Promotive effect of abscisic acid in flowering ofChenopodium rubrum as the result of decreasing apical dominance

Abscisic acid (ABA) was applied in a concentration of 1. 10^?3 M and 1. 10^?4 M to the quantitative SD plantChenopodium rubrum under various light regimes. ABA did not influence flowering in plants under continuous illumination, enhanced flowering in plants subjected to long days and inhibited it in plants induced by short days. It was concluded that ABA can not substitute for inductive treatment but its action may be additive to initial stages of reproductive morphogenesis (enhanced growth rate and branching of the apical meristem) as evoked by long days.     

Productivity of Chlorella sorokiniana in a short light‐path (SLP) panel photobioreactor under high irradiance

Maximal productivity of a 14 mm light‐path panel photobioreactor under high irradiance was determined. Under continuous illumination of 2,100 µmol photons m^?2 s^?1 with red light emitting diodes (LEDs) the effect of dilution rate on photobioreactor productivity was studied. The light intensity used in this work is similar to the maximal irradiance on a horizontal surface at latitudes lower than 37°. Chlorella sorokiniana, a fast‐growing green microalga, was used as a reference strain in this study. The dilution rate was varied from 0.06 to 0.26 h^?1. The maximal productivity was reached at a dilution rate of 0.24 h^?1, with a value of 7.7 g dw m^?2 h^?1 (m² of illuminated photobioreactor surface) and a volumetric productivity of 0.5 g dw L^?1 h^?1. At this dilution rate the biomass concentration inside the reactor was 2.1 g L^?1 and the photosynthetic efficiency was 1.0 g dw mol photons. This biomass yield on light energy is high but still lower than the theoretical maximal yield of 1.8 g mol photons^?1 which must be related to photosaturation and thermal dissipation of absorbed light energy. Biotechnol. Bioeng. 2009; 104: 352–359 © 2009 Wiley Periodicals, Inc.     

Nisin production in a chitin-including continuous fermentation system with Lactococcus lactis displaying a cell wall chitin-binding domain

The limiting factors in the continuous production of nisin are high amount of biomass loss and low dilution rate application. In this study, a chitin-including continuous nisin fermentation system (CICON-FER) was constructed for high volumetric nisin production using nisin producer L. lactis displaying cell wall chitin-binding domain (ChBD) together with chitin in the reactor. In this respect, the highest binding conditions of relevant L. lactis cells to chitin were determined. Then the chitin flakes carrying nisin-producing L. lactis cells were used within the CICON-FER system at different dilution rates (0.1–0.9 h^?1) and initial glucose concentrations (20–60 g l^?1). The results revealed that the pH 7 conditions and the use of 100 mM sodium phosphate buffer with 0.1 % Tween 20 and Triton X-100 significantly increased the binding capacity of ChBD displaying L. lactis cells to chitin. The constructed CICON-FER system maintained the presence of the ChBD surface displaying L. lactis cells in the reactor system until 0.9 h^?1 dilution rate that resulted in a considerably high level of volumetric nisin production and productivity (10,500 IU ml^?1 and 9,450 IU ml^?1 h^?1, respectively) with the combination of a 0.9-h^?1 dilution rate and a 40-g l^?1 initial glucose concentration. In conclusion, an innovative nisin fermentation system that yielded the highest nisin production thus far and that was feasible for industrial application was created.     

Photophosphorylation as a function of illumination time. I. Effects of permeant cations and permeant anions

(1) Very brief periods of illumination do not initiate photophosphorylation in isolated chloroplast lamellae. The time of illumination required before any phosphorylation can be detected is inversely proportional to the light intensity. At very high intensities, phosphorylation is initiated after illumination for about 4 ms.(2) There is no similar delay in the initiation of electron transport. The rate of electron transport is very high at first but declines at about the time the capacity for ATP synthesis develops. When the chloroplasts are uncoupled with gramicidin the high initial rate persists.(3) Various ions which permeate the thylakoid membrane (K⁺ or Rb⁺ in the presence of valinomycin, SCN^?, I^?, or ClO₄^?) markedly increase the time of illumination required to initiate phosphorylation. Potassium ions in the presence of valinomycin increase the delay to a maximum of about 50 ms whereas thiocyanate ions increase the delay to a maximum of about 25 ms. The effects of K⁺ with valinomycin and the effect of SCN^? are not additive. Permeant ions and combinations of permeant ions have little or no effect on phosphorylation during continuous illumination.(4) The reason for the threshold in the light requirement and the reason for the effect of permeant ions thereon are both obscure. However, it could be argued that the energy for phosphorylation initially resides in an electric potential gradient which is abolished by migration of ions in the field, leaving a more slowly developing proton concentration gradient as the main driving force for phosphorylation during continuous illumination. If so, the threshold in the presence of permeant ions should depend on internal hydrogen ion buffering.     

Investigation of lipid production by nitrogen-starved <Emphasis Type="Italic">Parachlorella kessleri</Emphasis> under continuous illumination and day/night cycles for biodiesel application

This study aims to investigate the triacylglycerol (TAG) productivity of Parachlorella kessleri grown under continuous illumination and to investigate its metabolism in simulated day/night cycles in order to estimate the feasibility of a large-scale production in outdoor solar photobioreactors. The strain was chosen for its ability to accumulate large amounts of triacylglycerol during nitrogen starvation. Several protocols of nitrogen starvation were tested in continuous illumination as well as in simulated day/night cycles. Sudden and progressive nitrogen starvation conditions have enhanced the TAG concentration and productivity of P. kessleri reaching up to 48 dry wt% and 4.4 × 10^?3 kg m^?2 day^?1, respectively. Microalgal cell metabolism was significantly affected by the day/night illumination cycles. The energy-rich compounds (TAGs and carbohydrates) were accumulated by P. kessleri during the photoperiods and partly consumed during the dark to sustain the microalgae vitality. This TAG oxidation ultimately led to a 26% decrease in TAG productivity in cultures exposed to day/night cycles compared to ones exposed to continuous illumination of equal 24-h average photon flux density. The results can dictate the optimal time for harvesting cells for recovering the largest amount of TAGs.     

Metabolic,physiological and kinetic aspects of the alcoholic fermentation of whey permeate by Kluyveromyces fragilis NRRL 665 and Kluyveromyces lactis NCYC 571

Optimum growth conditions for the fermentation of non-concentrated whey permeate by Kluyveromyces fragilis NRRL 665 have been defined. Use of 3.75 g yeast extract l^?1, a growth temperature of 38°C and a pH of 4.0 allowed a maximum productivity of 5.23 g ethanol l^?1 h^?1 in continuous culture with a yield 91% of theoretical. Complete batch fermentation of permeate with 100 g lactose l^?1 was possible with a maximum specific growth rate of 0.276 h^?1 without any change in ethanol yield. Fermentation of concentrated permeate resulted, however, in a general decrease of specific substrate consumption rate, demonstrated by the inability to completely convert an initial 90 or 150 g lactose l^?1 in continuous culture, even at dilution rates as low as 0.05 and 0.08 h^?1, respectively. The decrease could be related to substrate inhibition, to an increase in osmotic pressure caused by lactose and salts, and to ethanol inhibition of both alcohol and biomass yield. The decrease in specific productivity could be counterbalanced by use of high cell density cultures, obtained by cell recycle of K. fragilis. Fermentation of a non-concentrated permeáte at a dilution rate of 1 h^?1 resulted in a productivity of 22 g l^?1 h^?1 at 22 g ethanol l^?1. Cell recycle using flocculating Kluyveromyces lactis NCYC 571 was also tested. With this strain a productivity of 9.3 g l^?1 h^?1 at 45 g product l^?1 was attained at a dilution rate of 0.2 h^?1, with an initial lactose concentration of 95 g l^?1.     

Reduction of photosystem I reaction center, P-700, by plastocyanin in stroma thylakoids from spinach: Lateral diffusion of plastocyanin

The reduction kinetics of the photooxidized photosystem I reaction center (P-700⁺) by plastocyanin was studied in the stroma thylakoids prepared by the Yeda press treatment. The kinetics of the P-700⁺ reduction after flash excitation were biphasic and separated into two independent first-order reactions, the fast phase with a half-time of about 4 ms and the slow phase with a half-time of about 18 ms. Only the fast phase of the P-700⁺ reduction was sensitive to KCN and glutaraldehyde treatments of the thylakoids which block the plastocyanin site in the photosynthetic electron flow indicating that the fast phase is mediated by plastocyanin. However, the content of plastocyanin in the stroma thylakoids used was greatly decreased by the Yeda press treatment to only half that of P-700⁺ reduced in the fast phase. This indicates that one plastocyanin molecule turns over more than once in the single turnover of P-700⁺ rather than forming a fixed complex with P-700. On the other hand, the slow phase was not affected by KCN or glutaraldehyde treatment and its apparent rate constant linearly depended on the concentration of reduced dichlorophenolindophenol. These results indicate that the slow phase shows direct reduction of P-700⁺ by dichlorophenolindophenol. A second-order rate constant of 3.96 × 10⁵m^?1 s^?1 was obtained for the slow phase at pH 7.6, 25 °C. Analysis of reaction kinetics in the initial portion of the fast phase indicated initial interaction between P-700⁺ and the reduced plastocyanin and gave a half-time of 0.53 ms for the bimolecular reaction. We assumed the lateral diffusion of plastocyanin on the thylakoid membrane and calculated the two-dimensional diffusion coefficient for plastocyanin from the half-time of the initial reduction of P-700⁺ as about 2 × 10^?9 cm² s^?1.     

Light-flash analysis of the photoenzymic repair process in yeast cells III. The photoenzymic repair of respiratory-sufficient and respiratory-deficient cells cultured aerobically and anaerobically

In the previous papers, determinations of the number of deoxyribodipyrimidine photolyase or photoreactivating enzyme (PRE) molecules per cell and of the rate constant for the formation of the PRE-pyrimidine dimer complex, k₁, for yeast cells cultured aerobically, were described. In the present work, the number of PRE molecules and ther ate constant k₁ for respiratory-sufficient (RS) and respiratory-deficient (RD) cells of yeast cultured anaerobically were determined. The numbers of PRE molecules in both RS and RD cells cultured anaerobically were larger than those in cells cultured aerobicaly, whereas the rate constant k₁ (nuclear volume). (PRE molecules)^?1 sec^?1 showed a reverse relationship. The numbers of PRE molecules in cells cultured aerobically in various media were also determined.     

Growth potential of Lemna gibba: Effect of CO2 enrichment at high photon flux rate

Lemna gibba L. was cultivated in continuous light (800–1200 μmol quanta m^?2s^?1, 320–400 W m^?2) and normal or CO₂-enriched air (1500 μl CO₂ l^?1), with a continuous nutrient supply. Increased CO₂ concentration increased the unit leaf rate (ULR) or net assimilation rate and decreased the leaf area ratio (LAR) (photosynthetic area per unit dry weight), but the relative growth rate was unchanged (0.43 g g^?1 day^?1). The changes in ULR and LAR indicate that organic matter production can be increased with CO₂ enrichment at high photon flux rate (PFR).     

Phototropism in Hypocotyls of Radish : II. Role of cis- and trans-Raphanusanins, and Raphanusamide in Phototropism of Radish Hypocotyls

When etiolated radish (Raphanus sativus var. hortensis f. gigantissimus Makino) hypocotyls were subjected to a continuous unilateral illumination with white fluorescent light (0.1 watt per square meter), the growth rate at the lighted side was strongly inhibited for the first 2 hours, while that at the shaded side showed no change. After 2.5 hours growth on the lighted side recovered gradually, while that on the shaded side was slightly inhibited. The neutral growth inhibitors, cis- and trans-raphanusanins and raphanusamide, were determined in the lighted and shaded sides from 1 hour before until 2 hours after the start of unilateral illumination. In the lighted side, cis- and trans-raphanusanins increased by 0.5 hour after the start of illumination, reached 3 to 3.5-fold greater concentrations than in the shaded side after 1 hour, and then decreased gradually. Raphanusamide increased in the lighted side to a 3-fold greater concentration than that in the shaded one 2 hours after the start of the illumination. Unilateral applications of cis- and trans-raphanusanins and raphanusamide suppressed the growth of the hypocotyl on the applied side more than that on the opposite one, causing the hypocotyls to bend towards the site of application. The data suggest that phototropic curvature in radish is caused by the light-induced synthesis of growth-inhibiting cis- and trans-raphanusanins, and raphanusamide at the site of illumination.     

Degradation of cationic surfactants using Pseudomonas putida A ATCC 12633 immobilized in calcium alginate beads

In this study, the degradation of tetradecyltrimethylammonium bromide (TTAB) by freely suspended and alginate-entrapped cells from the bacteria Pseudomonas putida (P. putida) A ATCC 12633 was investigated in batch cultures. The optimal conditions to prepare beads for achieving a higher TTAB degradation rate were investigated by changing the concentration of sodium alginate, pH, temperature, agitation rate and initial concentration of TTAB. The results show that the optimal embedding conditions of calcium alginate beads are 4 % w/v of sodium alginate content and 2 × 10⁸ cfu ml^?1 of P. putida A ATCC 12633 cells that had been previously grown in rich medium. The optimal degradation process was carried out in pH 7.4 buffered medium at 30 °C on a rotary shaker at 100 rpm. After 48 h of incubation, the free cells degraded 26 mg l^?1 of TTAB from an initial concentration of 50 mg l^?1 TTAB. When the initial TTAB concentration was increased to 100 mg l^?1, the free cells lost their degrading activity and were no longer viable. In contrast, when the cells were immobilized on alginate, they degraded 75 % of the TTAB after 24 h of incubation from an initial concentration of 330 mg l^?1 of TTAB. The immobilized cells can be stored at 4 °C for 25 days without loss of viability and can be reused without losing degrading capacity for three cycles.     

Efficiency of copper removal by Sargassum sinicola in batch and continuous systems

The efficiency of batch and continuous systems of copper removal by Sargassum sinicola was studied. The effects of flow rate, initial metal concentration, and bed density on the capacity of the continuous system were also recorded. In batch systems, the maximum biosorption capacity was calculated as 49.63?±?0.88 mg g^?1; in the continuous system, under the following conditions: flow rate of 10 mL min^?1, initial solution of 200 mg Cu L^?1, bed density of 150 g L^?1, and higher copper removal of 62.39?±?1.91 mg g^?1 was achieved. The Thomas model can be used to predict the breakthrough curves, but it underestimated breakthrough time.     

GROWTH,PHOTOSYNTHESIS AND MAINTENANCE METABOLIC COST IN THE DIATOM PHAEODACTYLUM TRICORNUTUM AT VERY LOW LIGHT LEVELS 1

The compensation point for growth of Phaeodactylum tricornutum Bohlin is less than 1 μmol. m^?2s^?1. Growth at low PFDs (<3.5 μmol. m^?2.s^?1) does not appear to reduce the maximum quantum efficiency of photosynthesis (ø_m) or to greatly inhibit the potential for light-saturated, carbon-specific photosynthesis (P_m^c). The value for ø_m in P. tricornutum is 0.10–0.12 mol O₂-mol photon^?1, independent of acclimation PFD between 0.75 and 200 μmol.m^?2.s^?1 in nutrient-sufficient cultures. P_m^c in cells of P. tricornutum acclimated to PFDs <3.5 μmol m^?2?s^?1 is approximately 50% of the highest value obtained in nutrient-sufficient cultures acclimated to growth-rate-saturating PFDs. In addition, growth at low PFDs does not severely restrict the ability of cells to respond to an increase in light level. Cultures acclimated to growth at lees than 1% of the light-saturated growth rate respond rapidly to a shift-up in PFD after a short initial lag period and achieve exponential growth rates of 1.0 d^?1 (65% of the light- and nutrient-saturated maximum growth rate) at both 40 and 200 μmol.m^?2.s^?1     

Reduction of medium consumption in perfusion mammalian cell cultures using a perfusion rate equivalent concentrated nutrient feed

Media preparation for perfusion cell culture processes contributes significantly to operational costs and the footprint of continuous operations for therapeutic protein manufacturing. In this study, definitions are given for the use of a perfusion equivalent nutrient feed stream which, when used in combination with basal perfusion medium, supplements the culture with targeted compounds and increases the medium depth. Definitions to compare medium and feed depth are given in this article. Using a concentrated nutrient feed, a 1.8-fold medium consumption (MC) decrease and a 1.67-fold increase in volumetric productivity (PR) were achieved compared to the initial condition. Later, this strategy was used to push cell densities above 100 × 10⁶ cells/ml while using a perfusion rate below 2 RV/day. In this example, MC was also decreased 1.8-fold compared to the initial condition, but due to the higher cell density, PR was increased 3.1-fold and to an average PR value of 1.36 g L⁻¹ day⁻¹ during a short stable phase, and versus 0.46 g L⁻¹ day⁻¹ in the initial condition. Overall, the performance improvements were aligned with the given definitions. This multiple feeding strategy can be applied to gain some flexibility during process development and also in a manufacturing set-up to enable better control on nutrient addition.     

Factors affecting growth and product formation in plant cells grown in continuous culture

In the present work we examined the potential benefits of the continuous culture (chemostat) technique at improving biomass yields of Mentha and Dioscorea cells and product formation (diosgenin) by Dioscorea cells. In contrast to Mentha cells, Dioscorea cells were sensitive to mechanical agitation in the exponential growth phase and could only be grown in a bubble column type fermentor. Maximal biomass yield of 0.5 and 0.4 g cell dry weight g^?1sucrose were obtained for Mentha and Dioscorea cells, respectively. When the phosphate concentration during the growth phase of Dioscorea was increased, a maximal concentration of 7.8% diosgenin (of dry weight) was obtained. Productivity of diosgenin was 12 mg 1^?1 day^?1 in a two-stage continuous process as compared to 7.3 mg 1^?1 day^?1 in a batch culture.     

Successful operation of continuous reactors at short retention times results in high-density,fast-rate Dehalococcoides dechlorinating cultures

The discovery of Dehalococcoides mccartyi reducing perchloroethene and trichloroethene (TCE) to ethene was a key landmark for bioremediation applications at contaminated sites. D. mccartyi-containing cultures are typically grown in batch-fed reactors. On the other hand, continuous cultivation of these microorganisms has been described only at long hydraulic retention times (HRTs). We report the cultivation of a representative D. mccartyi-containing culture in continuous stirred-tank reactors (CSTRs) at a short, 3-d HRT, using TCE as the electron acceptor. We successfully operated 3-d HRT CSTRs for up to 120 days and observed sustained dechlorination of TCE at influent concentrations of 1 and 2 mM TCE to ≥97 % ethene, coupled to the production of 10¹² D. mccartyi cells L_culture ^?1. These outcomes were possible in part by using a medium with low bicarbonate concentrations (5 mM) to minimize the excessive proliferation of microorganisms that use bicarbonate as an electron acceptor and compete with D. mccartyi for H₂. The maximum conversion rates for the CSTR-produced culture were 0.13?±?0.016, 0.06?±?0.018, and 0.02?±?0.007 mmol Cl^? L_culture ^?1 h^?1, respectively, for TCE, cis-dichloroethene, and vinyl chloride. The CSTR operation described here provides the fastest laboratory cultivation rate of high-cell density Dehalococcoides cultures reported in the literature to date. This cultivation method provides a fundamental scientific platform for potential future operations of such a system at larger scales.     

Hertwig effect caused by UV-irradiation of sperm of Oryzias latipes (teleost) and its photoreactivation

When sperm of the fish Oryzias latipes were irradiated with ultrviolet light and allowed to fertilize normal egges, the so-called “Hertwig effect” was observed, with a dose-dependent decrease in survival rate at low doses (0–27 J · m^?2) but a better survival rate at higher dose ranges. Illumination with visible light after fertilization (10–70 min after insemination) showed the existence of photoreactivation (PR), demonstrating that pyrimidine dimers are a lesion in sperm DNA that is mainly responsible for the UV-caused Hertwig effect. Genetic analysis, in which sperm from a wild-type of this fish was used, showed that, after UV-irradiation at the high dose range, male nuclei did not participate in embryonic development (a gynogenetic haploid condition). Embryos having only a maternal set of chromosomes could develop no further than stage 27. Only the visible light during the early part (until around 20–30 min after insemination, at 25°C) of the single-cell stage was effective for PR; illumination thereafter was not.     

Immobilization of Kluyveromyces marxianus cells containing inulinase activity in open pore gelatin matrix: 2. Application for high fructose syrup production

Batch and continuous production of high fructose syrup from Jerusalem artichoke tubers has been studied using yeast cells immobilized in open pore gelatin matrix. In a batch reactor, the hydrolysis was 93% ($\text{d}\text{-fructose/}\text{d}\text{-glucose}\text{= 90/10}$) and 42 mg d-fructose per ml was produced from the artichoke tuber extract by immobilized cells in 3 h. The same immobilized cells were recycled and used repeatedly for 10 batch cycles starting with fresh juice at the beginning of each cycle. It was found that immobilized cells were extremely stable and the percent hydrolysis was almost constant for all 10 batch cycles. In a continuous reactor using an immobilized cell concentration of 65.7 g (dry wt) l^?1 of total working bioreactor volume, the percent hydrolysis was found to remain constant at ～100% at dilution rates <1.26 h^?1, but beyond that it decreased. Volumetric productivity attained its maximum value at D = 2.08 h^?1 and was found to be 100 g l^?1 h^?1. This was achieved at a feed sugar conversion of 80%. At 90% conversion and D = 1.66 h^?1, the productivity was found to be 90 g l^?1 h^?1. Continuous operation of the immobilized cell bioreactor at a constant dilution rate of 1.65 h^?1 for 240 h resulted in only 2% loss of original activity.     

Adoptive transfer of PR1 cytotoxic T lymphocytes associated with reduced leukemia burden in a mouse acute myeloid leukemia xenograft model

Background aimsTumor antigen-specific cytotoxic T lymphocytes (CTL) have been used in the treatment of human cancer, including leukemia. Several studies have established PR1 peptide, an HLA-A2.1-restricted peptide derived from proteinase 3 (P3), as a human leukemia-associated antigen. PR1-specific CTL elicited in vitro from healthy donors have been shown to lyse P3-expressing AML cells from patients. We investigated whether PR1-CTL can be adoptively transferred into NOD/SCID mice to eliminate human leukemia cells.MethodsPR1-CTL were generated in bulk culture from peripheral blood mononuclear cells (PBMC) stimulated with autologous dendritic cells. Human acute myeloid leukemia (AML) patient samples were injected and engrafted in murine bone marrow at 2 weeks post-transfer.ResultsFollowing adoptive transfer, bone marrow aspirate from mice that received AML alone had 72–88% blasts in a hypercellular marrow, whereas mice that received AML plus PR1-CTL co-infusion had normal hematopoietic elements and only 3–18% blasts in a hypocellular marrow. The PR1-CTL persisted in the bone marrow and liver and maintained a CD45RA^? CD28⁺ effector phenotype.ConclusionsWe found that adoptive transfer of PR1-CTL generated in vitro is associated with reduced AML cells in NOD/SCID mice. PR1-CTL can migrate to the sites of disease and maintain their capacity to kill the AML cells. The surface phenotype of PR1-CTL was consistent with their trafficking pattern in both vascular and end-organ tissues.