bluuebunny/crossref_metadata_2025_split huggingface dataset:
Photochemical energy conversion system using immobilized chloroplasts
Authors: Kayano Hiromichi , Matsunga Tadashi , Karube Isao , Suzuki Shuichi 
Published: December 2004

AbstractImmobilized chloroplasts and Clostridium butyricum were employed for a photochemical energy conversion system. Spinach chloroplasts were immobilized in 2% agar gel. The optimum temperature of immobilized chloroplasts was 30°C. The maximum activity was obtained in the phosphate buffer solution (pH 8.0) containing 8μM of ferredoxin under an N2 bubbling condition. Hydrogen was evolved under illumination by immobilized chloroplasts and C. butyricum. Hydrogen produced by this system was applied to a hydrogen‐oxygen fuel cell. Photoinduced current was obtained from this photochemical energy conversion system. A photocurrent of 0.4−1.5 mA was continuously obtained for 4 h. The conversion ratio from hydrogen to current was 80−100%.
Bioconversion of wheat straw cellulose/hemicellulose to ethanol by Saccharomyces uvarum and Pachysolen tannophilus
Authors: Detroy R. W. , Cunningham R. L. , Bothast R. J. , Bagby M. O. , Herman A. 
Published: December 2004

AbstractThe information presented in this publication represents current research findings on the production of glucose and xylose from straw and subsequent direct fermentation of both sugars to ethanol. Agricultural straw was subjected to thermal or alkali pulping prior to enzymatic saccharification. When wheat straw (WS) was treated at 170°C for 30–60 min at a water‐to‐solids ratio of 7:1, the yield of cellulosic pulp was 70–82%. A sodium hydroxide extration yielded a 60% cellulosic pulp and a hemicellulosic fraction available for fermentation to ethanol. The cellulosic pulps were subjected to cellulase hydrolysis at 55°C for production of sugars to support a 6‐C fermentation. Hemicellulose was recovered from the liquor filtrates by acid/alcohol precipitation followed by acid hydrolysis to xylose for fermentation. Subsequent experiments have involved the fermentation of cellulosic and hemicelluosic hydrolysates to ethanol. Apparently these fermentations were inhibited by substances introduced by thermal and alkali treatment of the straws, because ethanol efficiencies of only 40–60% were achieved. Xylose from hydrolysis of wheat straw pentosans supported an ethanol fermentation by Pachysolen tannophilus strain NRRL 2460. This unusual yeast is capable of producing ethanol from both glucose and xylose. Ethanol yields were not maximal due to deleterious substances in the WS hydrolysates.
Optimization of biomass productivity and substrate utility of a hydrogen bacterium, Alcaligenes hydrogenophilus
Authors: Miura Yoshiharu , Okazaki Mitsuo , Ohi Kiyomoto , Nishimura Takashi , Komemushi Sadao 
Published: December 2004

AbstractOptimizations of cell productivity and utility of gaseous substrates were investigated for Alcaligenes hydrogenophilus. Theoretical analyses for the cell productivity and substrate utility were discussed in the light of experimental data. It was proved from the theoretical analyses that the maximum cell productivity was at the following conditions: D = 0.21 h−1, R1 ( = H2 partial pressure/O2 partial pressure) = 2.25 and R2 ( =CO2 partial pressure/O2 partial pressure) = 0.09, i.e., a molal ratio, H2:O2:CO2 = 67.4:29.9:2,7. The Condition which gave the maximum cell productivity also gave high utilities of gaseous substrates. The growth yield for oxygen increased with increasing R1 in chemostat culture, and the growth yield for hydrogen slightly increased with increasing R1. Theoretical cell productivity and substrate and substrate utility were in good agreement with experimental values, taking into account the change of growth yield for oxygen.
Effect of dithiocarbamates on cellulase activity in culture filtrates of Trichoderma reesei
Authors: Shirkot C. K. , Mann D. , Dhawan S. , Gupta A. K. , Gupta K. G. 
Published: December 2004

AbstractDifferent concentrations of tetramethylthiuram disulfide (TMTD), sodium dimethyldithiocarbamate (NaDDC), and zinc dimethyldithiocarbamate (ZnDDC) affected the amount of cellulase(s) activity in the culture of Trichoderma reesei. After eight days incubation at 28°C the greatest increase in Avicelase, CMCase, and β‐glucosidase over the control were observed at 0.1 ppm (TMTD) and 0.4 ppm (NaDDC and ZnDCC). There was decrease in the growth in the ZnDDC, but β‐glucosidase activity was reduced considerably. Total protein in the culture filtrate increased with the increase in cellulase(s) activity. No change in pH was observed at eight days incubation but pH increased (not exceeding 5.9) at 12 days incubation.
Studies on Scenedesmus acutus growth. I effect of autotrophic and mixotrophic conditions on the growth of Scenedesmus acutus
Authors: Shamala T. R. , Drawert F. , Leupold G. 
Published: December 2004

AbstractAmong sugars, glucose and mannose were found to be the most suitable substrates for mixotrophic growth, uptake of galactose and its influence on growth was negligible, and sucrose and fructose occupied intermediary positions. The optimum temperature for sugar uptake was 30°C, both under light and in darkness. Enhancement in the photosynthetic oxygen‐evolution rate, based on the utilization of substrates, was foremost in the presence of glucose, followed by mannose, sucrose, and fructose. Industrial by‐products such as sugarcane molasses also were utilized to increase the algal growth under mixotrophic conditions. A maximum yield in biomass was obtained subsequent to the combined supply of sugarcane molasses with carbon dioxide to indoor as well as outdoor mixotrophic cultures. Doubling the carbon dioxide supply alone above a certain level, under autotrophic and mixotrophic outdoor conditions, did not produce a pronounced increase in the algal growth rate. The results on autotrophic and mixotrophic growth variations are discussed in the article.
Comparative performance of biofilm reactor types
Authors: Rittmann B. E. 
Published: December 2004

AbstractDevelopment of a unified model of biofilm‐reactor kinetics is based on substrate‐utilization kinetics, mass transport, biofilm growth, and reactor analysis. The model is applied to steady‐state conditions for complete‐mix, fixed‐bed, and fluidized‐bed reactors with and without recycle. The results of modeling experiments demonstrate that simple loading factors and kinetic relationships are insufficient to describe the performance of a variety of biofilm processes. Instead, the interactions among utilization kinetics, biofilm growth, and reactor configuration determine the performance. For example, fluidized‐bed reactors can achieve superior performance to complete‐mix and fixed‐bed reactors because the biofilm is evenly distributed throughout the reactor while the liquid regime has plug‐flow characteristics. When it is possible, experimental results which demonstrate key concepts are presented.
The theory and design of aerobic biological treatment
Authors: Vavilin V. A. 
Published: December 2004

AbstractThe processing of numerous experimental data shows that the high‐level and rough treatments of multicomponent sewage water follow different laws. In the case of rough treatment, the classical Monod's model is fairly adequate to the experiment. High concentrations of a pollutant “saturate” the complex of microorganisms (activated sludge or biofilm) and the general oxidation process follows a zero order for the substrate. In the case of high‐level treatment, the model of an n order (n > 1) for the substrate is adequate to the experiment. Generalized models of aerobic treatment, independent of the reactor type (an aeration tank, trickling filter, rotating disk), are proposed.
Stability studies of immobilized enzyme stir rods
Authors: Hammons John L. , Coleman Geoffrey N. 
Published: December 2004

AbstractAlcohol dehydrogenase has been covalently attached to the surfaces of nylon stir rods. Several rod types have been evaluated in terms of their mixing efficiency and enzyme loading. Fluorometric monitoring of the rate of conversion of NAD to NADH serves as a measure of the reaction rate under varying conditions. The rate of reaction of the enzyme stir rods has been evaluated in terms of RPM, buffer concentration, NAD reagent concentration, and pH. The rate of reaction is seen to reach a plateau at higher stir rates, indicating a lack of diffusional hindrances. The reaction rate also begins to level off at phosphate buffer concentration of 0.1M to 0.15M. Saturating conditions are reached at an NAD concentration of 2.5mM. The optimum pH is found to be 9.0. The Stability of the covalent bond between the enzyme and the nylon has been assessed by comparing the bond strength to the energies of various disruptive forces to which the enzyme is exposed. Centrifugal, drag, and shear forces are shown to be insufficient to cause rupture of the bond. The stability to the immobilized enzyme preparation has been investigated under varying conditions of immobilization and use. No effect on activity loss was found for rotation rate or for continuous versus intermittent use. It was found that enhanced stability occurred for hydrolytic cleavage of the nylon, using nitric acid, as compared to nonhydrolytic cleavage. Hydrolytic cleavage also led to some degree of adsorption of the enzyme to the surface of the nylon. Thus, the possibility of increased stability to multipoint attachment of the enzyme is discussed. Possible cause of activity loss are discussed, as well as the extension of the enzyme stir rod to use in scale model reactor studies.
Role of phosphorus in activated sludge
Authors: Wu Yeun C. , Okrutny Mark S. 
Published: December 2004

AbstractMonod's kinetic model was used to correlate the specific growth rate of mixed activated sludge with the limiting substrate of phosphorus for both batch and continuous‐flow culture systems. In the batch reactor system, the specific growth rate varied from 0.092 to 0.617 h−1 and the saturation constant changed from 25.5 to 117.5 when the COD: P ratio was controlled within the range of 10 to 788 and at the temperature 25± 0.5°C. An inverse relationship between specific growth rate and cell yield was found. the maximum specific growth rate and the saturation constant obtained from this study were equal to 0.64 h−1 and 0.378mg/L, respectively. In the completely mixed continuous‐flow culture system, it was found that the substrate utilization, biological solids production, and sludge composition were markedly affected by the source of phosphorus available in the wastewater. The phosphorus‐limited activated sludge is normally high in carbohydrate content and low in protein content. Also, sludge organisms growth under the severely restricted phosphorus condition usually possess a large capsule. These capsulated carbohydrate‐like substances can be converted to cellular protein if the source of phosphorus is added. The values of cell yield in the continuous‐flow activated sludge system are predictable by the use of kinetic constants that are generated from batch culture studies.
Distribution and behavior of sludge in upflow reactors for anaerobic treatment of wastewater
Authors: Buijs C. , Heertjes P. M. , Van Der Meer R. R. 
Published: December 2004

AbstractA model has been developed and experimentally checked for the physical behavior of sludge in the blanket in upflow reactors. The model is based on the mass balance for the sludge in the blanket, and can be used to predict the distribution of sludge in an upflow reactor in relation with the gas production, sludge settling characteristics, and the linear fluid velocity in the reactor. The quantitative values of the transport factors that are a measure of the efficiency of the transport of sludge by the fluid streams occurring in the reactor were determined experimentally in reactors of 30‐ and 200‐m3 volumes. As this was done for wastewater containing lower fatty acids as the main organic pollutants and for sludge with good settling characteristics, the predictive value of the model is limited. It may be used for the second (methane forming) step of anaerobic treatment of wastewater.
A filter fermenter—apparatus and control equipment
Authors: Dostálek Milan , Häggstrom Margareta 
Published: December 2004

AbstractLaboratory equipment for cultivation of microorganisms with the removal of cell‐free medium is described. Separation is accomplished by filtration through a membrane which is built into a top‐driven fermenter. A system is presented which controls the flow rate by automatic cleaning of the filter. Flow schemes for batch and continuous fermentations are shown. The filter fermenter is useful when studying continuous culture with feedback of biomass or processes where growth or product formation rates are influenced by inhibitory metabolites. Results are presented from experiments with Saccharomyces cerevisiae, Pedicoccus pentosaceus, and Zymomonas mobilis.
Stereospecific hydrolysis by soluble and immobilized lipases
Authors: Lavayre J. , Verrier J. , Baratti J. 
Published: December 2004

AbstractStereospecific hydrolysis of insoluble monoesters by lipases are reported. Among the lipases tested, porcine pancreatic lipase was the most stereospecific when acting on 3‐chloro–2‐methyl propanol propionate. When the chain length of the acid was enhanced, the stereospecificity decreased. Initial rate measurements analysis concluded that the observed stereospecificity was the result of different catalytic constants rather than different Michaelis constants. From these results, methods were derived for the preparation of l‐ or d‐3‐chloro–2‐methylpropanol (an intermediary in the synthesis of levomepromasine) based on the hydrolysis of esters by soluble or immobilized lipases.
Interactions between amino‐acid‐degrading bacteria and methanogenic bacteria in anaerobic digestion
Authors: Nagase Michihiko , Matsuo Tomonori 
Published: December 2004

AbstractThe degradation of amino acids in anaerobic digestion was examined in terms of the interactions between amino‐acid‐degrading bacteria and methanogenic bacteria. Certain amino acids were degraded oxidatively by dehydrogenation, with methanogenic bacteria acting as H2 acceptors. The inhibition of methanogenesis by chloroform also inhibited the degradation of these amino acids and/or caused variations in the composition of volatile acids produced from them. The presence of glycine reduced the inhibitory effect caused by chloroform, probably because glycine acted as an H2 acceptor in place of methanogenic bacteria. This fact suggested that the coupled oxidation‐reduction reactions between two amino acids—one acting as the H2 donor and the other acting as the H2 acceptor–may occur in the anaerobic digestion of proteins or amino‐acid mixtures. The conversion of some proteins to volatile acids was not affected when methanogenesis was inhibited by chloroform. This suggested that the component amino acids of proteins may be degraded by the coupled oxidation‐reduction reactions and that the degradation of proteins may not be dependent on the activity of methanogenic bacteria as H2 acceptors.
Structural properties of cellulose and cellulase reaction mechanism
Authors: Lee Sun Bok , Kim I. H. , Ryu Dewey D. Y. , Taguchi H. 
Published: December 2004

AbstractThe effects of structural properties and their changes during cellulose hydrolysis on the enzymatic hydrolysis rate have been studied from the reaction mechanism point of view. Important findings are the following: (1) The crystallinity index (CrI) of partially crystalline cellulose increases as the hydrolysis reaction proceeds, and a significant slowing down of the reaction rate during the enzymatic hydrolysis is, in large part, attributable to this structural change of cellulose substrate. (2) The crystallinity of completely disordered cellulose, like phosphoric‐acid‐treated cellulose, does not change significantly, and a relatively high hydrolysis rate is maintained during hydrolysis. (3) The specific surface area (SSA) of partially crystalline cellulose decreases significantly during enzymatic hydrolysis while the change in SSA of regenerated cellulose is found to be negligible. (4) The value of degree of polymerization (DP) of highly ordered crystalline cellulose remains practically constant whereas the change in DP of disordered regenerated cellulose is found to be very significant. (5) Combination of these structural effects as well as cellulase adsorption, product inhibition, and cellulase deactivation all have important influence on the rate of cellulase reaction during cellulose hydrolysis. More experimental evidence for a two‐phase model, which is based on degradation of cellulose by simultaneous actions of cellulase complex on the crystalline and amorphous phases, has been obtained. Based on experimental results from this study and other results accumulated, the mode of cellulase action and a possible reaction mechanism are proposed.
Selective solvent delignification for fermentation enhancement
Authors: Avgerinos G. C. , Wang D. I. C. 
Published: December 2004

AbstractCellulose and hemicellulose in renewable biomass resources such as cornstover and wheat straw have been examined as substrates for the production of ethanol. A mixed culture of selected strains of Clostridium thermocellum and Clostridium thermosaccharolyticum are used to accomplish both the hydrolysis and fermentation of these carbohydrates in a single step. However, lignin and related phenolic materials are shown to diminish the rate, extent, and yield at which these carbohydrates can be utilized for ethanol production. In order to overcome this problem, a selective solvent pretreatment with alkaline–ethanol–water mixtures was examined for the delignification of cellulosic biomass under conditions where very little loss of fermentable carbohyrates results. Under optimal conditions, up to 67% of the initial lignin in cornstover can be extracted while 95% of the α‐cellulose and pentosan carbohydrates remain insoluble. Subsequent mixed culture fermentation of the treated material has shown a 400% increase in the rate of degradation and greater than 85% utilization of the substrate. The effects of various extraction parameters on delignification kinetics and subsequent fermentation performance are discussed.
By‐product inhibition effects on ethanolic fermentation by Saccharomyces cerevisiae
Authors: Maiorella Brian , Blanch Harvey W. , Wilke Charles R. 
Published: December 2004

AbstractInhibition by secondary fermentation products may limit the ultimate productivity of new glucose to ethanol fermentation processes. New processes are under development whereby ethanol is selectively removed from the fermenting broth to eliminate ethanol inhibition effects. These processes can concentrate minor secondary products to the point where they become toxic to the yeast. Vacuum fermentation selectively concentrates nonvolatile products in the fermentation broth. Membrane fermentation systems may concentrate large molecules which are sterically blocked from membrane transport. Extractive fermentation systems, employing nonpolar solvents, may concentrate small organic acids. By‐product production rates and inhibition levels in continuous fermentation with Saccharomyces cerevisiae have been determined for acetaldehyde, glycerol, formic, lactic, and acetic acids, 1‐propanol, 2‐methyl‐1‐butanol, and 2,3‐butanediol to assess the potential effects of these by‐products on new fermentation processes. Mechanisms are proposed for the various inhibition effects observed.
Structural modification of lignocellulosics by pretreatments to enhance enzymatic hydrolysis
Authors: Gharpuray M. M. , Lee Yong‐Hyun , Fan L. T. 
Published: December 2004

AbstractIn this work an evaluation was made of a wide variety of single and multiple pretreatment methods for enhancing the rate of enzymatic hydrolysis of wheat straw. A multiple pretreatment consisted of a physical pretreatment followed by a chemical pretreatment. The structural features of wheat straw, including the specific surface area, crystallinity index, and lignin content, were measured to understand the mechanism of the enhancement in the hydrolysis rate upon pretrement. It has been found that, in general, multiple pretreatments were not promising, since the hydrolysis rates rarely exceeded those achieved by single pretreatments. Ballmilling pretreatment was found to be effective in increasing the specific surface area and decreasing the crystallinity index. Treatment with ethylene glycol was highly effective in increasing the specific surface area, in addition to a high degree of delignification. Peracetic acid pretreatment was highly effective in delignifying substrate. Among multiple pretreatments, those involving peracetic acid treatment generally had lower crystallinity indices and lignin content values. The relationship between the hydrolysis rate and the set of structural features indicated that an increase in surface area and a decrease in the crystallinity and lignin content enhance the hydrolysis; the specific surface area is the most influential of the structural features, followed by the lignin content.
Endogenous metabolism and the stability of microbial prey–predator systems
Authors: Nisbet R. M. , Cunningham A. , Gurney W. S. C. 
Published: December 2004

AbstractWe formulate a variant of the “double Monod model” which takes explicit account of endogenous metabolism. Using parameter values appropriate to carbohydrate‐limited substrate, bacterial prey, and protozoan predator, we study the stability of steady states under chemostat conditions. We conclude that the predator's endogenous metabolism may have a stabilizing effect at low dilution rates.
An enzyme electrode for specific determination of L‐lysine: A real‐time control sensor
Authors: Tran N. D. , Romette J. L. , Thomas D. 
Published: December 2004

AbstractLysine decarboxylase (L‐lysine carboxylyase, E.C.4.1.1.18) is immobolized on a carbon dioxide gas‐sensing electrode, by copolymerization with gelatin using the bifuncitional agent glutaraldehyde. The enzyme electrodes thus prepared are used in a continuous flow system to measure the concentration of L‐lysine in a mixture of amino acids. The measuring time for each sample is about 3 min, including response and rinsing times. The electrode response is linear between 0.01‐1 g/L and has a high specificity for L‐lysine. The enzyme electrode response to lysine at concentrations below 0.5 g/L is stable on repeated use for at least 500 assays.