bluuebunny/crossref_metadata_2025_split huggingface dataset:
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

AbstractA 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

AbstractThe 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

AbstractZymomonas 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

AbstractConsiderable 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

AbstractCell 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

AbstractIt 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

AbstractThe 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

AbstractThe 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

AbstractA 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

AbstractTwo 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

AbstractCellobiase 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

AbstractThe 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

AbstractStudies 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

AbstractBased 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

AbstractA 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

AbstractThe 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

AbstractThe 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

AbstractParticles 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

AbstractA 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

AbstractThis 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

AbstractWheat 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.