bluuebunny/crossref_metadata_2025 huggingface dataset:
Hollow‐fiber membrane bioreactors using immobilized E. coli for protein synthesis
Authors: Inloes Douglas S. , Smith William J. , Taylor Dean P. , Cohen Stanley N. , Michaels Alan S. , Robertson Channing R.
Published: December 2004

Actively growing Escherichia coli C600(pBR322), immobilized within the macroporous matrix of asymmetric‐wall hollow‐fiber membranes, has been propagated to extremely high densities, typically more than 1012 cells/mL of accessible void volume, in some regions cells accounting for nearly 100% of the available macrovoid volume forming a tissue‐like mass. Production rates of β‐lactamase, an enzyme used as an indicator of the culture's biosynthetic potential, remained at high and relatively stable levels for more than three weeks of continuous operation, and effluent supernatant enzyme activities attained 25% of the accumulated level measured in a 24‐h shaker‐flask culture. Based on the accessible void volume within the fiber wall, the β‐lactamase productivity was independent of the specific asymmetric membrane used. On a per cell basis, however, cells cultured using hollow‐fiber membranes were only 10% as productive as those in the shaker‐flask culture, possibly due to the high packing density or culture aging. By contrast, the hollow‐fiber bioreactor was 100 times more productive than the shaker‐flask culture on a reactor‐volume basis, primarily as a consequence of the high cell densities. Reactor productivity was dependent on the number of cells in the reactor, suggesting that reactor performance was kinetically controlled and not mass transport limited.
Cultural properties and mass–energy balances in methanol fermentation by Methylomonas methanolovorans
Authors: Amano Yoshifumi , Takada Nobuo , Sawada Hidekazu , Sakuma Hideo , Terui Gyozo
Published: December 2004

The cultural properties of an obligate methanol utilizer, Methylomonas methanolovorans, were investigated in batch and continuous cultures, and the problems of mass‐energy balances were examined. Among the culture data, an exponential increase of growth lag with increased methanol concentration, as well as the inhibition kinetics in the relation between attainable maximum specific growth rate (μm ≦ 0.52) and methanol concentration are of interest. In the latter case, the inhibition constant (Ki) and the index number were 40 g/L, and 3 (dimensionless), respectively. The maximum yield coefficient (Y) in both batch and chemostat cultures was around 0.52. An analysis of the behavior of respiratory activity (Qo2) in response to the dissolved oxygen concentration (DO) indicated that the oxygen‐terminal entity should be regarded as a single one with a saturation constant for DO of 32 μg/L (1.1 × 10−6M). Chemostat data showed that the saturation constant for methanol is as low as 2.2 mg/L or 7 × 10minus;5M. A linear relationship was observed between the respiratory activity (mol O2g−1h−1) and the specific growth rate (μ i h−1), with the relationship Qo2 = 0.0504μ + 0.00112. The theory of mass and energy balances used by Roels has been reformed to give useful relationships between RQ or the cell yield and μ. In the case of M. methanolovorans, the relations can be greatly simplified since the influence of metabolic by‐product formation was negligible. Experimental RQ values (theoretical values for Y = 0.52 and 0.445) at varying μ‐values were compared with theoretical ones; despite considerable fluctuations, the results were regarded to conform with theory. By use of mass balance equations and enthalpy data of known compounds, the heat evolution in methanol fermentation was estimated indirectly to be 612 kcal/100 g biomass formed. The YATP problems are also discussed.
Mode of uptake of insoluble solid substrates by microorganisms. I: Sterol uptake by an arthrobacter species
Authors: Goswami P. C. , Singh H. D. , Bhagat S. D. , Baruah J. N.
Published: December 2004

The mode of uptake of sterols, which are nearly insoluble in water by an Arthrobacter species, was studied on the basis of substrate transfer via the aqueous phase (solubilization/pseudosolubilization) and through direct contact with sterol particles. Growth of the organism, on stero powder was predominantly in nonlogarithmic in character, indicating a possible limitation of substrate transfer. Soluble sterol was shown to be the preferential form of the substrate for assimilation by the organism. Evidence was obtained for increased solubilizition of β‐sitosterol and cholesterol during microbial growth on these substrates. But the rate of solubilization of β‐sitosterol (3.06 mg L−1 h−1) was too inadequate to account for the observed substrate uptake rare (107 mg L−1 h−1) during growth. A cholesterol solubilization rate of 44 mg L−1 h−1 could, however, account to an appreciable extent for the observed cholesterol uptake rate of 140 mg L−1 h−1 during growth. Increasing attachement of cells to sterol particles during growth was observed by microscopic examination, indicating that growth may take place over the surface of sterol particles. By using the synthetic surfactant HYOXYD AAO (alkyl aryl polyglycol ether), which prevented attachment of cells to sterol particles without affecting the metabolic integrity of the cells, it was shown that growth indeed took place predominantly on the surface of the sterol particles. Increased generation of finer particles of sterol, which provides increased substrate surface area during growth, was demonstrated. It was concluded that with β‐sitosterol, growth takes place almost entirely by attachement, whereas with cholesterol, about 30% of the growth take place on solubilized substrate and the rest through attachament.
Mode of uptake of insoluble solid substrates by microorganisms. II: Uptake of solid n‐alkanes by yeast and bacterial species
Authors: Cameotra Swaranjit S. , Singh H. D. , Hazarika A. K. , Baruah J. N.
Published: December 2004

Using two species of yeast and one of bacterium, evidence has ben obtained which indicates that the microbial uptake of solid alkane powders occurs primarily through a substrate solubilization mechanism. EDTA, a strong inhibitor of hydrocarbon solubilization by the cells, inhibited the growth of these organisms on alkane powder; the inhibition could be removed vai a supply of artificially solubilized alkane. One of the yeast strians, which was a mutant incapable of growing on solid alkane powder and liquid alkane, could grow very well on artifically solubilized alkanes. It was demonstrated that the solid alkane solubilization rate during microbial growth could satisfactorily account for the maximal alkane uptake rate actully observed during growth. The specificity of solubilization for the solid alkane used as the growth substrate was demonstrated.
Effects of temperature shift on growth rate of Escherichia coli BB at lower glucose concentration
Authors: Chohji Tetsuji , Sawada Tatsuro , Kuno Sigeru
Published: December 2004

Although a shift in nutritinal conditins brings about transient unbalanced growth in normally grown Escherichia coli, a shift in temperature without changing the nutritional conditions results in immediate adaptation to the new conditions. However, when a medium contained an insufficient amount of nutrient, such as glucose, a temperature shift caused a lag time in temperature shiftup was primarily determined by the postshift temperature. These situatins were quite similar to those observed in nutrient shiftup, but a growth profile during the lag time was more distorted than that found in the nutrient shiftup. The transient unbalanced growth appeared to be caused by a difference in physiological states of bacteria, as expressed by macromolecule content per cell characterized by the pre and postshift environments, and was capable of expressing theoretically its profile and duration according to the model of Cooper and Helmstetter. On the other hand, the shiftdown in temperature in the presence of a limiting concentration of glucose caused extraordinarily long lag time, and transient cessation of cell division during that period. This response was unable to explain by the Cooper and Helmstetter model. In contrast to the temperature shiftup, the duration of lag time in the shiftdown was expresed as functions of the poshift temperature and the difference in physiological states of the pre‐ and postshift environments.
Explosive pretreatment of lignocellulosic residues with high‐pressure carbon dioxide for the production of fermentation substrates
Authors: Puri V. P. , Mamers H.
Published: December 2004

A new pretreatment technique has been developed in which the lignocellulosic material is subjected to the action of steam and high‐pressure carbon dioxide before being explosively discharged through a defibrating nozzle of novel design. Operating at 200°C and gas pressures in the range of 3.45–13.8 MPa, exploded products with maximum in vitro cellulase digestibilities of 81, 78, and 75% were obtained from wheat straw, bagasse, and Eucalyptus regnans woodchips, respectively. The treatment times required to obtain substrates of maximum digestibility were 5 min for wheat straw and bagasse and 15 min for E. regnans. Analysis of the exploded products indicated that the pretreatment had substantially removed and solubilized the hemicellulose fraction of the feed materials, giving an autohydrolysis liquor rich in xylose and a fibrous residue primarily composed of α‐cellulose and lignin. The fibrous residue was readily amenable to cellulase hydrolysis, with saccharification being completed within 48 h. The theoretical energy demand for gas compression in the pretreatment process has been calculated at 11 k Wh/ton raw material when the digester is operated at 3.45 MPa and a packing density of 250 kg raw material/m3 digester volume.
Methane production using whole and screened dairy manure in conventional and fixed‐film reactors
Authors: Liao P. H. , Lo K. V.
Published: December 2004

The technical feasibility of adopting the fixed‐film reactor concept for biogas production from screened dairy manure was investigated. The methane production capability of laboratory‐scale 4‐L anaerobic reactors (conventional and fixed‐film) receiving screened dairy manure and operated at 35°C was compared. Dairy manure filtrate with 4.4% total solids (TS) and 3.4% volatile solids (VS) (average value) was prepared from 1:1 manure–water slurry. The feed material was added intermittently at loading rates ranging from 2.34 to 25 and 2.25 to 785 g VS/L d, respectively, for the conventional and fixed‐film reactors. Maximum methane production rate (L CH4/L d) for the conventional reactor was 0.63 L CH4/L d achieved at a 6‐day hydraulic retention time (HRT). For the fixed‐film reactor the maximum production rate was 3.53 L CH4/L d when operated at a loading rate of 262 g VS/L d (3 h HRT). The fixed‐film reactor was capable of sustaining a loading of 785 g VS/L d (1 h HRT). The fixed‐film reactor performed much better than the conventional reactors. These results indicate that a large reduction of required reactor volume is possible through application of a fixed‐film concept combined with a liquid–solid separation pretreatment of dairy manure.
Preparation and characterization of immobilized growing cells of Zymomonas mobilis for ethanol production
Authors: Jain V. K. , Toran‐Diaz I. , Barrati J.
Published: December 2004

Zymomonas mobilis cells were entrapped in K. carrageenan. Growth was observed with the immobilized cell preparation. The kinetic and yield parameters for the conversion of fructose to ethanol were nearly identical to free cells. The same preparation of immobilized cells was used in six repeated batch runs and at the end sixthbatch fructose was converted to ethanol more rapidly and efficiently with ethanol productivity of 14 g/L h and 96% conversion of fructose. The effect of high fructose and ethanol levels on specific fructose uptake rate and ethanol productivity was studied and quantitatively analyzed.
Induction of NADPH‐linked D‐xylose reductase and NAD‐linked xylitol dehydrogenase activities in Pachysolen tannophilus by D‐xylose, L‐arabinose, or D‐galactose
Authors: Bolen P. L. , Detroy R. W.
Published: December 2004

Considerable interest in the D‐xylose catabolic pathway of Pachysolen tannophilus has arisen from the discovery that this yeast is capable of fermenting D‐xylose to ethanol. In this organism D‐xylose appears to be catabolized through xylitol to D‐xylulose. NADPH‐linked D‐xylose reductase is primarily responsible for the conversion of D‐xylose to xylitol, while NAD‐linked xylitol dehydrogenase is primarily responsible for the subsequent conversion of xylitol to D‐xylulose. Both enzyme activities are readily detectable in cell‐free extracts of P. tannophilus grown in medium containing D‐xylose, L‐arabinose, or D‐galactose and appear to be inducible since extracts prepared from cells growth in media containing other carbon sources have only negligible activities, if any. Like D‐xylose, L‐arabinose and D‐galactose were found to serve as substrates for NADPH‐linked reactions in extracts of cells grown in medium containing D‐xylose, L‐arabinose, or D‐galactose. These L‐arabinose and D‐galactose NADPH‐linked activities also appear to be inducible, since only minor activity with L‐arabinose and no activity with D‐galactose is detected in extracts of cells grown in D‐glucose medium. The NADPH‐linked activities obtained with these three sugars may result from the actions of distinctly different enzymes or from a single aldose reductase acting on different substrates. High‐performance liquid chromatography and gas‐liquid chromatography of in vitro D‐xylose, L‐arabinose, and D‐galactose NADPH‐linked reactions confirmed xylitol, L‐arabitol, and galactitol as the respective conversion products of these sugars. Unlike xylitol, however, neither L‐arabitol nor galactitol would support comparable NAD‐linked reaction(s) in cellfree extracts of induced P. tannophilus. Thus, the metabolic pathway of D‐xylose diverges from those of L‐arabinose or D‐galactose following formation of the pentitol.
Effects of phosphate, glucose, and ammonium on cell growth and lincomycin production by Streptomyces lincolnensis in chemically defined media
Authors: Young M. D. , Kempe L. L. , Bader F. G.
Published: December 2004

Cell growth and lincomycin production were measured in batch cultures of Streptomyces lincolnensis in chemically defined media. In these fermentations the specific rate of antibiotic production was maximal during growth and always declined at the end of the growth phase. It was found that both phosphate and ammonium salts, while required for cell growth, had negative effects on antibiotic production. By increasing the concentration of magnesium sulfate, it was possible to increase both the production rates and final titers of lincomycin. The mechanism for this effect was found to be the reduction of soluble phosphate in the medium through the precipitation of ammonium magnesium phosphate. Lincomycin production rates were not inhibited by glucose at concentrations of up to 30 g/L.
Simultaneous saccharification and fermentation of cellulose: Effect of ethanol on enzymatic saccharification of cellulose
Authors: Ooshima Hiroshi , Ishitani Yohsuke , Harano Yoshio
Published: December 2004

It was confirmed that simultaneous saccharification and fermentation are effective for accelerating enzymatic saccharification of cellulose. In this work, the effects of ethanol on the saccharification of tissue paper by Trichoderma cellulase (Meicelase CEPB) have been investigated. The following results were obtained. (1) Saccharification was inhibited by at least 0.2M ethanol. (2) Less than 4M ethanol did not affect the enzymatic activities of β‐glucosidase and endoglucanase (Cx) at all. The thermal stability of endoglucanase was not also varied by ethanol. (3) It is suggested that ethanol depresses the adsorption of exoglucanase on cellulose. (4) The rate expression of saccharification of cellulose in the presense of ethanol is proposed. (5) The inhibititory effect of ethanol was found to become more significant in the later stages of the reaction than just the initial stage.
A standard formula for the determination of the initial rate of hydrolysis of carboxymethylcellulose
Authors: Poulsen O. M. , Petersen L. W.
Published: December 2004

The integrated rate equation of Huang, originally used to describe the hydrolysis of insoluble acid treated cellulose, is shown equally applicable in describing the hydrolysis of carboxymethylcellulose (CMC) using a dilution series of Cellulomonas sp. ATCC 21399 crude cellulase as enzyme preparation. Interpretation of the progress curves of hydrolysis of CMC according to the integrated rate equation is used to calculate a standard formula for the conversion of the rate of hydrolysis into the initial velocity of hydrolysis. The validity of the standard formula is tested, using enzyme preparations from Cellulomonas grown under varied conditions, and enzyme preparations containing purified endoglucanases from Cellulomonas.
The response of a nitrogen‐limited chemostat culture of Escherichia coli B/r to pH and dilution rate steps
Authors: Goochee Charles F. , Hatch Randolph T. , Cadman Theodore W.
Published: December 2004

The effects of four pH steps and one dilution rate step are described for an ammonia–nitrogen‐limited continuous culture of Escherichia coli B/r. Two of the pH steps, 6.06–5.49 and 5.96–5.60, led to prolonged transients in both cell density and rate‐limiting nutrient concentration. The other two pH steps, 6.20–5.96 and 5.60–6.20, had almost no effect on the culture. The dilution rate step led to a sharp transition in the steady‐state external pyruvate concentration. Monitoring of the external pyruvate concentration for the pH 5.96–5.60 step revealed that the transient phase continued long after the cell density and rate‐limiting nutrient concentration returned to steady‐state values. The implications for industrial and laboratory fermentations are discussed.
Novel process for the production of cellulolytic enzymes
Authors: Cauchon Nicole , Leduy Anh
Published: December 2004

A novel process for the production of extracellular carboxymethylcellulase (CMCase) and xylanase by fermentation under nonaseptic or nonsterile conditions is described. The fermentation process is carried out under very acidic conditions of pH 2.0 by using a acidophilic cellulolytic fungus. Microbial contamination is avoided or minimized to an insignificant level under this acid pH condition. The culture medium for this production consists of a carbon source from cellulosics or lignocellulosics, such as Na–CMC, xylan, Avicel cellulose, cellulose powder, α‐cellulose, sawdust, etc., or a mixture of the forementioned together with simple ingredients such as (NH4)2SO4, K2HPO4, MgSO4 and NaNO3. The fermentation is carried out at room temperature (28–30°C), under aerobic conditions, and without controlling the pH. The CMCase and xylanase produced are stable under very simple storage conditions, such as in the fresh culture medium not containing the substrate for a period of 3 days, at any temperature from 0 to 30°C. These extracellular enzymes have an optimum pH around 3, with the best range of pH from 2.0 to 3.6, for any temperature between 15 and 60°C. The optimum temperatures are 55°C for CMCase activity and 25–50°C for xylanase activity, at any pH between 2.0 and 5.2. The apparent Michaelis constants Km are 2.6 and 1.5 mg/mL for CMCase and xylanase of the culture filtrate, respectively.
The effect of growth temperature on the bioenergetics of photosynthetic algal cultures
Authors: Lee Yuan‐Kun , Tan Hai‐Meng , Hew Choy‐Sin
Published: December 2004

Two photosynthetic algal cultures, one Chlorella vulgaris, and the other a Chlorogonium sp., were cultured under light limitations in chemostats. The effects of growth temperature on their energy yield and maintenance energy requirement were studied. It was observed that a lowering in temperature resulted in a lower maximum growth yield from the light energy, YG. This was attributed to two reasons. First, at low temperatures there was a change in the algal cell composition with more energy being expended to synthesize a higher biomass protein content. Secondly, at low temperatures, a cyanide‐resistant respiratory pathway became operative which led to a decrease in the number of ATP being generated. The maintenance energy coefficient was a function of temperature increasing with decreasing temperature. This might reflect energy wastage by the cell at low temperatures. The maximum specific growth rate dropped with decreasing temperature, and can be described by an Arrhenius type rate‐temperature model up to the optimal temperature for growth; i.e., activation energy remained constant.
Immobilization of a soluble chemically thermostabilized enzyme
Authors: Lenders J.‐P. , Germain P. , Crichton R. R.
Published: December 2004

Cellobiase was coupled to a dialdehyde dextran by reductive alkylation in the presence of sodium cyanoborohydride. The resulting conjugate, obtained without loss of enzymic activity, presents properties of thermoresistance largely superior to those of native enzyme: the rate of inactivation is reduced compared to that of native enzyme and its optimal temperature of activity is 70–75°C instead of 65°C. Finally the conjugate presents increased longevity when subjected to experiments of operational stability; its hydrolytic activity is maintained at 60°C in a 10% (w/v) cellobiose solution for more than 100 h whereas the native enzyme is inactivated after 45 h. The cellobiase–dextran conjugate was immobilized by covalent coupling on aminated silica by reductive alkylation in the presence of NaBH3CN. The characteristics of thermoresistance of this stabilized and immobilized conjugate were studied and compared to those of a preparation of native cellobiase immobilized on a silica support activated with glutaraldehyde. Analysis of the thermoresistance of these two cellobiase preparations clearly shows that immobilization has maintained and even enhanced their properties. In particular, the operational stability, measured at 68°C on 10% (w/v) cellobiose shows an increased longevity of the stabilized and immobilized enzyme for 120 h compared to 60 h for the native immobilized enzyme. Two successive incubations of these cellobiase derivatives show that it is possible to obtain 2.5 times more glucose with the stabilized‐immobilized enzyme than with the immobilized preparation. The procedure described above enables us to prepare a thermostabilized immobilized cellobiase.
Preparation of cibacron blue F3G‐A (polyethylene glycol) in large scale for use in affinity partitioning
Authors: Johansson Göte , Joelsson Monica
Published: December 2004

The reaction parameters for preparation of Cibacron Blue F3G‐A polyethylene glycol have been studied, including temperature, concentration of reactants, and addition of neutral salt (Na2SO4) as well as ethanol. The yield of dypolymer is strongly dependent on temperature and time of reaction. Preparation in large scale has been done under optimal conditions binding more than 30% of the dye to polyethylene glycol in a low‐cost procedure. The effectiveness of this dye‐polymer for use in liquid–liquid extraction of enzymes is demonstrated by partition of glucose 6‐phosphate dehydrogenase and phosphofructokinase when an extract of baker's yeast is included in a dextran–polyethylene glycol–water two‐phase system.
Enzymic saccharification of pretreated wheat straw
Authors: Vallander Lars , Eriksson Karl‐Erik
Published: December 2004

Studies of pretreatment of wheat and its subsequent saccharification by Trichoderma reesei cellulases are reported. Steam explosion was found to be the most effective of the pretreatment methods tested. Data are presented describing the effect of enzyme and substrate concentration on the rate and degree of hydrolysis. Significant inhibition of the cellulases was observed when sugar concentrations were 6% or higher. This inhibition increased when glucose and ethanol were present simultaneously. Adsorption of enzymes to the substrate was followed during a 24‐h hydrolysis period. An initial rapid and extensive adsorption occurred, followed by a short desorption period that was followed in turn by a further increased adsorption peaking after 3 h. Intermediate removal of hydrolysate, particularly in combination with a second addition of enzyme, clearly improved the yield of saccharification compared to an uninterrupted hydrolysis over a 24‐h period. Thus, a 74% yield of reducing sugars was obtained. Furthermore, an increase in the amount of recoverable enzymes was observed under these conditions. Evidence is presented that suggests that a countercurrent technique, whereby free enzymes in recovered hydrolysate are adsorbed onto new substrate, may provide a means of recirculating dissolved enzymes.
Improved performance with multiple fermentors for repeated batch cultivation for non‐growth‐associated products
Authors: Shimizu Kazuyuki , Kobayashi Takeshi , Nagara Akira , Matsubara Masakazu
Published: December 2004

Based on batch cultivation data for the production of L‐glutamic acid from glucose, a comparative evaluation was made for repeated batch cultivations using one and more fermentors. The problem was formulated as maximizing the productivity of metabolic product with the specified conversion with respect to the cell age and the volume fraction used as seed for the subsequent repeated batch cultivation. Simulations were carried out with the assumption of no lag in product formation for the cases where the total operation time was specified as 200 h with reproducible batch cultivation cycles. The product production was assumed to be solely a function of product concentration. The computation results show the advantage of using more than one fermentor from the viewpoints of productivity and conversion, which will apply in general to non‐growth‐associated product production with delay time. In particular, three fermentors are recommended for the production of L‐glutamic acid chosen as an example in this article.
On‐line optimal control for fed‐batch culture of baker's yeast production
Authors: Wu Wen‐Teng , Chen Kuo‐Cheng , Chiou Hung‐Wen
Published: December 2004

A method of on‐line optimal control for fed‐batch culture of bakers yeast production is proposed. The feed rate is taken as the control variable. The specific growth rate of the yeast is the output variable and is determined from the balance equation of oxygen. A moving model is obtained by using the data from the feed rate and the specific growth rate. Based on the moving model, an optimal feed rate for fed‐batch culture is then achieved.
Continuous alcohol fermentation in an immobilized cell rotating disk reactor
Authors: Del Borghi M. , Converti A. , Parisi F. , Ferraiolo G.
Published: December 2004

The increasing interest in alcohol fermentation over these last years because of the energy crisis has been demonstrated by an increase in scientific research. After a brief analysis of the main results of the literature in the field of alcohol fermentation reactors, the use of a new type of immobilized cell reactor [the rotating biological surface (RBS) reactor] was studied. As is well known, the RBS reactor is a form of fixed‐film reactor and can be described as a dynamic trickling filter. Our experimental apparatus employed a spongy material to trap the yeast cells on the disks. The results of fermentations carried out in the RBS reactor working in batch, in continuous with cell support, and in continuous without cell support have been presented in order to compare the different productivities and to assess the performance of the RBS immobilized cell reactor. An ethanol productivity of 7.1 g/L h was achieved in the RBS‐ICR at a dilution rate of 0.3 h−1, 2.5 times higher than the maximum productivity obtained in the RBS reactor without support at a lower dilution rate. The adoption of a spongy material as a cell immobilizer, combined with the use of the RBS reactor, enhances the particular advantages of both systems.
Estimation of available efficiency of microbial growth on methanol and ethanol
Authors: Minkevich I. G.
Published: December 2004

The balances of reductivity and high‐energy bonds (HEB) during microbial growth on glucose (a standard substrate), methanol, and ethanol are reported. Also, numerical values for the quantities of HEB formation in the respiratory metabolism, HEB consumption in the constructive metabolism, as well as in a number of the other intracellular processes are evaluated. Estimations of maximum cell yields by mass and energy are made during growth on methanol and ethanol with regard to peculiar features of different microbe metabolism.
The use of a hydrophobic resin as a product reservoir in steroid transformations
Authors: Saunders R. P. , Hardman R. , Cheetham P. S. J.
Published: December 2004

Particles of the hydrophobic resin polydimethylsiloxane were found to preferentially accumulate steriods on the basis of their hydrophobicity. Thus, the resin selectively sorped the steroid products resulting from the transformation of diosgenin by Nocardia rhodochrous, with the result that higher yields of the later biotransformation product, 1‐dehydrodiosgenone, and lower yields of the first product, diosgenone, were obtained than in the absence of resin. Furthermore, steroids accumulated by the resin were available for further biotransformation, so that a two‐step reaction forming androstenes from a crude extract of furostanol glycosides (obtained from fenugreek seed) could be carried out. The first step involves deglycosylation and is catalyzed by Fusarium solani. In the presence of resin the water‐insoluble diosgenin product becomes sorped to the resin and can be easily transferred to a second fermentation in which diosgenone, 1‐dehydrodiosgenone, and androstenes were formed by Mycobacterium phlei. These compounds were completely accumulated by the resin at the end of the fermentation. This procedure is logistically more convenient than the conventional chemical process and illustrates the potential of biotechnological processes in which simultaneous reaction, product isolation, and product purification occur.
Hyphomicrobium bacterial electrode for determination of monomethyl sulfate
Authors: Schär Hans‐Peter , Ghisalba Oreste
Published: December 2004

A biosensor consisting of physically entrapped monomethyl sulfate (methyl sulfate) degrading bacterium, Hyphomicrobium MS 219, and a combined glass electrode has been developed for the determination of methyl sulfate. The response of the bacterial electrode is linear between 2.5 × 10−2M and 6.3 × 10−1M methyl sulfate with an effective response to concentrations as low as 10−3M and as high as 1M methyl sulfate. The probe has an average slope of 8 mV per concentration decade over the linear range. Response times vary from 5 min in the linear range to 30 min at the detection limit. The sensor has a lifetime of at least 1 week and shows high selectivity to methyl sulfate in the absence of other growth substrates.
A direct fuel cell for the production of electricity from lignin
Authors: Weetal Howard H. , Forsyth Barbara D. , Hertl William
Published: December 2004

This report describes the use of an anthraquinone mediated fuel cell for the direct production of electrical energy from sulfonated lignin and Kraft Black Liquor. The cell produces the equivalent of 1 kWh for each 2–3 lb sulfonated lignin and 5–8 lb black liquor combustibles. In the case of the sulfonated lignin, chain session occurs during the oxidation process, reducing the molecular weight from ca. 2 × 104 to less than 1000 D.
Products of alkaline peroxide attack on wheat straw, oak, and kenaf
Authors: Abbott Thomas , Peterson Robert
Published: December 2004

Wheat straw, oak, and kenaf were partially delignified by treatment with hydrogen peroxide at pH 11.0, and the water‐soluble degradation products were characterized. Forty to sixty percent of the solubilized products were larger than 1000 molecular weight (MW), as determined by membrane ultrafiltration. Lignin degradation products in the low‐molecular‐weight fraction (<1000) consisted primarily of aromatic and aliphatic carboxylic acids.
Production of glycerol by hansenula anomala
Authors: Parekh S. R. , Pandey N. K.
Published: December 2004

Production of glycerol by Hansenula anomala in molasses–corn steep liquor based media was studied. The accumulation and yield of glycerol was dependent on the medium composition and aeration rate; pH control did not affect the yield. Intermittent addition of sugar during fermentation resulted in significant increase in production of glycerol.
An automatic method for on‐line estimation of the photosynthetic rate in open algal ponds
Authors: Ben‐Yaakov Sam , Guterman Hugo , Vonshak Avigad , Richmond Amos
Published: December 2004

An analytical model for dissolved oxygen concentration in an algal minipond was used to develop a new method for estimating, on‐line, the net O2 production rate (OPR) of the biological process. The method was tested experimentally and was found to provide crucial information on the vitality of the biological process and to provide an early warning of a possible forthcoming collapse of the ecosystern. It is suggested that the newly developed model and measurement method could provide investigators with useful tools for optimization of algal cultivation in the laboratory and plant.
Comparisons between cellulase production by Aspergillus fumigatus in agitated vessels and in an air‐lift fermentor
Authors: Wase D. A. John , McManamey William J. , Raymahasay Sugat , Vaid Aloke K.
Published: December 2004

Aspergillus fumigatus was cultured in disc‐turbine‐agitated vessels and in an air‐lift fermentor. In the agitated vessels the yield of cellulase was reduced when the agitation rate was increased, although extracellular protein levels rose. The enzyme complex itself was shown to be exceptionally stable under conditions similar to those in the agitated vessels, so probably shear damage to the mycelium had occurred, liberating intracellular contents. These appeared to contain an inhibitor that could be removed by fabricated inorganic protein absorbents, such as kieselguhr and alumina. However, the inhibitor was not likely to be protease, since only relatively low levels could be detected and its identity has not been established. The use of an air‐lift fermentor avoided the shear effects due to use of the disc turbine agitator in the conventional fermentors, and yields of enzyme were then found to increase by about 20%, maximum yields being obtained at maximum KLa values.
A growth model for the continuous microbiological leaching of a zinc sulfide concentrate by Thiobacillus ferrooxidans
Authors: Sanmugasunderam V. , Branion R. M. R. , Duncan D. W.
Published: December 2004

The leaching of a zinc sulfide concentrate by Thiobacillus ferrooxidans was investigated in continuous stirred tank reactors. A mathematical model for the growth of T. ferrooxidans on this solid substrate is presented and tested. Experimental leaching studies were done using two reactors in series with and without recycle of solids from the outlet of the first reactor back to its inlet. The proposed model fits the authors' experimental data well. However, comparison of the parameters calculated with those calculated from the data of others showed that a wide variation can exist; thus, the parameters seem to depend on the nature of the substrate. The area occupied on the sulfide surface by a bacterium was found to be 5.4 μm2. The calculated maximum specific growth rates ranged from 0.20 to 0.31 h−1, and these values were dependent on whether they were observed in the first or second of the two reactors in series.
Invertase activity of intact cells of Saccharomyces cerevisiae growing on sugar cane molasses. I. Steady‐state continuous culture tests
Authors: Vitolo Michele , Vairo Marina L. R. , Borzani Walter
Published: December 2004

During the steady‐state continuous culture of Saccharomyces cerevisiae on sugar cane blackstrap molasses under different experimental conditions, oscillatory variations of the invertase activity of the intact yeast cells were observed. The continuous morphological changes of the cells wall and of the periplasmic space affecting the interaction between invertase and sucrose molecules could be responsible by the observed oscillatory phenomena. The average invertase activity at the steady state is linearly correlated to the cell's growth rate.
Biological treatment specific for an industrial wastewater containing s‐triazines
Authors: Hogrefe W. , Grossenbacher H. , Cook A. M. , Hütter R.
Published: December 2004

Mixed cultures of bacteria grew in medium containing real s‐triazine wastes as nitrogen source. About 80% of the s‐triazine waste could be degraded as determined by HPLC and by measurements of dissolved nitrogen. The culture required an added carbon source in order to degrade s‐triazines. A temperature optimum near 40°C was observed and a salt concentration above about 4% markedly retarded growth and the degradation of s‐triazines. This system was examined as a biological treatment for wastes from syntheses of s‐triazines.
Acetate inhibition of Pseudomonas putida
Authors: Fieschko John , Humphrey Arthur E.
Published: December 2004

To study the effect of acetate inhibition on the parameters of yield and maintenance for bacterial growth, Pseudomonas putida ATCC 23467 was grown in a minimal salts medium with acetate as the sole carbon source with limiting and with excess quantities of urea in the feed medium. The behavior of the chemostat cultures under sole acetate limitation results in low residual acetate present in the fermentation broth. These cultures can be described satisfactorily using the equation qs = D/Yg + m, i.e., the acetate is consumed only for growth and maintenance,. Those cultures in which urea was limiting or where urea was present in large excess contained significant amounts of residual acetate in the broth. For these cultures it was necessary to add a third term for acetate inhibition to the above expression.
Cellulase production by trichoderma harzianum in static and mixed solid‐state fermentation reactors under nonaseptic conditions
Authors: Deschamps F. , Giuliano C. , Asther M. , Huet M. C. , Roussos S.
Published: December 2004

Cellulase production from lignocellulosic materials was studied in solid‐state cultivation by both static and mixed techniques under nonaseptic conditions. The effects of fermentation conditions, such as moisture content, pH, temperature, and aeration, on cellulase production by Trichoderma harzianum using a mixture of wheat straw (80%) and bran (20%) were investigated. With a moisture content of 74% and a pH of 5.8., 18 IU filter paper activity and 198 IU endoglucanase activity/g initial substrate content were obtained in 66 h. The extension from static column cultivation to stirred tank reactor of 65 L capacity gave similar yields of cellulase.
Membrane separation of protein precipitates: Unstirred batch studies
Authors: Devereux N. , Hoare M. , Dunnill P.
Published: December 2004

The study examines the use of ultrafiltration and microfiltration membranes for concentrating isoelectric soya protein. Experiments with an unstirred batch cell indicate that the flux is limited by the protein which remains in solution after precipitation of the major proportion. The porosityof the precipitate cake formed is shown to be a second important factor. A significant improvement in flux can be obtained by using membranes which permit passage of the soluble protein and by increasing the precipitate particle size. The results are shown to be within the range predicted theoretically by the two limiting cases of a particulate model and a soluble protein model.
Ethanol fermentation by ionically adsorbed Zymomomas mobilis: Environmental effects on cell immobilization
Authors: Bar Raphael , Gainer John L. , Kirwan Donald J.
Published: December 2004

Batch ethanol fermentation by cells of Zymomomas mobilis ATCC 29191, ionically adsorbed on a DEAE‐cellulose ion exchanger, was investigated in a stirred fermentor. Adsorption isotherms in different media were determined and used to interpret the effects of the environment on cell immobilization. Other factors affecting cell immobilization during an actual fermentation were studied. Mechanical agitation was found to cause detachment of cells from the ion exchange particles. The results suggest that the amount of cells adsorbed during a fermentation process is different from that found from adsorption isotherm data. Consequently, application of equilibrium adsorption data to actual fermentations should be done with caution.
Growth of the extreme thermophile Sulfolobus acidocaldarius in a hyperbaric helium bioreactor
Authors: Sturm F. J. , Hurwitz S. A. , Deming J. W. , Kelly R. M.
Published: December 2004

The relationship between pressure and temperature as it affects microbial growth and metabolism has been examined only for a limited number of bacterial species. Because many newly‐discovered, extremely thermophilic bacteria have been isolated from pressurized environments, this relationship merits closer scrutiny. In this study, the extremely thermophilic bacterium, Sulfolobus acidocaldarius, was cultured successfully in a hyperbaric chamber containing helium and air enriched with 5% carbon dioxide. Over a pressure range of approximately 1–120 bar and a temperature range of 67–80°C, growth was achieved in a heterotrophic medium with the air mixture at partial pressures up to 3.5 bar. Helium was used to obtain the final, desired incubation pressure. No significant growth was noted above 80°C over the same range of hyperbaric pressures, or at 70°C when pressure was applied hydrostatically. Growth experiments conducted under hyperbaric conditions may provide a means to study these bacteria under simulated in situ conditions and simultaneously avoid the complications associated with hydrostatic experiments. Results indicate that hyperbaric helium bioreactors will be important in the study of extremely thermophilic bacteria that are isolated from pressurized environments.
Production of ethanol by immobilized Saccharomyces bayanus in an extractive fermentation system
Authors: Barros M. R. Aires , Cabral J. M. S. , Novais J. M.
Published: December 2004

An extractive fermentation system using immobilized yeast cells was developed to study the ethanol production at high sugar concentrations. Organic acids were used as extracting solvents of ethanol and their toxicity was tested in free and k‐carrageenan entrapped cell preparations. Immobilization seems to protect cells against solvent toxicity, when long‐chain organic acids, e.g., oleic acid, were used, probably due to steric and diffusional limitations, the free cells not being viable at high oleic acid concentrations. The entrapped cells also present a higher metabolic activity than their free counterparts at high glucose concentrations. A solution of 300 g/L of glucose was totally fermented by the immobilized yeast cells, which when free cannot normally convert more than 200 g/L. In situ recovery of ethanol by oleic acid in a batch immobilized cell system led to higher ethanol productivities and to the fermentation of 400 g/L, when an oleic acid/medium ratio of 5 was used.
Controlled expression and purification of human immune interferon from high‐cell‐density fermentations of Saccharomyces cerevisiae
Authors: Fieschko John C. , Egan Kevin M. , Ritch Thomas , Koski Raymond A. , Jones Matthew , Bitter Grant A.
Published: December 2004

Conditions for high‐cell‐density fermentations of Saccharomyces cerevisiae strains producing recombinant‐DNA‐derived proteins were established. Strains producing human immune interferon (IFN‐γ) from the constitutive PGK promoter failed to grow to high cell densities and exhibited low plasmid stability. Regulated expression of IFN‐γ was obtained in similar strains by employing a hybrid yeast GPD promoter that was subject to carbon source regulation due to the presence of regulatory DNA sequences from the yeast GAL 1,10 intergenic region. IFN‐γ expression programmed by this vector was low during growth on glucose and was induced by galactose. Previously defined fermentation conditions employing glucose as a carbon source were applied to this strain, resulting in high ceil densities with higher plasmid stability. Various methods of galactose induction of IFN‐γ expression in high‐cell‐density fermentations were investigated. Optimal conditions resulted in a 2000‐fold induction and production of 2 g IFN‐γ/L fermentation culture.
Characteristics of draft tube gas–liquid–solid fluidized‐bed bioreactor with immobilized living cells for phenol degradation
Authors: Fan Liang‐Shih , Fujie Koichi , Long Teng‐Rui , Tang W.‐T.
Published: December 2004

Biological phenol degradation in a draft tube gas‐liquid‐solid fluidized bed (DTFB) bioreactor containing a mixed culture immobilized on spherical activated carbon particles was investigated. The characteristics of biofilms including the biofilm dry density and thickness, the volumetric oxygen mass transfer coefficient, and the phenol removal rates under different operating conditions in the DTFB were evaluated. A phenol degradation rate as high as 18 kg/m3‐day with an effluent phenol concentration less than 1 g/m3 was achieved, signifying the high treatment efficiency of using a DTFB.
Purification and partial characterization of a cellodextrin glucohydrolase (β‐glucosidase) from Trichoderma reesei strain QM 9414
Authors: Schmid G. , Wandrey Ch.
Published: December 2004

A β‐glucosidase (E.C. 3.2.1.21) was isolated from the culture filtrate of fungus Trichoderma reesei QM 9414 grown in continuous culture with biomass retention. The crude extracellular enzyme preparation was fractionated by a three‐step purification procedure [chromatography on Fractogel HW‐55 (S) and Bio‐Gel A 0.5 plus final preparative isoelectric focusing] to yield three β‐glucosidases with isoelectric points at pH 8.4, 8.0, and 7.4. Only one enzyme (pi 8.4) met the stringent criterion of being homogeneous according to titration curve analysis. This enzyme was then characterized not to be a glycoprotein, although the native protein contained 35% carbohydrate (as glucose). It was found to have an apparent molar mass of 7 × 104 g/mol (SDS‐PAGE), exhibited its optimum activity towards cellobiose at pH 4.5 and 70°C (30 min test), and lost less than 3% activity at 50°C over a period of 7 h. The KM values towards cellobiose and p‐nitrophenyl‐β‐D‐glucopyranoside were determined to be 0.5mM and 0.3mM, respectively. The enzyme hydrolyzed cellodextrins (cellotriose to cellooctaose) by sequentially splitting off glucose units from the nonreducing end of the oligomers. The extent of the observed transfer reactions varied with the initial substrate concentration. No enzyme activity towards microcrystalline cellulose or carboxymethylcellulose could be detected. The classification of the enzyme as β‐glucosidase or exo‐β‐1,4‐glucan glucohydrolase is discussed with respect to the exhibited hydrolytic activities.
Growth of free and attached Thiobacillus ferrooxidans in ore suspension
Authors: Espejo Romilio T. , Ruiz Paulina
Published: December 2004

The growth of Thiobacillus ferrooxidans in a copper‐containing ore suspension incubated in shake flasks was studied by determining the number of colony‐forming units both in solution and attached to ore particles. The amounts of iron and copper released from the ore under experimental conditions were also determined. The total ferrous iron either released from the minerals or generated by reduction of the ferric iron in the minerals could account for the observed growth of bacteria in solution. Only a small fraction of the total colony‐forming units—about 500 per mg ore—was found to be associated with the ore particles throughout the experiments. However, the rapid development of these colonies when ore particles were plated suggested that they were produced by a number of bacteria associated with each ore particle. Accordingly, when the amount of bacteria attached to ore particles was determined by monitoring the formation of ferric iron in the plates, the percentage of the total activity associated with attached bacteria was found to be between 1 and 10%.