Localized hybridization betweenSaxifraga aizoides andS. mutata (Saxifragaceae): Reproductive ecology ofS. ×hausmannii and implications for conservation

The roles of hybridization and of introgression as potential threats to small native populations are current topics of interest both for evolutionary and conservation biologists. Two factors are mainly involved in the threat to natural populations through hybridization: demographic swamping and genetic assimilation. At prealpine locations, twoSaxifraga species with very different growth habits,S. aizoides andS. mutata, form a hybrid,S. ×hausmannii. Investigation of meiosis and crossing experiments revealed regular pairing of the 26 chromosomes and development of viable seeds in the hybrid. Analysis of hybrid indices, GPI allozymes, germination experiments and seed sizes showed an intermediate position ofS. ×hausmannii between its parental species.Saxifraga aizoides andS. mutata were separated by only weak hybridization barriers. Introgression occurred mostly in direction ofS. aizoides, although to a small amount. There is no actual threat to small, prealpine populations ofS. aizoides andS. mutata through interspecific gene flow because hybridization is localized, resulting from different flowering phenologies of the parental species and from the narrow habitat requirements ofS. ×hausmannii, which are similar to those ofS. aizoides. The major threat to local, prealpine populations ofS. aizoides andS. mutata is the loss of landscape dynamics. Both species need open erosion slopes for successful recruitment.     

Stream channel experiments on downstream movement of recently emerged trout, Salmo trutta L. and salmon, S. salar L.—I. Effect of four different water velocity treatments upon dispersal rate

Four experimental stream channels were used to study instantaneous downstream dispersal rates of young trout, Salmo trutta L., and salmon, S. salur L ., relative to four different water velocities.
Young salmon showed a high rate of dispersal at a low velocity of 7.5 cm s⁻¹ and lower rates at higher velocities of 25 to 70cm s⁻¹. Trout showed their lowest rate at 25cm s⁻¹ with a slightly higher rate at 7.5 cm s⁻¹ and increasingly higher rates at velocities in excess of 25 cm s⁻¹. These results are consistent with field observations on the velocity preferences of young trout and salmon.     

A monolithic lipase reactor for biodiesel production by transesterification of triacylglycerides into fatty acid methyl esters

An enzymatic reactor with lipase immobilized on a monolithic polymer support has been prepared and used to catalyze the transesterification of triacylglycerides into the fatty acid methyl esters commonly used for biodiesel. A design of experiments procedure was used to optimize the monolithic reactor with variables including control of the surface polarity of the monolith via variations in the length of the hydrocarbon chain in alkyl methacrylate monomer, time of grafting of 1-vinyl-4,4-dimethylazlactone used to activate the monolith, and time used for the immobilization of porcine lipase. Optimal conditions involved the use of a poly(stearyl methacrylate-co-ethylene dimethacrylate) monolith, grafted first with vinylazlactone, then treated with lipase for 2 h to carry out the immobilization of the enzyme. Best conditions for the transesterification of glyceryl tributyrate included a temperature of 37°C and a 10 min residence time of the substrate in the bioreactor. The reactor did not lose its activity even after pumping through it a solution of substrate equaling 1,000 reactor volumes. This enzymatic reactor was also used for the transesterification of triacylglycerides from soybean oil to fatty acid methyl esters thus demonstrating the ability of the reactor to produce biodiesel.     

塔拉多糖的脱色工艺化研究

塔拉多糖是一种半乳甘露聚糖胶,对于我们具有非常重要的应用价值。本实验主要对塔拉提取物中的塔拉多糖进行脱色工艺化研究;在单因素实验的基础上,对活性炭颗粒质量、脱色时间、脱色温度以及脱色次数这四种因素进行正交优化实验,其最佳脱色实验参数为：活性炭颗粒0.6 g,脱色45 min,脱色温度45℃脱色次数3次,脱色率可以达到50.21%,同时多糖类保留率为90.39%。     

Viral clearance by flow‐through mode ion exchange columns and membrane adsorbers

Anion exchange (AEX) is a common downstream purification operation for biotechnology products manufactured in cell culture such as therapeutic monoclonal antibodies (mAbs) and Fc‐fusion proteins. We present a head‐to‐head comparison of the viral clearance efficiency of AEX adsorbers and column chromatography using the same process fluids and comparable run conditions. We also present overall trends from the CDER viral clearance database. In our comparison of multiple brands of resins and adsorbers, clearance of three model viruses (PPV, X‐MuLV, and PR772) was largely comparable, with some exceptions which may reflect run conditions that had not been optimized on a resin/membrane specific basis. © 2013 American Institute of Chemical Engineers Biotechnol. Prog., 30:124–131, 2014     

Faunal response to benthic and hyporheic sedimentation varies with direction of vertical hydrological exchange

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Metabolic isotopomer labeling systems. Part II: structural flux identifiability analysis

Metabolic flux analysis using carbon labeling experiments (CLEs) is an important tool in metabolic engineering where the intracellular fluxes have to be computed from the measured extracellular fluxes and the partially measured distribution of 13C labeling within the intracellular metabolite pools. The relation between unknown fluxes and measurements is described by an isotopomer labeling system (ILS) (see Part I [Math. Biosci. 169 (2001) 173]). Part II deals with the structural flux identifiability of measured ILSs in the steady state. The central question is whether the measured data contains sufficient information to determine the unknown intracellular fluxes. This question has to be decided a priori, i.e. before the CLE is carried out. In structural identifiability analysis the measurements are assumed to be noise-free. A general theory of structural flux identifiability for measured ILSs is presented and several algorithms are developed to solve the identifiability problem. In the particular case of maximal measurement information, a symbolical algorithm is presented that decides the identifiability question by means of linear methods. Several upper bounds of the number of identifiable fluxes are derived, and the influence of the chosen inputs is evaluated. By introducing integer arithmetic this algorithm can even be applied to large networks. For the general case of arbitrary measurement information, identifiability is decided by a local criterion. A new algorithm based on integer arithmetic enables an a priori local identifiability analysis to be performed for networks of arbitrary size. All algorithms have been implemented and flux identifiability is investigated for the network of the central metabolic pathways of a microorganism. Moreover, several small examples are worked out to illustrate the influence of input metabolite labeling and the paradox of information loss due to network simplification.     

Effects of sedimentation from water-based drill cuttings and natural sediment on benthic macrofaunal community structure and ecosystem processes

In this study, we aim at investigating the role of physical disturbance in effects of water-based drill cuttings on benthic ecosystems. Today, most of the cuttings discharged from oil and gas installations contain water-based drilling muds, rather than oil-based or synthetic muds. Drill cuttings with water-based muds are assumed to cause only marginal effects on the benthos, mainly resulting from sedimentation. However, this statement has not been experimentally tested, which is the purpose of the present work. Natural sediment particles and water-based drill cuttings were added to benthic communities in layer thicknesses of 3-24 mm in a mesocosm set-up. During the following 6 months, changes in benthic community structure and fluxes of oxygen and nutrients across the sediment water interface were studied. There was a significant reduction in number of taxa, abundance, biomass and diversity of macrofauna with increasing thickness of drill cuttings, which was not observed for the natural sediment particles. The drill cuttings also influenced oxygen consumption and oxygen penetration depth in the sediment, and it was concluded that an organic compound in the drill cuttings initiated a typical eutrophication response. Fluxes of phosphate and silicate were, however, similarly affected by the two types of particles, and maximum fluxes occurred in sediments treated with thin layers (3-6 mm) of particles. As the response of water-based drill cuttings in the present study was a result of factors other than physical disturbance, we recommend a reconsideration of the assumption that water-based drill cuttings only cause sedimentation (burial) effects.     

Toward intensifying design of experiments in upstream bioprocess development: An industrial Escherichia coli feasibility study

In this study, step variations in temperature, pH, and carbon substrate feeding rate were performed within five high cell density Escherichia coli fermentations to assess whether intraexperiment step changes, can principally be used to exploit the process operation space in a design of experiment manner. A dynamic process modeling approach was adopted to determine parameter interactions. A bioreactor model was integrated with an artificial neural network that describes biomass and product formation rates as function of varied fed‐batch fermentation conditions for heterologous protein production. A model reliability measure was introduced to assess in which process region the model can be expected to predict process states accurately. It was found that the model could accurately predict process states of multiple fermentations performed at fixed conditions within the determined validity domain. The results suggest that intraexperimental variations of process conditions could be used to reduce the number of experiments by a factor, which in limit would be equivalent to the number of intraexperimental variations per experiment. © 2016 American Institute of Chemical Engineers Biotechnol. Prog., 32:1343–1352, 2016     

CLINES FOR HYBRID DYSFUNCTION IN A GRASSHOPPER HYBRID ZONE

Two subspecies of the grasshopper Chorthippus parallelus meet in the Pyrenees forming a hybrid zone several kilometers wide. Crosses between the two pure taxa result in sterile male offspring and normal females (i.e., Haldane's rule applies). However, no such dysfunction has been detected in hybrid males collected through the center of the hybrid zone. By assessing the level of dysfunction in the offspring of reciprocal crosses, it was possible to map clines for the genes responsible for dysfunction through the zone. This analysis shows that there is no abrupt transition between incompatible genomes in the field. Crosses were also made between females collected from a transect spanning the hybrid zone and pure males of both subspecies. This reveals noncoincident clines for dysfunction near the center of the hybrid zone such that the dysfunction expressed in the offspring of these crosses is less than expected from simple models. More complex models involving interaction among genes must be invoked. Also, the possibility exists that since the postglacial contact of these two grasshopper taxa, hybrid dysfunction has become ameliorated by the evolution of modifiers. This hybrid zone is thought to be a tension zone, maintained by a balance between selection against hybrid genotypes and dispersal into the zone center. The lessening of hybrid disadvantage over time through the breakdown of epistatic interactions by recombination or through modification could account for the general lack of dysfunction in field collected hybrids today.