bluuebunny/crossref_metadata_2025_split huggingface dataset:
Biofilm formation and chemostat dynamics: Pure and mixed culture considerations
Authors: Bryers James D. 
Published: December 2004

AbstractTime‐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

AbstractPoly‐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

AbstractIndividual 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

AbstractElectron 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

AbstractThe 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

AbstractSurface 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

AbstractIn 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

AbstractFrog 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

AbstractMore 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

AbstractUsing 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

AbstractOil 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

AbstractHemicellulosic 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

AbstractTwo 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

AbstractTrypsin 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

AbstractThe 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

AbstractCarbon, 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

AbstractA 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

AbstractThe 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.