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Biomass Yield (biomass + yield)
Selected AbstractsPhysiological behaviour of Hanseniaspora guilliermondii in aerobic glucose-limited continuous culturesFEMS YEAST RESEARCH, Issue 2 2003Helena Albergaria Abstract The physiology of Hanseniaspora guilliermondii was studied under aerobic glucose-limited conditions using the accelerostat procedure (continuous acceleration of dilution rate) and classical chemostat cultures. By both cultivation techniques this yeast was found to be Crabtree-positive. Up to a dilution rate of 0.25 h,1, glucose was completely metabolised into biomass, glycerol and carbon dioxide. Above this value, an increase in the dilution rate was accompanied by the production of other metabolites like ethanol, acetic and malic acids. Biomass yield during the purely oxidative growth was 0.49 g g,1 and decreased to 0.26 g g,1 for D=0.34 h,1. A maximal specific ethanol production rate of 1.36 mmol g,1 h,1 and a maximal ethanol yield of 0.05 g g,1 were achieved at D=0.34 h,1. [source] Poplar as a feedstock for biofuels: A review of compositional characteristicsBIOFUELS, BIOPRODUCTS AND BIOREFINING, Issue 2 2010Poulomi Sannigrahi Abstract The growing demand for transportation fuels, along with concerns about the harmful effects of greenhouse gas emissions from the burning of fossil fuels, has assured a viable future for the development of alternative fuels from renewable resources, such as lignocellulosic biomass. The efficient utilization of these biomass resources is critically dependant on the in-depth knowledge of their chemical constituents. This, together with the desired fuel properties, helps tailor the chemical and/or enzymatic processes involved in converting biomass to biofuels. Hybrid poplars are among the fastest growing temperate trees in the world and a very promising feedstock for biofuels and other value-added products. Sequencing of the poplar genome has paved the way for tailoring new cultivars and clones optimized for biofuels production. Our objective is to review published research on the composition of the key chemical constituents of hybrid poplar species used for biofuels. Biomass yields, elemental composition, carbohydrate and lignin content and composition are some of the characteristics reviewed, with emphasis on lignin structure. Genetic modifications used to alter lignin content and composition, with the aim of improving biofuels yields, are also examined. Copyright © 2010 Society of Chemical Industry and John Wiley & Sons, Ltd [source] Bioreactor for cultivation of red beet hairy roots and in situ recovery of primary and secondary metabolitesENGINEERING IN LIFE SCIENCES (ELECTRONIC), Issue 3 2009Bhagyalakshmi Neelwarne Abstract To arrive at an appropriate bioreactor design and in situ recovery of the products, red beet hairy roots were used as a model system where the levels of betalain pigments (betacyanins and betaxanthins) were followed as secondary metabolite and the peroxidase enzyme as primary metabolite. Medium volume and other kinetic parameters were found to play significant roles by way of directly affecting the biomass yield rather than a specific metabolite. The hydrodynamic stress created on the roots by large culture volume could be minimized by pulse-feeding of medium in shake-flasks; and by separating the biomass chamber from the aerated medium reservoir in circulatory fed-batch bioreactor. Accordingly the bioreactor was modified to provide anchorage and air-enrichment chamber which resulted in higher formation of both the metabolites than in shake-flasks. Various down-stream processing aspects such as in situ release of pigments by non-destructive methods, followed by adsorption through a column and recovery by desorption were optimized for betalains. A strategy for simultaneous recovery of pigment and peroxidase was worked out using aqueous two phase extraction (ATPE). [source] Hexavalent uranium supports growth of Anaeromyxobacter dehalogenans and Geobacter spp. with lower than predicted biomass yieldsENVIRONMENTAL MICROBIOLOGY, Issue 11 2007Robert A. Sanford Summary The stimulation of bacteria capable of reducing soluble U(VI) to sparingly soluble U(IV) is a promising approach for containing U(VI) plumes. Anaeromyxobacter dehalogenans is capable of mediating this activity; however, its ability to couple U(VI) reduction to growth has not been established. Monitoring the increase in 16S rRNA gene copy numbers using quantitative real-time PCR (qPCR) in cultures provided with U(VI) as an electron acceptor demonstrated growth, and 7.7,8.6 × 106 cells were produced per ,mole of U(VI) reduced. This biomass yield was lower than predicted based on the theoretical free energy changes associated with U(VI)-to-U(IV) reduction. Lower than predicted growth yields with U(VI) as electron acceptor were also determined in cultures of Geobacter lovleyi and Geobacter sulfurreducens suggesting that U(VI) reduction is inefficient or imposes an additional cost to growing cells. These findings have implications for U(VI) bioremediation because Anaeromyxobacter spp. and Geobacter spp. contribute to radionuclide immobilization in contaminated subsurface environments. [source] Role of reserve carbohydrates in the growth dynamics of Saccharomyces cerevisiae,FEMS YEAST RESEARCH, Issue 8 2004Vincent Guillou Abstract The purpose of this study was to explore the role of glycogen and trehalose in the ability of Saccharomyces cerevisiae to respond to a sudden rise of the carbon flux. To this end, aerobic glucose-limited continuous cultures were challenged with a sudden increase of the dilution rate from 0.05 to 0.15 h,1. Under this condition, a rapid mobilization of glycogen and trehalose was observed which coincided with a transient burst of budding and a decrease of cell biomass. Experiments carried out with mutants defective in storage carbohydrates indicated a predominant role of glycogen in the adaptation to this perturbation. However, the real importance of trehalose in this response was veiled by the unexpected phenotypes harboured by the tps1 mutant, chosen for its inability to synthesize trehalose. First, the biomass yield of this mutant was 25% lower than that of the isogenic wild-type strain at dilution rate of 0.05 h,1, and this difference was annulled when cultures were run at a higher dilution rate of 0.15 h,1. Second, the tps1 mutant was more effective to sustain the dilution rate shift-up, apparently because it had a faster glycolytic rate and an apparent higher capacity to consume glucose with oxidative phosphorylation than the wild type. Consequently, a tps1gsy1gsy2 mutant was able to adapt to the dilution rate shift-up after a long delay, likely because the detrimental effects from the absence of glycogen was compensated for by the tps1 mutation. Third, a glg1,glg2, strain, defective in glycogen synthesis because of the lack of the glycogen initiation protein, recovered glycogen accumulation upon further deletion of TPS1. This recovery, however, required glycogen synthase. Finally, we demonstrated that the rapid breakdown of reserve carbohydrates triggered by the shift-up is merely due to changes in the concentrations of hexose-6-phosphate and UDPglucose, which are the main metabolic effectors of the rate-limiting enzymes of glycogen and trehalose pathways. [source] A quantitative review comparing the yield of switchgrass in monocultures and mixtures in relation to climate and management factorsGCB BIOENERGY, Issue 1 2010DAN WANG Abstract Switchgrass (Panicum virgatum L.), a US Department of Energy model species, is widely considered for US biomass energy production. While previous studies have demonstrated the effect of climate and management factors on biomass yield and chemical characteristics of switchgrass monocultures, information is lacking on the yield of switchgrass grown in combination with other species for biomass energy. Therefore, the objective of this quantitative review is to compare the effect of climate and management factors on the yield of switchgrass monocultures, as well as on mixtures of switchgrass, and other species. We examined all peer-reviewed articles describing productivity of switchgrass and extracted dry matter yields, stand age, nitrogen fertilization (N), temperature (growing degree days), and precipitation/irrigation. Switchgrass yield was greater when grown in monocultures (10.9 t ha,1, n=324) than when grown in mixtures (4.4 t ha,1, n=85); yield in monocultures was also greater than the total yield of all species in the mixtures (6.9 t ha,1, n=90). The presence of legume species in mixtures increased switchgrass yield from 3.1 t ha,1 (n=65) to 8.9 t ha,1 (n=20). Total yield of switchgrass-dominated mixtures with legumes reached 9.9 t ha,1 (n=25), which was not significantly different from the monoculture yield. The results demonstrated the potential of switchgrass for use as a biomass energy crop in both monocultures and mixtures across a wide geographic range. Monocultures, but not mixtures, showed a significant positive response to N and precipitation. The response to N for monocultures was consistent for newly established (stand age <3 years) and mature stands (stand age ,3 years) and for lowland and upland ecotypes. In conclusion, these results suggest that fertilization with N will increase yield in monocultures, but not mixtures. For monocultures, N treatment need not be changed based on ecotype and stand age; and for mixtures, legumes should be included as an alternative N source. [source] Comparative Effect of Nitrogen Sources on Maize under Saline and Non-saline ConditionsJOURNAL OF AGRONOMY AND CROP SCIENCE, Issue 4 2008M. Irshad Abstract The main objective of this study was to compare the relationship between biomass yield and nutrient uptake in salt-stressed maize (Zea mays L.) following nitrogen (N) nutrition in a greenhouse. Three forms of N were applied, each at the rate of 100 kg ha,1: urea-N, nitrate-N, 1/2 urea-N + 1/2 nitrate-N (mixed-N) and no N application (control). Maize was grown as a test crop for 6 weeks. All N sources greatly stimulated crop growth and nutrient uptake compared with the control. The biomass (shoot and root) of maize was significantly greater in mixed-N treatment than in single sources in saline soil whereas it varied in the order of urea-N > mixed-N > nitrate-N > control in non-saline soil. Under both soil conditions, the concentration of Ca, Mg and Na in shoot was highest in nitrate-N treatments while that of K was highest in the control. Shoot nitrogen concentration was not significantly different among N sources under non-saline treatment, whereas under saline conditions, the concentration varied markedly in the order of nitrate-N > urea-N > mixed-N > control. The mineral concentrations in the shoot increased under salt treated soil when compared with non-saline soil. The ratios of Na/K, Na/Ca and Na/Mg were also higher under salt stress due to higher accumulation of Na ion in the shoot. Among N-fertilizer sources, Na/Ca and Na/Mg ratios were highest in control whereas Na/K ratio was the highest in nitrate-N treatment. The lowest cation ratios were noted in mixed-N-treated plants under both soils. Regression analysis showed that maize biomass was related to N concentration by the following equations: Y = ,4.54 + 0.97N for the non-saline soil and Y = 0.89 + 0.25N for the saline soil. Nitrogen use efficiency for non-saline soil exceeded that of saline soil by 15 %. [source] Fluid biomulching based on poly(vinyl alcohol) and fillers from renewable resourcesJOURNAL OF APPLIED POLYMER SCIENCE, Issue 1 2008E. Chiellini Abstract This article reports on the results obtained in an investigation on the application of biodegradable polymeric materials in the agricultural practice of mulching. Particular attention has been devoted to the effect of biobased mulching films generated in situ by low-pressure spraying of polymeric water dispersions on the various cultivars. In a field trial, the effectiveness of the hydromulching (liquid-mulching) technique was assessed by the monitoring of the growth and yield of lettuce and corn, which were used as reference plants. Conventional plastic films and straw mulching (SM) were compared with liquid-mulching treatments based on poly(vinyl alcohol) and natural fillers derived from agroindustrial wastes (sugar cane bagasse, wheat flour, saw dust, and wheat straw). An improvement of the biomass yield of the two selected plants with respect to conventional polyethylene mulching was attained in various liquid-mulching formulations with positive effects on the maintenance of soil structure. Alternative fluid-mulching treatments based on biodegradable components were effective in preserving soil aggregates and improving some crop growth parameters. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Fermentation of enzymatic hydrolysates from olive stones by Pachysolen tannophilusJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 3 2009Manuel Cuevas Abstract BACKGROUND: Olive stones were pretreated with liquid hot water (LHW or autohydrolysis) at maximum temperatures between 175 and 225 °C (severity factors, logR0, between 2.73 and 4.39) to be subjected (both liquid and solid components) afterwards to enzymatic hydrolysis with cellulases from Trichoderma viride. Ethanol fermentation of hydrolysates was performed with the non-traditional yeast Pachysolen tannophilus ATCC 32691. RESULTS: After the enzymatic step, yields of hemicellulose solubilization reached 100%, while the cellulose was only partially hydrolysed (23%, logR0 = 4.39). The maximum yields in total reducing sugars and acetic acid, at the upper end of the severity range, was close to 0.25 and 0.04 g g,1 dry stone, respectively. During the fermentation stage, the increase in R0 reduced the maximum specific growth rate, biomass productivity, and overall biomass yield. The overall yields of ethanol and xylitol ranged, respectively, from 0.18 to 0.25 g g,1 and from 0.01 to 0.13 g g,1. CONCLUSIONS: The results demonstrate the possibility of producing ethanol from olive stones, making use of the cellulose and hemicellulose fraction of the waste. It was confirmed that the overall yield in xylitol strongly depended on severity factor, while the overall yield in ethanol remained practically constant for all the pretreatment conditions tested. Copyright © 2008 Society of Chemical Industry [source] Clonal variation in morphological and physiological responses to irradiance and photoperiod for the aquatic angiosperm Potamogeton pectinatusJOURNAL OF ECOLOGY, Issue 5 2002Jörn Pilon Summary 1Widely distributed plants are exposed to contrasting gradients in irradiance and photoperiod across latitude. We investigated the relative contribution of local specialization and phenotypic plasticity to variation in plant growth for three clones of the aquatic angiosperm Potamogeton pectinatus L., originating from 42.5 to 68° N. Plants were grown at a factorial combination of two irradiances (50 and 350 µmol m,2 s,1) and three photoperiods (13, 16 and 22 h) and morphology, gas-exchange rate and biomass accumulation were recorded. 2The overall response to variation in irradiance and photoperiod was similar for all three clones. 3Differences in irradiance resulted in strong acclimative changes in morphological and physiological characteristics. At low irradiance, pronounced vertical shoot extension compensated for the limited plasticity in leaf area production, while photosynthetic capacity, apparent quantum yield and total chlorophyll concentration increased. As a result, biomass yield at the end of the experimental period was similar in both treatments. 4A decrease in photoperiod also resulted in plastic changes in morphology (increase of leaf biomass per unit plant biomass) and physiology (increase of photosynthetic capacity). However, these acclimative responses did not fully compensate for differences in photoperiod, since biomass was significantly lower under 13 and 16 h photoperiods than at 22 h. 5P. pectinatus is therefore phenotypically plastic, rather than locally specialized to differences in irradiance and photoperiod. [source] Effects of potassium carbonate as an alternative de-icer on ground vegetation and soilANNALS OF APPLIED BIOLOGY, Issue 3 2000E ERHART Summary The effects of the new de-icer potassium carbonate on the growth and species composition of a mixed sward and on the pH and electrical conductivity of the soil were examined in a four-year field trial and compared with sodium chloride. There were small positive effects of K2CO3 on the biomass yield of the sward at application rates up to 200 g m,2 yr,1, while effects were less negative than those of NaCl at annual application rates of 200 , 400 g m,2 yr,1. The species composition of the sward changed considerably with K2CO3 application, Agropyron repens becoming the dominant species. The pH was elevated slightly more by K2CO3 than by NaCl application. Electrical conductivity as an index of soil salinity was increased by both de-icers. K2CO3 was more adsorbed to soil colloids than NaCl, so that the rise in E.C. resulting from application of the former was restricted to the uppermost 10 cm of soil. [source] Sources and bioavailability of phosphorus fractions in freshwaters: a British perspectiveBIOLOGICAL REVIEWS, Issue 1 2001C. S. REYNOLDS ABSTRACT This paper seeks a perspective on the forms of phosphorus which promote aquatic eutrophication, with the particular quest of establishing their sources. A short background traces the development of understanding of nutrient enrichment and the suppositions about the relative contributions of agriculture, sewage and detergent residues. Most aquatic systems, and their primary producers, are naturally deficient in biologically-available phosphorus. Aquatic plants have evolved very efficient phosphorus uptake mechanisms. The biomass responses to an increase in the supply of phosphorus are stoichiometrically predictable. The most bioavailable forms of phosphorus are in solution, as orthophosphate ions, or are readily soluble or elutable from loose combinations. Ready bioavailability coincides well with what is measurable as molybdate-reactive (MRP) or soluble-reactive phosphorus (SRP). Most other forms, including phosphates of the alkaline earth metals, aluminium and iron are scarcely available at all. Orthophosphate ions sorbed to metal oxides and hydroxides are normally not biologically available either, except through weak dissociation (,desorption'). The production of alkaline phosphatase provides organisms with an additional mechanism for accelerating the sequestration of phosphate from organic compounds. Bioavailable phosphate is liberated when redox- or alkali-sensitive metal hydroxides dissolve but these processes are minor contributors to the biological responses to nutrient enrichment. Most of the familiar eutrophication is attributable to the widespread application of secondary sewage treatment methods to the wastes emanating from a burgeoning and increasingly urbanised human population. The use of polyphosphate-based detergents, now in decline, has contributed to the problem. In aquatic systems, the additional phosphorus raises the biological supportive capacity, sometimes to the capacity of the next limiting factor (carbon, light, hydraulic retention or of another nutrient). At high orthophosphate loadings, the straight stoichiometric yield relationship between biomass yield and phosphorus availability is lost. Movements of phosphorus and its recycling within aquatic systems do not prevent the slow gravitation of phosphorus to the bottom substrata. The phosphorus retentivity of sediments depends upon their chemical composition. While oxide-hydroxide binding capacity in the surface sediments persists, they act as a sink for phosphorus and a control on further cycling. Iron-rich and clay-rich sediments perform best in these conditions; calcareous sediments least so. Eutrophication may lead to the exhaustion of sediment P-binding capacity. Non-sorbed phosphate is readily recyclable if primary producers have access to it. Recycling is most rapid in shallow waters (where sediment disturbance, by flow, by wind action and through bioturbation, is frequent) and least in deep ventilated sediments. The contributions of phosphorus from catchments are assessed. The slow rate of weathering of (mostly apatitic) minerals, the role of chemical binding in soils and the incorporation and retentivity by forested terrestrial ecosystems each contribute to the minimisation of phosphorus leakage to drainage waters. Palaeolimnological and experimental evidence confirms that clearance of land and ploughing its surface weakens the phosphorus retentivity of catchments. The phosphorus transferred from arable land to drainage remains dominated by sorbed fractions which are scarcely bioavailable. Some forms of intensive market gardening or concentrated stock rearing may mobilise phosphates to drainage but it is deduced that drainage from agricultural land is not commonly a major source of readily bioavailable phosphorus in water. Careful budgeting of the phosphates in run-off from over-fertilised soils may nevertheless show that a proportionately small loss of bioavailable phosphorus can still be highly significant in promoting aquatic plant production. The bioavailable-phosphorus (BAP) load achieving the OECD threshold of lake eutrophy (35 mg P m,3) is calculated to be equivalent to a terrestrial loss rate of approximately 17.5 kg BAP km,2 year,1), or only 1,2% of a typical fertiliser application. The output is shown to be comparable with the P yield from secondary treatment of the sewage produced by a resident population of 30,44 persons km,2. With tertiary treatment, the equivalence is with approximately 200 persons km,2. [source] Metabolic and transcriptional response of recombinant Escherichia coli to elevated dissolved carbon dioxide concentrationsBIOTECHNOLOGY & BIOENGINEERING, Issue 1 2009Antonino Baez Abstract The effect of dissolved carbon dioxide (dCO2) concentration on the stoichiometric and kinetic constants and by-product accumulation was determined for Escherichia coli cells producing recombinant green fluorescent protein (GFP). Constant dCO2, in the range of 20,300,mbar, was maintained during batch cultures by manipulating the inlet gas composition. As dCO2 increased, specific growth rate (µ) decreased, and acetate accumulation and the time for onset of GFP production increased. Maximum biomass yield on glucose and GFP concentration were affected for dCO2 above 70 and 150,mbar, respectively. Expression analysis of 16 representative genes showed that E. coli can respond at the transcriptional level upon exposure to increasing dCO2, and revealed possible mechanisms responsible for the detrimental effects of high dCO2. Genes studied included those involved in decarboxylation reactions (aceF, icdA, lpdA, sucA, sucB), genes from pathways of production and consumption of acetate (ackA, poxB, acs, aceA, fadR), genes from gluconeogenic and anaplerotic metabolism (pckA, ppc), genes from the acid resistance (AR) systems (adiA, gadA, gadC), and the heterologous gene (gfp). The transcription levels of tricarboxylic acid (TCA) cycle genes (icdA, sucA, sucB) and glyoxylate shunt (aceA) decreased as dCO2 increased, whereas fadR (that codes for a negative regulator of the glyoxylate operon) and poxB (that codes for PoxB which is involved in acetate production from pyruvate) were up-regulated as dCO2 increased up to 150,mbar. Furthermore, transcription levels of genes from the AR systems increased as dCO2 increased up to 150,mbar, indicating that elevated dCO2 triggers an acid stress response in E. coli cells. Altogether, such results suggest that the increased acetate accumulation and reduction in µ, biomass yield and maximum GFP concentration under high dCO2 resulted from a lower carbon flux to TCA cycle, the concomitant accumulation of acetyl-CoA or pyruvate, and the acidification of the cytoplasm. Biotechnol. Bioeng. 2009; 104: 102,110 © 2009 Wiley Periodicals, Inc. [source] A hidden square-root boundary between growth rate and biomass yieldBIOTECHNOLOGY & BIOENGINEERING, Issue 1 2009Wilson W. Wong Abstract Although the theoretical value of biomass yield can be calculated from metabolic network stoichiometry, the growth rate is difficult to predict. Since the rate and yield can vary independently, no simple relationship has been discovered between these two variables. In this work, we analyzed the well-accepted enzyme kinetics and uncovered a hidden boundary for growth rate, which is determined by the square-root of three physiological parameters: biomass yield, the substrate turnover number, and the maximum synthesis rate of the turnover enzyme. Cells cannot grow faster than the square-root of the product of these parameters. This analysis is supported by experimental data and involves essentially no assumptions except (i) the cell is not undergoing a downshift transition, (ii) substrate uptake enzyme activity is proportional to its copy number. This simple boundary (not correlation) has escaped notice for many decades and suggests that the yield calculation does not predict the growth rate, but gives an upper limit for the growth rate. The relationship also explains how growth rate is affected by the yield and sheds lights on strain design for product formation. Biotechnol. Bioeng. 2009;102: 73,80. © 2008 Wiley Periodicals, Inc. [source] Expression of Aspergillus hemoglobin domain activities in Aspergillus oryzae grown on solid substrates improves growth rate and enzyme productionBIOTECHNOLOGY JOURNAL, Issue 7-8 2006Rob te Biesebeke Dr. Abstract DNA fragments coding for hemoglobin domains (HBD) were isolated from Aspergillus oryzae and Aspergillus niger. The HBD activities were expressed in A. oryzae by introduction of HBD gene fragments under the control of the promoter of the constitutively expressed gpdA gene. In the transformants, oxygen uptake was significantly higher, and during growth on solid substrates the developed biomass was at least 1.3 times higher than that of the untransformed wild-type strain. Growth rate of the HBD-activity-producing strains was also significantly higher compared to the wild type. During growth on solid cereal substrates, the amylase and protease activities in the extracts of the HBD-activity-producing strains were 30,150% higher and glucoamylase activities were at least 9 times higher compared to the wild-type strain. These results suggest that the Aspergillus HBD-encoding gene can be used in a self-cloning strategy to improve biomass yield and protein production of Aspergillus species. [source] Packed Bed Column Fermenter and Kinetic Modeling for Upgrading the Nutritional Quality of Coffee Husk in Solid-State FermentationBIOTECHNOLOGY PROGRESS, Issue 6 2001Débora Brand Studies were carried out to evaluate solid-state fermentation (SSF) for the upgradation of the nutritional quality of coffee husk by degrading the caffeine and tannins present in it. SSF was carried out by Aspergillus niger LPBx in a glass column fermenter using factorial design experiments and surface response methodology to optimize bioprocess parameters such as the substrate pH and moisture content and aeration rate. The first factorial design showed that the moisture content of the substrate and aeration rate were significant factors for the degradation of toxic compounds, which was confirmed by the second factorial design too. The kinetic study showed that the degradation of toxic compounds was related to the development of the mold and its respiration and also to the consumption of the reducing sugars present in coffee husk. From the values obtained experimentally for the oxygen uptake rate and CO2 evolved, the system determined a biomass yield (Yx/o) of 3.811 (g of biomass)·(g of consumed O2),1 and a maintenance coefficient (m) of 0.0031 (g of consumed O2)·(g biomass of biomass),1·h,1. The best results on the degradation of caffeine (90%) and tannins (57%) were achieved when SSF was carried out with a 30 mL·min,1 aeration rate using coffee husk having a 55% initial moisture content. The inoculation rate did not affect the metabolization of the toxic compounds by the fungal culture. After SSF, the protein content of the husk was increased to 10.6%, which was more than double that of the unfermented husk (5.2%). [source] Hexavalent uranium supports growth of Anaeromyxobacter dehalogenans and Geobacter spp. with lower than predicted biomass yieldsENVIRONMENTAL MICROBIOLOGY, Issue 11 2007Robert A. Sanford Summary The stimulation of bacteria capable of reducing soluble U(VI) to sparingly soluble U(IV) is a promising approach for containing U(VI) plumes. Anaeromyxobacter dehalogenans is capable of mediating this activity; however, its ability to couple U(VI) reduction to growth has not been established. Monitoring the increase in 16S rRNA gene copy numbers using quantitative real-time PCR (qPCR) in cultures provided with U(VI) as an electron acceptor demonstrated growth, and 7.7,8.6 × 106 cells were produced per ,mole of U(VI) reduced. This biomass yield was lower than predicted based on the theoretical free energy changes associated with U(VI)-to-U(IV) reduction. Lower than predicted growth yields with U(VI) as electron acceptor were also determined in cultures of Geobacter lovleyi and Geobacter sulfurreducens suggesting that U(VI) reduction is inefficient or imposes an additional cost to growing cells. These findings have implications for U(VI) bioremediation because Anaeromyxobacter spp. and Geobacter spp. contribute to radionuclide immobilization in contaminated subsurface environments. [source] Forage and biomass feedstock production from hybrid forage sorghum and sorghum,sudangrass hybridsGRASSLAND SCIENCE, Issue 4 2008Brad Venuto Abstract As the bioenergy industry expands, producers choosing to shift current forage crop production to dedicated biomass crops can benefit from growing lower risk multipurpose crops that maximize management options. Hybrid forage sorghums (HFS) and sorghum,sudangrass hybrids (SSG) are capable of impressive biomass yields and tolerance to environmental stress. Multiple vegetative harvests (ratoon harvests) of sorghum are possible and there are photoperiod-sensitive sorghums that remain vegetative. However, the response of newer HFS and SSG cultivars to harvest management practices designed for forage or cellulosic feedstock production has not been fully investigated in all environments. The objectives of this study were to: (i) determine biomass production and quality characteristics of a genetically diverse range of HFS, SSG and sudangrass cultivars and evaluate their interaction with harvest system; and (ii) provide data to aid selection of sorghum cultivars for both forage and biofuel uses. Mean yield across all entries and years for a single late season harvest was 27.1 Mg ha,1 of dry matter per year. Mean total yield for a first harvest plus a ratoon crop was 25.5 Mg ha,1 of dry matter per year. However, entries varied for yield and interacted with harvest system. Mean caloric value was 16.5 Gj Mg,1 and modest differences were observed among cultivars evaluated. The best performing entry (cv. Tentaka) yielded 40.3 Mg ha,1 of dry matter for a single late season harvest, demonstrating the biomass potential of existing sorghum cultivars, specifically those possessing photoperiod- and/or thermosensitive genotypes. [source] Effects of Deficit Irrigation and Salinity Stress on Common Bean (Phaseolus Vulgaris L.) and Mungbean (Vigna Radiata (L.) Wilczek) Grown in a Controlled EnvironmentJOURNAL OF AGRONOMY AND CROP SCIENCE, Issue 4 2010M. Bourgault Abstract As water for irrigation purposes becomes increasingly scarce because of climate change and population growth, there is growing interest in regulated deficit irrigation (RDI) as a way to improve efficiency of water usage and farm productivity in arid and semi-arid areas. Salinity is also becoming an important problem in these same regions. Experiments were performed to investigate the effects of RDI and salt stress on two legumes crops, common bean (Phaseolus vulgaris L.) and mungbean (Vigna radiata (L.) Wilczek); previous work showed contrasting responses to RDI by these two crops under field conditions. The seed and biomass yields of both crops were reduced as a result of increasing water deficit stress; however, mungbean was able to maintain the same proportion of its biomass in reproductive structures and maintain its harvest index under stress, whereas common bean's decreased. In addition, photosynthesis in mungbean was higher than in common bean and higher at the same levels of transpiration. Finally, salinity stress did not affect the water potential, harvest index or the specific leaf weight of either crop. There were no interactions between salinity and crops or RDI levels, which suggest that the two crops do not differ in their response to salinity stress, and that RDI levels do not modify this response. [source] A review of methods for Centropomus spp. (snooks) aquaculture and recommendations for the establishment of their culture in Latin AmericaAQUACULTURE RESEARCH, Issue 7 2008Luis Alvarez-Lajonchčre Abstract The positive features of Centropomids and Latids for cultivation are analysed and highlighted. The main life cycle characteristics as well as market prices and demands are presented. Good growth, highly efficient food conversion ratios and energy utilization allow very high biomass yields per unit volume in nursery and grow-out systems. They have shown notable tolerances to main environmental conditions, as well as considerable versatility in adapting to culture systems (cages, ponds and tanks), and culture intensity (extensive, semi-intensive, intensive and superintensive), especially in estuarine and coastal sites and ponds. These positive features provide them with a high culture potential. A general summary of their culture is presented, based on the commercial cultivation of the Asian sea bass or barramundi Lates calcarifer as well as the experimental and pilot-scale results from the main American species. The importance of hatchery fry production as an essential culture pre-requisite is emphasized, in addition to an analysis of the main difficulties and constraints for future development. [source] Comparison of Growth and Recombinant Protein Expression in Two Different Insect Cell Lines in Attached and Suspension CultureBIOTECHNOLOGY PROGRESS, Issue 4 2001R. A. Taticek Culture conditions required for obtaining maximum recombinant protein concentrations from two cell lines, Spodoptera frugiperda (IPL,-Sf21-AE) and Trichoplusia ni (Tn 5,-1,4), were determined in this work. Conditions studied include mode of culture (suspended vs attached), agitation rates, inoculum sizes, cell concentration at the time of infection, and various serum-free media (SFM). Results were compared with the performance of attached cultures in TnM-FH with 10% fetal bovine serum. Growth rates in the different culture media tested were similar, but the cell numbers achieved (i.e., yield) improved 2 to 2.7-fold in SFM over cultures in TnM-FH. Agitation rates of 150,160 rpm were necessary for maximum growth of suspended Tn 5,-1,4 cells compared to 125,150 rpm for Sf-21 cells. An inoculum size of 5 × 105 cells/mL gave good growth rates and optimum biomass yields for both cell lines. Cultures of both cell lines were infected with viruses encoding for ,-galactosidase or human secreted alkaline phosphatase (seAP). Protein expression in TnM-FH in attached culture showed that Tn 5,-1,4 cells are 2,4.5 times more productive on a per cell basis than Sf-21 cells grown under similar conditions. Production of ,-galactosidase in Sf-21 cells increased 50% in suspension cultures with SFM compared to attached cultures in TnM-FH, but seAP expression was essentially unchanged by culture techniques. The Tn 5,-1,4 cells produced 2.6,4.4 and 2.7,3 times more ,-galactosidase and seAP, respectively, in SFM in suspension compared to Sf-21 cells. EX-CELL 401 and Sf900-II were formulated as optimized SFM for Sf cell lines. However, in Sf-21 cultures EX-CELL 400 performed better than the other two media, as it increased the ,-galactosidase yield up to 25%. Surprisingly, EX-CELL 401 was the best medium for the production of ,-galactosidase by Tn 5,-1,4 cells, resulting in 25% and 69% higher volumetric and specific yields, respectively, compared to EX-CELL 405 which was formulated for this specific cell line. These results show that even when culture media are designed for maximal growth of a specific cell line, other media may provide the best conditions for protein production. 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