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The recovery of valuable compounds from food wastes and by-products kills two birds with one stone and addresses both the use of by-products and societal health care. Traditional extraction methods include usually high-temperature treatment (more than 100°C) with the subsequent risk of thermal denaturation or transformation of the target molecules. Moreover, these techniques are very time-consuming and require relatively large quantities of solvents. On the other hand, the use of environment-friendly technologies has led researchers and the food industry to develop new alternative processes that can extract valuable compounds from different sources and food wastes of different origins. This chapter describes the potential use of emerging technologies such as ultrasound-assisted extraction, laser ablation, pulsed electric fields, high-voltage electrical discharge, membrane-assisted extraction, and solvent-induced complexation. The latest methodologies comply with the concepts of green chemistry and sustainability.

BACKGROUND: Bioconversion broths are complex media with microorganisms that convert substrates into products in the presence of salts and nitrogen sources and that may release biomolecules. This paper deals with the impact of bioconversion broth components on the membrane‐based reactive extraction of 3‐hydroxypropionic acid (3‐HP) by tri‐n‐octylamine (TOA) in n‐decanol in preparation for an in situ product recovery. The focus here is on the influence of 3‐HP concentration (0.5–10 g L⁻¹), initial pH of the solution (3–5) and presence of proteins and salts on the extraction yield and kinetics. RESULTS: It was found that reducing the initial acid concentration caused an acceleration of the extraction kinetics because of a higher extent of complexation with TOA. pH effects were dramatic, as enhancing the pH from 3 to 5 decreased the extraction yield from 74% to only 5% due to acid dissociation. Proteins were shown to have negligible impact on the extraction yield and kinetics, probably because of their negligible mass transfer resistance at the liquid–liquid interface compared with the membrane. Conversely, the presence of salts (potassium chloride and potassium biphosphate) was highly detrimental. The decrease in extraction yield was shown to be due to an anion exchange between the carboxylate anion of 3‐HP in the organic phase and the anion of the salt in the aqueous phase. Chloride ions had more impact than biphosphate ions. CONCLUSION: These results give valuable information for the implementation of a membrane‐based reactive extraction as an in situ product recovery process, suggesting recommendations for bioconversion tuning. © 2018 Society of Chemical Industry

BACKGROUND: 3-hydroxypropionic acid (3-HP) microbial synthesis through glycerol bioconversion by Lactobacillus reuteri is at the moment characterized by too low performances to consider production at industrial scale. To avoid its toxic accumulation in the medium and to recover this molecule of interest, 3-HP in situ reactive extraction from bioconversion broth was investigated using a hollow fiber membrane contactor (HFMC) in order to intensify its production. The so-called integrated system was compared with the conventional bioconversion system. The impact of the extractive bioconversion on the overall production performance and on cell physiological state was studied. RESULTS: Results underlined drastic inhibitory effects on the producing bacteria, especially under extractive bioconversion conditions despite the use of a HFMC supposed to avoid direct contact between organic phase and bacteria. Indeed, the extractant phase components (trioctylamine in n-decanol) were found to be toxic for the cells (due to solubility and by direct contact). These phenomena were increased by the presence of 3-hydroxypropionaldehyde (3-HPA) and 3-HP produced during glycerol bioconversion. These cumulative effects induced complete loss of the cellmembrane integrity and esterase activity after 1.5 h of extractive bioconversion. When the bioconversion was conducted alone, the bacterial inhibition was lower, as around 50% of L. reuteri cells remained active with unaltered membrane after 3 h. Hypotheses concerning the mechanisms of action of the observed inhibitions were proposed and discussed.

BACKGROUND: 3‐Hydroxypropionic acid (3‐HP) production through glycerol bioconversion by Lactobacillus reuteri suffers from low yields and productivities due to product inhibition. Reactive extraction assisted by a Hollow Fibre Membrane Contactor (HFMC) is a promising strategy for process intensification. However, the use of this integrated system is hindered by extraction phase toxicity towards the microorganism. This study describes a solvent selection strategy based on extraction performance (extraction yield and viscosity, related to mass transfer), and a low solvent toxicity, in order to find an extraction phase composition that allows continuous in stream extraction of 3‐HP. RESULTS: Inert diluent addition to a trioctylamine (TOA)‐decanol mixture decreased its toxicity and viscosity but decreased extraction yield. The linear and ramified long‐chain alcohols tested showed that increasing the number of carbon atoms decreased extraction performance as well as toxicity. Ramified alcohols showed the lowest extraction performance. Didodecylmethylamine (DDMA) gave higher extraction yield and lower solvent toxicity than TOA. Flow cytometry with dual staining for cell membrane integrity and enzymatic activity proved to give concordant and complementary information with cell bioconversion ability, being an adequate and quick method for solvent toxicity assessment. The selected organic phase consisted of 20% DDMA, 47% dodecanol and 33% dodecane by volume, and can be used for in‐stream extraction of 3‐HP produced by L. reuteri. CONCLUSIONS: The integrated selection criteria proposed in this study – extraction yield, solvent viscosity and toxicity – provide key information for choosing an organic phase with the best trade‐off between extraction performance and biocompatibility. © 2019 Society of Chemical Industry

BACKGROUND Reactive liquid–liquid extraction is a promising technique for the direct recovery of carboxylic acids from bioconversion media. This work focused on the optimization of 3-hydroxypropionic acid (3-HP) reactive extraction assisted by hollow-fiber membrane contactor (HFMC), using tri-n-octylamine (TOA) and Aliquat 336 as extractants in n-decanol, and on its practical application for the recovery of 3-HP obtained from glycerol bioconversion by Lactobacillus reuteri. RESULTS The results underlined the influence of the initial pH and 3-HP concentration of the aqueous medium and the impact of extractant phase composition on the extraction performances. The highest distribution coefficient of 3-HP (KD = 13.0) was observed at pH = 3 with 10% v/v TOA mixed with 10% v/v Aliquat 336 in n-decanol. This study showed that the acid concentration and the ratio of amines used between TOA and Aliquat 336 in n-decanol did not have a great impact on the KD during 3-HP reactive extraction, whereas it had an influence on the extraction kinetics. Moreover, 3-HP reactive extraction assisted by HFMC from real bioconversion broth with glycerol as the substrate was shown to be feasible, with the same order of magnitude of extraction kinetics but with a lower KD compared with reactive extraction using model broth. CONCLUSIONS 3-HP was predominantly extracted from the bioconversion broth, confirming the high selectivity of the extraction process studied and the high potential of this approach applied to the biotechnological production of 3-HP. © 2016 Society of Chemical Industry

International audience; Reactive extraction is a well-known method for the recovery of organic acids from dilute streams. The extraction through complex formation with amines is followed by its back-extraction. Their affinity for amine extractants makes their back-extraction a limiting step. The case of 3-hydroxypropionic acid is addressed here. Three methods were compared: salts additions, diluent swing and temperature swing. Mineral bases led to complete 3-HP recovery but as a salt. Diluent swing was tested using n-hexane as the anti-solvent. Results showed that increasing the n-hexane content led to a great increase of 3-HP recovery. However, high recovery yields are associated with high dilutions. The temperature was varied from 4 to 140 °C and it led to a high decrease of the acid-amine complex formation. Our thermochemical study showed an apparent heat of reaction of-25.3 kJ/mol and, at 140 °C, 78% of 3-HP can be recovered in a single step.

BACKGROUND Bioconversion is a promising route to produce bio-based building blocks such as 3-hydroxypropionic acid (3-HP). Reactive extraction can be used for 3-HP recovery, and ultimately integrated to the bioconversion process. To the best of our knowledge, there is no published experimental data about the reactive extraction of 3-HP. This work aimed to study the extraction of 3-HP using tri-n-octylamine and Aliquat 336 as extractants in n-decanol. Comparison was also made with its positional isomer, lactic acid. Finally, the extraction of 3-HP from model and real bioconversion broths was examined. RESULTS The use of mixed extractants showed high performances over a wide range of experimental conditions, highlighting a synergistic effect. A possible extraction mechanism considers the formation of a ternary complex between TOA, Aliquat 336 and the carboxylic acid. When 3-HP was extracted from a real bioconversion broth, some cell-originating compounds were suspected to adsorb to the aqueous–organic interface. This effect, added to the possible competition between 3-HP and compounds that can react with the extractants, led to limitations in the yield (Y%) and selectivity (α3HP) of the extraction. For example, Y% and α3HP were respectively 89% and 35.9 for the model bioconversion broth and decreased to 62% and 15.7 for the real broth at pH = 3.2. CONCLUSION Effective experimental conditions for the reactive extraction of 3-HP were pointed out for the first time. Further work will be undertaken with a view to better elucidating the mechanisms involved in real conditions of an integrated extractive bioconversion system. © 2015 Society of Chemical Industry

International audience; The present study aims at comparing the performances of three Lactobacillus reuteri strains (DSM 20016, DSM 17938, and ATCC 53608) in producing 3-hydroxypropionic acid (3-HP) from glycerol and at exploring inhibition phenomena during this bioconversion. Differences were highlighted between the three strains in terms of 3-HP production yield, kinetics of substrate consumption, and metabolite production. With a maximal productivity in non-optimal conditions (free pH) around 2 g.L−1.h−1 of 3-HP and 4 g.L−1.h−1 of 3-hydroxypropionaldehyde (3-HPA) depending on the strain, this study confirmed the potential of L. reuteri for the biotechnological production of 3-HP. Moreover, the molar ratios of 3-HP to 1,3-propanediol (1,3-PDO) obtained for the three strains (comprised between 1.25 and 1.65) showed systematically a higher 3-HP production. From these results, the DSM 17938 strain appeared to be the most promising strain. The impact of glycerol bioconversion on the bacteria’s physiological state (a decrease of around 40 % in DSM 17938 cells showing an enzymatic activity after 3 h) and survival (total loss of cultivability after 2 or 3 h depending on the strains) was revealed and discussed. The effect of each metabolite on L. reuteri DSM 17938 was further investigated, displaying a drastic inhibition caused by 3-HPA, while 3-HP induced lower impact and only at acidic pH.

International audience; This study deals with the production of isoamyl acetate (IAA) by fermentation of sugar cane molasses with the strain Pichia fermentans ITD00165, using L-leucine as precursor. A mathematical model that describes the experimental data from fermentation was developed for its use as a tool for further process optimization. The fermentation system was constantly aerated and coupled to liquid–liquid in situ extraction with decane as the recovery solvent. Thus, the model integrates the biological production of IAA, its partition coefficient in the two liquid phase system and the stripping effect of aeration. A productivity of 26 mg L−1 h−1 was obtained with addition of 4 g L−1 of L-leucine at 12 h of fermentation. The use of the model for process optimization was explored. According to it, the maximum theoretical productivity that can be obtained is 63 mg L−1 h−1. The model was used to determine that 1.6 g L−1 is the minimum concentration of L-leucine that can be added without significantly reducing IAA production. Also, it makes possible to propose an adequate decane/culture medium ratio, to have a desired final concentration and amount of recovered IAA. This value can be adjusted based on the needs of further purification steps and is useful to define a global economic optimum of the process.

A comprehensive study of equilibrium states involved in the reactive extraction of 3-hydroxypropionic acid (3-HP) by tri- n -octylamine (TOA) in n -decanol is described. Complexation phenomena between 3-HP and TOA were revealed by infrared spectroscopy (FT-IR). This study demonstrated that the main extraction mechanism is the formation of an ion pair involving the dissociated form of 3-HP. Chemical models were then formulated, taking the formation of the ion pair between 3-HP and TOA and the influence of the amount of solvent in the organic phase into account. Two models are proposed: (1) a stoichiometric model where the solvent is seen as a reagent that is involved in the complexation as a synergistic extractant, but with competition for solvation via H-bond interactions with TOA; (2) a model where the solvent is seen as a phase modifier that improves the physicochemical properties of the extractant and that changes the complexation equilibrium. Both models describe the extraction yields in the investigated ranges, with Model (2) being particularly predictive since it provides a mean absolute prediction error of less than 2% in yield units. According to this latter model, the complexation equilibrium coefficient increases with the increase of the n -decanol proportion in the organic phase. Model (2) shows that solvation effects are better described as non-stoichiometric interactions. Therefore, the two mechanistic models accurately represent extraction yields over a wide range of initial conditions and are potentially transposable to other reactive extraction systems. Such knowledge is essential for further implementation of downstream processes.

The aims of this study is to compare the growth and glucose metabolism of three Lactobacillus reuteri strains (i.e. DSM 20016, DSM 17938, and ATCC 53608) which are lactic acid bacteria of interest used for diverse applications such as probiotics implying the production of biomass, or for the production of valuable chemicals (3-hydroxypropionaldehyde, 3-hydroxypropionic acid, 1,3-propanediol). However, the physiological diversity inside the species, even for basic metabolisms, like its capacity of acidification or glucose metabolism, has not been studied yet. In the present work, the growth and metabolism of three strains representative of the species diversity have been studied in batch mode. The strains were compared through characterization of growth kinetics and evaluation of acidification kinetics, substrate consumption and product formation. The results showed significant differences between the three strains which may be explained, at least in part, by variations in the distribution of carbon source between two glycolytic pathways during the bacterial growth: the phosphoketolase or heterolactic pathway (PKP) and the Embden-Meyerhof pathway (EMP). It was also shown that, in the context of obtaining a large amount of biomass, DSM 20016 and DSM 17938 strains were the most effective in terms of growth kinetics. The DSM 17938 strain, which shows the more significant metabolic shift from EMP to PKP when the pH decreases, is more effective for lactate production.

Traditional extraction methods include usually high temperature treatment (more than 100°C) with the subsequent risk of thermal denaturation or transformation of the target molecules. Moreover, these techniques are very time-consuming and require relatively large quantities of solvents. On the other hand, the use of environmentally friendly technologies has led researchers and the food industry to develop new alternative processes that can extract valuable compounds from different sources and food wastes of different origin. This chapter describes the potential use of emerging technologies such as ultrasound-assisted extraction (UAE), laser ablation, pulsed electric fields (PEF), high voltage electrical discharge (HVED), and membrane-assisted extraction. The latest methodologies comply with the concepts of green chemistry and sustainability within the food industry.

The pervaporation properties of a methylated-silica membrane were studied on binary ethanol/water and ternary ethanol/water/methanol mixtures. The aim was to acquire a better understanding of the pervaporation mechanisms by studying the effects of feed temperature, permeate pressure, and feed composition on molecular transport. Emphasis was placed on the role of competitive adsorption and dragging and blocking effects between the components in the context of the adsorption-diffusion model. The results show the potential of the membrane for the coupled removal of water and methanol from bioethanol. This attractive application for process intensification was suggested for the first time in this paper.

International audience; Hydrophilic membrane pervaporation is largely described as a promising alternative to molecular sieves and azeotropic distillation, the ordinary techniques for ethanol dehydration (1). Three major types of membranes have been studied: i) organic (polymeric) membranes, ii) inorganic membranes and iii) hybrid membranes. Polymeric membranes remain the most widely used for pervaporation in the industry. These membranes are attractive because of their economical and fabrication advantages. During the last 10 years, considerable efforts have been put in the development of inorganic and hybrid membranes as they show a better chemical, hydrothermal and mechanical stability and are free of swelling.Extensive research works have been focused on optimization of membrane material and operation parameters to maximize flux and water selectivity (2, 3). However, most of these works reported permeation data without systematically analyzing the contribution of the intrinsic parameters, i.e. membrane permeability (adsorption-diffusion through the membrane) and driving force. Moreover, in most cases, experiments were performed using ethanol that has undergone several distillations to remove volatile organic compounds (VOCs) impurities. Ethanol obtained from agricultural residues and lignocellulosic biomass contains high amount of impurities, mainly (VOCs). For example, the fermentation of grape marc produces bioethanol that contains up to 40000 ppm of methanol, some aldehydes, long chain alcohols and esters in smaller quantities, which can modify the perm-selectivity performances of pervaporation membranes.This work aimed to study the performances of three pervaporation membranes: polymeric (PVA), inorganic (Me-Si®) and hybrid (HybSi®) used for ethanol dehydration. These membranes were compared in terms of permeance, flux and selectivity using pure, binary (ethanol + water), ternary (ethanol + water + methanol) and complex (grape marc bioethanol) mixtures. Emphases have been put on drag and competitions effects involved between molecules depending on feed mixture complexity. 1.Bolto, B., M. Hoang, and Z. Xie. 2011. A review of membrane selection for the dehydratation of aqueous ethanol by pervaporation. Chemical Engineering and Processing: Process Intensification 50:227-235.2.Casado, C., A. Urtiaga, D. Gorri, and I. Ortiz. 2005. Pervaporative dehydration of organic mixtures using a commercial silica membrane: Determination of kinetic parameters. Separation and Purification Technology 42:39-45.3.Sommer, S., and T. Melin. 2005. Influence of operation parameters on the separation of mixtures by pervaporation and vapor permeation with inorganic membranes. Part 1: Dehydration of solvents. Chemical Engineering Science 60:4509-4523.

In this paper, emphasis has been put on the relationship between volume compression and cell inactivation for the Saccharomyces cerevisiae strain CBS 1171 submitted to high hydrostatic pressure treatments. The influence of cell dehydration on pressure inactivation was first investigated. Inactivation was found to be strongly limited, or even completely prevented for cells with a water content of 60% w/w or below. Moreover, the volume compression undergone by a single yeast cell was assessed as a function of pressure and hydration conditions using a high-pressure setup for pressure-volume-temperature measurements. Direct measurements of volume compression were performed on cell pellets after being equilibrated in air at different relative humidity levels (yeast powders). Yeast cells suspended in water-glycerol were assumed to be composed of two compartments: the cytoplasm and the dry matter. The compression of the cell cytoplasm was assumed to be similar to that obtained for water-glycerol mixtures at the same water content. The compression of the dry matter was measured on yeast powder at a(w) = 0.11. Results showed that the magnitude of cell volume compression increased with pressure level. At a given pressure level, cells in a hydrated state underwent higher volume compression than the dehydrated ones. Cell inactivation and volume compression data were then taken together in order to highlight their parallel behaviors. An attempted correlation showed that a cell volume compression of near 10 mu m(3) would be a critical value for cell inactivation. Accordingly, inactivation occurs only when the cell undergoes a sufficient volume compression, regardless of the pressure level. From the thermodynamic point of view, the pressure-induced volume compression indicates the amount of mechanical energy (work of compression) transferred to the cell system. It was suggested that damages at the cellular level, such as the membrane permeabilization, would occur when cells undergo a sufficient volume compression, i.e. mechanical stress and energy. The involvement of protein denaturation, compression of membrane phospholipids, as well as differential in compression between the cell cytoplasm and the plasma membrane, were discussed as possible events leading to cell permeabilization. Cells with compromised membrane integrity are subjected to uncontrolled mass transfers that could lead to inactivation under pressure. (C) 2013 Elsevier Ltd. All rights reserved.

International audience

Hydrophilic membrane pervaporation is largely described as a promising alternative to molecular sieves and azeotropic distillation, the ordinary techniques for ethanol dehydration(6,7). Pervaporation is considered as more flexible, cleaner and less energy consuming technology. (...)

International audience; The role of water in microorganism viability was assessed through the application of combined physical perturbations. The combination of different physical parameters could allow to balance the properties variations (especially water related) resulting from the increase of one parameter alone. Thus, it is possible to optimize the survival of cells in controlling these parameters. This was tested through two different examples. The first example shows that combination of osmotic level and temperature can allow optimizing yeast cell survival in following membrane fluidity variation. Moreover this analysis has allowed a better comprehension of cell inactivation during rehydration and especially the impact of intracellular vesiculation during dehydration. The second example deals with the effect of combination of high hydrostatic pressure, low temperature and water activity of the medium, on resistance Escherichia coli cells. These experiments show that synergetic effect of high pressure and low temperature was only observed at pressure lower than 300 MPa and high water content. Otherwise, low temperature as well as low water activity protects the microorganisms from inactivation even at extreme pressure level (P > 600 MPa). These two examples show the implication of water thermodynamical properties and their preservation on cell survival even after extreme treatment conditions. Preservations process would certainly benefit from extensions of this knowledge.

National audience; 1. ContexteCette étude se déroule dans le cadre d’un projet financé par l’ADEME en réponse à l’appel à projets Bioressources Industries Performances 2008, projet intitulé MIDIPER (Étude de la faisabilité technico-économique d’une MIniDIstillerie proche des ressources et des besoins, équipée d’un système de déshydratation par membranes de PERméation). Ce projet s’intéresse à la production d’éthanol biocarburant à l’échelle d’une distillerie viti-vinicole. L’implantation d’une nouvelle technologie membranaire pour la déshydratation de l’éthanol pourra permettre de réduire les consommations d’énergie, promouvoir la production d’énergies renouvelables et diversifier les matières premières.Le projet MIDIPER réunit 4 partenaires : •L’Union Nationale de Groupement de Distillateurs d’Alcool (UNGDA) ;•La société d’ingénierie HONORE SAS ;•La Société Française de Distillerie (SFD) qui fait partie de l'Union des Distilleries de la Méditerranée (UDM) ;•L’UMR GMPA, INRA-AgroParisTech, Génie et Microbiologie des Procédés Alimentaires.Une convention de collaboration a été cosignée dans le cadre de ce projet par les différents partenaires et la société VAPERMA Inc.2. Problématique & objectifsLe bioéthanol est l’une des sources prometteuses d’énergie renouvelable alternative à l’énergie fossile fortement émettrice de CO2. Traditionnellement, le bioéthanol est utilisé comme produit de base pour la production d'ETBE. Il peut être également mélangé à l'essence dans une proportion de 5 à 10% (E10) ou majoritairement dans l’E85 (85% d’éthanol), ou mélangé à des teneurs variables à des distillats (gazole), mélanges qui nécessitent l’utilisation de l’éthanol déshydraté à 98,7% m/m selon la réglementation européenne (NF EN 15376 :2008-03).L’éthanol anhydre ne peut pas être obtenu directement par rectification, l’éthanol formant un azéotrope avec l’eau pour une composition de 95,6% m/m en éthanol. De ce fait, la séparation de ces deux composés est impossible par un principe d’équilibre liquide-vapeur à pression atmosphérique. Les techniques classiquement employées pour la déshydratation de l’éthanol sont :•La distillation azéotropique, avec adjonction d’un tiers corps pour briser l’azéotrope (souvent le cyclohexane après interdiction du benzène) : cette méthode nécessite une étape de séparation additionnelle pour éliminer le tiers corps et est de moins en moins employée pour limiter l’emploi de solvants.•L’adsorption sur tamis moléculaire : cette méthode emploie des zéolithes dont la taille, la forme et la nature permettent l’adsorption sélective des molécules d’eau. Une étape de régénération du lit de zéolithes est nécessaire, énergivore car utilisant de l’éthanol anhydre sous forme vapeur.Une alternative innovante à ces deux méthodes très consommatrices d’énergies, est l’emploi des techniques séparatives à membranes de pervaporation et de perméation de vapeur. Ces techniques mettent en jeu l’affinité entre la face amont d’une membrane dense (hydrophile et non poreuse) et les molécules d’eau contenues dans la phase d’alimentation liquide (pervaporation) ou gazeuse (perméation de vapeur). L’eau diffuse au travers de la membrane avant d’être désorbée sous forme vapeur de l’autre côté de la membrane. La force motrice du transfert en technique de perméation est la différence de pression partielle de la vapeur d’eau entre les deux faces de la membrane. Ce gradient de pression est maintenu suffisant grâce à l’augmentation de la pression d’alimentation en amont et l’application du vide en aval de la membrane (Schafer and Crespo 2005).Les techniques de pervaporation et de perméation de vapeur permettent une déshydratation en continu de l’éthanol. Elles sont modulables et s’intègrent parfaitement dans un schéma énergétique global économe pour la production de bioéthanol.Il existe actuellement sur le marché des modules membranaires quelques technologies utilisables dans le processus de déshydratation de l'éthanol. Nous utilisons dans le cadre de cette étude la membrane polymérique à fibre creuse SiftekMC, à base de polyimides, développée et brevetée au Canada, aux USA et en Europe (Cranford and Roy 2006). Des études préliminaires réalisées pendant l’élaboration et la mise au point de cette membrane ont montré son fort potentiel pour la perméation sélective de l’eau contenue dans des solvants organiques (Cranford et al. 1999; Huang et al. 2004).Ce travail est donc axé sur l’étude du potentiel de la technologie SiftekMC de perméation de vapeur pour la déshydratation de l’éthanol jusqu’à une teneur supérieure ou égale à 98,7 % m/m en éthanol. Nous nous attacherons également à mieux comprendre les mécanismes de transfert des molécules mises en jeu via une approche de modélisation.3. Avancement de l’étudeDans le cadre du projet MIDIPER, la conception d’un équipement à l’échelle pilote a été effectuée, afin de réaliser l’étude de faisabilité technique. Ce pilote comprend un module membranaire fibre creuse SiftekMC de 4 m² intégré au sein d’une installation complète permettant l’évaporation d’une matière première contenant de l’éthanol, la surchauffe de la vapeur obtenue, le transfert de cette vapeur dans le module membranaire et la récupération des phases perméat (principalement l’eau extraite de la vapeur d’alimentation) et rétentat (éthanol déshydraté).La démarche expérimentale a consisté dans un premier temps à établir le fonctionnement optimal du pilote afin de pouvoir étudier l’influence des conditions opératoires sur le procédé de déshydratation. Les essais ont été réalisés en utilisant des solutions hydro-alcooliques modèles à différentes concentrations. Ces essais ont permis de définir les capacités du module membranaire fibre creuse SiftekMC (débit, facteur d’enrichissement, sélectivité) et de comparer les résultats obtenus aux courbes théoriques de fonctionnement d’un procédé de perméation. Des contraintes liées à la conduite du procédé ont été identifiées et des améliorations ont été apportées.L’emploi d’éthanol d’origine vinique (alcool brut issu de marc de raisin) présentant un potentiel de valorisation à l’échelle locale comme biocarburant, l’utilisation de cette technologie de déshydratation a été évaluée, le potentiel de cet alcool étant freiné actuellement par des teneurs élevées en composés organiques volatils (COV), et notamment le méthanol. La diminution de la teneur en COV peut être réalisée par une rectification spécifique, mais il est intéressant de déterminer l’aptitude du module membranaire seul à en diminuer la teneur pour cette application biocarburant.Cranford RJ, Darmstadt H, Yang J, Roy C (1999) Polyetherimide/Polyvinylpyrrolidone Vapor Permeation Membranes. Physical and Chemical Characterization. Journal of Membrane Science 155:213-240Cranford RJ, Roy C; 2006 Jun. 8. Solvent Resistant Asymmetric Integrally Skinned Membranes. US Patent # 7,556,677 B2. July 7th, 2009.Huang J, Cranford RJ, Darmstadt H, Matsuura T, Roy C (2004) Sorption and Transport Behavior of Water Vapor in Dense and Asymetric Polyimide Membranes. Journal of Membrane Science 241:187-196Schafer T, Crespo JG (2005) Vapor Permeation and Pervaporation. In: Afonso CAM, Crespo JG, Editors. Green Separation Processes. Weinheim: Wiley-Vch. p 271-289.

International audience; We investigated the influence of cell hydration on the ability of Saccharomyces cerevisiae CBS 1171 to withstand extreme hydrostatic pressure in order to determine the mechanisms involved in cell resistance. Hydration conditions were modified in two different ways. We first modulated the chemical potential of water by adding glycerol in cell suspensions. Another procedure consisted in dehydrating cells aerobically and immersing them in perfluorooctane, an innocuous hydrophobic liquid used as a pressure-transmitting medium, prior to pressure treatments. This original method made it possible to transmit isostatic pressure to yeast powders without changing the initial water activity (a w) level at which cells had been equilibrated. The a w ranged between 0.11 and 0.99. Pressure treatments were applied at levels of up to 600 MPa for 10 min, 24 h, and 6 days. The dehydration of cells was found to strongly limit, or even prevent, cell inactivation under pressure. Notably, cells suspended in a water–glycerol mixture with a w levels of 0.71 or below were completely protected against all pressure treatments. Moreover, cells dehydrated aerobically survived for 6 days at 600 MPa even when a w levels were relatively high (up to 0.94). We highlighted the crucial role of water content in determining cellular damage under pressure. When water is available in a sufficient amount, high pressure induces membrane permeabilization, causing uncontrolled mass transfers that could lead to death during a prolonged holding under pressure. Possible mechanisms of membrane permeabilization are discussed.

L'utilisation de la haute pression hydrostatique constitue potentiellement, au niveau de l'industrie alimentaire, une innovation comparable a celles apportees en leur temps par l'utilisation du cuiseur pression ou des microondes. Cependant, cette revolution est encore grandement freinee par l'incapacite de fournir cette technologie a faible cout aux industriels, et encore moins au grand public. Les applications de la haute pression hydrostatique a l'industrie agroalimentaire sont nombreuses et variees. Elles couvrent des operations unitaires comme la pasteurisation, la sterilisation, le blanchiment, la congelation/decongelation, la texturation, le formage, l'extraction, l'emulsification, le confisage, ou encore la maturation, et de nouvelles applications sont regulierement proposees. L'apport de cette technologie a ces transformations est tout a fait original car les produits obtenus par haute pression ne peuvent souvent pas etre reproduits par d'autres techniques. La cle de la reussite de l'application de cette technologie reside dans la bonne connaissance de ce qu'est la pression et de ses effets sur la matiere et, en particulier, de celle qui constitue les aliments. Ces deux points fondamentaux seront abordes successivement dans les deux premiers paragraphes de ce dossier. L'action de la pression sur les microorganismes, qui reste l'effet majeur de la pression pour l'application alimentaire, sera ensuite consideree avant d'explorer l'ensemble des applications alimentaires des hautes pressions identifiees a ce jour.

The survival of cells subjected to cooling at sub-zero temperature is of paramount concern in cryobiology. The susceptibility of cells to cryopreservation processes, especially freeze-thawing, stimulated considerable interest in better understanding the mechanisms leading to cell injury and inactivation. In this study, we assessed the viability of cells subjected to cold stress, through long-term supercooling experiments, versus freeze-thawing stress. The viability of Escherichia coli, Saccharomyces cerevisiae, and leukemia cells were assessed over time. Supercooled conditions were maintained for 71 days at -10 degrees C, and for 4 h at -15 degrees C, and -20 degrees C, without additives or emulsification. Results showed that cells could be inactivated by the only action of sub-zero temperature, that is, without any water crystallization. The loss of cell viability upon exposure to sub-zero temperatures is suggested to be caused by exposure to cold shock which induced membrane damage. During holding time in the supercooled state, elevated membrane permeability results in uncontrolled mass transfer to and from the cell maintained at cold conditions and thus leads to a loss of viability. With water crystallization, cells shrink suddenly and thus are exposed to cold osmotic shock, which is suggested to induce abrupt loss of cell viability. During holding time in the frozen state, cells remain suspended in the residual unfrozen fraction of the liquid and are exposed to cold stress that would cause membrane damage and loss of viability over time. However, the severity of such a stress seems to be moderated by the cell type and the increased solute concentration in the unfrozen fraction of the cell suspension.

The relationship between membrane permeability, changes in ultrastructure, and inactivation in Escherichia coli strain K-12TG1 cells subjected to high hydrostatic pressure treatment at room and subzero temperatures was studied. Propidium iodide staining performed before and after pressure treatment made it possible to distinguish between reversible and irreversible pressure-mediated cell membrane permeabilization. Changes in cell ultrastructure were studied using transmission electron microscopy (TEM), which showed noticeable condensation of nucleoids and aggregation of cytosolic proteins in cells fixed after decompression. A novel technique used to mix fixation reagents with the cell suspension in situ under high hydrostatic pressure (HHP) and subzero-temperature conditions made it possible to show the partial reversibility of pressure-induced nucleoid condensation. However, based on visual examination of TEM micrographs, protein aggregation did not seem to be reversible. Reversible cell membrane permeabilization was noticeable, particularly for HHP treatments at subzero temperature. A correlation between membrane permeabilization and cell inactivation was established, suggesting different mechanisms at room and subzero temperatures. We propose that the inactivation of E. coli cells under combined HHP and subzero temperature occurs mainly during their transiently permeabilized state, whereas HHP inactivation at room temperature is related to a balance of transient and permanent permeabilization. The correlation between TEM results and cell inactivation was not absolute. Further work is required to elucidate the effects of pressure-induced damage on nucleoids and proteins during cell inactivation.

The combined effects of subzero temperature and high pressure on the inactivation of Escherichia coli K12TG1 were investigated. Cells of this bacterial strain were exposed to high pressure (50 to 450 MPa, 10-min holding time) at two temperatures (−20°C without freezing and 25°C) and three water activity levels (a w ) (0.850, 0.992, and ca. 1.000) achieved with the addition of glycerol. There was a synergistic interaction between subzero temperature and high pressure in their effects on microbial inactivation. Indeed, to achieve the same inactivation rate, the pressures required at −20°C (in the liquid state) were more than 100 MPa less than those required at 25°C, at pressures in the range of 100 to 300 MPa with an a w of 0.992. However, at pressures greater than 300 MPa, this trend was reversed, and subzero temperature counteracted the inactivation effect of pressure. When the amount of water in the bacterial suspension was increased, the synergistic effect was enhanced. Conversely, when the a w was decreased by the addition of solute to the bacterial suspension, the baroprotective effect of subzero temperature increased sharply. These results support the argument that water compression is involved in the antimicrobial effect of high pressure. From a thermodynamic point of view, the mechanical energy transferred to the cell during the pressure treatment can be characterized by the change in volume of the system. The amount of mechanical energy transferred to the cell system is strongly related to cell compressibility, which depends on the water quantity in the cytoplasm.

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National audience; This work was aimed to study the performance of a new hydrophilic hallow-fiber and asymmetric polyimide membrane in dehydrating grape marc bioethanol using a vapor permeation pilot-plant. Grape marc bioethanol with variable concentrations in volatile organic compounds (VOC) was used. Concentration in water, ethanol and VOC were determined in permeate and retentate phases in order to calculate membrane selectivity and flux. Mass transfer mechanisms were then analyzed by taking into account the thermodynamic properties of the different molecules and the properties of membrane materials.Results showed that continuous dehydration of grape marc bioethanol up to 0.3% w/w of residual water was possible using the membrane module studied, in conformity with the UE regulation. Moreover, it was shown that this new membrane was able to reduce the amount of methanol in grape marc bioethanol during its dehydration.Taken together with advantages in term of energy consumption and CO2 emission, these promising results highlight the positioning of this membrane process with regard to the traditional techniques used for ethanol dehydration in the world industry (azeotropic distillation, dehydration on molecular sieves).Key words: grape marc bioethanol, dehydration, vapour permeation, selectivity, flux.; Ce travail est axé sur l’étude du potentiel de trois types de membranes de déshydratation : organique en polyimides, minérale en silicium et hybride (technologie HybSi) pour la déshydratation de l’éthanol jusqu’à une teneur supérieure ou égale à 99,7 % m/m en éthanol. La démarche expérimentale a consisté dans un premier temps à établir le fonctionnement optimal du procédé préalablement à l’étude de l’influence des conditions opératoires sur les performances du procédé de déshydratation, en mode de perméation de vapeur et de pervaporation. Les essais de déshydratation ont ensuite été réalisés en utilisant des solutions hydro-alcooliques modèles à différentes concentrations, additionnées de composés organiques volatils. Les performances des membranes testées ont été caractérisées afin de comprendre les mécanismes de transfert de matière et le rôle des composés organiques du milieu sur la sélectivité et le flux membranaires.