes on the effectiveness factor charts together. Comment is made on the variation of the slope of the effectiveness factor graph and its relation to the change in the observed reaction activation energy. Possible application of the model to the catalytic tube wall reactor is discussed.
Production of aflatoxin in corn by a large‐scale solid‐substrate fermentation process
Authors: Silman R. W. , Conway H. F. , Anderson R. A. , Bagley E. B.
Published: December 2004

Culturing of Aspergillus flavus was conducted in static flask cultures and 4 in. × 5 ft columns (containing 7–8 kg corn) to measure the effects of moisture, temperature, and air flow upon growth and the production of aflatoxin. Aflatoxin levels as high as 6200 ppb (dry basis) in 10 days were observed. Conditions were selected (ca. 20% moisture, 0.008 liter air/kg corn/min air flow with 1.5 liter/kg/min recirculated) for production of aflatoxin in 1200 bushels of corn in a 18‐ft diam corrugated steel Butler storage bin for preparation of contaminated corn for animal feeding trials and for testing of an ammoniation process for decontamination of aflatoxin in corn. A target level of 1000 ppb aflatoxin was attained.
Effect of interstage mixing in multistage culture systems on continuous biomass production
Authors: Páca Jan , Grégr Vratislav
Published: December 2004

The significance of the interstage mixing on important process parameters of biomass production was studied. The experiments were performed in a multistage tower fermentor and in fermentors in series. The interstage mixing effect can be evaluated under conditions of geometrical similarity, identity of oxygen transfer rate, and identity of dilution rate per stage in the individual stages of both culture systems. Candida utilis was cultivated on a synthetic medium with ethanol as the sole carbon and energy source in the concentration range 10–100 g/liter. Dilution rate, temperature, and pH in each stage of both culture systems were kept constant. It was demonstrated that in the multistage tower fermentor the definite backflow which ensures the permanent reinoculation by adapted cells significantly decreases the inhibitory effect of higher ethanol concentrations on the cell growth and on the rate of ethanol utilization.
Application of balancing methods in modeling the penicillin fermentation
Authors: Heijnen J. J. , Roels J. A. , Stouthamer A. H.
Published: December 2004

This paper shows the application of elementary balancing methods in combination with simple kinetic equations in the formulation of an unstructured model for the fed‐batch process for the production of penicillin. The rate of substrate uptake is modeled with a Monod‐type relationship. The specific penicillin production rate is assumed to be a function of growth rate. Hydrolysis of penicillin to penicilloic acid is assumed to be first order in penicillin. In simulations with the present model it is shown that the model, although assuming a strict relationship between specific growth rate and penicillin productivity, allows for the commonly observed lag phase in the penicillin concentration curve and the apparent separation between growth and production phase (idiophase–trophophase concept). Furthermore it is shown that the feed rate profile during fermentation is of vital importance in the realization of a high production rate throughout the duration of the fermentation. It is emphasized that the method of modeling presented may also prove rewarding for an analysis of fermentation processes other than the penicillin fermentation.
Hydrolysis of urea by gelatin‐immobilized urease: Separation of kinetic and diffusion phenomena in a model immobilized‐enzyme‐reactor system
Authors: Bollmeier John Philip , Middleman Stanley
Published: December 2004

Experiments and appropriate mathematical models are presented in an attempt to elucidate and separate the effects of mass transfer and immobilization on the apparent kinetics of hydrolysis of urea by urease immobilized within a crosslinked gelatin film. Diffusion of urea through the gelatin matrix appears to exert the major influence on the observed kinetics. Diffusion coefficients are measured, and a model for the “effectiveness factor” is presented, accounting for this aspect of mass transfer control. A secondary, but significant, influence on apparent kinetics arises because the reaction products lead to an increased pH level which, because of diffusion resistance, remains high within the gelatin matrix. For pH levels in the 6.7 to 9.0 range the activity of urease is a strongly decreasing function of pH. An approximate model accounting for ionic equilibrium allows this pH–diffusion effect to be introduced in such a way as to lead to predictions of the apparent kinetics that are compared with experimental observations. Examination of these results indicates that the immobilization procedure leads to some loss of activity due to an interaction of the gelatin crosslinking reaction with the enzyme itself.
Preparation of immobilized phosphodiesterase from calf spleen and its use in oligonucleotide analysis
Authors: Seliger H. , Teufel E. H. , Philipp M.
Published: December 2004

The phosphodiesterase from calf spleen (EC 3.1.4.18) was immobilized on several supports. Some properties of the most suitable enzyme support system—calf spleen phosphodiesterase bound to agarose‐Concanavalin A—were investigated, e.g., pH dependence, influence of ionic strength of the buffer medium, and Zn2+‐ion inhibition. The immobilized spleen phosphodiesterase showed about 60% of the activity of the free enzyme: the activity toward several oligonucleotide test substrates was unchanged for two months.
Kinetics of microbial death by combined treatment with heat and antimicrobial agents
Authors: Tsuchido T. , Shibasaki I.
Published: December 2004

Studies were made of the death kinetics of Escherichia coli cells heated at 46 to 56°C in 0.05M phosphate buffer (pH 7.0) containing either an amphoteric surfactant (Tego 15DL, 1–10 μg/ml) or sorbic acid (0.5 to 3%). A linear relationship was obtained on the Arrhenius plot for the death of cells heated with each antimicrobial agent. The kinetics of the action of the surfactant, however, differed from that of sorbic acid. With the amphoteric surfactant, the activation enthalpy of the death reaction decreased from 108 to 51 kcal/mol as the concentration of surfactant was increased in the range tested although the death rate remained high; whereas with sorbic acid the activation enthalpy remained fairly constant (104 ± 9 kcal/mol) independent of its concentration and the death rate was similarly high. Further, in the action of the amphoteric surfactant, a thermodynamic compensation effect was observed, the compensation temperature being 334°K (61°C), i.e., relatively close to the observed temperatures. For sorbic acid, however, this temperature seemed to be too high to observe when determined from the Arrhenius plot. The data of the dependency of the death‐rate constant upon the concentration of antimicrobial agent indicated a similar difference in the action of the two agents. Based on our results and on data obtained by other workers, we propose that antimicrobial agents that enhance cellular death induced by heating can be characterized into two types.
Dynamic aspects of radiorespirometry during the cell cycle of Candida utilis: Some observations in phased culture under carbon‐, nitrogen‐, and phosphorus‐limited growth
Authors: Dawson Peter S. S. , Steinhauer Lee P.
Published: December 2004

Many changes that occur in a cell during the cell cycle can be demonstrated in synchronous cultures and can reveal dimensions of cell metabolism not attainable by the study of balanced growth of asynchronous populations in batch cultures or the steady state in chemostat cultures. The release of 14CO2 from specifically labeled glucose by phased (continuously synchronized) cultures follows a characteristic pattern (profile) that depends upon the stage in the cell cycle and the period of labeling used. Successive profiles throughout a cycle showed differences that were altered under different nutrient‐limiting growth conditions. Profiles obtained with glucose‐1‐14C, glucose‐2‐14C, glucose‐3,4‐14C, and glucose‐6‐14C and phased cells of Candida utilis under N‐, P‐, and C‐limited growth demonstrated the variable character of the metabolic activity that occurred in the cells while contour changes within the profiles across the cycle indicated possible correlations with activities of the hexose monophosphate, Embden‐Meyerhof‐Parnas, and tricarboxylic acid cycle pathways during the cell cycle. The basis of these changes and their use as elementary parameters for study of problems of physiological changes in vivo are considered.
Immobilization of β‐galactosidase, albumin, and γ‐globulin on epoxy‐activated acrylic beads
Authors: Hannibal‐Friedrich Otto , Chun Moonjin , Sernetz Manfred
Published: December 2004

A comparative study was conducted into the immobilization of β‐galactosidase, albumin, and γ‐globulin on an epoxy‐activated polyacrylic matrix (oxirane C, Röhm‐Pharma GmbH, Darmstadt). The kinetic parameters of the immobilized β‐galactosidase were investigated with three kinds of miniaturized analytical reactors: namely, stirred batch, continuous stirred‐tank, and packed‐bed reactors. The optimum binding conditions, saturation activity and Michaelis constant of immobilized β‐galactosidase are given, together with determinations of the binding capacity of the oxirane C matrix for the three proteins investigated. For beta;‐galactosidase a saturation activity of 1300 U/g oxirane C was reached. The maximum binding, achieved by experiment, was 140 mg/g with 0.69 yield for albumin, 120 mg/g with 0.61 yield for γ‐globulin, and 40 mg/g with 0.42 yield for β‐galactosidase. From these data the inner surface of the matrix as a function of the size of the bound proteins was estimated.
Enzyme electrode for phenol
Authors: Kjellén Karin G. , Neujahr Halina Y.
Published: December 2004

An enzyme electrode is described for quantitative determination of phenol at micromolar concentrations. Immobilized phenol hydroxylase is attached to the surface of a Clark oxygen electrode. The Maximum rate of oxygen consumption is linearly dependent on phenol concentration over the 0.5–50μM range. The electrode can be used for at least 150 assays without an activity loss. Readout is very rapid—within 30 sec of sample addition. The electrode response is independent of pH between pH 6.5 and 9.5. The response increases linearly with temperature in the interval 10–40°C. It is necessary to incubate the enzyme electrode in a buffer containing NADPH for a few minutes before the addition of sample. This is to make the electrode response independent of the diffusion rate of this cosubstrate. This and other diffusional effects on the performance of the phenol electrode are discussed.
Stability of the Cellulase of Trichoderma reesei under use conditions
Authors: Reese Elwyn T. , Mandels Mary
Published: December 2004

Enzyme stability studies have been reinvestigated under the conditions used for cellulose hydrolysis (pH 4.8, 50°C, 24 hr). The cellobiohydrolase (CBH) component as measured on Avicel is less stable than other enzymes of the cellulase complex, and is 60% inactivated by merthiolate (and other Hg compounds) under the above conditions. Endo‐β‐1,4‐glucanase is much more stable, and more resistant to merthiolate and other compounds. Under unshaken conditions the Avicelase of the Rutgers strain C 30 shows greater stability to heat than that of other available strains. Biocides must be selected not only for their ability to prevent contamination, but also for their compatibility with cellulases. Tetracycline and chlortetracycline are inexpensive, effective in very low concentrations, have no harmful effect on the enzymes, and are compatible with the yeasts that subsequently grow on the sugar solutions to produce alcohol. Attempts have been made to stabilize the enzymes by chemical modification in such a way as to maintain their solubility. Glutaraldehyde treatment greatly increased the enzyme size, lowered the pI values, and gave a slight shift in the pH activity curve. There was, unfortunately, no increase in enzyme stability, and the activity of enzymes on solid celluloses was adversely affected. Shaking greatly reduced the hydrolysis of Avicel by Trichoderma reesei C 30 enzyme. The adverse effect was accompanied by a decrease in recoverable enzyme and protein.
Growth and anthocyanin production by carrot suspension cultures grown under chemostat conditions with phosphate as the limiting nutrient
Authors: Dougall Donald K. , Weyrauch Keith W.
Published: December 2004

Chemostat cultures of carrot suspension cultures, where growth was limited by the concentration of phosphate in the input medium, were achieved by replacing a fixed proportion of the culture with fresh medium at daily intervals. In the range 0.05–0.30mM phosphate in the input medium and at a specific growth rate of 0.357 days−1, steady‐state culture density but not anthocyanin in the cells was strictly proportional to the input phosphate concentration with no intercept. At a phosphate concentration of 0.10mM and growth rates from 0.105 to 0.430 days−1, the steady‐state culture density could not be described by Monod's model of chemostat cultures, but could be described by Nyholm's model. The steady‐state levels of anthocyanin were not strictly proportional to the steady‐state biomass under all conditions, showing that anthocyanin production is not completely growth associated.
Growth energetics in the production of bacterial single cell protein from Methanol
Authors: Drozd J. W. , Wren S. J.
Published: December 2004

Bacteria grown on methanol exhibit a poor efficiency of energy conservation, which is mainly due to the low P/O ratio of 1 associated with methanol oxidation. Thermodynamic considerations indicate that a P/O ratio of at least 2 is possible for this step in substrate oxidation. This low efficiency of energy conservation is reflected in the yield values on methanol, which are very important in the consideration of biomass production from methanol. Unfortunately in continuous culture there is no obvious way to select for organisms with a greater efficiency of energy conservation.
Hydrophobic chromatography of β‐galactosidase
Authors: Chang C.‐T. , McCoy B. J. , Carbonell R. G.
Published: December 2004

The hydrophobic interaction of β‐galactosidase with Sepharose 4B substituted with 3,3′‐diaminodipropylamine was studied in both batch and column experiments. The equilibrium and the binding rate constants were determined for different phosphate buffer concentrations. The equilibrium constants exhibit a hysteresis effect, i.e., desorption constants are less than adsorption constants, and the higher the ionic strength to start the desorption, the larger the effect. The rate data are not satisfactorily described by a simple reversible first‐order model. The column chromatographic data are semiquantitatively described by a local equilibrium theory without axial dispersion or intraparticle diffusion.
Enzyme formation during solid‐substrate fermentation in rotating vessels
Authors: Silman Robert W.
Published: December 2004

Aspergillus awamori NRRL 4869 was cultured on the solid substrate, wheat bran, in a modified Rollacell apparatus to produce α‐galactosidase and invertase. The swivel cap on the elongated bottle permits the introduction of air while the bottle rotates. Parameters of air flow rate (0.05–0.2 liter/kg/min), rpm (0.15–15 rpm), and weight of solids (150 and 300 g) were varied. At low air flow rates (0.05 liter/kg solid/min), α‐galactosidase production was minimal independent of the rotation rate. At 0.15 rpm and 0.2 liter/kg solids/min air flow rate, invertase production ceased after five days; whereas α‐galactosidase production continued. The modified Rollacell can be a useful apparatus for studying solid‐substrate cultures.
Monolayer cultures of animal cells with the gyrogen equipped with tubes
Authors: Girard H. C. , Sütcü M. , Erdem H. , Gürhan I.
Published: December 2004

The gyrogen with tubes has been the object of repeated trials carried out over a period of some years. The aim of these trials was essentially to multiply BHK cells in monolayer and to reproduce the FMD virus in one operation. At the laboratory stage, the gyrogen represented three roller flasks; at the pilot stage, 100 roller flasks; and at the industrial stage, 500 flasks. Culturing cells on a glass support, is not in itself new, but the difficulty appeared when replicating the virus in order to obtain the high parameters necessary for vaccine production. Everything was accomplished so that finally the cell culture and viral multiplication could be carried out in situ in the same apparatus.
Hydrolysis of raffinose in a hollow‐fiber reactor using an unrefined mixture of α‐galactosidase and invertase
Authors: Silman R. W. , Black L. T. , McGhee J. E. , Bangley E. B.
Published: December 2004

Raffinose was converted enzymatically in a hollow‐fiber reactor to melibiose, sucrose, galactose, glucose and fructose. The enzymes were a crude extract of α‐galactosidase and invertase produced by Aspergillus awamori NRRL 4869 on a solid substrate, Wheat bran. With a concentration of raffinose, C0, entering the reactor at a flow rate Q, and with C being the concentration of raffinose exiting the reactor, the conversion (C/C0), was studied as a function of Q at two level of C0. The data could be fairly well fitted using the analysis of Waterland et al. even though a mixed crude enzyme system was being investigated. It was found empirically that In (C/C0) was linear in Q−1, with the absolute value of the slope decreasing with increasing C0. The linearity of such plots were predicted by Lewis and Middleman from Waterland et al. for a single enzyme system obeying first‐order kinetics, the slope being independent of C0. Although the assumptions involved in this approximate analytical solution are not valid, the observed linearity of the In (C/C0) vs. Q−1 plots is excellent and should prove useful in reactor design considerations.
Effect of external mass transfer of activation energy of hydrolysis of BAEE and casein by trypsin immobilized on molecular sieve type 4A
Authors: Mukherjea R. N. , Bhattacharya P. , Gangopadhay T. , Ghosh B. K.
Published: December 2004

In this investigation, the activation energies of the hydrolysis of N‐(α)‐benzol‐L‐arginine ethyl ester (BAEE) and casein have been determined using trypsin immobilized on molecular sieve type 4A. There is a complete absence of intraparticle diffusion in the system, and the temperature dependence of the reaction has been studied only under external diffusional limitation. While the hydrolysis of BAEE by bound trypsin in found to be controlled by external diffusion, that of casein is kinetically controlled.
Pulse response in an immobilized‐enzyme column: Theoretical method for predicting elution curves
Authors: Adachi S. , Hashimoto K. , Matsuno R. , Nakanishi K. , Kamikubo T.
Published: December 2004

A theoretical method for predicting the elution profile of a pulse response in an immobilized‐enzyme column is proposed. The method is based on a mass balance model, which is extensively used in gel chromatography. To test the method, a pulse of sucrose solution was applied to a column of spherical acrylamide gel in which was entrapped invertase from yeast, and it was eluted with 0.05M acetate buffer at pH 5.0. The elution curves of the substrate and the product were in fairly good agreement with the theoretically calculated ones. The method was extended to the system of reversible as well consecutive reactions.
Estimation of Trichoderma QM 9414 biomass and growth rate by indirect means
Authors: Harima Takeshi , Humphrey Arthur E.
Published: December 2004

Trichoderma QM 9414 was aerobically grown on glucose as the sole carbon and energy sources in a chemostat culture. The specific rates of glucose consumption (QG), oxygen consumption (Q), and carbon dioxide production (Q) at the steady state were measured to estimate the growth and maintenance requirements. From the results it was estimated that 2 mol adenosine triphosphate (ATP) were produced when1 mol NADH was oxidized through the respiratory chain of this microorganism. The true growth yield for ATP (YATP) and specific ATP consumption rate for maintenance (Q) calculated with this value were 0.0106 g dry cell/mmol ATP and 5.2 mmol ATP/g dry cell/hr, respectively. Using the relationships between specific growth rate (μ) and (Q) and between μ and QG obtained from chemostat‐culture data, cell and glucose concentration histories were estimated from the carbon dioxide production rate during the batch culture. The estimated cell concentrations agreed with the experimentally measured values. Glucose concentration were slightly overestimated.
Methane production from wastewaters by immobilized methanogenic bacteria
Authors: Karube Isao , Kuriyama Shinichi , Matsunaga Tadashi , Suzuki Shuichi
Published: December 2004

A methanogenic population was immobilized onto agar gel, polyacrylamide gel, and collagen membrane. Agar‐gel‐entrapped methanogenic microorganisms gave the highest activity. The optimum agar concentration was between 1.5 and 3% (w/v), and the optimum microbial content was 20 mg wet cells/g gel. The optimum conditions for methane production by immobilized whole cells were pH 7.0–7.5 and 37–45°C. The rate of methane production was initially 1.8 μmol/g gel/hr. Methane productivity was gradually increased and reached a steady state (4.5μmol/g gel/hr) after 25 days of incubation. The immobilized methanogenic microbial population continuously evolved methane over a 90 day period. No difference in methane productivity was observed after three months of storage at 5°C. Methane was also produced by immobilized whole cells under aerobic conditions. Furthermore, carbohydrates, such as glucose, in wastewater completely decomposed by immobilized whole cells.
Studies on the immobilization of trypsin on sand
Authors: Puvanakrishnan R. , Bose S. M.
Published: December 2004

Trypsin was immobilized on sand using five different methods. Attempts were made to attach amino‐functional groups onto sand using 3‐aminopropyltriethoxysilane, hexamethylenetetramine, hexamethylenediamine, and melamine. Glutaraldehyde was used as a bifunctional agent in all the methods. Methods for the estimation of the proteolytic 1activity and protein content of immobilized trypsin were standardized. The maximum retained activity was observed for trypsin immobilized on sand via 3‐aminopropytriethoxysilane and glutaraldehyde. Immobilized trypsin showed a shift in the pH optimum toward the acidic side over that of soluble trypsin in all five cases. The optimum temperature for both native and immobilized trypsin prepared by the silane‐glutaraldehyde method was found to be 45°C. However, the pH and thermal stabilities of immobilized trypsin were observed to be better than that of the native enzyme.
Stability analysis of commensal and mutual relations with competitive assimilation in continuous mixed culture
Authors: Miura Yoshiharu , Tanaka Hiroki , Okazaki Mitsuo
Published: December 2004

The population dynamics of continuous mixed cultures with pure commensalism, commensalism plus competitive assimilation, pure mutualism, and mutualism plus competitive assimilation was disused. The population does not display oscillatory phenomena where there is a single interaction of commensalism or mutualism. Damped oscillations take place when two interactions (such commensalism and competitive assimilation or mutualism and competitive assimilation) coexist in the continuous mixed culture. The stability of these systems was discussed in detail.
Estimation of diffusion coefficients of proteins
Authors: Young M. E. , Carroad P. A. , Bell R. L.
Published: December 2004

A correlation for estimating the diffusion coefficients of protein molecules is presented. The correlation is based upon literature values of the protein diffusion coefficients and molal volumes for 143 proteins. The correlation can be used for the estimation of diffusion coefficients using only molecular weight. Accuracy is such that a linear regression on 301 proteins showed 75% of the diffusion coefficients estimated fell within 20% of the experimental values. The relationship between this correlation, the Stokes–Einstein equation, and the Wilke–Chang correlation is discussed.
Relationship between bulking and physicochemical–biological properties of activated sludges
Authors: Beccari M. , Mappelli P. , Tandoi V.
Published: December 2004

Research into bulking in laboratory‐scale activated‐sludge plants are reported upon. A correlation between sludge volume index (SVI) and biopolymer content (exocellular polymer, ECP) has been determined or sludge obtained under various operating conditions and with different chemical and physical characteristics. This paper interprets that correlation. A method for ECP determination that is quicker and just as precise as the gravimetric one and which enables this parameter to be used not only to interpret bioflocculation mechanisms but also as a parameter for evaluating optimal plant operation is reported.
Problems concerning the operation of high productivity biomass fermentations using volatile liquid hydrocarbon feedstocks
Authors: Hamer G. , Hamdan I. Y. , Khamis Alisar S. , Baroon Zainab H.
Published: December 2004

The possibilities of using liquefied petroleum gas (LPG) heavy ends, predominantly volatile liquid n‐alkanes (a location‐specific hydrocarbon feedstock) for single‐cell protein (SCP) production are examined against criteria established to define potentially attractive SCP production processes. The factors discussed include the use of the heat of vaporization for fermentor cooling, the efficiency of conversion of nalkane vapors, problems of maintaining constant composition substrates when feeding volatile liquid n‐alkane vapors to laboratory fermentors, the possible solvent effect of liquid n‐alkanes, and the possibilities of competitive inhibition. The study confirms that mixed volatile n‐alkane feedstocks will introduce major physical and biological problems for both product and process research and development. Even when the technical problems are solved, the economic question of whether a direct production route using the feedstock as the fermentation substrate or an indirect route involving the conversion of the feedstock, by chemical means, into methanol, which can then be used as the fermentation substrate, needs careful examination.
Immobilized yeast cells with methanol oxidase activity: Preparation and enzymatic properties
Authors: Couderc R. , Baratti J.
Published: December 2004

Cells form the yeast Hansenula polymorpha (ATCC 26012) were successfully immobilized by entrapment in a polyacrylamide gel. The resulting gel showed high methanol oxidase activity especially after treatment with a detergent (CTAB). The enzymatic properties of the gel‐entrapped cell were not very different from that of the soluble enzyme except that no inhibition was observed at high methanol concentration. In continuous reactors, the gel‐entrapped cells showed a much higher stability than other enzyme preparations. The inactivation mechanism was investigated and proved to be the oxidation of essential SH group(s) of the methanol oxidase molecule by hydrogen peroxide. Treatment with β‐mercaptoethanol prevented inactivation or regenerated activity.
Continuous production ofL‐isoleucine using immobilized growing Serratia marcescens cells
Authors: Wada Mitsuru , Uchida Tomofumi , Kato Jyoji , Chibata Ichiro
Published: December 2004

An immobilized growing cell system was applied to the continuous L‐isoleucine production by Serratia marcescens. In the new immobilized‐cell systems using the carrageenan gel method. S. marcescens cells in the gel required nutrients and oxygen for growth, and the numbers of living cells per milliliter of gel increased to the levels of that of free cells in the liquid medium. This immobilized growing cell system exhibited high and stable activity for isoleucine production under steady‐state conditions. Continuous isoleucine production was carried out by feeding the nutrient medium under aeration into a fluidized bed reactor containing the immobilized cells. In the continuous operation, an efficient production was maintained by automatically controlling the pH of the reaction mixture at 7.5. The productivity of isoleucine increased using multibed reactors. In a two‐bed reactor system, the effluent L‐isoleucine concentration reached 4.5 mg/ml at a retention time of 10 hr, and a steady state was maintained for longer than 30 days.
Polymethylglutamate as a new matrix for covalently immobilized enzymes: Preparation and properties of urease and uricase
Authors: Minamoto Yoshiki , Yugari Yasumi
Published: December 2004

Polymethylglutamate (PMG), a synthetic polypeptide, was used as a new carrier to immobilize urease (EC 3.5.1.5) and uricase (EC 1.7.3.3) by the azide method. The enzymes could be immobilized onto PMG in various forms, such as film, fiber, coating on various beads, and a silicon tube. The retained activities of the immobilized enzymes were excellent (more than 95%), therefore it was possible to immobilized almost all activities of the enzymes added in the coupling mixtures. Heat stabilities of the resulting immobilized enzymes were markedly improved, while the optimal pH and Km values remained almost unchanged. The urease immobilized on the PMG‐coated glass beads packed in a column, was found to retain its activity more than 80% of the initial value, even after the occasional use for a year. In view of the improved retained activities and stabilities of the immobilized enzymes, PMG may therefore be a very versatile matrix for the immobilized enzymes.
Enzymatic biosynthesis of cephalexin
Authors: Rhee D. K. , Lee S. B. , Rhee J. S. , Ryu Dewey D. Y. , Hospodka J.
Published: December 2004

The reaction kinetics of the enzymatic of cephalexin from 7‐aminodea‐cetoxy cephalosporanic acid and phenylglycine methylester was studied using the synthesizing enzyme obtained from Xanthomonas citri. The activation energy, Km value for 7‐aminodeacetoxy cephalosporanic acid and phenylglycine methylester, and Ki value for phenylglycine methylester were determined as 8.63 kcal/mol, 3.7mM, 14.5mM, and 70mM, respectively. The enzyme was found to be constitutive and susceptible to deactivation.
Structure and function of the Bacillus thuringiensis protein crystal
Authors: Nickerson Kenneth W.
Published: December 2004

The structural chemistry of the Bacillus thuringiensis parasporal protein crystal is discussed in terms of purification techniques, removal of contaminating proteases, crystal subunit size, crystal shape, interchain crosslinks, the ultimate toxin, and lysinoalanine. The alkaline pH cleavage of disulfide bonds is stressed in relationship to this role in crystal solubilization and toxin formation. The future implication s of plasmid‐coded crystal formation and B. thuringiensis var. israelensis (effective against mosquitoes and black flies) are also discussed.
Production and efficacy of baculviruses
Authors: Shieh T. R. , Bohmfalk G. T.
Published: December 2004

Several baculvirusus of nuclear polyhedrosis virus (NPV) have been produced and tested for microbial control of various Lepidoptera spp. To date, there are three registered preparations of NPV that are exempt from the requirement of tolerance by the Environmental Protection Agency (EPA) in the United States (US). The first and only commercially available viral preparation used in agriculture was developed by Sandoz, Inc. under the name of Elcar® for control of Heliothis spp. on cotton. The other two baculovirus preparations were developed and registered by the US Department of Agriculture (USDA) for control of Douglas‐fir tussock moth and gypsy moth on forests. Several methods are being used for production of NPV viruses: (1) field collection of diseased larvae, (2) laboratory rearing of insects followed by infection with viral inoculum, (3) tissue culture. and (4) tissue culture and mass rearing larvae. Recent progress in mass production of insect virus points toward the adoption of tissue culture with the whole organism technology for production of a standardized viral product. The practical usefulness of various baculovirus preparations has been demonstrated for protection of forests from defoliation by various lepidopterous species. In agriculture, Elcar® has been successfully marketed and has been very well received for use in integrated pest management on cotton. Recent development also demonstrated that use of adjuvants further increase the efficacy of Elcar® against Heliothis spp. on cotton.
Production and efficiency of protozoa
Authors: Brooks Wayne M.
Published: December 2004

Despite the chronic and debilitative nature of the infection they cause, several species of microsporidia and neogregarines offer a good potential as microbial control agents, particularly against insect pests of high economic thresholds. Techniques for mass production of protozoa have usually involved per os, inoculation or injection of the protozoa into their usual or alternate hosts. The spores are harvested subsequently from heavily infected host tissues by grinding, filtration, and differential centrifugation. Although fresh spores are used in most field tests, the spores of many species can be stored with high survival either frozen or in water at low temperatures (0–4°C) for up to several months. Sunlight or ultraviolet (UV) radiation is a serious factor limiting spore persistence. However, the protozoa do not appear to be significantly limiting spore persistence. However, the protozoa do not appears to be significantly more susceptible to UV radiation than other insect pathogens and persistence can be prolonged with UV protectants. Most field tests with protozoa have involved the application of spores in sprays and have usually resulted in a high degree of infection in the target host species. The potential for control of few species has been improved by formulation of spores in to baits, and the potential of other species will likely increase if suitable bait formulation can be devised in the future. One species, Nosema locustae, formulated as a bait, has been successfully used to control grasshoppers on rangelands. Limited laboratory and field studies have also suggested that increased short‐term control might be obtained if candidate protozoan species can be combined with certain insecticides. While recent and increased efforts have been devoted to assess the potential of protozoa as microbial control agents, potential hazards to nontarget organism have been investigated for only three species. Their close relation taxonomically to protozoa pathogenic for mammals will necessitate careful evaluation of the safety of candidate control species for nontarget organisms.
Mechanistic model of the growth of Streptococcus cremoris HP at super optimal temperatures
Authors: Franks P. A. , Hall R. J. , Linklater P. M.
Published: December 2004

The kinetic response of Streptococcus cremoris HP to growth at super optimal temperatures is reported. The response to a step increase in temperature was shown to be transient and to result from an increased metabolic rate caused by the raised temperature combined with thermal deactivation of the cell mass present. The catabolic and anabolic activities of the cell were shown to decay at different rates resulting in an accumulation of cells capable of catabolism (energy production) but unable to reproduce. The proposed mechanism was confirmed by independent estimates of the catabolic and anabolic activities of the culture. A mathematical model based on the proposed mechanism and incorporating simultaneous exponential growth, thermal death, and catabolic uncoupling of anabolically inactive cells was developed. Experimental evaluation of the model indicated the presence of a delay in deactivation of metabolic activity in response to a temperature transient. After the inclusion of this delay in death, it was confirmed that the model was capable of prediction of the balanced growth and transient response of this organism to changes in growth temperature. The delay in death was shown to be of major significance to the control of a simulated cheddar cheese fermentation.
Conversion of cellulose to glucose with cellulase of Trichoderma viride ITCC‐1433
Authors: Herr Dieter
Published: December 2004

Trichoderma viride ITCC‐1433 secretes a cellulase complex that is rich in β‐glucosidase and therefore well suited for the saccharification of cellulosic materials. The cellulase was investigated with respect to optimum conditions of reaction and enzyme stability. Avicelase, CMCase, and β‐glucosidase differed considerably in their physicochemical properties. At temperatures above 50°C, β‐glucosidase is not very stable. Therefore, as a compromise the conditions of hydrolysis were chosen to be 50°C and pH 4.5. With the crude culture filtrate of T. viride ITCC‐1433 a nearly pure glucose solution of 4% is reached from a 10% cellulose suspension. Wood pulp and newsprint are hydrolyzed to a much smaller extent. With an enzyme concentrate up to 8% glucose accumulated in the reaction fluid within 48 hr. At this time the glucose‐cellobiose ratio was 75:1. Glucose was demonstrated to be the most potent inhibitor of total hydrolysis. The addition of glucose to the enzyme‐substrate solution at zero time completely stopped its own formation and cellobiose and reducing groups (oligosaccharides) accumulated. By removing glucose through an ultrafilter device about 90% saccharification of cellulose to glucose was achieved in 48 hr without any accumulation of cellobiose.
Oxygen transfer and mycelial growth in a tubular loop fermentor
Authors: Ziegler H. , Dunn I. J. , Bourne J. R.
Published: December 2004

A 22 m long. 20 liter tubular loop fermentor (TLF) has been tested for oxygen transfer characteristics and as a reactor for mycelial growth. Model calculations show that the flow pressure drop has an important influence on the axial oxygen profiles. A design model that accounts for this influence is presented. Using the model, KLa values are calculated from the results of sulfite oxidation experiments. These are correlated with power consumption and aeration rates. The KLa dependence on aeration rate was found to be less than found with tank reactors. The growth kinetics of three metabolite‐producing mycelial organisms in the TLF are presented: a Streptomyces, a Fusarium, and a Acrophialophora. In order to determine the influence of reactor type on the growth and product formation, these cultures have been grown in tanks and shake flasks. The antibiotic, product spectrum of Streptomyces is compared on the basis of inhibition tests and it is shown that the distribution of products is reactor dependent. The Fusarium culture produced a previously unknown metabolite, whose concentration in the loop fermentor was four times higher than in a shake flask. The Acrophialophora culture grew twice as fast in the loop fermentor, but produced essentially none of the specific product. Power Consumptions of up to 8 kW/m3 in the tubular fermentor did not appear to harm the mycelia.
Study of a “bloom” of the oil‐rich alga Botryococcus braunii in the Darwin River Reservoir
Authors: Wake L. V. , Hillen L. W.
Published: December 2004

A “bloom” of the freshwater alga Botryococcus braunii Kützing appeared in the Darwin River Reservoir in 1976. At the time of algal sampling, the "bloom" was estimated at 1500 ton and possibly double this mass at a maximum cell concentration. The alga is characterized by a high liquid hydrocarbon content, sufficient to cause flotation of the algal colonies. This report is an examination of the waters of the reservoir and of the characteristics of the alga. Observations are included on the formation of a material known as Coorongite, a rubbery complex produced by the drying of colony aggregates at the shoreline. Earlier reports of “blooms” of B. braunii are reviewed in relation to this study.
Ultraviolet‐sensitive photographic process using enzymes
Authors: Kuan K. N. , Lee Y. Y. , Melius P.
Published: December 2004

A unique silver‐free and ultraviolet (UV)‐sensitive photographic process using enzymes has been developed. It utilizes α‐chymotrypsin acylated to a light‐sensitive stereoisomeric ester as the basic photographic material. When UV light is exposed to the file, the signal is registered by the appearance of melanin pigment through the chymotrypsin‐mediated activation of pre‐tyrosinase.
Bed expansion characteristics of liquid fluidized particles with attached microbial growth
Authors: Ngian Kian‐Fah , Martin William R. B.
Published: December 2004

The bed expansion behavior of liquid fluidized beds of char particles coated with attached microbial growth of denitrifying mixed bacteria was studied experimentally to obtain an expression that relates the bed expansion to the liquid velocity for liquid fluidized beds of composite particles. As for liquid beds of homogeneous spheres, the bed voidage and the liquid velocity vz for liquid fluidized beds of biomass‐coated particles were found to be related as vz/Vi = ∈n. The correlations recommended by Richardson and Zaki for homogeneous spheres are found to be satisfactory for the estimation of the constant n, but only under certain conditions for the constant Vi.
Oxygen supply to bacterial suspensions of high cell densities by hydrogen peroxide
Authors: Ibrahim M. , Schlegel H. G.
Published: December 2004

The supply of heterotrophically growing suspensions of Alcaligenes eutrophus PHB−4 with oxygen formed by the continuous addition of H2O2 in the presence of bovine liver catalase was found to be restricted to well‐defined conditions. The catalase‐H2O2 system proved to be suitable during the growth at low cell densities equivalent to 2 g dry weight/liter. When under these conditions the oxygen concentration was held constant at 1.8 mg O2/liter, the cells grew for 6–8 hr at a rate almost identical to that observed with conventional aeration. However, aeration with H2O2 for longer durations (10–20 hr) and at higher cell densities (5−20 g dry weight/liter) led invariably to cell damage and retardation of growth. The impairment of growth observed during the oxygen supply by the catalase−H2O2 system was traced back to the formation of gradually increasing steady‐state concentrations of H2O2 in the medium. Possible sites of cell damage by H2O2 such as membrane function, excretion and function of siderophores, and synthesis of cell polymers have been studied, and the cytotoxic mechanism of low concentrations of H2O2 was discussed.
Continuous conversion of sucrose to fructose and gluconic acid by immobilized yeast cell multienzyme complex
Authors: D'Souza S. F. , Nadkarni G. B.
Published: December 2004

A multienzyme complex consisting of invertase, glucose oxidase, and catalase was reconstituted by binding glucose oxidase using concanavalin A (Con A) to the cell wall of Sacchararomyces cerevisiae, previously induced for maximal activities of invertase and catalase. The cell flocculate obtained was stabilized by entrapment in polyacrylamide using γ irradiation at 100 kR. This complex showed a shortening of the lag period and enhancement in gluconic acid production as compared to a similar mixture of soluble enzymes. The efficacy of the multienzyme complex has been compared with that of mixed multienzyme system composed of individually immobilized enzymes. The immobilized multienzyme complex in a continuous‐flow stirred‐tank reactor system could be operated for continuous conversion of sucrose to fructose and gluconic acid. The reactor system did not show any loss in efficiency in a continuous operation over 20 days.