bluuebunny/crossref_metadata_2025 huggingface dataset:
Alcohol fermentation of sweet potato. I. Acid hydrolysis and factors involved
Authors: Azhar A. , Hamdy M. K.
Published: December 2004

Factors affecting acid hydrolysis of sweet potato powder (SSP) to fermentable sugars were examined. These include HCl concentration, temperature, time, and levels of SPP. Maximum reducing sugar, reported as dextrose equivalent (DE), was detected after 24 min hydrolysis (1% SPP) in 0.034N HCl heated at 154°C. These samples also had 3.43% droxymethylfurfural (HMF) based on dry weight. A high level of HMF (9.2%) was detected in 1% SPP heated at 154° in 0.10N HCl for 18 min. The lowest concentration of HMF formed (1.8%), at maximal DE of 61%, was established in samples containing 5% SPP and heated at 154° in 0.034N HCl for 48 min. Aqueous extracts of uncured SPP, examined by HPLC, contained glucose, fructose and sucrose, but degraded SPP had only glucose and fructose. Products of degraded SPP, under appropriate conditions, could be used for alcohol fermentation.
Immobilization of Brevibacterium flavum cells on collagen for the production of glutamic acid in a recycle reactor
Authors: Constantinides Alkis , Bhatia Daleep , Vieth Wolf R.
Published: December 2004

In this study, live cells of Brevibacterium flavum were immobilized for the production of glutamic acid. The reason for such a choice was that glutamic acid fermentation is an extensively studied fermentation and one which requires the viability of entire cellular faculties for the acid production. Brevibacterium flavum was chosen because it is an industrially used bacterium, and is very potent via a vis glutamic acid production. Studies were performed to find aeration and agitation conditions for optimal growth and glutamic acid productivity. Experiments were also done to find the optimum harvesting time. The cell activity peaks during the run of fermentation, and the time at which the peak occurs, was found. Conventional methods for immobilizing the cells on collagen were found to be lacking. The pH and drying were the two main reasons for loss of viability of the cells; the latter being more important. A modified immobilization procedure has been devised, which can immobilize live cells at any given pH and ionic strength, in contrast to the conventional method which requires the pH to be above 11 or below 3. This new method involves dialysis of collagen in suitable dialysis bags against water at pH7 (or buffer at any desired pH). The dialysed collagen blended at 20,000 rpm, resulted in a very smooth dispersion, unnoticeably different from collagen dispersion prepared at pH 11. The dispersed collagen was then cast and dried at an elevated temperature, and high air flow rate over the cast membrane, decreasing the time of drying from 6–8 hr ( in the conventional method) to 1.5–2 hr. The membrane has been tested for glutamic acid producing capabilities in a column reactor with the membrane spirally wound. The reactor has been operated under continuous conditions for 5–10 days with stable activities.
Ribonuclease isolated from yeast (Saccharomyces carlsbergensis): Characterization and properties
Authors: Shetty J. K. , Weaver R. C. , Kinsella J. E.
Published: December 2004

The homogeneity of a purified ribonuclease from brewers' yeast was determined by velocity sedimentation and polyacrylamide gel electrophoresis techniques. The velocity sedimentation pattern gave a single peak with a Sapp 3.46 and polyacrylamide gel electrophoresis showed one major band. The absorption spectrum of the enzyme showed maximum absorption at 277–278 nm and minimum at 252 nm. The enzyme was relatively stable to extreme pH values and high temperature. Both NaCl and KCl increased the enzyme activity whereas enzyme was inhibited by divalent metal ions. The inhibition of the enzyme was increased in the order of Ca2+ > Mg2+ > Fe2+Cu2+. Chemical modification studies of the enzyme showed that tryptophan residues and disulfide bonds were required for enzyme activity.
Conversion of the enzymatic hydrolysate of shellfish waste chitin to single‐cell protein
Authors: Revah‐Moiseev Sergio , Carroad Paul A.
Published: December 2004

The conversion of the enzymatic hydrolysate of shellfish chitin waste to single‐cell protein was investigated as part of a comprehensive waste treatment program. Forty‐two yeasts were screened for ability to assimilate the monomer of chitin, N‐acetylglucosamine, which has been shown to be the sole product of enzymatic hydrolysis of chitin. The Yeast Pichia Kudriavzevii was selected for study, based on ability to grow at high temperature (37°C and above), low pH (4.0 ± 0.5), and in a nutritionally simple medium. Growth rates of P. kudriavzevii were similar on N‐acetylglucosamine and on the chitin hydrolysate. Dependencies of specific growth rate on temperature, pH, medium composition, and oxygen tension were studied. The variations of yield, protein content, and total nucleic acid content with the specific growth rate were evaluated. The amino acid distribution of the protein of P. kudriavzevii was obtained.
Enzymes in preparative organic synthesis: Coincidence of the pH optimum for catalyst effectiveness with the pH optimum for the catalyzed reaction equilibrium
Authors: Martinek Karel , Semenov Anatole N. , Berezin Ilya V.
Published: December 2004

The study concerned the pH profile of the apparent equilibrium constant for synthesis of N‐benzoyl‐L‐phenylalanine ethyl ester from the respective acid and ethanol in the biphasic system chloroform + 5% (v/v) water. The substitution of water (as a reaction medium) for the biphasic aqueous–organic system shifted the pH profile toward neutral pH values. As a result the pH range thermodynamically conducive to synthesis of the final product in the biphasic system coincided with the pH optimum of the catalytic activity of the enzyme used (α‐chymotrypsin). This approach should, in principle, be considered as general: first, per se it is independent of a catalyst (enzyme) nature; second, the biphasic method helps the shift ionic equilibria involving not only organic acids, but also bases. A physical mechanism of the ionic equilibrium shift is the same is both cases, namely, a preferable extraction from water into an organic phase of one generally nonionic (more hydrophobic) form of the reagent.
Utilization of carbohydrates by Thermomonospora sp. Grown on glucose, cellobiose, and cellulose
Authors: Moreira A. R. , Phillips J. A. , Humphrey A. E.
Published: December 2004

Thermomonospora sp. was grown on glucose, cellobiose, and in order to study its growth characteristics with different carbohydrate substrates and to assess the validity of some of the assumptions made in a previously proposed model for the cellulose fermentation with this microorganism. It was observed that the nitrogen and protein contents of the cells are essentially constant during the fermentation and independent of the carbon source when glucose or cellobiose are utilized. Under oxygen starvation conditions it was shown that unidentification organic compound(s) accumulate(s) in the culture broth. Culture fluorescence was shown to be an excellent variable for monitoring and control of the fermentation process. This microorganism showed a preference for crystalline cellulose (Avicel) as substrate although it grows readily on a more amorphous cellulose (Solka Floc). The production of extra cellular protein is shown to be growth related. Data were obtained confirming the decrease in the number of active adsorption sites as the cause for the decrease in the cellulose digestion rate. It is suggested that a future model should account for the time change of surface characteristics of the cellulose particles.
Production of cellulases by Thermomonospora sp.
Authors: Moreira A. R. , Phillips J. A. , Humphrey A. E.
Published: December 2004

Glucose, cellulose, Avicel, and Solka Floc were utilized as substrates for growth of Thermomonospora sp in order to study the induction–repression characteristics of its associated cellulase system. While glucose proved to be an effective repressor of the cellulase enzymes, the other three substrates induced relatively high levels of enzyme activity as measured by the filter paper assay. On a unit cell mass basis the highest values of cellulase activity were obtained when Avicel was utilized as the carbon and energy source. The nature of the cellulosic material and its initial concentration were identified as two very important parameters of the induction process.
A novel method for determining the parameters of microbial kinetics
Authors: Szetela Ryszard W. , Winnicki Tomasz Z.
Published: December 2004

It is conventional to describe the relationship between the specific rate of microbial growth and the concentration of the inhibitory substrate in terms of the Andrews–Edwards equation. A novel method for establishing the constants of this equation is presented. The equation is transformed to a polynomial and the empirical data are approximated by a quadratic polynomial. The results obtained for the biodegradation of phenol in a mixed culture (activated sludge) are discussed.
Eeffect of pH on growth in a respiration‐deficient mutant of Saccharomyces cerevisiae
Authors: Sawada Tatsuro
Published: December 2004

The effects of pH on the budding cycle of a respiration‐deficient mutant of Saccharomyces cerevisiae were investigation by monitoring the time course of bud development on single cells. The volume of each bud was measured at various time intervals between the inception of its development and inception of development of the next bud on the mother cell. A previous report that the budding cycle consisted of two phases (a rapid‐growth phase and a slow‐growth phase) was confirmed. With increase in pH from 3.8 to 6.0 the budding cycle shortened as a result of both increase in rate of the rapid‐growth phase and decrease in the duration of the slow‐growth phase. Although further increase in pH to 7.4 further increased the rate of the rapid‐growth phase, the budding cycle lengthened as a result of an increase in time lag and increase in duration of the slow‐growth phase. The growth rate, in terms of bud volume, conformed with the expression: (1/V)(dV/dτ) = ξ exp(–V/η), where the values of ξ and η were dependent on pH. The cell volume distribution in a batch culture was compared with the cell volume distribution calculated from the growth curve of a single bud. Similarities in the curves suggested that the growth pattern of a whole culture reflected the growth pattern of a single cell.
Mixed cultures: Commensalism and competition with Proteus vulgaris and Saccharomyces cerevisiae
Authors: Tseng Murray M‐C. , Phillips Colin R.
Published: December 2004

Several modes of interaction are demonstrated and modeled in the Proteus vulgaris–Saccharomyces cerevisiae system, in particular, commensalism (citrate present. glucose limiting, the nicotinic acid required by the bacterium supplied by the yeast), and commensalism and competition [citrate absent, both organisms compete for the same limiting carbon source (glucose) and the yeast supplies the nicotinic acid for the bacterium]. By varying the medium component concentrations, competition (citrate absent, glucose limiting, nicotinic acid not limiting), mutualism (citrate excess, glucose limiting, nicotinic acid absent), and neutralism (citrate limiting, glucose limiting, and nicotinic acid excess) could also be created. Kinetic models for commensalism and commensalism plus competition were developed to describe cell growth, substrate utilization, and nicotinic acid production. Good agreement with experiment was obtained for the commensalism case.
Production of earthworms as a potentially economical source of protein
Authors: Hartenstein Roy
Published: December 2004

The main objectives of this study were (1) to determine the optimum frequency for transferring a fixed population of Eisenia foetida into fresh surroundings to effect maximum production of earthworm biomass, (2) to determine carrying capacity and maximum production of E. foetida biomass per unit area–volume–time at 24°C, and (3) to measure the nucleic acid concentration of this earthworm. Population were rapidly decimated in limed peat moss with horse manure as food when transferred weekly or when held for ten weeks in the same substrate; no significant differences and high survival obtained at intermediate intervals. Significantly more cocoons were produced when transfers were made every two weeks, and a trend was seen toward a lower level of cocoon production with length of detention in substrate. The growth rate of adults was approximately similar in relation to the frequency of transfer, as was biomass, at transfer frequencies of every 2 to 9 weeks. One interpretation of the data is that a detention interval of 6 to 8 weeks is optimum for maximizing production of biomass; eight weeks is the interval commonly selected in commercial practices. Carrying was 9.5 g live weight on a surface area–volume of 24 cm2–110 cm3 with horse manure as food on 20 g of soil as substrate; maximum production in this space was 2 g live weight in 7 weeks, which extrapolates to 6685 kg protein/ha yr. Nucleic acid concentration was 2.9%, which falls below values of about 6–28% obtained for microbes, and may exceed values for mammalian muscle by about twofold.
Single‐cell protein production from spent sulfite liquor utilizing cell‐recycle and computer monitoring
Authors: Gold Daniel , Mohagheghi Ali , Cooney Charles L. , Wang Daniel I. C.
Published: December 2004

Spent sulfite liquor (SSL), a waste product of the paper pulping industry, is produced at a rate of 1 ton (dry basis) per ton of pulp. The sugar content of SSL is about 30 g/L. To reduce the biological oxygen demand (BOD) of SSL before disposal, torula yeast (Candida utilis) is produced by a continuous culture process, the productivity of which is limited by sugar concentration and cell growth rate. To increase productivity, a recycle system has been designed and tested. Cells were sedimented continuously with a flocculating agent (bentonite) before being recycled to the fermentor. A bentonite concentration of 0.02 g/g cell was required. A computer monitoring system based on material balancing techniques was developed to monitor and control the recycle system. With this computer system, productivity was raised to 6.1 g/L h, with cell concentration up to 65 g/L in the recycle stream and 24 g/L in the fermentor. This represents a productivity increase of 150% over continuous culture with no recycle.
Kinetic modeling of a multiple immobilized enzyme system. II. Application of the model
Authors: Mercer D. G. , O'Driscoll K. F.
Published: December 2004

The mathematical model for the reaction sequence catalyzed by immobilized invertase and glucose oxidase discussed in the preceding article has been used successfully to duplicate experimental findings. In addition, it has been used as a tool for the simulation and prediction of effects derived from alterations to system‐related and gel‐related parameters. The effects of gel diffusivity on the overall conversion of sucrose substrate to reaction products was investigated through use of this model. Changes in the enzyme loading within a gel and the results of varying the ration of invertase activity to glucose activity were also evaluated. Through use of concentrations of the molecular species determined at the collocation points within a gel particle and in the bulk liquid phase, an estimate of the thickness of the diffusion boundary layer around the gel particle was determined which was in close agreement with values obtained from classical mass transfer relationships. For most of this study, the enzymes were coimmobilized within the same polymeric matrix. However, a number of tests were run with the enzymes immobilized individually and placed in separate reactors in a sequential reactor system. The experimental results from these tests were duplicated successfully by means of the model with little modification to the basic computer program. Such an example illustrates the potential flexibility of the model and its overall versatility.
Five‐year perspective of the large‐scale growth of mammalian cells in suspension culture
Authors: Zwerner R. K. , Cox R. M. , Lynn J. D. , Acton R. T.
Published: December 2004

The Cell Culture Center at the University of Alabama in Birmingham was set up to produce large quantities of cells and their products from suspension cultured cell lines. This system has now been in operation for over five years and has been effective in producing large quantities of mammalian cells of murine and human origin. This article describes the system and some growth parameters which have been of importance for large‐scale mammalian cell growth.
Inhibitory effects of particulate materials in growing cultures of Thiobacillus ferrooxidans
Authors: Dispirito Alan A. , Dugan Patrick R. , Tuovinen Olli H.
Published: December 2004

Particulate materials (flowers of sulfur, fluorapatite, glass beads, and pyrite) inhibited the growth of Thiobacillus ferrooxidans on ferrous iron at pH 1.5. The degree of inhabitation varied with the type of the particulate and culture conditions. The inhibition caused by pyrite involved a soluble toxic component. The inhibition caused by sulfur particles and glass beads was alleviated by incubation under static culture conditions (i.e., no shaking) but oxidation rates declined because of lack of aeration an increase in the pH above 2 also relieved the inhibition. The nature of inhibition. The nature of inhibition by different particles varied from declined iron oxidation rates to prolonged lag periods depending on the concentration of the test material. Thus, the results indicate that the bacterial activity at the liquid‐solid interface is different from that in the bulk liquid phase and is influenced by the proton concentration and by the physiochemical properties of the solids.
Effect of chemical treatments on the degradability of cotton straw by rumen microorganisms and by fungal cellulase
Authors: Miron Josual , Ben‐Ghedalia Daniel
Published: December 2004

Three different chemical treatments—sulfur dioxide, ozone, and sodium hydroxide—were applied on cotton straw, and the effect on cell‐wall degradability was assessed by using rumen microorganism and Trichoderma reesei cellulase. Sulfur dioxide (applied at 70°C for 72 h) did not change the lignin content of cotton straw but reduced the concentration of hemicellulose by 48%. Ozone exerted a dual effect, both on lignin (a 40% reduction) and hemicellulose (a 54% decrease). The treatment with NaOH did not solublize cell‐wall components. The in vitro organic matter digestibility with rumen fluid of cotton straw was increased significantly by ozone and SO2 treatments, by 120% and 50%, respectively, but not by NaOH. T. reesei cellulase was applied on the chemically pretreated cotton straw at a low level (6 filter paper U/g straw, organic matter), and the release of reducing sugars was determined. The highest level of reducing sugars (30.6 g/100 g organic matter) was obtained with the O3‐cellulase combination, which solubilized 64% of the cellulose and 88% of the hemicellulose. the SO2‐ and the NaOH‐pretreated cotton straw were hydrolyzed by T. reesei cellulase to the same extent (21 g reducing sugars/100 g organic matter). The rumen fluid digestibility of the enzymatic ally hydrolyzed straw was not increased further over the effect already obtained with the chemical pretreatments. However, the fermentability of the combined treatments was increased markedly. In the O3‐cellulase‐treated cotton straw, 83% of the rumen fluid digestible material consisted of highly fermentable components. Although ozone proved to be the most potent pretreatment for enzymic saccharification in this study, the absolute result was modest. The limited effect of the combined O3‐cellulase treatment was probably associated with the pretreatment limitations, but not with the enzyme level. Based on the differential response of the chemically treated cotton straw to attack by rumen microorganisms on the one hand, and by T. reesei cellulase on the other hand, a hypothesis has been suggested as to the location of lignin and hemicellulose in the cellwall unit of cotton straw.
The effect of Hofmeister anions and protein concentration on the activity and stability of some immobilized NAD‐dependent dehydrogenases
Authors: Carrea G. , Bovara R. , Pasta P. , Cremonesi P.
Published: December 2004

The effect of several factors on the activity and stability of alcohol dehydrogenase, glyceraldehyde‐3‐phosphate dehydrogenase, and 20β‐hydroxysteroid dehydrogenase, both free and immobilized on CNBr‐activated Sepharose 4B, was investigated. Enzymes were im‐ mobilized under different conditions including various degrees of matrix activation, variable amounts of protein, in the presence, or in the absence of, additives (coenzymes, dithioth‐ reitol, salts). Activity recovery was in general satisfactorily high with 20β‐hydroxysteroid dehydrogenase, low with glyceraldehyde‐3‐phosphatedehydrogenase, and markedly linked to the concentration of immobilized protein with alcohol dehydrogenase. In the latter case the advantageous stabilizing effect of high enzyme concentrations was notably diminished by the parallel decrease of the effectiveness factor. The effect of high concentrations of anions of the Hofmeister series was examined. It was found that 1M phosphate and 0.5M sulfate dramatically stabilize both free and immobilized enzymes against inactivation by temperature and urea. Km, values of apolar substrates were considerably lowered by the two anions while Km values of polar substrates were not affected. In some cases Vmax values also were influenced by high concentrations of these anions. The present results appear of interest particularly in view of enzyme utilization for analytical as well as for preparative purposes.
Enzymatic synthesis of formic acid from H2 and CO2 and production of hydrogen from formic acid
Authors: Klibanov Alexander M. , Alberti Barbara N. , Zale Stephen E.
Published: December 2004

Whole cells of Alcaligenes eutrophus (as well as isolated P. oxalaticus formate dehydrogenase and A. eutrophus hydrogenase coupled via NAD+ or methyl viologen) have been shown to produce H2 from formic acid. Immobilization of the cells in kappacarrageenan gel greatly enhances their stability at room temperature. The rate of hydrogen production catalyzed by immobilized A. eutrophus has been studied as a function of the concentrations of the cells and formate and also pH. An inhibition by high concentrations of formate has been found. Immobilized cells were also capable of synthesizingformate from H2 and bicarbonate. Yields of formate up to 30% have been obtained. The catalytic efficiency of immobilized A. eutrophus cells was compared with that of palladium adsorbed on activated carbon.
Phosphorus uptake and growth of blue‐green alga, Microcystis aeruginosa
Authors: Okada Mitsumasa , Sudo Ryuichi , Aiba Shuichi
Published: December 2004

The specific uptake rate Qp of orthophosphate (expressed throughout as phosphorus) and the specific growth rate μ of Microcystis aeruginosa were measured using batch‐precultured cells, whose growth phase, and intracellular and extracellular phosphorus concentrations fp and P, respectively, had been changed. When the cells from phosphorus‐rich precultures were used, smaller values of Qp (0.1–0.3 μg P mg dry wt. −1 h −1) were observed. However, if phosphorusstarved cells were used, the initial value of Qp was enhanced to more than ten times those smaller values referred to above, but declined rapidly with time after the transfer. Qp leveled off at around t = 4 h, when fp approached the maximum value, even if phosphorus was still available in the medium. A new correlation was presented here with respect to Qp as a function of P and fp as follows:

Although numerical values of parameters involved in the equation depend on physiological state (or preculture history) of the cells, the above equation could account not only for phosphorus uptake, during which changes in phosphorus content in the cells were observed, but also for initial rates of uptake presented previously by other workers. μ Values were confirmed to be a hyperbolic function of fp as has been suggested by previous workers.
Photosynthetic regeneration of ATP using a strain of thermophilic blue–green algae
Authors: Sawa Yoshihiro , Kanayama Kazumi , Ochiai Hideo
Published: December 2004

Photosynthetic ATP accumulation was shown in the presence of exogenous ADP plus orthophosphate on illumination to the intact cells of a strain of thermophilic blue–green algae isolated from Matsue hot springs, Mastigocladus sp. Kinetic studies of various effectors on the ATP accumulation proved that the ATP synthesis depends mainly on the cyclic photophosphorylation system around photosystem I (PS‐I) in the algal cells. The temperature and pH optima for the accumulation were found at 45°C and pH 7.5. Maximum yield was obtained with light intensity higher than 15 mW/cm2. Borate ion exerted pronounced enhancement on the ATP synthesis. With a continuous reactor at a flow rate of 1 ml/hr at 45°C and pH 7.5, efficient photoconversion of ADP (2mM, at substrate reservoir) to ATP (1mM, at product outlet) has been maintained for a period of 2.5 days, though the efficiency has decreased in a further 2‐day period to the level of 0.5mM ATP/9.5 h of residence time.
Kinetics of biofilm nitrification
Authors: Tanaka H. , Dunn I. J.
Published: December 2004

The reaction rates (r and r) in the two‐step nitrification reaction were measured in a fluidized‐sand‐bed biofilm reactor under a range of steady‐state conditions with respect to bulk NH, NO, and O2 concentrations. It was shown from theory and experiment that under low NH concentration conditions, if the O2/NH concentration ratio in the bulk liquid is less than the stoichiometric coefficient (3.4 mg/mg), then oxygen will be rate limiting. In all experiments r decreased more than r under low oxygen conditions. This resulted in high NO effluent concentrations under low residence time conditions. The influence of the oxygen penetration effects on the relative values of r and r was experimentally shown to be caused either by the Nitrobacter location in the inner biofilm regions or by a Km effect for oxygen. Theoretical support of these findings was provided by a differential diffusion‐reaction model which was used to simulate the experimental results.
Studies on immobilized Saccharomyces cerevisiae. III. Physiology of growth and metabolism on various supports
Authors: Bandyopadhyay K. K. , Ghose T. K.
Published: December 2004

In earlier communications general analyses of rapid ethanol fermentation by Saccharomyces cerevisiae immobilized on inert supports were described. In this article physiology of growth and metabolism (parameters like rates of CO2 evolution and O2 uptake, respiratory quotient, and generation time) of Saccharomyces cerevisiae immobilized on different supports are reported. Values of the ratio of specific oxygen uptake rate for immobilized cells to free cells have been found to be 0.732, 0.781 and 0.785 for carrier A, carrier B, and covalently crosslinked controlled pore glass (CPG, specific surface area of 439 m2 g−1), respectively. Rates of specific CO2 evolution for immobilized cells to free cells for these supports are 0.784, 0.822, and 0.783, respectively. Marked reduction in generation time of Saccharomyces cerevisiae on all the supports has been observed. No change in size (4.8–5 μm) and specific growth rate (μm = 0.275 h−1) of cells leaving the reactor has been observed.
Identification of mass‐transfer parameters and process simulation of SCP production process in airlift tower reactors with an external loop
Authors: Luttmann R. , Buchholz H. , Zakrzewski W. , Schügerl K.
Published: December 2004

A distributed parameter model for simulation of SCP‐production processes in tower reactors with an outer loop was developed by considering substrate, cell, and CO2 balances in the liquid phase, and O2 and CO3 balances in the ges phase and taking into account variations of dissolved oxygen concentration, pressure, and kLa along the column, as well as double substrate Monod kinetics. This model was used to describe the cultivation of Hansenula polymorpha in a tower‐loop reactor (height 275 cm, diameter 15 cm). Parameter identification and process simulation were carried out by a hybrid computer. The variation of identified mass transfer parameters with fermentation time and operation mode is considered employing ethanol and glucose substrate, respectively. Relationships among kLa, substrate concentration, and superficial gas velocity were developed to facilitate the layout and simulation of pilot‐plant reactors.
Immobilization of horse liver alcohol dehydrogenase on copolymers of glycidyl methacrylate and ethylene dimethacrylate
Authors: Kovář J. , Navrátilová M. , Skurský L. , Drobník J. , Švec F.
Published: December 2004

Alcohol dehydrogenase has been immobilized to the basic copolymer and its several derivatives using various techniques. Enzyme coupling to the supports with amino groups by means of glutaraldehyde was found the most suitable. Activity of alcohol dehydrogenase coupled to these amino supports was comparable to that of the enzyme bound to Sepharose. Thermal and pH stability of alcohol dehydrogenase increased essentially upon immobilization. Kinetic properties of the immobilized enzyme differed from those of free alcohol dehydrogenase, pH optimum shifted to alkaline range, and apparent Michaelis constants for substrates and coenzymes increased. Curvatures observed in Lineweaver‐Burk plots for coenzymes suggest an involvement of diffusion effects in the reaction catalyzed by alcohol dehydrogenase linked to these polymers.
The influence of precipitation reactor configuration on the centrifugal recovery of isoelectric soya protein precipitate
Authors: Bell D. J. , Dunnill P.
Published: December 2004

The strength and rheological characteristics of isoelectric soya protein precipitate, prepared in continuous tubular and batch‐stirred tank reactors, were determined in relation to the separation efficiency and sludge discharge characteristics of intermittent disk and scroll discharge centrifuges. The batch tank precipitate showed greater resistance to aggregate shear breakup than the tubular reactor precipitate. This difference was of significance to the separation efficiency of the scroll centrifuge only. The tubular reactor precipitate sludge showed greater resistance to shear deformation and resulted in drier sludge for a given scroll differential speed. some compressive dewatering occurred for both types of precipitate sludge but shear‐induced dewatering is proposed as the major mechanism. This study illustrates the need to integrate the design of protein precipitate formation and centrifugal recovery operations.
Kinetic studies of enzymatic hydrolysis of insoluble cellulose: Analysis of the initial rates
Authors: Lee Yong‐Hyun , Fan L. T.
Published: December 2004

A study was conducted on the kinetics of enzymatic hydrolysis of pure insoluble cellulose using unpurified culture filtrate Trichoderma reesei, with the emphasis on the initial reaction period. The initial hydrolysis rate and extent of enzyme (soluble protein)adsorption, either apparent or initial, were evaluated under various experimental conditions. It has been found that the various mass‐transfer steps do not control the overall hydrolysis rate and that the hydrolysis rate is mainly controlled by the surface reaction step promoted by the adsorbed enzyme. It has also been found that the initial hydrolysis rate strongly depends on the initial extent of soluble protein adsorption and the effectiveness of the adsorbed soluble protein to promote the hydrolysis. The initial extent of soluble protein adsorption, in turn, is related to the initial cellulose concentration, enzyme concentration, and specific surface area of cellulose, whereas the effectiveness of the initially adsorbed soluble protein to promote the derived to interrelate these parameters without resorting to the Michaelis–Menten kinetics. The present result appear to imply that the role of enzyme–substrate complex formation should not be ignored in deriving a mechanistic kinetic model for enzymatic hydrolysis of cellulose.
Continuous enzymatic liquefaction of starch for saccharification
Authors: Carr M. E. , Black L. T. , Bagby M. O.
Published: December 2004

A process was explored for continuous enzymatic liquefaction of corn starch at high concentration and subsequently saccharification to glucose. The process appears to be quite efficient for conversion of starch to glucose and enzymatic liquefaction and should be readily adaptable to industrial fermentation processes. Preliminary work indicated that milled corn or other cereal grains also can be suitably converted by such a process. Essentially, the process involved incorporation of a thermostable, bacterial α‐amylase for liquefaction and, subsequently, of a glucoamylase into the continuous mixer under conditions conductive to rapid enzymatic hydrolyses. Also studied was the effect on substrate liquefaction of variable such as starch concentration (40–70° ), level of α‐amylase (0.14–0.4%, dry starch basis), temperature (70–100°C), pH (5.8–7.1), and residence time (6 and 12 min). The degree of liquefaction was assessed by determining (1) the Brookfield viscosity, (2) the amount of reducing groups, and (3) the rate and extent of glucose formed after glucoamylase treatment. Best liquefaction process conditions were achieved by using 50–60% starch concentration, at 95°C, with 0.4% α‐amylase, and a 6‐min residence period in the mixture. Under these conditions, rate and extents of glucose obtained after glucoamylase treatment approached those obtained in longer laboratory batch liquefactions. The amount of glucose formed in 24h with the use of 0.4% glucoamylase was 86% of theory after a 6‐min continuous liquefaction, compared to 90% for a 30‐min laboratory batch liquefaction (95°C, 0.4% α‐amylase).
Processes governing primary biofilm formation
Authors: Bryers James D. , Characklis William G.
Published: December 2004

Biofilm accumulation under turbulent flow condition on the surface of a circular tube is the net result of several process including the following: (1) transport and firm adhesion of soluble components and microbial cell to the surface; (2) metabolic conversions within the biofilm in cluding growth and maintenance decay process; (3) detachment of portions of the biofilm and reentrainment in the bulk fluid. Experiments in tabular reactor were designed to measure the rates of these process during the early stages of biofilm accumulation as a function of the Reynolds number and suspended biomass concentration. Results indicate deposition (i.e., combined transport and adsorption) is only important in the very early stages of biofilm accumulation and is significantly influenced by negligible for the thin biofilms encountered in these experiments. Net biofilm production rates in all experiments decrease to same level and this level is not affected by changes in Reynolds number or suspended biomass concentration. Biofilm detachment rate increases continuously with biofilm accumulation and with increasing Reynolds number.
Effects of attachment of bacteria to chemostat walls in a microbial predator–prey relationship
Authors: Ratnam Diwakaran A. , Pavlou Stavros , Fredrickson A. G.
Published: December 2004

Mixed cultures of the protozoan Tetrahymena pyriformis and the bacterium Escherichia coli were propagated in chemostats fed with glucose and minimal mineral salts medium. The interior surfaces of some chemostats were treated with a silicone compound but those of other chemostats were not. Data obtained showed that bacteria but not protozoans were attached strongly to the walls of the chemostats, that silicone treatment reduced the density of the attached bacteria by two orders of magnitude or more, and that the presence of the attached bacteria had significant effects on the dynamics of the microbial predator–prey system. Attempts were made to simulate the data by various mathematical models. It was found that a model based on combination of the Topiwala–Hamer model for wall attachment and a multiple saturation model for growth of the protozoans on the bacteria gave a reasonable fit of all the data.
The effect of the oxygen transfer rate (OSR) on the formation of cellulases by Trichoderma viride in submersion culture
Authors: Škachová Helena , Gottvaldová Maria , Kučera Jiří , Podrazký Vladimíir
Published: December 2004

The formation of cellulases by Trichoderma viride in a medium containing cellulose as a sole source of carbon depends on the oxygen transfer rate (OSR); the OSR, on the other hand, depends on the concentration of cellulose in the medium because the concentration of cellulose strongly affects the viscosity of the medium. In the work presented here, the dependence has been determined for the oxygen transfer rate on geometric relations and viscosity in cellulose‐containing media during cultivation in shaken flasks, and the oxygen transfer rate on NRe' NG' and Na during cultivation in a laboratory fermentor of 3000‐mL volume. Two cellulosic materials have been compared with a different effect on viscosity: Microcrystalline beach cellulose and fibrous cellulose. It has been found that, in an applicable range of concentration, microcrystalline cellulose does not affect the oxygen transfer rate (at concentrations up to 3%). Fibrous cellulose increases the OSR during cultivation in shake flasks but decreases it during civilization in fermentors. On the basis of these results, the optimization has been carried out on the cultivation conditions in fermentors.
Enzyme immobilization by the coulomb force
Authors: Furusaki Shintaro , Asai Nobuhiro
Published: December 2004

A new immobilization technique has been developed. It involves immobilizing enzymes on a porous polytetrafluoroethylene membrane with a nonporous polyurethane coat by the use of an electrostatic force, i.e. the Coulomb force. The immobilized enzyme can be recovered by supplying a reversed electrical potential. The reaction characteristics of the immobilized amyloglucosidase were studied using maltose as a substrate. The Michaelis constant becomes larger than that of the native enzyme, and depends on the electrical potential gradient in the solution.
Factors affecting the pretreatment of biomass with gaseous ozone
Authors: Neely W. C.
Published: December 2004

Treatment of a wide variety of lignocellulosic biomass with gaseous ozone results in greatly enhanced susceptibility to cellulase enzyme hydrolysis and to digestion by rumen microorganisms so that it can be used as ruminant animal feed or for the production of glucose via enzymatic hydrolysis. By use of appropriate reaction conditions a useful degree of such pretreatment may be obtained in 1–2 h contact time with an ozone consumption of ca. 4–6% of the dry weight of the biomass.
Isolation of an inulinase derepressed mutant of Pichia polymorpha for the production of fructose
Authors: Bajon A. M. , Guiraud J. P. , Galzy P.
Published: December 2004

Pichia polymorpha has inulinase activity and could be used for the production of fructose syrup from inulin. The application of immobilized P. polymorpha whole cells for the continuous hydrolysis of inulin is, however, limited since the biosynthesis of this enzyme system is repressed by the reaction products, dextrose and fructose. A derepressed mutant hyperproducer of inulinase was isolated after treatment with EMS followed by a selection step with deoxyglucose.
Studies on nitrification of aniline with acclimated activated sludge
Authors: Kumar N. Jothi , Krishnamoorthi K. P. , Swaminathan T.
Published: December 2004

Aniline, a toxic, organic pollutant, occurs in a number of industrial effluents. Apart from carbonaceous oxygen demand, aniline imposes a nitrogenous oxygen demand, due to its nitrogen content, in excess of that required for cell growth. Incomplete biodegradation will result in ammonia production; this also exerts toxicity. Hence, nitrification of aniline should be ensured in the biological treatment before discharge into receiving streams. Aniline, however, is reported to inhibit the nitrification process. Aniline degradation was studied in laboratory continuous activated sludge with an acclimated culture developed in synthetic feed to determine the extent of complete biological degradation. Aniline–N (even at 400 mg/L aniline concentration)could be converted to nitrate–N with ammonium–N and nitrite–N formed as intermediates at a detention time of 24 h. The nitrification, however, was suppressed by aniline. The degradation of aniline to ammonia releases the suppression and the nitrification proceeds rapidly.
Accumulation of heavy‐metal ions by Zoogloea ramigera
Authors: Norberg Anders B. , Persson Hans
Published: December 2004

Biomass has been produced from glucose using the organism Zoogloea ramigera 115. This biomass has been used to remove copper, cadmium, and uranyl ions from water solutions. The metal uptake was studied with two different methods: either by spectrophotometric measurements on the solutions after flocculation or by potentiometric measurements with amalgam electrodes in order to follow the entire complex formation. The metal–biopolymer interaction in 0.1M NaClO4 is practically the same as when no neutral salt is added. The metal uptake is dependent on pH and is selective. A reversible process suitable for metal complexation is described.
Continuous production of ethanol by yeast “immobilized” in a membrane‐contained fermentor
Authors: Kyung Kyu H. , Gerhardt Philipp
Published: December 2004

A dialysate‐feed, immobilized‐cell dialysis continuous fermentation system was investigated as a method of relieving product inhibition in the conversion of glucose to ethanol by cells of Saccharomyces cerevisiae ATCC 4126. The substrate was fed into a continuous dialysate circuit and then into a batch fermentor circuit via diffusion through the microporous membranes of an intermediate dialyzer. Simultaneously, product was withdrawn from the fermentor circuit through the dialyzer membranes into the dialysate circuit and out in the effluent. Since the fermentor was operated without an effluent, the cells essentially were immobilized and converted substrate to product by maintenance metabolism. Contrary to prior results with this novel system for the continuous fermentation of lactose to lactate by lactobacillus cells, a steady state of yeast cells in the fermentor did not occur initially but was obtained by the depletion of medium nitrogen and the prevention of cell breakage, although the substrate and product concentrations then became unsteady. The inherent advantages of the system was offset in the ethanol fermentation by relatively low productivity, which appeared to be limited by membrane permeability.
Semicontinuous and continuous production of penicillin‐G by Penicillium chrysogenum cells immobilized in κ‐carrageenan beads
Authors: Deo Y. M. , Gaucher G. M.
Published: December 2004

Conidia of Penicillium chrysogenum were immobilized in K‐carrageenan beads and then incubated in a growth‐supporting medium to yield a penicillin producing immobilized cell mass. These in situ grown immobilized cells were used for the semicontinuous (replacement cultures)and continuous (fluidized bioreactor culture) production of penicillin‐G. When periodically replaced into a minimal production medium, immobilized cells exhibited a half‐life for penicillin production which was ninefold greater than that exhibited by free cells. The half‐life of penicillin production and the yield of penicillin from glucose in such a replacement culture were greatly affected by the frequency of replacement and by the production medium's pH and concentration of glucose, phosphate, and trace metal nutrients. A penicillin‐producing continuous flow bioreactor (150 mL), employing immobilized cells, was operated for up to 16 days. The best specific penicillin productivity (1.2 mg/g cells/h)yield from glucose (7.0 mg/g glucose) and half‐life of production (15 days) were obtained when the feed medium contained 10 g/L of glucose, the pH was maintained at 7.0, the relative dissolved oxygen concentration was ca. 40%; and the residence time was 20 h.
Preparation and characterization of a soluble dextran α1 proteinase inhibitor complex
Authors: Mitra G. , Coan M. H.
Published: December 2004

Purified human α1 proteinase inhibitor, a plasma glycoprotein with a molecular weight of 5.3 × 104 daltons and a major serine protease inhibitor has been covalently coupled to dextrans with molecular weights of 1.77 × 104 and 1.03 × 104 daltons. The coupled conjugates were soluble in aqueous medium and stable up to 6 months at +5°C. Increased moles of dextran/mole protein ratio during coupling resulted in progressive decreases of inhibitory capacity, immunogenicity, and the association constant (kassoc) between the enzyme and the inhibitor. Compared to the native protein, the soluble conjugates showed improved stability at pH 3.0 and heat stability at 60°C. At 60°C, no loss of inhibitory capacity has been seen up to 60 min for the conjugates during which time the native protein lost greater than 90% of its inhibitory capacity. The presence of antioxidant catalase was needed to prevent oxidative degradation by hydrogen peroxide.
Dephenolization of industrial wastewaters catalyzed by polyphenol oxidase
Authors: Atlow Stuart C. , Bonadonna‐Aparo Lucia , Klibanov Alexander M.
Published: December 2004

A new enzymatic method for the removal of phenols from industrial aqueous effluents has been developed. The method uses the enzyme polyphenol oxidase which oxidizes phenols to the corresponding o‐quinones; the latter then undergo a nonenzymatic polymerization to form water‐insoluble aggregates. Therefore, the enzyme in effect precipitates phenols from water. Polyphenol oxidase has been found to nearly completely dephenolize solutions of phenol in the concentration range from 0.01 to 1.0 g/L. The enzymatic treatment is effective over a wide range of pH and temperature; a crude preparation of polyphenol oxidase (mushroom extract) is as effective as a purified, commercially obtained version. In addition to phenol itself, polyphenol oxidase is capable of precipitating from water a number of substituted phenols (cresols, chlorophenols, naphthol, etc.). Also, even pollutants which are unreactive towards polyphenol oxidase can be enzymatically coprecipitated with phenol. The polyphenol oxidase treatment has been successfully used to dephenolize two different real industrial waste‐water samples, from a plant producing triarylphosphates and from a coke plant. The advantage of the polyphenol oxidase dephenolization over the peroxidase‐catalyzed one previously elaborated by the authors is that the former enzyme uses molecular oxygen instead of costly hydrogen peroxide (used by peroxidase) as an oxidant.
Use of catalase from Escherichia coli in model experiments for oxygen supply of microorganisms with hydrogen peroxide
Authors: Nies D. , Schlegel H. G.
Published: December 2004

A catalase has been purified from aerobically grown Escherichia coli K12. The enzyme exhibits unorthodox properties compared with catalyse from bovine liver and seems to be identical to hydroperoxidase II from E. coli. A mathematical model is presented which makes it possible to calculate the steady‐state concentration of hydrogen peroxide in an open system. The model has been verified experimentally. It has been shown that the catalase from E. coli is better suited than the bovine liver enzyme for oxygen supply to cell suspensions using hydrogen peroxide.
The HCH‐1 model of enzymatic cellulose hydrolysis
Authors: Holtzapple Mark T. , Caram Hugo S. , Humphrey Arthur E.
Published: December 2004

Solka Floc BW200 was enzymatically hydrolyzed in a batch reactor using a commercial cellulase preparation. A total of 50 different hydrolysis conditions were run within a 10‐fold range in enzyme concentration and a 30‐fold range in cellulose concentration. The data were evaluated in three ways using five different models. Previous literature models were not as successful in correlating the data as the HCH‐1 Model derived in this work.