Investigation of nanofiltration as a purification step for lactic acid production processes based on conventional and bipolar electrodialysis operations

Nanofiltration was investigated for usability in a specific lactic acid production process based on conventional and bipolar electrodialysis operations. Industrial fluids, corresponding to two potential integration levels and coming from an existing installation, were investigated. The commercially available DK nanofiltration membrane was used and performances in terms of lactate/lactic acid recovery rate and purification efficiency are reported. Nanofiltration was able to efficiently remove magnesium and calcium ions from a sodium lactate fermentation broth before its concentration and conversion by electrodialysis (first potential integration level). Maximum impurities rejections and lactate recovery were obtained at maximum transmembrane pressures. Mg2+ and Ca2+ rejections were 64±7 and 72±7%, respectively and lactate recovery rate reached 25±2 molm−2 h−1 for P = 20 bar. Sulfate and phosphate ions were also partially removed from the broth (40% rejection). At the invert, chloride ions were negatively retained by the membrane and were consequently more concentrated in the permeate. Nanofiltration also led to a nearly total decolouration of the fermentation broth. On the other hand, sulfate and phosphate rejections obtained from the filtration of a converted broth containing the lactic acid under its neutral form (second potential integration level) were also satisfactory, i.e. 47±5 and 51±5%, respectively. High recovery rates were observed in that case, i.e. 48±2 molm−2 h−1 at 20 bar. It indicated that NF could also be used as final purification step in the process

Introduction of nanofiltration in a production process of fermented organic acids

Nanofiltration in a production process of fermented organic acid

Acid-base thermochemistry of gaseous oxygen and sulfur substituted amino acids (Ser, Thr, Cys, Met)

International audienceAcid-base thermochemistry of isolated amino acids containing oxygen or sulfur in their side chain (serine, threonine, cysteine and methionine) have been examined by quantum chemical computations. Density functional theory (DFT) was used, with B3LYP, B97-D and M06-2X functionals using the 6-31+G(d,p) basis set for geometry optimizations and the larger 6-311++G(3df,2p) basis set for energy computations. Composite methods CBS-QB3, G3B3, G4MP2 and G4 were applied to large sets of neutral, protonated and deprotonated conformers. Conformational analysis of these species, based on chemical approach and AMOEBA force field calculations, has been used to identify the lowest energy conformers and to estimate the population of conformers expected to be present at thermal equilibrium at 298 K. It is observed that G4, G4MP2, G3B3, CBS-QB3 composite methods and M06-2X DFT lead to similar conformer energies. Thermochemical parameters have been computed using either the most stable conformers or equilibrium populations of conformers. Comparison of experimental and theoretical proton affinities and Delta(acid)H shows that the G4 method provides the better agreement with deviations of less than 1.5 kJ mol-1. From this point of view, a set of evaluated thermochemical quantities for serine, threonine, cysteine and methionine may be proposed: PA = 912, 919, 903, 938; GB = 878, 886, 870, 899; Delta(acid)H = 1393, 1391, 1396, 1411; Delta(acid)G = 1363, 1362, 1367, 1382 kJ mol-1. This study also confirms that a non-negligible Delta(p)S° is associated with protonation of methionine and that the most acidic hydrogen of cysteine in the gas phase is that of the SH group. In several instances new conformers were identified thus suggesting a reexamination of several IRMPD spectra

Modélisation du RMI et trajectoires des allocataires : Une analyse empirique des liens RMI-marché du travail à partir de données individuelles

Document de travailDans une perspective analytique, on cherche à établir une représentation appropriée du RMI afin de rendre compte simultanément de l'ensemble de ses dimensions et des dynamiques qui l'animent. A travers cette approche, la question des liens avec le marché du travail, au centre de l'analyse, peut être abordée en incluant les dimensions institutionnelles propres au RMI qui modèlent son fonctionnement réel. La prise en compte des règles complexes qui le fondent du fait de la pluralité des objectifs et de l'hétérogénéité des populations conduit à dépasser l'interprétation de ses effets en termes d'incitation/désincitation des individus à la reprise d'activité. Plus largement, cette approche permet de mieux situer la place du RMI dans le système de protection sociale dont il marque une certaine forme d'universalisation et dans la régulation du marché du travail à travers les liens particuliers qu'il entretient avec certains de ses segments.Les données utilisées sont extraites de l'enquête de la DREES réalisée en juin 2006 auprès d'un échantillon de 3000 allocataires du RMI

L'évaluation du RMI : la simplification de la démarche et ses enjeux

URL des Cahiers : https://halshs.archives-ouvertes.fr/CAHIERS-MSECahiers de la MSE 2005.38 - Série Rouge - ISSN : 1624-0340This paper analyses the different evaluation programs which have been conducted since the beginning of the minimum income policy in 1989. It's aimed at interpreting the links between the evaluation models and the policies. Two approaches can be highlighted; the first one, that we can all "pluralistic approach" started with the early works of the national evaluation committee until the mid-90's and combined many purposes and procedures. Despite the extensive knowledge gained about the problems of poverty, it led to very few public decisions. The second approach initiated in the mid-90's resulted from the rising cost of the policy of minimum income due to the increasing number of beneficiaries. By focusing on simple indicators of efficiency and using econometric methods, the analysis appears more restrictive but it led to policy decisions which deeply modified the minimum income policy.L'analyse des travaux d'évaluation du RMI permet de distinguer deux approches principales. La première, pluraliste dans ses objectifs et ses méthodes, s'étend des travaux de la commission nationale d'évaluation jusqu'au milieu des années 90. En dépit de ses apports réels concernant la connaissance des phénomènes de pauvreté, cette approche a eu peu d'incidences pratiques. La seconde conception qui se développe à partir du milieu des années 90 est liée aux préoccupations financières engendrées par l'augmentation importante du nombre de bénéficiaires. En privilégiant des indicateurs simples d'efficacité et des méthodes issues de l'économétrie, elle apparaît plus restrictive dans ses investigations. Cependant, ses préconisations opérationnelles en termes d'action publique ont contribué à modifier le dispositif initial, en esquivant la question centrale de la pluralité de ses fonctions

A quantitative model for cyclin-dependent kinase control of the cell cycle: revisited

The eukaryotic cell division cycle encompasses an ordered series of events. Chromosomal DNA is replicated during S phase of the cell cycle before being distributed to daughter cells in mitosis. Both S phase and mitosis in turn consist of an intricately ordered sequence of molecular events. How cell cycle ordering is achieved, to promote healthy cell proliferation and avert insults on genomic integrity, has been a theme of Paul Nurse's research. To explain a key aspect of cell cycle ordering, sequential S phase and mitosis, Stern & Nurse proposed ‘A quantitative model for cdc2 control of S phase and mitosis in fission yeast’. In this model, S phase and mitosis are ordered by their dependence on increasing levels of cyclin-dependent kinase (Cdk) activity. Alternative mechanisms for ordering have been proposed that rely on checkpoint controls or on sequential waves of cyclins with distinct substrate specificities. Here, we review these ideas in the light of experimental evidence that has meanwhile accumulated. Quantitative Cdk control emerges as the basis for cell cycle ordering, fine-tuned by cyclin specificity and checkpoints. We propose a molecular explanation for quantitative Cdk control, based on thresholds imposed by Cdk-counteracting phosphatases, and discuss its implications

Gabrielle Cadier‑Rey (études réunies par), Femmes protestantes au xixe‑xxe siècles, Bulletin de la Société de l’Histoire du Protestantisme français

Les protestantes et leur contribution à l’émancipation des femmes sont sorties d’une zone d’ombre ces dernières années. Pourtant il reste encore beaucoup à apprendre sur les divers champs d’intervention et les luttes multiformes que rappelle Michelle Perrot, dans l’introduction de ce numéro thématique du Bulletin de la Société de l’Histoire du Protestantisme français : éducation des jeunes enfants, aide à l’enfance en difficulté, santé, hôpitaux, prisons… La modernité de l’analyse des protest..

Gas-phase basicities of polyfunctional molecules. Part 2 : saturated basic sites

International audienc

Nanofiltratio of glucose and sodium lactate solutions Variations of retention between single- and mixed-solute solutions

The aim of this work was to investigate NF as a purificatio step, i.e. sugar removal, in the production process of lactic acid from sodium lactate fermentation broth. Experiments were carried out with the Desal 5 DK membrane and solutions of increasing complexity, i.e. single-solute solutions of sodium lactate and glucose and mixed-solute solutions containing both solutes. Concentrations close to those of a fermentation broth were chosen. Experimental results were used to get the variations of the intrinsic retention versus the permeation flu in order to achieve comparisons without the interference of concentration polarization. Quite distinct retentions were obtained for glucose and sodium lactate in single-solute solutions so that the purificatio was expected to be feasible. However, it is pointed out that glucose retention is significantl lower in mixed-solute solutions, i.e. when sodium lactate is present. This decrease is such that the retentions of both solutes become comparable so that any purificatio is unachievable. Experiments were also performed with a salt of a different nature (mineral salt, NaCl). Again, it was found that the presence of NaCl tends to decrease glucose retention. Moreover, the phenomenon is shown to be related to the salt concentration in both cases, i.e. with sodium lactate and NaCl. Some possible explanations of this effect are provided in this paper. Further investigations are still in progress to improve the knowledge of the mechanisms involved

Modélisation du RMI et trajectoires des allocataires. Une analyse empirique des liens RMI-marché du travail à partir de données individuelles

Le dispositif RMI combine une allocation différentielle, un accès aux droits sociaux et des mesures de suivi ou d'incitation. Depuis sa création en 1988, son fonctionnement réel permet de distinguer trois logiques d'intervention ; revenu de subsistance ; complément salarial et allocation de chômage. Cette pluralité s'accompagne d'une hétérogénéité des bénéficiaires et de leurs trajectoires. L'analyse propose une représentation qui permet de mieux situer le dispositif dans le système de protection sociale et dans la régulation du marché du travail auquel il participe. Elle utilise les données de l'enquête de la DREES réalisée en juin 2006 auprès d'un échantillon d'allocataires permettant de reconstituer leurs trajectoires sur une période de 18 mois et de caractériser le rapport qu'ils entretiennent vis à vis des institutions. Nous précisons en premier lieu les particularités des différents groupes dans l'espace des observations de l'enquête en proposant une modélisation (section 1). On examine les proximités et les différences qui caractérisent ces groupes (section 2). On observe ensuite les relations qu'ils entretiennent avec les institutions du marché du travail et de la protection sociale (section 3). On précise enfin leurs trajectoires longues (section 4).Revenu minimum, pauvreté, marché du travail, trajectoires.