bluuebunny/crossref_metadata_2025 huggingface dataset:
Saccharification of cellulose by the cellulolytic enzyme system of Thermomonospora sp. II. Hydrolysis of cellulosic substrates
Authors: Ferchak John D. , Hägerdal Bärbel , Pye E. Kendall
Published: December 2004

A saccharification of cellulosic material using culture filtrate from the stationary phase of a culture of Thermomonospora sp. produced primarily cellobiose up to levels inhibitory to further saccharification, while the use of whole broth resulted in the production of glucose as well. Glucose production was enhanced and continued throughout the saccharification (24–36 hr) by several additions of cellobiase activity in the form of culture solids. Using Solka‐Floc as substrate, the “difference sugar” level (total soluble sugar minus glucose) rapidly rose to the same relatively stable concentration under various hydrolysis conditions, which was independent of the total sugar and glucose concentrations. A rapid hydrolusis rate was observed initially during saccharification, followed by a much slower rate of sugar production. Repeated centrifugation of the reaction mixture and replacement of the supernatant with fresh enzyme solution resulted each time in the reinitiation of a rapid hydrolysis rate. Saccharifications using A vicel microcrystalline cellulose, acid‐swollen cellulose, and cotton as substrates were also studied. A modified method of making phosphoric‐acid swollen cellulose is described. Saccharification of this substrate by culture filtrate and sequential additions of culture solids resulted in an inverse relationship between the attained glucose concentration and cellobiose‐cellotriose concentrations.
Enzymatic modification of vegetable protein: Mechanism, kinetics, and production of soluble and partially soluble protein in a batch reactor
Authors: Constantinides A. , Adu‐Amankwa B.
Published: December 2004

Enzymatic hydrolysis of insoluble soybean protein by a protease enzyme produced by Penicillium duponti K 1104, was investigated in a batch reactor. The reaction conditions were 30–55°C and pH 3.4–3.7. The mechanism of solubilization of the insoluble protein by the Penicillium duponti enzyme was deduced from a series of experiments. Kinetic models were developed that involved adsorption followed by peptic digestion of protein, inhibition of low‐molecular‐weight peptides, and enzyme deactivation. The uncoupled kinetic parameters were estimated using the Marquardt nonlinear parameter estimation algorithm. A bang–bang production of soluble and partially soluble protein is suggested for higher productivity. The essential amino acids pattern of the enzyme‐Hydrolyzed soy protein was comparable with the unhydrolyzed protein isolate. Aggregation of the soluble protein for an extended time was observable. The low‐molecular‐weight soluble protein was incorporated into noncarbonated beverages. The amount of protein that could be incorporated into a can of 355 ml noncarbonated beverage, without observable changes in the optical density and also aggregation of the protein, was 2.5 g soluble protein. Beverages with caramel color showed excessive decrease in optical density and precipitation. The kinetics and diffusion in a multipore immobilized‐enzyme recycle reactor will be considered in part II of this series.
Continuous aerobic conversion of poultry waste into single‐cell protein using a single reactor: Kinetic analysis and determination of optimal conditions
Authors: Kargi F. , Shuler M. L. , Vashon R. , Seeley H. W. , Henry A. , Austic R. E.
Published: December 2004

A single‐stage aerobic continuous process for the conversion of poultry waste into single‐cell protein is described. The slurried manure was supplemented by molasses. Kinetics and possible mechanisms for the suggested conversion‐scheme have been investigated. A Box–Wilson experimental design has been employed to elucidate the effect of environmental conditions on reactor performance. Temperature, pH, and percent solids concentration in the feed (media composition) were the independent process variables, while the minimum residence time for the nearly complete utilization of total uric acid and ammonia nitrogen, the amount of carbon required per gram of nitrogen consumed, and protein content of the product were considered as dependent variables. Optimal environmental conditions for the minimum raw material cost and for the maximum percent protein, lysine, and methionine content of the product were determined. The operating conditions of 25°C, pH 7.5, 1.5% solids in the feed, and a residence time of 8.1 hr were found to be the most appropriate conditions maximizing the “profit” function, which is defined as the difference between the product value and raw material cost.
Immobilized mitochondrial electron transport particle for NADH determination
Authors: Aizawa Masuo , Wada Mitsuo , Kato Seishi , Suzuki Shuichi
Published: December 2004

Nonphosphorylating electron transport particles (ETP) prepared from beef heart mitochondrion were immobilized in agar gel. The immobilized ETP showed an oxidase activity to both NADH and succinate. The immobilized ETP was reusable. An electrochemical device for the determination of either NADH or succinate was assembled consisting of the membrane‐bound ETP and an oxygen probe. The response to succinate was specifically inhibited by the addition of malonate.
Partition of hexadecane to the cell surface of Candida tropicalis: Mechanism for the transport of water‐insoluble substrates
Authors: Käppeli O. , Fiechter A.
Published: December 2004

The partition of hexadecane to the cell surface of Candida tropicalis was measured by incubating heat‐inactivated cells with hexadecane‐1‐14C on a gyratory shaker. The free hexadecane was separated by centrifuging the cells through a 15% sucrose solution, and the partitioned hexadecane was quantified by scintillation spectrometry of the samples from the resulting cell sediment. Heat‐inactivated cells did not take up hexadecane as determined by a membrane filtration technique involving organic solvent washing. The partitioning was a time‐dependent process. The velocity increased by increasing the shake rate of te shaker. At 360 rpm and with baffled flasks, saturation of the cell surface with hexadecane was obtained after a 20 min incubation period. The amount of hexadecane partitioned depended on the initial hexadecane‐to‐cell concentration ratio. At a ratio of 5 μmol/mg cell protein the highest amount of hexadecane partitioned was measured at 2100 μmol/mg cell protein. At ratios higher than 6 μmol/mg cell protein the cells were no longer sedimentable by centrifugation. The partition of hexadecane to the cell surface was affected by removing the surface layer of the cell wall by Pronase treatment and by using detergents in the partition assay. Pronase treatment lowered the amount of hexadecane partitioned as a consequence of the removal of the lipophilic layer of the cell surface. Detergents influence the partition coefficient and also lowered the amount of hexadecane partitioning to the cell surface. At a low shaking intensity (280 rpm, unbaffled flasks), after Pronase treatment, and in the presence of detergents he uptake of hexadecane by the cells was limited by the partitioning.
Analysis of microbial growth and product formation with Nitrate as Nitrogen source
Authors: Erickson L. E.
Published: December 2004

Mass balance regularities are used to develop equations for the estimation of maintenance coefficients, true growth yields, and true product yields when nitrate is the nitrogen source. An available electron balance is presented that includes the uptake of nitrate. The application of the theory is illustrated using continuous‐culture data of Stouthamer and Bettenhaussen in which Aerobacter aerogenes is grown aerobically with KNO3 as the nitrogen source.
Influence of very small bubbles on the dynamic kLA measurement in viscous gas–liquid systems
Authors: Heijnen J. J. , Riet K. Van't , Wolthuis A. J.
Published: December 2004

Experiments reveal a fraction of tiny bubbles (≪1 mm) in viscous gas‐liquid systems. It is plausible that the oxygen tension is these bubbles will be in equilibrium with that in the liquid within seconds. This means that, as regards to such oxygen concentration changes as occur on kLA determination by the dynamic method, the “liquid‐small bubble dispersion” can be considered as a homogeneous phase. This leads to major corrections and, therefore, the application of the dynamic kLA method in viscous gas‐liquid systems will be problematic.
Modeling of rotating biological contactor systems
Authors: Wu Yeun C. , Smith Ed D. , Hung Yung T.
Published: December 2004

An investigation of the rotating biological contractor (RBC) process variables to determine the efficiency of biological oxygen demand (BOD) removal is presented. Operating parameters including influent BOD content (<355 mg/liter), flow rate, disk surface area, hydraulic loading, disk rotational speed, liquid retention time, stage number, and wastewater temperature were evaluated. The BOD predictive model was developed using literature data with multiple regression analysis. This study shows that influent BOD concentration, hydraulic loading, stage number, and wastewater temperature are the most significant variables in predicting the RBC system performance. The model presently developed was verified by field data concerned with the treatment of both domestic and low‐strength industrial wastewaters. Also, the results calculated by this model were compared to those obtained from Weng's model.
Human antibody immunosorption of hepatitis B surface antigen from blood and plasma
Authors: Areson Peter D. W. , Charm Stanley E. , Wong Bing L.
Published: December 2004

Removal of the Hepatitis B surface antigen (HBsAg) from whole blood and blood products, using human antibody (HBAb) immunosorbent, was studied and kinetics of complexing were monitored using radioimmunoassay (RIA). An intermittent complexing process was developed that minimizes damage to the cellular components of blood. HBsAg concentration in blood was reduced 1.5 to 2 logarithmic cycles in 3 hr with this system. Free HBsAg remaining in solution at equilibrium was further reduced by transferring the blood to a vessel containing unused immunosorbent. Through multiple stage treatment of a blood sample, it may be possible to reduce the probability of contamination with HBsAg to below the infectious level. This process may be applied to the selective removal of other proteins from blood and plasma.
Utilization of the white‐rot fungus Sporotrichum pulverulentum for water purification and protein production on mixed lignocellulosic wastewaters
Authors: Ek Mats , Eriksson Karl‐Erik
Published: December 2004

A process has been developed that allows a direct conversion of lignocellulosic materials into fungal biomass. The thermotolerant white‐rot fungus Sporotichum pulverulentium has been used in continuous laboratory fermentations as well as in a 25 m3 batch fermentation. Fungal cell mass for feeding trials was produced and the economics of the process were estimated. The investigation shows that the process works satisfactorily on the small continuous scale as well as in the large batch culture. The process also seems easy to scale up. The economic evaluations show the conversion of solid lignocellulosic materials to protein feed is not feasible by our process unless the material to be fermented has a certain negative value. A mixed wastewater, such as the white water system in paper and fiber board mills, containing both water soluble mono‐ and oligosaccharides and solid lignocellulosic material, can, however, be fermented in an economically feasible way due to the combined effect of protein production and water purification. Data on the nutritional value of the product are presented in an accompanying paper.
Inhibition of alcoholic fermentation by substrate and ethanol
Authors: Moulin G. , Boze Hèlène , Galzy P.
Published: December 2004

The effect of ethanol and sugars on rates of fermentation was studied. We used a strain of Canadida pseudotropicalis. The specific rate of fermentation was determined by using the Warburg manometer. The effect of ethanol was formulated as an exponential function of ethanol concentration, but the empirical constant was different when glucose or lactose was used as a substrate. The effects of both ethanol and substrate were formulated. It was demonstrate that when lactose and glucose were present in the medium with a small amount of alcohol, a synergistic effect on the rate of fermentation appeard. This phenomenon considerably limits the rate of fermentation.
Oxidation of D‐glucose in the presence of glucose oxidase and catalase
Authors: Linek V. , Beneš P. , Sinkule J. , Holeček O. , Malý V.
Published: December 2004

The kinetics of oxidation of glucose solution by dissolved oxygen in the presence of glucose oxidase and excess catalase were studied both theoretically and experimentally. The kinetic model used was based on the detailed mechanism of the reaction. The description of the model is given by the Michaelis–Menten equation for the case of two substrates. The experiments were carried out in a closed reactor at a temperature of 25°C and pH 5.55. Commercial enzymes were used. Kinetic constants of the reaction were evaluated by fitting the oxygen concentration profiles calculated from the model to those found experimentally, by the method of nonlinear regression. The rate of D‐glucose mutarotation to α and β form, and distortion of data caused by the dynamics of the applied oxygen probe were taken into account. The determined kinetic constants of the reactions are in good agreement with those given in the literature for purified enzymes. Adoption of literature kinetic data of this reaction to the determination of aeration capacity of fermentors by means of glucose oxidase systems has proved possible.
Concentration of animal blood by ultrafiltration
Authors: Fernando T.
Published: December 2004

Pilot‐scale investigations into the application of ultrafiltration (UF) for concentrating bovine blood or a mixture of bovine and ovine blood are described. Tests were carried out in an Iopor 6CL UF system and a Romicon (hollow fiber) UF system. Optimal operating conditions for these two system were evaluated. Starting from a 18–20% TS lood concentration final concentrations of 28–30% TS were achieved. The lopor system was found to be more suited for processing blood and the average flux values obtained indicated UF to be a more economical process for concentrating blood than vacuum evaporation.
Production of yeast‐lytic enzymes by Cytophaga species in batch culture
Authors: Asenjo J. A. , Dunnill P. , Lilly M. D.
Published: December 2004

The conditions for culture storage, inoculum preparation, and growth of a Cytophaga species, constitutive with respect to yeast‐lytic enzymes, have been established in shake‐flask studies and in 5 liter fermentor experiments. A low cost medium was adopted for 900 liter‐scale fermentation and gave an enzyme activity in the fermentation broth somewhat greater than the comparable laboratory‐scale one.
Enzymatic hydrolysis of cellulose to glucose lung immobilized β‐glucosidase
Authors: Sundstrom D. W. , Klei H. E. , Coughlin R. W. , Biederman G. J. , Brouwer C. A.
Published: December 2004

The production of sugars by enzymatic hydrolysis of cellulose is a multistep process which includes conversion of the intermediate cellobiose to glucose by β‐glucosidase. Aside from its role as an intermediate, cellobiose inhibits the endoglucanase components of typical cellulase enzyme systems. Because these enzyme systems often contain insufficient concentrations of β‐glucosidase to prevent accumulation of inhibitory cellobiose, this research investigated the use of supplemental immobilized β‐glucosidase to increase yield of glucose. Immobilized β‐glucosidase from Aspergillus phoenicis was produced by sorption at controlled‐pore alumina with about 90% activity retention. The product lost only about 10% of the original activity during an on‐stream reaction period of 500 hr with cellobiose as substrate; maximum activity occurred near pH 3.5 and the apparent activation energy was about 11 kcal/mol. The immobilized β‐glucosidase was used together with Trichoderma reesei cellulase to hydrolyze cellulosic materials, such as Solka Floc, corn stove and exploded wood. Increased yields of glucose and greater conversions of cellobiose of glucose were observed when the reaction systems contained supplemental immobilized β‐glucosidase.
Biosorption of uranium and thorium
Authors: Tsezos Marios , Volesky Bohumil
Published: December 2004

Selected samples of waste microbial biomass originating from various industrial fermentation processes and biological treatment plants have been screened for biosorbent properties in conjunction with uranium and thorium in aqueous solutions. Biosorption isotherms have been used for the evaluation of biosorptive uptake capacity of the biomass which was also compared to an activated carbon and the ion exchange resin currently used in uranium production processes. Determined uranium and thorium biosorption isotherms were independent of the initial U or Th solution concentration. Solution pH affected the exhibited uptake. In general, lower biosorptive uptake was exhibited at pH 2 than at pH 4. No discernible difference in uptake was observed between pH 4 and pH 5 where the optimum pH for biosorption lies. The biomass of Rhizopus arrhizus at pH 4 exhibited the highest uranium and thorium biosorptive uptake capacity (g) in excess of 180 mg/g. At an equilibrium uranium concentration of 30 mg/liter, R. arrhizus removed approximately 2.5 and 3.3 times more uranium than the ion exchange resin and activated carbon, respectively. Under the same conditions, R. arrhizus removed 20 times more thorium than the ion exchange resin and 2.3 times more than the activated carbon. R. arrhizus also exhibited higher uptake and a generally more favorable isotherm for both uranium and thorium than all other biomass types examined.
Preliminary studies on the use of internal carbon sources in the removal of nitrogen from sewage with a model treatment system using alternating aerobic and anaerobic conditions
Authors: Battley E. H.
Published: December 2004

A description is presented of the design and performance of a model sewage treatment system consisting of one aerobic reactor and clarifier plus one anaerobic reactor, with an aerobic‐mixed‐liquor‐volume/anaerobic‐mixed‐liquor‐volume ratio of 1:4. Effluent values of ammonia, nitrite, and nitrate nitrogen were found to be 0, 0, and about 5 ppm, respectively. Effluent organic nitrogen was not determined, having been assumed to be negligible. Approximately 90% of the total influent nitrogen was removed by nitrification plus denitrification. Sludge production was found to be minimal, and it was never necessary to waste sludge from the system.
Casein hydrolysis in stirred tank reactors using chymotrypsin immobilized on magnetic supports
Authors: Munro P. A. , Dunnil P. , Lilly M. D.
Published: December 2004

Nickel‐NiO‐BSA‐chymotrypsin has been used to hydrolyze casein in both batch and continuous stirred tank reactors. The kinetics of hydrolysis in both types of reactor were considered. Some operational problems encountered using fine powder catalysts in batch stirred tank reactors are discussed. High gradient magnetic separation was found to be a powerful catalysts retention method for magnetic support particles, particularly when using a ferromagnetic collection matrix. Nickel particles of diameter 3–7 μm were easily separated from water at a processing velocity of 39 mm/sec. Nickel powder and precipitated Fe3O4 were also separated satisfactorily using a rotating drum magnetic separator.
The use of calcium alginate gels for “solids separation” and “diffusional chromatography” of biological materials
Authors: Kierstan M.
Published: December 2004

The use of calcium alginate gels for the “Solids Separation” techniques was demonstrated by entrapment of a yeast extract in calcium alginate pellets and the study of the release of alcohol dehydrogenase and NADH into a dilute calcium chloride solution. The use of calcium alginate gels for a “Diffusional Chromatography” technique was demonstrated in a model system by a fractionation of NAD and hemoglobin release following their entrapment in calcium alginate pellets. The advantages of these techniques and their potentials are discussed.
Evaluation of feeding strategies in carbon‐regulated secondary metabolite production through mathematical modeling
Authors: Bajpai R. K. , Reuß M.
Published: December 2004

There is now growing evidence that the production of many secondary metabolic by microorganisms is subjected to carbon‐catabolite regulation. Even though the exact mode of this regulation is not yet clear, an engineering analysis of the production process is still possible based upon a suitable hypothesis. By way of simulation of penicillin fermentation data obtained from the literature, a mechanistic model involving a substrate inhibition kinetics of product formation has been verified in this paper. Such a model has been found successful not only in predicting simple sugar‐feeding strategy, but also a complicated computer guided strategy based upon controlling biomass growth rates in the tropo and idiophases. Using this model, for strategies for sugar feeding into penicillin fermentation have been investigated. These results show that similar penicillin productivities can be obtained using any of these strategies provided fermentations are carried out under optimal conditions corresponding to the strategy chosen. Effect of maximum oxygen transfer capacity of the fermentor under the conditions of fungal growth has been incorporated using an upper limit of biomass concentration on achievement of which the fermentations must be stopped due to serious oxygen limitations. Results of model simulations with such limits throw light upon the way in which different fermentors may behave with respect to product formation.
Microelectrode studies of oxygen transfer in trickling filter slimes*
Authors: Chen Y. S. , Bungay H. R.
Published: December 2004

Slime‐covered rocks and samples of process waters from two trickling filters for treatment of municipal wastes were brought to the laboratory for probing with microelectrodes to determine dissolved oxygen (DO). Slime thickness was 0.4–1.5 mm. Flow rate of medium over the slime had a minor effect on slime respiration, but pH 5 or below was strongly inhibitory. Increasing temperature showed lower oxygen concentration throughout a slime, although 27°C had results little different from those at 22°C. Medium concentration had a profound effect on oxygen concentration profiles, and either oxygen‐limited or substrate limited respiration could be demonstrated. Illumination of slimes from the top of the trickling filter developed oxygen supersaturation because oxygen from photosynthesis could not diffuse away rapidly.
Determination of the inherent deactivation characteristics for the parallel poisoning of immobilized catalase
Authors: Tai Nguyen M. , Greenfield P. F.
Published: December 2004

An approximate analytical solution which describes the deactivation of catalase immobilized on porous supports is provided. Catalase was chosen as an example of an enzyme which undergoes parallel poisoning. The solution incorporates the effects of pore diffusion and of the parallel poisoning. The solution incorporates the effects of pore diffusion and of the parallel poisoning of catalase by its substrate hydrogen peroxide into a time dependent effectiveness factor which can then be inserted into the appropriate reactor equations. The model was tested by measuring experimentally the deactivation of immobilized catalase in both a packed bed reactor and a continuous stirred basket reactor and was found to be very satisfactory at inlet substrate concentrations of less than 0.02M. Values of the deactivation rate constant obtained by regression analysis were independent of particle type and size and reactor description indicating that they were in fact inherent characteristics of the immobilized enzymes which are immobilized on supports and which undergo substrate or parallel poisoning.
Immobilization of the methanogenic bacterium Methanosarcina barkeri
Authors: Scherer P. , Kluge M. , Klein J. , Sahm H.
Published: December 2004

Whole cells of the methanogen Methanosarcina barkeri were immobilized in an alginate network which was crosslinked with Ca2+ ions. The rates of methanol conversion to methane of entrapped cells were found to be in the same range as the corresponding rates of free cells. Furthermore, immobilized cells were active for a longer period than free cells. The particle size of the spherical alginate beads (1.2 mm‐3.7 mm ϕ) and thus diffusion had no obvious influence on the turnover of methanol. The half‐value period for methanol conversion activity determined in a buffer medium was approximately 4 days at 37°C for entrapped cells. The apparent Km value K for such cells was nearly 140mM and the Vmax value was about 1.2 μmol methanol/min/mg entrapped protein. Therefore the high rates of methanol degradation measured, e.g., 0.5 μmol methanol/min/mg entrapped protein, indicated that the immobilization technique preserved the cellular functions of this methanogenic bacterium.
Lactate and ethanol as intermediates in two‐phase anaerobic digestion
Authors: Pipyn P. , Verstraete W.
Published: December 2004

The thermodynamics of the various anaerobic digestion patterns of hexose to methane are compared. It appears that by directing the hexose‐hydrolysis phase towards ethanol and lactic acid production, methanogenesis can be enhanced because the syntrophic bacteria are allocated more potentially available energy. This hypothesis was confirmed in a series of laboratory test runs. They revealed that lactic acid and ethanol as intermediates, in comparison to lower volatile fatty acids, give rise to a considerably higher effluent quality and a slightly larger biogas production.
A two‐phase oxygen uptake model of aerobic fermentations
Authors: Sobotka M. , Votruba J. , Prokop A.
Published: December 2004

The mechanism of Solid particle flotation was used for explaining an alternative route of oxygen uptake by cells situated within the relatively stagnant liquid region adjacent to bubbles in a submerged culture. The Two‐phase model of oxygen uptake takes into consideration uptake from both liquid and gaseous phases, the latter being denoted as the direct uptake. Experiments obtained with yeast cultures on different substrates were used to evaluate the proportion of both types of uptake. The combined model provides a better fit to experimental data compared to the one‐phase model which omits the direct uptake. The results are discussed from the viewpoint of the enhancement of oxygen absorption by cells present near the interface.
Technological problems in cultivation of plant cells at high density
Authors: Tanaka Hideo
Published: December 2004

Using Cudrania tricuspidata cells as model plant cells which have high sensitivity to hydrodynamic stress, technology problems in the cultivation of the plant cells at high density were investigated. Using “shake” flasks on a reciprocal shaker and Erlenmeyer flasks on a rotary shaker and with a high supply of oxygen on order to obtain high cell densities in shaken cultures, particles breakdown and damage to the largest cell aggregate group (above 1981 μm in diameter) occurred and normal cell growth became impeded. The mass‐transfer coefficient (K)for a model solid–liquid system (β‐naphthol particles and water) in place of a system of plant cells and a liquid medium was proposed as an intensity index of hydrodynamic stress effects on plant cells in subsequent cultures under various conditions in the bioreactor systems. Normal cell growth was obtained under culture conditions for K values less than about 4.4 × 10−3 cm/sec. The characteristics of various bioreactors used until now were investigated by considering the three main technological factors (capacity of oxygen supply, intensity of hydrodynamic stress effects on plant cells, and intensity of culture broth mixing and air‐bubble desperation). The most suitable bioreactor for culturing plant cells at high density was ajar fermentor with a modified paddle‐type impeller (J‐M). The yield of cell mass in the 10‐liter J‐M (working volume 5 liter) was about 30 g dry weight per liter of medium.
Process development and evaluation for algal glycerol production
Authors: Chen Bill J. , Chi C. H.
Published: December 2004

This article and develops a process for large‐scale production of glycerol by means of a hemophilic algae. The process is shown to be economically and technically feasible. Although the proposed process is extremely capital intensive, the total production cost is competitive with existing glycerol process. In addition, the overall energy requirement is much lower than that of the petrochemical process. This proposed process provides an alternative route for glycerol production that is minimally dependent on fossil fuels and is therefore, less sensitive to crude oil availability and price. The primary raw material carbon dioxide from stack gas, is an inexpensive and renewable resource. Maximal Utilization of solar energy is made not only in the glycerol synthesis steps but also in the product recovery system. Significant improvement in the process economics can be realized through further development of large‐scale cultivation technology, and biomass distribution and collection machinery. Due to the labor intensive nature of the proposed algal process, it is particularly suitable for less developed nations with limited fossil fuel resources and lower labor costs.
Growth of cellulolytic bacteria on sugarcane bagasse
Authors: Enríquez A.
Published: December 2004

The growth behavior of Cellulomonas has been examined in fermentation system using alkali pretreated sugarcane bagasse. During the batch operation diauxic growth was found which would not seem to be explained by catabolic repression. The relative variation of cellulose and hemicellulose during the fermentation process suggests the initial utilization of easily degradable substrate, i.e., hemicellulose and amorphous cellulose, until their concentration becomes limiting, followed by utilization of the crystalline cellulose. The conversion of substrate was 70% with a yield of 0.355 g of biomass per gram of bagasse feed.
Kinetics of the isomerization of D‐glucose into D‐fructose catalyzed by glucose isomerase containing Arthrobacter cells in immobilized and nonimmobilized form
Authors: Van Keulen M. A. , Vellenga K. , Joosten G. E. H.
Published: December 2004

The kinetic properties of immobilized and nonimmobilized glucose isomerase have been investigated. In both cases the kinetics can be described by a modified Michaelis–Menten expression. It appeared that immobilization causes no deactivation. Furthermore, it was shown that the permeability of the cell membrane increases by heat and toluene treatments.
Automatic control for fed‐batch culture of single cell protein
Authors: Huang Shih Yow , Chu Wey‐Bang
Published: December 2004

Candida utilis was cultivated in a 5‐liter jar fermentor using ethanol as sole carbon source. Control of ethanol in the cultivation broth was performed by using an ethanol vapor monitoring instrument and an oxygen electrode coupled with two control circuits. By setting upper and lower bounds according to the predetermined conditions, a signal from a gas monitoring sensor switched the lower or higher bound relay governing the actuating or switch‐off of the motor; this maintained a proper concentration of ethanol in the cultivation of ethanol in the system. The growth of cells was found to be satisfactory. Cell concentration reached 64 g/liter during a 20‐hr cultivation. As the results of comparative experiments, the control mode using the gas monitoring instrument was found to be superior to that using dissolved oxygen as a controlling signal, especially at high cell concentration.
Application of immobilized aminoacylase from Micrococcus agilis for isolation of D‐phenylglycine from its racemic mixture
Authors: Szwajcer E. , Szewczuk A. , Mordarski M.
Published: December 2004

The procedure for isolation of D‐phenylglycine from its racemic mixture by enzymatic hydrolysis of L‐enantiomer of N‐acetyl‐D,L‐phenylglycine is described. For this hydrolysis. aminoacylase from Micrococcus agilis immobilized by sorption of DEAE‐cellulose was applied. As is also shown, the course of enzymatic reaction can be directly controlled by spectrophotometric method.
Simulation of the integration of the internal energy metabolism and cell cycle of Saccharomyces cerevisiae
Authors: Hall R. J. , Barford J. P.
Published: December 2004

A computer simulation of the integration of the internal energy metabolism and the cell cycle of Saccharomyces cerevisiae is described. This was attempted, for the first time, as a result of the observation that in this organism the overall or average external metabolic exchange rates often differed considerably from the internal metabolic fluxes which they are normally assumed to represent. This was the result of such factors as the variation in the nature of the metabolism of the organism depending on its stage in the cell cycle and redox interactions between anabolism and catabolism. The overall result of this simulation is the prediction of the internal metabolic fluxes consistent with the experimentally determined external fluxes. While these simulation depend on the assumption regarding the energetics and cell cycle of Saccharomyces cerevisiae, they provide a means of examining with precision such processes as the energetics of cell growth and cell cycle variation. As a result, within these limitation, they allow the systematic study of coordinated cell control. Such an approach provides a useful and largely unused adjunct to the experimental approaches which have attempted the study of coordinated metabolic regulation.
Design of a nonuniformly distributed biocatalyst
Authors: Park Sun Ho , Lee Sun Bok , Ryu Dewey D. Y.
Published: December 2004

The properties of a nonuniformly distributed biocatalyst, where the active enzymes are immobilized on the exterior or the interior portions o a solid support, are compared with those of a conventional biocatalyst which is uniformly distributed in a spherical geometry. To investigate the performance of nonuniformly distributed biocatalysts their effectiveness factors are computed and compared for six different enzyme distribution configurations: one‐half core, one‐half shell, one‐third center space, one‐third middle annulus, one‐third outer shell, and the uniformly distributed. According to the results of numerical analysis, the biocatalyst performance of the exterior "shell" configuration is always far more effective for the immobilized enzymes with positive order reaction kinetics such as Michaelis‐Menten and competitive product inhibition. However, in the case of negative order enzymatic reaction kinetics such as substrate inhibition, the interior "core" configuration of the biocatalyst can render far greater enzyme utilization efficiency.
Mechanical control of the activity of glucose oxidase immobilized on porous polyvinylchloride membrane
Authors: Ishimori Yoshio , Karube Isao , Suzuki Shuichi
Published: December 2004

Glucose Oxidase was immobilized on a porous polyvinylchloride (PVC) membrane. The activity of the glucose oxidase‐PVC membrane decreased when the membrane was mechanically stretch. A linear relationship was observed between the stress and the relative logarithmic activity of the glucose oxidase‐PVC membrane. Apparent Michaelis constant (Km′) and maximum velocity (Vm′) of the glucose oxidase‐PVC membrane under stretched conditions were 1.4 and 0.71 times those without stretching, respectively. The decrease of the membrane activity with stress was reproducible. Therefore, the glucose oxidase activity of the membrane can be controlled with stress.
Design and performance of a new microcalorimetric system for aerobic cultivation of microorganisms
Authors: Ishikawa Yasufumi , Shoda Makoto , Maruyama Hiromu
Published: December 2004

A twin‐type heat‐conduction calorimeter for an aerobic fermentation process was designed and constructed fermentor both in batch and continuous runs. The time constant of the calorimeter was 3.3 min. The volumetric oxygen transfer coefficient (kLa) of the vessel was measured by a sulfite oxidation method in a continuous flow system under various rotation speeds and gas flow rates. Sufficient thermal stability of the calorimeter was obtained both in batch and continuous runs within the operation time period.
Mutagenesis and carcinogenesis testing in vitro
Authors: Casto Bruce C.
Published: December 2004

The development and validation of short‐term tests for carcinogens and mutagens are urgently needed if estimates of 70–80% for environmentally induced cancer are valid. Several methods for in vitro testing have been described in microbial and mammalian cells. It is anticipated that a battery of tests will soon be available with high degree of reproducibility and predictability for potential in vivo carcinogenesis. This review discusses those assays currently being implemented in mammalian cells including a brief description of the methodology, advantages, and disadvantages, and the correlation with known in vivo activity.
Microcarrier culture: Applications in biological production and cell biology
Authors: Crespi Charles L. , Imamura Toshiko , Leong Phaik‐Mooi , Fleischaker Robert J. , Brunengraber Henri , Thilly William G. , Giard Donald J.
Published: December 2004

This report reviews recent progress in micro carrier technology at the Massachusetts Institute of Technology. This progress includes new understanding of the nutritional needs of high‐cell density micro carrier cultures, the demonstration of cell growth on microcarriers in a hormone‐supplemented, serum‐free medium, and the continuous cell propagation of epithelial cell types in microcarrier culture by medium modification that permits efficient bead‐to bead transfer. Also, a technique for obtaining large quantities of mitotic cells by selective detachment from microcarriers is reported. Finally, recent progress in interferon production from human foreskin fibroblasts grown on microcarriers is outlined: Our improvements in the interferon “super induction” process have increased the interferon yield per cell fivefold to tenfold.
Phenotypic variation in plants regenerated from protoplasts: The potato system
Authors: Bidney Dennis L. , Shepard James F.
Published: December 2004

Regeneration of whole plants from isolated protoplasts (plant cells devoid of cell walls) provides a novel capability that is potentially useful for crop improvement efforts. Such a regeneration capacity has been developed for the commercial potato cultivar ‘russet Burbank,’ currently the most popular cultivar in production. Due to fertility problems of this cultivar, the improvement of ‘russet Burbank’ by classical breeding procedures has been limited. Examination of a large population of protoplast‐derived clones has revealed the variation for a number of traits can be observed. Variation observed under laboratory conditions and in field trials includes changes in plant morphology and tuber‐setting characteristics, as well as alterations in response to environmental and pathogen stress. A brief description of the cloning process and the potential for application of cloning technology in crop plant improvement will be presented.
Prediction of the degradability of sugarcane celulosic residues by indirect methods
Authors: Cabello Agustín , Conde José , Otero Miguel A.
Published: December 2004

The effect of mild NaOH treatments on sugarcane cellulosic wastes (bagasse, pith, and straw) to increase their biological degradability has been studied. At a level of 8% NaOH (on a dry matter basic) 60% digestibility measured by the in vitro technique was achieved for all materials tested. Indirect methods to predict the digestibility of treated materials such as the bacterial degradability, enzymatic degradability, hot‐water solubility, and chemical oxygen demand were tried as alternative methods to the rumen fluid technique. High correlation coefficients for all materials were obtained with all alternative techniques. The minimal r value was 0.96 while the highest was 0.99. An important reduction of time and reagents is achieved by the utilization of the solubility and chemical oxygen demand tests.
Immobilization of microbial cells in crosslinked, prepolymerized, linear polyacrylamide gels: Antibiotic production by immobilized Streptomyces clavuligerus cells
Authors: Freeman A. , Aharonowitz Y.
Published: December 2004

A mild new method for the immobilization whole microbial cells has been developed. Cells were suspended in a solution of preformed, linear, water‐soluble Polyacrylamide chains, partially substituted with acylhydrazide groups. The Prepolymerized backbone polymer was crosslinked, in the presence of viable cells, by stoichiometric amounts of dialdehydes such as glyoxal, glutardialdehyde, and period ate‐oxidized polyvinyl alcohol. The crosslinking reaction, carried out in cold, neutral physiological conditions resulted in cells entrapped in gels with physical properties similar to those of the common Polyacrylamide gels. However, cell damage generally caused by the acrylamide monomer was avoided. Resting Streptomyces clavuligerus cells, possessing a high capacity for antibiotic production, were entrapped according to this procedure. These immobilized cells produced cephalosporins continuously for 96 h with yields similar to those of free resting cells. The same cells, when immobilized by direct polymerization acrylamide monomers, yielded significantly lower amount of antibiotics.
Optimal substrate profile for antibiotic fermentations
Authors: Guthke R. , Knorre W. A.
Published: December 2004

The optimal substrate profile is calculated by Pontryagin's maximum principle for a simplified mathematical model of microbial growth and product formation. This model is fitted to experimental data of turimycin fermentation. Sub optimal control is studied for comparison.
A model for noninhibitory microbial growth
Authors: Chiam H. F. , Harris I. J.
Published: December 2004

A model for noninhibitory microbial growth has been developed which is superior to the Monod model in that it can predict the decline in steady‐state growth yields at both the slow and the fast specific growth rates. The model parameters are evaluated from data obtained for steady‐state, phenol‐limited Pseudomonas putida growth using a conventional 1‐dm3 cheniostat. The model also has been successfully applied to Mor and Fiechter's data for cheniostat yeast cultures.
Unstructured model for growth of mycelial pellets in submerged cultures
Authors: Van Suijdam J. C. , Hols H. , Kossen N. W. F.
Published: December 2004

An unstructured model is presented to describe growth of mycelial pellets in submerged cultures. This model integrates growth kinetics at the scale of the hyphae with the physical mechanisms of mass‐transfer processes at the scale of the pellets and the fermentor. The main elements of the model are biomass, substrate, and oxygen balances for the liquid phase and the pellets. The possible occurrence of oxygen limitation in the pellets is introduced in analogy with catalyst theories by means of an effectiveness factor. To simulate the growth of pellets the model is transferred into a computer program. The model is tested by means of fermentation experiments in a bubble column. Results of the growth experiments compare favorably with the outcome of computer simulations.
Enhancement of enzymatic hydrolysis by simultaneous attrition of cellulosic substrates
Authors: Neilson Martin J. , Kelsey Rick G. , Shafizadeh Fred
Published: December 2004

It has been shown that simultaneous attrition of cellulose in an attritor containing stainlesssteel beads results in a substantial enhancement of the enzymatic hydrolysis. The attrition exerts two opposing effects, continuous delamination and comminution of the substrate with formation of new reactive sites and a gradual denaturation and inactivation of the enzyme. Consequently, the hydrolysis proceeds very rapidly at first and levels off at about 70% saccharification of the substrate. Accumulation of hydrolysis products is also responsible for inhibition of the enzyme. The attrition method is effective for the saccharification of cottonwood in which the cellulosic microfibrils are embedded in a matrix of lignin and hemicelluloses. A comparison between the saccharification of wood, lignocellulose, holocellulose, and cellulose with simultaneous attrition showed that the lignin component provided more hindrance toward the saccharification process than hemicelluloses, which are themselves subject to enzymatic hydrolysis.
Kinetics of immobilized sucrose phosphorylase
Authors: Taylor Frank , Chen Lifu , Gong Cheng Shung , Tsao G. T.
Published: December 2004

Sucrose phosphorylase was immobilized on porous ceramic beads with 3‐aminopropyltriethoxysilane and glutaraldehyde. It was determined experimentally that under laboratory conditions there was no diffusional resistance to the enzyme‐catalyzed reaction. The half‐life of the immobilized enzyme varied from about 35 days at 30°C to about 5 days at 40°C. The pH optimum was found to be between 6.5 and 7.0. The activation energy for the reaction was found to be about 12.5 kcal/mol. Eleven independent kinetic constants in the complete rate equation for the previously proposed ping–pong mechanism were found to be in good agreement with those for the soluble enzyme.
Studies on immobilized Saccharomyces cerevisiae. I. Analysis of continuous rapid ethanol fermentation in immobilized cell reactor
Authors: Tyagi R. D. , Ghose T. K.
Published: December 2004

Rapid fermentation of cane molasses into ethanol has been studied in batch, continuous (free‐cell and cell‐immobilized systems) by a strain of Saccharomyces cerevisiae at temperature 30°C and pH 5.0. The maximum productivity of ethanol obtained in immobilized system was 28.6 g L−1 h−1. The cells were immobilized by natural mode on a carrier of natural origin and retention of 0.132 g cells/g carrier was achieved. The immobilized‐cell column was operated continuously at steady state over a period of 35 days. Based on the parameter data monitored from the system, mathematical analysis has been made and rate equations proposed, and the values of specific productivity of ethanol and specific growth rate for immobilized cells computed. It has been established that immobilized cells exhibit higher specific rate of ethanol formation compared to free cells but the specific growth rate appears to be comparatively low. The yield of ethanol in the immobilized‐cell system is also higher than in the free‐cell system.
Potentiometric quantitation of glycerol using immobilized glycerol dehydrogenase
Authors: Chen A. K. , Starzmann J. A. , Liu C. C.
Published: December 2004

Glycerol dehydrogenase was immobilized in polyacrylamide gel layered over a small platinum screen and used to catalyze the oxidation of glycerol. In the presence of NAD+ and potassium ferricyanide, the coupling reaction generated a measurable electrical potential which was found to be Nernstian with respect to the glycerol concentration range of 10−4M to 10−1M. The reproducibility of the measurement and the optimal conditions for glycerol determination were described.