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International audience; Yeast hulls can be used to adsorb undesirable compounds such as volatile phenols that may be present in wine. To understand this adsorption process, the properties of the cell walls and their chemical composition need to be better understood. A study was conducted using four different yeast fractions of either autolysed or high-pressure homogeniser (HPH)-crushed yeast biomasses of Saccharomyces cerevisiae and Brettanomyces bruxellensis. Near-infrared spectroscopy (FT-NIR) coupled with X-ray photoelectron spectroscopy (XPS) was used and analysed by principal component analysis (PCA). The FT-NIR spectral region of Saccharomyces and Brettanomyces statistically analysed by PCA showed a clear discrimination accounting for 76% of the variation in the data for PC1; moreover, yeast hulls prepared from the same strain and subjected to two different treatments were also separated. These methods classify yeast cell hulls (YCH) according to strain, composition and treatment applied. Our results indicate that yeast hulls obtained by autolysis are less rich in proteins than those resulting from HPH treatment due to the high pressure that releases more proteins and exposes them on the surface of the cell wall. The composition of YCH at the extreme surface is similar to that found deeper in the wall.

International audience; The role of the initial concentration of anaerobic growth factors (AGF) on interactions between Torulaspora delbrueckii and Saccharomyces cerevisiae was investigated in strict anaerobiosis. Experiments were performed in a synthetic grape must medium in a membrane bioreactor, a special tool designed for studying direct and indirect interactions between microorganisms. In pure culture fermentations, increased AGF concentration had no impact on S. cerevisiae behaviour, whereas it induced an extension of T. delbrueckii latency. Surprisingly, T. delbrueckii used only 75 to 80% of the consumed sugar to produce biomass, glycerol and ethanol. Physical separation influenced the population dynamics of co-fermentations. S.cerevisiae dominated the co-cultures having a single dose of AGF as its presence indirectly induced a decrease in numbers of living T. delbrueckii cells and physical contact with T. delbrueckii stimulated S.cerevisiae growth. Increasing the AGF initial concentration completely upset this domination: S. cerevisiae growth was not stimulated and T. delbrueckii living cells did not decrease. Yeasts incorporate exogenous AGFs, which probably impact their response to competing yeasts. The increase in AGF might have induced changes in the lipid composition of the T. delbrueckii membrane, which would hinder its interaction with S. cerevisiae antimicrobial peptides. The initial concentration of anaerobic growth factors influenced co-culture fermentation population dynamics tremendously, thus highlighting a new way to monitor population evolution and eventually wine organoleptic properties.

International audience; In winemaking, after the alcoholic fermentation of red wines and some white wines, L-malic acid must be converted into L-lactic acid to reduce the acidity. This malolactic fermentation (MLF) is usually carried out by the lactic acid bacteria Oenococcus oeni. Depending on the level of process control, selected O. oeni is inoculated or the natural microbiota of the cellar is used. This study considers the link between growth and MLF for five strains of O. oeni species. The kinetics of growth and L-malic acid consumption were followed in modified MRS medium (20 °C, pH 3.5, and 10 % ethanol) in anaerobic conditions. A large variability was found among the strains for both their growth and their consumption of L-malic acid. There was no direct link between biomass productivities and consumption of L-malic acid among strains but there was a link of proportionality between the specific growth of a strain and its specific consumption of L-malic acid. Experiments with and without malic acid clearly demonstrated that malic acid consumption improved the growth of strains. This link was quantified by a mathematical model comparing the intrinsic malic acid consumption capacity of the strains.

International audience; Traditional tequila fermentation is a complex microbial process performed by different indigenous yeast species. Usually, they are classified in two families: Saccharomyces and Non-Saccharomyces species. Using mixed starter cultures of several yeasts genera and species is nowadays considered to be beneficial to enhance the sensorial characteristics of the final products (taste, odor). However, microbial interactions occurring in such fermentations need to be better understood to improve the process. In this work, we focussed on a Saccharomyces cerevisiae/Kluyveromyces marxianus yeast couple. Indirect interactions due to excreted metabolites, thanks to the use of a specific membrane bioreactor, and direct interaction due to cell-to-cell contact have been explored. Comparison of pure and mixed cultures was done in each case. Mixed cultures in direct contact showed that both yeast were affected but Saccharomyces rapidly dominated the cultures whereas Kluyveromyces almost disappeared. In mixed cultures with indirect contact the growth of Kluyveromyces was decreased compared to its pure culture but its concentration could be maintained whereas the growth of Saccharomyces was enhanced. The loss of viability of Kluyveromyces could not be attributed only to ethanol. The sugar consumption and ethanol production in both cases were similar. Thus the interaction phenomena between the two yeasts are different in direct and indirect contact, Kluyveromyces being always much more affected than Saccharomyces.

Sustainable development is more and more considered as a key parameter and a driving strategy for sustainable performance. Today, numerous organizations develop their own performance indicators as no standard set of performance indicators could be generalized as meaningful in terms of sustainability performance. Particularly, the context of developing countries, where the concept of sustainability is not well diffused yet and where economic difficulties and constraints result most of the times in underestimation of environmental and social considerations, requires specifically adapted indicators. Specially, the sector of health care waste management lacks of sustainability indicators. This sector ensures the treatment, before disposal, of hazardous health care waste generated by health care centers (hospitals, clinics, and others). The evaluation system is designed for monitoring the pace of gaining sustainability within this sector. The objective of this article is to propose a sustainability evaluation system adapted to the needs and situation of developing countries, based on meaningful, practical, easily measurable and applicable indicators for the Infectious Health Care Waste (IHCW) Treatment sector.DOI: http://dx.doi.org/10.5755/j01.erem.73.2.13399

International audience; The control of malolactic fermentation (MLF) by Oenococcus oeni is an essential step in winemaking process. Although selected O. œni strains are available for winemakers, the MLF is not always successful, sometimes because of indigenous presence of other strains. In this work, interaction during MLF between five strains of O. œni was studied. Experiments were performed in MRS medium modified to be closer to wine conditions (pH 3.5, 10% ethanol). Interaction in mixed cultures of 10 pairs formed by the five strains were analysed from experiments performed in a Membrane Bioreactor (MBR). Pairs were classified in three different classes among growth interaction: 1) negative reciprocal interaction of both strains (6 pairs), 2) interaction that affect negatively one strain and positively the other (3 pairs), and 3) interaction with positive effect on one strain and no effect on the other (1 pair). Thanks to a mathematical model previously established during pure cultures to link growth and malic acid consumption, effect of mixed cultures on the specific activity of cells to consume malic acid has been equally evaluated. This capacity seemed not to be affected for 4 pairs whereas it seemed activated for 6 pairs.

A model to predict accurately pH evolution during alcoholic fermentation of must by Saccharomyces cerevisiae is proposed for the first time. The objective at least is to determine if the pH measurement could be used for predictive control. The inputs of the model are: the temperature, the concentrations in sugars, ethanol, nitrogen compounds, mineral elements (magnesium, calcium, potassium and sodium) and main organic acids (malic acid, citric acid, acetic acid, lactic acid, succinic acid). In order to avoid uncertainties coming from the possible precipitation, we studied this opportunity on a grape must without any tartaric acid, known as forming complexes with potassium and calcium during the fermentation. The model is based on thermodynamic equilibrium of electrolytic compounds in solution. The dissociation constants depend on the temperature and the alcoholic degree of the solution. The average activity coefficients are estimated by the Debbye–Huckel relation. A fictive diacid is introduced in the model to represent the unmeasured residual species. The molality of hydrogen ions and thus the pH are determined by solving a non-linear algebraic equations system consisted of mass balances, chemical equilibrium equations and electroneutrality principle. Simulation results showed a good capacity of the model to represent the pH evolution during fermentation.

International audience; The aeration is a key factor for Bacillus thuringiensis growth, sporulation and δ-endotoxins production. The objective of our work was to study the effect of aeration on the fermentation kinetics of Bacillus thuringiensis kurstaki (Btk), cultivated in a cereal milling byproduct (CMB) mono-component medium, in order to improve the δ-endotoxins productivity. Aeration conditions were systematically characterized by the volumetric mass transfer coefficient KLa. In the 6% CMB culture medium, different values of the maximal specific oxygen uptake rate were obtained at different values of KLa. For KLa of 7.2 h−1, the growth was inhibited and the sporulation was defective. There was a linear increase of the average specific growth rate and faster sporulation and liberation of spores and δ-endotoxins crystals when KLa was increased between 13.3 h−1 and 65.5 h−1. Similar kinetic was observed in cultures performed at KLa equal to 65.5 h−1 and 106.2 h−1. The highest toxins productivity of 96.1 mg L−1 h−1 was obtained in the 9% CMB culture medium for KLa of 102 h−1. It was possible to track the evolution of the bacterial cells between vegetative growth, sporulation and liberation of mature spores by following the variation of the CO2 percent in the effluent gas.

International audience; The objective of this study is to analyze Infectious Health Care Waste generation rates and patterns in Lebanon. Therefore, the quantities generated during five years by 57 hospitals from a total of 163 in the country have been analyzed. The seasonal evolution of Infectious Health Care Waste production and the evolution of the evaluation of the trends over years have been studied. Besides, the generation per capita have been estimated and compared to other countries. The variance between categories and the correlation between number of beds and Infectious Health Care Waste generation have been analyzed. The obtained results showed that the large private hospitals (over 200 beds) are characterized by their high generation rate: an average of 2.45 kg per occupied bed^-1 day^-1, whereas the average generation rate for other categories is 0.94 kg per occupied bed^-1 day^-1. The weighted mean is 1.14 per occupied kg bed^-1 day^-1. Small public hospitals (i.e. less than 100 beds) have the smallest standard deviation: 0.13, whereas large private hospitals (i.e. over than 200 beds) have the highest standard deviation: 0.40. Infectious Health Care Waste generation has been estimated to 1.42 kg/capita/year. The correlation between the numbers of hospitals beds in hospitals and the generation rate per bed is weak. The correlation between Infectious Health Care Waste generation per day and beds number is stronger. The total quantity produced by hospitals has increased over the five past years. These results suggest that the quantities of medical waste are not well controlled, and that hospitals have a defective monitoring management system of their waste. Annual peaks are observed in June, July, and December. Thus, this study, for the first time in Lebanon, has provided information on the infectious waste generation, allowing benchmarking between hospitals and between countries

International audience; Many studies show that the treatment of Infectious Health Care Waste (IHCW) in steam sterilization devices at usual operating standards does not allow for proper treatment of Infectious Health Care Waste (IHCW). Including a grinding component before sterilization allows better waste sterilization, but any hard metal object in the waste can damage the shredder. The first objective of the study is to verify that efficient IHCW treatment can occur at standard operating parameters defined by the contact time–temperature couple in steam treatment systems without a pre-mixing/fragmenting or pre-shredding step. The second objective is to establish scientifically whether the standard operation conditions for a steam treatment system including a step of pre-mixing/fragmenting were sufficient to destroy the bacterial spores in IHCW known to be the most difficult to treat. Results show that for efficient sterilization of dialysis cartridges in a pilot 60L steam treatment system, the process would require more than 20 min at 144 °C without a pre-mixing/fragmenting step. In a 720L steam treatment system including pre-mixing/fragmenting paddles, only 10 min at 144 °C are required to sterilize IHCW proved to be sterilization challenges such as dialysis cartridges and diapers in normal conditions of rolling.

International audience; Opti’Tom aims to develop and confirm, at pilot and industrial scale, stoichio-kinetic models describing changes in micronutrients contents in tomato-based products during processing. Two kinds of processes were studied such as production of tomato paste from fresh tomatoes and sauces from tomato paste. Several pilot trials were conducted and the data (amounts of microconstituents, schedules of the processes) were exploited to develop a software in order to optimize the current manufacturing processes.

International audience; To investigate the action mechanisms of a specific fungal origin chitosan preparation on Brettanomyces bruxellensis. METHODS AND RESULTS: Different approaches in a wine-model synthetic medium were carried out: optical and electronic microscopy, flow cytometry, ATP flow measurements and zeta potential characterization. The inactivation effect was confirmed. Moreover, fungal origin chitosan induced both physical and biological effects on B. bruxellensis cells. Physical effect led to aggregation of cells with chitosan likely due to charge interactions. At the same time, a biological effect induced a leakage of ATP and thus a viability loss of B. bruxellensis cells. CONCLUSIONS: The antimicrobial action mode of chitosan against B. bruxellensis is not a simple mechanism but the result of several mechanisms acting together. SIGNIFICANCE AND IMPACT OF THE STUDY: Brettanomyces bruxellensis, a yeast responsible for the production of undesirable aromatic compounds (volatile phenols), is a permanent threat to wine quality. Today, different means are implemented to fight against B. bruxellensis, but are not always sufficient. The chitosan of fungal origin is introduced as a new tool to control B. bruxellensis in winemaking and has poorly been studied before for this application.

International audience; Various consortia of yeasts and bacteria involved in the natural fermentation process of tequila have been identified, particularly non-Saccharomyces yeasts. This study evaluates the fermentative capacity of two non-Saccharomyces yeasts (isolated from traditional mezcal fermentation): Kluyveromyces marxianus (DU3) and Pichia kluyveri (GRO3), and assesses their production of volatile compounds. The values found are compared with those of the same attributes of a Saccharomyces cerevisiae (AR5) isolated from tequila fermentation. The fermentations were performed in two different media, agave juice (JA) and a semi-synthetic medium (M11). The study also compared free and immobilized yeast fermentations in the JA medium in order to evaluate the potential benefits of immobilization on the yeast behaviour. This study demonstrated the potential of non-Saccharomyces yeasts, which fermented the agave juice in the same manner as S. cerevisiae but with higher ester production. Furthermore, K. marxianus produced more higher alcohols than S. cerevisiae. This could lead to tequila with different aroma profiles. Results were different in the synthetic medium, thus showing sensitivity to the composition of the medium. No significant differences between yeast fermentations with free and immobilized cells were detected, except for ethanol yield.

Bacillus thuringiensis is a facultative anaerobe, gram positive, spore forming bacterium. The biotechnological importance of this bacterium resides in its ability to produce, during sporulation, crystal proteins known as delta-endotoxins which express specific insecticidal activity. At industrial scale, the culture media represents an important part of B. thuringiensis based biopesticides production cost. According to the literature, different agro-industrial residues and byproducts were used as sources of proteins in order to reduce the cost of B. thuringiensis culture medium, but carbohydrates (glucose, starch or molasses) and/or mineral sources were added. In this work, a cereal milling by-product (CMB) as a monocomponent medium was investigated and compared to synthetic mediums in terms of delta-endotoxin yield and productivity in submerged fermentation of different strains of B. thuringiensis. The CMB was shown efficient to be used as a complete substrate (source of proteins, carbohydrates and minerals) for B. thuringiensis production. The optimal CMB ratio in the culture medium was found to be 6% in shake flasks experiments. The consumption of the CMB sugars by the bacteria was analyzed. Production of the bio-insecticide in lab-bioreactor in controlled conditions was equally performed to give basic elements for extrapolation in industrial conditions.

International audience; Food companies want to improve the quality of their products guaranteeing complex organoleptic properties and high nutritional value. The development of such foods and the reassessment of existing products and processes require controlling the interaction between structure and chemical reactivity of the food in relation with applied treatments. The study and at last the control of these reactions are an important challenge of progress for food industry. The aim of this project is to build and provide, for companies in the sector of tomato-based products, a tool to optimize existing processes and predict the final nutritional quality and avoid many uncertain and expensive preindustrial trials.

Volatile phenols are aromatic compounds and one of the key molecules responsible for olfactory defects in wine. The yeast genus Brettanomyces is the only major microorganism that has the ability to covert hydroxycinnamic acids into important levels of these compounds, especially 4-ethylphenol and 4-ethylguaiacol, in red wine. When 4-ethylphenols reach concentrations greater than the sensory threshold, all wine’s organoleptic characteristics might be influenced or damaged. The aim of this literature review is to provide a better understanding of the physicochemical, biochemical, and metabolic factors that are related to the levels of p-coumaric acid and volatile phenols in wine. Then, this work summarizes the different methods used for controlling the presence of Brettanomyces in wine and the production of ethylphenols.

International audience; Alcoholic fermentation by an oenological strain of Torulaspora delbrueckii in association with an oenological strain of Saccharomyces cerevisiae was studied in mixed and sequential cultures. Experiments were performed in a synthetic grape must medium in a membrane bioreactor, a special tool designed to study indirect interactions between microorganisms. Results showed that the S. cerevisiae strain had a negative impact on the T. delbrueckii strain, leading to a viability decrease as soon as S. cerevisiae was inoculated. Even for high inoculation of T. delbrueckii (more than 20× S. cerevisiae) in mixed cultures, T. delbrueckii growth was inhibited. Substrate competition and cell-to-cell contact mechanism could be eliminated as explanations of the observed interaction, which was probably an inhibition by a metabolite produced by S. cerevisiae. S. cerevisiae should be inoculated 48 h after T. delbrueckii in order to ensure the growth of T. delbrueckii and consequently a decrease of volatile acidity and a higher isoamyl acetate production. In this case, in a medium with a high concentration of assimilable nitrogen (324 mg L−1), S. cerevisiae growth was not affected by T. delbrueckii. But in a sequential fermentation in a medium containing 176 mg L−1 initial assimilable nitrogen, S. cerevisiae was not able to develop because of nitrogen exhaustion by T. delbrueckii growth during the first 48 h, leading to sluggish fermentation.

International audience; A new bacterial species, Saccharothrix algeriensis NRRL B-24137, was isolated in 1992 in the Sahara desert. This filamentous bacterium is able to produce dithiolopyrrolones, molecules presenting antibacterial, antifungal, and anticancer properties. In this study, a “reaction engineering” approach was adopted to gain more knowledge on the growth of Sa. algeriensis and its dithiolopyrrolone production on a semi-synthetic liquid medium. The objective is to establish a reaction scheme of the bacterium metabolism from extracellular experimental information, relatively easy to obtain. The approach enabled us to show that Sa. algeriensis could grow using several substrates that were sequentially consumed and that substrate limitation may induce a secondary metabolism in antibiotic production. From these qualitative data, a general reaction scheme was extracted consisting of four reactions: growth via amino acids, glucose consumption for maintenance, growth using glucose, and thiolutin production. The stoichiometric coefficients and the reaction extends were identified using a factorial analysis based on the bilinear structure of the component mass balances in a batch reactor. The analysis of the reaction stoichiometry enabled us to draw some conclusions concerning the substrate consumption pathway.

p-Coumaric acid is a natural hydroxycinnamic acid existing in grapes and wine. It is the precursor of the 4-ethylphenol molecule through the bioconversion reaction by Brettanomyces yeast. Chromatographic methods are the most common techniques to detect p-coumaric acid. It is known that this acid is highly unstable in analysis and fermentation experiments. This paper highlights the problems occurring in p-coumaric acid analysis in wine fermentation conditions when studying its bioconversion. First, it was shown that p-coumaric acid was unstable at elevated temperature. On the other hand, it was found that in our experimental conditions p-coumaric acid reacted with ethanol. This work revealed also that the p-coumaric acid is partially adsorbed on Brettanomyces yeast, certainly on cell walls. Because of these phenomena the quantity of p-coumaric acid which can participate to the bioconversion into ethylphenol decreases.

The effect of temperatures ranging from 15 to 35 °C on a culture of Brettanomyces bruxellensis was investigated in regards to thermodynamics, metabolism, and kinetics. In this temperature range, we observed an increase in growth and production rates. The growth behavior was well represented using the Arrhenius model, and an apparent activation energy of 16.61 kcal/mol was estimated. A stuck fermentation was observed at 35 °C as represented by high cell death. The carbon balance established that temperature had no effect on repartition of the glucose consumption between biomass and products. Hence, the same biomass concentration was obtained for all temperatures, except at 35 °C. Moreover, using logistic and Luedeking–Piret models, we demonstrated that production rates of ethanol and acetic acid were partially growth associated. Parameters associated with growth (αethand αaa) remained constant with changing temperature, whereas, parameters associated with the population (βethand βaa) varied. Optimal values were obtained at 32 °C for ethanol and at 25 °C for acetic acid.

Development of bacterial resistance to antibiotics has lead to investigations of rare bacteria, which produce new bioactive molecules. Saccharothrix algriensis has been isolated from the desert Maghreb. It produces dithiolopyrrolones, some of which were newly identified. In order to optimize and control production of dithiolopyrrolones, investigation regarding microorganism metabolism was required. Growth on semisynthetic medium containing 2 g· l −1 of yeast extract was complicated because it was performed on several substrates. Moreover, because development of this bacterium on minimum medium was difficult, its composition was optimized by screening of different compounds led by yeast extract. Uracil added to the minimum medium allowed a maximum biomass production of 1.35 g· l −1 compared to 0.32 g· l −1 without uracil. Moreover, nonpolar amino acids and trace metal elements stimulated Saccharothrix algeriensis growth.

This paper presents a kinetic model for the enzymatic degradation of the starch during mashing for beer production. Based on a new set of experiments, an original reaction scheme for the hydrolysis of starch by α- and β-amylases has been proposed. Here, the kinetics of the reactions involved in this scheme are described: starch gelatinisation, amylase activities and carbohydrate production. One originality of this model is the mathematical representation of the amylase activities temperature dependency. The model requires to know the initial composition of malt (starch concentration and amylase potential which are classically measured to qualify the raw material) and the operating conditions (temperature chart) to predict the evolutions of amylase activities, dextrins and fermentable carbohydrate concentrations during mashing. The model parameters have been estimated by fitting nine experiments performed on one malt variety. Five other experiments validate the model for different malt varieties.

International audience; This work aimed to investigate the effect of some nutriments (tiglic acid and methacrylic acid) on the growth of Saccharothrix algeriensis DSM 44581 on chemically defined medium (semi-synthetic medium) by using controlled batch fermenters. The controlled batch fermentations were conducted in the presence of tiglic and methacrylic acids. The growth rate of S. algeriensis in all fermentations was fast during the first 10 h of fermentation. The control culture showed a partially cell lysis in comparison to cultures with organic acids. This result showing that these organic acids could be used for biomass maintaining. The formation of biomass was influenced by the addition of organic acids. The experiment in the fermentor showed some differences with results obtained in Erlenmeyers.; Ce travail s’est donné pour objectif l’étude cinétique de l’effet de certains nutriments (acide tiglique et acide méthacrylique) sur la croissance de Saccharothrix algeriensis DSM 44581 en fermenteur batch dans un milieu semi-synthétique.Des fermentations contrôlées dans des fermenteurs en batch ont été effectuées en présence de l’acide tiglique et de l’acide méthacrylique, prisun à un, pour affiner les résultats obtenus en Erlenmeyers. D'après les résultats obtenus, la croissance de S. algeriensis dans les deuxfermentations est très rapide pendant les premières heures de culture. Les cellules de la culture témoin subissent une lyse cellulaire assez marquée alors que les cellules en présence des acides organiques se maintiennent bien. Les acides organiques en tant que source de carbone permettent la conservation de l’intégrité des cellules. La formation de la biomasse est soumise à la régulation par les deux acides organiques ajoutés. Les résultats obtenus en fermenteurs ne sont pas exactement les même que ceux obtenus en Erlenmeyers d’un point de vue qualitatif et quantitatif.

International audience; Healthcare waste mismanagement constitutes a serious environmental and sanitary problem, especially in developing countries. This article describes the strategy and the methodology of the implementation of a national network for healthcare waste management by a non-profit organisation in Lebanon, taking into consideration environmental, social and economic issues. It presents a holistic description of the main aspects of this crucial sustainable development topic: the elaboration of the strategy and the selection of the optimal treatment technique based on an analysis of the context; the training on waste minimisation and waste management issues inside hospitals; the waste transportation and treatment procedures; the quality management of the process; the evaluation and the monitoring of the produced quantities and the established system; the optimisation of sterilisation parameters and process in order to reduce sterilisation time and fuel consumption.