Home About us Contact
|
Home About us Contact | ||
|
|
||
Maximum Yield (maximum + yield)
Selected AbstractsCharacterization of Pantoea dispersa UQ68J: producer of a highly efficient sucrose isomerase for isomaltulose biosynthesisJOURNAL OF APPLIED MICROBIOLOGY, Issue 1 2004L. Wu Abstract Aims:, Isolation, identification and characterization of a highly efficient isomaltulose producer. Methods and Results:, After an enrichment procedure for bacteria likely to metabolize isomaltulose in sucrose-rich environments, 578 isolates were screened for efficient isomaltulose biosynthesis using an aniline/diphenylamine assay and capillary electrophoresis. An isolate designated UQ68J was exceptionally efficient in sucrose isomerase activity. Conversion of sucrose into isomaltulose by UQ68J (enzyme activity of 90,100 U mg,1 DW) was much faster than the current industrial strain Protaminobacter rubrum CBS574.77 (41,66 U mg,1 DW) or a reference strain of Erwinia rhapontici (0·3,0·9 U mg,1 DW). Maximum yield of isomaltulose at 78,80% of supplied sucrose was achieved in less than half the reaction time needed by CBS574.77, and the amount of contaminating trehalulose (4%) was the lowest recorded from an isomaltulose-producing microbe. UQ68J is a Gram negative, facultatively anaerobic, motile, noncapsulate, straight rod-shaped bacterium producing acid but no gas from glucose. Based on 16S rDNA analysis UQ68J is closest to Klebsiella oxytoca, but it differs from Klebsiella in defining characteristics and most closely resembles Pantoea dispersa in phenotype. Significance and Impact of Study:, This organism is likely to have substantial advantage over previously characterized sucrose isomerase producers for the industrial production of isomaltulose. [source] Automated method for measuring globin adducts of acrylamide and glycidamide at optimized Edman reaction conditions,RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 6 2006Hubert W. Vesper The general population is exposed to acrylamide, a potential human carcinogen, through food and cigarette smoke. The assessment of human exposure to acrylamide is important in the evaluation of health risks associated with this chemical. Hemoglobin adducts of acrylamide (AA-Hb) and its primary metabolite glycidamide (GA-Hb) are established biomarkers of acrylamide exposure and methods to measure these biomarkers using modified Edman reaction are described. Only limited information about the optimal Edman reaction conditions such as pH or temperature is available for these adducts and the existing methods do not allow automation needed in biomonitoring studies. In this study, the yield of Edman products of AA-Hb and GA-Hb between pH 3,10 and at 35,55°C at different time intervals, and the applicability of liquid-liquid extraction on diatomaceous earth for analyte extraction, were assessed and results were used in a new optimized method. The applicability of our optimized method was assessed by comparing results obtained with a convenience sample from 96 individuals with a conventional method. Maximum yield of Edman products was obtained between pH 6,7, heating the reaction solution at 55°C for 2,h resulted in the same yields as with conventional conditions, and use of diatomaceous earth was found suitable for automated analyte extraction. Using these conditions, no difference was observed between our optimized and a conventional method. The median globin adduct values in the convenience sample are 129,pmol/g globin (range: 27,453,pmol/g globin) and 97,pmol/g globin (range: 27,240,pmol/g globin) for AA-Hb and GA-Hb, respectively. The GA-Hb/AA-Hb ratio decreases significantly with increasing AA-Hb values indicating that measurement of AA-Hb as well as GA-Hb are needed to appropriately assess human exposure to acrylamide. Published in 2006 by John Wiley & Sons, Ltd. [source] Simulation of optimal harvesting strategies for small-scale mixed-sex tilapia (Oreochromis shiranus Boulenger 1896) ponds using a bio-economic modelAQUACULTURE RESEARCH, Issue 4 2007Francis Saiti Abstract A cohort-based bio-economic biomass growth and economic model, validated with data from experiments conducted in Malawi, was used to identify an optimal harvesting strategy for mixed-sex tilapia ponds. Three harvesting scenarios (baseline, economic optimum time +10 days and economic optimum time) were used. In each harvesting scenario four options were explored: (i) no further harvest, harvest every (ii) 60 days, (iii) 90 days and (iv) 120 days after initial harvest. The lowest simulated yield (487 kg ha,1 year,1) was obtained when no partial harvesting was carried out and fish were harvested after 365 days. Maximum yield (4416 kg ha,1 year,1) was obtained when partial harvests were carried out every 90 days starting with a first harvest of fish weighing 60 g or more at day 90. Maximum financial returns (US$2561 ha,1 year,1) were obtained when partial harvests were carried out every 120 days starting with the first harvest at day 90 and removing all fish ,60 g. The model simulations indicate that mixed-sex tilapia culture may be profitable for tilapia farmers in Africa where markets accept small (60,150 g)-sized fish. The study further shows that a cohort-based population growth model can be reliably incorporated in tilapia production models to simulate fish yields in mixed-sex tilapia production systems. However, incorporation of intergenerational competition effects could improve the model's utility as a decision support tool for managing mixed-sex tilapia production. [source] Enantioselective reduction of pentoxifylline to lisofylline using whole-cell Lactobacillus kefiri biotransformationBIOTECHNOLOGY JOURNAL, Issue 4 2007bieta P, kala; Dr. Abstract Lisofylline (LSF) is a drug candidate that has been under investigation for acute respiratory distress syndrome, acute lung injury, septic shock and mucositis. As LSF is not commercially available in our country, we produced it for pharmacokinetic studies. In the present work whole-cell reduction of pentoxifylline [1-(5-oxohexyl)-3,5-dimethylxanthine] to LSF [1-(5R-hydroxyhexyl)-3,5-dimethylxanthine] using Lactobacillus kefiri DSM 20587 was investigated. Glucose or 2-propanol was used as a co-substrate to regenerate the NADPH cofactor. The reaction conditions were optimized. The influence of different concentrations of co-substrates on the yield and enantioselectivity of the biotransformation of pentoxifylline into LSF were tested. Maximum yield (100%) of biotransformation was reached in the presence of glucose as a co-substrate. At glucose concentrations of 675 and 900 mM the bioreduction of pentoxifylline proceeded highly enantioselectively (enantiomeric excess for the R enantiomer of 98%). [source] Influence of Fungal Elicitors on Production of Ajmalicine by Cell Cultures of Catharanthus roseusBIOTECHNOLOGY PROGRESS, Issue 1 2002Ajay Namdeo Suspension cultures of Catharanthus roseus ( C. roseus) were elicited with fungal cell wall fragments of Aspergillus niger (A.niger), Fusarium moniliforme (F. moniliforme), and Trichoderma viride (T.viride). The effects of elicitor dosage, exposures time, and age of subculture on ajmalicine accumulation were studied. A higher concentration of elicitor extract responded positively to C. roseus suspension cultures. Ajmalicine accumulation increased by about 3-fold when cells were treated with A.niger, F. moniliforme, and T. viride. The maximum ajmalicine production (75 ,g g,1 dry weight (DW)) was observed in cells treated with T. viride. Cell cultures were elicited with 5% preparation of A. niger, F. moniliforme, and T. viride and exposed for 24, 48, 72, and 96 h. for elicitation. Suspension cultures elicited with T. viride for 48 h showed a 3-fold increase (87 ,g g,1 DW) in ajmalicine contents, whereas A. niger and F. moniliforme synthesized a 2-fold increase in alkaloid and yielded 52 and 56 ,g g,1 DW ajmalicine, respectively. C. roseus cells of different age (5,10, 15, 20, and 25 days old) were treated with a 5% elicitor of A. niger, F. moniliforme, and T. viride and investigated elicitors activity at different age of cell cultures. Maximum yield 166 ,g g,1 DW of ajmalicine was synthesized in 20 day old suspension cultures treated with T. viride. A longer period of incubation of cell cultures with elicitors adversely affected the ajmalicine synthesis. [source] Effects of organic matter and initial carbon,nitrogen ratio on the bioconversion of volatile fatty acids from sewage sludgeJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 7 2008Xiaoling Liu Abstract BACKGROUND: The biodegradable organic matter and the initial carbon,nitrogen ratio can be substantially different in different batches of sewage sludge, which results in a difference in the acidification efficiency of sludge. Using sewage sludge from three different sources, batch tests were performed to analyze the relationship between volatile fatty acids (VFAs) and consumed organic matter, and to investigate the effects of initial carbon,nitrogen (C/N) ratio on the acidification efficiency of sludge. RESULTS: Maximum yields of 152.1 ± 3.5 mg total VFAs-COD per gram volatile solid (VS) added and 22.4 ± 1.2 mg butyric acid-COD g,1 VS added were obtained from the sludge with the highest initial C/N ratio. Statistical analysis indicated that protein was the major substrate for the produced VFAs. The sludge with the least initial C/N ratio (5.01) had the least yield, and only acetic acid, which was also mainly related to protein, was detected. CONCLUSION: The initial carbon,nitrogen ratio was one of the most important factors influencing the distribution patterns of VFAs and the yield of total VFAs produced from sewage sludge. A high C/N ratio could not only improve the yield of total VFAs but also enhance the yield of butyric acid. Copyright © 2008 Society of Chemical Industry [source] Synthesis of 1-amino-2-methylindoline by Raschig process: Parallel reactions, modeling, and optimizationINTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 10 2002M. Elkhatib The reaction between chloramine and 2-methylindoline was studied at pH 12.89, T = 40°C, and for different initial concentrations of reactants. The interaction includes two concurrent bimolecular mechanisms leading to 1-amino-2-methylindoline and 2-methylindole. The rate laws were determined at the first moments of the reaction by using a differential method. By considering the totality of the reactions that occur in the medium, an appropriate mathematical model was developed. It permits to follow the evolution of the system over time and to calculate the final yields of reaction products. An optimization in terms of the initial contents of 2-methylindoline and chloramine was performed. It indicated that the maximum yield of 1-amino-2-methylindoline does not exceed 56%. The results show the limit of the Raschig process for the synthesis of indolic hydrazines in aqueous medium. © 2002 Wiley Periodicals, Inc. Int J Chem Kinet 34: 575,584, 2002 [source] Age, growth, mortality and population structure of the oyster, Crassostrea madrasensis, in the Moheskhali Channel (southeastern coast of Bangladesh)JOURNAL OF APPLIED ICHTHYOLOGY, Issue 1 2008S. M. Nurul Amin Summary The population structure, age, growth, mortality and harvest intensity of the oyster Crassostrea madrasensis were examined in the Moheskhali Channel, Bangladesh between June 2003 and May 2004. The channel is a representative habitat for the area. C. madrasensis monthly length frequency data were analyzed using FiSAT software for estimating population parameters, including asymptotic length (L), growth co-efficient (K) and recruitment pattern to assess the status of the stock. Asymptotic length (L,) and growth co-efficient (K) were 20.88 cm and 0.35 year,1, respectively. The growth performance index (,,) was calculated with 2.18. The growth pattern showed negative allometric growth (b < 3), with an asymptotic weight (W) of about 1124.6 g. The oyster attained an average length of 6.17 cm at the end of 1 year. Total mortality (Z) by length-converted catch curve was estimated at 1.78 year,1, fishing mortality (F) at 0.77 year,1, and natural mortality (M) at 1.01 year,1. The exploitation level (E) of C. madrasensis was 0.43, while the maximum allowable limit of exploitation (Emax) was 0.45 for the highest yield. The recruitment pattern was continuous, displaying a single major peak event per year. Habitat temperatures were 25.5,31.0°C (mean ± SD, 29 ± 1.62°C); salinity range was from 12.36 to 26.0 ppt (mean ± SD, 19.6 ± 4.7 ppt). The exploitation level (0.43) indicated that the oyster stock was exploited at almost maximum yield in this channel. [source] A study of antifungal antibiotic production by Thermomonospora sp MTCC 3340 using full factorial designJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 6 2003Monali Gupte Abstract The three independent variables, viz concentration of carbon source (glucose), concentration of nitrogen source (soybean meal) and temperature of incubation were found to be the most important for production of antifungal antibiotic by the isolate Thermomonospora sp MTCC 3340 from one-factor-at-a-time study. These variables were varied at three levels in a total number of 27 experiments designed using full factorial design. The results on analysis using the statistical software SPSS (version 6.0) indicated that the optimum combination of the three factors for the maximum yield of the antibiotic was concentration of carbon source (glucose) 2%, concentration of nitrogen source (soybean meal) 1% and temperature of incubation 30 °C. A close fit between experimental and predicted values of the antifungal yield was obtained using one of the modes derived from the statistical analysis, indicating that this model was applicable to this production. Copyright © 2003 Society of Chemical Industry [source] Syntheses of multicyclic poly(ether sulfone)s from 5,5,,6,6,-tetrahydroxy-3,3,3,,3,-tetramethyl spirobisindane and 4,4,-bis(4-chlorophenyl) sulfonesJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 11 2008Hans R. Kricheldorf Abstract 5,5,,6,6,-Tetrahydroxy-3,3,3,,3,-tetramethyl spirobisindane (TTSBI) was polycondensed with 4,4,-dichlorodiphenyl sulfone (DCDPS) or with 4,4,-bis(4-chlorophenyl sulfonyl) biphenyl (BCSBP) in DMSO. Concentration and feed ratio were optimized to avoid gelation and to obtain a maximum yield of multicyclic polyethers free of functional groups. Regardless of these reaction conditions, only low fractions of perfect multicycles were obtained from DCDPS apparently due to steric hindrance of ring closure. Under the same conditions high fractions of perfect multicycles were achieved with the longer and more flexible DCSBP. The reaction products were characterized by MALDI-TOF mass spectrometry, 1H-NMR spectroscopy viscosity, and DSC measurements. Relatively low glass transition temperatures (Tgs , 160,175 °C) were found. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 3732,3739, 2008 [source] Nitrogen fertilisation in coriander (Coriandrum sativum L.): a review and meta-analysisJOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 6 2009Alessandra Carrubba Abstract Nitrogen (N) fertilisation is one of the most important external inputs in assessing coriander seed yield and plant growth. Recent concerns related to the misuse of N fertilisers in agricultural environments, however, stress the opportunity for a fine-tuning of N management in order to optimise the use of this element, avoiding losses and reducing environmental hazards. In this study, some results from the literature concerning N fertilisation in coriander are reviewed and, by means of statistical analysis, an attempt is made to derive from them some general suggestions about practices of N fertilisation. In most cases examined, N fertilisation allowed a 10,70% increase in seed yields in comparison with each respective untreated control. The efficiency of use of this element, however, has proven to be greatly dependent on the overall fertility conditions of the growing site. The greatest yield advantages were actually found in more favourable environments, whereas in low-yielding environments plants reached their maximum yield with a comparatively reduced N supply. In low-yielding environments a careful risk/benefit assessment of this practice is therefore advisable. No definite conclusion could be drawn at this stage about essential oil yield and composition in relation to N fertilisation. Copyright © 2009 Society of Chemical Industry [source] Comparative study on the proteolytic activities and storage globulins in seeds of Theobroma grandiflorum (Willd ex Spreng) Schum and Theobroma bicolor Humb Bonpl, in relation to their potential to generate chocolate-like aromaJOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 7 2004Christoph Reisdorff Abstract The cocoa relatives T grandiflorum (cupuaçu) and T bicolor (macambo) are promising crop plants for sustainable agroforestry in the Amazon region of South America. The market for cupuaçu is expanding since the fruit flesh is utilised by the foodstuffs industry. Attempts to commercialise chocolate-like wares from the seeds have failed so far because of unreliable product quality. It is not known whether this is due to an insufficient aroma potential of cupuaçu seeds. We therefore investigated the proteolytic enzymes and the seed storage globulins which are both decisive for the formation of aroma precursors in cocoa. We found that the activities of the aspartic endopeptidase and the carboxypeptidase in T bicolor and T grandiflorum differed slightly from those in cocoa. The specificity of the carboxypeptidase for hydrophobic amino acids was quite similar across the three species, while the optimal pH of the T grandiflorum enzyme was lower than that of the other species. The qualitative and quantitative differences between the globulins indicate a lower maximum yield of aroma precursors in T grandiflorum and a higher maximum yield of aroma precursors in T bicolor, compared to cocoa. We conclude that the quality of chocolate-like products made from the studied cocoa relatives can be improved by adapting fermentation procedures to particular biochemical features of these seeds. Copyright © 2004 Society of Chemical Industry [source] Hydrolytic Degradation and Monomer Recovery of Poly(butylene succinate) and Poly(butylene succinate/adipate) in the MeltMACROMOLECULAR REACTION ENGINEERING, Issue 6 2008Hideto Tsuji Abstract Aliphatic dicarboxylic acid/aliphatic diol-derived polyesters, poly(butylene succinate) and poly(butylene succinate/adipate), have been hydrolytically degraded in the melt in high-temperature and high-pressure water over a wide temperature range of 180,300,°C for periods of up to 30 min. The formation/decomposition of succinic acid (SA), adipic acid (AA), and butane-1,4-diol (BD), plus the molecular weight change of PBS and PBSA were then investigated. SA and AA were recovered at maximum yields of 65,80%, whereas BD was recovered at a maximum yield of only 30%, probably because of its decomposition. The obtained results were compared with those reported for aliphatic hydroxycarboxylic acid-derived polyesters and aromatic dicarboxylic acid/aliphatic diol-derived polyesters. [source] Overcoming growing water scarcity: Exploring potential improvements in water productivity in IndiaNATURAL RESOURCES FORUM, Issue 3 2010Upali A. Amarasinghe Abstract Improvements in water productivity (WP) are often suggested as one of the alternative strategies for overcoming growing water scarcity in India. This paper explores the potential improvements in WP of food grains at district level, which currently varies between 0.11 and 1.01 kilogram per cubic metre (kg/m3), in the 403 districts that account for 98% of the total production of food grains. The paper first finds the maximum yield function conditional on consumptive water use (CWU) and then explores the potential improvements in WP by: (a) bridging the gap between actual and maximum yield while keeping CWU constant; and (b) changing the maximum yield by adjusting the CWU using supplementary or deficit irrigation. Deficit irrigation in some areas may decrease yield but can increase production if land availability is not a constraint. A large potential exists for bridging the yield gap in irrigated areas with CWU between 300 and 475 mm. Of the 222 districts that fall under this category, a 50% reduction in yield gap alone could increase production by 100 million tonnes (Mt) without increasing CWU. Supplementary irrigation can increase yield and WP in rain-fed and irrigated areas of 266 and 16 districts with CWU is below 300 mm. Deficit irrigation in irrigated areas of 185 districts with CWU above 475 mm could increase yield, WP and production. Decreasing CWU in irrigated areas with CWU between 425 and 475 mm reduces yield slightly, but if availability of land is not a constraint then the benefits due to water saving and production increases could exceed the cost. [source] Seasonal studies on the alginate and its biochemical composition I: Sargassum polycystum (Fucales), PhaeophyceaePHYCOLOGICAL RESEARCH, Issue 4 2003Sundararaju Jothi Saraswathi SUMMARY Investigations were made on the brown seaweed Sargassum polycystum C. Agardh collected from Rameswaram Coast, Tamil Nadu. The alginates extracted from ,leaf', ,stem' and entire thallus of S. polycystum were investigated for their viscosity and chemical constituents, namely ,-D-mannuronic acid (M-block), ,-L-guluronic acid (G-block) and alternating sequences of ,-D-mannuronic acid and ,-L-guluronic acid (MG-block) for six different seasons between August 1998 and November 1999. Significant seasonal variation (P< 0.05) was observed with high yield of alginate in February. The alginate extracted from the ,leaf' region showed a maximum yield whereas the ,stem' region exhibited maximum viscosity. The amount of G-block was found to be more than M- and MG-blocks in all the samples tested. The amount of G-block was high in ,stem' followed by leaf and entire thallus. A positive correlation was recorded between viscosity and G-block. Among the three alginates, the ratio of M/G was low in the ,stem' followed by ,leaf' and entire thallus. [source] Microwave-assisted extraction of total bioactive saponin fraction from Gymnema sylvestre with reference to gymnemagenin: a potential biomarkerPHYTOCHEMICAL ANALYSIS, Issue 6 2009Vivekananda Mandal Abstract Objective , To develop a fast and ecofriendly microwave assisted extraction (MAE) technique for the effective and exhaustive extraction of gymnemagenin as an indicative biomarker for the quality control of Gymnema sylvestre. Methodology , Several extraction parameters such as microwave power, extraction time, solvent composition, pre-leaching time, loading ratio and extraction cycle were studied for the determination of the optimum extraction condition. Scanning electron micrographs were obtained to elucidate the mechanism of extraction Results , The final optimum extraction conditions as obtained from the study were: 40% microwave power, 6,min irradiation time, 85% v/v methanol as the extraction solvent, 15,min pre-leaching time and 25,:,1 (mL/g) as the solvent-to-material loading ratio. The proposed extraction technique produced a maximum yield of 4.3% w/w gymnemagenin in 6,min which was 1.3, 2.5 and 1.95 times more efficient than 6,h of heat reflux, 24,h of maceration and stirring extraction, respectively. A synergistic heat and mass transfer theory was also proposed to support the extraction mechanism Conclusion , Comparison with conventional extraction methods revealed that MAE could save considerable amounts of time and energy, whilst the reduction of volume of organic solvent consumed provides an ecofriendly feature. Copyright © 2009 John Wiley & Sons, Ltd. [source] In vitro anti-adhesive activity of green tea extract against pathogen adhesionPHYTOTHERAPY RESEARCH, Issue 4 2009Ji-Hye Lee Abstract Camellia sinensis polysaccharide has been reported to possess anti-adhesive activity against pathogens. The present study was designed to investigate whether hot water extracts obtained from green tea leaves might inhibit pathogen adhesion to human or mouse cell lines. Green tea extract-4 (CSI-4) with the maximum yield of 4% (w/v) is composed of a major proportion of carbohydrates containing 40% uronic acids, but lack of catechins. It showed strong inhibitory activities against hemagglutination mediated by pathogens Helicobacter pylori, Propionibacterium acnes and Staphylococcus aureus with the minimum inhibitory concentrations of 0.01-0.5 mg/mL. CSI-4 further demonstrated an inhibitory effect on the adhesion of these pathogens to host cell lines with the IC50 values (50% inhibition of adhesion) of 0.14,2.3 mg/mL. It exhibited the highest activity against P. acnes, but no inhibitory effects were observed against Lactobacillus acidophilus, Bifidobacterium bifidum, Escherichia coli, or Staphylococcus epidermidis. Our results suggest that CSI-4 may exert a selective anti-adhesive effect against certain pathogenic bacteria with no adverse effects against beneficial or commensal bacteria. Copyright © 2008 John Wiley & Sons, Ltd. [source] Narrow rows reduce biomass and seed production of weeds and increase maize yieldANNALS OF APPLIED BIOLOGY, Issue 2 2009A.B. Mashingaidze Abstract Smallholder farmers in southern African countries rely primarily on cultural control and hoe weeding to combat weeds, but often times, they are unable to keep up with the weeding requirements of the crop because of its laboriousness, causing them to incur major yield losses. Optimisation of crop planting pattern could help to increase yield and suppress weeds and to reduce the critical period of weed control and the weeding requirements to attain maximum yield. Experiments were carried out in Zimbabwe during two growing seasons to assess the effect of maize density and spatial arrangement on crop yield, growth and seed production of weeds and to determine the critical period for weeding. Planting maize at 60 cm row distance achieved higher yields and better weed suppression than planting at 75 or 90 cm row distance. Increasing crop densities beyond the customary three to four plants m,2 gave modest reductions in weed biomass but also diminished crop yields, probably because of increased competition for water and nutrient resources. Maize planted in narrow rows (60 cm) intercepted more radiation and suffered less yield reduction from delaying hoe weeding than those planted in wider rows (75 or 90 cm), and the duration of the weed-free period required to attain maximum grain yield was 3 weeks shorter in the narrow spacing than that in the 75- and 90-cm row spacings. Weeding was more effective in curtailing weed seed production in the narrow row spatial arrangements than in the wide row planting. The results of these studies show that narrow row spacings may reduce weeding requirements and increase yields. [source] Optimal nitrogen supply as a key to increased and sustained production of a monoclonal full-size antibody in BY-2 suspension culture,BIOTECHNOLOGY & BIOENGINEERING, Issue 2 2010T. Holland Abstract Plant cell cultures have been used as expression hosts for recombinant proteins for over two decades. The quality of plant cell culture-produced proteins such as full-size monoclonal antibodies has been shown to be excellent in terms of protein folding and binding activity, but the productivity and yield fell short of what was achieved using mammalian cell culture, in which the key to gram-per-liter expression levels was strain selection and medium/process optimization. We carried out an extensive media analysis and optimization for the production of the full-size human anti-HIV antibody 2G12 in N. tabacum cv. BY-2. Nitrogen source and availability was found to be one key factor for the volumetric productivity of plant cell cultures. Increased amounts of nitrate in the culture medium had a dramatic impact on protein yields, resulting in a 10,20-fold increase in product accumulation through a combination of enhanced secretion and higher stability. The results were scalable from shake flasks to stirred-tank bioreactors, where the maximum yield per cultivation volume was 8,mg,L,1 over 7 days. During the stationary phase, antibody levels were 150-fold higher in nitrogen-enriched medium compared to standard medium. The enhanced medium appeared not to affect antibody quality and activity, as determined by Western blots, surface plasmon resonance binding assays and N -glycan analysis. Biotechnol. Bioeng. 2010;107: 278,289. © 2010 Wiley Periodicals, Inc. [source] Efficient synthesis of a long carbohydrate chain alkyl glycoside catalyzed by cyclodextrin glycosyltransferase (CGTase)BIOTECHNOLOGY & BIOENGINEERING, Issue 5 2009David Svensson Abstract Alkyl glycosides with long carbohydrate groups are surfactants with attractive properties but they are very difficult to synthesize. Here, a method for extension of the carbohydrate group of commercially available dodecyl-,- d -maltoside (DDM) is presented. DDM was converted to dodecyl-,- d -maltooctaoside (DDMO) in a single step by using a CGTase as catalyst and ,-cyclodextrin (,-CD) as glycosyl donor. The coupling reaction is under kinetic control and the maximum yield depends on the selectivity of the enzyme. The Bacillus macerans CGTase favored the coupling reaction while the Thermoanaerobacter enzyme also catalyzed disproportionation reactions leading to a broader product range. A high ratio ,-CD/DDM favored a high yield of DDMO and yields up to 80% were obtained using the B. macerans enzyme as catalyst. Biotechnol. Bioeng. 2009; 104: 854,861. © 2009 Wiley Periodicals, Inc. [source] Analysis of NADPH supply during xylitol production by engineered Escherichia coliBIOTECHNOLOGY & BIOENGINEERING, Issue 1 2009Jonathan W. Chin Abstract Escherichia coli strain PC09 (,xylB, cAMP-independent CRP (crp*) mutant) expressing an NADPH-dependent xylose reductase from Candida boidinii (CbXR) was previously reported to produce xylitol from xylose while metabolizing glucose [Cirino et al. (2006) Biotechnol Bioeng 95(6): 1167,1176]. This study aims to understand the role of NADPH supply in xylitol yield and the contribution of key central carbon metabolism enzymes toward xylitol production. Studies in which the expression of CbXR or a xylose transporter was increased suggest that enzyme activity and xylose transport are not limiting xylitol production in PC09. A constraints-based stoichiometric metabolic network model was used to understand the roles of central carbon metabolism reactions and xylose transport energetics on the theoretical maximum molar xylitol yield (xylitol produced per glucose consumed), and xylitol yields (YRPG) were measured from resting cell biotransformations with various PC09 derivative strains. For the case of xylose-proton symport, omitting the Zwf (glucose-6-phosphate dehydrogenase) or PntAB (membrane-bound transhydrogenase) reactions or TCA cycle activity from the model reduces the theoretical maximum yield from 9.2 to 8.8, 3.6, and 8.0 mol xylitol (mol glucose),1, respectively. Experimentally, deleting pgi (encoding phosphoglucose isomerase) from strain PC09 improves the yield from 3.4 to 4.0 mol xylitol (mol glucose),1, while deleting either or both E. coli transhydrogenases (sthA and pntA) has no significant effect on the measured yield. Deleting either zwf or sucC (TCA cycle) significantly reduces the yield from 3.4 to 2.0 and 2.3 mol xylitol (mol glucose),1, respectively. Expression of a xylose reductase with relaxed cofactor specificity increases the yield to 4.0. The large discrepancy between theoretical maximum and experimentally determined yield values suggests that biocatalysis is compromised by pathways competing for reducing equivalents and dissipating energy. The metabolic role of transhydrogenases during E. coli biocatalysis has remained largely unspecified. Our results demonstrate the importance of direct NADPH supply by NADP+ -utilizing enzymes in central metabolism for driving heterologous NADPH-dependent reactions, and suggest that the pool of reduced cofactors available for biotransformation is not readily interchangeable via transhydrogenase. Biotechnol. Bioeng. 2009;102: 209,220. © 2008 Wiley Periodicals, Inc. [source] Enzymatic production of ,- D -glucose-1-phosphate from trehaloseBIOTECHNOLOGY JOURNAL, Issue 9 2010Jef Van der Borght Abstract ,- D -Glucose-1-phosphate (,Glc1P) is an efficient glucosyl donor for both enzymatic and chemical glycosylation reactions but is currently very costly and not available in large amounts. This article provides an efficient production method of ,Glc1P from trehalose and phosphate using the thermostable trehalose phosphorylase from Thermoanaerobacter brockii. At the process temperature of 60°C, Escherichia coli expression host cells are lysed and cell treatment prior to the reaction is, therefore, not required. In this way, the theoretical maximum yield of 26% could be easily achieved. Two different purification strategies have been compared, anion exchange chromatography or carbohydrate removal by treatment with trehalase and yeast, followed by chemical phosphate precipitation. In a next step, ,Glc1P was precipitated with ethanol but this did not induce crystallization, in contrast to what is observed with other glycosylphosphates. After conversion of the product to its cyclohexylammonium salt, however, crystals could be readily obtained. Although both purification methods were quantitative (>99% recovery), a large amount of product (50%) was lost during crystallization. Nevertheless, a production process for crystalline ,Glc1P is now available from the cheap substrates trehalose and inorganic phosphate. [source] ,-Galactosidase from Lactobacillus pentosus: Purification, characterization and formation of galacto-oligosaccharidesBIOTECHNOLOGY JOURNAL, Issue 8 2010Thomas Maischberger Abstract A novel heterodimeric ,-galactosidase with a molecular mass of 105 kDa was purified from crude cell extracts of the soil isolate Lactobacillus pentosus KUB-ST10-1 using ammonium sulphate fractionation followed by hydrophobic interaction and affinity chromatography. The electrophoretically homogenous enzyme has a specific activity of 97 UoNPG/mg protein. The Km, kcat and kcat/Km values for lactose and o -nitrophenyl-,-D-galactopyranoside (oNPG) were 38 mM, 20 s -1, 530 M -1·s -1 and 1.67 mM, 540 s -1, 325 000 M -1·s -1, respectively. The temperature optimum of ,-galactosidase activity was 60,65°C for a 10-min assay, which is considerably higher than the values reported for other lactobacillal ,-galactosidases. Mg2+ ions enhanced both activity and stability significantly. L. pentosus ,-galactosidase was used for the production of prebiotic galacto-oligosaccharides (GOS) from lactose. A maximum yield of 31% GOS of total sugars was obtained at 78% lactose conversion. The enzyme showed a strong preference for the formation of ,-(1,3) and ,-(1,6) linkages, and the main transgalactosylation products identified were the disaccharides ,-D-Galp -(1,6)- D -Glc, ,-D-Galp -(1,3)- D -Glc, ,- D -Galp -(1,6)- D -Gal, ,- D -Galp -(1,3)- D -Gal, and the trisaccharides ,- D -Galp -(1,3)- D -Lac, ,- D -Galp -(1,6)- D -Lac. [source] High-throughput screening techniques for rapid PEG-based precipitation of IgG4 mAb from clarified cell culture supernatantBIOTECHNOLOGY PROGRESS, Issue 3 2010Carol Knevelman Abstract Locating optimal protein precipitation conditions for complex biological feed materials is problematic. This article describes the application of a series of high-throughput platforms for the rapid identification and selection of conditions for the precipitation of an IgG4 monoclonal antibody (mAb) from a complex feedstock using only microliter quantities of material. The approach uses 96-microwell filter plates combined with high-throughput analytical methods and a method for well volume determination for product quantification. The low material, time and resource requirements facilitated the use of a full factorial Design of Experiments (DoE) for the rapid investigation into how critical parameters impact the IgG4 precipitation. To aid the DoE, a set of preliminary range-finding studies were conducted first. Data collected through this approach describing Polyethylene Glycol (PEG) precipitation of the IgG4 as a function of mAb concentration, precipitant concentration, and pH are presented. Response surface diagrams were used to explore interactions between parameters and to inform selection of the most favorable conditions for maximum yield and purification. PEG concentrations required for maximum yield and purity were dependant on the IgG4 concentration; however, concentrations of 14 to 20% w/v, pH 6.5, gave optimal levels of yield and purity. Application of the high-throughput approach enabled 1,155 conditions to be examined with less than 1 g of material. The level of insights gained over such a short time frame is indicative of the power of microwell experimentation in allowing the rapid identification of appropriate processing conditions for key bioprocess operations. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2010 [source] Modulation of Phosphoenolpyruvate Synthase Expression Increases Shikimate Pathway Product Yields in E. coliBIOTECHNOLOGY PROGRESS, Issue 6 2002Jian Yi Product yields in microbial synthesis are ultimately limited by the mechanism utilized for glucose transport. Altered expression of phosphoenolpyruvate synthase was examined as a method for circumventing these limits. Escherichia coli KL3/pJY1.216A was cultured under fed-batch fermentor conditions where glucose was the only source of carbon for the formation of microbial biomass and the synthesis of product 3-dehydroshikimic acid. Shikimate pathway byproducts 3-deoxy- d - arabino -heptulosonic acid, 3-dehydroquinic acid, and gallic acid were also generated. An optimal expression level of phosphoenolpyruvate synthase was identified, which did not correspond to the highest expression levels of this enzyme, where the total yield of 3-dehydroshikimic acid and shikimate pathway byproducts synthesized from glucose was 51% (mol/mol). For comparison, the theoretical maximum yield is 43% (mol/mol) for synthesis of 3-dehydroshikimic acid and shikimate pathway byproducts from glucose in lieu of amplified expression of phosphoenolpyruvate synthase. [source] Investigation of the Mechanism of Colloidal Silicalite-1 Crystallization by Using DLS, SAXS, and 29Si NMR Spectroscopy,CHEMISTRY - A EUROPEAN JOURNAL, Issue 9 2010Alexander Aerts Dr. Abstract Colloidal silicalite-1 zeolite was crystallized from a concentrated clear sol prepared from tetraethylorthosilicate (TEOS) and aqueous tetrapropylammonium hydroxide (TPAOH) solution at 95,°C. The silicate speciation was monitored by using dynamic light scattering (DLS), synchrotron small-angle X-ray scattering (SAXS), and quantitative liquid-state 29Si NMR spectroscopy. The silicon atoms were present in dissolved oligomers, two discrete nanoparticle populations approximately 2 and 6,nm in size, and crystals. On the basis of new insight into the evolution of the different nanoparticle populations and of the silicate connectivity in the nanoparticles, a refined crystallization mechanism was derived. Upon combining the reagents, different types of nanoparticles (ca. 2 nm) are formed. A fraction of these nanoparticles with the least condensed silicate structure does not participate in the crystallization process. After completion of the crystallization, they represent the residual silicon atoms. Nanoparticles with a more condensed silicate network grow until approximately 6,nm and evolve into building blocks for nucleation and growth of the silicalite-1 crystals. The silicate network connectivity of nanoparticles suitable for nucleation and growth increasingly resembles that of the final zeolite. This new insight into the two classes of nanoparticles will be useful to tune the syntheses of silicalite-1 for maximum yield. [source] Polymerization of n -phenyl maleimide by lanthanide complexesJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 17 2005Bei Zhao Abstract N -Phenyl maleimide (N -PMI) was successfully polymerized by divalent rare-earth complexes (ArO)2Sm(THF)4 (ArO = 2,6-di- tert -butyl-4-methyl phenoxo-; THF = tetrahydrofuran) and (Ar,O)2Ln(THF)3 (Ar,O = 2,6-di- tert -butyl phenoxo-; Ln = Sm, Yb, or Eu). The central metals greatly affected the reactivity, and the reactivity order was Sm(II) > Yb(II) > Eu(II). The activity of (Ar,O)2Sm(THF)3 was higher than that of (ArO)2Sm(THF)4. The polymerization yields were higher in THF than in other solvents, and the maximum yields were obtained around 25 °C. A proposed mechanism is discussed. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3966,3972, 2005 [source] Performance of electrospun nanofibers for SPE of drugs from aqueous solutionsJOURNAL OF SEPARATION SCIENCE, JSS, Issue 18 2008Xue-jun Kang Abstract A novel extraction technique was reported. The solid phase material, nanofiber, was prepared by electrospinning using polystyrene. Twenty different drugs (10 ,g/L in water) were extracted using 1 mg of nanofibers within 5 min. The analytes can be desorpted from the fibers with 50 ,L of the methanol and then monitored by LC coupled to a UV detector. Packed-fiber SPE (PFSPE) provide high recoveries (>50%) for some relatively non-polar drugs (log P >1.5) (n -octanol-to-water partition ratio), and relatively low recoveries (9.9,39.8%) for the drugs within the log P window below 1. Experimental optimization of the technique has been carried out using seven representative drugs, edaravone, cinchonine, quinine, voriconazole, chlordiazepoxide, verapamil, and rutonding. Except for edaravone, the maximum yields of seven drugs (0.2 ,g/L) from water samples were approximately 100%, and were 33.7,88.2% from human plasma. The advantageous aspect of the technique encompasses high throughput, high sensitivity, simplicity, low cost, and green chemistry. [source] Hydrolytic Degradation and Monomer Recovery of Poly(butylene succinate) and Poly(butylene succinate/adipate) in the MeltMACROMOLECULAR REACTION ENGINEERING, Issue 6 2008Hideto Tsuji Abstract Aliphatic dicarboxylic acid/aliphatic diol-derived polyesters, poly(butylene succinate) and poly(butylene succinate/adipate), have been hydrolytically degraded in the melt in high-temperature and high-pressure water over a wide temperature range of 180,300,°C for periods of up to 30 min. The formation/decomposition of succinic acid (SA), adipic acid (AA), and butane-1,4-diol (BD), plus the molecular weight change of PBS and PBSA were then investigated. SA and AA were recovered at maximum yields of 65,80%, whereas BD was recovered at a maximum yield of only 30%, probably because of its decomposition. The obtained results were compared with those reported for aliphatic hydroxycarboxylic acid-derived polyesters and aromatic dicarboxylic acid/aliphatic diol-derived polyesters. [source] Batch solvent extraction of flavanolignans from milk thistle (Silybum marianum L. Gaertner)PHYTOCHEMICAL ANALYSIS, Issue 1 2005Sunny N. Wallace Abstract Seeds of milk thistle (Silybum marianum L. Gaertner) contain silymarins and ca. 25% (w/w) of oil. A pre-treatment step involving re,uxing with petroleum ether is usually performed before extraction of the silymarins using organic solvents. This paper compares the extraction of whole and defatted milk thistle seeds in various solvents as a function of temperature. The extraction of whole seeds of milk thistle with water at 50, 70 and 85°C was also examined: the yield of silymarin increased with increasing water temperature. In most cases, ethanol at 60°C recovered the largest quantities of silymarins. However, boiling water proved to be an ef,cient extraction solvent for the more polar silymarins such as taxifolin and silychristin, even when using whole seeds. Extractions of defatted seed meal with boiling ethanol returned maximum yields of 0.62, 3.89, 4.04, and 6.86 mg/g defatted seed of taxifolin, silychristin, silybinin A and silybinin B, respectively. When extracting defatted seed meal with ethanol, yields of taxifolin, silybinin A and silybinin B were, respectively, 6.8-, 0.95-, 1.7- and 1.6-fold higher than when extracting whole seeds. When extracting with boiling water, the yields of silychristin, silybinin A, and silybinin B were 380, 47 and 50% higher for whole seeds compared with defatted seeds. Copyright © 2005 John Wiley & Sons, Ltd. [source] | |||||||||||||||||||