bluuebunny/crossref_metadata_2025 huggingface dataset:
Ethanol production from Jerusalem artichoke tubers (Helianthus tuberosus) using Kluyveromyces marxianus and Saccharomyces rosei
Authors: Margaritis Argyrios , Bajpai Pratima
Published: December 2004

This article examines the potential of Jerusalem artichoke as a source for ethanol and single‐cell protein SCP. In addition, experimental results are presented on batch fermentation kinetics employing two strains of Kluyveromyces marxianus and one strain of Saccharomyces rosei grown on the extract derived from the tubers of Jerusalem artichoke. Of the three cultures examined, Kluyveromyces marxianus UCD (FST) 55–82 was found to be the best producer of ethanol grown in a simple medium at 35°C. The ethanol production was found to be growth‐associated having a μmax = 0.41. h−1 and the ethanol and biomass yields were determined to be Yp/s = 0.45 (88% of the theoretical) and Yx/s = 0.04 with 92% of the original sugars utilized. On the basis of carbohydrate yields of Jerusalem artichoke reported in the literature and these batch kinetic studies with K. maxxianus, the calculated ethanol yields were found to range from 1400 kg ethanol acre −1 yr−1to a maximum of 2700 kg ethanol acre −1 yr−1. The SCP yields for K. marxianus were calculated to range between 130 to 250 kg dry wt cell acre −1 yr−1. The potential for developing an integrated process to produce ethanol and SCP is also discussed.
The effects of temperature, inlet pollutant concentration, and microorganism concentration on the rate of aerobic biological treatment
Authors: Vavilin V. A.
Published: December 2004

Systematic errors obtained in using traditional models of aerobic waste treatment processes are discussed. These errors are observed to arise due to the lack of matching of traditional models to experimental data in the case of broad variations of process parameters, for instance, organic loading. It is shown that the generalized models of waste treatment proposed earlier by the author permit these errors to be eliminated.
Cellulase production from immobilized growing cell composites prepared by radiation polymerization
Authors: Kumakura Minoru , Kaetsu Isao , Nisizawa Kazutosi
Published: December 2004

The cellulase production from immobilized Trichoderma reesei composites prepared by radiation polymerization at low temperature was studied. The production of cellulase from the cells irradiated by radiation was slightly retarded at the initial stage of the culture, but was immediately recovered. The production of cellulase resulting from the growth of the immobilized cells proceeds efficiently in the composite having a porous polymer matrix, in which the productivity of cellulase varied with the hydrophilicity, the shape of the composite, monomer, and cell concentration. It was found that cellulase produced by immobilized growing cell composites effectively hydrolyzed cellulosic wastes such as newspaper and chaff which are pretreated by irradiation and crushing.
A kinetic model for the hydrolysis and synthesis of maltose, isomaltose, and maltotriose by glucoamylase
Authors: Beschkov V. , Marc A. , Engasser J. M.
Published: December 2004

Kinetic results on the glucomylase‐catalysed hydrolysis of maltose and maltotriose, and glucose polymerization into maltose and isomaltose up to 450 g/L total sugar concentration are presented. Whereas the enzyme has a faster hydrolytic and synthetic activity on α‐(1→4) than on α‐(1→6) linkages, at equilibrium, on the contrary, the isomaltose level which represents 15% (w/w) of the total sugar concentration at the highest investigated concentrations is much higher than the corresponding maltose level. Under a wide range of initial conditions, experimental results are adequately described by a new kinetic model with simple first‐ and second‐order, or Michaelian‐type, rate expressions for the reversible hydrolysis of maltotriose, maltose, and isomaltose. The model also accounts for the inhibition of hydrolysis by glucose, but does not consider the concentration of water which, under the present conditions, was not found kinetically limiting.
The development of an immobilized lactate oxidase system for lactic acid analysis
Authors: Cannon John J. , Chen Li‐Fu , Flickinger Michael C. , Tsao George T.
Published: December 2004

An enzyme designated as lactate oxidase was purified from Acetobacter peroxydans by using the partition methods of separation. A DE‐52 cellulose column was used for the primary purification of lactate oxidase, and the purified enzyme was covalently bound to a porous cellulose bead matrix in which benzoquinone was used as the coupling reagent. The physicochemical properties of the native and immobilized enzymes were determined including molecular weight, cofactor requirements, and optimal reaction conditions. Lactate oxidase was shown not to be subject to product inhibition, and to require Mg2+ as a metal cofactor. Analysis of an immobilized lactate oxidase packed‐bed reactor indicated that this system may not be subject to internal diffusional limitations. Molecular oxygen appeared to be a cosubstrate of the enzyme, and a reaction mechanism was postulated to predict the kinetic behavior of the immobilized reactor system. Applications of the immobilized lactate oxidase reactor for the pulse‐flow analysis of lactic acid in whole milk and in a yeast fermentation system were considered.
Characterization of heterogeneous immobilized enzyme subpopulations using EPR spectroscopy
Authors: Clark Douglas S. , Bailey James E.
Published: December 2004

Direct evidence was obtained for the existence of two distinct forms of active α‐chymotrypsin immobilized on CNBr‐activated Sepharose 4B. Electron paramagnetic resonance (EPR) spectra of five different spin‐labeled immobilized enzyme formulations in the presence of indole were all resolved into the same two spectral components. Both subpopulation spectra were approximately identified experimentally, and the subpopulation exhibiting greatly restricted spin‐label motion was shown also to be relatively inaccessible to solvent. Using overall specific activity data and subpopulation fractions from EPR spectral analysis, the specific activity of the more constricted immobilized enzyme active form was shown to be approximately 15 times smaller than that of the other class of immobilized enzyme molecules with an indole EPR spectrum similar to that of chymotrypsin in solution. Variations in overall specific activity of formulations with different loadings and different supports results entirely from changes in the proportions of the same two subpopulations of immobilized enzyme molecules.
A kinetic model for methanogenesis of acetic acid in a multireactor system
Authors: Bhadra Amit , Mukhopadhyay S. N. , Ghose T. K.
Published: December 2004

Bioconversion of acetic acid to methane by a crude culture of methanogens in a continuous multireactor system was investigated. Culture of methanogens was drawn from an active cow‐dung digester (12 days) and was grown in a semisynthetic medium (pH 6.3, 37°C) with acetic acid as the sole carbon source. The solubilities of CO2, HCO3−, and CO32− increased with the rise in pH and exercised considerable influence on the gas composition. Various mechanisms for methanogenesis of acetic acid based on the available pathways were considered. Experimental data were compared with these mechanisms, the best fit was determined, and the corresponding rate expression was identified. This mechanism predicted that, of the total methane produced, 72%;comes from acetic acid directly and 28%;via the CO2 reduction route.
Bioengineering of photosynthetic membranes. Requirement of magnesium for the conversion of chlorophyllide a to chlorophyll a during the greening of etiochloroplasts in vitro
Authors: Daniell Henry , Rebeiz Constantin A.
Published: December 2004

The massive conversion of δ‐aminolevulinic acid (ALA) to protochlorophyllide (Pchlide) and the massive conversion of chlorophyllide a (Chlide a) to chlorophyll a (Chl a) are two essential conditions for the ALA‐dependent assembly of photosynthetic membranes in vitro. In this work, we describe the development of a cell‐free system capable of the forementioned biosynthetic activities at rates higher than in vivo, for the first 2 h of dark‐incubation. The cell‐free system consisted of (1) etiochloroplasts prepared from kinetin and gibberellic‐acid‐pretreated cucumber cotyledons, and (2) cofactors and additives described elsewhere and which are needed for the massive conversion of ALA to Pchlide, (3) high concentrations of ATP, MgCl2, and an isoprenol alcohol such as phytol, were required for the massive conversion of Chlide a to Chl a. An absolute and novel requirement of Mg2+ for the conversion of Chlide a to Chl a was also demonstrated. In addition to the role of phytol as a substrate for the conversion of Chlide a to Chl a, the data suggested that this alcohol may also be involved in the regulation of the reactions between ALA and Pchlide. It is proposed that during greening, the conversion of Chlide a to Chl a may follow different biosynthetic rates, having different substrate and cofactor requirements, depending on the stage of plastid development.
Plasmid stability in budding yeast populations: Steady‐state growth with selection pressure
Authors: Hjortso Martin A. , Bailey James E.
Published: December 2004

Plasmid gene product accumulation in a cell population depends on the fraction of plasmid‐containing cells and the distribution of single‐cell plasmid content. These important population properties have been related to plasmid replication regulation and kinetics and to plasmid segregation rules at the single‐cell level using population balance mathematical models. Budding yeast populations are considered in detail because of the practical potential of yeast host–vector systems and because of the model complications introduced by the asymmetric division pattern observed for Saccharomyces cerevisiae at all but the largest growth rates. Solutions are presented for several different reasonable models of plasmid replication and segregation. The results offer potential for identification of important qualitative features of yeast plasmid replication and of model parameter values from average and segregated experimental data on yeast populations.
Enzymatic hydrolysis of sodium‐hydroxide‐pretreated sallow in an ultrafiltration membrane reactor
Authors: Ohlson Ingrid , Trägårdh Gun , Hahn‐Hägerdal Bärbel
Published: December 2004

An ultrafiltration membrane reactor was used to investigate the recovery of biocatalysts during enzymatic hydrolysis of pretreated sallow. Product inhibition could be eliminated by continuous removal of products through the ultrafiltration membrane, thus retaining the macromolecular substrate and enzymes. In this way, the degree of conversion was improved from 40% in a batch hydrolysis to 95% (within 20 h), and the initial hydrolysis rate was increased up to seven times. The recovery studies were focused on mechanical deactivation and irreversible adsorption on to the nonconvertible fraction of the substrate. Cellulase deactivation during mechanical agitation was not significant, and the loss of activity was attributed mainly to strong adsorption of the enzymes onto undigested material. This process was studied in semicontinuous hydrolyses, where fresh substrate was added intermittently. The amount of reducing sugars produced in this experiment was 25.7 g/g enzyme, compared to 4.7 g/g enzyme in a batch hydrolysis.
Invertase covalent grafting onto corn stover
Authors: Monsan P. , Combes D. , Alemzadeh I.
Published: December 2004

The covalent coupling of an invertase from baker's yeast onto an agricultural by‐product, corn grits, has been developed. The optimal conditions for each step of the chemical modification of the support have been determined: oxidation with sodium metaperiodate, amination with ethylenediamine, reduction with sodium cyanoborohydride, and activation with glutaraldehyde. Activities up to 7.2 × 104 μmol reducing sugars produced/min g support could thus be achieved. Invertase coupling onto corn grits yields a derivative with a 25 times higher activity than when coupling this enzyme onto porous silica. The operational stability of invertase immobilized onto corn stover was found to be very high, with a half‐life of up to 365 days at 40°C when using a 2M sucrose solution as substrate. This immobilization method could be easily scaled up to the preparation of 10 kg of invertase derivative.
DNA immobilized onto an acyl‐azide derivative of collagen membranes for use as immunoadsorbent
Authors: El Habib Raphaelle , Coulet Pierre R. , Sanhadji Kamel , Gautheron Danielle C. , Laville Maurice , Traeger J.
Published: December 2004

Single‐ and double‐stranded DNA were immobilized on films of highly polymerized collagen by a covalent process. The coupling was efficient at an acidic pH with an optimum at pH 5, while preventing the collagen film from any damage. In addition, no leakage occurred, so it was possible to use this DNA‐coated collagen film as an immunoadsorbent. Therefore the findings reported here suggest that the acyl‐azide procedure is also suitable for DNA binding on a proteinic support. Promising results in specific clearance of DNA antibodies were obtained in vitro.
Microbial oxidation of dibenzothiophene by the thermophilic organism Sulfolobus acidocaldarius
Authors: Kargi Fikret , Robinson James M.
Published: December 2004

The refractory organic sulfur compound dibenzothiophene (DBT) has been oxidized by the thermophilic, sulfur oxidizing organism Sulfolobus acidocaldarius. Sulfate ions were released into the medium as the oxidation product. The kinetics of this oxidation have been investigated on the basis of sulfate released as a result of oxidation. Dibenzothiophene was found to be inhibitory to the organisms for initial concentrations over 500 mg/L. The organism may prove to be capable of oxidizing thiophene compounds present in oil refinery wastewater, coal, and crude oil.
Mechanisms for the acoustic conditioning of protein precipitates to improve their separation by centrifugation
Authors: Bell D. J. , Dunnill P.
Published: December 2004

A theoretical description of a low‐frequency, dual‐source acoustic treatment of protein precipitates is presented. Two mechanisms for the potential improvement of the centrifugal separation of precipitates are proposed. They are acoustic aggregation, which causes an increase in particle size, and aggregate deformation, which results in an increase in aggregate density. Experiments with isoelectric soya protein precipitate indicated that the extent of ageing prior to acoustic conditioning is important. Support for both aggregation and dewatering was found and a maximum increases in the particle settling velocity of 20% was observed.
The influence of fluid mixing upon respiratory patterns for extended growth of a methylotroph in an air‐lift fermenter
Authors: Fields Peter R. , Slater Nigel K. H.
Published: December 2004

The influence of methanol dispersion and fluid mixing upon respiratory patterns observed during unlimited fedbatch growth of the methylotrophic bacterium Methylophilus methylotrophus has been investigated. A concentric tube air‐lift fermenter was employed for which the mixing and fluid circulation patterns have been well characterized. Respiratory quotients showed a marked dependence upon the position in the vessel at which methanol was injected, the volumetric rate of such methanol addition, the fluid circulation time, and the local mixing behavior; the latter two factors of which are both determined by the air throughput. Such variations are discussed on the basis of simple mixing concepts and observations of fluid dispersion.
Improved biocatalyst effectiveness by controlled immobilization of enzymes
Authors: Borchert A. , Buchholz K.
Published: December 2004

Nonuniform enzyme distributions can be obtained by kinetic control of the immobilization process. Such heterogeneous biocatalysts exhibit higher effectiveness compared to conventional immobilization procedures, when the mass transfer of substrates or products is limiting. Model calculations provide some insight into the relative weight of the immobilization parameters with respect to optimal control of the enzyme distribution. Experimental results and model calculations show that considerably improved effectiveness of biocatalysts can be obtained. The role of external mass transfer is emphasized.
Ethanol fermentation in a continuous tower fermentor
Authors: Jones Stephen T. , Korus Roger A. , Admassu Wudneh , Heimsch Richard C.
Published: December 2004

A mutant of Saccharomyces cerevisiae, which forms large, multicellular flocs in liquid culture, rapidly fermented media containing high concentrations of glucose (100–180 g/L) in a continuous nonaerated tower fermentor at 30°C. The fermentor operated continuously for seven months. Batch and tower fermentor data were fitted to a kinetic model incorporating linear ethanol inhibition and Monod dependence on glucose. Conversion, ethanol yield, and ethanol productivity were related to the apparent fermentation time for initial glucose concentrations of 130 and 180 g/L. Productivities of 8–12 g ethanol/L h were achieved through the yeast bed giving conversions exceeding 90% of the theoretical yield.
Continuous growth kinetics of Candida utilis in pineapple cannery effluent
Authors: Prior B. A.
Published: December 2004

Candida utilis was grown on a pineapple cannery effluent as the sole carbon and energy source in a chemostat at dilution rates between 0.10 and 0.62 h−1 to determine the growth kinetics. The principal sugars in the effluent were sucrose, glucose, and fructose. The cell yield coefficient on carbohydrate varied with dilution rate and a maximum value of 0.63 was observed at a dilution rate of 0.33 h−1. The steady‐state concentrations of carbohydrate, reducing sugar, and chemical oxygen demand (COD) appeared to follow Monod saturation kinetics with increasing dilution rate, although none of the measured parameters represented a pure substrate. The maximum specific growth rate and reducing sugar saturation constant were 0.64 h−1 and 0.060 g/L, respectively. A maximum cell mass productivity of 2.3 g/L h was observed at a dilution rate of 0.51 h−1. At this dilution rate, only 68% of the COD was removed. A 95% COD removal was attained at a dilution rate of 0.10 h−1. Optimal yeast productivity and COD reduction occurred at a dilution rate of 0.33 h−1.
Pilot‐and production‐scale containment of cytotoxic and oncogenic fermentation processes
Authors: Flickinger M. C. , Sansone E. B.
Published: December 2004

Proper design of fermentation facilities and equipment modification can control the risks associated with largescale production and purification of microbially produced cytotoxic agents and oncogenic viruses. The primary biohazard risks to operators and the environment are generation of aerosols and accidental spills. Fermentation and recovery facilities can be constructed to contain these agents by installing fermentation equipment within a HEPA‐filter‐exhausted biological barrier. Within this barrier system, large‐scale processing that generates potentially hazaradous areosols (filtration, centrifugation of transformed cells or crystal slurries, and banding of viruses) should be isolated from other operations. Isolation of equipment is often required, with provision for both chemical and biological decontamination of process wastes. Failsafe fermentor over‐pressure sensors, parallel exhaust gas filtration, welded transfer lines, and modified sampling systems for elimination of aerosols can be installed on most fermentation equipment. Aerosol and spill containment by proper equipment design, coupled with appropriate personnel protective equipment and medical monitoring, make possible safe production of experimental growth factors and viruses from large‐scale culture of transformed mammalian cells and production of cytotoxic antitumor antibiotics.
A comparison of two empirical models for the enzymatic hydrolysis of pretreated poplar wood
Authors: Holtzapple Mark T. , Caram Hugo S. , Humphrey Arthur E.
Published: December 2004

Two empirical models for the enzymatic hydrolysis of cellulose are used to analyze the same set of experimental data to determine if one model is superior to the other. Both models adequately describe the data. The parameters in both models may be correlated to the hydrolysis conditions of enzyme, substrate, and product inhibitor concentrations. Both empirical models have features which are consistent with theoretical models of cellulose hydrolysis.
Biofilm formation and chemostat dynamics: Pure and mixed culture considerations
Authors: Bryers James D.
Published: December 2004

Time‐dependent biofilm formation effects on continuous fermenter operation are modelled here in general for a mixed culture of N different microorganisms growing on a single substrate. Dynamic computer solutions are detailed for two versions of the general model: a pure culture and a simple two‐cell mixed culture. Pure culture model predictions compare favorably with two pure culture experiments in the literature where significant biofilm formation was noted. A mixed culture of one microbe (C1) having a higher growth rate than a second microbe (C2) is simulated for two hypothetical scenarios of microbe C2 having different magnitudes of cell deposition rate. Biofilm effects on the estimation of kinetic and stoichiometric parameters in both model versions, plus the impact of biofilms on mixed culture dynamics, are discussed.
Characterization of intracellular accumulation of poly‐β‐hydroxybutyrate (PHB) in individual cells of Alcaligenes eutrophus H16 by flow cytometry
Authors: Srienc F. , Arnold B. , Bailey J. E.
Published: December 2004

Poly‐β‐hydroxybutyrate (PHB) accumulates in individual cells of Alcaligenes eutrophus in the form of refractile bodies which alter the light‐scattering properties of individual cells. Flow cytometry has been applied to measure the distributions of single‐cell light‐scattering intensity in Alc. eutrophus populations during batch cultivation of the organism. These measurements clearly identify heterogeneities in the inoculum which influence the lag interval prior to beginning of exponential growth. Light‐scattering distributions show greater homogeneity and are extremely similar during balanced, exponential growth. After exhaustion of the nitrogen source and with carbon source still available, significant PHB accumulations occur and the flow cytometry measurements reveal extreme heterogeneity in single‐cell light‐scattering properties. These measurements clearly demonstrate the potential advantages of single‐cell light‐scattering measurements by flow cytometry for analysis and control of certain fermentation processes. Single‐cell light‐scat light‐scattering measurements in conjunction with flow sorting instrumentation have been applied to demonstrate enrichment of PHB‐producing cells, initially present in a number concentration of 0.01%by a factor of 300 in a single pass. Flow cytometry–cell sorting technology should find significant application in strain improvement and mutant selection.
Sugar cane bagasse as a possible source of fermentable carbohydrates. I. Characterization of bagasse with regard to monosaccharide, hemicellulose, and amino acid composition
Authors: Du Toit P. J. , Olivier S. P. , van Biljon P. L.
Published: December 2004

Individual monosaccharides present in bagasse hemicellulose were determined using HPLC and other chromatographic procedures. The presence of higher oligomers of the monosaccharides could also be determined. No single procedure can separate and identify all the naturally occurring monosaccharides. The pentosan fraction of bagasse wa successfully hydrolyzed and extracted with 5% (m/v)HCl, and the rate of release of individual monosaccharides was determined. Xylose was the main component in the hydrolyzates, while glucose, arabinose, and galactose present in the side chains of the pentosans were initially released at a fast rate. This treatment resulted in obtaining 229 mg/g xylose (85% of theoretical maximum) and 44 mg/g glucose from bagasse. Only arabinose (2.8 mg/g) and galactose (0.75 mg/g) was also present in detectable quantities. A total of 309 mg monosaccharides were obtained from 1 g of bagasse by this treatment. The results indicated that hydrolysis conditions for specific plant materials depend on the composition of the specific material being utilized. A part of the pentosan fraction (77.1%) was hydrolyzed at a high rate, while 22.9% was more stable and hydrolyzed more slowly. Although 39.8% dry bagasse could be obtained in solution by treatment with dilute alkali, only about 72% of the available hemicelluloses could be extracted in this way if the bagasse was not delignified beforehand. Amino acids and peptides or proteins were also extracted to very much the same with the alkali.
Deactivation kinetics of immobilized α‐chymotrypsin subpopulations
Authors: Clark Douglas S. , Bailey James E.
Published: December 2004

Electron paramagnetic resonance (EPR) spectroscopy has been applied in concert with measurements of catalytic activity and the quantity of active immobilized protein to study the deactivation in 50% n‐propanol of α‐chymotrypsin immobilized on CNBr–Sepharose 4B. These analyses focus on the behavior of two distinct active forms of immobilized enzyme, designated here A and B, identified in previous studies. Raw data provided by EPR spectroscopy clearly show that the relative quantities of active chymotrypsin‐A and active chymotrypsin‐B change as a result of exposure to alcohol, with the relative quantity of the B form increasing with time. These and additional results provide evidence that the distribution of A and B forms is a function of active enzyme loading but independent of the means used to obtain the loading. Different kinetic models in conjunction with experimental observations consistently indicate that the activity of enzyme form B, by far the more active enzyme form, does not change significantly during the initial 60 min of catalyst deactivation but then decreases appreciably.
The surface activity of Acinetobacter calcoaceticus sp. 2CA2
Authors: Neufeld R. J. , Zajic J. E.
Published: December 2004

The hydrocarbon metabolizing Acinetobacter calcoaceticus sp. 2CA2 reduces the surface tension of the culture broth during growth on liquid hydrocarbons. This activity, which is not evident during growth on soluble substrates, is associated with the whole cells. Removing the cells from the culture broth increases the surface tension of the liquid phase. The cells when resuspended in water result in a dramatic lowering of the surface tension. Acinetobacter sp. 2CA2 tends to partition between the two liquid phases during growth on hydrocarbons. Both the hydrocarbon bound and nonadhering cells are equally surface active. The whole cells are also able to form and stabilize kerosene–water emulsions. This ability is not related to the lowering of the liquid surface or interfacial tension, since both surface active and nonsurface active cells demonstrated the same emulsifying properties. An extracellular lipopeptide produced during growth on hydrocarbons is not surface active but effectively forms and stabilizes kerosene–water emulsions. The cells and extracellular lipoptide are also effective in de‐emulsifying surfactant stabilized test emulsions. The lipopeptide product reduced the half‐life of a Tween‐Span (TS) stabilized kerosene–water emulsion from 650 to 0.4 h at product concentrations of less than 1% (w/v).
Pretreatment of indian cane molasses for increased production of citric acid
Authors: Kundu Subir , Panda Tapobrata , Majumdar S. K. , Guha Barun , Bandyopadhyay K. K.
Published: December 2004

Surface culture citric acid fermentation was carried out by Aspergillus niger T55, a strain isolated from its natural source, using cane molasses, either untreated or treated by various methods. Citric acid biosynthesis is seriously impaired by both organic and inorganic inhibitors. A combined treatment of molasses with tricalcium phosphate, hydrochloric acid, and Sephadex fractionation minimizes the level of inorganic and organic inhibitors in molasses and increases the production of citric acid (65% weight yield based on total reducing sugar). The optimum level of individual metal ions for citric acid production depends on the concentration of other metals in the medium.
Freeze preservation of synchrony in cultures of enterobacteriaceae synchronized by continuous phasing in phosphate‐limited media
Authors: Kepes François , Kepes Adam
Published: December 2004

In order to achieve synchronization of cell division by continuous phasing, the growth of enteric bacteria has been limited by inorganic phosphate. After a short starvation, the culture was automatically diluted twofold so that the limiting nutrient allowed for one doubling exactly. An automatic device was designed to carry out repeated cycles of growth, starvation and dilution with adjustable periodicity. After 12–24 automatic cycles, which were usually achieved largely overnight, synchronous cell divisions could be observed for several generations in nonlimiting culture conditions. When portions of the phased culture were frozen and kept at low temperature for periods up to several months, these freeze‐preserved populations exhibited a synchronous growth upon thawing and cultivation. This technique has thus the potential of providing synchronized cultures of a variety of bacterial strains at the desired time.
Tyrosine hydroxylase activity of immobilized tyrosinase on enzacryl‐AA and CPG‐AA supports: Stabilization and properties
Authors: Vilanova E. , Manjon A. , Iborra J. L.
Published: December 2004

Frog epidermis tyrosinase has been immobilized on Enzacryl‐AA (a polyacrylamide‐based support) and CPGzirclad‐Arylamine (a controlled pore glass support) in order to stabilize the tyrosine hydroxylase activity of the enzyme; in this way, the immobilized enzyme could be used to synthesize L‐dopa from L‐tyrosine. The activity immobilization yield YIMEact (higher than 86%), coupling efficiency (up to 90%), storage stability (no loss in 120 days), and reaction stability (t1/2 was higher than 20 h in column reactors) were measured for tyrosinase after its immobilization. The results showed a noticeable improvement (in immobilization yield, coupling efficiency, and storage and operational stabilities) over previous reports in which tyrosinase was immobilized for L‐dopa production. The activity and stability of immobilized enzyme preparations working in three different reactor types have been compared when used in equivalent conditions with respect to a new proposed parameter of the reactor (Rp), which allows different reactor configurations to be related to the productivity of the reactor during its useful life time. The characteristic reaction inactivation which soluble tyrosinase shows after a short reaction time has been avoided by immobilization, and the stabilization was enhanced by the presence of ascorbate. However, another inactivation process appeared after a prolonged use of the immobilized enzyme. The effects of reactor type and operating conditions on immobilized enzyme activity and stability are discussed.
Biological removal of pyritic sulfur from coal by the thermophilic organism Sulfolobus acidocaldarius
Authors: Kargi Fikret , Robinson James M.
Published: December 2004

More than 90% of initial pyritic sulfur was removed from bituminous coal samples (containing 2.1% pyritic sulfur) using the thermophilic organism Sulfolobus acidocaldarius. Microbial desulfurization rate was improved nearly ten fold by adjusting the N/P and N/Mg ratios in the nutrient medium. Environmental conditions were optimized. The optimal values of temperature and pH were 70°C and 1.5, respectively. The influence of certain process variables (such as coal pulp density, particle size, and initial cell number density) on the rate of pyritic sulfur removal were determined. A pulp density of 20%, particle size of D¯p < 48 μm, and an initial cell number density of 1012 cells/g pyrite in coal were found to be optimal. The carbon dioxide enriched air did not improve the rate of pyritic sulfur removal compared to pure air at 10% pulp density of coal samples containing 2.1% pyritic sulfur. The kinetics of microbial leaching of pyritic sulfur from coal was investigated. The rate of leaching was found to be first order with respect to pyritic sulfur concentration in the reaction medium.
Equations and calculations of product yields and preferred pathways for butanediol and mixed‐acid fermentations
Authors: Papoutsakis Eleftherios Terry , Meyer Charles L.
Published: December 2004

Using the available information of fermentation biochemistry, fermentation (stoichiometric) equations are derived for anaerobic saccharolytic fermentations of butanediol and mixed acids. The equations describe the interrelations among the fermentation products, biomass, and consumed substrate (glucose). The validity of the equations is tested using a variety of batch data from the literature. The validity of the equations is expected to extend to steady‐state and transient fermentations, as well. Uses, improvements, and extensions of the equations are also discussed in detail. Among others, it is shown that the equations are useful for checking the consistency of experimental data, for calculating maximal yields and selectivities for the fermentation products, and calculating the extent of utilization of the Embden–Meyerhof–Parnas pathway versus the Hexose Monophosphate pathway of glucose utilization.
Pilot trials of the microbial degradation of Christos–Bitas water in oil emulsion (chocolate mousse) and BP llandarcy gas oil using venturi aeration
Authors: Berwick Paul G.
Published: December 2004

Oil residues arising from the Christos–Bitas spillage were found to contain 28% of oil extractable by carbon tetrachloride; the remainder consisted of water and undefined solids. Christos–Bitas mousse was added to 1.18 m3 liquor inoculated with oil‐contaminated marine mud, and aerated with a 1.5‐hp vortex pump and venturi nozzle (12.5 mm) in a cylindrical tank. After 70 days, oil degradation reached 7 mg oil/L/h. About 98% of the solvent extractable oil added was degraded over 83 days. Analysis of oil residues harvested at the end of this experiment showed that there was a decreasing trend in percent degradation in the following order: aromatics > saturates > heterocyclics > asphalts. No less than 94% of any fraction analysed was degraded.

In the second pilot trial, oil degradation was carried out in a cylindrical jacket tank containing 6.82 m3 liquor inoculated with oil‐contaminated marine mud from Penarth, South Wales, UK, together with pure cultures derived from the same source, and aerated with a 7.5‐hp vortex pump and venturi nozzle (18 mm diameter). Mixing of the oil was inhomogeneous for the first 100–110 days. The overall degree of substrate dispersion and total oil balance was determined by sampling at different depths. Degradation by the mixed culture was achieved at the rate of 164 mg oil/L/h. After 224 days, this was equivalent to 9.6 × 103/kg−1/yr;(214 kg/wk) for 6.82 m3 of liquor. The degradation rate continued to rise as the feed rate was increased by means of an automatic, timed pump. A lag phase of five to six months was necessary to allow the mixed population to build up to an exploitable level.
Effect of glucose supplements on the fermentation of xylose by Pachysolen tannophilus
Authors: Jeffries T. W. , Fady J. H. , Lightfoot E. N.
Published: December 2004

Hemicellulosic sugars, predominantly D‐xylose, comprise about one‐half the total carbohydrate that can be obtained from hardwoods and agricultural residues through dilute acid hydrolysis. Because rates and yields in the xylose fermentation are low, economic utilization of these materials as fermentation feedstocks is difficult. Pachysolen tannophilus formed 5.5% ethanol from 12% glucose but only 2% ethanol from 12% xylcose. Aeration doubled the specific rate of D‐glucose fermentation by P. tannophilus, as compared to anaerobic fermentation, but the specific rate of the xylose fermentation remained unchanged. Periodic additions of 0.5% D‐glucose to aerobic fermentations of 3% xylose increased the yield of ethanol from 0.28 g/g xylose to greater than 0.41 g/g xylose utilized. The rate of xylose utilization remained unchanged, and radiotracer studies showed that addition of 0.5% glucose did not inhibit xylose utilization under aerobic or anaerobic conditions. No enhancement was observed anaerobically, nor was enhancement observed with acid hydrolysates, apparently because of the presence of acetic acid which inhibited growth and fermentation.
Effect of pH on the batch fermentation of pullulan from sucrose medium
Authors: Lacroix Carine , LeDuy Anh , Noel Gaetan , Choplin Lionel
Published: December 2004

Two strains of the yeast‐like fungus Aureobasidium pullulans 2552 and 140B have been used for the fermentative production of the polysaccharide pullulan from a sucrose synthetic medium. In the batch fermentation, either in Erlenmeyers or in the fermentor, the pH of the culture medium was decreased rapidly from its initial pH value of 5.5 to the self‐stabilized final value of 2.5 within 24 h. Experiments on the effect of initial pH on the fermentation revealed that at very low initial pH values, such as at pH 2, the polysaccharide production was in‐significant. However, the biomass concentration obtained was very high at this very low initial pH value. This interesting phenomenon was served as the basic principle for the development of the bistaged pH fermentation process for the production of pullulan. In this process the first stage of fermentation was conducted at the very acidic pH for the best production of biomass. When the biomass concentration reached its maximum value, the second stage of fermentation was initiated by adjusting the medium pH to a higher value for promoting the synthesis of the polysaccharide. Experiments conducted in Erlenmeyers and in the fermentor confirmed this concept. The bistaged pH process enhanced the polysaccharide concentration in the medium, influenced the rheological properties of the fermentation broth, and has a potential of operation under nonsterile and nonaseptic conditions.
Separation and purification of enzymes by continuous pH‐parametric pumping
Authors: Huang Shih Yow , Lin Ching Kuan , Juang Long Yih
Published: December 2004

Trypsin and chymotrypsin were separated from porcine pancreas extract by continuous pH‐parametric pumping. CHOM (chicken ovomucoid) was convalently bound to laboratory‐prepared crab chitin with glutaraldehyde to form an affinity adsorbent of trypsin. The pH levels of top and bottom feeds were 8.0 and 2.5, respectively. Similar inhibitor, DKOM (duck ovomucoid), and pH levels 8.0 and 2.0 for top and bottom feeds, respectively, were used for separation and purification of chymotrypsin. ε‐Amino caproyl‐D‐tryptophan methyl ester was coupled to chitosan to form an affinity adsorbent for stem bromelain. The pH levels were 8.7 and 3.0. Separation continued fairly well with high yield, e.g., 95% recovery of trypsin after continuous pumping of 10 cycles. Optimum operational conditions for concentration and purification of these enzymes were investigated. The results showed that the continuous pH‐parametric pumping coupled with affinity chromatography is effective for concentration and purification of enzymes.
Diffusion coefficient and its dependency on some biochemical factors
Authors: Onuma M. , Omura T. , Umita T. , Aizawa J.
Published: December 2004

The diffusion coefficients for glucose and oxygen through the microbial aggregate were measured, and then the dependency on the biochemical factors was investigated. Kinetic and diffusion studies were carried out experimentally for this purpose. Both coefficients were found to be dependent not only on the bacteria concentration but also on the C/N ratio of microbial aggregate at the high bacteria concentration, when the temperature was 20 ± 2°C. On the other hand, these values were considered to be independent of both factors at the low bacteria concentration, when the temperature was 20 ± 2°C. In other words, both coefficients were approximately 86–95% of the values in water at the high bacteria concentration and nearly 100% of the values in water at the low bacteria concentration. It was also found that they were dependent on the temperature.
Analysis of bioenergetic yield and maintenance parameters associated with mixotrophic and photoheterotrophic growth
Authors: Lee H. Y. , Erickson L. E. , Yang S. S.
Published: December 2004

Carbon, available electron, and energetic yields are determined from literature data for photoheterotrophic and mixotrophic growth. Maintenance coefficients and energetic yields corrected for maintenance are estimated using covariate adjustment methods for several sets of data. Results are presented and compared for anaerobic photoheterotrophic growth, microaerobic photoheterotrophic growth, aerobic photoheterotrophic growth, and aerobic mixotrophic growth to gain a better understanding of yields for these photosynthetic processes.
Cell immobilization in κ‐carrageenan for ethanol production
Authors: Luong J. H. T.
Published: December 2004

A combination of extended Monod kinetics and the diffusional equation was used for evaluating the effectiveness factor of entrapped immobilized cells. Based on the kinetics of Zymomonas mobilis reported in the literature, the numerical results have revealed that the problem of mass transfer diffusional restrictions can be neglected by using small beads (1 mm in diameter) with a corresponding cell loading up to 276 g/L gel. On the basis of the numerical results obtained, the application of immobilized cells for continuous ethanol production was investigated. The κ‐carrageenan method was utilized to entrap Z. mobilis CP4, a potential ethanol producer. A two stage fermentation process has also been developed for ethanol production by the Z. mobilis carrageenan‐bound cells. About 90 g/L ethanol was produced by immobilized cells at a total residence time of 1.56 h. The ethanol yield was estimated to be 93% of theoretical. The results obtained in this study also indicated that the control of optimum pH in an immobilized cell column is necessary to enhance the rate of ethanol production.
Assay of the high‐alkaline proteinase from alkalophilic bacillus PB92 using a chromogenic tripeptide substrate
Authors: Gray C. J. , Barker S. A. , Dhariwal M. S. , Sullivan J. M.
Published: December 2004

The chromogenic tripeptide substrate, benzyloxycarbonylglycyl‐L‐prolyl‐L‐citrulline p‐nitroanilide, is proposed for the assay of the high‐alkaline proteinase, HAP‐PB92, from an alkalophilic Bacillus. The assay method is sensitive, reproducible, and may be adapted for an automatic system.
The acetone butanol fermentation on glucose and xylose. II. Regulation and kinetics in fed‐batch cultures
Authors: Fond Olivier , Engasser Jean‐Marc , Matta‐El‐Amouri Ghassam , Petitdemange Henri
Published: December 2004

The kinetics in fed‐batch cultures of acetone butanol fermentation by Clostridium acetobutylicum is compared on glucose, xylose, and mixtures of both sugars. The final conversion yield of sugars into solvents always increases with the sugar feeding rate. At low feeding rates, the sugar concentration in the medium becomes limiting, which results in a slower cellular growth, a slower metabolic transition from an acid to a solvent fermentation and, thus, a higher accumulation of acids. It is only at sufficiently high feeding rates that fed‐batch fermentations yield kinetic results comparable to those of batch fermentations. With mixtures of glucose and xylose, because of a maintained low glucose level, both sugars are taken up at the same rate during a first fermentation period. An earlier accumulation of xylose when the fermentation becomes inhibited suggest that xylose utilization is inhibited when the catabolic flux of glucose alone can satisfy the metabolic activity of the cell. Kinetic results with batch and fed‐batch fermentations indicate several important features of the regulation of C. acetobutylicum metabolism: an early inhibition by the produced acids; an initiation of solvent formation between 4 and 6 g/L acetic and butyric acid depending on the metabolic activity of the cell; a metabolic transition from acids to solvents production at a rate closely related to the rate of sugar uptake; during solvent production, a reassimilation of acids above a minimal rate of sugar consumption of 0.2 h−1; a final inhibition of the fermentation at a total butanol and acids concentration of ca. 20 g/L.
Mathematical model of a batch acetone–butanol fermentation
Authors: Votruba J. , Volesky B. , Yerushalmi L.
Published: December 2004

A mathematical model for the batch culture of Clostridium acetobutylicum was formulated using experimental data for anaerobic solvent production. The model summarizes biochemical as well as physiological aspects of growth and metabolite synthesis by the production strain. The key fermentation rates are expressed and evaluated with regard to substrate consumption and butanol end‐product inhibitory effects. Parametric sensitivity analysis of the batch process model was carried out, indicating the importance of the key process parameters.
Rate and yield relationships in the production of xanthan gum by batch fermentations using complex and chemically defined growth media
Authors: Pinches Anthony , Pallent Leslie J.
Published: December 2004

Rate and yield information relating to biomass and product formation and to nitrogen, glucose and oxygen consumption are described for xanthan gum batch fermentations in which both chemically defined (glutamate nitrogen) and complex (peptone nitrogen) media are employed. Simple growth and product models are used for data interpretation. For nitrogen sources, rate and yield parameter estimates are shown to be independent of initial nitrogen concentrations. For stationary phases, specific rates of gum production are shown to be independent of nitrogen source but dependent on initial nitrogen concentration. The latter is modeled empirically and suggests caution in applying simple product models to xanthan gum fermentations.
Sequential substrate utilization and effectiveness factor in fixed biofilms
Authors: Droste R. L. , Kennedy K. J.
Published: December 2004

A mathematical model describing the change in effectiveness factor or effective diffusivity for the intermediate substrate in sequential substrate removal reactions in fixed biofilms is developed. Typical results from the numerical solution of the resulting equation are presented. The production of intermediate substrate in the biofilm increases the conversion of primary substrate to ultimate product in all cases, but the increase is not always significant. Using typical data applying to laboratory anaerobic fermentation studies, it is demonstrated that a small but significant change in reaction kinetics and the effectiveness factor exists.