bluuebunny/crossref_metadata_2025_split huggingface dataset:
Kinetic studies of enzymatic hydrolysis of insoluble cellulose: (II). Analysis of extended hydrolysis times
Authors: Lee Yong‐Hyun , Fan L. T. 
Published: December 2004

AbstractThe kinetics of enzymatic hydrolysis of pure insoluble cellulose by means of unpurified culture filtrate of Trichoderma reesei was studied, emphasizing the kinetic characteristics associated with the extended hydrolysis times. The changes in the hydrolysis rate and extent of soluble protein adsorption during the progress of reaction, either apparent or intrinsic, were investigated. The hydrolysis rate declined drastically during the initial hours of hydrolysis. The factors causing the reduction in the hydrolysis rate were examined; these include the transformation of cellulose into a less digestible form and product inhibition. The structural transformation can be partially explained by changes in the crystallinity index and surface area. The product inhibition was caused by the deactivation of the adsorbed soluble protein by the products, which essentially represents the so‐called “un‐competitive” inhibition. The kinetics of β‐glucosidase were also studied. The result has shown that the action of β‐glucosidase is competitively inhibited by glucose. It has been found that the integrated form of the initial rate expression cannot be used in predicting the progress of reaction because the digestibility of cellulose changes drastically as the hydrolysis proceeds, and that the rate expression for enzymatic hydrolysis of cellulose cannot be simplified or approximated by resorting to the pseudo‐steady‐state assumption. A mechanistic kinetic model of cellulose hydrolysis should include the following major influencing factors: (1)mode of action of enzyme, (2) structure of cellulose, and (3) mode of interaction between the enzyme and cellulose molecules.
Saccharification of bamboo carbohydrates for the production of ethanol
Authors: De Menezes Tobias J. B. , Dos Santos C. L. M. , Azzini A. 
Published: December 2004

AbstractBamboo carbohydrates were hydrolyzed with commercial amylases and a mixture of fungal culture broths containing cellulolytic and hemicellulolytic enzymes. The effects of cooking temperature and the size of fiber particles were also investigated. It was found that the higher the cooking temperature, the higher the rate of sugar formation and the lower the viscosity of the slurry. Additions of cellulose and hemicellulose digesting enzymes increased the sugar yield and decreased the viscosity of both the cooked and noncooked slurries. A smaller size of particle appeared to favor the average saccharification rate. Although glucose, xylose, and cellobiose were present in the hydrolysates, only 50% of the total carbohydrate was digested, and 78.9% of this was converted to reducing sugars. The alcohol efficiency for the fermentation of cooked and noncooked mashes by Saccharomyces was about 85%.
Toxicity of organic extraction reagents to anaerobic bacteria
Authors: Playne M. J. , Smith B. R. 
Published: December 2004

AbstractVarious forms of liquid‐liquid extraction systems are being developed to separate products, such as ethanol and volatile fatty acids (VFA), from fermentation liquids, since distillation is energetically expensive. Continuous extraction is advantageous, as product inhibition of the fermentation is minimized. However, some extraction solvents may be toxic or inhibitory to microorganisms.Thirty organic chemicals were examined by means of a small scale (60 mL) batch fermentation bioassay procedure for their toxicity to a commercial inoculum (Methanobac, W.B.E. Ltd.), which was a mixed culture of facultatively anaerobic, acid‐producing bacteria. Gas production, pH change of medium, and the concentrations of ethanol, VFA, and lactic acid were measured after 75 h growth. The optimum experimental conditions for toxicity testing were alfalfa as substrate (2 g), a buffered nutrient medium (pH 6.8), “Methanobac” inoculum (10 mL), and test chemicals at levels between 10 and 100 μL/mL.Thirteen chemicals were nontoxic, and included the paraffins (C6‐C12), phthalates, organophosphorus compounds, Freon 113 (1,1,2‐trichloro‐1,2,2‐trifluoro ethane), Aliquat 336 (tricaprylylmethyl ammonium chloride), di‐isoamyl ether, and trioctylamine. Other amine extractants were partially toxic. Alcohols (C5‐C12), ketones (C5‐C8), benzene derivatives, isoamyl acetate, and di‐isopropyl ether were toxic. Generally, the chemicals were not toxic unless present at levels in excess of that expected to be required to saturate the aqueous phase.Total gas production was a good indicator of toxicity even within 24 h, but the presence of homofermentative (nongas producing) lactic acid bacteria complicated interpretation.“Methanobac” inoculum was compared with an inoculum derived from a rumen culture for four test chemicals. The results were essentially the same. However, the toxicity of a chemical to bacteria is likely to vary considerably between bacterial species.
Ion exchange chromatography of proteins—prediction of elution curves and operating conditions. I. Theoretical considerations
Authors: Yamamoto Shuichi , Nakanishi Kazuhiro , Matsuno Ryuichi , Kamikubo Tadashi 
Published: December 2004

AbstractA mathematical model is proposed for the elution of proteins on ion exchange columns by a linear gradient increase and stepwise increase of ionic strength in order to predict relationships between the elution characteristics (the peak position, the peak width, etc.) and the operating conditions (the flow rate, the slope of gradient, etc). This model is in principle based on the continuous‐flow plate theory, in which the protein concentration and ionic strength dependent distibution coefficient between proteins and ion exchangers and zone sperading effects are taken into consideration. The advantage of this model is its simplicity since it requires only two parameters: The distribution coefficient and the number of plates. Since the distribution coefficient of proteins depends on both the protein concentration and ionic strength of the elution buffer, the number of plates should vary with time. However, it is extremely difficult to take into consideration the time‐dependent number of plates. Therefore, we assume that the number of plates is constant and related to that number derived from a mass balance model which includes longitudinal dispersion and gel phase diffusion. On the basis of these assumptions, a method for determining the number of plates by the moment method is presented. Although the dependencies of the peak position and peak width on the slope of linear gradient are predictable by numerical calculations of the present model, simpler methods for prediction of these dependencies are desirable. A graphical method is proposed for prediction of the peak position. For prediction of the peak width, an asymptotic solution is derived from a quasi‐steady‐state model.
Efficiency of lipid synthesis by yeasts
Authors: Eroshin V. K. , Krylova N. I. 
Published: December 2004

AbstractThe efficiency of lipid synthesis by ethanol‐grown yeasts is characterized using the coefficient of the lipid energetic yield (η1). This coefficient is defined as the fraction of energy in an organic substrate that is converted to lipids. The advantages of η1 compared with the “fat coefficient” (Fs) as well as the biomass energetic yield (η) compared with Ys are discussed.
Uranium binding by emulsan and emulsanosols
Authors: Zosim Zinaida , Gutnick David , Rosenberg Eugene 
Published: December 2004

AbstractEmulsan, the extracellular bioemulsifier of Acinetobacter RAG‐1, bound up to 0.9 μm of uranium per 1 mg emulsan. The dissociation constant for the emulsan‐uranium complex, K was 1.2 × 10−4M. Much larger amounts of uranium were bound to emulsan when the biopolymer occurred on hexadecane‐water interfaces. Under these conditions, more than 3.5 µm uranium were bound per 1 mg emulsan and the dissociation constant K was 5.1 × 10−5M. At pH 2, more than 90% of the uranium bound to emulsan on the hexadecane‐water interface was desorbed, while less than 10% bioemulsifier was released from the interface. The different binding parameters of emulsan when free in solution and while adsorbed onto the hexadecane water interface are discussed in view of potential applications and as a model system for studying the properties of an extracellular amphipathic polymer bound to a hydrophobic surface.
Kinetics of hydrolysis, oxidation, and adsorption during olive oil degradation by activated sludge
Authors: Hsu Ting‐Chi , Hanaki Keisuke , Matsumoto Junichiro 
Published: December 2004

AbstractKinetics of the degradation of olive oil by an acclimated activated sludge were studied. Kinetic constants for the lipid removal from the mixed liquor and for that from the supernatant and for the hydrolysis step were evaluated using Michelis‐Menten equations. The maximum specific reactions rates (vmax) and the saturation constants (Km) were vmax = 1.20 mg lipid mg−1 MLVSS day−1 and Km = 1290 mg/L for lipid removal from the mixed liquor; vmax = 1.54 mg lipid mg−1 MLVSS day−1 and Km = 801 mg/L for that from the supernatant; vmax = 1.57 mg olive oil mg−1 MLVSS day−1 and Km = 1750 mg/L for the hydrolysis of olive oil (where MLVSS refers to mixed liquor volatile suspended solids). The adsorption of olive oil by the activated sludge contributed to the lipid removal from the supernatant. The specific rate of this adsorption was also estimated. The hydrolysis, rather than the oxidation of free fatty acids, was the rate limiting step in the degradation of olive oil when the concentration of olive oil was lower than about 800 mg/L.
Operational stability of copolymerized enzymes at elevated temperatures
Authors: Mozhaev V. V. , Šikšnis V. A. , Torchilin V. P. , Martinek Karel 
Published: December 2004

AbstractThe copolymerization method of immobilization was used to obtain preparations of enzymes covalently incorporated in polyacrylamide gel. They possess properties making them suitable for practical use. First, the preparations are hundreds of times more stable against irreversible thermoinactivation than native enzymes. Second, on immobilization, the reversible conformational changes which also lower enzyme activity at elevated temperatures are completely suppressed. As a result, the temperatures of maximum activity for trypsin and α‐chymotrypsin covalently entrapped in polyacrylamide gel are 75 and 70°C, respectively—25 and 30°C higher than the corresponding values for the native enzymes. Therefore, the copolymerized enzyme preparations have a high operational stability at elevated temperatures.
Optimization of conditions and cell feeding procedures for alcohol fermentation
Authors: Ciftci T. , Constantinides A. , Wang S. S. 
Published: December 2004

AbstractAlcohol fermentation was studied with an emphasis on the separation of cell growth and alcohol production stages. Experiments were conducted to establish the optimal conditions for alcohol production in batch fermentations and to simulate continuous fermentations with cell feeding at various stages. It was found that the glucose concentration should be kept under 10% (w/v), and the temperature should be between 40 and 42.5°C for maximum specific alcohol productivity. If the cell concentration is increased, a decrease in specific alcohol productivity is observed. Higher cell concentrations are needed for higher final alcohol concentrations. Among the cell feeding procedures into alcohol production stages, a cocurrent design was found to be better than recycle and countercurrent designs.
Influence of oxygen on the growth of Saccharomyces cerevisiae in continuous culture
Authors: Furukawa K. , Heinzle E. , Dunn I. J. 
Published: December 2004

AbstractBaker's yeast, Saccharomyces cerevisiae, was investigated for the combined influence of dissolved oxygen and glucose concentration in continuous culture. A reactor was operated at a range of dilution rates (0.1, 0.2, 0.25, 0.27, and 3.0 h−1), above and below the critical value that separates the oxidative and fermentation regions. For each dilution rate (D), steady states were established at each of five to ten different dissolved oxygen concentrations (DO) in the range of 0.01−5 mg/L. The use of on‐line mass spectrometry facilitated the measurement of gaseous and dissolved O2, CO2, and ethanol. Intracellular carbohydrate, protein, RNA, DNA, lipid, and cytochrome concentrations were measured. Cell size measurements were reduced to specific surface areas. Cytochrome content showed up to 100% variation during a 20‐day period of adaptation at D = 0.2 h−1 to low DO. Eventually, the culture behaved the same at DO = 0.05 mg/L as it did initially at 3 mg/L. At D = 0.2, 0.25, and 0.27 h−1, the transition between oxidation and fermentation was characterized by a critical DO which decreased with decreasing D. The X‐D curves were shifted such that the critical D value was reduced with decreasing DO. Specific oxygen update rates varied with DO according to the saturation kinetics. Specific cell surface areas increased with decreasing DO. Cytochrome content generally decreased with decreasing DO, and Q could be linearly related to the total cytochrome content, which exhibited a maximum at D = 0.27 h−1.
A new process combining adsorption and enzyme reaction for producing higher‐fructose syrup
Authors: Hashimoto Kenji , Adachi Shuji , Noujima Hiromitsu , Ueda Yasuo 
Published: December 2004

AbstractA process for producing a higher‐fructose syrup containing more than 50% fructose was developed that involves a new system combining selective adsorption of fructose and an immobilized glucose isomerase reaction. Continuous countercurrent contact of the liquid stream with the solid adsorbent is simulated by advancing adsorption columns against the fixed inlets and outlet of liquid streams without actual movement of the solid adsorbent, while the immobilized enzyme reactors are stationary. Two mathematical models, an intermittent moving‐bed and a continuous moving‐bed model, are presented for calculation the concentration profiles of glucose and fructose in the system. The validity of the models is experimentally confirmed, and a criterion for good production in the system is presented. This system requires less desorbent than a process using a fixed‐bed adsorber and a simulated moving‐bed process to produce the syrup with 45−65% fructose content, the level desired in food manufacture.
Competition of two microbial populations for a single resource in a chemostat when one of them exhibits wall attachment
Authors: Baltzis Basil C. , Fredrickson A. G. 
Published: December 2004

AbstractIt is known that two microbial populations competing for a single resource in a homogeneous environment with time‐invariant inputs cannot coexist in a steady state. The case where two microbial populations compete for a single resource in a chemostat but one of them exhibits attachment to the chemostat walls is studied theoretically. Because of the cells' attachment to the walls, the environment is no longer homogeneous. The present article considers the case where the attached cells form no more than a monolayer. Other situations occur, often frequently, but we do not consider them here. Two models are used to represent the attachment to the walls: the Topiwala‐Hamer model and a model which assumes that the attachment of microbial cells to the solid surfaces is a reversible process. The first model does not allow the population that exhibits wall attachment to wash out from the chemostat, in contrast to the second model (which nevertheless reduces to the first one in the limit). It has been found that in most of the possible cases for both models, the two competitors can coexist in a stable steady state for a wide range of the operating parameters space. The results of the stability analysis are discussed and analytical expressions for the conditions and the boundaries of the domains of stable coexistence are given for all the possible situations that may arise.
Enzyme immobilization on palmityl–sepharose
Authors: Nemat‐Gorgani Mohsen , Karimian Khashayar 
Published: December 2004

AbstractEnzymes adsorbed on palmityl‐substituted Sepharose 4B by hydrophobic interactions have been used in reactor‐type experiments. Results presented on immobilized glutamate dehydrogenase, trypsin, α‐chymotrypsin, and amyloglucosidase indicate possible potential of the method for continuous catalytic operations. Glutamate dehydrogenase used as a model allosteric enzyme was found to retain its allosteric properties after binding to the absorbent in the form of column or suspension. Thermal stabilities of glutamate dehydrogenase and α‐chymotrypsin were significantly decreased upon adsorption, while that of trypsin was apparently unaltered. Results are discussed in terms of specific interactions involving palmityl residues present on the matrix. Relevance of these observations to in vivo processes are also discussed.
Conversion of organic acids to h2 by Rhodospirillaceae grown with glutamate or dinitrogen as nitrogen source
Authors: Segers Ludovik , Verstraete Willy 
Published: December 2004

AbstractAxenic cultures of Rhodopseudomonas capsulata. Rhodospirillum rubrum, and Rhodomicrobium vannielii grown with glutamate as the nitrogen source converted lactate, acetate, and butyrate to H2 and CO2. Conversion rates ranged from 100 to 926 mL H2 L day−1 (where Lr is the reactor contents), and efficiencies varied from 23 to 100% When grown with N2, conversion rates up to 760 mL H2 L day−1 and efficiencies up to 100%were achieved. Upon aging, cultures appear to rapidly increase in hydrogen uptake activity and furthermore decrease in nitrogenase activity, both factors leading to a slowdown of hydrogen production. This was particularly the case for diazotrophically grown photobacteria.
The ejector‐loop fermenter: Description and performance of the apparatus
Authors: Moresi Mauro , Bartolo Gianturco Gian , Sebastiani Enzo 
Published: December 2004

AbstractA novel fermentation unit, the ejector‐loop fermenter (ELF), consisting of an outer‐loop tower fermenter, a centrifugal pump, a plate‐heat exchanger, and a gas‐liquid ejector, was designed and constructed. Aeration was achieved by continuously recirculating the fermentation medium through two different nozzle devices instead of using the traditional expensive air compressor. By carrying out a whey fermentation with Kluyveromyces fragilis as the test organism, either in the ELF or in conventional stirred fermenter, it was possible to confirm that the high sheat streses and mixing shock occurring in the ejector nozzle and diffuser sections did not affect microbial growth. Within the range of experimental power consumption per unit volume (‐0.1–5 kW/m3), the oxygen transfer capability of the ELF per unit power input was found to vary from 1 to 2.5 kg O2 kW−1h−1. Moreover, it is shown that there is suficient room for improvement in the performance of the ELF unit by care fully designing the aeration device. In fact, at constant volumetric oxygen transfer coefficient, the power consumpotion per unit volume in a 4‐mm nozzle was found to be about 40% less than that in a 6‐mm nozzle.
Enzymic saccharification of sugarcane bagasse pretreated by autohydrolysis–steam explosion
Authors: Dekker R. F. H. , Wallis A. F. A. 
Published: December 2004

AbstractPretreatment of bagasse by autohydrolysis at 200°C for 4 min and explosive defibration resulted in the solubilization of 90% of the hemicellulose (a heteroxylan) and in the production of a pulp that was highly susceptible to hydrolysis by cellulases from Trichoderma reesei C‐30 and QM 9414, and by a comercial preparation, Meicelase. Saccharification yields of 50% resulted after 24 h at 50°C (pH 5.0) in enzymic digests containing 10% (w/v) bagasse pulps and 20 filter paper cellulase units (FPU). Saccharifications could be increased to more than 80% at 24 h by the addition of exogenous β‐glucosidase from Aspergillus niger. The crystallinity of cellulose in bagasse remained unchanged following autohydrolysis‐explosion and did not appear to hinder the rate or extent of hydrolysis of cellulose. Autohydrolysis‐exploded pulps extracted with alkali or ethanol to remove lignin resulted in lowere conversions of cellulose (28–36% after 25 h) than unextracted pulps. Alkali extracted pulps arising from autohydrolysis times of more than 10 min at 200°C were less susceptible to enzymic hydrolysis than unextracted pulps and alkali‐extracted pulps arising from short autohydrolysis times (e.g., 2 min at 200°C). Autohydrolysis‐explosion was as effective a pretreatment method as 0.25M NaOH (70°C/2 h) both yielded pulps that resulted in high cellulose conversions with T. reesei cellulase preparations and Meicelase. Supplementation of T. reesei C‐30 cellulose preparations with A. niger β‐glucosidases was effective in promoting the conversion of cellulose into glucose. A ration of FPU to β‐glucosidase of 1:1.25 was the minimum requirement to achieve more than 80% conversion of cellulose into glucose within 24 h. Other factors which influenced the extent of saccharification of autohydrolysis‐exploded bagasse pulps were the enzyme‐substrate ratio, the substrate concentration, and the saccharification mode.
Kinetics of organic compound removal from waste gases with a biological filter
Authors: Ottengraf S. P. P. , Van Den Oever A. H. C. 
Published: December 2004

AbstractIn order to eliminate organic pollutants in waste gases, a biological filter bed technique has been developed, with a high self‐regenerating capacity and a low pressure drop. The bed consists of an appropriate filling material (mainly peat compost), in order to let the microorganisms grow on the solid surface and to supply them with inorganic nutrients. Most organic compounds are oxidized to carbon dioxide and water. The compositions of the solid phase and the viable organisms present are such that aging is prevented, as a result of which a relatively high activity can be maintained during a long period of time (years). Experiments have been carried out in laboratory‐scale columns with composite gas mixtures at varied concentrations and superficial gas velocities. The (macro) kinetics of the elimination processes have been studied, which enables the prediction of the elimination capacity of the filter bed.
Mixing and oxygen transfer in conventional stirred fermentors
Authors: Manfredini R. , Cavallera V. , Marini L. , Donati G. 
Published: December 2004

AbstractA set of experiments has been performed in an industrial 112 m3 fermentor in order to get a complete map of oxygen concentration and temperature distribution in the system. Five fermentations of non‐Newtonian broths of two different strains, in various operating conditions, were examined. A simple model has been developed which takes into account both the mixing and the mass‐transfer properties of the fermentor, and a dimensionless parameter has been identified which is sufficient to characterize the oxygen axial distribution in the reactor in any operating condition.