A model for pH determination during alcoholic fermentation of a grape must by Saccharomyces cerevisiae

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–H¨uckel 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

A stoichiometric reaction scheme for Saccharothrix algeriensis growth and thiolutin production

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

Highlight on the problems generated by p-coumaric acid analysis in fermentations

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

Health Care Waste generation rates and patterns: The case of Lebanon

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 countrie

Analysis of the effectiveness of a cereal milling by product monocomponent medium for the low cost production of Bacillus thuringiensis

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

Effect of temperature on Brettanomyces bruxellensis: metabolic and kinetic aspects

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 (αeth and αaa) remained constant with changing temperature, whereas, parameters associated with the population (βeth and βaa) varied. Optimal values were obtained at 32 °C for ethanol and at 25 °C for acetic acid

Influence de l'étape de croissance et de la quantité de brettanomyces bruxellensis sur la production d'éthyl-phenols

Influence de l'étape de croissance et de la quantité de brettanomyces bruxellensis sur la production d'éthyl-phenol

Indicators of Sustainable Development for Health Care Waste Treatment Industry

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

Evaluation of a cereal milling by-product for the low cost production of Bacillus thuringiensis kurstaki in submerged fermentation

With the idea of finding a cheap medium for the mass production of Bacillus thuringiensis (Bt), a cereal milling by product (CMB) was evaluated and was shown efficient to be used as a source of carbohydrates, proteins and minerals for the production of δ-endotoxins in submerged fermentation of a new strain of Bacillus thuringiensis kurstaki “Lip”. The results obtained in 1000 mL shake flasks experiments showed that the toxin proteins concentration produced in the 6% (w/v) CMB medium was 2.4 fold and 1.54 fold greater than the values reached in the Anderson medium and in a standard semi synthetic medium respectively, while there was no significant difference between the cell, spore and crystal counts or between the protein profiles of the “Lip” spore/crystal complex obtained in the three mediums. Considering all three factors, relative yield, productivity and cost, the use of the CMB mono-component medium was proved much more economical for an industrial production of “Lip” than the references mediums. Moreover, the suitability of the medium for large scale production of Bt based bio insecticide was evidenced in a 5 L lab bioreactor

Mixed cultures of Oenococcus oeni strains: A mathematical model to test interaction on malolactic fermentation in winemaking

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