bluuebunny/crossref_metadata_2025 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

The 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

Bamboo 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

Various 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

A 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

The 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

Emulsan, 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

Kinetics 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

The 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.
Precipitation, chelation, and the availability of metals as nutrients in anaerobic digestion. I. Methodology
Authors: Callander I. J. , Barford J. P.
Published: December 2004

A methodology has been developed for the quantitative assessments of the individual effects of precipitation and chelation of metal ions in an anaerobic digester.
Optimization of conditions and cell feeding procedures for alcohol fermentation
Authors: Ciftci T. , Constantinides A. , Wang S. S.
Published: December 2004

Alcohol 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

Baker'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

A 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

It 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

Enzymes 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

Axenic 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

A 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

Pretreatment 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

In 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

A 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.
Intensive use of biomass feedstock in ethanol conversion: The alcohol–water, vapor‐phase separation
Authors: Robertson George H. , Doyle Larry R. , Pavlath Attila E.
Published: December 2004

Fermentation of ethanol in a system whereby the biomass is used intensively (both to separate alcohol from water by vapor phase adsorption and to serve as the feedstock) is shown to be possible on theoretical grounds when the biomass is grain. The rationale for a vapor‐phase adsorption process as an alternative to distillation is shown to be energetically valid above 84 wt % ethanol. The capacity of grain in new vapor‐phase ambient adsorption processes was estimated experimentally with the finding that sufficient capacity exists for the intensive use but that the adsorption is dynamically controlled so that the grain form and particle size are important. Pretreatments such as explosive dehydration improve the transfer of water to the grain in adsorption with potential improvement in the efficiency of liquefaction and saccharification. At room temperature, these sorbents are not perfectly selective for water but adsorb ethanol which will be carried to the liquefaction, saccharification, and fermentation with the feedstock.
Immobilization of Saccharomyces cerevisiae by adhesion: Treatment of the cells by Al ions
Authors: Van Haecht J. L. , Bolipombo M. , Rouxhet P. G.
Published: December 2004

The adsorption of aluminum ions by Saccharomyces cerevisiae has been investigated by determining adsorption isotherms and electrophoretic mobility. The adsorption of aluminum ensures a neutralization of the cell surface charge and allows adhesion of the cells to glass and polycarbonate. Glass slides have been taken as a negatively charged model support, allowing the authors to study in detail the process of adhesion. The cells are simply pretreated by an aluminum solution near pH 4. Bringing the Al‐pretreated cells in contact with the support by sedimentation and washing the support and sediment makes it possible to obtain a single, dense, regular layer of cells adhering strongly to the support. Adhesion can also be obtained from a suspension flowing parallel to a vertical support, provided the flow velocity is sufficiently small; the amount of cells immobilized per unit support area is about one‐half that obtained by sedimentation. The immobilized cells show a specific activity for ethanol production from glucose which is similar to cells in suspension.
Studies on the mechanism of alkaline peroxide delignification of agricultural residues
Authors: Gould J. Michael
Published: December 2004

Alkaline solutions of hydrogen peroxide partially delignify wheat straw and other lignocellulosic materials, leaving a cellulosic residue that is highly susceptible to enzymatic digestion by cellulase. The delignification reaction is strongly dependent upon the pH of the reaction mixture, with an optimum at pH 11.5–11.6, pKa for the dissociation H2O2 ⇌ H+ + HOO−. The data are consistent with a mechanism in which H2O2 decomposition products such as ·OH and O·, rather than H2O2 or HOO−, are the primary lignin oxidizing species. During the course of the delignification reaction, O2 is evolved from the reaction mixture indicating active H2O2 decomposition. At a given concentration of H2O2, the rate of O2 evolution is proportional to the amount of lignocellulosic substrate present in the reaction mixture. However, the total amount of O2 evolved is inversely proportional to the amount of substrate present, indicating that some of the peroxide oxygen becomes incorporated into lignin degradation products. The amount of peroxide oxygen incorporated can range as high as 2 O2 per lignin C9 unit, depending upon the initial concentration of lignocellulosic substrate.
Studies on batch and continuous cultures of Botryococcus braunii: Hydrocarbon production in relation to physiological state, cell ultrastructure, and phosphate nutrition
Authors: Casadevall E. , Dif D. , Largeau C. , Gudin C. , Chaumont D. , Desanti O.
Published: December 2004

The growth of the hydrocarbon‐rich alga Botryococcus braunii was studied under “air‐lift” conditions using batch and continuous cultures. Large variations in the physiological state of B. braunii were achieved in batch cultures and in continuous cultures with various dilution rates. The possible effects of these variations upon hydrocarbons (nature, relative abundance, location, level, productivity) and also on the production of exocellular polysaccharides were examined. The relationships between the physiological state of B. braunii and its hydrocarbon and polysaccharide production were discussed and compared with those generally observed in unicellular algae. The factors giving rise to the transition from high to low productivity stages were considered. To this end we examined, at first, the variations in cell ultrastructure and the resulting degeneration occurring during batch cultures. Afterward the parallel changes in some parameters of the medium (pH, phosphate level) were determined and their possible relationships with B. braunii growth and hydrocarbon production were discussed. The main features of phosphate nutrition in B. braunii and its effects on hydrocarbons were finally examined.
Application of a two‐compartment model to the wall growth of Pelobacter acidigallici under continuous culture conditions
Authors: Kreikenbohm Rainer , Stephan Wolfgang
Published: December 2004

Continuous cultivation of Pelobacter acidigallici on gallic acid is accompanied by biofilm formation. Steady states can be obtained at dilution rates nearly twice the maximum growth rate. A two‐compartment model is presented which allows us to determine rate constants of attachment and detachment. The model is based on the assumption that the biofilm is fully penetrated by the substrate. At high dilution rates the outcome of our experiments is mainly determined by the attachment rate. The influence of the thickness of the biofilm is discussed in order to demonstrate the limitations of the model.
Modeling alkali consumption and digestibility improvement from alkaline treatment of wheat straw
Authors: Pavlostathis Spyros G. , Gossett James M.
Published: December 2004

The alkali consumption during alkaline treatment of wheat straw at ambient temperature was measured as a function of time, solids concentration, and alkali concentration. The maximum measured alkali consumption was 5.5 g NaOH/100 g TS over a period of 30 days of treatment. Chemical functional groups (e.g., acyl and carboxyl groups) were measured and compared with the observed alkali consumption. The kinetics of alkali consumption were studied and a model was developed which predicts alkali consumption reasonably well. Use of this model was made to predict biodegradability of alkali‐treated wheat straw, since a strong correlation was found to exist between alkali consumption and observed biodegradability. The method of bioconversion used was anaerobic digestion for methane production.
Application of scale‐down experiments in the study of kinetics of oxytetracycline biosynthesis
Authors: Bošsnjak Marijan , Stroj Alešs , Caurčcica Miljenko , Adamovica Vlasta , Glunčcica Zdravka , Bravar Danica , Johanides Vera
Published: December 2004

Scale‐down experiments in antibiotic biosynthesis were performed by transferring the corresponding amounts of fermentation broth from industrial to laboratory and pilot‐plant fermentors where the cultivation process was continued at different cultivation conditions. A previously proposed mathematical model was used to explain the experimental results. The effects of temperature, agitation‐aeration intensity, and medium addition during the process were investigated. Computer simulation data were fitted to the experimental data, and good agreement was found. As a consequence of increasing temperature up to 37°C, increases in the specific growth and autolysis rates as well as the specific rates of antibiotic synthesis and carbohydrate utilization were in evidence. Temperature increases of up to 40°C caused a lower oxytetracycline yield. The effect of increased oxygen transfer rate on oxytetracycline biosynthesis was more pronounced at higher temperatures than at lower cultivation temperatures. Culture differentiation (strain segregation) was also studied; it was found that the increased cultivation temperature could be favorable for the growth of biomass active in oxytetracycline biosynthesis. Results of experiments at the pilot‐plant scale showed that fed batch and repeated fed batch cultures could be successfully applied and the period of intensive antibiotic synthesis could be prolonged significantly.
Preparation of optically activeD‐arylglycines for use as side chains for semisynthetic penicillins and cephalosporins using immobilized subtilisins in two‐phase systems
Authors: Schutt Hermann , Schmidt‐Kastner Günter , Arens Alfred , Preiss Michael
Published: December 2004

Optically activeD‐arylglycines, which are of interest for preparation of semisynthetic penicillins and cephalosporins, were isolated from the racemic mixtures of their derivatives using immobilized proteolytic enzyme subtilisin (EC No. 3.4.4. 16). The performance of these reactions in two‐phase systems, consisting of water and an immiscible organic solvent, improved the yield, purity, and economics of the process by increasing the substrate solubility and reducing the rate of nonenzymatic hydrolysis. The proportion of the organic phase can be as much as 75% of the overall volume without seriously impairing the enzymatic activity. The optically pureD‐andL‐arylglycines were liberated from theirD‐ andL‐derivatives by acid hydrolysis. The substituent influence of the various arylglycine derivatives on the rate of the enzymatic cleavage reaction was investigated.
Performance of hydrophobic chromatography in purification of α‐amylase
Authors: Sada Eizo , Katoh Shigeo , Inoue Tsuneo , Shiozawa Masami
Published: December 2004

Hydrophobic ligands were introduced onto agarose beads, and the adsorption capacity of the beads was measured. The adsorption capacity increased with increase in the carbon number of the ligand, ionic strength of the buffer solution, and temperature. Crude α‐amylase was purified with these hydrophobic adsorbents and the breakthrough and elution curves were estimated based on the mass transfer theory. Under strongly hydrophobic conditions, impurities contained in crude feeds and the lack of uniformity of packing caused by aggregation of beads affected adsorption and elution behaviors.
Purification and characterization of endo‐xylanases from Aspergillus niger. II. An enzyme of pl 4.5
Authors: Shei Juliana C. , Fratzke Alfred R. , Frederick Mary M. , Frederick James R. , Reilly Peter J.
Published: December 2004

A homogeneous endo‐xylanase (1,4‐β‐D‐xylan xylanohydrolase, EC 3.2.1.8) was obtained from a crude Aspergillus niger pentosanase by chromatography with Ultrogel AcA 54, SP‐Sephadex C‐25 at pH 4.5, DEAE‐Sephadex A‐25 at pH 5.4, Sephadex G‐50, and SP‐Sephadex C‐25 with a gradient from pH 2.8 to pH 4.6. It was much more active on soluble than on insoluble xylan, yielding large amounts of unreacted xylan and a mixture of oligosaccharides with chain lengths from two to six. No xylose or L‐arabinose was produced. There was high activity on a xylopentaose through xylononaose mixture, but not on xylobiose, xylotriose, or xylotetraose. The enzyme had slight activity on untreated cellulose, carboxymethylcellulose, and pectin. Molecular weight was ca. 1.4 × 104, with an isoelectric point of 4.5 and an amino acid profile high in acidic but low in sulfur‐containing residues. In a 25‐min assay at pH 4.7, this endo‐xylanase was most active at 45°C, with an activation energy from 5 to 35°C of 33.3 kJ/mol. The optimum pH for activity was 4.9. Decay in buffer was first order, with an activation energy at pH 4.7 from 48 to 53°C of 460 kJ/mol. Optimum pH for stability was about 5.6, where the half‐life at 48°C in buffer was ca. 40 h.
Feast/famine growth environments and activated sludge population selection
Authors: Chiesa Steven C. , Irvine Robert L. , Manning John F.
Published: December 2004

The effect of feast/famine growth conditions on activated sludge cultures indicates that nonfilamentous cultures can be selected by providing proper substrate gradients and extended periods of endogenous metablism. Reactor operating strategies providing intermittently high substrate concentrations result in cultures characterized by high peak substrate and oxygen uptake activities, rapid settling rates, and high resistance to starvation. Sludge settleability can be manipulated using controlled variations in growth environment with corresponding changes noted in sludge activity. In combination with the low net growth rates associated with activated sludge systems, feast/famine environments would logically convey a selection advantage to microbes capable of readily assimilating substrate materials and maintaining viability during extended starvation periods.
Malic acid production by an electrochemical reduction system combined with the use of diaphorase and methylviologen
Authors: Maeda H. , Kajiwara S.
Published: December 2004

A regenerating reaction combined with the use of native malate dehydrogenase, native diaphorase, methylviologen, NAD, oxalacetic acid as the substrate and lipoamide as a stabilizer was carried out in the presence of electrolysis. Consequently, malic acid was efficiently produced from oxalacetic acid in the regenerating reaction. A glassy carbon bead electrode was used as a cathode. Twenty four milliamperes were passed at a rotation speed of 500 rpm, 29.8 ± 0.3°C and −1.0 V. It was found that lipoamide has a stabilizing effect on malate dehydrogenase and diaphorase. Low concentration (50 μM) of NAD was also effective for the stabilization of malate dehydrogenase. NADH regeneration activity based on malic acid production rate was 4.7 U/mg of the enzyme protein of the commercial diaphorase preparation. The current efficiency was more than 74%, compared with the theoretical yield, in the presence of enough oxalacetic acid.
Use of cell affinity chromatography for separation of lymphocyte subpopulations
Authors: Hertz C. M. , Graves D. J. , Lauffenburger D. A. , Serota F. T.
Published: December 2004

We describe the use of affinity chromatography for separation of cell populations that do not differ significantly with respect to gross physical properties such as size, density, or charge. Cell affinity chromatography exploits differences in cell surface macromolecules by passage of mixtures of cell populations through a column containing beads to which are attached chemical ligands with specific binding affinity for particular cell surface receptors. In this article we focus on the application of this concept to separation of mature T lymphocytes from peripheral blood. This serves as a model for the separation of these cells from bone marrow in order to prevent graft‐vs.‐host disease in bone marrow transplantation. However, the concept of cell affinity chromatography should find more general widespread utility in a variety of biotechnological applications. Thus, we introduce a simple theoretical framework which is necessary in order to understand the results that might be expected in any given situation. Finally, we use this theory to provide a tentative explanation for experimental observation of the effects of temperature and flowrate on the degree of separation achieved for our current pplication.
Structured modeling of the anaerobic digestion of biomass particulates
Authors: Bryers J. D.
Published: December 2004

Anaerobic digestion of biological organic particulates to methane has been described by a structured mathematical model based on multiple‐reaction stoichiometry, conventional material balances, and liquid phase equilibrium chemistry. A general stoichiometric treatment for any set of multiple biological reactions is derived based on a unit mass of oxggen equivalents of the reactions limiting substrate. The model agrees well with two existing experimental studies of anaerobic digestion of biomass particulates. Hypothetical computer simulations are presented to illustrate possible instabilities of the anaerobic process under various operating scenarios.
Kinetics of chitinase production. I. Chitin hydrolysis
Authors: Young Manuel E. , Bell Richard L. , Carroad Paul A.
Published: December 2004

As part of the development of a comprehensive mathematical model for chitinase production by Serratia marcescens QMB 1466 growing on chitin, the different mass transport and kinetic steps involved during chitin hydrolysis were studied. The experimental results for the hydrolysis of chitin by a crude preparation of chitinase show a system kinetically limited by the overall rate of chitin hydrolysis. This rate is linearly related to the concentration of enzyme adsorbed on the chitin particle. Adsorbed and bulk enzyme concentration were found to be related through a Langmuir type of isotherm.
Performance of an upflow anaerobic reactor combining a sludge blanket and a filter treating sugar waste
Authors: Guiot S. R. , van den Berg L.
Published: December 2004

A new hybrid reactor, the upflow blanket filter (UBF), which combined on open volume in the bottom two‐thirds of the reactor for a sludge blanket and submerged plastic rings (Flexiring, Koch Inc., 235 m2/m3) in the upper one‐third of the reactor volume, was studied. This UBF reactor was operated at 27°C at loading rates varying from 5 to 51 g chemical oxygen demand (COD)/L d with soluble sugar wastewater (2500 mg COD/L). Maximum removal rates of 34 g COD/L d and CH4 production rates of 7 vol/vol d [standard temperature and pressure (STP)] were obtained. The biomass activity was about 1.2 g COD/g volatile suspended solids per day. Conversion (based on effluent soluble COD) was over 93% with loading rates up to 26 g COD/L d. At higher loading rates conversion decreased rapidly. The packing was very efficient in retaining biomass.
Mathematical simulation of a biofilm process
Authors: Benefield Larry , Molz Fred
Published: December 2004

A mathematical model has been developed for a fixed‐film biological process (film flow over a flat plate) that describes bulk liquid transport, diffusional transport of oxygen and organics across a stagnant film, diffusional transport of oxygen and organics into the biofilm, biochemical reactions by the individual cells within the biofilm, biofilm growth, and cell density changes within the biofilm due to cellular decay. Simulation studies are presented to show how contact time and diffusion layer thickness affect process performance.
Modeling of enzyme immobilization in porous membranes
Authors: Hossain Md. M. , Do D. D.
Published: December 2004

This article deals with the mathematical modeling of the process of enzyme immobilization in porous membranes. During the initial period, an analytical solution is available to extract the rate constant for immobilization. Beyond this period, the model equations are solved numerically to yield the transient response of the enzyme concentration in the immobilizing solution and also the evolution of the enzyme loading profile inside the membrane. It is found that the immobilization practically ceases even through the attachment sites are still available within the membrane.
Importance of agitation in acetone‐butanol fermentation
Authors: Yerushalmi Laleh , Volesky Bohumil
Published: December 2004

The specific rates of anaerobic solvent production byClostridium acetobutylicumincreased with increasing fermentor impeller speed from 190 to 340 rpm (NRe= 3.93 × 104). The maximum values were 5.54, 3.85, and 0.8 mmol/h · g cell for butanol, acetone, and ethanol, respectively. Corresponding rates for respective gases produced were 11.60 and 15.88 mmol/h · g cell for H2and CO2. Further increases in agitation speed resulted in generally decreasing specific production rates to the point of inactive fermentation at 560 rpm. A competition observed between the cellular subsystems for butanol + butyric acid and biomass biosynthesis was evaluated through expressing the energetic yield coefficients. An imbalance between the production and outflux of the former metabolites is apparently further enhanced by a mechanical damage of the cells at high shear rates. A correlation was developed between the production of gases and solvents pointing at both H2‐to‐solvent as well as CO2‐to‐solvent ratios following the same pattern, peaking at 410 rpm.
Biotransformation of 3‐methoxy‐8,14‐seco‐1,3,5(10),9(11) estratetraen‐14,17‐dione (secodione) to its 17β‐hydroxy derivative (secol) using immobilized yeast cells (Pichia farinosa Y‐118)
Authors: Bihari Vinod , Joshi A. K. , Khan A. W. , Vora V. C.
Published: December 2004

The yeast cells of Pichia farinosa Y‐118 were immobilized in polyacrylamide gel and used for 17 β‐oxidoreduction of secondione to secol. The loss of hydroxysteroid oxidoreductase activity of cells was found to be insignificant during immobilization. The preparation exhibited greater temperature stability as compared to free cells. The ratio of reaction volume to the volume of immobilized biocatalyst in the range 1.4−1.9 was found to be satisfactory for the reaction conditions studied. This ratio played a significant role in the stability of the catalyst particle, since beyond a critical value the disintegration of gel granules was rapid resulting in sharp decline of activity. The immobilized cell preparation could be used 50 times over a period of 100 days without loss of activity. However, the activity declined in further reuses, leaving the preparation 50 and 35% active after its 60th and 70th uses, respectively.
Thermophilic anaerobic digestion of high strength wastewaters
Authors: Wiegant W. M. , Claassen J. A. , Lettinga G.
Published: December 2004

Investigations on the thermophilic anaerobic treatment of high‐strength wastewaters (14‐65 kg COD/m3) are presented. Vinasse, the wastewater of alcohol distilleries, was used as an example of such wastewaters. Semicontinuously fed digestion experiments at high retention times revealed that the effluent quality of digestion at 55°C is comparable with that at 30°C at similar loading rates. The amount of methane formed per kilogram of vinasse drops almost linearly with increasing vinasse concentrations. This can be attributed to increasing concentrations of inhibitory compounds, resulting in increasing volatile fatty acid (VFA) concentrations in the effluent. The treatment of vinasse was also investigated using upflow anaerobic sludge blanket (UASB) reactors. Thermophilic granular sludge, cultivated on sucrose, was used as seed material. The sludge required a 4‐month adaptation period, during which the size of the sludge granules decreased significantly. However, the settling characteristics remained satisfactory. After adaptation, high loading and methane generation rates could be accommodated at satisfactory treatment efficiencies, namely, 86.4 kg COD/m3 day and 26 m3 CH4(STP)/m3 day, respectively. As in the semicontinuously fed digesters, the effluent VFA concentrations were virtually independent of the loading rates applied, indicating that the toxicity of the vinasse is more important than the loading rate in determining the efficiency of the conversion of vinasse to methane.
Effects of solute hydrophobicity and phospholipid composition on permeability of composite membranes containing phospholipids
Authors: Sada Eizo , Katoh Shigeo , Terashima Masaaki , Yamana Shuichi , Ueyama Nobuhiko , Nagaya Mitsuru
Published: December 2004

Permeabilities of several solutes through the composite membranes containing phospholipids have been measured. They were inversely proportional to the content of the phospholipids in the membrane. Both the permeability of solutes and the degree of permeability change around the phase transition temperature of the phospholipids for the hydrophobic solutes such as n‐butanol and salicylamide were larger than those for the hydrophilic solutes such as amino acids and pyridoxine. These results suggest thatthe permeation path of hydrophobic solutes is different from that of hydrophilic ones. The addition of phosphatidyl ethanolamine, phosphatidyl serine, or phosphatidic acid to the composite membrane influenced the solute permeability due to the introduced negative charge and/or the change in the molecular packing of phospholipid.