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Initial Biomass (initial + biomass)
Selected AbstractsAcclimation Strategy of a Biohydrogen Producing Population in a Continuous-Flow Reactor with Carbohydrate FermentationENGINEERING IN LIFE SCIENCES (ELECTRONIC), Issue 4 2006Q. Ren Abstract Poor startup of biological hydrogen production systems can cause an ineffective hydrogen production rate and poor biomass growth at a high hydraulic retention time (HRT), or cause a prolonged period of acclimation. In this paper a new startup strategy was developed in order to improve the enrichment of the hydrogen-producing population and the efficiency of hydrogen production. A continuously-stirred tank reactor (CSTR) and molasses were used to evaluate the hydrogen productivity of the sewage sludge microflora at a temperature of 35,°C. The experimental results indicated that the feed to microorganism ratio (F/M ratio) was a key parameter for the enrichment of hydrogen producing sludge in a continuous-flow reactor. When the initial biomass was inoculated with 6.24,g of volatile suspended solids (VSS)/L, an HRT of 6,h, an initial organic loading rate (OLR) of 7.0,kg chemical oxygen demand (COD)/(m3,×,d) and an feed to microorganism ratio (F/M) ratio of about 2,3,g COD/(g of volatile suspended solids (VSS) per day) were maintained during startup. Under these conditions, a hydrogen producing population at an equilibrium state could be established within 30,days. The main liquid fermentation products were acetate and ethanol. Biogas was composed of H2 and CO2. The hydrogen content in the biogas amounted to 47.5,%. The average hydrogen yield was 2.01,mol/mol hexose consumed. It was also observed that a special hydrogen producing population was formed when this startup strategy was used. It is supposed that the population may have had some special metabolic pathways to produce hydrogen along with ethanol as the main fermentation products. [source] The effect of initial biomass in manipulative experiments on plantsFUNCTIONAL ECOLOGY, Issue 1 2006Z. KIKVIDZE No abstract is available for this article. [source] Carbohydrate storage enhances seedling shade and stress tolerance in a neotropical forestJOURNAL OF ECOLOGY, Issue 2 2007JONATHAN A. MYERS Summary 1To survive in forest understoreys, seedlings must depend on carbohydrate reserves when they experience negative carbon balance imposed by occasional light reduction and tissue loss to herbivores and diseases. We present the first experimental evidence in support of this hypothesis, using seven woody neotropical species. 2We transplanted seedlings that had recently expanded their first photosynthetic cotyledon or leaf to the forest understorey (1% of full sun) and quantified initial biomass and total non-structural carbohydrate (TNC) in stems, roots and storage cotyledons. We then randomly assigned seedlings to control and two stress treatments: light reduction (0.08% of full sun for 8 weeks) and complete defoliation. 3First-year survival of control seedlings, a comparative measure of shade tolerance, differed widely among species. The two stress treatments reduced survival and relative growth rates (RGR) of all species. Shade-tolerant species were little impacted by the stress treatments, whereas the two least shade-tolerant species experienced 100% mortality. 4In all treatments, 8-week and first-year survival was positively correlated with initial TNC pool size in stems and roots. By contrast, survival was generally not correlated with initial TNC concentration in any organ, TNC pools in cotyledons, seed mass or seedling biomass. 5TNC in stems and roots, but not in cotyledons, decreased in response to light reduction and defoliation over 8 weeks. Leaf area recovery of defoliated seedlings was positively correlated with initial TNC pools in stems and roots. 6First-year survival in each treatment was negatively correlated with 0,8 week RGR of control seedlings, suggesting higher stress tolerance of species with inherently slow growth rates in shade. RGR of control seedlings from 0 to 8 weeks was negatively correlated with initial TNC pools, but not concentrations, in stems and roots. After 8 weeks, RGR was positive for all species, without clear relationships with survival or TNC. 7We conclude that carbohydrate storage in stems and roots enhances long-term survival in shade by enabling seedlings to cope with periods of biotic and abiotic stress. Carbohydrate storage is a key functional trait that can explain species differences in growth and survival that lead to species coexistence through niche assembly processes and life-history trade-offs. [source] Pleomorphism of the marine bacterium Teredinobacter turniraeLETTERS IN APPLIED MICROBIOLOGY, Issue 1 2001G.M. Ferreira Aims:,A morphology transition for the marine bacterium, Teredinobacter turnirae is reported. Methods and Results:,When grown in the rod-shaped morphology, the cells require high concentrations of NaCl (0·3 mol l,1) and secrete extracellular protease and endoglucanase activity. When this bacterium is grown in a medium containing casein as a sole carbon and nitrogen source, a major change in morphology to a stable aggregated form is obtained. Conclusions:,In the aggregated morphology, much higher protease production rates (170 Units ml,1 d,1 for aggregates vs. 15 Units ml,1 d,1 for rods, for the same initial biomass) and negligible endoglucanase titres are obtained. In addition, the aggregated morphology does not require sodium chloride for growth. Significance and Impact of the Study:,The phenomenon reported here describes a novel relationship between the cell morphology and the biochemical characteristics of the bacterium. [source] A multikinetic model approach to predict gluconic acid production in an airlift bioreactorBIOTECHNOLOGY JOURNAL, Issue 5 2007Mukesh Mayani Abstract This paper uses a multikinetic approach to predict gluconic acid (GA) production performance in a 4.5 L airlift bioreactor (ALBR). The mathematical model consists of a set of simultaneous firstorder ordinary differential equations obtained from material balances of cell biomass, GA, glucose, and dissolved oxygen. Multikinetic models, namely, logistic and contois equations constitute kinetic part of the main model. The main model also takes into account the hydrodynamic and mass transfer parameters. These equations were solved using ODE solver of MATLAB v6.5 software. The mathematical model was validated with the experimental data available in the literature and is used to predict the effect of change in initial biomass and air sparging rate on the GA production. It is concluded that the mathematical model incorporated with multikinetic approach would be more efficient to predict the change in operating parameters on overall bioprocess of GA production in an ALBR. [source] | ||||||||||