bluuebunny/crossref_metadata_2025_split huggingface dataset:
Multienzyme catalysis in microfluidic biochips
Authors: Lee Moo‐Yeal , Srinivasan Aravind , Ku Bosung , Dordick Jonathan S. 
Published: May 2003

AbstractThe attachment of enzymes to glass microfluidic channels has been achieved using a highly reactive poly(maleic anhydride‐alt‐α‐olefin) (PMA)‐based coating that is supplied to the microchannel in a toluene solution. The PMA reacts with 3‐aminopropyltriethoxysilane groups linked to the glass surface to form a matrix that enables additional maleic anhydride groups to react with free amino groups on enzymes to give a mixed covalent–noncovalent immobilization support. Using a simple T‐channel microfluidic design, with reaction channel dimensions of 200 μm wide (at the center), 15 μm deep, and 30 mm long giving a reaction volume of 90 nL, soybean peroxidase (SBP) was attached at an amount up to 0.6 μg/channel. SBP‐catalyzed oxidation of p‐cresol was performed in aqueous buffer (with 20% [v/v], dimethylformamide) containing H2O2, with microfluidic transport enabled by electroosmotic flow (EOF). Michaelis–Menten kinetics were obtained with Km and Vmax values of 0.98 mM and 0.21 μmol H2O2 converted/mg SBP per minute, respectively. These values are nearly identical to nonimmobilized SBP kinetics in aqueous–DMF solutions in 20‐μL volumes in 384‐well plates and 5‐mL reaction volumes in 20‐mL scintillation vials. These results indicate that SBP displays intrinsically native activity even in the immobilized form at the microscale, and further attests to the mild immobilization conditions afforded by PMA. Bienzymic and trienzymic reactions were also performed in the microfluidic biochip. Specifically, a combined Candida antarctica lipase B–SBP bienzymic system was used to convert tolyl acetate into poly(p‐cresol), and an invertase–glucose oxidase SBP trienzymic system was used to take sucrose and generate H2O2 for SBP‐catalyzed synthesis of poly(p‐cresol). © 2003 Wiley Periodicals, Inc. Biotechnol Bioeng 83: 20–28, 2003.
A novel biphasic extractive membrane bioreactor for minimization of membrane‐attached biofilms
Authors: Splendiani Antonietta , Nicolella Cristiano , Livingston Andrew G. 
Published: May 2003

AbstractExtractive membrane bioreactor (EMB) systems offer a means of biologically treating wastewaters, but, like other membrane processes, are constrained by their tendency to be fouled by membrane‐attached biofilms (MABs). This study describes a new approach to eradicate MAB formation and accumulation in EMB systems. To this end, an innovative EMB configuration, the biphasic extractive membrane bioreactor (BEMB), has been developed. In BEMB systems, the two main constituents of the EMB process, membrane and bacteria, are kept separated and interact via a suitable recirculating solvent. Nineteen candidate solvents were tested to assess their suitability for BEMB application. Based on the results of the solvent selection, guidelines are provided to screen solvents for BEMB application. BEMB and EMB runs were carried out to demonstrate the effectiveness of BEMB technology in avoiding MAB accumulation and to compare BEMB and EMB performance. A synthetic wastewater containing monochlorobenzene (MCB) was used as a model system. Abiotic BEMB and EMB runs were carried out and used as comparative references for estimating the effect of MAB accumulation on system performance. MAB thickness in the BEMB systems was controlled at 18 μm during 1 month of operation, whereas, in the EMB systems, MAB thickness reached 1250 μm. Analysis of mass transport in EMB and BEMB systems revealed that the high affinity of the permeating molecules for the solvent may contribute to a reduction in shell‐side mass transfer resistance. This reduction of shell‐side mass transfer resistance and the absence of MAB accumulation led to overall mass transfer coefficients of about sevenfold greater (4.5 × 10−5 m s−1) in the BEMB system than in the EMB system (0.6 × 10−5 m s−1). © 2003 Wiley Periodicals, Inc. Biotechnol Bioeng 83: 8–19, 2003.
Large‐scale propagation of a replication‐defective adenovirus vector in stirred‐tank bioreactor PER.C6™ cell culture under sparging conditions
Authors: Xie Liangzhi , Metallo Christian , Warren James , Pilbrough Warren , Peltier Joseph , Zhong Tanya , Pikus Lana , Yancy Amanda , Leung John , Auniņš John G. , Zhou Weichang 
Published: May 2003

AbstractLarge‐scale propagation of replication‐defective adenovirus vectors has not been well studied to date. One of the challenges for efficient propagation at large scale is to overcome the sensitivity of virus infected cells to gas sparging required for oxygenation and CO2 removal. In our initial experiments, it was observed that productivity of an adenovirus vector was significantly reduced under sparging conditions as compared to nonsparged, i.e., surface‐aerated controls in serum‐free cultures. Investigations led to the identification of a buffer containing surfactant (Polysorbate‐80, PS‐80) that was included in the virus seed stock formulation and introduced through virus infection into the culture at a very low concentration as the cause of the reduced virus productivity. This finding was not obvious and trivial, as neither uninfected sparged nor infected nonsparged PER.C6™ cells in serum‐free cultures were affected by the buffer at such a low PS‐80 concentration of 0.00025% (v/v), which is a common component of serum‐free cell culture media. These results strongly suggest that virus‐infected cells behave very differently from uninfected cells under sparging conditions. To mitigate the deleterious effects of sparging, the virus seed stock was prepared in the absence of the buffer containing PS‐80. At the same time, the concentration of Pluronic‐F68 (PF‐68) in the serum‐free medium was increased to 1 g/L, at which cell growth and metabolism were unaffected, even though this measure alone did not result in virus productivity improvement. Only by implementing the two measures together was virus productivity loss completely eliminated under sparging conditions. After demonstration of the process robustness in 2‐L bioreactors, this adenovirus propagation process was successfully scaled up to 250 L in a 300‐L bioreactor under the worst‐case sparging conditions projected for 10,000‐L scale. © 2003 Wiley Periodicals, Inc. Biotechnol Bioeng 83: 45–52, 2003.
Metabolic load of recombinant protein production: Inhibition of cellular capacities for glucose uptake and respiration after induction of a heterologous gene in Escherichia coli
Authors: Neubauer P. , Lin H. Y. , Mathiszik B. 
Published: May 2003

AbstractThe strong expression of recombinant proteins in bacteria affects the primary carbon and energy metabolism resulting in growth inhibition and acetate formation. By applying glucose pulses to fed‐batch fermentations performed for production of a heterologous (α‐glucosidase in Escherichia coli, we show that the induction of the recombinant gene strongly inhibits the maximum specific uptake capacities for glucose and the respiration capacity. The accumulation of glucose in the fermentation medium promotes the growth of plasmid‐free cells. These inhibition effects are well described by including the kinetics of product formation into a recently published dynamic model (Lin et al. [2001] Biotechnol Bioeng 73:349–357). The new model also includes the population characteristics and gives a good fit to the measured data describing growth, production, substrate consumption, by‐product formation, and respiration. © 2003 Wiley Periodicals, Inc. Biotechnol Bioeng 83: 53–64, 2003.
Construction of biofilms with defined internal architecture using dielectrophoresis and flocculation
Authors: Verduzco‐Luque Cynthia E. , Alp Burçak , Stephens Gillian M. , Markx Gerard H. 
Published: May 2003

AbstractA novel approach was developed for the construction of biofilms with defined internal architecture using AC electrokinetics and flocculation. Artificial structured microbial consortia (ASMC) consisting of localized layered microcolonies of different cell types were formed by sequentially attracting different cell types to high field regions near microelectrodes using dielectrophoresis. Stabilization of the microbial consortia on the electrode surface was achieved by crosslinking the cells using the flocculant polyethyleneimine (PEI). Consortia of Escherichia coli, Micrococcus luteus, and Saccharomyces cerevisiae were made as model systems. Also, more natural consortia were made of the bacteria Pseudomonas putida, Clavibacter michiganense, and Methylobacterium mesophilum, which are found together in consortia during biodegradation of metal‐cutting waste fluids. © 2003 Wiley Periodicals, Inc. Biotechnol Bioeng 83: 39–44, 2003.
The use of dinoflagellate bioluminescence to characterize cell stimulation in bioreactors
Authors: Chen Antony K. , Latz Michael I. , Frangos John A. 
Published: May 2003

AbstractBioluminescent dinoflagellates are flow‐sensitive marine organisms that produce light emission almost instantaneously upon stimulation by fluid shear in a shear stress dose‐dependent manner. In the present study we tested the hypothesis that monitoring bioluminescence by suspended dinoflagellates can be used as a tool to characterize cellular response to hydrodynamic forces in agitated bioreactors. Specific studies were performed to determine: (1) impeller configurations with minimum cell activation, (2) correlations of cellular response and an integrated shear factor, and (3) the effect of rapid acceleration in agitation. Results indicated that (1) at a volumetric mass transfer coefficient of 3 × 10−4 s−1, marine impeller configurations were less stimulatory than Rushton configurations, (2) bioluminescence response and a modified volumetric integrated shear factor had an excellent correlation, and (3) rapid acceleration in agitation was highly stimulatory, suggesting a profound effect of temporal gradients in shear in increasing cell stimulation. By using bioluminescence stimulation as an indicator of agitation‐induced cell stimulation and/or damage in microcarrier cultures, the present study allows for the verification of hypotheses and development of novel mechanisms of cell damage in bioreactors. © 2003 Wiley Periodicals, Inc. Biotechnol Bioeng 83: 93–103, 2003.
Metabolic flux and metabolic network analysis of Penicillium chrysogenum using 2D [13C, 1H] COSY NMR measurements and cumulative bondomer simulation
Authors: van Winden Wouter A. , van Gulik Walter M. , Schipper Dick , Verheijen Peter J.T. , Krabben Preben , Vinke Jacobus L. , Heijnen Joseph J. 
Published: May 2003

AbstractAt present two alternative methods are available for analyzing the fluxes in a metabolic network: (1) combining measurements of net conversion rates with a set of metabolite balances including the cofactor balances, or (2) leaving out the cofactor balances and fitting the resulting free fluxes to measured 13C‐labeling data. In this study these two approaches are applied to the fluxes in the glycolysis and pentose phosphate pathway of Penicillium chrysogenum growing on either ammonia or nitrate as the nitrogen source, which is expected to give different pentose phosphate pathway fluxes. The presented flux analyses are based on extensive sets of 2D [13C, 1H] COSY data. A new concept is applied for simulation of this type of 13C‐labeling data: cumulative bondomer modeling. The outcomes of the 13C‐labeling based flux analysis substantially differ from those of the pure metabolite balancing approach. The fluxes that are determined using 13C‐labeling data are shown to be highly dependent on the chosen metabolic network. Extending the traditional nonoxidative pentose phosphate pathway with additional transketolase and transaldolase reactions, extending the glycolysis with a fructose 6‐phosphate aldolase/dihydroxyacetone kinase reaction sequence or adding a phosphoenolpyruvate carboxykinase reaction to the model considerably improves the fit of the measured and the simulated NMR data. The results obtained using the extended version of the nonoxidative pentose phosphate pathway model show that the transketolase and transaldolase reactions need not be assumed reversible to get a good fit of the 13C‐labeling data. Strict statistical testing of the outcomes of 13C‐labeling based flux analysis using realistic measurement errors is demonstrated to be of prime importance for verifying the assumed metabolic model. © 2003 Wiley Periodicals, Inc. Biotechnol Bioeng 83: 75–92, 2003.
Evaluation of spectrofluorometry as a tool for estimation in fed‐batch fermentations
Authors: Hagedorn Andrea , Legge Raymond L. , Budman Hector 
Published: May 2003

AbstractNative culture fluorescence was investigated as an additional source of information for predicting biomass and glucose concentrations in a fed‐batch fermentation of Alcaligenes eutrophus. Partial least squares (PLS) regression and a feed forward neural network (FFNN) coupled with principle component analysis (PCA) were each used to model the kinetics of the fermentation. Data from three fermentations was combined to form a training set for model calibration and data from a fourth fermentation was used as the testing set. The fluorescent soft‐sensors were compared with a previously developed feed forward neural network soft‐sensor model which used oxygen uptake rate (OUR), carbon dioxide evolution rate (CER), aeration rate, feed rate, and fermentor volume to estimate biomass and glucose concentrations. The best model performance for predicting both biomass and glucose concentrations was achieved using the native fluorescence‐based models. Real data predictions of the biomass concentration in the testing set were obtained using both the PLS and FFNN PCA modeling utilizing fluorescence measurements plus the rate of change of the fluorescence measurements. Accurate predictions of the glucose concentration in the testing set were obtained using the FFNN PCA modeling technique utilizing the rate of change of the fluorescence measurements. Substrate exhaustion was indicated qualitatively by a first‐order PLS model utilizing the rate of change of fluorescence measurements. These results indicate that native culture fluorescence shows promise for providing additional valuable information to enhance predictive modeling which cannot be extracted from other easily acquired measurements. © 2003 Wiley Periodicals, Inc. Biotechnol Bioeng 83: 104–111, 2003.
Fluid shear contributions to bacteria cell detachment initiated by a monoclonal antibody
Authors: Mascari Lisa , Ymele‐Leki Patrick , Eggleton Charles D. , Speziale Pietro , Ross Julia M. 
Published: May 2003

AbstractReceptor‐mediated adhesion of bacteria to biological surfaces is a significant step leading to infection. Due to an increase in bacterial antibiotic resistance, novel methods to block and disrupt these specific interactions have gained considerable interest as possible therapeutic strategies. Recently, several monoclonal antibodies specific for the Staphylococcus aureus collagen receptor demonstrated specialized ability to displace attached cells from collagen in static assays. In this study, we experimentally examine the monoclonal antibody detachment functionality under physiological shear conditions to evaluate the role of this parameter in the detachment process. The detachment of staphylococci from collagen was quantified in real‐time using a parallel plate flow chamber, phase contrast video‐microscopy and digital image processing. The results demonstrate a unimodal dependence of detachment on fluid wall shear rate. The observed decrease in effective detachment rate with increasing force at the highest shear levels evaluated is counterintuitive and has not been previously demonstrated. Several possible mechanisms of this result are discussed. © 2003 Wiley Periodicals, Inc. Biotechnol Bioeng 83: 65–74, 2003.
Hydrodynamic stress and lethal events in sparged microalgae cultures
Authors: Barbosa Maria J. , Albrecht Marco , Wijffels René H. 
Published: May 2003

AbstractThe effect of high superficial gas velocities in continuous and batch cultures of the strains Dunaliella tertiolecta, Chlamydomonas reinhardtii wild‐type and cell wall‐lacking mutant was studied in bubble columns. No cell damage was found for D. tertiolecta and C. reinhardtii (wild‐type) up to superficial gas velocities of 0.076 and 0.085 m s−1, respectively, suggesting that high superficial gas velocities alone cannot be responsible for cell death and, consequently, bubble bursting cannot be the sole cause for cell injury. A death rate of 0.46 ± 0.08 h−1 was found for C. reinhardtii (cell wall‐lacking mutant) at a superficial gas velocity of 0.076 m s−1, and increased to 1.01 ± 0.29 h−1 on increasing superficial gas velocity to 0.085 m s−1. Shear sensitivity is thus strain‐dependent and to some extent the cell wall plays a role in the protection against hydrodynamic shear. When studying the effect of bubble formation at the sparger in batch cultures of D. tertiolecta by varying the number of nozzles, a death rate of 0.047 ± 0.016 h−1 was obtained at high gas entrance velocities. D. tertiolecta was cultivated in a pilot‐plant reactor under different superficial gas velocities of up to 0.026 m s−1, with relatively low gas entrance velocities and no cell damage was observed. There is some indication that the main parameter causing cell death and damage was the gas entrance velocity at the sparger. © 2003 Wiley Periodicals, Inc. Biotechnol Bioeng 83: 112–120, 2003.
Optimization of catechol production by membrane‐immobilized polyphenol oxidase: A modeling approach
Authors: Boshoff A. , Burton M. H. , Burton S. G. 
Published: May 2003

AbstractAlthough previous research has focused on phenol removal efficiencies using polyphenol oxidase in nonimmobilized and immobilized forms, there has been little consideration of the use of polyphenol oxidase in a biotransformation system for the production of catechols. In this study, polyphenol oxidase was successfully immobilized on various synthetic membranes and used to convert phenolic substrates to catechol products. A neural network model was developed and used to model the rates of substrate utilization and catechol production for both nonimmobilized and immobilized polyphenol oxidase. The results indicate that the biotransformation of the phenols to their corresponding catechols was strongly influenced by the immobilization support, resulting in differing yields of catechols. Hydrophilic membranes were found to be the most suitable immobilization supports for catechol production. The successful biocatalytic production of 3‐methylcatechol, 4‐methylcatechol, catechol, and 4‐chlorocatechol is demonstrated. © 2003 Wiley Periodicals, Inc. Biotechnol Bioeng 83: 1–7, 2003.
111In-labelled octreotide binding by the somatostatin receptor subtype 2 in neuroendocrine tumours
Authors: Hashemi S H , Benjegård S-A , Ahlman H , Wängberg B , Forssell-Aronsson E , Billig H , Nilsson O 
Published: May 2003

Abstract

Background
The aim of this study was to investigate the importance of somatostatin receptor subtype 2 (SSTR2) expression for 111In-labelled diethylenetriamine-pentaacetic acid (DTPA)-d-Phe1-octreotide binding and uptake of 111In in neuroendocrine tumours.

Methods
111In activity concentrations in surgical biopsies from neuroendocrine tumours (midgut carcinoid and medullary thyroid carcinoma), breast carcinoma and blood were determined 1–8 days after intravenous injection of 111In-labelled DTPA-d-Phe1-octreotide (140–350 MBq). The ratio of 111In activity concentrations between tumour tissue and blood (T/B value) was calculated. The expression of SSTR2 messenger RNA (mRNA) in tumour biopsies was quantitated by ribonuclease protection assay and SSTR2 protein was localized by immunocytochemistry.

Results
T/B values were highest for tumour biopsies from midgut carcinoids (mean 160 (range 4–1200); n = 65) followed by medullary thyroid carcinoma (mean 38 (range 2–350); n = 88) and breast carcinoma (mean 18 (range 4–41); n = 4). The expression of SSTR2 mRNA (relative to the NCI-H69 cell line) was highest in tumour biopsies from midgut carcinoids (mean 2·5 (range 0·83–6·0); n = 40) followed by medullary thyroid carcinoma (mean 1·3 (range 0·20–6·0); n = 7) and breast carcinoma (mean 0·66 (range 0·29–1·0); n = 9). In tumour biopsies SSTR2 protein was localized exclusively to tumour cells.

Conclusion
Midgut carcinoid tumours showed a much higher level of SSTR2 expression than medullary thyroid carcinoma in accordance with superior tumour imaging by octreotide scintigraphy. The high SSTR2 mRNA values and T/B values observed in midgut carcinoid tumours were positively correlated.
Extrahepatic disease does not contraindicate hepatectomy for colorectal liver metastases
Authors: Elias D , Ouellet J-F , Bellon N , Pignon J-P , Pocard M , Lasser P 
Published: May 2003

Abstract

Background
Extrahepatic disease has always been considered an absolute contraindication to hepatectomy for liver metastases. The present study reports the long-term outcome and prognostic factors of patients undergoing resection of extrahepatic disease simultaneously with hepatectomy for liver metastases.

Methods
From January 1987 to January 2001, 111 (30 per cent) of 376 patients who had hepatectomy for colorectal liver metastases underwent simultaneous resection of extrahepatic disease with curative intent.

Results
Surgery was considered R0 in 77 patients (69 per cent) and palliative (R1 or R2) in 34 patients (31 per cent). The mortality rate was 4 per cent and the morbidity rate 28 per cent. After a median follow-up of 4·9 years, the overall 3- and 5-year survival rates were 38 and 20 per cent respectively. The 5-year overall survival rate of patients with R0 resection only (n = 75) was 29 per cent. The difference in survival between patients with and without extrahepatic disease discovered incidentally at operation was significant, as was the number of liver metastases.

Conclusion
Extrahepatic disease in patients with colorectal cancer who also have liver metastases should no longer be considered an absolute contraindication to hepatectomy. However, the presence of more than five liver metastases and the incidental intraoperative discovery of extrahepatic disease remain contraindications to hepatic resection.
High recurrence rate after atypical resection for pancreatic metastases from renal cell carcinoma
Authors: Bassi C , Butturini G , Falconi M , Sargenti M , Mantovani W , Pederzoli P 
Published: May 2003

Abstract

Background
Pancreatic metastases from renal cell carcinoma are rare but highly resectable. The aim of this study was to review a series of patients with this condition.

Methods
The study involved 22 consecutive patients with histologically proven pancreatic metastases from renal cell cancer.

Results
Seventeen of the 22 patients had surgery. No patient died but eight of the 17 patients had a postoperative complication. Median follow-up was 33 (range 1–96) months. The 24- and 60-month survival probabilities were 0·84 and 0·53 respectively. Five patients who did not undergo surgery had 24- and 60-month survival probabilities of 0·53 and 0·26 respectively. The difference between the two groups was significant (P = 0·040).

Conclusion
Despite the slow development of these secondaries and their well encapsulated morphology, the high rate of recurrence after limited resection suggests that radical resection should be recommended.