bluuebunny/crossref_metadata_2025 huggingface dataset:
Oxygen transfer in mechanically agitated aqueous systems containing dispersed hydrocarbon
Authors: Hassan Ibrahim T. M. , Robinson Campbell W.
Published: December 2004

The effect of dispersed n ‐dodecane or n ‐hexadecane on the air‐to‐aqueous phase overall volumetric oxygen transfer coefficient in a simulated (cell‐free) stirred‐tank fermentor is described. The oil volume fraction ranged from zero to 0.10; the ionic strength of the aqueous phases was varied from 0 to 0.45. The air‐to‐aqueous phase coefficients in both oil‐free (KLa) and oil‐bearing (KLa*) systems were evaluated from unsteady‐state experiments using a membrane‐covered probe to follow the aqueous phase dissolved oxygen tension.

For all systems studied, KLa*/KLa was found to be independent of P/V and vs for all practical purposes. However, for a particular aqueous phase and at a given P/V and vs, the ratio KLa*KLa generally differed from unity. Depending on the combination of hydrocarbon type and volume fraction and the aqueous‐phase ionic strength employed, the dispersed hydrocarbon may, in some cases, reduce the rate of oxygen transfer and in others enhance it relative to that of the corresponding oil‐free gas–liquid dispersion. Enhancement of the air‐to‐aqueous transfer rate by such negative spreading coefficient hydrocarbons has not been reported previously.
Assimilation of liquid hydrocarbon by microorganisms. I. Mechanism of hydrocarbon uptake
Authors: Miura Yoshiharu , Okazaki Mitsuo , Hamada Shin‐Ichiro , Murakawa Shin‐Ichi , Yugen Rieko
Published: December 2004

The uptake mechanism of liquid hydrocarbons of low solubility in water was investigated, using microorganisms with different affinities for liquid hydrocarbon. Microorganisms which could utilize hydrocarbon were much more adherent to hydrocarbon than those which could not. The adhesive force between Candida intermedia IFO 0761 and hydrocarbon was higher than that of Candida tropicalis ATCC 20336, though both could utilize hydrocarbon. The total hydrocarbon uptake from the drop and accommodation forms of hydrocarbons was much higher than that from dissolved hydrocarbon. The uptake rate of drop‐form hydrocarbon was nearly equal to that of accommodation‐form hydrocarbon for C. intermedia, but was lower for C. tropicalis which shows lower adhesion to hydrocarbon.
Ferrous iron oxidation and uranium extraction by Thiobacillus ferrooxidans
Authors: Guay Roger , Silver Marvin , Torma Arpad E.
Published: December 2004

The microbiological oxidation of ferrous iron in batch and continuous systems has been investigated in relation to uranium extraction from a low‐grade ore by Thiobacillus ferrooxidans. The influence of the parameters, agitation, and aeration on oxygen saturation concentration, rate of oxygen mass transfer, and rate of ferrous iron oxidation was demonstrated. The kinetic values, Vmax and K were determined using an adapted Monod equation for different dilution rates and initial concentrations of ferrous iron. The power requirements for initial leaching conditions were also calculated. Uranium extraction as high as 68% has been realized during nine days of treatment. Regrinding the leach residue and its subsequent leaching yielded 87% uranium solubilization.
Continuous manufacture of yogurt. II. Procedure and apparatus for continuous coagulation
Authors: Driessen F. M. , Ubbels J. , Stadhouders J.
Published: December 2004

The procedure and apparatus for the continuous coagulation of yogurt are described. The continuous coagulation takes place in a plug‐flow fermentor. Prefermented milk is brought into this fermentor with the help of a centrifugal distributor, which avoids any undesirable mixing of the prefermented milk with the acidifying milk. A special stirring plate allows a stirring treatment in the coagulation tank. By this procedure the acidity and the viscosity of the final yogurt can be controlled between certain limits. The organoleptic characteristics of the continuous manufactured yogurt are good.
Amperometric assay of coenzyme‐dependent oxidoreductase enzymes in a flow‐through cell
Authors: Wallace Thomas C. , Leh Melonia Berezny , Coughlin Robert W.
Published: December 2004

We have demonstrated that a simple electrochemical cell can serve as a detector of NADH concentration in a flow system thereby providing an assay technique for NADH dependent enzymes. When this is applied to NADH produced by enzymatic reaction, then a reproducible measure of enzyme activity is obtained. This method of enzyme activity assay is applicable to a number of oxidoreductase enzymes which employ NAD+ or NADP+ as coenzymes to achieve substrate modification. The presence of electroactive species in samples of human serum has proved a serious problem in the electrochemical analysis of serum activity. These species produce a large background anode current at the anode voltage appropriate for NADH oxidation. The presence of this high current limits the usefulness of amplification of the current output to detect small changes in NADH concentration.
Cellobiase from Trichoderma viride: Purification, properties, kinetics, and mechanism
Authors: Gong Cheng‐Shung , Ladisch Michael R. , Tsao George T.
Published: December 2004

Three distinct cellobiase components were isolated from a commercial Trichoderma viride cellulase preparation by repeated chromatography on DEAE cellulose eluting by a salt gradient. The purified cellobiase preparations were evaluated for physical properties, kinetics, and mechanism. Results from this work include: (1) development of a one step enzyme purification procedure using DEAE‐cellulose; (2) isolation of three chromatographically distinct, yet kinetically similar, cellobiase fractions of molecular weight of ∼76,000; (3) determination of kinetics which shows that cellobiase hydrolyzes cellobiose by a noncompetitive mechanism and that the product, glucose, inhibits the enzyme, and (4) development of an equation, based on the mechanism of cellobiase action, which accurately predicts the time course of cellobiose hydrolysis over an eightfold range of substrate concentration and conversions of up to 90%. Based on the data presented in the paper, it is shown that product inhibition of cellobiase significantly retards the rate of cellobiose hydrolysis.
Corynecin (chloramphenicol analogs) fermentation studies: Selective production of Corynecin I by Corynebacterium hydrocarboclastus grown on acetate
Authors: Nakano Hirofumi , Tomita Fusao , Yamaguchi Ken , Nagashima Minoru , Suzuki Takeo
Published: December 2004

Corynebacterium hydrocarboclastus KY 8835 grew in the acetate medium and accumulated 28mM Corynecins which was the highest production yield among the processes using various carbon sources. Selective production of Corynecin I (over 90% of all Corynecins), which had been desired for increase of the product yield, was achieved in this acetate medium. To keep the concentration of acetate, ammonium, and phosphate ions in the optimum range throughout the fermentation, a solution containing CH3COOH (50%), CH3COONH4 (9%), and KH2PO4(0.2%) was fed continuously to the culture medium as the pH controlling agent. The addition of KCl (1%) and NaCl (1%) to the medium at 12 hr after inoculation stimulated the production of Corynecins.
Alcohol production by selected yeast strains in lactase‐hydrolyzed acid whey
Authors: O'Leary V. S. , Green R. , Sullivan B. C. , Holsinger V. H.
Published: December 2004

Ethanol production by Kluyveromyces fragilis and Saccharomyces cerevisiae was studied using cottage cheese whey in which 80 to 90% of the lactose present had been prehydrolyzed to glucose and galactose. Complete fermentation of the sugar by K. fragilis required 120 hr at 30°C in lactase‐hydrolyzed whey compared to 72 hr in nonhydrolyzed whey. This effect was due to a diauxic fermentation pattern in lactase‐hydrolyzed whey with glucose being fermented before galactose. Ethanol yields of about 2% were obtained in both types of whey when K. fragilis was the organism used for fermentation. Saccharomyces cerevisiae produced alcohol from glucose more rapidly than K. fragilis, but galactose was fermented only when S. cerevisiae was pregrown on galactose. Slightly lower alcohol yields were obtained with S. cerevisiae, owing to the presence of some lactose in the whey which was not fermented by this organism. Although prehydrolysis of lactose in whey and whey fractions is advantageous in that microbial species unable to ferment lactose may be utilized, diauxie and galactose utilization problems must be considered.
Characteristics of unbuffered gel‐immobilized urease particles. I. Internal pH
Authors: Atkinson B. , Rott J. , Rousseau I.
Published: December 2004

The overall rate of reaction of a gel‐immobilized urease particle necessarily depends upon the hydrogen ion concentrations within the particle. When the particle is unbuffered, the internal hydrogen ion concentrations are a consequence of the local rates of reaction and the rate of egress of the products of hydrolysis. A simple apparatus has been devised which allows a fairly rapid determination of the hydrogen ion concentration in the center of a particle for any given size, enzyme concentration, substrate concentration, and external pH. The products of urea hydrolysis are self‐buffering in the region of pH 8.83 and for an external pH less than the self‐buffering pH, the pH within the particle is increased because of the reaction. When the external pH is greater than the self‐buffering pH, the converse occurs. The pH at the center of the particle approaches the self‐buffering pH with an increase in particle size and enzyme concentration. The external pH necessarily differs in effect when above or below the self‐buffering pH. An increase in the external substrate concentration has a limited effect, simply rendering the local rates of reaction to be of zero order. The center‐line pH and therefore all internal hydrogen ion concentrations depend upon the parameter \documentclass{article}\pagestyle{empty}\begin{document}$ L\sqrt {\rho _e} $\end{document} and the external pH. Differences between the external and center‐line pH values of the order of units are unexceptional. The implications of the internal pH profiles on the local and overall rates of reaction are explored.
Process engineering studies on immobilized trypsin using molecular sieves as carriers
Authors: Mukherjea R. N. , Bhattacharya P. , Ghosh B. K. , Taraphdar D. K.
Published: December 2004

In the present investigation molecular sieve has been found to be a suitable carrier for the immobilization of enzymes. From the present study it may be specifically found that trypsin and pappain can be immobilized by molecular sieve type 4A following a very simple technique. The immobilized enzyme can be used both in packed as well as in a continuous stirred tank reactor (CSTR).
Hydrocarbon uptake in hydrocarbon fermentations
Authors: Gutierrez J. R. , Erickson L. E.
Published: December 2004

Candida lipolytica (strain ATCC 8662) was grown on a simple defined medium with n‐hexadecane as the main carbon Source under batch fermentation conditions. The relative importance of the cells growing in the aqueous phase on the overall kinetics was studied. The effect of interfacial tension, unoccupied interfacial area, and pseudosolubility on the specific growth was also studied. Results are presented and discussed here.
Concentration of antibiotics by reverse osmosis
Authors: Datta R. , Fries L. , Wildman G. T.
Published: December 2004

Reverse osmosis is shown to be a viable process for the concentration of highly labile antibiotic solutions. Mathematical n10deJs of antibiotic inactivation by chemical and biological contamination are proposed and correlated with experimental data. Procedures for obtaining high antibiotic recoveries are discussed.
Chemical procedures for enzyme immobilization on porous cellulose beads
Authors: Chen Li Fu , Tsao George T.
Published: December 2004

In a previous article, the method of preparation and the physical properties of porous (75 to 80% porosity) cellulose beads were described (Biotechnol. Bioeng., 18, 1057 (1976)). The present article reports that the chemical procedures employed for immobilizing enzymes on ordinary cellulose can be applied to the porous cellulose beads. The results showed more enzyme loading on the beads than ordinary cellulose. The choice of the procedures might also affect the mechanical strength of the cellulose beads.
Acid mine drainage treatment with rotating biological contactors
Authors: Olem Harvey , Unz Richard F.
Published: December 2004

A pilot scale rotating biological contactor (RBC) was set up near a coal mine at Hollywood, Penn. to evaluate ferrous iron, Fe(II), oxidation. Acid drainage from this mine entered the treatment unit which consisted of four sets of plastic disks affixed to a rotating central shaft. As the disks rotated half immersed in the flowing mine water, iron‐oxidizing bacteria, presumed to be Thiobacillus ferrooxidans, colonized the disk surfaces with an average population of 70,000 cells/cm2 and mediated the transformation of Fe(II) to the less soluble ferric state, Fe(III). Kinetics of microbial Fe(II) oxidation were established during an eleven month period of continuous pilot operation and were found to follow a concentration dependent first order relationship. Operating at an optimum disk rotation rate and hydraulic loadings of 2.7 and 5.4 gal/day‐ft2 (0.11 and 0.22 m3/day‐m2) resulted in the oxidation of an average 240 mg/liter influent Fe(II) to produce effluent Fe(II) of 2 and mg/liter, respectively. The RBC appears potentially useful as a first step in the total treatment of acid mine drainage.
Water recycle in biomass production processes
Authors: Topiwala H. H. , Khosrovi B.
Published: December 2004

Various aspects of process water recycle in a continuous flow fermentation process are analyzed. Simple mass balance equations in terms of product and feed components for a single‐stage reactor producing biomass are developed. Constraints on the recycle ratio, imposed by the efficiency of the dewatering stage, are examined. The recycle analysis is extended using a kinetic growth model incorporating water soluble product formation and growth inhibition. The potential effect of recycle on substrate conversion and product accumulation is also examined and the concept of a critical recycle ratio in fermentation processes is developed.
Isolation of lysozyme on chitosan
Authors: Muzzarelli Riccardo A. A. , Barontini Gaetano , Rochetti Roberto
Published: December 2004

Lysozyme has been immobilized on chitosan, a polyaminosaccharide, without using any intermediate reagent. The best pH conditions for operating the chitosan columns have been determined and the best eluting agent was found to be a 2% solution of propylamine. The lysozyme activity was determined after reacting lysozyme with the product of glycolchitin and Remazol Brilliant Blue R. The recovery of lysozyme from chicken egg white yields lysozyme with 55% activity.
Pore dimensions for accumulating biomass. I. Microbes that reproduce by fission or by budding
Authors: Messing R. A. , Oppermann R. A.
Published: December 2004

The relationship between the dimensions of a microbe and the accumulation of that microbe in porous, inorganic structures has been determined. That relationship is dependent upon the cell dimensions, the mode of reproduction, and the pore diameter of the material. In order to achieve high accumulation of microbes that reproduce by fission, at least 70% of the pores of an inorganic carrier should have pore diameters in the range of one times the smallest major dimension through five times the largest major dimension of the cell. To achieve the highest accumulation of microbes that reproduce by budding, at least 70% of the pores should have pore diameters in the range of one times the smallest dimension of the cell and less than four times the largest cell dimension. These relationships were established by varying the physical parameters of the carriers as well as their chemical composition.
Oxygen‐transfer rates and efficiencies in one‐ and two‐stage airlift towers
Authors: Orazem M. E. , Erickson L. E.
Published: December 2004

The primary consideration in fermentor design is the supply of oxygen to the growing microorganisms. The oxygen‐transfer characteristics of a two‐stage splitcylinder airlift tower were compared to those of a similar single‐stage airlift tower of equal liquid volume using a sodium sulfite–air system. At superficial gas velocities, from 720 to 1200 cm/min, no difference in KLa was apparent. The KLa was significantly larger in the two‐stage tower for a gas velocity between 1200 and 2728 cm/min. At 2728 cm/min a KLa of 25.2 min−1 was achieved in the two‐stage system, and at 2262 cm/min the two‐stage tower had a 54% larger KLa than the single stage. A comparison of dispersion‐volume based KLa showed a 27% larger value at a gas velocity of 2262 cm/min. The performance ratios for the two‐stage tower were larger than those for the single‐stage tower at oxygen‐transfer rates greater than 180 mmol/liter hr. A comparison of the data with literature values is presented.
Start‐up of chemostat: Application of fed‐batch culture
Authors: Yamané Tsuneo , Sada Eizo , Takamatsu Takeichiro
Published: December 2004

A time‐optimal strategy for start‐up of a chemostat has been established by applying Miele's extremization method based on Green's theorem. The start‐up time is always minimized by traveling along the uppermost boundary of the set of admissible domains on the (vx, μ) phase plane. The solutions are batch culture for monotone increasing growth kinetics and exponentially fed‐batch culture followed by batch culture for substrate‐inhibition kinetics. A time‐suboptimal start‐up strategy, exponentially fed‐batch culture operated the same μ as that of chemostate, is proposed as more feasible than and physiologically preferable to the time‐optimal strategies. The complete set of equations of operations necessary for performing each of the optimal and suboptimal start‐ups is formulated. Numerical comparisons on the basis of continuous operation giving maximum productivities of cell‐mass outputs show that differences in times required for start‐up between optimal and suboptimal strategies are small.
Analysis of fermentation processes using flow microflourometry: Single‐parameter observations of batch bacterial growth
Authors: Fazel‐Madjlessi Jila , Bailey J. E.
Published: December 2004

The laser flow microfluorometer (FMF) can determine the amounts of certain components in single cells at sample rates of several thousand cells per second. This technique has been employed to characterize Bacillus subtilis populations in batch fermentations with different inocula. Protein and distributions obtained by FMF analyses at different times during the batch have been decomposed using an optimized fit of summed subpopulation distributions. The results of these decomposition calculations, some of which have been approximately confirmed by independent microscopic observations, indicate cells relative numbers of single rods, cell chains, spores, and swollen rounded cells change dramatically during the entire fermentation including the stationary phase. The dynamics of these subpopulations may be related to secondary metabolite production.
Maximum cell productivity by repeated fed‐batch culture for constant yield case
Authors: Weigand W. A.
Published: December 2004

Optimal operation of repeatedly fed‐batch was determined by the continuous maximum principle for the constant yield case. The objective of maximum cell productivity for a fixed cell concentration was achieved by finding the substrate feeding policy that minimized the processing time. Analytical criteria for the optimal filling policy show that an exponential policy is optimum when the specific growth rate has a maximum, and also that operation in the simple repeated batch mode is optimum when the specific growth rate is monotonic increasing. Comparisons between optimal repeated fed‐batch culture and other modes of operation were made for the case of substrate‐inhibited growth. Cell productivity by repeated fed‐batch exceeds both batch and continuous operation for the case of low residual substrate concentration.
Characteristics of mechanically disrupted bakers' yeast in relation to its separation in industrial centrifuges
Authors: Mosqueira F. G. , Higgins J. J. , Dunnill P. , Lilly M. D.
Published: December 2004

The viscosity, density, and sedimentation characteristics of suspensions of whole and mechanically disrupted yeast cells were measured. Mechanical disruption increases the suspension viscosity and its non‐Newtonian behavior. Experiments showed a good correlation between laboratory‐ and industrial‐scale centrifugation results.
Peptide synthesis enzymatically catalyzed in a biphasic system: Water–water–immiscible organic solvent
Authors: Semenov Anatole N. , Berezin Ilya V. , Martinek Karel
Published: December 2004

Synthesis of a peptide bond is suggested to be enzymatically catalysed in a biphasic system “water–water‐immiscible organic solvent”. The pH dependence of the apparent equilibrium constant is studied for synthesis of N‐acetyl‐L‐tryptophanyl‐L‐leucine amide from N‐Acet‐Trp andL‐Leu‐NH2. The reaction was performed in the biphasic system ethyl acetate plus water [from 2 to 2% (v/v)] in the presence of α‐chymotrypsin. The suggested approach is preparative value: with the stoichiometric ratio of the reagents, [N‐Acet‐L‐Trp] = [L‐Leu‐NH2] = 2 × 10−3M, the yield is practically 100% (in water, with other conditions being the same, the yield is not over 01.%).
Cephalexin synthesis by partially purified and immobilized enzymes
Authors: Choi W. G. , Lee S. B. , Ryu Dewey D. Y.
Published: December 2004

An enzyme which catalyzes the synthesis of cephalexin fromD‐α phenylglycinemethylester (PGM) and 7‐amino‐3‐desacetoxy‐cephalosporanic acid (7‐ADCA) was prepared from Xanthomonas citri (IFO 3835) and partially purified 30‐fold by ammonium sulfate fractionation, DEAE‐cellulose, and Sepharose‐4B column chromatography. The Km values for 7‐ADCA, PGM, and cephalexin were determined as 11.1, 2.1, and 1.61 mM, respectively. The enzymatic cephalexin synthesis follows the reversible bi‐uni reaction kinetics. The equilibrium constant is influenced by the initial mole ratios of 7‐ADCA and PGM. The cephalexin hydrolysis is catalyzed by the same cephalexin synthesizing enzyme, but methanol does not participate in the hydrolytic reaction. The amount of enzyme in the reaction mixture affects the initial rate but does not influence the equilibrium product concentration. This cephalexin‐synthesizing enzyme was immobilized onto several adsorbents. Among these, Kaolin and bentonite showed a higher retention of enzyme activity and stability for reuse. The immobilized‐enzyme reaction kinetics were investigated and compared with those of the soluble enzyme. A rate expression for the enzymatic synthesis of cephalexin was derived. The results of computer simulation showed good agreement with the experimental results.
Bioengineering report: Fouling biofilm development: A process analysis
Authors: Characklis W. G.
Published: December 2004

Biofilm development at a surface is the net result of several physical, chemical, and microbial processes including the following: (1)transport of dissolved and particulate matter from the bulk fluid to the surface; (2) firm microbial cell attachment to the surface; (3) microbial transformations (growth, reproduction, etc.) within the biofilm resulting in production of organic matter; (4) partial detachment of the biofilm due primarily to fluid shear stress. This report presents a framework for analyzing the interrelated processes contributing to biofilm development. Some of the available rate and composition data are presented so that the relative process rates can be compared.
Microbial transformation of racemic hydantoins to D‐amino acids
Authors: Olivieri R. , Fascetti E. , Angelini L. , Degen L.
Published: December 2004

It has been shown that resting cells of Agrobacterium radiobacter catalyze a sequence of two stereospecific hydrolytic reactions leading to the complete transformation of racemic hydantoins to D‐amino acids. This report describes some properties of this new biocatalyst and its potential application for the production of some D‐amino acids, which are used as intermediates in the preparation of semisynthetic penicillin and cephalosporins.
Continuous cultivation of fission yeast: Classical and flow microfluorometry observations
Authors: Agar David W. , Bailey James E.
Published: December 2004

The fission yeast Schizosaccharomyces pombe was grown in glucose‐limited medium in a steady‐state continuous flow reactor. Changes in mean cell protein and RNA contents with growth rate are consistent with earlier observations under different conditions. Flow microfluorometry measurements of the frequency functions of DNA at different dilution rates show changes in coordination of DNA synthesis and cell separation. Shifting from batch growth to small dilution rates results in unusual cell aggregation which leads to multiple steady states at identical operating conditions.
Photochemical energy conversion system using immobilized chloroplasts
Authors: Kayano Hiromichi , Matsunga Tadashi , Karube Isao , Suzuki Shuichi
Published: December 2004

Immobilized 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

The 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

Optimizations 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

Different 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

Among 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

Development 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

The 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

Alcohol 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

Monod'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

A 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

Laboratory 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

Stereospecific 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

The 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

The 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

Cellulose 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

Inhibition 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

In 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

We 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

Lysine 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.