bluuebunny/crossref_metadata_2025 huggingface dataset:
Utilization of cellulosic materials through enzymatic hydrolysis. I. Fermentation of hydrolysate to ethanol and single‐cell protein
Authors: Cysewski Gerald R. , Wilke Charles R.
Published: December 2004

Ethanol fermentation studies were conducted with Saccharomyces cerevisiae ATCC #4126, to determine the optimal conditions of oxygen tension and feed sugar concentration. In long‐term continuous culture maximum ethanol production was found to occur at 0.07 mmHg oxygen tension and 10% glucose feed concentration. Preliminary process design and cost studies are developed for industrial scale fermentations to produce ethanol and torula yeast from sugars obtained by enzymatic hydrolysis of newsprint.
The immobilization of microbial cells, subcellular organelles, and enzymes in calcium alginate gels
Authors: Kierstan M. , Bucke C.
Published: December 2004

Saccharomyces cerevisiae cells, Kluyveromyces marxianus cells, inulase, glucose oxidase, chloroplasts, and mitochondria were immobilized in calcium alginate gels.

Ethanol production from glucose solutions by an immobilized preparation of S. cerevisiae was demonstrated over a total of twenty‐three days, and the half‐life of such a preparation was shown to be about ten days.

Immobilized K. marxianus, inulase, and glucose oxidase preparations were used to demonstrate the porosity and retraining properties of calcium alginate gels.

Calcium alginate–immobilized chloroplasts were shown to perform the Hill reaction.

Some experiments with immobilized mitochondria are reported.
Phenotypic modifications in amino acid profiles of cell residues ofcandida utilisandenterobacter aerogenes
Authors: Alroy Yair , Tannenbaum Steven R.
Published: December 2004

Glucose‐limited chemostat cultures ofCandida utiliswere cultivated at various pH levels (3.0–7.5), temperatures (15–37.5°C), dilution rates (0.06–0.42 hr−1), and with one of two nitrogen sources (NHor NO).Enterobacter aerogeneswas also cultivated in the chemostat under nitrogen and phosphorus limitations. The amino acid profile of total cell protein is expressed as the content of each amino acid relative to the sum of all amino acids recovered after acid hydrolysis. Cell residues obtained after hot trichloroacetic acid extraction display small variations in amino acid profile. Some of these variations correlate with the growth rate at satisfactory levels of statistical significance. InC. utilis, the correlations cover increased levels of lysine, arginine, and leucine and decreased levels of serine and glutamic acid with increased “reduced dilution rate” (D/Dc). InE. aerogenes, increased levels of lysine and arginine and a decreased level of glutamic acid correlate with increased dilution rate. The directions of most of these correlations and the extents of those pertaining to lysine and arginine are consistent with the change predicted to occur simultaneously in the relative level of the ribosomal protein group.
Media suitable for industrial production of Entomophthora virulenta zygospores
Authors: Latgé J.‐P. , Soper R. S. , Madore C. D.
Published: December 2004

Entomophthora virulenta has been grown using inexpensive, commercial grade nutrient sources in order to produce a resting spore formulation available to agriculture. Solid media and liquid media in shake flasks and fermentors were examined. The best carbon sources for sporulation were dextrose and corn syrup, while the best nitrogen sources were yeast extract, soybean, and cottonseed flours. The optimal nutrient concentration (12%) produced 3 × 106spores/ml with a 70% germination rate within five days.
Properties and biodegradation of a bioemulsifier from Corynebacterium hydrocarboclastus
Authors: Zajic J. E. , Guignard Hélène , Gerson D. F.
Published: December 2004

An extracellular polymer was produced by continuous fermentation of Corynebacterium hydrocarboclastus on kerosene in a 24 liter reactor. This polymer was composed of protein, lipid, and carbohydrates. The polymer possesed surface active properties, and had two critical micelle concentrations. Its effectiveness was quite comparable to the effectiveness of synthetic surface active agents such as Tween 80 and Span 20; however, its efficiency was much lower. The polymer also had emulsifying properties. Maximum emulsification was obtained at pH 6. The emulsifying properties were unaffected by high salt concentration [up to 5% (w/v) in Na+], and tolerated a water hardness up to 5,000 ppm. A 2 hr treatment of the polymer at temperatures higher than 65°C resulted in a loss of its emulsifying properties. Two microorganisms, named SLYS and Y, isolated from soil, were able to grow on the polymer as sole carbon and energy source, thus proving its biodegradability. SLYS was tentatively identified as Flavobacterium breve and Y as Flavobacterium devorans.
Differential speed two roll mill pretreatment of cellulosic materials for enzymatic hydrolysis
Authors: Tassinari Thomas , Macy Charles
Published: December 2004

Differential speed two roll milling is an effective pretreatment for increasing the susceptibility of cellulose to enzymatic hydrolysis. Using mills with three, six, and ten in. diam rolls and processing times of 10 min or less results in the following percent increases in susceptibility over untreated controls: cotton, 1100; maple chips, 1600; white pine chips, 600; newspaper, 125. In comparison, ball milling of newspaper for 24 hr gives only a 62% increase. A further advantage of the roll mill is the increased wet density of the product permitting higher slurry concentrations during hydrolysis. Important parameters of mill effectiveness are roll clearance and processing time.
Kinetics of nitrification and denitrification reactions
Authors: Shah Dhananjai B. , Coulman George A.
Published: December 2004

Nitrification and denitrification are important microbiological reactions of nitrogen. In this work, the kinetics of these reactions have been investigated based on a Monod‐type expression involving two growth limiting substrates: ammonium nitrogen and dissolved oxygen for nitrification and nitrate nitrogen and dissolved organic carbon for denitrification. The kinetic constants and yield coefficients were evaluated for both these reactions. Past experimental work was used to determine the constants for the nitrification reaction. For the denitrification reaction, experiments were performed in a stirred tank reactor under conditions such that only one substrate was growth limiting. Steady‐state values of the substrate concentrations in the reactor were determined at various dilution rates. These data were analyzed to obtain the kinetic and stoichiometric constants. From these constants it was concluded that in the range of nitrate nitrogen concentrations encountered in waste water, the denitrification reaction can be considered a first‐order reaction. It was also found that three times as much organic carbon is required as nitrate nitrogen for complete nitrogen removal.
Single cell protein from various chemically pretreated wood substrates using Chaetomium cellulolyticum
Authors: Moo‐Young M. , Chahal D. S. , Vlach D.
Published: December 2004

The growth behavior of Chaetomium cellulolyticum, a new cellulolytic fungus, has been examined in slurry fermentation systems using various chemically pretreated sawdusts from hardwoods as substrates. Both acid‐ and alkali‐pretreatment methods were used and the fermentation media included the spent pretreatment liquor in an attempt to concurrently maximize substrate utilization and minimize the biological oxygen demand (BOD) level in the process effluent. Diauxic growth patterns were found in the three cases studied, suggesting an initial utilization of soluble hemicellulose sugars followed by utilization of the insoluble cellulose. This behavior patterns was supported by separate growth experiments using the major sugars of hemicellulose as carbon sources. The organism was found to be a good convertor of both cellulose and hemicelluloses into single cell protein (SCP). In terms of rate and extent of protein production in the insoluble biomass product, acid pretreatment appears to be better than alkali pretreatment if the product is intended as ruminant feed.
Citric acid production from glucose. I. Growth and excretion kinetics in a stirred fermentor
Authors: Briffaud Joseph , Engasser Jeanmarc
Published: December 2004

The growth and citric acid production kinetics of Saccharomycopsis lipolytica on glucose are investigated in an aerated stirred fermentor. Cellular growth first proceeds exponentially until exhaustion of ammonia in the fermentation medium. Cells then continue to grow at a reduced rate with a concomitant decrease in intracellular nitrogen content. Citric and isocitric acid production starts at the end of the growth phase. During about 80 hr excretion proceeds at a constant rate of 0.7 g/liter/hr for citric acid and 0.1 g/liter/hr for isocitric acid. The final citric and isocitric acid concentrations are 95 and 10g/liter, respectively. During acid excretion cellular respiration accounts for 60 and 35% of consumed oxygen and glucose. Both acid and CO2 production rates follow a Michaelis–Menten‐type dependence on oxygen concentration with Michaelis–Menten constants of 0.9 and 0.15 mg/liter for acid and CO2 productions, respectively.
Citric acid production from glucose. II. Growth and excretion kinetics in a trickleflow fermentor
Authors: Briffaud Joseph , Engasser Jeanmarc
Published: December 2004

The growth and citric acid production kinetics of Saccharomycopsis lipolytica on glucose is investigated in a trickle‐flow fermentor. Liquid hold‐up and oxygen‐transfer coefficient in the reactor column filled with cylindrical wood chips have been determined and found in agreement with chemical engineering correlations. Citric acid production starts at the end of the growth phase and proceeds at a constant specific rate of 0.025 hr−1for about 80 hr. The fermentor can then be regenerated by addition of ammonia, which induces new growth and excretion phases. Comparing the metabolic behavior of free and immobilized cells, two main kinetic differences are observed. First, the growth phase is linear with the bound cells instead of exponential in the stirred fermentor. Second, in the trickle‐bed fermentor acid productivity and oxygen acid yield are reduced by 30%. Oxygen diffusional limitations, mainly in the biomass film, and alterations in bound cell metabolism are shown to be responsible of the kinetic modifications. Simple modelizations of oxygen diffusion effects are also presented to support the interpretation of the experimental data.
Production of ethanol from raw cassava starch by a nonconventional fermentation method
Authors: Ueda Seinosuke , Zenin Celia T. , Monteiro Domingos A. , Park Yong K.
Published: December 2004

Raw cassava root starch was transformed into ethanol in a one‐step process of fermentation, in which are combined the conventional processes of liquefaction, saccharification, and fermentation to alcohol. Aspergillus awamori NRRL 3112 and Aspergillus niger were cultivated on wheat bran and used as Koji enzymes. Commercial A. niger amyloglucosidase was also used in this experiment. A raw cassava root homogenate–enzymes–yeast mixture fermented optimally at pH 3.5 and 30°C, for five days and produced ethanol. Alcohol yields from raw cassava roots were between 82.3 and 99.6%. Fungal Koji enzymes effectively decreased the viscosity of cassava root fermentation mashes during incubation. Commercial A. niger amyloglucosidase decreased the viscosity slightly. Reduction of viscosity of fermentation mashes was 40, 84, and 93% by commercial amyloglucosidase, A. awamori, and A. niger enzymes, respectively. The reduction of viscosity of fermentation mashes is probably due to the hydrolysis of pentosans by Koji enzymes.
Organic acid production from CO2/H2 and CO/H2 by mixed‐culture anaerobes
Authors: Levy P. F. , Barnard G. W. , Garcia‐Martinez D. V. , Sanderson J. E. , Wise D. L.
Published: December 2004

The gases CO, CO2, and H2 were used as substrates in anaerobic fermentations producing organic acids. Various mixed bacterial sources were used, including sewage sludge digester effluent, rabbit feces, and soil. Nonsterile microorganism selection was carried out using CO2/H2 and CO/H2 as the primary carbon and energy sources. Cultures were grown in specially designed, high‐pressure (to 70 psig) flasks. Methanogenic bacteria were eliminated from the cultures. Liquid products of the fermentations were acetic through caproic acids, with the even‐numbered acids predominating. Carbon balances showed conclusively that acetic acid was formed from carbon contained in the CO or CO2 feed gas. Measurements made included rates of acid product formation, cell density, and degree of gas utilization. Limited characterization of the microorganisms was also performed. Production of organic acids by mixed culture inocula from CO2/H2 or CO/H2 had not been reported previously. Application of this work is to the production of organic chemicals from synthesis gas (SNG), produced by the gasification of fossil fuels (peat, lignite, and various ranks of coals), biomass (agricultural and forest residues, and various biomass crops grown expressly for energy recovery), and municipal solid waste.
Effect of compression milling on cellulose structure and on enzymatic hydrolysis kinetics
Authors: Ryu Dewey D. Y. , Lee Sun Bok , Tassinari T. , Macy C.
Published: December 2004

The changes in the cellulose structure by compression milling were studied and expressed in terms of crystallinity, accessibility, specific surface area, and degree of polymerization. The kinetic parameters, maximum reaction rate, and Michaelis constant were determined experimentally. Based on the experimental results a two‐phase model, which is based on the degradation of cellulose by simultaneous actions of the cellulase complex on the crystalline and amorphous phases, is proposed. The relationships between cellulose accessibility and the kinetic parameters were compared with those predicted by the model. A good agreement was found, although the two‐phase hypothesis is a simplification of the true state of order in cellulose.
Ethanol production by immobilized Saccharomyces cerevisiae, Saccharomyces uvarum, and Zymomonas mobilis
Authors: McGhee J. E. , Julian G. St. , Detroy R. W. , Bothast R. J.
Published: December 2004

Saccharomyces cerevisiae NRRL Y‐2034, S, uvarum NRRL Y‐1347, and Zymomonas mobilis NRRL B‐806 each were separately immobilized in a Ca‐alginate matrix and incubated in the presence of a free‐flowing and continuous 1, 3, 5, 10, or 20% (w/w) glucose solution. In general, the yeast cells, converted 100percnt; of the 1, 3, and 5% glucose to alcohol within 48 h and maintained such a conversion rate for at least two weeks. The bacterium converted ca. 90% (w/w) of the 1, 3, and 5% glucose to alcohol continuously for one week. However, both the yeast and bacterium were inhibited in the highest glucose (20% w/w) solution. All of the immobilized cultures produced some alcohol for at least 14 days. Immobilized S. cerevisiae was the best alcohol producer of all of the glucose concentrations; the yeast yielded 4.7 g ethanol/100 g solution within 72 h in the 10% glucose solution. After 7–8 days in the 10% solution, S. cerevisiae produced ethanol at 100% of theoretical yield (5.0 g ethanol/100 g solution), with a gradual decrease in alcohol production by 14 days. Immobillized S. uvarum produced a maximum of 4.0 g ethanol/100 g solution within 2 days and then declined to ca. 1.0 g ethanol/100 g solution after 7 days continuous fermentation in the 10% glucose solution. Zymomonas mobilis reached its maximum ethanol production at 4 days (4.7 g/100 g solution), and then diminished similarly to S. uvarum. The development of a multiple disk shaft eliminated the problem both of uneven distribution of alginate‐encapsulated cells and of glucose channeling within the continuous‐flow fermentor column. This invention improved alcohol production about threefold for the yeast cells.
Development of a direct digital‐controlled fermentor using a microminicomputer hierarchical system
Authors: Rolf Michael J. , Hennigan Paul J. , Mohler Robert D. , Weigand William A. , Lim Henry C.
Published: December 2004

A computerized fermentation system was developed for use in a research environment. Major goals in the design and construction of the system were flexibility and versatility. Direct digital control is employed for all low‐level and high‐level control loops. A microminicomputer hierarchical configuration is used to implement this control structure. The microcomputer is also utilized to simplify the interface with the fermentor, both at the hardware and minicomputer software levels. This computerized fermentation system provides accurate data acquisition, excellent control, and flexibility in the fermentation operation.
Continuous ethanol production from Jerusalem artichoke tubers. II. Use of immobilized cells of Kluyveromyces marxianus
Authors: Margaritis Argyrios , Bajpai Pratima
Published: December 2004

Kluyveromyces marxianus UCD (FST) 55–82 cells were immobilized in Na alginate beads and used in a packed‐bed bioreactor system for the continuous production of ethanol from the extract of Jerusalem artichoke tubers. Volumetric ethanol productivities of 104 and 80 g ethanol/ L/h were obtained at 80 and 92% sugar utilization, respectively. The maximum volumetric ethanol productivity of the immobilized cell bioreactor system was found to be 15 times higher than that of an ordinary‐stirred‐tank (CST) bioreactor using cells of K. marxianus. The immobilized cell bioreactor system was operated continuously at a constant dilution rate of 0.66 h−1 for 12 days resulting in only an 8% loss of the original immobilized cell activity, which corresponds to an estimated half‐life of ca. 72 days. The maximum specific ethanol productivity and maximum specific sugar uptake rate of the immobilized cells were found to be 0.55 g ethanol/g/biomass/h and 1.21 g sugars/g biomass/h, respectively.
Hydrogen production by a green alga, Chlamydomonas reinhardtii, in an alternating light/dark cycle
Authors: Miura Yoshiharu , Yagi Kiyohito , Shoga Mitsuru , Miyamoto Kazushisa
Published: December 2004

The evolution of H2 in the dark period of a light/dark cycle by a green alga, Chlamydomonas reinhardtii, was studied with the aim of developing a two/stage biophotolysis system. The algal cells accumulated starch during the growth period in light. When these cells were incubated microaerobically in the dark, hydrogenase activity was induced was induced without an appreciable lag time and therapy H2 evolution was observed for several hours to more than 10 h, depending upon the amount of added O2. The cells harvested in the midlogarithmic growth phase were the most efficient in production of H2 in the dark. H2 evolution was highly dependent on temperature, but rather incentive to pH values from 5–9. Based on these observations, altering production of O2 and H2 was demonstrated repeatedly in a light/dark cycle.
Immobilization of mold and bacterial amylases on silica carriers
Authors: Kvesitadze G. I. , Dvali M. Sh.
Published: December 2004

The immobilization of α‐amylase and glucoamylase was investigated by several coupling methods on silica carriers, different types of Silokhroms, and silica gels. The most active immobilized mold and bacterial α‐amylases and mold glucoamylase were obtained with titanium salts. These activities were twice the value of that obtained by glutaraldehyde or azo coupling. The half‐lives of A. oryzae α‐amylase, B. subtilis α‐amylase, and A. niger glucoamylase, immobilized to silica carriers at 45°C and under continuous operation at a high concentration of substrate, were 14, 35, and 65 days, respectively.
Exploitation of plant cells for the production of natural compounds
Authors: Deus B. , Zenk M. H.
Published: December 2004

A four‐step strategy is presented which allows the establishment of plant cell cultures producing high yields of secondary plant products. The application of suitable methods (radioimmunoassay, fluorescence screening) for the selection of overproducing differentiated plants and cell colonies is stressed. By precursor feeding and hormone application, plant cell cultures can greatly be influenced in their production behavior. A highly sensitive, selective regulatory mechanism for the uptake and storage of alkaloids in Catharanthus vacuoles is demonstrated. Overproducing variant cell strains are so far the most promising tool for the future biotechnological application of the plant cell culture method.
Methane from cattle waste: Effects of temperature, hydraulic retention time, and influent substrate concentration on kinetic parameter (k)
Authors: Hashimoto Andrew G.
Published: December 2004

The effects of temperature (35 and 55°C), influent volatile solids (VS) concentration (S0 = 43, 64, 82, 100, and 128 kg VS/m3) and hydraulic retention time (HRT = 4, 5, 8, 10, 15, and 25 days) on methane (CH4) production from cattle waste were evaluated using 3‐dm3 laboratoryscale fermentors. The highest CH4 production rate achieved was 6.11 m3 CH4 m−3 fermentor day−1 at 55°C, four days HRT, and S0 = 100 kg VS/m3. Batch fermentations showed an ultimate CH4 yield (B0) of 0.42 m3 CH4/kg VS fed. The maximum loading rates for unstressed fermentation were 7 kg VS m−3 day−1 at 35°C and 20 kg VS m−3 day−1 at 55°C. The kinetic parameter (K, an increasing K indicates inhibition of fermentation) increased exponentially as S0 increased, and was described by: K = 0.8 + 0.0016 e. Temperature had no significant effect on K for S0 between 40 and 100 kg VS/m3. The above equation predicted published K values for cattle waste within a mean standard error of 7%.
The properties of immobilized caldolysin, a thermostable protease from an extreme thermophile
Authors: Cowan Donald A. , Daniel Roy M.
Published: December 2004

Caldolysin, the extracellular thermostable metal‐chelator‐sensitive lytic protease from Thermus T‐351 was immobilized to Sepharose 4B, CM‐cellulose, and controlled pore glass (CPG). Although protein binding efficiencies were high (96, 88, and 95%), some loss of enzyme activity occurred on immobilization (26, 69, and 89%). The pH optimum of both CM‐cellulose and CPG‐immobilized Caldolysin was decreased by about one pH unit. The Km for Sepharose‐Caldolysin was unchanged with respect to the free protease, while those for CM‐cellulose‐Caldolysin and CPG‐Caldolysin were lower by approximately one order of magnitude. Immobilization to both Sepharose and CM‐cellulose increased the thermostability of Caldolysin at high temperatures, while CPG‐Caldolysin was less thermostable than the free protease.
Bioconversion of waste cellulose by using an attrition bioreactor
Authors: Ryu S. K. , Lee J. M.
Published: December 2004

A new type of reactor, an attrition bioreactor, was tested to achieve a higher rate and extent of enzymatic saccharification of cellulose than is possible with conventional methods. The reactor consisted of a jacketted stainless‐steel vessel with shaft, stirrer, and milling media, which combined the effect of the mechanical action of wet milling with cellulose hydrolysis. The substrates tested were newsprint and white‐pine heartwood. The performance of the reactor was excellent. The extent and rate of enzymatic hydrolysis could be markedly improved over other methods. The power consumption of the attrition bioreactor was also measured. The cellulase enzyme deactivation during attrition milling was not significant.
Reduction of acetoin to 2,3‐butanediol in Klebsiella pneumoniae: A new model
Authors: Voloch M. , Ladisch M. R. , Rodwell V. W. , Tsao G. T.
Published: December 2004

Fermentation of xylose by Klebsiella pneumoniae (ATCC 8724, formerly known as Aerobacter aerogenes) carried out in our laboratory yields 2,3‐butanediol as the major product. Experimental data obtained in this work cannot be explained by the model presently in the literature for the formation of 2,3‐butanediol isomers from acetoin isomers. A new model is proposed with the existence of two acetoin reductases and an acetoin racemase. The two reductases were separated and their stereospecificity determined. Extension of the model of other microorganisms is discussed.
Conversion of straw–manure mixtures to methane at mesophilic and thermophilic temperatures
Authors: Hashimoto Andrew G.
Published: December 2004

The effects of temperature (35 and 55°C) and straw–manure mixtures (90, 75, 50, and 0% straw) on methane (CH4) production were studied using laboratory‐scale fermentors. Batch fermentations showed that the ultimate CH4 yield (B0) of straw–manure mixtures was directly proportional to the relative proportion and B0 of the individual components. Also, hammer or ball milling did not increase the B0 of straw. Kinetic analysis showed that fermentation stress occurred when the straw content of straw–manure mixtures was higher than 40% at 35°C, or higher than 75% at 55°C. This fermentation stress was observed to occur when the free ammonia concentration was below 10 g/m3.
Immobilization of fumarase by entrapment of rat liver mitochondria in polyacrylamide gel using gamma rays
Authors: Godbole S. S. , Kaul Rajni , D'Souza S. F. , Nadkarni G. B.
Published: December 2004

A stable immobilized preparation of fumarase (EC 4.2.1.2) was obtained by entrapment of rat liver mitochondria in acrylamide polymerized by using gamma irradiation (100 kR). The enhanced stability and the efficiency of the entrapped enzyme have shown potential for repeated use for the production of L‐malic acid from fumaric acid. The possible formation of succinic acid in the system could be controlled by incorporating malonate along with detergents such as sodium deoxycholate or sodium dodecylsulfate in the reactor system.
Preparation and performance of immobilized yeast cells in columns containing no inert carrier
Authors: Hsiao Humg‐Yu , Chiang Lin‐Chang , Yang Che‐Ming , Chen Li‐Fu , Tsao George T.
Published: December 2004

Schizosaccharomyces pombe was cultivated in a medium of glucose (10 g/L) malt extract (3 g/L), yeast extract (3 g/L), and bactopeptone (5 g/L) to form flocs. More than 95% of the cell population were flocculated. Variation in glucose concentration (from 10 to 100 g/L) did not affect flocculation. Yeast extract helped induce flocculation. Application of the immobilized yeast for the continuous production of ethanol was tested in a column reactor. Soft yeast flocs (50–200 mesh) underwent morphological changes to heavy particles (0.1–0.3 cm diameter) after continuously being fed with fresh substrates in the column. Productivity as high as 87 g EtOH L−1 h−1 was obtained when a 150 g/L glucose medium was fed. The performance of this yeast reactor was stable over a two‐month period. The ethanol yield was 97% of the theoretical maximum based upon glucose consumed.
Kinetics and mechanism of acyl transfer by penicillin acylases
Authors: Konecny Jan , Schneider André , Sieber Meinrad
Published: December 2004

The hypothesis that at least some penicillin acylases react via an acyl–enzyme intermediate was tested by kinetic investigations involving the methyl ester of cyanoacetic acid as the acyl donor, deacetyl‐7‐aminocephalosporanic acid as the acyl receptor, and penicillin acylase (E.C.3.5.1.11) from B. megaterium ATCC 14945 as the catalyst. The results obtained at low concentrations of the acyl receptor are in accord with the derived rate equations. Deviations observed at higher concentrations of the acyl receptor are discussed together with some practical implications of the mechanism.
An immobilized two‐enzyme system (fungal α‐amylase/glucoamylase) and its use in the continuous production of high conversion maltose‐containing corn syrups
Authors: Hausser Alexander G. , Goldberg Bruce S. , Mertens John L.
Published: December 2004

Fungal α‐amylase (E.C. 3.2.1.1) and glucoamylase (E.C. 3.2.1.3) were chemically attached to separate reactor modules made from Microporous Plastic Sheet (MPS). Immobilization of enzymes and subsequent chemical reactions were accomplished by pumping reactants through the sheet, i.e., perpendicular to the surface. The expressed activity of the reactor modules was ca. 800 U/g for both fungal α‐amylase and glucoamylase. The kinetics and short‐term effects of pH and temperature on the expressed activity of the immobilized enzymes were investigated. Using commercially available DE‐42 corn syrup at 50% dissolved solids, half‐lives of 2000 and 5000 h were achieved for glucoamylase and fungal α‐amylase, respectively. The reactors were operated at 50°C and at pH 4.3 for glucoamylase and 5.5 for fungal α‐amylase. A typical DE‐62 corn syrup product was continuously produced in a two‐stage reactor system by pumping the feedstock through the glycoamylase reactor and then through the fungal α‐amylase reactor. Saccharide distributions at each stage were controllable to ±0.2%.
The effects of limiting nutrients, dilution rate, culture pH, and temperature on the yield constant and anthocyanin accumulation of carrot cells grown in semicontinuous chemostat cultures
Authors: Dougall D. K. , LaBrake S. , Whitten G. H.
Published: December 2004

With carrot cells grown in semicontinuous culture with phosphate as limiting nutrient. Dougall and Weyrauch (1980) found that the steady‐state culture density was different at different dilution rates. They suggested that the yield constant for biomass was different at different dilution rates. Here the yield constant for biomass for PO, NH, Mg2+, and glucose‐limited semicontinuous cultures has been measured directly at two dilution rates. The yield constants for PO, NH4+, and Mg2+ but not for glucose are different at the two dilution rates. The effects of pH and temperature on the biomass yield constant was measured to extend the number of system parameters examined. Biomass yield constant was changed little with change from 25 to 28°C or from pH 4.2 to pH 5.5. The steady‐state levels of anthocyanin were also measured. The responses of anthocyanin levels to the system parameters are different to the biomass responses. The data suggest that at different values of each of the system parameters, the composition and metabolic activities of the cells at steady state in semicontinuous cultures are different.
Production of microbial biomass on the products of mild acid hydrolysis of piggery slurry
Authors: Davey G. , Bruce J.
Published: December 2004

The effect of mild sulfuric acid (H2SO4) hydrolysis on the cellulosic components of piggery slurry was investigated. Combinations of acid concentrations between 1 and 10% (w/v) and temperatures of 89, 90, and 100°C were studied with the aim of maximizing the release of soluble carbohydrates from the cellulosic constituents of piggery slurry. The highest yield of soluble monosaccharides was obtained by hydrolysis with 5% sulfuric acid at 90°C for 3 h, which produced 0.53 g of monosaccharide for every gram of cellulosic material available in raw piggery slurry. When the fungus Sporotrichum pulverulentum was cultivated on a medium prepared from this hydrolysate, a yield of 19.8 g of microbial biomass was obtained for each liter of piggery slurry hydrolyzed.
Kinetics of aflatoxin biosynthesis by Aspergillus parasiticus in the presence of Nα‐palmitoyl‐L‐lysyl‐L‐lysine‐ethyl ester dihydrochloride or dichlorvos
Authors: Yousef Ahmed E. , Marth Elmer H.
Published: December 2004

Nα‐Palmitoyl‐L‐lysyl‐L‐lysine‐ethyl ester dihydrochloride (PLL) has antimicrobial properties and may be useful as a food preservative. This study was conducted to see if PLL can inhibit growth and synthesis of aflatoxin by Aspergillus parasiticus. Growth of mold and accumulation of aflatoxins were monitored for up to 15 days. To compare these data with those of a known inhibitor of aflatoxin synthesis, dichlorvos was added to media, and mold growth and aflatoxin accumulation were monitored. The kinetic model of Brown and Vass that correlates growth and formation of secondary metabolites was applied to results of this study, and values for maturation time (tm) and aflatoxin accumulation rate constant (α) were calculated. Values of tm decreased when cultures contained PLL, whereas presence of dichlorvos resulted in a considerable increase. The lag phase of mold growth increased in the presence of PLL. The values of α increased with an increasing amount (up to 300 ppm) of PLL in media. Higher concentrations of PLL decreased the value of α. All levels of dichlorvos tested decreased the value of α. The aflatoxin accumulation rate constant (α) as a function of concentration of additive (C) followed the general equation:

where αm, Ka, and Ki are constants.
New concepts for rapid yeast settling. I. Flocculation with an inert powder
Authors: Weeks M. G. , Munro P. A. , Spedding P. L.
Published: December 2004

A novel technique for settling microorganisms has been described. The technique involves adding a dense, inert powder to a suspension of microorganisms under conditions where flocculation of the microorganism with the inert poweder occurs. The flocs formed are small and relatively dense and settle rapidly. Suspensions of Saccharomyces cerevisiae yeast have been flocculated with several different inert seed materials achieving rapid settling and separations of up to 99.9%. Nickel powder was used as a seed material for most experiments described here, and iron sand showed promise as a cheaper seed for large‐scale use. The degree of flocculation and cell separation obtained depended largely on the seed concentration and the components in solution. Temperature and pH had little effect. When the method was initially applied to a practical fermentation, flocculation was poor because of inhibiting compounds in the fermentation medium, but modification of the technique produced good flocculation in the medium.
New concepts for rapid yeast settling. II. pH switching with an inert powder
Authors: Weeks M. G. , Munro P. A. , Spedding P. L.
Published: December 2004

A new technique is outlined for the rapid settling of yeast cells in fermentation media. The technique involved the addition of dense, inert particles (nickel powder) to a yeast suspension (Saccharomyces cerevisiae) at pH 4.5 and a rapid change of pH to 8.0–9.0. When the pH was changed large flocs formed immediately and settled rapidly, leaving a clear supernatant. On returning the pH to 4.5 the flocs were destroyed. This technique gave larger flocs and higher settling rates than the constant pH method, and much lower nickel/yeast ratios were required. Good flocculation also occurred in a fermentation medium. The technique was used to recycle yeast cells to a semicontinuous ethanol fermentation. Application of the technique to this and similar systems is discussed. The factors affecting yeast/inert powder flocculation are also discussed and a model is proposed to explain the observed experimental behavior for flocculation with a rapid change in pH.
The use of chaotropic salts for separation of ribonucleic acids and proteins from yeast nucleoproteins
Authors: Damodaran Srinivasan , Kinsella John E.
Published: December 2004

The effect of chaotropic salts on the dissociation of ribonucleic acid from yeast nucleoprotein complex was studied. The effectiveness of various salts on the dissociation of ribonucleic acid followed the chaotropic series; i.e., Cl3CCOONa = NaClO4 > NaBr > NaCl. Treatment of the nucleoprotein complex with 0.5M Cl3CCOONa or NaClO4 resulted in RNA removal of about 80%, whereas NaCl and NaBr removed only about 10 and 25%, respectively. Based on the results presented, a simple and novel method for industrial‐scale preparation of single‐cell proteins with low levels of nucleic acid is proposed.
Computer control of the penicillin fermentation using the filtration probe in conjunction with a structured process model
Authors: Nestaas Eirik , Wang Daniel I. C.
Published: December 2004

A structured model for the penicillin fermentation is presented. This model includes three different cell types: (1) hyphae tips, (2) penicillin‐producing cells, and (3) degenerated, metabolically inactive cells. Cell degeneration has been described previously as a gradual loss of cytoplasmic material by endogenous metabolism. The rate at which such loss of cytoplasm (and activity) proceeds can be expressed as a linear function of the specific growth rate. At growth rates above some minimum value (0.0115 h−1) cell degeneration can be prevented. This model served as the control basis during open‐loop as well as closed‐loop computer control of the fermentation. Closed‐loop control was achieved through feedback information of biomass concentration using a filtration probe and was required when complex nutrients contributed significantly to the overall biomass production.
Some practical aspects of computer applications in a fermentor hall
Authors: Meiners M. , Rapmundt W.
Published: December 2004

The use of computers in a fermentation pilot plant is described from a practical point of view. The aim is not the application of a computer to a single special process but a general application of computers to prepare and present data for the following analysis of fermentation processes. The hardware is normally bought from computer manufacturers, but some additional installations are useful. Application software has to be developed by the biotechnologist, therefore the software structure is the most important part of the computer application. Data storage is divided into three parts: short‐time memory, long‐time storage, and a medium memory mainly to be used in process analyses and process control. Four types of programs are used: main schedule tasks, low‐priority on‐line tasks, sense‐switch routine, and different off‐line programs. A table of all programs is presented, the main schedule task is described in detail to demonstrate the software structure.
Determination of substrate concentrations by a computerized enzyme electrode
Authors: Kernevez J. P. , Konate L. , Romette J. L.
Published: December 2004

A numerical treatment of the signal produced by an electrode onto which an artificial enzyme membrane is mounted can give the concentration of the substrate (glucose, saccharose, lactose, amino acids, etc.) in solution. In the example of a glucose analyzer, in which glucose oxidase catalyzes the oxidation of glucose, the computer receives pO2 level data from the electrode and calculates the glucose concentration. The transient electrode signal, measured as the enzyme membrane is exposed to a solution of glucose, is least‐square approximated by a third‐degree polynomial whose slope at inflection point is characteristic of the external glucose concentration. A calibration procedure provides a cubic spline approximation of glucose concentration as a function of slope, thus enabling automatic measurement of samples. The computer performs the calculations, and actuates valves for air rinsing, introduction of the sample, and water rinsing.
The deposition of bacterial cells from laminar flows onto solid surfaces
Authors: Powell Martin S. , Slater Nigel K. H.
Published: December 2004

In a previous article, the authors proposed a simple model for the rate of removal of bacterial cells from solid surfaces by fluid shear. This Model has been extended to include the deposition of cells from a flowing suspension. The theory is compared to experimentally obtained data for the deposition of Bacillus cereus cells onto the surface of glass capillaries. The effect of a hydrophobic surface, siliconized glass, and the addition of an antifoam agent to the suspension is also investigated.
Optimization of batch fermentation processes by graphical method
Authors: Staniškis J. , Levišauskas D.
Published: December 2004

A graphical method is proposed for batch fermentation process optimization. Its objective function is the maximum output of the product when the time of process is fixed or free. The technique of optimization is based on Bellman's dynamic programming concepts and the assumption that the process can be described by mathematical models of generalized structure. An example of the proposed technique's application is presented.
Arachidonic acid production by the red algaPorphyridium cruentum
Authors: Ahern Tim J. , Katoh Shigeo , Sada Eizo
Published: December 2004

The single‐celled alga,Porphyridium cruentum, was assessed by means of chromatographic separation and mass spectral analysis of its fatty acids to be a potentially competetive source of arachidonic (5,8,11,14‐eicosatetraenoic) acid. Models for both cell growth and production of the prostaglandin precursor at various temperatures and light intensities are presented. Increasing the light intensity within the range 1700–8000 lux increases the cell growth rate without affecting the arachidonic acid yield per cell; increasing the cultivation temperature from 18°C to ca. 32°C lowers the yield of arachidonic acid per cell but increases the rate of its production per unit volume and time. The increase of the weight ratio of arachidonic:palmitic acids at low temperatures is interpreted as a means of controlling the microviscosities of cellular membranes. In addition, the arachidonic acid content of cells decreases with the culture's age, despite increases in unit cell dry weight. The maximum rate of 0.46 mg arachidonic acid L−1h−1was calculated by means of the model to occur at ca. 32°C and 8000 lux in liquid cultures of 12 × 109cells/L. Estimates of the cost of producing arachidonic acid by means of this alga range from $0.15/g to $1.00/g of arachidonic acid. Cells grown at 18°C in the presence of 0.3% linoleic acid swelled and produced gorlic (13‐cyclopent‐2‐enyltridec‐6‐enoic) acid and another compound not normally observed. An estimated threefold increase of arachidonic acid content also occurred, but no significant lipogenesis was induced at 23°C in the presence of 1% kerosene or 0.3% palmitic, stearic, oleic, or linoleic acids.
The effect of carbon dioxide on the production of an extracellular nuclease of Staphylococcus aureus
Authors: Quirk A. V. , Plank R. W. H.
Published: December 2004

The production of the extracellular nuclease secreted by Staphylococcus aureus (Foggi strain) was studied in a fermentor in an attempt to improve yield and allow large‐scale production of the enzyme. In shake flask cultures, 600 units/mL of the enzyme were produced routinely. However, only 450 units/mL of the enzyme at best were obtained in a small‐scale fermentor (3 L). The supplementation of the air supply to the fermentor with carbon dioxide [20% (v/v)] increased levels of enzyme in the culture medium to 770 units/mL. Subsequently, this result was reproduced in larger fermentors (10 and 150 L). The possible mechanisms of the effect of carbon dioxide upon the growth of Staphylococcus aureus (Foggi) and the production of the enzyme are discussed.
Bioconversion of hemicellulose: Aspects of hemicellulase production by Trichoderma reesei QM 9414 and enzymic saccharification of hemicellulose
Authors: Dekker Robert F. H.
Published: December 2004

The growth of Trichoderma reesei QM9414 in shake flasks at 28°C on hemicellulose substrates and bagasse resulted in rather low yields of hemicellulolytic enzymes (1.0–1.5 units/mL xylanase and 0.05–0.08 units/mL β‐xylosidase). The influence of pH on the synthesis of β‐xylosidase was greater than on the synthesis of xylanase. Both xylanase and β‐xylosidase showed optimal activity at pH 4–5 and 55–60°C. Xylanase was stable at pH 2–10 but was heat labile and totally inactivated after 1 h at 65°C. Enzyme stability towards heat could be increased in the presence of bovine serum albumin. The β‐xylosidase was more tolerant to heat, but stable over a pH range 2.5–6.0. The D‐xylose inhibited both enzymes in a competitive manner. Hemicellulose (heteroxylan) was degraded to the extent of 30–40%within 24 h. The degree of hydrolysis decreased as the substrate concentration increased and increased with increased amounts of enzyme. Multiple enzyme doses resulted in increased saccharification in reduced times. The degree of hydrolysis was influenced by the amount of β‐xylosidase present in the hemicellulolytic enzyme preparation. The ‐;xylosidase was demonstrated to play an important role in the overall conversion of heteroxylan into xylose that is analogous to the role of β‐glucosidase in the saccharification of cellulose by cellulases.
A minicomputer system for analyzing and reporting pilot plant fermentor data
Authors: Bowski Leo , Perley Christopher R. , West John M.
Published: December 2004

In 1979, a minicomputer system was developed for Hoffmann‐La Roche by ABEC, Inc. for the purpose of achieving on‐line analysis and reporting of data from 16 70‐L pilot‐plant fermentors (New Brunswick Scientific Co.). The system consists of a PDP 11/60 computer with 96K core capacity, two RL01 disk drives, two RX01 floppy‐disk drives, LA‐36 DECwriter terminal, Tektronix CRT, and Versatec printer plotter. DEC, PDP, RSX, RL01, RX01, LA‐36, and DECwriter are trademarks of Digital Equipment Corporation. The computer software comprises three distinct groups of programs. RSX‐11M is a disk‐based operating system that allows quick response to realtime events, such as process monitoring and data acquisition, while carrying out less time‐dependent activities, such as program development and graphical output. The AIM (Biles, Inc.) system is used to acquire and convert the voltage signals produced by pilot‐plant instrumentation into engineering units. Analysis and graphical output are executed by ABEC and Versatec supplied programs. The most beneficial task performed by the computer is the production of graphical output of a variety of measured and analyzed data. This has led to an increase in personnel productivity and design of more meaningful experiments. An ancillary function of the system is to pick up data logged by a PDP 11/03 computer from a remote fermentation production plant by means of a MODEM interfaced communication link. Production data are analyzed and presented in a form identical with pilot‐plant data. The experience with the system is discussed in this article.
Purification of chymotrypsin by subunit exchange chromatography on the denatured protein
Authors: Carrea G. , Pasta P. , Antonini E.
Published: December 2004

The α‐chymotrypsin subunits immobilized under denaturing conditions (6 M urea or 1% SDS) on CNBr‐activated Sepharose 4B, were found to interact with soluble chymotrypsin subunits with the formation of oligomers higher than dimers. Subunits immobilized under nondenaturing conditions form only dimers. The effects of several parameters, such as organic solvents, cations, and anions of the lyotropic series, on the associating properties of the immobilized derivatives were examined. The interaction between immobilized and free enzyme was shown to be specific because extraneous proteins and compounds were not bound by the derivatives. Chymotrypsinogen, studied analogously, did not show appreciable self‐associating capacity. Chymotrypsin subunits immobilized under denaturing conditions and packed in a column proved to be suitable for the purification of chymotrypsin from both bovine and porcine pancreatic extracts. The “subunit exchange” chromatography of such extracts, carried out between pH 2.5 and 4, gave an eightfold purification with a 93% recovery of chymotryptic activity. The specific activity was ca. 12,000 Schwert and Takenaka units/mg. Only 6% of the tryptic activity was bound by the column. The capacity of the matrix, 6 mg chymotrypsin/mL, dropped to about 70% of the original value after