Kinetics of substrate removal in a completely mixed anaerobic filter

A completely mixed anaerobic filter, in which the influent organic matter concentration is diluted with recirculated effluent, was found to effectively remove organic matter concentrations in high strength acidic wastewater, at a range of organic loadings and shock loads. Increases in organic loading had a substantial effect on the relative organic matter composition of the effluent and the magnitude of the fatty acid fraction showed a pattern inverse to that of the nitrogenous organics. A fixed film model was formulated which indicated that at high substrate concentrations the substrate removal rate is proportional to the square root of the substrate concentration and the specific area of the filter medium. A comparison of the biofilm model and the measured effluent concentrations tended to indicate that the substrate removal rate is primarily affected by substrate concentration, specific surface area, flow rate, and temperature of the unit.     

Microwave-induced enzyme-catalyzed chemoselective reduction of organic azides

A lipase enzyme, suspended in organic media along with organic azides and irradiated under microwaves, enhances the reaction rate over thermal heating and affords the corresponding amines in high yields. The present biocatalytic method employing lipase is a significant development with remarkable regio- and chemoselectivity under microwave irradiation in organic media with excellent yields for the reduction of azide functionality.     

Physiological response of Spisula subtruncata (da Costa, 1778) to different seston quantity and quality

Individuals of the bivalve Spisula subtruncata were fed a mixed diet comprising of sea water enriched with the diatom Phaeodactylum tricornutum and ashed silt within a range of concentrations, simulating natural conditions above pseudofaeces threshold. The designed ranges for total particulate matter were between 10 and 30 mg l^–1and organic content of seston 15–40%. Filtration rate, rejection rate, ingestion rate and absorption rate were measured at those different conditions. Filtration rate and rejection rate were significantly correlated to total particulate matter and percentage of organic matter, with higher rates at higher values of total particulate matter and lower values of percentage organic matter. Ingestion rate was maintained at similar levels in all the treatments and organic enrichment of the ingested food occurred due to preingestive selection of the filtered material. A differential absorption rate occurred at different levels of organic matter in the diet with high rates at high values of the organic content of the diet. S. subtruncata showed different physiological responses to changes of the food conditions: (1) Increase of pseudofaeces production at increasing levels of particulate matter, (2) preingestive selection of organic material which enriched the organic fraction of ingested food, (3) stabilized ingestion rate and (4) increase of the absorption rate at high organic levels of the seston.     

Asymmetric synthesis with immobilized yeast in organic solvents: equilibrium conversion and effect of reactant partitioning on whole cell biocatalysis

A newly isolated strain of the yeast Saccharomyces cerevisiae is investigated for the biocatalytic reduction of ketones and the oxidation of alcohols in organic solvents. The yeast cells are immobilized by entrapment within calcium alginate beads and are found to possess the ability to stereoselectively reduce prochiral ketones and oxidize chiral alcohols to equilibrium conversions. The effect of reactant partitioning on the initial rate of the reactions is also investigated. The observed initial rates are found to vary inversely with reactant partitioning between the organic solvent and the biocatalyst beads. A kinetic model is developed to describe the initial reaction rate of hexanone reduction as a function of substrate concentration within the alginate beads.     

A simple technique for determining mineralization of carbon during incubation of soils treated with organic materials

Summary A simple technique is described for determining the rate of mineralization of carbon (carbon dioxide release) during incubation of soils treated with organic materials. The moistened mixture of soil and organic material is contained in a closed test tube and a small vial containing barium peroxide and water rests on the soil. This mixture absorbs carbon dioxide and releases oxygen in approximately equivalent amounts. The vial is removed periodically, replaced with a freshly charged vial, and its carbonate content determined in a calcimeter. Typical results obtained using a number of organic materials are presented.     

不同有机肥量对旱地玉米光合特性和产量的影响

在渭北旱塬合阳试验基地进行了4年的旱地有机培肥试验, 研究不同有机肥施用量对旱地玉米光合特性和产量的影响.结果表明： 与单施化肥相比,施有机肥处理的玉米各生育时期的叶片光合速率和气孔导度显著增大,胞间CO2浓度显著减小;随着有机肥施用量的增加,玉米叶片各生育时期的叶片光合速率和气孔导度逐渐增大,胞间CO2浓度逐渐减小.玉米各生育时期的光合作用主要受非气孔因素限制,施用有机肥显著降低了非气孔因素对光合的限制.连续4年施用有机肥,改善了土壤养分状况,使养分不再是玉米光合速率和产量的主要限制因子.     

河南封丘县域农田土壤固碳速率空间变异特征及其影响因素

农田土壤固碳速率是评价土壤固碳效应和潜力的重要指标,精确估算区域农田土壤固碳速率对土壤地力及环境效应均具有重要意义.本研究选取黄淮海平原典型潮土区河南省封丘县为研究区域,按照土壤利用-土壤类型联合单元布点法,于2011年采集了70个耕层土样,测定了土壤有机碳含量、机械组成、容重、pH,并与全国第二次土壤普查(1981年)数据进行对比分析,结合地统计方法和GIS技术研究了该地区近30年农田土壤固碳速率的空间变异特征,利用显著性检验、回归分析、方差分析等方法定量分析了该区域农田土壤固碳速率的影响因素.结果表明: 近30年封丘县域土壤固碳速率平均值为0.33 t C·hm^-2·a^-1,变异系数为74%,属于中等变异性;土壤固碳速率的变化在东西方向上表现为西高东低、中部高南北低,呈片状分布,区域结构性因素是引起农田土壤固碳速率空间分布差异的主导因素,如土壤类型、机械组成、容重、pH,可解释空间变异的59.5%,其次是随机性因素,如秸秆还田量、施肥量,可解释空间变异的40.5%.     

Discrepancies between cell volume and organic content in semi-continuous cultures of a marine microalga

J. FÁBREGAS, A. CID, E. MORALES, B. CORDERO AND A. OTERO. 1996. Changes in average cell volume, measured by flow cytometry, and cell organic content were studied in light/dark synchronized semi-continuous cultures of the marine microalga Phaeodactylum tricornutum . Cell volume and organic content both increased with nutrient concentration at all the renewal rates tested. Cell volume against renewal rate, at each nutrient concentration, followed a U-shaped curve with smallest cells at intermediate renewal rates. In contrast, cell organic content decreased continuously with increasing renewal rate. The variation in cell volume and organic content, related to culture conditions, should be taken into account if biochemical composition and productivity of microalgal cultures are assessed on the basis of cell counts.     

Feeding, growth, and fecundity of Abarenicola pacifica in relation to sediment organic concentration

For marine deposit-feeding invertebrates, the distribution of species with different life history strategies has long been known to be correlated with sediment organic concentration. Large populations of opportunistic species are found in sediments with enriched organic concentration, while equilibrium species populate low organic concentration sediments. Differences in both behavioral (e.g. feeding rate) and physiological (e.g. growth rate, reproductive output) adaptations determine the ability of species to establish populations in different environments. By systematically documenting differences in the way these factors vary as sediment organic concentration varies for both opportunistic and equilibrium species, we can better understand the mechanisms underlying this correlation between sediment organic concentration and species distributions. Here, we present the results of experiments examining the interactions among food concentration, feeding rate, growth rate, and reproductive output (measured as egg number and size) for the equilibrium species Abarenicola pacifica. A. pacifica is a large, long-lived, iteroparous, sub-surface deposit-feeding polychaete. Individual worms were reared throughout most of one generation in sediments differing only in the concentration of organic matter. Juveniles (<20 mg AFDW) had higher feeding rates and growth rates in sediments of higher organic concentration throughout the range tested. These results are consistent with the predictions from optimal foraging theory. As worms grew, however, these patterns changed. Once worms reached a mean body size of approximately 50 mg AFDW, feeding rate was greater on sediments of lower organic concentration (although it took worms in the sediments with lower organic concentration longer to reach this size). Differences in growth rates among treatments decreased as worms grew. For worms >100 mg AFDW, growth rates were uniformly low ( approximately 1%/day) on all sediments, but the early advantage obtained by worms in the high organic treatments resulted in much greater body sizes after 200 days. Worms had higher tissue triacylglyceride concentrations and produced more eggs (independent of worm size) as sediment organic concentration increased. We conclude that A. pacifica alters its feeding rate in response to variations in food resources in such a way as to maximize its energy intake and thereby maximize fitness. Future studies should investigate whether opportunistic species (as well as other equilibrium species) also have this ability.     

藻－菌生态系统代谢功能的生态学研究

在室内模拟条件下,研究了一些生态因子对藻－菌（Ａ＋Ｂ）生态系统代谢有机碳（Ｃ６Ｈ１２Ｏ６）、ＮＨ３－Ｎ和无机磷（ＩＰ）的影响．研究结果表明,当藻－菌生态系统中藻（Ａ）或菌（Ｂ）的起始数量一定时,其代谢Ｃ６Ｈ１２Ｏ６的速率,随与之组合的Ｂ或Ａ的起始数量增加（数量比则相应降低）而增加．在光照和黑暗条件下,Ａ＋Ｂ系统代谢上述３种营养物质的速率均有一定的差异．黑暗下Ｃ６Ｈ１２Ｏ６的平均代谢速率较光照下高１２．３％（Ｐ＜０．０５）,ＩＰ和ＮＨ３－Ｎ的平均代谢速率则分别较光照下低１４．４％（Ｐ＜０．０５）和１６．２％（Ｐ＜０．００１）．在Ａ＋Ｂ系统和Ａ、Ｂ单培养物中,３种营养物质的代谢速率均随有机负荷量增加而增加,而且Ａ＋Ｂ系统的代谢速率分别高于单培养的Ａ和Ｂ,其中ＮＨ３－Ｎ代谢尤为显著．文章还就生态系统结构与功能的关系问题进行了讨论．     

Seasonal Growth Rate of the Sponge Haliclona oculata (Demospongiae: Haplosclerida)

The interest in sponges has increased rapidly since the discovery of potential new pharmaceutical compounds produced by many sponges. A good method to produce these compounds by using aquaculture of sponges is not yet available, because there is insufficient knowledge about the nutritional needs of sponges. To gain more insight in the nutritional needs for growth, we studied the growth rate of Haliclona oculata in its natural environment and monitored environmental parameters in parallel. A stereo photogrammetry approach was used for measuring growth rates. Stereo pictures were taken and used to measure volumetric changes monthly during 1 year. Volumetric growth rate of Haliclona oculata showed a seasonal trend with the highest average specific growth rate measured in May: 0.012 +/- 0.004 day(-1). In our study a strong positive correlation (p < 0.01) was found for growth rate with temperature, algal biomass (measured as chlorophyll a), and carbon and nitrogen content in suspended particulate matter. A negative correlation (p < 0.05) was found for growth rate with salinity, ammonium, nitrate, nitrite, and phosphate. No correlation was found with dissolved organic carbon, suggesting that Haliclona oculata is more dependent on particulate organic carbon.     

Will changes in soil organic carbon act as a positive or negative feedback on global warming?

The world's soils contain about 1500 Gt of organic carbon to a depth of 1m and a further 900 Gt from 1--2m. A change of total soil organic carbon by just 10% would thus be equivalent to all the anthropogenic CO₂ emitted over 30 years. Warming is likely to increase both the rate of decomposition and net primary production (NPP), with a fraction of NPP forming new organic carbon. Evidence from various sources can be used to assess whether NPP or the rate of decomposition has the greater temperature sensitivity, and, hence, whether warming is likely to lead to an increase or decrease in soil organic carbon.Evidence is reviewed from laboratory-based incubations, field measurements of organic carbon storage, carbon isotope ratios and soil respiration with either naturally varying temperatures or after experimentally increasing soil temperatures. Estimates of terrestrial carbon stored at the Last Glacial Maximum are also reviewed. The review concludes that the temperature dependence of organic matter decomposition can be best described as: d(T) = exp[3.36 (T – 40)/(T + 31.79)] where d(T) is the normalised decomposition rate at temperature T (in °C). In this equation, decomposition rate is normalised to 1 at 40 °C.The review concludes by simulating the likely changes in soil organic carbon with warming. In summary, it appears likely that warming will have the effect of reducing soil organic carbon by stimulating decomposition rates more than NPP. However, increasing CO₂ is likely to simultaneously have the effect of increasing soil organic carbon through increases in NPP. Any changes are also likely to be very slow. The net effect of changes in soil organic carbon on atmospheric CO₂ loading over the next decades to centuries is, therefore, likely to be small.     

Enzyme reaction kinetics in organic solvents: A theoretical kinetic model and comparison with experimental observations

A theoretical kinetic model has been developed in order to describe the enzyme reaction in organic solvents. In this model the hydration of the enzyme molecule was examined and the equilibrium kinetic constants expressed in terms of thermodynamic activity. Analysis of a proposed kinetic model shows that the enzyme reaction rate in organic solvents is determined by two factors: substrate solvation and enzyme hydration, which are determined by the activity coefficient of the substrate and the water activity of the reaction media, respectively. The activity coefficient of the substrate and the water activity have been calculated using the UNIFAC equation to analyze the effects of organic solvents on the rate of enzyme reaction, and the results were compared with experimental data. Predictions of the proposed model were found to be in good agreement with previous experimental observations.     

Kinetics of whey-lactose acidogenesis

The mixed-culture anaerobic conversion of lactose to organic acids in a bench-scale continuous-flow stirredtank fermentor is considered. The major acidogenic end-product distribution with respect to the dilution rate are presented. A Monod chemostat model is employed to describe a microbial growth, and the influence on pH of the estimated model parameters is discussed.     

A Safe Organic Oxygen Battery Built with Li‐Based Liquid Anode and MOFs Separator

Safe rechargeable batteries of improved energy density and high power performance are urgently needed for the development of large electric devices. Herein, an Li‐based organic liquid anode is proposed, and an organic oxygen battery with a metal organic framework membrane separator is realized, which is able to conduct Li ions and separate other large species in the system. Equipped with the dual redox mediator strategy, the organic oxygen battery exhibits superior rate performance with long cycling life and low overpotential. A “solid electrolyte interface”‐like layer is observed between the organic liquid anode and the ion conducting separator. This work not only introduces a new type of anode for Li‐based batteries, but also provides fundamental insights for the better application of biphenyl‐based liquid anodes.     

Substrate utilization kinetic model for biological treatment process

The applicability of Contois' kinetic equation to aerobic and anaerobic treatments of organic wastes is investigated. A refractory coefficient to account for the nonbiodegradable portion of the organic substrates in the digester is incorporated into the kinetic equation. The kinetic equation is applied to the data for aerobic digestions of organic substrates and for anaerobic treatment of dairy wastes. They all show a very good fit of the kinetic equation to the data. Furthermore, the kinetic parameters and the refractory coefficients are shown to be independent of influent organic substrate concentration. This study confirms previous reports that the effluent quality of biological treatment systems for organic wastes depends on influent organic waste concentration. The effect of temperature on the kinetic parameters and the refractory coefficient for anaerobic treatment of sewage sludge are studied. It shows that the kinetic parameters vary with temperature, while the refractory coefficient remains fairly constant. Equations to predict biodegradable treatment efficiency and volumetric substrate utilization rate are also briefly discussed.     

The equilibrium and kinetics of N-acetyl-tryptophan phenylethyl ester synthesis by agarose-chymotrypsin in organic media

The synthesis of N-acetyl tryptophan phenylethyl ester in organic media is catalyzed by suspended agarose beads with multipoint covalently attached chymotrypsin. A dilute aqueous phase is trapped within the gel beads and may be manipulated separately from the organic phase. The equilibrium position becomes more favorable as the solvent polarity decreases, with K(eq) increasing 38 times between 2-butanone and 1,1,1-trichloroethane. The more apolar solvents also give faster kinetics. Addition of cosolvents (up to 10% dimethylformamide or 20% acetonitrile) does not affect the rate but does substantially reduce the equilibrium yield, presumably also by making the organic phase more polar. With trichloroethane as solvent the enzyme appears to be kinetically saturated with 1M phenylethanol. Doubling this concentration also does not cause the expected increase in equilibrium conversion, probably again because K(eq) is reduced in the more polar organic phase. Increased temperature raises the reaction rate as expected but has little effect on the equilibrium. (c) 1992 John Wiley & Sons, Inc.     

A kinetic model for microbic organic-matter decomposition in marine sediments

Abstract The microbial decomposition of organic matter in marine sediments has been described using a rate law which is linear in the concentration of the metabolizable organic matter, entirely independent of the biomass concentration, and displays a Monod-like dependence on the concentration of the oxidant species being utilized. This paper develops a quasi-reaction mechanism to explain these observed dependencies. The Monod dependence on the oxidant concentration and the biomass independence can both be traced back to the preponderance of occupied sites on the organic matter and pseudo-steady state concentrations of occupied sites during most of the decay process. In the framework of the proposed reaction scheme, the linearity of the rate with the organic matter concentration is possible only if there is a linear proportionality between surface area and mass of organic matter.
The rate law described above divides natural organic matter into a finite collection of reactive types. This paper also reformulates this rate law model in terms of a continuum of reactive types as proposed by Boudreau and Ruddick (Am. J. Sci. 291, 507–538, 1991). It is shown that this continuum model can produce a better fit to kinetic rate data than the discrete model.     

Influence of fertilization on the Colorado potato beetle, Leptinotarsa decemlineata, in organic potato production

The abundance of the Colorado potato beetle, Leptinotarsa decemlineata (Say), in organically grown potato did not change significantly in response to increasing rates of dehydrated poultry manure. However, peaks of abundance of larvae were shifted forward in time in response to the high rate of organic fertilizer. Tests using excised foliage showed that the shift was not caused by differential larval mortality or longer developmental times. Time allocation to resting, walking, and feeding by adults was similar regardless of fertilizer rate. Adult foliage consumption was unaffected by organic fertilizer rates in no choice tests and significantly affected in few choice tests. A 22% longer larval development time on plants treated with low fertilizer rate than on plants with high rate was the most significant effect. Even though maximum plant height, canopy, biomass, and yield were significantly smaller in the organic than in conventional plots, the suitability of the plants was not affected except for reduced feeding by summer beetles. Summer adults spent less time feeding and consumed two to five times less foliage on organic potato than on inorganically fertilized and conventionally produced plants. The overall influence of fertilizer on Colorado potato beetle populations was limited and therefore can only play a secondary role in management strategies for organic potato. Avoidance of excessive organic fertilizer that promotes short larval development time and extension of the period over which large Colorado potato beetle larvae are present should be recommended.     

Correlation of abundance of arbuscular mycorrhizal fungi, bacteria and saprophytic microfungi with soil carbon, nitrogen and phsophorus

A significant positive correlation between the concentration of CFU of soil saprophytic microfungi and total soil carbon content, organic matter (oxidizable carbon) and available phosphorus was observed in field collected soil samples. Concentration of CFU of culturable bacteria correlated negatively with soil organic matter. Specific length of hyphae of arbuscular mycorrhizal fungi in the soil correlated only with soil respiration rate. The results indicate that arbuscular mycorrhizal fungi are associated with soil microsites rich in some easily mineralizable fraction of soil, organic matter rather than with total or oxidizable organic carbon.