Études physiologiques et cinétiques de "geotrichum candidum" et "Penicillium camembertii" cultivés en bioréacteur sur milieux synthétiques

Des cultures des deux microflores d'affinage G. candidum et P. camembertii ont été menées en bioréacteur. Ce travail a montré que, contrairement à P. camembertii, en présence de substrats aisément assimilables en tant que sources de carbone, par exemple des peptones ou du glutamate, le lactate n'est pas consommé par G. candidum durant sa croissance. La culture mixte sur jus de camembert a mis en évidence des effets de synergie entre les deux microorganismes; les activités enzymatiques de G. candidum ont facilité l'assimilation de peptides et d'acides aminés comme sources de carbone par P. camembertii. Il y a de plus compétition entre les deux espèces pour les peptides et acides aminés les plus aisément métabolisables, qui sont ainsi utilisés comme sources d'énergie, en plus d'être sources de carbone et d'azote; les autres sources de carbone disponibles n'ont été utilisées que pour le maintien cellulaire. Cette compétition a été confirmée sur milieux synthétiques simples.RENNES1-BU Sciences Philo (352382102) / SudocSudocFranceF

Energy Balance Of Third Generation Bioethanol

Global greenhouse gas emissions are constantly increasing, despite the partial replacement of fossil fuels by renewable energies. The transport sector is responsible for almost 24% of direct CO2 emissions from the combustion of fossil fuels, generating greenhouse gas emissions, highlighting the need for a greater focus of international policies to encourage the production and the use of biofuels. Bioethanol is the most consumed biofuel in the world; it is produced by fermentation from materials rich in sugar (glucose, starch, cellulose). However, the controversy around the use of first and second generation have forced the transition to the third generation based on marine and freshwater algae; the latter have the advantage of being abundant, even invasive, easy to cultivate with good energy potential. This study proposes a life cycle analysis (LCA) of bioethanol production from the macro algae Ulva Lactuca, it was carried out after the introduction of several data into the SimPro8.1 software (e.g. quantity of water, consumed electricity, used chemicals) using the Impact 2002+ methodology. The results show a positive energy balance reflecting high-energy efficiency since the system produces about 1.44 times the energy consumed

CELLULOSIC BIOETHANOL PRODUCTION FROM ULVA LACTUCA MACROALGAE

International audienceNowadays, the use of biofuels has become an unavoidable solution to the depletion of fossil fuels and global warming. The controversy over the use of food crops for the production of the first-generation biofuels and deforestation caused by the second-generation ones has forced the transition to the third generation of biofuels, which avoids the use of arable land and edible products, and does not threaten biodiversity. This generation is based on the marine and freshwater biomass, which has the advantages of being abundant or even invasive, easy to cultivate and having a good energetic potential. Bioethanol production from Ulva lactuca, a local marine macroalgae collected from the west coast of Algiers, was examined in this study. Ulva lactuca showed a good energetic potential due to its carbohydrate-rich content: 9.57% of cellulose, 6.9% of hemicellulose and low lignin content of 5.11%. Ethanol was produced following the separate hydrolysis and fermentation process (SHF), preceded by a thermal acid pretreatment at 120 degrees C during 15 min. Enzymatic hydrolysis was performed using a commercial cellulase (Celluclast 1.5 L), which saccharified the cellulose contained in the green seaweed, releasing about 85.01% of the total glucose, corresponding to 7.21 g/L after 96 h of enzymatic hydrolysis at pH 5 and 45 degrees C. About 3.52 g/L of ethanol was produced after 48 h of fermentation using Saccharomyces cerevisiae at 30 degrees C and pH 5, leading to a high ethanol yield of 0.41 g of ethanol/g of glucose

Bioethanol production from deproteinized cheese whey powder by local strain isolated from soured milk: influence of operating parameters

International audienceIn this paper, a local isolated yeast strain was studied for bioethanol production using protein-free cheese whey powder (CWP) in batch alcoholic fermentation experiments. Ethanol tolerance tests were performed with different ethanol concentrations (from 0% to 20%). The maximum ethanol tolerance obtained for our strain was 5% (v/v). The influence of initial lactose concentration, temperature and pH on fermentation kinetic was studied. For initial lactose concentration ranging from 57.5 to 260 gL−1, the highest ethanol production 34.8 gL−1 was obtained at 109 gL−1 initial lactose concentration corresponding to 0.413 gg−1 ethanol yield (YP/S); (While it was noticed less ethanol production, namely 0.178 g g−1) at a higher initial whey sugar concentration of 260 gL−1. The effect of the initial pH on the fermentation was studied at three different values: 3, 4 and 5. The ethanol production reached a maximum of 22 g L−1 with a lactose consumption of 77.62% at pH 4. However, an observed decrease occurred in ethanol production and lactose consumption at pH 3, with values of 10.34 gL-1 and 24.46%, respectively. For the fermentation conducted at the three temperatures of 37°C, 40°C and 43°C, the maximum ethanol production and lactose consumption were 34.82 gL-1 and 80.75%, respectively, achieved at 37°C. The experimental data was analyzed using the Gompertz model to obtain the following kinetic parameters: the maximum ethanol concentration (Pm) was found to be 36.97 gL-1, the maximum ethanol production rate (rp,m) was 0.402 gL−1h−1 and the lag phase (tl) was 10.8 h. The comparison of the isolated Kluyveromyces marxianus TXID4911 strain with the reference strain Kluyveromyces marxianus DSM 5421, showed a relatively close ethanol yield (YP/S) 0.415 and 0.505 gg,−1 respectively