bluuebunny/crossref_metadata_2025 huggingface dataset:
Growth of three established cell lines on glass microcarriers
Authors: Carani James , Dame Michael , Beals Ted F. , Wass John A.
Published: December 2004

Three established cell lines were examined for growth on a newly developed microcarrier which consists of glass beads. The cells were simultaneously exmined for growth on commercially available microcarriers made from DEAE‐dextran and from plastic. Cell yields on the glass microcarriers were comparble to the cell yields on the commercially available products. Cells grown on the glass microcarriers were easily separated from the substratum by trypsinization (as were the cells grown on the plastic substratum) while the cells grown on the DEAE‐dextran particles were much more trypsin resistant. After removal of cells from the glass microcarriers, the cells reattached and spread out in plastic flasks as readily as cells harvested from monolayer. Scanning electron microscopy revealed dramatic differences in the appearence of the cell grown on the glass microcarriers and cells grown on the DEAE‐dextran microcarriers. On the glass microcarriers, cells attached to the substratum through lond, slender filopodia while on the DEAE‐dextran microcarriers, the entire edge of the cell appeared to be in contact with the substratum. This dissimilarity in attachment could underly the difference in sensitivity to trypsin‐mediated detachment. Finally, the glass microcarriers were washed after being used once and retested for their ability to support cell growth a second time. Nearly identical results were obtained with the reprocessed beads as with previously unused ones.
Inversion of sucrose by immobilized β‐fructooxidase in an integral reactor
Authors: Annesini M. Cristina , Gaudioso Domenico , Toro Luigi
Published: December 2004

Experimental runs on the inversion of sucrose by means of immobilized β‐fructooxidase are reported. External mass‐transfer and axial dispersion phenomena have been analyzed. It has been observed that external mass‐transfer plays a significative role in the overall kinetics, while axial dispersion phenomena are negligible.
Continuous transformation of benzaldehyde to benzyl alcohol by Rhodotorula mucilaginosa immobilized in an ultrafiltration cell
Authors: Wiśniewski J. , Winnicki T. , Majewska K.
Published: December 2004

Microbiological transformation of benzaldehyde accomplished by the fungus Rhodotorula mucilaginosa immobilized in the ultrafiltration cell was studied. A polysulfone membrane formed on a sintered PVC support was used for the separation of the transformation product from the cellular material. Kinetic investigations have led to results which are typical of continuously fed stirred tank reactors (CFSTR)—the value of the maximum reaction rate (Vmax) and apparent Michaelis constant (K′m) are practically independent of the substrate retention time (calculated in terms of the flow intensity value). A strong relationship was found to occur between Vmax and biomass concentration in the reactor. Study of the apparent enzyme stability shows that the decrease in the biocatalyst activity is chiefly caused by penetration of the cells through the membrane. The experimental results were approximated in terms of the adopted mathematical model. Based on this model, the half‐lives (t1/2) of enzyme activities were determined. The t1/2 value varies from 35 to 82 days and depends both on the permeate flux through the membrane and on the separation properties of the membrane.
Producton of single‐cell protein from cellulose by Aspergillus terreus
Authors: Miller T. Ferrell , Srinivasan V. R.
Published: December 2004

Cellulose fermentation studies were conducted with a thermotolerant strain of Aspergillus terreus. Batch cultivation of A. terreus using purified or complex cellulose showed that 80–88% of the available cellulose was utilized in 30–36 h with an average doubling time of 7.5–8.3 h. The protein content in the biomass ranged from 23 to 38%. Semicontinuous cultivation studies, in which 90% of the biomass was withdrawn at the end of growth cycle, indicated that 84% of added cellulose was utilized with the biomass containing 32% crude protein. No loss in cellulose consumption, growth rate, or protein production occurred through two growth cycles. Continuous cultivation of A. terreus showed that 78–84% cellulose consumption occurred over growth temperatures ranging from 35 to 45°C. Maximum specific growth rates (0.14 h−1) occurred at 40 and 45°C with a minimum doubling time of 4.9 h.
Development of a two‐phase combination fermenter for the conversion of cellulose to methane
Authors: Khan A. W. , Miller S. Shea , Murray William D.
Published: December 2004

Cellulose degradation to methane under continuous fermentation conditions was compared using fully mixed, fully mixed with solids return, sludge‐blanket, and fixed‐film fermenters. In fully mixed fermenters, a decrease in hydraulic retention time (HRT) of two weeks or less caused the wash out of anaerobes capable of converting volatile fatty acids to methane, while at increased feeding rates over 1 g/L day the rapid growth of cellulolytic anaerobes upset the balance between acid formation and its conversion to CH4. Circulation of cellulose and difficulty in settling of cellulose with attached bacteria imposed problems in the use of other types of fermenters. On the basis of information obtained from this study, a fermenter which combined a fully mixed phase for cellulose degradation and a fixed‐film phase with pre‐immobilized bacteria for converting fatty acids to CH4 in one vessel, was devised. Using this fermenter, a mixed culture converted cellulose to CH4 at 4.8 g/L day at a HRT of six days as compared to 0.7 g/L day at a HRT of 28 days in the fully mixed fermenter.
Pectinase from Trichoderma reesei QM 9414
Authors: Haltmeier T. , Leisola M. , Ulmer D. , Waldner R. , Fiechter A.
Published: December 2004

No. Abstrct.
Anaerobic treatment of raw domestic sewage at ambient temperatures using a granular bed UASB reactor
Authors: Lettinga G. , Roersma R. , Grin P.
Published: December 2004

Results obtained in a 120 liter 2 m high UASB‐reactor with raw domestic sewage and using a granular sugar beet waste cultivated seed sludge, reveal the feasibility of this type of anaerobic treatment for domestic sewage. Under dry weather conditions 65‐85% COD reduction can be achieved at temperatures in the range of 8‐20°C and at hydraulic loads as high as 2 m3 · m−3 · day−1. In the case of heavy rainfall the COD‐reduction drops to 50‐70% and occasionally, viz.at very low influent COD, even below 50%. The net methane production amounts to 7.1‐7.3 m3 · PE−1 · year−1, and the excess sludge production ranges form 5.0‐8.6 kg TS · PE−1 · year−1. Regarding the results obtained anaerobic treatment of raw sewage not only looks an attractive proposition for tropic areas but also for moderate climatic areas.
Ethanol production from fodder beets
Authors: Kosaric N. , Wieczorek A. , Kliza S.
Published: December 2004

Various yeasts such as two strains of Saccharomyces cerevisiae, Saccharomyces diastaticus, and Kluyveromyces marxianus were investigated for their ability to ferment fodder beet juice to alcohol. Juice extracted from fodder beet roots without any additives was used as a fermentation substrate. The fermentation kinetic parameters were determined and compared for each species of yeast tested. The best species for fodder beet juice fermentation was chosen and products obtained by fermentation of one hectare of fodder beet plants are given.
Effect of pretreatment on the hydrolysis of cellulose by Penicillium funiculosum cellulase and recovery of enzyme
Authors: Rao Mala , Seeta R. , Deshpande Vasanti
Published: December 2004

Penicillium funiculosum produces a complete cellulase which brings about 97% hydrolysis of cotton and has high β‐glucosidase, xylanase, laminarinase, and lichenase activities. This article deals with the effect of different pretreatments on the hydrolysis of sugarcane bagasse by P. funiculosum enzymes and the recovery of enzyme from the insoluble residues. Enzymic saccharification of bagasse pretreated with hot 1N NaOH followed by neutralization with HCI and steam treated under pressure (7 kg/cm2) gave 63 and 59% saccharification, respectively, in 48 h. Hemicellulose is not lost in these pretreatments. With a 30% slurry of steam‐treated bagasse, a semisolid mass containing 14% sugar was obtained. A 90% recovery of CMCase, β‐glucosidase, and filter paper activity from the hydrolysates was obtained under the following conditions: (1) maintaining the ratio of enzyme to substrate high by stepwise addition of substrate, (2) brief grinding of the residual substrate with glass powder, and (3) addition of 0.4% Tween‐80 to the eluting buffer. The high recovery of cellulolytic enzymes indicates that the adsorption of these enzymes on cellulose is not irreversible.
Effect of oxygen removal on hydrogen photoproduction in algae
Authors: Rosenkrans Addison M. , Rosen Michael M. , Krasna Alvin I.
Published: December 2004

Hydrogen photoproduction from water in Scenedesmus cells requires removal of oxygen by a reagent in contact with the algae. Both deoxyhemoglobin and deoxymyoglobin stimulated hydrogen production by reversible absorption of oxygen. Their effectiveness was greatly increased when other oxygen‐combining reagents were present in a separate chamber with deoxyhemoglobin and deoxymyoglobin serving as reversible oxygen transfer agents.
Maximum photosynthetic efficiency: A problem to be resolved
Authors: Pirt S. J.
Published: December 2004

The great disarray in the measurements of the maximum efficiency of conservation of light energy in photosynthesis is an outstanding problem in the development of photosynthetic biotechnology. The short‐term measurements of the efficiency based on O2 release by suspensions of cells or chloroplasts have given minimum quantum demands between 4 and 12 hv/O2. The defect of the short term measurements is that the effects of growth conditions, which can alter the efficiency by a factor of 2, have been generally ignored. In contrast, the steady‐state growth method, which depends on measurement of the maximum growth yield in photosynthesis, ensures that growth and photosynthesis are normally coupled. This growth method indicates that the minimum quantum demand lies in the relatively narrow range of 5.3 to 8.6 hv/O2. The question of whether the minimum quantum demand is less or greater than 8 hv/O2 is a crucial test for present theoretical concepts of the conversion of radiant energy to chemical energy in photosynthesis. To obtain the definitive maximum value more rigorously controlled measurements of photosynthetic efficiency in growing organisms are essential.
Continuous production of high‐glucose syrup by chitin‐immobilized amylase
Authors: Flor Perfecto Q. , Hayashida Shinsaku
Published: December 2004

A simple method of preparing a chitin‐immobilized α‐amylase and glucoamylase from the protease‐ and glycosidase‐less Mutant HF‐15 of Aspergillus awamori var. kawachi was developed and used for the production of high‐glucose syrup. The glucoamylase was tightly bound onto chitin without the aid of a crosslinking agent because the enzyme contained a specific binding site for chitin. Continuous production of high glucose concentrate from a highly concentrated α‐amylasetreated gelatinized starch substrate (about 45% total solids) was undertaken successfully with the use of a column‐packed chitin‐immobilized amylase. The activity of the column was stable for more than 20 days of continuous operation and the product was found to be only glucose with an average dextrose equivalent value of more than 97%. The final product showed no isomaltose or panose contamination, indicating that the immobilized amylase had no transglucosidation activity. The immobilized amylase was most active in the conversion of gelatinized starch to glucose at 55°C and pH 2.5 to 5.0. Drying the chitin‐immobilized amylase resulted in the decrease of activity and shortening of storage life, whereas a storage life of up to 80 days was attained without affecting its original activity when kept under moist condition at 4°C.
Kinetic study on enzymatic hydrolysis of cellulose by cellulose from Trichoderma viride
Authors: Ohmine Kazuo , Ooshima Hiroshi , Harano Yoshio
Published: December 2004

Pure cellulose (Avicel) was hydrolyzed batchwise at 50°C and pH 4.8 by cellulase from Trichoderma viride (Meicelase CEP). Then the effects of the crystallinity of cellulose as well as the thermal deactivation and product (cellubiose and glucose) inhibition to cellulose on the hydrolysis rate were quantitatively investigated. While these factor had evidently retarded the enzymatic hydrolysis of cellulose to a significant extent, the hydrolysis rates observed could not be explained. For practical purposes, an empirical, simple rate expression was developed which included only one parameter: a overall rate retardation constant. This empirical rate expression held for the hydrolysis of at least two kind of cellulosic materials: Avicel and tissue paper.
Thienamycin production by immobilized cells of Streptomyces cattleya in a bubble column
Authors: Arcuri E. J. , Nichols J. R. , Brix T. S. , Santamarina V. G. , Buckland B. C. , Drew S. W.
Published: December 2004

A novel 2.0‐L columnar reactor has been developed for the production of thienamycin by cells of Streptomyces cattleya attached to celite particles. Successful immobilization of cells was achieved by operating the column continuously at a high dilution rate during the growth phase. Scanning electron micrographs of the celite particles indicate the involvement of subcellular fibrils in the attachment of cells to the solid surfaces. Reactor operation was divided into two distinct phases–a growth phase and a production phase. The kinetics of attached growth and thienamycin production were found to be strongly influenced by nutrient concentrations. The influences of nutrient concentration on CO2 production and thienamycin production during both the growth phase and the production phase are discussed.
Bacterial fermentation of cellulose: Effect of physical and chemical parameters
Authors: Armstrong David W. , Martin Stanley M.
Published: December 2004

Acetivibrio celluloyticus converts cellulose directly to ethanol, acetate, H2, and CO2. The effects of various physical and chemical parameters, and their interdependence, including pH, temperature, redox, and ethanol toxicity on this fermentation, were studied. Controlling pH at 6.8 favored a predominance of ethanol over acetate. Supplementation of the medium with additional reductant, concomitant with a lower redox potential, incresed ethanol formation. Results from ethanol‐challenged cultures indicated that cell lysis occurs with growing but not with nongrowing cells. A stable strain was adapted for growth in ethanol concentrations almost sevenfold greater than the parent organism.
Production of sugars from wood using high‐pressure hydrogen chloride
Authors: Antonoplis R. A. , Blanch H. W. , Freitas R. P. , Sciamanna A. F. , Wilke C. R.
Published: December 2004

Saturating wood particles with HCl gas under pressure was found to be an effective pretreatment prior to subjecting wood to dilute acid hydrolysis. Pretreament is necessary to release sugars from wood because of the tight lattice structure of cellulose. The HCl gas makes the cellulose more susceptible to subsequent acid hydrolysis and the glucose yield is doubled when dilute acid hydrolysis is preceded by HCl saturation at high pressure. The saturation was most effectively performed in a fluidized bed reactor, with pure HCl gas fluidizing an equal volume of ground wood plus inert particles. The fluidized bed effectively dissipated the large amount of heat released upon HCl absorption into the wood. Batch reaction times of 1 h at 315 psia gave glucose yields of 80° and xylose yields of 95° after dilute acid hydrolysis. A model was developed which proposed gas diffusing through the solid as limiting the reaction rate and this was found to effectively describe the HCl‐wood reaction in the fluidized bed. The HCl was found to form a stable adduct with the lignin residue in the wood, in a ratio of 3.33 mole of lignin monomer. The adduct was broken upon the addition of water.
Effect of cellobiose, glucose, ethanol, and metal ions on the cellulase enzyme complex of Thermomonospora fusca
Authors: Ferchak John D. , Pye E. Kendall
Published: December 2004

The saccharification of cellulosic substrates by cellulase from Thermomonospora fusca, strain YX, was influenced by the presence of various substances. Cellobiose was strongly inhibitory, reducing the activity against swollen cellulose to 25% at 5% concentration. Glucose had much less effect, reducing activity to 40% at 20% concentration. Ethanol was found to be only slightly inhibitory to the cellulase, reducing activity by about 15% at 6% concentration, but much more inhibitory to the cell‐bound β‐glucosidase activity. Of the numerous metal ions examined, Ca2+ and Co2+ at 0.1mM‐1.0mM concentration were found to be slightly activating under assay conditions, while 1.0mM Pb2+ and Hg2+ were the most inhibitory ions. The implications of these results for the design of commercial processes for ethanol production from cellulose are discussed.
Enhancing gas‐liquid mass transfer rates in non‐newtonian fermentations by confining mycelial growth to microbeads in a bubble column
Authors: Gbewonyo K. , Wang D. I. C.
Published: December 2004

The performance of a penicillin fermentation was assessed in a laboratory‐scale bubble column fermentor, with mycelial growth confined to the pore matrix of celite beads. Final cell densities of 29 g/L and penicillin titres of 5.5 g/L were obtained in the confined cell cultures. In comparison, cultures of free mycelial cells grown in the absence of beads experienced dissolved oxygen limitations in the bubble column, giving only 17 g/L final cell concentrations with equally low penicillin titres of 2 g/L. The better performance of the confined cell cultures was attributed to enhanced gas liquid mass transfer rates, with mass transfer coefficients (kLa) two to three times higher than those determined in the free cell cultures. Furthermore, the confined cell cultures showed more efficient utilization of power input for mass transfer, providing up to 50% reduction in energy requirements for aeration.
Synergistic action of α‐amylase and glucoamylase on hydrolysis of starch
Authors: Fujii Michihiro , Kawamura Yosinori
Published: December 2004

Synergistic action of α‐amylase and glucoamylase on hydrolysis of starch is modeled by the kinetic equations presented in this paper. At the early stage of the reaction α‐amylase acts as a contributor of newly formed nonreducing ends of starch molecules to glucoamylase by splitting the original starch molecules. This is expressed by the simultaneous differential equations which consist of each rate equation for α‐amylase and glucoamylase. After the molecular weight of the substrate decreases to the value of about 5000, which is obtained experimentally in this work, the action of α‐amylase can be neglected and the rate of formation of glucose obeys only the rate equation for glucoamylase.
Kinetics of ethanol inhibition in alcohol fermentation
Authors: Luong J. H. T.
Published: December 2004

The inhibitory effect of ethanol on yeast growth and fermentation has been studied for the strain Saccharomyces cerevisiae ATCC No. 4126 under anaerobic batch conditions. The results obtained reveal that there is no striking difference between the response of growth and ethanol fermentation. Two kinetic models are also proposed to describe the kinetic pattern of ethanol inhibition on the specific rates of growth and ethanol fermentation:

The maximum allowable ethanol concentration above which cells do not grow was predicted to be 112 g/L. The ethanol‐producing capability of the cells was completely inhibited at 115 g/L ethanol. The proposed models appear to accurately represent the experimental data obtained in this study and the literature data.
Ethanol fermentation of crude acid hydrolyzate of cellulose using high‐level yeast inocula
Authors: Chung I. S. , Lee Y. Y.
Published: December 2004

High‐level yeast inocula was investigated as a means of overcoming the toxicity problem in ethanol fermentation of acid hydrolyzate of wood cellulose. When the inoculum level exceeded 108 initial cells/mL, 50% of the yeast cells survived the initial cell death period during which furfural and HMF were depleted. The fermentation thus proceeded to completion by virtue of cell regrowth. The specific ethanol productivity in batch fermentation on the basis of viable cells was comparable to that of pure glucose fermentation. Continuous fermentation with cell recycle was superior to batch fermentation in that there was no overall cell decline and the ethanol yield was substantially higher. The maximum ethanol productivity in continuous fermentation was 4.9 g/L h and it occurred at a dilution rate of 0.24 hr−1.
Acid hydrolysis of sweet potato for ethanol production
Authors: Kim K. , Hamdy M. K.
Published: December 2004

Studies were conducted to establish optimal conditions for the acid hydrolysis of sweet potato for maximal ethanol yield. The starch contents of two sweet potato cultivars (Georgia Red and TG‐4), based on fresh weight, were 21.1 ± 0.6% and 27.5 ± 1.6%, respectively. The results of acid hydrolysis experiments showed the following: (1) both hydrolysis rate and hydroxymethylfurfural (HMF) concentration were a function of HCL concentration, temperature, and time; (2) the reducing sugars were rapidly formed with elevated concentrations of HCl and temperature, but also destroyed quickly; and (3) HMF concentration increased significantly with the concentration of HCl, temperature, and hydrolysis time.

Maximum reducing sugar value of 84.2 DE and 0.056% HMF (based on wet weight) was achieved after heating 8% SPS for 15 min in 1N HCl at 110°C. Degraded 8% SPS (1N HCl, 97°C for 20 min or 110°C for 10 min) was utilized as substrate for ethanol fermentation and 3.8% ethanol (v/v) was produced from 1400 mL fermented wort. This is equal to 41.6 g ethanol (200 proof) from 400 g of fresh sweet potato tuber (Georgia Red) or an ethanol yield potential of 431 gal of 200‐proof ethanol/acre (from 500 bushel tubers/acre).
Chemical and enzymic pretreatment of corn stover to produce soluble fermentation substrates
Authors: Tanaka Mitsuo , Robinson Campbell W. , Moo‐Young Murray
Published: December 2004

Corn stover was pretreated with various chemical agents, including sodium hydroxide, sulfuric acid, ethylenediamine, n‐butylamine (either alone or in solution with methanol), and acetonitrile or ethanol containing hydrochloric acid. Of these chemicals, n‐butylamine was the best reagent for pretreatment of corn stover, considering the degree of loss of total carbohydrate, delignification, cumulative weight loss, cumulative yield of reducing sugars per original total carbohydrate, and the potential ease of recovery and reuse of reagent. In comparison to the other reagents tested, n‐butylamine (n‐BA) selectively delignified corn stover. The best conditions were as follows: a 12‐h presoak of about a 155 g dry wt/L slurry (1 mm average particle size) in 100% n‐BA at room temperature, followed by 30 min of refluxing (86.5°C) with 40% (w/w) n‐BA–distilled water solution. The cumulative yield of reducing sugars after enzymic hydrolysis was 44.5% of the original total carbohydrate and the cumulative total weight loss (dry basis) was 59%. Degradative loss of total carbohydrate during pretreatment was not detected.
Gas holdup and overall volumetric oxygen transfer coefficient in airlift contactors
Authors: Bello R. Ade , Robinson Campbell W. , Moo‐Young Murray
Published: December 2004

The two major types of airlift contactors, concentric‐tube and external‐loop, were investigated for their gas holdup (riser and downcomer) and overall mass transfer characteristics. Results obtained in batch charges of tap water and 0.15 kmol/m3 NaCl solution are reported for external‐loop airlift contactors having downcomer‐to‐riser cross‐sectional area ratios, Ad/Ar, ranging from 0.11 ≤ Ad/Ar ≤ 0.69 and for concentric‐tube types in the range 0.13 ≤ Ad/Ar ≤ 0.56.

The results are compared and contrasted for the two types of airlift contactors and also with corresponding results obtained in a bubble column (Ad/Ar = 0). Both the riser gas holdup, (εG)r, and the overall volumetric mass transfer coefficient, (KLaD)T, were found to increase with increasing gas superficial velocity and the corresponding specific gassing power input, (PG/VD)T. However, at a specified power input both (εG)r and (KLaD)T decreased with increasing Ad/Ar due to a resultant increase in circulating liquid velocity. Unifying generalized correlations for both types of airlift contactors are given for both (εG)r and (KLaD)T. These correlations are expected to be applicable as well to continuous‐liquid flow bubble columns at comparable liquid velocities.
Purification and immobilization of rabbit liver aldehyde oxidase
Authors: Angelino Steven A. G. F. , Müller Franz , van der Plast Henk C.
Published: December 2004

Aldehyde oxidase (E.C. 1.2.3.1) was isolated from rabbit liver and two potential bioaffinity ligands, i.e., 3‐aminocarbonyl‐1‐benzyl‐6‐methylpyridinium bromide and 3‐aminocarbonyl‐1‐benzyl‐4,6‐dimethylpyridinium chloride, were tested for their applicability in a purification procedure for this enzyme. Various supports and different coupling methods were investigated for the immobilization of aldehyde oxidase. Adsorption to n‐hexyl‐ and n‐octylamine‐substituted Sepharose 4B and DEAE Sepharose 6B gave the best retention of aldehyde oxidase activity. The storage stability of free enzyme and enzyme immobilized to n‐octylamine‐substituted Sepharose 4B was studied in several buffers at pH 7.8 and 9.0. This showed that the stability of immobilized enzyme was much less than that of free enzyme. The apparent operational stability of the immobilized enzyme preparation, however, improved substantially compared to soluble enzyme, although the corresponding product yield is still very poor. Coimmobilization of catalase and/or superoxide dismutase provided no significant increase of the apparent operational stability and product yield. A positive effect on both parameters was found for aldehyde oxidase‐n‐alkylamine Sepharose 4B preparations by increasing the amount of enzyme adsorbed per unit weight of support, whereas the productivity of these preparations remained about constant.
Oxygen transfer in liquids
Authors: Stejskal Jiřrí , Potůček František
Published: December 2004

In the laboratory‐type airlift tower reactor oxygen transfer from air in tap water and/or polyacrylamide solutions (Neuperm WF) was studied. In order to characterize the system, volumetric coefficient of oxygen transfer was determined by the gassing‐out method. Two arrangements of the airlift tower reactor were compared, namely the reactor with and without motionless mixer. In addition, mean relative gas holdup and gas power output were determined for both arrangements.
Ethanol productions from D‐xylose and cellobiose by Kluyveromyces cellobiovorus
Authors: Morikawa Y. , Takasawa S. , Masunaga I. , Takayama K.
Published: December 2004

Yeasts capable of fermenting both D‐xylose and cellobiose to ethanol were screened. Of 213 species of yeasts surveyed, Kluyveromyces cellobiovorus sp. nov., a new species belonging to genus of Kluyveromyces, was selected as the sole strain. This strain accumulated 32, 22, and 19 g/L of ethanol from 8% glucose, D‐xylose, and cellobiose, respectively. It was also shown that this strain produced ethanol from the enzymatic bagasse hydrolysate containing hexoses and pentoses more efficiently than Saccharomyces cerevisiae.
Conditions for the phase–plane analysis of feedback control of chemostat
Authors: Shimizu Kazuyuki , Matsubara Masakazu
Published: December 2004

This article deals with the effect of P‐control and Plcontrol on the dynamic behavior of a continuous stirred tank fermentor (CSTF). Several conditions concerning the stability of steady states and the existence of limit cycles of the closed‐loop system are derived. The application is made to the substrate inhibition model with variable yield coefficient. It is shown how the unfavorable phase–plane trajectories of the uncontrolled CSTF can be altered to favorable ones by the appropriate choice of control parameters based on the conditions derived.
The immobilization of enzymes and cells of Bacillus stearothermophilus onto poly(maleic anhydride/styrene)–Co‐polyethylene and poly(maleic anhydride/vinyl acetate)–Co‐polyethylene
Authors: Beddows C. G. , Gil H. G. , Guthrie J. T.
Published: December 2004

The graft copolymer, poly(maleic anhydride/styrene)‐co‐polyethylene was prepared. The copolymer immobilized bovine serum albumin (BSA), but the amount coupled appeared to be effected by the amount of styrene in the graft copolymer, temperature, and pH of the coupling medium. Competition existed between hydrolysis of the grafted anhydride groups and the protein. A graft copolymer with 66% add‐on immobilized 4.5 mg/glucose oxidase/g copolymer, 4.6 mg alkaline phosphates/g copolymer and 0.2 mg cell of Bacillus stearothermophilus/g copolymer. A number of copolymers containing poly(maleic anhydride/vinyl acetate)–co‐polyethylene were prepared to cover a range of grafting levels. These immobilized larger quantities of BSA, alkaline phosphatase, and cells of B. stearothermophilus than did the styrene graft copolymer. The copolymer was also hydrolyzed to release the hydroxyl group from the poly(vinyl acetate) component of the grafted chains. Using p‐benzoquinone as the “activating agent,” the copolymer coupled to BSA and to acid phosphatase. Using p‐toluene‐sulfonyl chloride, the copolymer was very effective in immobilizing trypsin.
A mechanistic analysis of the inoculum requirement for the cultivation of mammalian cells on microcarriers
Authors: Hu W. S. , Meier J. , Wang D. I. C.
Published: December 2004

For the cultivation of mammalian cells on microcarriers a minimum inoculum concentration is required to initiate cell attachment and subsequent cell growth. A critical cell number model has been proposed to elucidate the mechanism of the inoculum requirement. In this model it was hypothesized that after inoculation a critical number of cells per microcarrier is required for normal growth to occur; failure to acquire enough cells will impede cell growth. This critical cell number model was expressed mathematically and used to simulate cell distribution and growth on microcarriers under different cultivation conditions. By comparing the simulated growth kinetics with the experimental results, the actual critical cell number per microcarrier was identified. The critical number could be reduced by employing an improved medium for the cultivation.
Filament formation and ethanol production by Zymomonas mobilis in adsorbed cell bioreactors
Authors: Daugulis Andrew J. , Krug T. A. , Choma C. E. T.
Published: December 2004

Zymomonas mobilis immobilized on microporous ion exchange resins has previously been shown to allow the attainment of high ethanol productivities in packed‐bed bioreactors. The formation of bacterial filaments after several days of continuous operation, however, had resulted in excessive pressure increases across the reactor bed. The present work examines techniques for controlling filament formation by Z. mobilis in two reactor sizes (161 mL and 7.85 L) and a feed glucose concentration of 100 g/L. By controlling the fermentation temperature at 20–25°C it has been possible to eliminate filament formation by Z. mobilis and to operate the larger bioreactor for 232 h with an ethanol productivity of 50 g/L h (based on total reactor volume). The rate of ethanol production has been shown to be very sensitive to temperature in the range 20–30°C, and it is likely that slightly higher temperatures than those used in this study will improve ethanol productivity while still permitting long‐term operation.
The effect of pH on nitrogen supply, cell lysis, and solvent production in fermentations of Clostridium acetobutylicum
Authors: Roos Joseph W. , McLaughlin Joseph K. , Papoutsakis Eleftherios T.
Published: December 2004

In batch fermentations of C. acetobutylicum, with 5 g/L yeast extract and 50mM glucose, the ratio of ammonium to glucose affected solvent production when the pH was left to vary uncontrolled from 4.5 to 3.65. High solvent production was observed for a low ratio. When the pH was controlled at 4.5, only acids were produced for all ratio values. At a low ammonium‐to‐glucose ratio, solvents were produced when the pH was controlled at 3.7. Acids only were produced for a low ratio value at pH 4.0 or for a high ratio value at pH 3.7. In continuous cultures, mostly acids were produced under glucose limitation, but solvents were produced under nitrogen limitation. It was concluded that the nitrogen availability controls solvent production and that the pH affects the availability of organic nitrogen. Biomass autolysis at the stationary phase of batch cultures was reversibly inhibited at pH values less than 3.8. In batch fermentations, the overall molar growth yields on ATP (YATP) varied from 5.5 to 9.0 and the transient yields from 5.5 to 15.5. In continuous cultures, the YATP values varied from 5.5 to 14.7 under glucose limitation, and from 6.1 to 9.3 under nitrogen limitation. The YATP depended on the ammonium to glucose ratio and the culture pH, but did not show the usual dependence on the specific growth rate in batch cultures. The experiments seem to confirm the hypothesis that solvent production is controlled by the demand and availability of ATP.
Scale‐down and optimization studies of the gluconic acid fermentation by Gluconobacter oxydans
Authors: Oosterhuis N. M. G. , Kossen N. W. F. , Olivier A. P. C. , Schenk E. S.
Published: December 2004

To simulate production‐scale conditions of gluconic acid fermentation by Gluconobacter oxydans, different experimental setups are presented in this study. From the determination of the time constants of a production‐scale reactor, it can be concluded that mixing and oxygen transfer are the rate‐limiting mechanisms. This results in oxygen concentration gradients which were simulated in a one‐compartment reactor in which the oxygen concentration was fluctuated by a fluctuated gassing with air and nitrogen. It could be concluded that only very long periods of absence of oxygen (ca. 180 s) results in lower specific oxygen uptake rates by Gluconobacter oxydans. From scale‐down studies carried out in a two‐compartment system to simulate a production‐scale reactor more accurately, it could be concluded that not only the residence time in the aerated part of the system is important, but the liquid flow in between the different parts of the reactor is also an essential parameter. It could also be concluded that the microorganisms are not influenced negatively by the fluctuated oxygen concentrations with respect to their maximal oxidation capacity. The two‐compartment system can also be used for optimization experiments in which the “aerated” compartment was gassed with pure oxygen. From these experiments it was concluded that also a short residence of the cells at high oxygen concentrations diminished the growth and product formation rates. These experiments show the necessity of the scale‐down experiments if optimization is carried out. The two‐compartment system presented in this study is a very attractive tool for reliable scale‐down experiments.
Control of ammonium concentration in Escherichia coli fermentations
Authors: Thompson B. G. , Kole M. , Gerson D. F.
Published: December 2004

A control system has been devised for the maintenance of stable ammonium concentrations throughout a fedbatch fermentation. The control system is based on an ammonia gas‐sensing electrode that monitors a pH‐adjusted effluent stream from the fermentor. To overcome the time lag between the fermentor and the electrode, feedback control included metered flows of ammonium to both the fermentor and the electrode vessel. The system was used to study the growth of Escherichia coli B (ATCC 11303) at controlled ammonium concentrations of 5 to 200mM. Apparent specific growth rates, biomass and protein production, and glucose yields were essentially constant from 5 to 170mM. Above 170mM ammonium growth was inhibited. As ammonium concentration decreased from 170 to 5mM, ammonium yields increased from 1 to 24 g cell dry wt/g ammonium utilized. The results demonstrate that control of ammonium concentrations at levels so low that ammonium would be exhausted in batch fermentations can significantly increase overall ammonium yields.
Agitation and pressure effects on acetone‐butanol fermentation
Authors: Doremus Michael G. , Linden James C. , Moreira Antonio R.
Published: December 2004

Batch fermentations were run at varying agitation rates and were either pressurized to 1 bar (15.2 psig) or nonpressurized. Agitation and pressure both affect the level of dissolved hydrogen gas in the media, which in turn influences solvent production. In nonpressurized fermentations volumetric productivity of butanol increased as the agitation rate decreased. While agitation had no significant effect on butanol productivity under pressurized conditions, overall butanol productivity was increased over that obtained in the nonpressurized runs. Maximum butyric acid productivity, however, was found to occur earlier and increased as agitation increased. Peak hydrogen productivity occurred simultaneously with peak butyric acid productivity. The proporation of reducing equivalents used in forming the above products was determined using a redox balance based on the fermentation stoichiometry. An inverse relationship between the final concentrations of acetone and acetoin was found in all fermentations studied. The results show that agitation and pressure are important parameters for solvent productivity in acetone‐butanol fermentation.
Enhanced polysaccharide recovery from agricultural residues and perennial grasses treated with alkaline hydrogen peroxide
Authors: Gould J. Michael
Published: December 2004

Pretreatment of lignocellulosic materials with alkaline hydrogen peroxide greatly increases their susceptibility to enzymatic cellulose hydrolysis. During the course of the pretreatment reaction (18 h), the pH rises slowly, increasing from pH 11.5 to a final pH > 12. As a result, most of the hemicellulose in the lignocellulosic substrate becomes solubilized. Maintaining the reaction pH near the optimum of 11.5 prevents hemicellulose solubilization and decreases the time required for effective pretreatment to about 6 h. Alkaline peroxide pretreatment is most effective on lignocellulose from monocotyledonous plants, especially members of the family Gramineae. Enzymatic saccharification efficiencies > 90% of theoretical were attained from high yielding perennial grasses such as big bluestem (Andropogon gerardi) and Indian grass (Sorghastrum nutans) after alkaline peroxide pretreatment.
The β‐xylosidase of Thermomonospora
Authors: Ristroph D. L. , Humphrey A. E.
Published: December 2004

This study is concerned with characterizing cell‐bound inducible β‐xylosidase produced by a strain of the thermophilic bacterial genus Thermomonospora. A crude preparation of this enzyme recovered from sonicated cells of this organism displayed high activity against paranitrophenyl‐β‐xylopyranoside over a pH range of 5.5‐7.7. The temperature optimum, based on a 30‐min assay of activity, at pH 6.5 was 70°C. The crude enzyme had a thermal half‐life of approximately 1 week at 55°C and pH 6.5. Xylose inhibited the enzyme. Values of Km and Vmax are estimated from the reaction rate data as 0.82 mM and 8 U/L, respectively.
An immobilized cell reactor with simultaneous product separation. I. Reactor design and analysis
Authors: Dale M. C. , Okos M. R. , Wankat P. C.
Published: December 2004

A four‐phase reactor–separator (gas, liquid, solid, and immobilized catalyst) is proposed for fermentations characterized by a volatile product and nonvolatile substrate.In this reactor, the biological catalyst is immobilized onto a solid column packing and contacted by the liquid containing the substrate.A gas phase is also moved through the column to strip the volatile product into the gas phase. The Immobilized Cell Reactor–Separator (ICRS) consists of two basic gas–liquid flow sections: a cocurrent “enricher” followed by a countercurrent–“stripper”.

In this article, an equilibrium stage model of the reactor is developed to determine the feasibility and important operational variables of such a reactor–separator. The ICRS concept is applied to the ethanol from whey lactose fermentation using some preliminary immobilized cell reactor performance data. A mathematical model for a steady‐state population based on an adsorbed monolayer of cells is also developed for the reactor. The ICRS model demonstrated that the ICRS should give a significant increase in reactor productivity as compared to an identically sized Immobilized Cell Reactor (ICR) with no separation. The gas‐phase separation of the product also allows fermentation of high inlet substrate concentrations. The model is used to determine the effects of reactor parameters on ICRS performance including temperature, pressure, gas flow rates, inlet substrate concentration, and degree of microbial product inhibition.
An immobilized cell reactor with simultaneous product separation. II. Experimental reactor performance
Authors: Dale M. C. , Okos M. R. , Wankat P. C.
Published: December 2004

The simultaneous separation of volatile fermentation products from product‐inhibited fermentations can greatly increase the productivity of a bioreactor by reducing the product concentration in the bioreactor, as well as concentrating the product in an output stream free of cells, substrate, or other feed impurities. The Immobilized Cell Reactor–Separator (ICRS) consists of two column reactors: a cocurrent gas–liquid “enricher” followed by a countercurrent “stripper” The columns are four‐phase tubular reactors consisting of (1) an inert gas phase, (2) the liquid fermentation broth, (3) the solid column internal packing, and (4) the immobilized biological catalyst or cells. The application of the ICRS to the ethanol‐from‐whey‐lactose fermentation system has been investigated. Operation in the liquid continuous or bubble flow regime allows a high liquid holdup in the reactor and consequent long and controllable liquid residence time but results in a high gas phase pressure drop over the length of the reactor and low gas flow rates. Operation in the gas continuous regime gives high gas flow rates and low pressure drop but also results in short liquid residence time and incomplete column wetting at low liquid loading rates using conventional gas–liquid column packings. Using cells absorbed to conventional ceramic column packing (0.25‐in. Intalox saddles), it was found that a good reaction could be obtained in the liquid continuous mode, but little separation, while in the gas continuous mode there was little reaction but good separation. Using cells sorbed to an absorbant matrix allowed operation in the gas continuous regime with a liquid holdup of up to 30% of the total reactor volume. Good reaction rates and product separation were obtained using this matrix. High reaction rates were obtained due to high density cell loading in the reactor. A dry cell density of up to 92 g/L reactor was obtained in the enricher. The enricher ethanol productivity ranged from 50 to 160 g/L h while the stripper productivity varied from 0 to 32 g/L h at different feed rates and concentrations. A separation efficiency of as high as 98% was obtained from the system.
Mathematical modelling of growth and substrate conversion of Zymomonas mobilis at 30 and 35°C
Authors: Jöbses I. M. L. , Egberts G. T. C. , van Baalen A. , Roels J. A.
Published: December 2004

Zymomonas mobilis was grown in continuous cultures at 30 and 35°C. The specific substrate consumption rates at 35°C were higher than those at 30°C. An unstructured mathematical model based on the linear equation for substrate consumption provided a statistically adequate description for cultures grown at 35°C but not for cultures grown at 30°C. A structured two‐compartment model described growth and substrate consumption well at both temperatures. Some theoretical and practical aspects of the two‐compartment model are discussed.
Microcalorimetric study of cellulose degradation by Cellulomonas uda ATCC 21399
Authors: Dermoun Z. , Belaich J. P.
Published: December 2004

A newly designed batch calorimeter was used to investigate the degradability of some celluloses having varying degrees of crystallinity. The PTC of an aerobic culture of Cellulomonas uda ATCC 21399 obtained revealed a diauxic growth which is attributed to the presence of hemicellulose contaminating Avicel and MN300 cellulose. The microcrystalline celluloses used were not completely utilized, whereas amorphous cellulose was easily metabolized, indicating that under the growth conditions used here, the physical structure of cellulose strongly influenced its microbial degradability. An equivalent growth yield of ca. 0.44 g/g was found with all the substrates used. The heat evolved by metabolism of 1 g cellulose was ‐5.86 kJ/g, a value similar to that obtained with glucose culture. The growth rate was the only variable parameter. The data obtained showed as expected that the hydrolysis product of cellulose was consumed in the same way as that of glucose and that the only limiting factor to the biodegradability of cellulose was the breakdown of the polymeric substrate. It is concluded that data obtained with glucose metabolism can be used to evaluate the extent of cellulose degradation.
Shear stress effects on human embryonic kidney cells in Vitro
Authors: Stathopoulos N. A. , Hellums J. D.
Published: December 2004

Human embryonic kidney cells grown as an attached, confluent monolayer on a flat substrate were subjected to steady, uniform laminar flow of medium in a specially designed chamber in which flow patterns and shear stress are accurately defined and controlled. Experiments were performed for shear stress levels ranging from 0.2 to 6.0 N/m2 with times of exposure to the shear stress ranging from 2 to 24 h. The influence of the shear field was slight at low shear stress (0.26 N/m2). Higher stress levels (0.65 N/m2 and higher) had significant effects on cell morphology, and on the post‐shear release of urokinase enzyme. Still higher stress levels (2.6 N/m2 and higher) caused marked reduction in cell viability. These results may be of interest in addressing practical problems in developing commercial biosynthesis reactors.
Enzymatic hydrolysis of cellulose in aqueous two‐phase systems. I. partition of cellulases from Trichoderma reesei
Authors: Tjerneld Folke , Persson Ingrid , Albertsson Per‐Åke , Hahn‐Hägerdal Bärbel
Published: December 2004

The partitioning of endo‐β‐glucanase, exo‐β‐glucanase, and β‐glucosidase from Trichoderma reesei QM 9414 in aqueous two‐phase systems has been studied with the object of designing a phase system for continuous bioconversion of cellulose. The partitioning of the enzymes in two‐phase systems composed of various water soluble polymeric compounds were studied. Systems based on dextran and polyethylene glycol (PEG) were optimal for one‐sidedly partitioning the enzymes to the bottom phase. The influence of polymer molecular weights, polymer concentration, ionic composition of the medium, pH, temperature, and adsorption of the enzymes to cellulose on the enzyme partition coefficients (K) were studied. By combining the effects of polymer molecular weight and adsorption to cellulose, K values could be reduced for endo‐β‐glucanase to 0.02 and for β‐glucosidase to 0.005 at 20°C in a phase system of Dextran 40–PEG 40000 in the presence of excess cellulose, At 50°C, K values were increased by a factor of two. In a phase system based on inexpensive crude dextran and PEG, the partition coefficient for endo‐β‐glucanase was 0.16 and for β‐glucosidase was 0.14 at 20°C with excess cellulose present.