bluuebunny/crossref_metadata_2025_split huggingface dataset:
Hydrolysis of milk lactose by immobilized β‐galactosidase–hen egg white powder
Authors: Kaul Rajni , D'Souza S. F. , Nadkarni G. B. 
Published: December 2004

AbstractImmobilized β‐galactosidase was obtained by crosslinking the enzyme with hen egg white using 2% glutaraldehyde. The gel obtained could be lyophilized to give a dry enzyme powder. The pH optimum of both the soluble and immobilized enzyme was found to be 6.8. The immobilized enzyme showed a higher Km for the substrates. The extent of enzyme inhibition by galactose was reduced upon immobilization. The stability towards inactivation by heat, urea, gamma irradiation, and protease treatment were enhanced. The bound enzyme as tested in a batch reactor could be used repeatedly for the hydrolysis of milk lactose. The possible application of this system for small‐scale domestic use has been suggested.
Enzymatic hydrolysis of inulin to fructose by glutaraldehyde fixed yeast cells
Authors: Workman Wesley E. , Day Donal F. 
Published: December 2004

AbstractInulin, a polyfruction, is found as the reserve carbohydrate in the roots and tubers of various plants (i.e. Jerusalem artichoke, chicory, and dahlia tubers). The β‐fructofuranosidase (inulase) from the yeast Kluyveromyces fragilis is of interest because of its industrial potential in fructose syrup and alcohol production from inulin containing plants. We have found that the inulase of K. fragilis can be immobilized in the yeast cells by glutaraldehyde treatment. These cells are resistant to physical and enzymatic destruction. Although the exact nature of the immobilization is not fully understood, the kinetic parameters of the immobilized enzyme are similar to those of the soluble enzyme. No reduction of enzyme activity was observed after glutaraldehyde treatment and glutaraldehyde concentration did not affect enzyme activity. A 96% hydrolysis of dahlia inulin was achieved in 10.5 h with a 9.5% (w/v) fixed enzyme suspension. A Jerusalem artichoke extract containing 16.8%polyfructan was completely hydrolyzed in 3.5 h with a 0.24% (w/v)fixed enzyme suspension. This is a time frame feasible for industrial consideration.
Control strategies of continuous bioprocesses based on biological activities
Authors: Meyer C. , Beyeler W. 
Published: December 2004

AbstractBased on the material balance principle applied to microbial reactions in continuous bioprocesses, the concept of reaction rate control has been developed theoretically. This concept provides a more direct way of controlling biological activities than the control of physical or chemical parameters in practice today. From an analysis of dynamic and steady‐state experiments, two control systems for carbon dioxide production rate control during the continuous culture of baker's yeast have been designed and evaluated experimentally. In these control methods, intracellular NADH concentration is used as an immediate indication of the onset of glucose repression. A more sophisticated master controller based on the respiratory quotient can be combined with these control methods. The resulting control system provides a means to indirectly optimize biomass production while preventing ethanol formation in the continuous culture of baker's yeast.
Stabilization of soluble and immobilized horse liver alcohol dehydrogenase by adenosine 5′‐monophosphate
Authors: Görisch Helmut , Schneider Manfred 
Published: December 2004

AbstractHorse liver alcohol dehydrogenase, which catalyzes oxidoreductions for a broad spectrum of substrates of organic chemical interest, was immobilized on CNBr‐activated Sepharose and on decylamine‐substituted agarose. The specific activities of the immobilized enzyme preparations were compared with the free enzyme, and the apparent Km values of the preparations were determined for a selection of substrates. At pH 9 and 60°C, soluble liver alcohol dehydrogenase was rapidly inactivated, while the enzyme immobilized on CNBr‐activated Sepharose was more stable. Adenosine monophosphate (AMP), adenosine diphosphate, and adenosine diphosphoribose protected the free and immobilized alcohol dehydrogenase against heat inactivation. On storage under a variety of conditions, AMP effectively stabilized free horse liver alcohol dehydrogenase and the immobilized preparations.
Effects of temperature on plasmid stability and penicillinase productivity in a transformant of Bacillus stearothermophilus
Authors: Aiba Shuichi , Koizumi Jun‐ichi 
Published: December 2004

AbstractAfter transforming host cells of Bacillus stearothermophilus CU21 with a recombinant plasmid pLP11 that harbored constitutive penicillinase genes of B. licheniformis CO1, both the stability of the plasmid and specific rate of penicillinase production were studied. The temperature at which the plasmid could be kept in a stable fashion in the transformant of B. stearothermophilus CU21 (pLP11) ranged nearly from 44 to 50°C, irrespective of batch and continuous cultures. Continuous and steady‐state cultures of the transformant could only be realized within this narrower temperature range. Indeed, the approximate temperature ranges of growth for the host and transformant were from 40 to 70°C and from 40 to 63°C, respectively. Clearly, the upper limit for the growth temperature of host cells decreased when they were transformed. Kinetic patterns of penicillinase production in continuous culture of the transformant (with plasmid) from 44 to 50°C differed remarkably from that of B. licheniformis CO1 (without plasmid) at 37°C.
Effect of crystallinity and degree of polymerization of cellulose on enzymatic saccharification
Authors: Puri Vinod P. 
Published: December 2004

AbstractLignocellulose materials were pretreated by methods known to improve enzymatic saccharification, and the percentage crystallinity (x‐ray diffraction) and degree of polymerization were measured. It was observed that although the percentage crystallinity of cellulose was not altered by alkaline explosion (AE), carbon dioxide explosion (CE), ozone, and sodium chlorite treatment, very great increases were obtained in the extent of enzymatic saccharification. All the pretreatments studied except sodium chlorite caused significant reduction in degree of polymerization. It appears likely that the rate and extent of saccharification is governed by particle size, surface area, and degree of polymerization, since crystallinity effects alone do not explain the observed trends in the hydrolysis data.
Physical and chemical conditions for microbial oil degradation
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 comprised water and undefined solids. When incubated in 8‐L rectangular tanks with a mixed population of mainly bacteria to which diammonium hydrogen phosphate was added, ca. 97% of the Christos‐Bitas oil fraction was degraded. When the same substrate was degraded by only three isolated Pseudomonas strains in 1‐L cylindrical tanks, degradation was only ca. 56%. Raising the temperature from 20 to 50°C brought about a visible loss in cell viability with only ca. 38% of the substrate degraded. Oil degradation proceeded in direct proportion to increases in cell attachment to the dispersed oil. The aliphatic fraction of Kuwait crude oil up to nC25 measured by gas liquid chromatography (GLC) was oxidized within 48 h. Using this substrate the three pseudomonads together brought about a more complete degradation (87%) than a single Bacillus isolate. The Bacillusstrain was capable of deggrading between 50 and 65% of the crude, depending on whether diammonium hydrogen phosphate supplemented a peptone‐based medium. The preferential biodgradability of fractions was the following aliphatics > aromatics > asphalts, as has been widely reported.
Bacterial removal of mercury from sewage
Authors: Hansen Conly L. , Zwolinski Gary , Martin Debra , Williams Jeffrey W. 
Published: December 2004

AbstractMercury‐resistant bacteria, which are able to reduce mercuric ion (Hg2+) to metallic mercury (Hg0), were examined for their ability to remove mercury from waste‐water aerobically. Growth studies in artificial medium indicated that mercury increases the lag phase, but does not effect the growth rate of these bacteria. Further studies demonstrated that growth was minimal during a phase of rapid mercury removal, after which growth resumed. Small but significant amounts of carbohydrates are required for the mercuric ion reduction. Prolonged periods of bacterial growth under nonsterile conditions was accomplished without the loss of the mercuric reducing ability of the culture. A continuous culture of the resistant organism was maintained on raw sewage for two weeks, during which time relatively high concentrations of mercury (70 mg/L) were removed from the sewage at a rate of 2.5 mg/L h and at efficiencies exceeding 98%.
Genetically structured models forlac promoter–operator function in the Escherichia coli chromosome and in multicopy plasmids: Lac operator function
Authors: Lee Sun Bok , Bailey James E. 
Published: December 2004

AbstractA mathematical model based on known molecular interactions has been formulated to describe quantitatively regulation of expression of the lactose (lac) operon in the Escherichia coli chromosome and in multicopy plasmids. This model is genetically structured such that a nucleotide sequence change affecting transcription initiation at the lac promoter–operator influences one or very few directly corresponding model parameters. The model simulates chromosomal lac operon function in good agreement with previous experimental measurements for many lacl and lacO mutant systems as well as for diploid cells which carry F'lac episomes. Simulation results clearly show the loss of cloned lac operator regulation as the plasmid copy number increases, in agreement with experimental trends. The importance of this class of models in designing DNAs, organisms, and reactors for precise regulation of cloned gene expression is discussed.
Studies on immobilized fungal spores for microbial transformation of steroids: 11 α‐Hydroxylation of progesterone with immobilized spores of Aspergillus ochraceus G8 on polyacrylamide gel and other matrices
Authors: Bihari Vinod , Goswami P. P. , Rizvi S. H. M. , Khan A. W. , Basu S. K. , Vora V. C. 
Published: December 2004

AbstractHydroxylation in the 11 α‐position in the progesterone molecule employing immobilized spores of Aspergillus ochraceus strain No. G8 (CDRI catalogue No.) was achieved. For immobilization the activity of the spores was evaluated on a variety of matrices such as alginate beads, epoxy resin beads, polyacrylamide gel, and collagen. Spores entrapped in polyacrylamide gel were found to be the most active. Studies of various parameters, e.g. monomer content, cell loading capacity, optimum pH, temperature, and substrate concentration, were carried out on polyacrylamide gel. In polyacrylamide, the entrapped spores normal decay pattern, as indicated by loss of activity, was observed after four uses. At the end of 15 cycles, the residual activity was found to be 18% of the original. It was possible to regenerate the activity by incubating the preparation in a nutrient medium. The regenerated spores showed increasing rate of loss of activity upon recycling.
Optimization of fermentation conditions for alcohol production
Authors: Bowman Llewellyn , Geiger Edwin 
Published: December 2004

AbstractThe quantitative effects of carbohydrate levels, degree of initial saccharification, glucoamylase dosage, temperature, and fermentation time were investigated using a Box–Wilson central composite design protocol. WithSaccharomyces cerevisiaeATCC 4126, it was found that the use of a partially saccharified starch substrate markedly increased yields and attainable alcohol levels. Balancing the degree of initial saccharification with the level of glucoamylase used to complete hydrolysis was found necessary to obtain optimum yields. The temperature optimum was found to be 36°C. The regression equations obtained were used to model the fermentation in order to determine optimum fermentation conditions.
A comparative study of the enzymatic hydrolysis of acid‐pretreated white pine and mixed hardwood
Authors: Grethlein H. E. , Allen D. C. , Converse A. O. 
Published: December 2004

AbstractRemoval of hemicellulose by acid pretreatment in a flow reactor followed by enzymatic hydrolysis of the neutralized slurry has resulted in glucose yields as high as 95% for mixed hardwood. For white pine, however, the maximum glucose yield is 65%. Although pine has a higher extractives content, removal of the extractives prior to enzymatic hydrolysis does not increases the glucose yield. Pore size measurements reveal that the increase in pore volume, in the size range of the cellulase molecule, following pretreatment for pine is only about one‐half the value obtained with mixed hardwood. This suggests that pore volume is an important determinant of substrate–enzyme reactivity.
Fed‐batch cultivation of Cellulomonas on sugarcane bagasse pith
Authors: Rodríguez Hilda , Enríquez Antonio 
Published: December 2004

AbstractA high biomass concentration (19.9 g/L) was obtained with the fed‐batch cultivation of Cellulomonas on pretreated sugarcane bagasse pith. Similar results in biomass concentration, yield, and substrated consumption were obtained with the discontinuous feed of bagasses as with discontinuous feed supplemented with a partial continuous addition of salts. Two or more growth phases were detected, probably caused by the differential utilization of bagasse components. An acceptably low content of bagasse components remained in the biomass after separation.
Optimization of microencapsulation parameters: Semipermeable microcapsules as a bioartificial pancreas
Authors: Goosen Mattheus F. A. , O'Shea Geraldine M. , Gharapetian Hrire M. , Chou Sheng , Sun Anthony M. 
Published: December 2004

AbstractAn improved membrane has been developed for the microencapsulation of islets of Langerhans which protects these cells from the immune system. These requirements were accomplished through the optimization of important microencapsulation parameters and through the improved biocompatibility of a new alginate‐poly‐l‐lysine (PLL)–alginate capsule membrane. Spherical and smooth microcapsules could be formed by utilizing a purer sodium alginate and by keeping the viscosity of the sodium alginate solution above 30 cps. The strength of the capsule membrane was enhanced by increasing the alginate–PLL reaction time as well as the PLL concentration. The permeability of the membrane [4 μm thick, 93% (w/w) water] was a function of the viscosity average molecular weight (Mv) of the PLL (Mv = 4000−4 × 105) used in the encapsulation procedure. Microcapsules prepared with PLL with Mv = 1.7 × 104 were the least permeable, being impermeable to normal serum immunoglobulin, albumin, and haemoglobin. The microencapsulation procedure, by protecting transplanted tissue from the components of the immune system, has great clinical potential as a new form of treatment for diseases such as diabetes and liver disease.
Nutrient‐limited continuous culture in the phauxostat
Authors: Rice Craig W. , Hempfling Walter P. 
Published: December 2004

AbstractStable steady‐state growth of Escherichia coli B limited by succinate, phosphate, or sulfate ion over the range of specific growth rates of 0.025–0.51 h−1 was achieved using pH‐controlled auxostasis in the phauxostat. The concentration of the growth‐limiting substrate in the growth vessel could be varied at will in the region of the Monod half‐maximal saturation constants by adjusting the concentration of that substrate in the reservior (at constant buffering capacity) or by varying the population density of the culture through changing the buffering capacity of the medium in the reservoir.
Effect of pretreatments and fermentation on pore size in cellulosic materials
Authors: Lin K. W. , Ladisch M. R. , Voloch M. , Patterson J. A. , Noller C. H. 
Published: December 2004

AbstractSurface area has been proposed as a major factor determining the extent of enzymatic hydrolysis of cellulose. We used cornstalk residue (CR) and Solka Floc BW‐300 (SF) as substrates and NaOH (a cellulose swelling agent) and iron sodium tartrate (FeTNa, intercolates between cellulose microfibrils) as pretreatments to study the effect of surface area on extent of fermentation. Micropore sizes (8‐130 Å) were determined by a solute exclusion technique using glucose, cellobiose, and polyethylene glycols as molecular probes. The pore size distributions follow the logistic model function: I = a/[1+exp(b − cX)] where I is pore volume; X = log D; D is the molecular probe diameter; and a, b, and c are constants. The pore volumes of CR (1.9 mL/g) and SF (1.6 mL/g) are increased to 2.1 mL/g by pretreatment with NaOH. Pretreatment of SF with NaOH and cornstalk residue with FeTNa caused an upward shift in the pore size distribution. Fermentation of untreated CR by rumen microbes resulted in a 46% loss of dry matter while increasing the internal pore size and decreasing the pore volume to 0.9 mL/g. Fermentation of NaOH pretreated CR resulted in a 73% loss of dry matter with little change in pore size, total pore volume, or fiber composition. Fiber analysis indicated that selective utilization of hemicellulose over cellulose in both fermentations was small. The data show that: (1) removal of hemicellulose and lignin increases dry matter disappearance upon fermentation of the remaining material; (2) relative to the size of bacterial cellulases (40‐160 Å), the pretreatments have little effect on increasing accessibility of surface internal to the cellulose particles; and (3) the micropore changes caused by NaOH or FeTNa treatment do not explain the enchanced fermentation obtained for treated cornstalk residue. These observations infer that external or macropore surface properties may be a significant factor in determining the extent of utilization of the solid substrates by cellulolytic microorganisms.
Dynamics of a chemostat in which one microbial population feeds on another
Authors: Pavlou Stavros 
Published: December 2004

AbstractUnder certain simplifying hypotheses, a chemostat in which one microbial population feeds on another can be described by a system of three ordinary differential equations. A study is conducted to find which features of the equations are the most important to the dynamics of the system; it is found that the main influence comes from the from the particular form of the specific growth rate of the feeding population. Some conditions are derived that relate the form of the specific growth rate of the feeding population to the dynamic behaviour of the system.
Maltodextrin hydrolysis in a fluidized‐bed immobilized enzyme reactor
Authors: Vallat I. , Monsan P. , Riba J. P. 
Published: December 2004

AbstractThe present work deals with maltodextrin hydrolysis by glucoamylase immobilized onto corn stover in a fluidized bed reactor. An industrial enzyme preparation was covalently grafted onto corn stover, yielding an activity of up to 372 U/g and 1700 U/g for support particle sizes of 0.8 and 0.2 mm, respectively. A detailed kinetic study, using a differential reactor, allowed the characterization of the influence of mass transfer resistance on the reaction catalyzed by immobilized glucoamylase. A simple and general mathematical model was then developed to describe the experimental conversion data and found to be valid.
Effects of chemical modification on enzymatic activities and stabilities
Authors: Sadana Ajit , Henley James P. 
Published: December 2004

AbstractThe influence of chemical modification on the initial specific activity, residual activity, and deactivation kinetics of various enzymes is analyzed using a series mechanism. This straightforward multistate sequential model presented is consistent with the enzyme deactivation data obtained from different fields. The enzymes are placed in five different categories depending on the effect of chemical modification on initial specific activity and residual activity or stability. Wherever possible, structure–function relationships are described for the enzymes in the different categories. The categorization provides one avenue that leads to further physical insights into enzyme deactivation processes and into the enzyme structure itself.
Comparative study of the effect of ferrocyanide and EDTA on the production of ethyl alcohol from molasses by Saccharomyces cerevisiae
Authors: Oderinde Rotimi A. , Ngoka Lambert C. , Adesogan E. Kayode 
Published: December 2004

AbstractThe effects of potassium ferrocyanide and EDTA on ethyl alcohol production from molasses by Saccharomyces cerevisiae were investigated on simulated batch pilotplant‐scale conditions for alcoholic fermentation of molasses. Ethyl alcohol production was more sensitive to ferrocyanide than to EDTA. When ferrocyanide was introduced into the cultures at the time of inoculation, there was stimulation of ethyl alcohol production, with 261 ppm ferrocyanide producing the maximum effect, which was 3.0% more than in control cultures. When added during the propagation of the yeast, ferrocyanide depressed ethyl alcohol production by 4.0% maximum whereas EDTA stimulated ethyl alcohol production by 2.0%. Addition of ferrocyanide during the fermentation stage produced no significant effect on alcohol production, whereas over a wide range of EDTA concentration there was a steady increase in alcohol yield.
A kinetic model for anaerobic digestion of biological sludge
Authors: Pavlostathis Spyros G. , Gossett James M. 
Published: December 2004

AbstractThe principal objective of this study was the development and evaluation of a comprehensive kinetic model capable of predicting digester performance when fed biological sludge, preliminary conversion mechanisms such as cell death, lysis, and hydrolysis responsible for rendering viable biological sludge organisms to available substrate were studied in depth. The results of this study indicate that hydrolysis of the dead, particulate biomass—primarily consisting of protein—is the slowest step, and therefore kinetically controls the overall process of anaerobic digestion of biological sludge. A kinetic model was developed which could accurately describe digester performance and predict effluent quality.
An integral dynamic model for the UASB reactor
Authors: Bolle W. L. , van Breugel J. , van Eybergen G. C. , Kossen N. W. F. , van Gils W. 
Published: December 2004

AbstractIn this article a dynamic model of a continuous working UASB reactor is described. It results from the integration of the fluid flow pattern in the reactor, the kinetic behavior of the bacteria (where inhibition and limitation were taken into account), and the mass transport phenomena between different compartments and different phases. The mathematical equations underlying the model and describing the important mechanisms were programmed and prepared for computations and simulations by computer. The settler efficiency has to be over 99% to prevent the reactor from wash‐out. When the settler efficiency is over 99%, the total sludge content of the reactor increases steadily, so the reactor is hardly ever in a steady state. This implies dynamic modeling. The model is able to predict the various observable and nonobservable or difficult to observe state variables, e.g., the sludge bed height, the sludge blanket concentration, the short‐circuiting flows over bed and blanket, and the effluent COD concentration as a function of the hydrodynamic load, COD load, pH, and settler efficiency. The optimal pH value is between 6.0 and 8.0; fatty acid shock loadings are difficult to handle outside this optimal pH range.