bluuebunny/crossref_metadata_2025_split huggingface dataset:
Formation of carotenoids by rhodotorula glutinis in whey ultrafiltrate
Authors: Frengova Ginka , Simova Emilina , Pavlova Konstantza , Beshkova Dora , Grigorova Drinka 
Published: December 2004

AbstractThe growth and carotenoid biosynthesis of the yeast Rhodotorula glutinis was studied by cocultivation with Lactobacillus helveticus in cheese ultrafiltrate containing 3.9% and 7.1% lactose. By growing this mixed culture in a 15‐L fermentor MBR AG (Switzerland) at an air flow rate of 0.5 L/L min and agitation at 220 rpm for 6 days, a total yield of carotenoids of 268 μg/g dry cells wasobtained. Carotenoids were formed almost parallel with the cell growth, anda maximum production was reached at an early stationary phase. A high‐performance liquid chromatographic system (HPLC) permitting simultaneous determination of major carotenoid pigments was used. The three main pigments (torularhodin, β‐carotene, and torulene) were formed in Rhodotorula glutinis, and reached a maximum concentration as follows: 182.0, 43.9, 23.0 μg,g dry cells. © 1994 John Wiley & Sons, Inc.
Efficient specific release of periplasmic proteins from Escherichia coli using temperature induction of cloned kil gene of pMB9
Authors: Steidler Lothar , Fiers Walter , Remaut Erik 
Published: December 2004

AbstractWe have cloned the kil gene of pMB9 under control of the tightly regulated leftward promoter (pL) of coliphage λ. Three types of plasmids were constructed. In all cases the activity of the λ promoter is controlled by a thermosensitive cl repressor (product of the c/857 gene) supplied form a resident defective prophage or cloned onto a compatible p 15A‐derived plasmid. Induction of the kil protein is brought about by a temperature shift of the culture from 28°C to 42°C. Plasmid pPLc28K1 contains the kil gene including its natural ribosome‐binding site and preceded by a transcription termination site. Using a bacterial strain with antitermination properties (e.g., M5219), periplasmic proteins can upon induction be gradually the growth of the host strain. The second plasmid pPLc321K1, contains the kil‐coding sequence preceded by an engineered ribosome binding site derived from the attenuator of the Escherichia coli tryptophan operon. With this plasmid induction of the Kil protein is very rapid and specific release of the periplasmic proteins in essentially complete within 30 min after induction. In a third construct, pcl857K1, the pL‐kil cassette together with c/857 allele are present on the same replicon, which is compatible with ColE1‐derived expression vectors. This configuration allows accumulation in the periplasm of cloned gene products, induced by, e.g., tac or trp promoters at low temperature and subsequent release into the medium following increase of the temperature of the culture. Under repressed conditions (growth at low temperature) all plasmids are perfectly stable in a large number of E. coli strains tested, also when cultivated on a 20‐L fermentor scale. Controlled, heat‐induced release of periplasmic proteins is highly specific and applicable at relatively high cell densities. The method therefore is an attractive alternative to cumbersome osmotic shock procedures for large‐scale cultures. © 1994 John Wiley & Sons, Inc.
Saccharification, fermentation, and protein recovery from low‐temperature AFEX‐treated coastal bermudagrass
Authors: Holtzapple Mark T. , Ripley E. Payson , Nikolaou Michael 
Published: December 2004

AbstractCoastal bermudagrass was pretreated by a low‐temperature ammonia fiber explosion (AFEX) process, which soaked the grass in liquid ammonia and then explosively released the pressure. Saccharifying enzymes were systematically applied to the AFEX‐treated grass corresponding to low, medium, and high loadings of cellulase/hemicellulase (from Trichoderma reesei), cellobiase, glucoamylase, and pectinase. Three‐day sugar yields linearly correlated with the logarithm of the cellulase loading. Supplemental enzymes (cellobiase, pectinase) caused upward shifts in the lines. The linearity and upward shifts are consistent with the HCH‐1 model of cellulose hydrolysis. The hydrolysis sugars were converted to ethanol using yeast (Saccharomyces cerevisiae). The solid residues were treated with proteases to attempt recovery of valuable proteins. The low‐temperature AFEX pretreatment was able o nearly double sugar yields. At the highest cellulase loadings (30 IU/g), the best reducing sugar and ethanol yields were 53% and 44% of the maximum potential, respectively. Protein recovery was, at most, 59% © 1994 John Wiley & Sons, Inc.
Broth recycle in a yeast fermentation
Authors: Hsiao Tzu‐Yin , Glatz Charles E. , Glatz Bonita A. 
Published: December 2004

AbstractFermentation is a water‐intensive process requiring treatment of large amounts of effluent broth. It is desirable to increase the ratio of product produced to the volume of effluent by minimizing the discharge of effluent from the fermentation process. A study of recycling spent fermentation process. A study of recycling spent fermentation broth for the subsequent fermentation was carried out with Apiotrichum curvatum an oleaginous yeast, as the working culture. Spent broth from a defined medium was recycled t replace as much as 75% of the water and salts for subsequent batches and this was repeated for seven sequential batches without affecting cell mass and lipid production. A 64% vlume reduction of wastewater was achieved in this manner. However, when using whey permeate as the medium, lipid production dropped after three consecutive recycle operations at 50% recycle, and after two consecutive recycle operations at 75% and 100% recycle. Accumulation of ions in the broth appeared to be responsible for the inhibition. An ion exchange step was able to eliminate the ion buildup and restore fermentation performance. © 1994 John Wiley & Sons, Inc.
The existence of a biological equilibrium in a trickling filter for waste gas purification
Authors: Diks R. M. M. , Ottengraf S. P. P. , Vrijlnad S. 
Published: December 2004

AbstractClogging is well‐known phenomenon in the application of a biological tricking filter for both waste gas and wastewater treatment. Nevertheless, no such observations or even significant changes in pressure drop have ever been recorded during the long‐term processing of a waste gas containing dichloromethane (DCM) as a sole carbon source. To obtain more information about this phenomenon, a detailed investigation into the carbon balance of this system has been performed. During a period of operation of about 200 days the rate of DCM elimination and the overall rate of CO2 production in a continuously operating filter were therefore recorded daily, thus allowing an evaluation of the overall conversion process. Furthermore pseudo‐steady‐state measurements were carried out on a regular basis. These experiments reveal more detailed information on the actual DCM conversion by Hyphomicrobium GJ21 within the biofilm. The combined results of the experiments described in this article show that on an overall basis a so‐called biological equilibrium, i.e., a situation of no net biomass accumulation, is obtained in the course of time. It appeared that the overall rate of CO2 production slowly increased until, after some 200 days, it finally counter‐balanced the conversion rate of DCM on a molar‐basis. As opposed to this result, all pseudo‐steady‐state experiments indicated that about 60% of the eliminated primary carbon source is converted into biomass. This is in good agreements with results from microkinetic experiments. Based on these results and evaluation of the experimental data, it is concluded that interactions between several microbial populations are involved in this biological equilibrium. These interactions include both biomass growth and biomass degradation. © 1994 John Wiley & Sons, Inc.
An Escherichia coli plasmid vector system for production of streptavidin fusion proteins: Expression and bioselective adsorption of streptavidin‐β‐galactosidase
Authors: Walsh Marie K. , Swaisgood Harold E. 
Published: December 2004

AbstractCovalently immobilized biotin was used as a biospecific adsorbant to investigate the application of streptavidin as an affinity domain for simultaneous purification and immobilization of recombinant proteins. A streptavidin‐β‐galactosidase fusion protein was constructed and tested as a model system. The gene for streptavidin from Streptomyces avidinii was modified by polymerase chain reaction to mutate the stop codon and to facilitate cloning into an Escherichia coli expression vector yielding a versatile plasmid with 37 unique restriction enzyme sites at the 3' end. E. coli β‐galactosidase was cloned in‐frame to the streptavidin gene. Analysis of lysates of induced recombinant E. coli cells by SDS‐PAGE and Western blots indicated that the 133.6‐kDa fusion protein was expressed. Sulfosuccinimidyl‐6‐(biotinamido) hexanoate was covalently immobilized on 3‐aminopropyl‐controled‐pore glass beads. Exposure of recombinant cell lysates to this support indicated that streptavidin‐β‐galactosidase was bioselectively adsorbed. The resulting biocatalyst contained 300 mg protein per gram of beads and exhibited a specific activity of 306 βmol/min per milligram protein with o‐nitrophenyl‐β‐D‐galactopyranoside as substrate corresponding to approximately 50% of that observed for commercially pure E. coli β‐galactosidase. © 1994 John Wiley & Sons, Inc.
Synthesis of protein‐containing polymers in organic solvents
Authors: Yang Zhen , Williams Darrel , Russell Alan J. 
Published: December 2004

AbstractSubtilisin has been modified with polyethylene glycol (PEG) monomethacrylate (MW 8000) by reductive alkylation, and incorporated into polymethyl methacrylate durring free‐radical initiated polymerization. The activity and stability of the PEG‐modified enzymes have been determined in aqueous buffer and organic solvents. The Km and Vmax values for unmodified, singly and doubly modified subtilisin were compared in these environments, and the half‐lives of both modified enzymes were remarkably high (up to 2 months). The protein‐containing polymer was analyzed for activity and polymer properties, and our results indicate that active subtilisin can be incorporated into polymethyl methacrylate during polymerization in organic solvents while retaining its activity and stability. © 1995 John Wiley & Sons, Inc.
On‐line gas analysis in animal cell cultivation: II. Methods for oxygen uptake rate estimation and its application to controlled feeding of glutamine
Authors: Eyer K. , Oeggerli A. , Heinzle E. 
Published: December 2004

AbstractDifferent methods for oxygen uptake rate (OUR) determinations in animal cell cultivation were investigated using a high quality mass spectrometer. Dynamic measurements have considerable disadvantages because of disturbances of the growing cells by the necessary variations of dissolved oxygen concentration. Only infrequent discrete measurements are possible using this method. Stationary liquid phase balance yielded better results with much higher frequency. Gas phase balancing has the advantage of not requiring dissolved oxygen measurement and knowledge of KLa, both of them are easily biased. It was found that simple gas phase balancing is either very inaccurate (error larger than expected signal) or very slow, with gas phase residence times of several hours. Therefore, a new method of aeration was designed. Oxygen and CO2 transfer are mainly achieved via sparging. The gas released to the headspace is diluted with a roughly 100‐fold stream of an inert gas (helium). Through this dilution, gas ratios are not changed for O2, CO2, Ar, and N2. The measurement of lower concentrations (parts per million and below) is easy using mass spectrometry with a secondary electron multiplier. With this new method an excellent accuracy and sufficient speed of analysis were obtained. All these on‐line methods for OUR measurement were tested during the cultivation of animal cells. The new method allowed better study of the kinetics of animal cell cultures as was shown with a hybridoma cell line (HFN 7.1, ATCC CRL 1606) producing monoclonal antibodies against human fibronectin. With the aid of these methods it was possible to find a correlation between a rapid decrease in oxygen uptake rate (OUR) and glutamine concentration. The sudden decrease in OUR can be attributed to glutamine depletion. This provided a basis for the controlled addition of glutamine to reduce the formation of ammonia produced by hydrolysis. This control method based on OUR measurement resulted in increased cell concentration and threefold higher product concentration. © 1995 John Wiley & Sons, Inc.
Effects of sorbitol addition on the action of free and immobilized hydrolytic enzymes in organic media
Authors: Triantafyllou Angeliki Öste , Wehtje Ernst , Adlercreutz Patrick , Mattiasson Bo 
Published: December 2004

AbstractThe effect of the addition of sorbitol on the activity and stability of enzymes was examined by monitoring transesterification reactions performed in organic media at various water activities (aw = 0.08 to 0.97). Lipases from Chromobacterium viscosum and Candida rugosa immobilized on celite, and chymotrypsin, free or immobilized on celite, were used. When the sorbitol‐containing enzymes were employed, higher reaction rates and less hydrolysis were observed. Immobilization of chymotrypsin resulted in high activity and operational stability, while the nonimmobilized enzyme was stable only in the presence of sorbitol. The activity of all preparations diminished after washing them with pyridine to remove sorbitol. Furthermore, severe stability problems occurred in the preparations lacking sorbitol. Sorbitol treatment, even after removal of the sorbitol itself, improved the activity of nonimmobilized chymotrypsin relative to the washed control. On the other hand, washing to remove sorbitol had a negative effect on the activity of both coimmobilized lipase and coimmobilized chymotrypsin. Addition of a substrate analogue, N‐acetyl‐L‐phenylalanine, to chymotrypsin yielded a preparation that exhibited higher activity than both the control and its sorbitol‐containing counterpart. Differential scanning calorimetry measurements revealed that the chymotrypsin–sorbitol complex was stable against thermal denaturation, undergoing transition at a high temperature (89°C). The transition temperatures of the substrate‐containing chymotrypsin and of the control were identical (72°C). © 1995 John Wiley & Sons, Inc.
Properties of microfiltration membranes: Mechanisms of flux loss in the recovery of an enzyme
Authors: Bowen W. Richard , Hall Nicola J. 
Published: December 2004

AbstractThe transmission and rate of filtration of the enzyme yeast alcohol dehydrogenase (YADH) has been studied at capillary pore microfiltration membranes. Photon correlation spectroscopy (PCS) with nanometer resolution showed that the enzyme existed as discreate molecules only for a narrow range of pH and ionic strength. Under such conditions, the transmission of the enzyme was high. However, the rate of filtration still decreased continuously with time. Analyssis of the time dependence of the rate of filtration indicated that this decrease was due to in‐pore enzyme deposition at low concentration (“standard blocking model”) and suface depositon at high concentration (“cake filtration model”). Use of atomic force microscopy (AFM) gave unequivocal and quantitative confirmation of these inferences. The work shows the great advantage of using advanced physical characterization techniques, both for the identification of the optimum conditions for filtration (PCS) and for the elucidation of mechanisms giving rise to inefficiencies in the filtration process (AFM). © 1995 John Wiley & Sons, Inc.
Genetically engineered charge modifications to enhance protein separation in aqueous two‐phase systems: Charge directed partitioning
Authors: Luther John R. , Glatz Charles E. 
Published: December 2004

AbstractThis report continues or examination of the effect of genetically engineered charge modifications on the partitioning behavior of proteins in aqueous two‐phase extration. The genetic modifications consisted of the fusion of charged peptide tails to β‐galactosidase and charge‐change point mutations to T4 lysozyme. Our previous article examined the influence of these charge modifications on partitioning as a function of interfacial potential difference. In this study, we examined charge directed partitioning behavior in PEG/dextran systems containing small amounts of the charged polymers diethylaminoethyl‐dextran (DEAE‐dextran) or dextran sulfate. The best results were obtained when attractive forces between the protein and polymer were present. Nearly 100% of the β‐galactosidase, which carries a net negative charge, partitioned to the DEAE‐dextran‐rich phase regardless of whether the phase was dextran or PEG. In these cases, cloudiness of the protein‐rich phases suggest that strong charge interactions resulted in protein/polymer aggregation, which may have contributed to the extreme partitioning. Unlike the potentialdriven partitioning reported previously, consistent partitioning trends were observed as a result of the fusion tails, with observed shifts in partition coefficient (Kp) of up to 37‐fold. However, these changes could not be solely attributed to charge‐based interactions. Similarly, T4 lysozyme, carrying a net positive charge, partitioned to the dextran sulfate‐containing phase, and displayed four‐ to sevenfold shifts in Kp as a result of the point mutations. These shifts were two to four times stronger than those observed for potential driven partitioning. Little effect on partitioning was observed when the protein and polymer had the same charge, with the exception of β‐galactosidase with polyarginine tails. The high positive charge density of these tails provided for a localized interaction with the dextran sulfate, and resulted in 2‐ to 15‐fold shifts in Kp. © 1995 John Wiley & Sons, Inc.
Factors affecting the esterification of lauric acid using an immobilized biocatalyst: Enzyme characterization and studies in a well‐mixed reactor
Authors: Lima F. Vázquez , Pyle D. L. , Asenjo J. A. 
Published: December 2004

AbstractThe esterification of lauric acid with geraniol catalyzed by the commercially immobilized lipase preparation from Mucor miehei, Lipozyme®, was studied in well‐stirred flasks. The enzyme support was characterized in terms of its internal and external surface area, protein location, and protein content. It was found that the enzyme was mainly located on the external surface of the support, therefore, internal diffusional limitations were not important. It was also shown that the protein content of the support depends on the size of the particle, with smaller particles containing higher amounts of protein per unit weight. Under the conditions studied, the reaction was not under external mass transfer limitations, and the initial reaction rate depended on the size of the support particles. This was mainly due to the different protein contents on the support as a function of particle size and not to internal or external mass transfer limitations. Also, it was found that the inhibition exerted by water was predominantly a physical effect due to its accumulation around the enzyme. It was also found that the reaction was substrate inhibited by lauric acid, but not by geraniol. © 1995 John Wiley & Sons, Inc.
Determination of the volumetric mass transfer coefficient (kLa) using the dynamic “gas out–gas in” method: Analysis of errors caused by dissolved oxygen probes
Authors: Tribe L. A. , Briens C. L. , Margaritis A. 
Published: December 2004

AbstractThere are many dynamic methods for measuring the volumetric mass transfer coefficient. The “gas out–gas in” method can directly determine the volumetric mass transfer coefficient in a bioreactor system and provide estimates of the volumetric microbial oxygen uptake rate and the average oxygen saturation concentration at the gas–liquid interface. The errors on these parameters are large if the dissolved oxygen probe response time is not considered. For reliable measurements, deconvolution of the oxygen probe measurements must be made. © 1995 John Wiley & Sons, Inc.
Intracellular responses of productive hybridomas subjected to high osmotic pressure
Authors: Oh Steve K. W. , Chua Florence K. F. , Choo Andre B. H. 
Published: December 2004

AbstractIt has previously been found tht hybridoma cells undr hyuerosmotic stress produce higher amounts of antibody. This study indentified the cellular processes and mechanisms that occur during this event. In studies fo hybridomas adpated toosmolarities ranging between 300 and 450 mOsm (uusing NaCl), antibody production increased to a saturation level while cell growth decreased progressively. At 500 mOsm, lower, cell numbers and markedly decreaased productivity resulted. Sucrose and KCl were found to induce similar trends, except to different extents.Several important change in cellulaes in cellular responses were onsserved. Elevation of osmnolarity with NaCl from 300 to 350 mOsm causes an increase of zwiterionic amino acid upatake, which, occurredvia Na+‐dependent transport systems. In particuar, systedm A was enhanced by 1.86‐fold, but noenhancement was observed for Na+‐independent transport systems, In addition, amino acids reactive with Na+‐dependent transport systems were onserved to be abundant within osmotically stressed hybridomas in the middle and dlate exponentoial statges. Sucroses ans Kcl caused similar uptake effects, but to a laeeser degree, as long as sodium ions were present in solution.Specific consumption rates fo glucose and glutamine incresase by 19% and 20%, respectively, under high osmolarity treatment. Thewse increases were confirmed by the 5% to 10% increase in cellular metabolic acitivity. At 350 mOsm, growth rate was slower, compared with the 300‐mOsm culture, which was reflected by thelower DNA conetr4ation. Stressed cultures contained enhanced leyls of tatal RNA content could in turn increase the translation rates of proteins. This was reflected in the accumulation of both dry cell weight and total cellular protein at linear rates of 0.42 μG/106 cells/mOsm and 0.21 μg/106 cells/mOmsm, respectively, with increasing osmolarty between 300 and 450 mOsm.Overall, hybridoms increased their metabolic activities and amino acids uptake via the Na+‐dependent symports to compensate for teh osmotically elevated external environment. These effects contribute directly and indirectly tothe increased cell mass consisting of a larger pool of amono acids, RNA, cellular proteins, and seecreted antibody produt. © 1995 John Wiley & Sons, Inc.
Physico‐chemical properties of the encapsulation matrix and germination of carrot somatic embryos
Authors: Timbert Raphaëlle , Barbotin Jean‐Noël , Kersulec Alain , Bazinet Christophe , Thomas Daniel 
Published: December 2004

AbstractCarrot somatic embryos were encapsulated in alginate gel beads. To improve the quality of a “synthetic seed” coating, the rheology and dehydration properties of different matrices were tested. By increasing alginate and CaCl2 concentrations, additional mineral elements were shown to increase resistance to rupture, and to depress the germination of somatic embryos. A polysaccharide addition was found to slow the alginate matrix dehydration; alginate‐gellan gum and alginate‐kaolin matrices could preserve the viability of somatic embryos at low relative humidities (30% to 35% germinations at 50% relative humidity) to a greater extent than other matrices. © 1995 John Wiley & Sons, Inc.