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Growth Yield (growth + yield)
Selected AbstractsENHANCEMENT OF INTRACELLULAR SAXITOXIN ACCUMULATION BY LIDOCAINE HYDROCHLORIDE IN THE CYANOBACTERIUM CYLINDROSPERMOPSIS RACIBORSKII T3 (NOSTOCALES),JOURNAL OF PHYCOLOGY, Issue 3 2003Francesco Pomati The metabolic effect of three different concentrations of lidocaine hydrochloride (0.01, 0.1, and 1 ,M) on growth and saxitoxin (STX) production of the freshwater cyanobacterium Cylindrospermopsis raciborskii (Wolosznska) T3 was analyzed. Lidocaine hydrochloride increased both the growth rate and the final growth yield in the toxic cyanobacterium, with a maximum of 25% and 18% for a 1-,M dose, respectively. Moreover, C. raciborskii T3 samples harvested at the end of the growth phase and analyzed for STX content by HPLC showed an increase in STX intracellular concentration of 14.3% and 49.3% after exposure to 0.01 and 0.1 ,M lidocaine hydrochloride, respectively, whereas 1 ,M lidocaine hydrochloride resulted in a 114% incremental change in STX content. The time course of the 1-,M lidocaine hydrochloride effect showed the highest rate of increase in mean STX intracellular concentration (298%) within the first 2 h after induction. The increase in STX content induced by lidocaine hydrochloride in C. raciborskii T3 was dependent on the concentration of Na+ ions in the culture medium and alkaline pH. The results suggest a possible action of lidocaine hydrochloride on membrane ion fluxes and the hypothesis of a potential linkage between cyanobacterial homeostasis and STX regulation. [source] A new ferrous iron-uptake transporter, EfeU (YcdN), from Escherichia coliMOLECULAR MICROBIOLOGY, Issue 1 2006Cornelia Große Summary Escherichia coli possesses multiple routes for iron uptake. Here we present EfeU (YcdN), a novel iron acquisition system of E. coli strain Nissle 1917. Laboratory strains of E. coli such as K12 lack a functional (efeU) ycdN gene caused by a frameshift mutation. EfeU, a member of the oxidase-dependent iron transporters (OFeT), is a homologue of the iron permease Ftr1p from yeast. The ycdN gene is part of the ycdNOB tricistronic operon which is expressed in response to iron deprivation in a Fur-dependent manner. Expression of efeU resulted in improved growth of an E. coli mutant lacking all known iron-uptake systems and mediated increased iron uptake into cells. Furthermore, the presence of other divalent metal cations did not impair growth of strains expressing efeU. The EfeU protein functioned as ferrous iron permease in proteoliposomes in vitro. Topology analysis indicated that EfeU is an integral cytoplasmic membrane protein exhibiting seven transmembrane helices. Two REXXE motifs within transmembrane helices of OFeT family members are implicated in iron translocation. Site-directed mutagenesis of each REGLE motif of EfeU diminished iron uptake in vivo and growth yield. In vitro the EfeU variant protein with an altered first REGLE motif was impaired in iron permeation, whereas activity of the EfeU variant with a mutation in the second motif was similar to the wild-type protein. [source] Characterization of single-walled carbon nanotubes synthesized using iron and cobalt nanoparticles derived from self-assembled diblock copolymer micellesAPPLIED ORGANOMETALLIC CHEMISTRY, Issue 8 2010Qiang Fu Abstract We present a comparative study of single-walled carbon nanotubes grown using iron and cobalt nanoparticles as catalysts via the chemical vapor deposition approach. Monodispersed iron and cobalt oxide nanoparticles with an average size of 2 nm were prepared using a polystyrene- b -poly (4-vinylpyridine) diblock copolymermicelle template. The 2 nm iron oxide nanoparticles generated single-walled carbon nanotubes with an average diameter of 1.5 nm while 2 nm cobalt oxide nanoparticles produced single-walled carbon nanotubes with an average diameter of 1.0 nm. To achieve high growth yield using iron nanoparticles as catalyst, higher carbon feed rate is required. These findings demonstrate the importance of the synergic interaction between catalyst and carbon precursor in single-walled carbon nanotube formation. It also elucidates the important role of catalyst chemical composition on carbon nanotube properties. Copyright © 2010 John Wiley & Sons, Ltd. [source] Continuous Cultivation of the Diatom Nitzschia laevis for Eicosapentaenoic Acid Production: Physiological Study and Process OptimizationBIOTECHNOLOGY PROGRESS, Issue 1 2002Zhi-You Wen The continuous cultures of the diatom Nitzschia laevis were performed at different dilution rates ( D) and feed glucose concentrations ( S0) to investigate cellular physiological responses and its production potential of eicosapentaenoic acid (EPA). Steady-state cell dry weight, residual glucose concentration, cell growth yield, specific glucose consumption rate, and fatty acid profiles were investigated within the range of D from 0.1 to 1.0 day,1 ( S0 fixed at 20 g/L) and the range of S0 from 5 to 35 g/L ( D fixed at 0.3 day,1), respectively. The highest EPA productivity of 73 mg L -1 day -1 was obtained at D = 0.5 day,1 and S0 = 20 g/L. However, when the continuous culture achieved high productivities of EPA at certain dilution rates and feed glucose concentrations, glucose in the feed could not be consumed completely. Accordingly, the continuous culture was evaluated in terms of both EPA productivity ( P) and glucose assimilation efficiency ( E). The parameter ,, defined as the product of P and E, was used as an overall performance index. Since , is a function of the two independent variables Dand S0, we employed a central composite design to optimize D and S0 for the highest , value. Based on the experimental results of the design, a second-order polynomial equation was established to represent the relationship between , and D and S0. The optimal values of D and S0 were subsequently determined as 0.481 day,1 and 15.56 g/L, respectively by the empirical model. The verification experiment confirmed the validity of the model. Under the optimal conditions, , value reached 46.5 mg L -1 day -1, suggesting a considerably high efficiency of the continuous culture of N. laevis in terms of EPA production and glucose utilization. [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] Dissimilatory ferrous iron oxidation at a low pH: a novel trait identified in the bacterial subclass RubrobacteridaeFEMS MICROBIOLOGY LETTERS, Issue 2 2008Christopher G. Bryan Abstract A novel iron-oxidizing acidophilic actinobacterium was isolated from spoil material at an abandoned copper mine. Phylogenetic analysis placed the isolate within the Rubrobacteridae subclass of the Actinobacteria. Its optimum temperature and pH for growth are 30,35 °C and pH 3.0, respectively. Although it could catalyze the dissimilatory oxidation of ferrous iron, growth yields declined progressively in media containing ferrous iron concentrations >100 ,M. The isolate, Pa33, did not grow or oxidize iron in the absence of organic carbon, and appeared to be an obligate heterotroph. Specific rates of iron oxidation were much smaller than those determined for the autotrophic iron-oxidizing proteobacterium Acidithiobacillus ferrooxidans and the heterotrophic iron-oxidizing actinobacterium Ferrimicrobium acidiphilum. Iron oxidation by isolate Pa33 appears to be a defensive mechanism, in which iron oxidation converts a soluble species to which the bacterium is sensitive to an oxidized species (ferric iron) that is highly insoluble in the spoil from which it was isolated. This is the first report of acidophily or dissimilatory iron oxidation within the Rubrobacteridae subclass and one of very few within the Actinobacteria phylum as a whole. [source] Mutants of the pentose-fermenting yeast Pichia stipitis with improved tolerance to inhibitors in hardwood spent sulfite liquorBIOTECHNOLOGY & BIOENGINEERING, Issue 5 2009Paramjit K. Bajwa Abstract Mutants of Pichia stipitis NRRL Y-7124 able to tolerate and produce ethanol from hardwood spent sulfite liquor (HW SSL) were obtained by UV mutagenesis. P. stipitis cells were subjected to three successive rounds of UV mutagenesis, each followed by screening first on HW SSL gradient plates and then in diluted liquid HW SSL. Six third generation mutants with greater tolerance to HW SSL as compared to the wild type (WT) were isolated. The WT strain could not grow in HW SSL unless it was diluted to 65% (v/v). In contrast, the third generation mutants were able to grow in HW SSL diluted to 75% (v/v). Mutants PS301 and PS302 survived even in 80% (v/v) HW SSL, although there was no increase in cell number. All the third generation mutants exhibited higher growth rates but significantly lower growth yields on xylose or glucose compared to the WT. The mutants fermented 4% (w/v) glucose as efficiently as the WT and fermented 4% (w/v) xylose more efficiently with a higher ethanol yield than the WT. In a medium containing 4% (w/v) each of xylose and glucose, all the third generation mutants utilized glucose as efficiently and xylose more efficiently than the WT. This resulted in higher ethanol yield by the mutants. The mutants retained the ability to utilize galactose and mannose and ferment them to ethanol. Arabinose was consumed slowly by both the mutants and WT with no ethanol production. In 60% (v/v) HW SSL, the mutants utilized and fermented glucose, mannose, galactose and xylose while the WT could not ferment any of these sugars. Biotechnol. Bioeng. 2009; 104: 892,900. © 2009 Wiley Periodicals, Inc. [source] | ||||||||||