bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of ferric tartrate/sodium hydroxide solvent pretreatment on enzyme hydrolysis of cellulose in corn residue
Authors: Hamilton T. J. , Dale B. E. , Ladisch M. R. , Tsao G. T.
Published: December 2004

Lignocellulose containing 62% cellulose was prepared from corn residue by dilute acid hydrolysis using 5% H2SO4at 90°C. The lignocellulose was then treated with a cellulose solvent consisting of a ferric sodium tartrate complex in 1.5Nsodium hydroxide at levels ranging from 4:1 to 12:1 (solvent volume: corn residue lignocellulose) or a 1.5Nsodium hydroxide solution alone. Subsequent hydrolysis with cellulase enzymes fromTrichoderma reeseigave cellulose conversions which were two to three times higher than untreated lignocellulose (30%) and approached 90% conversion after 24 h in the best cases. It was found that increasing cellulase enzyme levels from 3.74 lU/g lignocellulose to 7.71 lU/g lignocellulose increased cellulose conversion by 50% at all pretreatment conditions, while an increase from 7.71 to 10.1 lU/g gave only an additional 5–10% increase. Pretreatment with sodium hydroxide resulted in 5–25% lower conversions than observed for cellulose treated with the solvent, depending on enzyme levels and treatment levels. At high enzyme levels, sodium hydroxide pretreatment is almost as effective in enhancing cellulose conversion after 24 h as is pretreatment using the cellulose solvent.
Acidogenic and methanogenic fermentation of causticized straw
Authors: Baccay Romeo A. , Hashimoto Andrew G.
Published: December 2004

The effects of pretreatment process variables [straw concentration between 20 and 90 kg volatile solids (VS)/m3, temperature between 30 and 85°C, and alkaline dosage between 0 and 80 g NaOH/kg VS] on acidogenesis and methanogenesis were investigated. Rates of acidogenesis and methanogenesis were determined using firstorder kinetics, and ultimate acid and methane yields were measured. The acid yield was not affected by pretreatment concentration or temperature, but increased as alkaline dosage increased. The acidogenesis rate was not affected by pretreatment temperature or alkaline dosage, but decreased as the substrate concentration increased. This decrease in the acidogenesis rate was attributed to a decrease in the inoculum: substrate ratio as the substrate concentration increased. The methane yield and methanogenesis rate were not affected by pretreatment substrate concentration or temperature, and both increased with alkaline dosage up to about 40 g NaOH/kg VS, then remained relatively constant above 40 g NaOH/kg VS.
Cellulose degradation and monitoring of viscosity decrease in cultures of Cellulomonas uda grown on printed newspaper
Authors: Rapp Peter , Reng Hansgeorg , Hempel Dietmar‐Christian , Wagner Fritz
Published: December 2004

The rheological behavior of cultures of Cellulomonas uda with shredded printed newspaper as the carbon source was studied. The initial substrate concentrations ranged from 23 to 60 g/L. The changes in apparent viscosity were followed on‐line by applying a commercially available process viscometer and discretely using a rotational viscometer with an anchor impeller. During the time of highest cellulose degradation, the broths exhibited a pseudoplastic behavior which could be explained satisfactorily by the power‐law model. At the end of cultivation when cellulose degradation slowed down, the broths became Newtonian in behavior. Endo‐1,4‐β‐glucanase, 1,4‐β‐xylanase, β‐glucosidase, and β‐xylosidase activities were also determined during cultivation as well as cellulose degradation and cell mass production. The beginning of endoglucanase formation and the start of the final viscosity decrease of the bacterial paper pulp suspensions could be correlated.
Enzymatic hydrolysis of cellulosic materials: A kinetic study
Authors: Beltrame Pier Luigi , Carniti Paolo , Focher Bonaventura , Marzetti Annamaria , Sarto Virginio
Published: December 2004

A kinetic study of the enzymatic hydrolysis of two celluloses with different structural features was performed at various temperatures (26–50°C). The enzymatic system consisted of three types of enzymes: E1—β‐1,4‐glucan glucanohydrolase; E2—β‐1,4‐glucan cellobiohydrolase; and E3—β‐glucosidase. A mathematical model for the mechanism of the hydrolysis of cellulosic materials catalyzed by a multienzymatic system was checked and a good rationalization of the experimental results was achieved. Uncompetitive and competitive glucose inhibition on E1 and E2, respectively, appeared to occur for both substrates. Inhibition by cellobiose was checked at 34°C on one substrate. The Vmax, Km, and glucose inhibition constants were optimized and their dependence on temperature determined.
A simple algorithm for on‐line prediction of BOD5 by a microprocessor‐based system
Authors: Raviv Roni , Ben‐Yaakov Sam
Published: December 2004

A novel algorithm for predicting BOD5 from the dissolved oxygen (DO) concentration after a relatively short incubation period is presented and evaluated experimentally. Test runs on synthetic and experimentally derived raw data suggest that BOD5 can be predicted to within 15% ca. 36 h. The method can be improved by filtering out, via a digital filter, noise from the raw data. The suggested algorithm does not require elaborate computations or large data storage and can therefore be implemented on a low‐cost microcomputer for fast on‐line determination of BOD5.
Spectral shifting by dyes to enhance algae growth
Authors: Prokop A. , Quinn M. F. , Fekri M. , Murad M. , Ahmed S. A.
Published: December 2004

The photosynthetic growth action spectrum of a green alga at three bands of visible light (blue, orange, and red) at fixed quanta input and under light‐limiting conditions was measured in a batch cultivation system. Quantum efficiencies (biomass dry weight increment per quanta absorbed) were better in the yellow–red region than in the blue region. Results served as a basis for the design and optimization of a dye system that would shift the energy of solar radiation to the required wavelength range by absorbing ultraviolet to blue radiation and emitting in the yellow–red, thus enhancing algae growth. Direct incorporation of dyes into the growth medium, although theoretically expected to enhance growth, in fact resulted in dye decomposition, toxicity to algae and consequently in growth inhibition. Indirect application of dyes in a double tubular reactor (algae inside and dye solution outside) demonstrated growth enhancement for certain dyes with high quantum yields and stability, which had suitable absorption/emission spectra for artificial light sources used. The maximum indirect growth enhancement was obtained using rhodamine 6G at a concentration of 3×10−5M with tungsten filament lamp sources.
Stimulation of hydrogen photoproduction in algae by removal of oxygen by reagents that combine reversibly with oxygen
Authors: Rosenkrans Addison M. , Krasna Alvin I.
Published: December 2004

Hydrogen photoproduction from water by Scenedesmus cells was achieved in the presence of reagents that combine reversibly with oxygen. The oxygen can be subsequently released, and H2 and O2 are obtained in the 2:1 ratio expected for H2O photolysis. This was accomplished in an experimental design which facilitates rapid transfer of gases and the use of a variety of water‐soluble and DMSO‐soluble chelates of cobalt which combine reversibly with oxygen.
The growth dynamics of a methanol‐utilizing bacterium L3 in a batch bioreactor
Authors: Agrawal Pramod , Lim Henry C.
Published: December 2004

The growth dynamics of a methanol utilizing bacterium, L3, in batch bioreactors were experimentally investigated. Formaldehyde, a key intermediate of methanol oxidation, is indicated to have a significant role in the complex batch growth behavior of L3. The intricate batch growth dynamics of many microorganisms can be elegantly characterized by examining the specific rates of exchange of nutrients and products between the cells and the cellular environment. Following such an analysis, the batch growth of L3 on methanol was characterized by the presence of unbalanced and balanced growth phases. The nature and significance of nutrient and product concentration profiles or semilog‐arithmic profiles of nutrient and product exchange rates during balanced and unbalanced growth phases are also outlined.
The impulse response of Chlamydomonas reinhardii in nitrite‐limited chemostat culture
Authors: Cunningham Alexander
Published: December 2004

This article presents a clear experimental determination of the behavior of nutrient uptake rate, mean cell nutrient content, and specific growth rate following the injection of pulses of additional limiting nutrient into a chemostat culture of Chlamydomonas reinhardii. The uptake rate per cell is a hyperbolic function of external nutrient concentration. The specific growth rate is related to the mean cell nutrient content by a hysteresis loop. The data obtained is used to test the performance of the Caperon–Droop mean cell quota model. It is demonstrated that this model cannot be used under severe transient conditions, even when modified by the introduction of a discrete time delay, a simple memory function, or time‐dependent intracellular nutrient processing.
Comparison of different strategies for the lipase‐catalyzed preparative resolution of racemic acids and alcohols: Asymmetric hydrolysis, esterification, and transesterification
Authors: Cambou Bernard , Klibanov Alexander M.
Published: December 2004

Lipase from Candida cylindracea has been found to be a highly stereospecific catalyst suitable for preparative resolution of racemic acids and alcohols. Using (R, S)−2‐(p‐chlorophenoxy) propionic acid (whose R isomer is a herbicide) and (R, S)‐sec‐butanol (a versatile synthon) as model compounds, three alternative approaches to lipase‐catalyzed resolutions—asymmetric hydrolysis, esterification, and transesterification—have been compared. Enzymatic esterification in biphasic systems has been ruled out for preparative resolutions because addition of the acids lowers the pH of the aqueous phase thereby greatly reducing the efficiency of the procedure. Both enzymatic hydrolysis and biphasic transesterification afforded resolution of the racemates on a gram scale. From the standpoint of productivity, ease of product separation, and the amount of steps required, lipasecatalyzed asymmetric hydrolysis has been judged to be superior for the practical resolution of racemic acids, and lipase‐catalyzed asymmetric transesterification to be the method of choice for the practical resolution of racemic alcohols.
The kinetics and physiology of stipitatic acid and gluconate production by carbon sufficient cultures of Penicillium stipitatum growing in continuous culture
Authors: Linton J. D. , Austin R. M. , Haugh D. E.
Published: December 2004

The yield from glucose of ammonia‐grown carbon‐limited continuous cultures of Penicillium stipitatum was ca. 20% higher than that of nitrate‐grown cultures at all growth rates examined. However, the yield from oxygen was similar during growth on both nitrogen sources. Under phosphate limitation the specific rate of gluconic acid and stipitatic acid production increased with growth rate, but the former product accounted for virtually 100% of the excreted carbon. Stipitatic acid was not produced under nitrogen limitation, and glucose supplied to the culture in excess of that required for growth was virtually quantatively converted into gluconic acid. Productivities of 11.4 g gluconic acid/L/h were stably maintained in continuous culture. Under conditions of glucose excess the enzyme glucose oxidase was excreted into the culture. The specific activity of this extracellular enzyme increased when the input glucose concentration to the culture was progressively increased. The excretion of a protein under nitrogen limitation suggests that this enzyme plays an important role under these conditions. Indeed, it was demonstrated that nitrogen‐limited cultures did not overmetabolize gluconate at either pH 6.5 or 3.5, although up to 29 g/L gluconate was present in the culture. The Ygluconate and YO2 of C‐ and N‐limited gluconate‐grown cultures were similar indicating that the rapid conversion of glucose to gluconate probably affords a means of regulating carbon flow in this organism. Nitrogen‐limited cultures of P. stipitatum overmetabolized glucose to a much greater extent than acetate, fructose, or gluconate.
Optimization of solid substrate fermentation of wheat straw
Authors: Abdullah A. L. , Tengerdy R. P. , Murphy V. G.
Published: December 2004

Optimal conditions for solid substrate fermentation of wheat straw with Chaetomium cellulolyticum in laboratory‐scale stationary layer fermenters were developed. The best pretreatment for wheat straw was ammonia freeze explosion, followed by steam treatment, alkali treatment, and simple autoclaving. The optimal fermentation conditions were 80% (w/w) moisture content; incubation temperature of 37°C; 2% (w/w) unwashed mycelial inoculum; aeration at 0.12 L/h/g; substrate thickness of 1 to 2 cm; and duration of three days. Technical parameters for this optimized fermentation were: degree of substance utilization, 27.2%; protein yield/substrate, 0.09 g; biomass yield/bioconverted substrate, 0.40 g; degree of bioconversion of total available sugars in the substrate, 60.5%; specific efficiency of bioconversion, 70.8%; and overall efficiency of biomass production from substrate, 42.7%. Mixed culturing of Candida utilis further increased biomass production by 20%. The best mode of fermentation was a semicontinuous fed‐batch fermentation where one‐half of the fermented material was removed at three‐day intervals and replaced by fresh substrate. In this mode, protein production was 20% higher than in batch mode, protein productivity was maintained over 12 days, and sporulation was prevented.
Kinetic characteristics of biochemical cyclic reaction systems: Amplification of substrate cycle system
Authors: Okamoto Masahiro , Hayashi Katsuya
Published: December 2004

The amplification of a substrate cycle system with reversible closed reaction of two substrates was represented by mathematical equations. The results are summarized as follows: the amplification was affected especially by the affinity of enzyme and substrate, by the rate constant in rate‐limiting reaction step, and by the saturation degree of enzyme by substrate. These amplifications were not simply determined by the values of Km and Vmax, because each rate parameter in the system can affect the degree of amplification independently. The conclusion is that the “apparent” equilibrium constant of this system cannot be uniquely estimated from only data of Km and Vmax even if the reaction occurs in a closed system.
A segregated model for plasmid content and product synthesis in unstable binary fission recombinant organisms
Authors: Seo Jin‐Ho , Bailey James E.
Published: December 2004

Plasmid propagation in populations of unstable, binary fission recombinant organisms has been studied using a segregated, population balance mathematical model. Segregated models have the advantage of direct incorporation of basic information on mechanisms and kinetics of plasmid replication and segregation at the single‐cell level. The distribution of cellular plasmid content and specific rates of plasmid gene expression have been obtained for several single‐cell models of plasmid replication, partition, and gene expression. Plasmid replication kinetics during cell growth significantly influence the plasmid content distribution. In the case of transient growth of plasmid‐containing and plasmid‐free cells in partially selective medium, the degree of selection required for stable maintenance of plasmid‐containing cells has been determined. Guidelines are presented for applicability of simpler, nonsegregated models and for evaluation of the parameters in these models based on single‐cell mechanisms and associated parameters.
Primary particle formation in protein precipitation
Authors: Nelson C. D. , Glatz C. E.
Published: December 2004

Recovery of proteins frequently involves a precipitation step in which ease of recovery of the solid protein depends on the size and density of the solid particles. The solid particles are actually aggregates of much smaller primary particles. In this work, possible influences on the aggregates of primary particle properties are postulated. The role of precipitation conditions during precipitation of soy protein with acid or CaCl2 is determined by measurement of zeta potential and size distribution. Results are consistent with a nucleation/growth model for determination of size. There is indirect evidence that fractionation occurs at the primary particle level, although the particles are homogeneous at the aggregate level.
Profile control scheme in a Bakers' yeast fed‐batch culture
Authors: Takamatsu Takeichiro , Shioya Suteaki , Okada Yoshiki , Kanda Masaaki
Published: December 2004

This article develops and discusses a practical and useful computer control scheme so that the biomass concentration or the specific growth rate will as accurately as possible follow a desired profile specified in advance. Many computer simulations certified the validity of the proposed control scheme. The control scheme proposed, called “programmed‐controller/feedback‐compensator (PF) system,” consists of a programmed controller that will follow the desired profile unless there is noise or disturbance and a feedback compensator that will compensate the noise and correct error in the model parameters. As the feedback compensator, the model reference adaptive control (MRAC) algorithm was also proposed. The PF system with MRAC, named PF–MRAC, could be used sufficiently for the profile control of the specific growth rate. For the profile control of the cell concentration, “predictive control algorithm” should be added to the PF system, and the consequent control scheme was named as the PFP system. Many numerical examples showed that the PFP system with MRAC, named PFP–MRAC, proposed here worked sufficiently well.
The acetone butanol fermentation on glucose and xylose. I. Regulation and kinetics in batch cultures
Authors: Fond Olivier , Engasser Jean‐Marc , Matta‐El‐Amouri Ghassam , Petitdemange Henri
Published: December 2004

The kinetics in batch culture of the acetone butanol fermentation by Clostridium acetobutylicum is compared on glucose, xylose, and mixtures of both sugars. The fastest initial growth and transition from an acid to a solvent metabolism occurs on glucose, with a final 62 g/L glucose conversion. On xylose, an initial slower growth rate and a longer metabolic transition result in higher cellular and acids concentration, thus in a level of fermented sugar limited to 47 g/L. Batch fermentations on mixtures of glucose and xylose show that both sugars can be fermented, with a higher rate for glucose. However, xylose fermentation is inducible and inhibited at glucose level above 15 g/L. Mixtures of glucose and xylose yield the highest amount of fermented sugars, up to 68 g/L, as a result of both a fast metabolic transition on glucose and a strong acid reconsumption on xylose. In all cases, solvent production is triggered at a total acid concentration between 4 and 5 g/L, whereas the final inhibition of the fermentation takes place at a total butanol and acid concentration between 18 and 20 g/L.
The release of fermentable carbohydrate from peat by steam explosion and its use in the microbial production of solvents
Authors: Forsberg Cecil W. , Schellhorn Herb E. , Gibbins L. N. , Maine Frank , Mason Eileen
Published: December 2004

Steam treatment of peat at 200°C for 3 min, followed by instantaneous decompression (steam explosion), solubilized up to 28% of the dry matter. Seventy‐five percent of the solubilized material was carbohydrate, 33% of which was composed of mono‐ and disaccharides, including galactose, glucose, xylose, mannose, arabinose, and cellobiose, in order of decreasing concentration. The solubilized materials served as the sole source of carbohydrate for growth and solvent production by Clostridium acetobutylicum and C. butylicum which utilized up to 40% of the carbohydrate. Of the saccharides in this mixture, galactose was the least readily utilized. Approximately 30% of the fermentable carbohydrate used was converted to fatty acids and solvents, with the primary fermentation product being butyrate. Clostridium thermohydrosulfuricum was able to utilize ca. 50% of the carbohydrate, and simultaneously produced slightly more than 1 mol ethanol/mol saccharide metabolized. This organism, like other strains tested, used galactose less readily than the other sugars. The residue from the steam explosion process contained 24% cellulose, but it could not serve as a source of carbohydrate for the growth of either Bacteroides succinogenes or Clostridium thermocellum, suggesting that inhibitors were released during the steam treatment.
Oxygen supply to immobilized cells: 5. Theoretical calculations and experimental data for the oxidation of glycerol by immobilized Gluconobacter oxydans cells with oxygen or p‐benzoquinone as electron acceptor
Authors: Adlercreutz Patrick
Published: December 2004

Theoretical calculations of reaction kinetics were done for one‐step reactions catalyzed by cells immobilized in spherical beads. The reactions catalyzed by free cells were assumed to obey Michaelis–Menten kinetics for a one‐substrate reaction. Both external (outside the beads) and internal (inside the beads) mass transfer of the substrate were considered for the immobilized preparations. The theoretical calculations were compared with experimental data for the oxidation of glycerol to dihydroxyacetone by Gluconobacter oxydans cells immobilized in calcium alginate gel. Glycerol was present in excess so that the reaction rate was limited by oxygen. The correlation between experimental data and theoretical calculations was quite good. The calculations showed how the overall effectiveness factor was influenced by, for example, the particle size and the cell density in the beads. In most cases the reaction rate was mainly limited by internal mass transfer of the substrate (oxygen). As shown previously, p‐benzoquinone can replace oxygen as the electron acceptor in this reaction. The same equations for reaction kinetics and mass transfer were used with p‐benzoquinone as the rate‐limiting substrate. Parameters such as diffusivity, maximal reaction rate, and K were, of course, different. In this case also, the correlation between the model and the experimental results was quite good. Much higher production rates were obtained with p‐benzoquinone as the electron acceptor compared to when oxygen was used. The reasons for this fact were that p‐benzoquinone gave a higher maximal reaction rate for free cells and the solubility of p‐benzoquinone was higher than for oxygen. Different methods of increasing the rate of microbial oxidation reactions are discussed.
Methane recovery from water hyacinth through anaerobic activated sludge process
Authors: Saraswat N. , Khanna P.
Published: December 2004

The concepts of phase separation, anaerobic activated sludge process, and alkali pretreatment have been incorporated in this investigation with the objective of developing rational and cost‐effective designs of diphasic anaerobic activated sludge systems, with and without alkali treatment, for methane recovery from water hyacinth (WH). Evaluation of process kinetics and optimization analyses of laboratory data reveal that a diphasic system with alkali treatment could be designed with an alkali pretreatment step (3.6% Na2CO3 + 2.5% Ca(OH)2 (w/w) of WH, 24 h duration) followed by an open acid phase (2.1 days HRT) and closed methane reactor with sludge recycle (5.7 days HRT, 7.7 days MCRT) for gas yield of 50 L/kg WH/d at 35–37°C. Likewise, a diphasic system without alkali treatment could be designed with an open acid phase (2 days HRT) followed by closed methane reactor with sludge recycle (3.2 days HRT, 6 days MCRT) for gas yield of 32.5 L/kg WH/d at 35–37°C. Detailed economic analyses bring forth greater cost‐efficacy of the diphasic system without alkali treatment and reveal that the advantage accrued in terms of higher gas yield is overshadowed by the cost of chemicals in the diphasic system with alkali treatment.
Mathematical model for internal pH control in immobilized enzyme particles
Authors: Liou J. K. , Rousseau I.
Published: December 2004

A mathematical model has been developed for the internal pH control in immobilized enzyme particles. This model describes the kinetics of a coupled system of two enzymes, immobilized in particles of either planar, cylindrical, or spherical shape. The enzyme kinetics are assumed to be of a mixed type, including Michaelis–Menten kinetics, uncompetitive substrate inhibition, and competitive and noncompetitive product inhibition. In a case study we have considered the enzyme combination urease and penicillin acylase, whose kinetics are coupled through the pH dependence of the kinetic parameters. The hydrolysis of urea by urease yields ammonia and carbon dioxide, whereas benzylpenicillin (Pen‐G) is converted to 6‐amino penicillanic acid and phenyl acetic acid by penicillin acylase. The production of acids by the latter enzyme will cause a decrease in pH. Because of the presence of the ammonia–carbon dioxide system, however, the pH may be kept under control. In order to obtain information about the optimum performance of this enzymatic pH controller, we have computed the effectiveness factor and the conversion in a CSTR at different enzyme loadings. The results of the computer simulations indicate that a high conversion of Pen‐G may be achieved (80–90%) at bulk pH values of about 7.5–8.
Effect of nickel on biological methane generation from a laboratory poultry waste digester
Authors: Williams C. M. , Shih J. C. H. , Spears J. W.
Published: December 2004

Nickel added in concentrations as low as 10μM significantly increased biogas production in a laboratory poultry waste digester utilizing excreta from laying hens as the organic energy source. It was shown that the initial rate of biogas production increased as early as 4 h after the addition of nickel to the laboratory cultures. Analysis of the excreta for nickel content prior to addition of exogenous NiCl2 showed appreciable amounts of nickel present. The data indicate that nickel naturally present in layer excreta is suboptimal or unavailable to the bacteria for biogas production purposes.
In situ determination of kinetic parameters for biofilms: Isolation and characterization of oligotrophic biofilms
Authors: Rittmann Bruce E. , Crawford LouAnn , Tuck Cynthia K. , Namkung Eun
Published: December 2004

This article develops and utilizes an in situ technique to estimate the Monod half‐maximum rate concentration, Ks and the maximum specific utilization rate constant, k, for biofilms. The technique employs a curve‐matching method with kinetic results from several short‐term experiments with completely mixed biofilm reactors. Use of the in situ method eliminates the two drawbacks of using conventional suspended‐growth measurements to characterize biofilm: possible alteration of cell physiology and a major investment to run the suspended‐growth tests. Results with five cultures of biofilm‐forming oligotrophs demonstrated the in situ technique and supported the hypothesis that Ks values were lower for the biofilm oligotrophs than for typical copiotrophs.
Flow and oxygen transfer in a plunging water jet system using inclined short nozzles and performance characteristics of its system in aerobic treatment of wastewater
Authors: Ohkawa Akira , Kusabiraki Daisuke , Shiokawa Yoshihiro , Sakai Nobuyuki , Fujii Michihiro
Published: December 2004

For the plunging water jet system using inclined short nozzles, the flow characteristics such as the bubble penetration depth and the gas entrainment rate, which changed depending on the jet velocity, the nozzle diameter, the jet length, and the jet angle were first evaluated in an air‐water system. A comparable investigation between our results and those of existing studies used the long nozzles on those characteristics revealed that both the bubble penetration depth and the gas entrainment rate differed depending on the nozzle length; that is, the nozzle‐length‐to‐diameter ratio LN/DN and that of these characteristics the gas entrainment rate affected considerably by its magnitude and tended to be high when the nozzle of a large LN/DN ratio was used. It was also confirmed from the oxygen transfer experiments that the transfer efficiency at low jet velocities in the present water jet system was not inferior to the ones of other types of existing aeration systems; that is, the utilization of this jet aeration system to a high rate reactor for wastewater treatment or fermentation was sufficiently possible. The applicability of the plunging jet aeration method to microbial processes was then examined. As a typical example of microbial processes to be tested, the continuous treatment of an organic wastewater using activated sludge microorganisms was carried out, and the performance and related problem when this type of aeration system was applied to such a microbial process were investigated. Experimental results showed that, when viewed from the removal ability of dissolved organic matters, the plunging jet aeration system was capable of treating a wastewater of considerable high loading without the rate of oxygen transfer becoming the biooxydation‐rate‐limiting factor. Special attention was necessary for the choice of the liquid pump to be employed, however, due to the increased amount of fine suspended solids in the treated water caused by the shearing action between sludge flocks and pump blades.
Biodehalogenation of bromotrichloromethane and 1,2‐dibromo‐3‐chloropropane by Pseudomonas putida PpG‐786
Authors: Lam Tinyin , Vilker Vincent L.
Published: December 2004

Biodehalogenation of 10−5 M concentrations of bromotrichloromethane (BTM) and 1,2‐dibromo‐3‐chloropropane (DBCP) was studied in static cultures of Pseudomonas putida PpG‐786. The experimental cultures were prepared by growing P. putida on camphor, which is known to induce the synthesis of high concentrations of cytochrome P‐450 in this bacterium. Measurements of bromide ion release were found to be approximately consistent with the amounts of halocarbon degraded. Gas chromatography/elctron capture detection (GC/ECD) measurements of hydrocarbon degradation products as a function of incubation time showed the transitory appearance of chloroform and bromodichloromethane from BTM and the transitory appearance of lower boiling but unidentified products from DBCP. The degradation of BTM to trihalomethanes and the halide ion is consistent with the enzymatic reductive dehalogenation by cytochrome P‐450 reported by others. The dependence of initial conversion rates on halocarbon concentration (0.1–2 ppm) and cell mass concentration (1–28 g cell/L) was determined by measuring the decline of parent halocarbon in stirred batch cell suspensions. The rate of DBCP conversion was up to 10‐fold higher than the rate of BTM conversion. When the intracellular, enzyme‐catalyzed conversion BTM is analyzed by the effectiveness factor of heterogeneous catalysis, the initial conversion rates measured suggest that intrinsic enzyme kinetics, rather than halocarbon permeation of the cell membrane or other diffusive processes, is rate limiting.
Fractionation of Aspergillus niger cellulases by combined ion exchange affinity chromatography
Authors: Boyer R. F. , Allen T. L. , Dykema P. A.
Published: December 2004

Eight chemically modified cellulose supports were tested for their ability to absorb components of the Aspergillus niger cellulase system. At least two of the most effective adsorbents, aminoethyl cellulose and carboxymethyl cellulose, were shown to be useful for the fractionation of cellulases. These supports apparently owe their resolving capacity to both ion exchange and biospecific binding effects; however, the relative importance of each effect is unknown. These observations form the basis for a new cellulase fractionation technique, combined ion exchange–affinity chromatography.
Evaluation of bisubstrate secondary utilization kinetics by biofilms
Authors: Namkung Eun , Rittmann Bruce E.
Published: December 2004

A bisubstrate system having Ss1 > Smin 1 was tested with phenol and acetate as model compounds in completely mixed biofilm reactors. Two series of experiments compared the kinetics of phenol removal as a single substrate and as part of a bisubstrate system having a fixed total feed COD. Experimental results showed that, although the rate of utilization of either substrate was almost the same in a bisubstrate system as in a single substrate system, the utilization rate of either compound always was slightly greater in a bisubstrate system than in a single‐substrate system. This slight enhanced removal of an individual compound in a bisubstrate system was attributed to the extra biomass accumulated from the utilization of the other substrate. As the fraction of the feed COD contributed by an individual compound decreased in a bisubstrate system, the effluent concentration of that compound decreased and its fractional removal efficiency increased. The bisubstrate secondary‐utilization model successfully described the experimental results and explained the differences that occurred as phenol became a smaller fraction of the fixed total feed COD.
Adsorption of enzymes on krill chitin modified with carbon disulfide
Authors: Synowiecki Józef , Sikorska‐Siondalska Anna , El‐Bedawey Abo El‐Fath
Published: December 2004

Krill chitin modified with carbon disulfide was used as a support of enzymes. The dithiocarbamino groups created after reaction of CS2 with chitinous NH2 can participate in binding the enzymes without denaturation and loss in activity. The stability of these bonds depends on pH and decreases gradually at ionic strengths higher than 0.01. Chitin modified with CS2 can be used as a support for enzymes having high activity at mild conditions of pH and ionic strength.
Biomass and lipids from lactose or whey by Trichosporon beigelii
Authors: Tahoun M. K. , El‐Merheb Z. , Salam A. , Youssef A.
Published: December 2004

The yeast Trichosporon beigelii produced the highest amount of biomass when grown in chemical‐defined medium with a ratio of carbon source to nitrogen source of 30:1. On the other hand, carbon‐limited medium (C–N ratio 2:1) enhanced unsaturated fatty acids synthesis. The yeast efficiently converted unsalted whey lactose to biomass, while sodium chloride in whey raised lactose assimilation to single‐cell oil (SCO).
The effect of medium composition on the acetone–butanol fermentation in continuous culture
Authors: McNeil B. , Kristiansen B.
Published: December 2004

The effects of growing Clostridium acetobutylicum NCIB 8052 in a chemostat under conditions of glucose, NH, PO, Mg2+, and Fe2+ limitation were examined. It was noted that limitation of any major nutrient resulted in the same fermentation pattern. Conditions where minor nutrient levels were reduced appeared to stimulate solvent production. Under conditions of Mg2+ restriction, a productive solventogenic culture was produced, with a yield of total solvents on glucose of 35.5%.
Low‐pressure airlift fermenter for single cell protein production: II. Continuous culture of pichia yeast
Authors: Chen N. Y. , Srinivasan S. , Leavitt R. I. , Coty V. F. , Kondis E. F.
Published: December 2004

Experiments using Pichia yeast grown on n‐paraffins have been conducted in laboratory 10‐L airlift fermenters and in a 640‐L module of commercial scale. Results confirmed the design concept of combining oxygen transfer and fermenter cooling with low‐pressure air. However, in the absence of mass transport constraints, the build up of toxic factors in the fermenter appeared to be a major variable limiting cell productivity. Foaming in the large fermenter also presented a serious problem, which must be solved before low‐pressure airlift fermenters become practical.
Analysis of continuous cultures of recombinant methylotrophs
Authors: Parulekar Satish J. , Chang Yong K. , Modak Jayant M. , Lim Henry C.
Published: December 2004

Static and dynamic characteristics of continuous cultures of recombinant methylotrophs, which are designed to improve the selectivity of plasmid‐bearing cells and the plasmid stability, are investigated in detail. Operational regions in which coexistence (survival of plasmid‐bearing and plasmid‐free cells) operation is feasible have been identified in the entire space of kinetic parameters and operating variables. The stability characteristics of each steady state are examined. The existence of oscillatory states around the coexistence steady state is investigated using the dynamic (Hopf) bifurcation analysis. For proper startup of the continuous culture operation, it is critical to identify the sets of initial conditions, if any, which lead to transients that ultimately result in washout of plasmid‐bearing cells and avoid such conditions. For the numerical illustrations presented, the coexistence steady state happens to be locally stable over much of its region of existence, particular for the operating conditions corresponding to maximum productivity.
Suppression of pyritic sulphur during flotation tests using the bacterium Thiobacillus ferrooxidans
Authors: Townsley C. C. , Atkins A. S. , Davis A. J.
Published: December 2004

Environmental concern about sulphur dioxide emissions has led to the examination of the possibility of removing pyritic sulphur from coal prior to combustion during froth flotation, a routine method for coal cleaning at the pit‐head. The bacterium Thiobacillus ferrooxidans was effective in leaching 80% and 63% −53 μm pyrite at 2% and 6% pulp density in shake flasks in 240 and 340 h, respectively.

The natural floatability of pyrite was significantly reduced in the Hallimond tube following 2.5 min of conditioning in membrane‐filtered bacterial liquor prior to flotation. The suppression effect was greatly enhanced in the presence of Thiobacillus ferrooxidans. A bacterial suspension in pH 2.0 distilled water showed 85% suppression, whereas in spent growth liquor this value was 95%. The optimum bacterial density was 3.25 × 1010 cells/g pyrite in 230‐ml distilled water (2% pulp density) in the Hallimond tube. The degree of suppression by the cells was related to particle size but not to pH or temperature. The sulphur content of a synthetic coal/pyrite mixture was reduced from 10.9 to 2.1% by flotation after bacterial preconditioning. It is postulated that pyrite removal in coals which are cleaned by froth flotation could be significantly reduced using a bacterial preconditioning stage with a short residence time of 2.5 min.
Effect of activation energy microheterogeneity on first‐order enzyme deactivation
Authors: Malhotra Arun , Sadana Ajit
Published: December 2004

The influence of microheterogeneity on enzyme inactivation kinetics is examined. A continuous normal distribution of the thermal activation energy is assumed, and using this, a simple mathematical model is developed to find the activity–time trajectories for a microheterogeneous enzyme. Using an example, the model is used to show the quantitative effects of microheterogeneity such as increased order and stability observed during an enzyme inactivation. Experimental measurement of the extent of microheterogeneity in an enzyme sample is also discussed.
Continuous assay of neuraminidase activity by a bienzyme system immobilized in an artificial membrane
Authors: Kolisis Fragiskos N. , Thomas Daniel
Published: December 2004

Lactate dehydrogenase and NANA‐lyase were immobilized in an artificial gelantine membrane. This bienzyme system was used for continuous assay of neuraminidase activity. The K′m of the active membrane for lactate dehydrogenase and NANA‐lyase using NADH, pyruvic acid, and N‐acetylneuraminic acid as substrates were found to be 0.25mM, 0.75mM, and 2.1mM, respectively. The Km of soluble neuraminidase using sialyllactose as substrate was found to be 0.13 mM. The pH optimum for neuraminidase activity was 6.0. At 45°C the reaction rate was higher, and no denaturation phenomena of the immobolized enzymes have been observed. This bienzyme membrane was stable for several weeks stored in the reaction buffer at 4°C.
Novel anaerobic gas‐lift reactor (AGLR) with retention of biomass: Start‐up routine and establishment of hold up
Authors: Beeftink H. H. , van den Heuvel J. C.
Published: December 2004

A start‐up routine for a novel type of anaerobic gas‐lift reactor using sand as support particles for Bacterial adhesion and involving a dilution rate shift‐up is shown to result in rapid formation of mixed‐culture aggregates from freely suspended cells. Formation of aggregates changed the general metabolism from acetate–butyrate production to acetate–propionate production. This change is attributed to a selection by washout, favoring propionate‐producing bacteria with superior adhesive properties. Sand is shown to be essential in establishing, but not in sustaining, elevated holdup ratios. The importance of maintenance processes and cellular lysis in deeper parts of aggregates are manifest from a reduced effluent biomass concentration and a pronounced production of valeric acid.
Enzymatic hydrolysis of beer brewers' spent grain and the influence of pretreatments
Authors: Beldman G. , Hennekam J. , Voragen A. G. J.
Published: December 2004

The enzymatic saccharification of plant material has been shown to be of interest in various fields, such as the production of fruit juices1,2 and the utilization of biomass.3 A combination of cellulase, pectinase, and hemicellulases is usually used because of the chemical composition of the matrix of plant cell walls.

For apples, beet pulp, and potato fiber, almost a complete hydrolysis of polysaccharides is obtained by combining cellulose and pectinase. For nonparenchymatic tissue, the situation is somewhat different: pectin is a minor component and the hemicellulose content is much higher. Enzyme action is restricted by the lignin barrier and by the high crystallianity of cellulose in this material. For such materials, mechanical, thermal, or chemical pretreatments are necessary to achieve hydrolysis.4,5

This communication describes various enzymatic treatements and chemical and physical pretreatemtn, using brewers' spent grain as substrate. Spent grain is the residue of malt and grain which remains in the mash‐kettle after the liquefied and saccharified starch has been removed by filtration.
Affinity liquid‐liquid extraction of lactate dehydrogenase on a large scale
Authors: Tjerneld Folke , Johansson Göte , Joelsson Monica
Published: December 2004

Rapid liquid‐liquid extraction of lactate dehydrogenase from muscle by using a low‐cost aqueous bipolymer two‐phase system was achieved by using a centrifugal separator. Extraction of the target enzyme into the upper phase was enhanced by including the dye Procion yellow HE‐3G (bound to polyethylene glycol). The dye acted as an affinity ligand for the enzyme. The isolation of the enzyme was carried out either by using a cell extract or by homogenizing the muscle directly in the system. The latter approach reduced the preparation time with a factor of 0.25. The two methods gave, respectively, 310 and 360 kU lactate dehydrogenase/kg muscle (measured at 22°C). By using a small centrifugal separator, Alfa Laval LAPX 202, 3–5 kg muscle could be processed/h in a 30‐L, two‐phase system.
Effect of culture phasing and a polysaccharide on production of xylanase by mixed culture of trichoderma reesei D1‐6 and aspergillus wentii Pt 2804
Authors: Panda T. , Bisaria V. S. , Ghose T. K.
Published: December 2004

A significant increase in extracellular xylanase activity was observed in the mixed culture fermentation of Trichoderma reesei D1‐6 and Aspergillus wentii Pt 2804 when A. wentii inoculation was phased by 15 h. A. wentii produced a polysaccharide, chiefly consisting of glucose monomeric units, which was required for expression of maximum xylanase activity. Expression of high activity of xylanase in the A. wentii phased mixed culture compared to that in either T. reesei or A. wentii single cultures appeared to be controlled by the combined action of a polysaccharide produced by A. wentii and the relative growth of the two fungi in the mixed culture.
Oxidation of an inhibitory substrate by washed cells (oxidation of phenol by Pseudomonas putida)
Authors: Sokol W.
Published: December 2004

The specific uptake rate of phenol by washed cells of Pseudomonas putida grown on phenol in steady‐state continuous culture at various dilution rates was studied. The Monod‐Haldane‐type equation was applied to fit the data and the best kinetic parameters were determined by nonlinear least‐squares techniques. The values of the kinetic parameters were found to increase monotonically with the phenol concentration in the original chemostat. The relations between the values of kinetic parameters and phenol concentration in the chemostat were described by empirical equations. Then the equation governing the instant uptake of phenol by microorganisms in chemostat in the high conversion range of phenol was proposed. This equation together with the mass balance equations can be used to determine the stability range of continuous stirred tank biochemical reactors (CSTBR) utilizing phenol.
Evaluation of half‐life of immobilized enzyme during continuous reaction in bioreactors: A theoretical study
Authors: Yamane Tsuneo , Sirirote Pramote , Shimizu Shoichi
Published: December 2004

A theoretical study has been carried out on the evaluation of the apparent half‐life of immobilized enzyme activity during continuous reaction both in a plug‐flow reactor (PFR) and in a continuous‐flow stirred‐tank reactor (CSTR). Two apparent half‐lives have been defined: the elapsed time at which the feedrate becomes half of the initial one when the feedrate of the substrate solution is lowered to keep the conversion fixed (constant‐conversion policy), and the elapsed time at which the conversion becomes half of the initial one when the feedrate (or space velocity) is kept constant (constant‐feedrate policy or constant‐space‐velocity policy). Under no intraparticle diffusional limitation, the constant‐conversion policy of operation in the PFR and CSTR gives the same half‐life as that of the enzyme inactivation regardless of the formula of the reaction rate, and the constant‐feedrate policy of operation in the PFR and CSTR offers the same half‐life as that of the enzyme inactivation only when the reaction is zero‐order. Under intra‐particle diffusional limitation, apparent half‐lives are always greater than that of enzyme denaturation, depending on many factors such as order of reaction, feeding policy (constant‐conversion and constant‐feedrate policies), initial conversion, and bioreactor configuration. It is suggested to perform the continuous operation with changing feedrate to keep the conversion (or outlet substrate concentration) fixed under the domain of zero‐order kinetics so as to obtain an apparent half‐life as close to the real one in industrial operation.
Formation of oligosaccharides during enzymatic lactose: Part I: State of art
Authors: Prenosil J. E. , Stuker E. , Bourne J. R.
Published: December 2004

Enzymatic lactose hydrolysis by β‐galactosidase (lactase) was investigated with respect to the formation of oligosaccharides. An analysis of the formation of oligosaccharides and their control is important in the development of technical applications for enzymatic lactose hydrolysis. The available literature data on transfer reactions of lactase were reviewed, compared, and presented in a concise tabular form. Mechanisms and possible ways of modelling enzymatic lactose hydrolysis, including formation of oligosaccharides, are presented.