Analysis of Environmental Conditions Affecting Acids Production in Lactic Acid Bacteria Involved in Ivorian Cocoa Fermentation

International audienceOriginal Research Article Acetic and lactic acids produced during cocoa fermentation impact strongly the quality of fermented cocoa beans and chocolate. In this study, acid production from various carbon source and environmental conditions was analyzed in five lactic acid bacteria previously characterized as citrate lyase producers. It appears that production of acetic and lactic acids by these strains is strongly dependent on environmental conditions such as pH and temperature. Indeed, maximum yield of acids occurred at 30°C and pH 4 in Lactobacillus plantarum strain T11G3 and Lactobacillus casei strain T10G5. On the other hand acid production was maximum at 40°C and pH 4 in Lactobacillus plantarum strains T8N10, T10AG26 and at 40°C and pH 4.5 in Leuconostoc mesenteroides strain T8AB6. These strains also presented variable acid production regarding the sugar tested with sucrose allowing the highest acid yield (38.12 mg/mL) comparatively to that obtained from glucose (23.91 mg/mL) and fructose (26.28 mg/mL). Moreover, maximum acid production in all the strains was rapidly achieved, after 36-48h fermentation with sucrose, whereas a delayed production (around 72 h) was observed with glucose or fructose. Alcoholic conditions were found to particularly enhance acid production in the strains studied (Leuconostoc mesenteroides strain T8AB6). The maximum yield of acetic and lactic acids was 12.7 mg/mL and 14.4 mg/mL respectively in Leuconostoc mesenteroides strain T8AB6 and Lactobacillus plantarum strain T8N10 under citric acid condition. Overall, this study highlights that carbon source and environnemental condition impact on the production of acidic compounds by LAB from fermenting cocoa. Furthermore, variability in acid production was observed between the studied strains in most of the considered conditions. Thus, the different LAB strains studied probably behave as complementary consortium to continuously achieve the process of natural cocoa fermentation

Sulfur Assimilation and the Role of Sulfur in Plant Metabolism: A Survey

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Plant serine acetyltransferase: new insights for regulation of sulphur metabolism in plant cells

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Petrography and geochemistry of Plio-Quaternary Calc-Alkaline volcanoes of Southwestern Colombia

The six studied southwestern Colombian Plio-Quaternary volcanoes (Puracé, Doña Juana, Galeras, Azufral, Cumbal and Chiles) are located in the central part of the Northern Volcanic Zone (NVZ) of the Andes. The lavas are predominantly andesites and dacites, with lesser amount of basalt, and range 52% to 70% SiO₂. The two-pyroxenes basic and acid andesites exhibit plagioclase phenocrysts with core composition of An50–80 and An40–70 respectively. Hornblende and biotite occur in dacites in association with plagioclase cores ranging An30–50. The lavas belong to medium- to high-potassic calc-alkaline series, typical of active continental margins. Two types of lavas can be distinguished in the studied area: 1) Northeastern-type lavas which show high TiO₂, K-group elements, LREE, and Ce/Yb ratio, low HREE content and a low Ba/La ratio 2) Southwestern-type lavas are characterized by low TiO₂, K-group elements, LREE, low Ce/Yb, an enrichment in HREE content and high Ba/La ratio. The northward increase in incompatible elements is attributed to a higher contribution of the siliceous Pre-Mesozoic crust in the north of the studied area. The younger (Post-Cretaceous) oceanic basement underlying the southwestern volcanoes cannot be responsible for an enrichment in incompatible elements only by contamination processes. Geochemical evidences suggest that the NVZ calc-alkaline lavas were derived from a primitive mantle which was enriched in Ba and partially in other K-group elements by dehydration and/or partial melting of the oceanic slab within the asthenosphere. This primitive melt, induced in response of the hydration processes within the mantle, suffered various stages of assimilation and fractional crystallization at lower to intermediate crustal levels, as revealed by the regional depletion in HREE of the northeastern-type lavas. At an upper crustal level, within the magma chamber, magma mixing between “primitive” up-rising basalt melt and andesitic-dacitic differentiated magma accompanied by fractional crystallization and crustal assimilation processes produced the andesitic series of each volcanoes.Los volcanes plio-cuaternarios del sudoeste colombiano están localizados en el centro de la Zona Volcánica Norte (NVZ) de los Andes. Las lavas son generalmente andesíticas o dacíticas, con basaltos subordinados, variando el contenido en SiO₂ entre 53% y 70%. Las andesitas básicas o ácidas con dos piroxenos contienen fenocristales de plagioclasa con núcleos de composition An50–80 y An40–70 respectivamente. En las dacitas la hornblenda y la biotita aparecen asociadas con plagioclasas de composición An30–50 (núcleos). Las lavas pertenecen a la serie calcoalcalina potásica, típicas de márgenes continentales activos. Se pueden distinguir dos tipos de lavas: 1) lavas tipo Noreste, que se caracterizan por su alto contenido en TiO₂, elementos del grupo del potasio y tierras raras livianas, una alta relacion Ce/Yb, un empobrecimiento en tierras raras pesadas, y una baja relación Ba/La ; y 2) lavas tipo Suroeste, carcterizadas por bajo contenidos en TiO₂, en elementos del grupo del potasio, en tierras raras livianas, baja relación Ce/Yb, y un enriquecimiento en tierras raras pesadas y una alta relación Ba/La. El enriquecimiento en elementos incompatibles hacia el norte puede ser atribuído a una mayor contributión de la corteza silícea pre-mesozoica. El basamento oceánico más joven, que se encuentra bajo los volcanes del sudoeste, no puede ser responsable del enriquecimiento en elemnetos incompatibles por contaminación cortical. Evidencias petrográficas y geoquímicas sugieren que la génesis de las lavas puede ser atribuida a la fusion parcial de un fragmento de la corteza oceánica en la astenosfera, lo que condujo a un enriquecimiento del magma en Ba, y probablemente en otros elementos del grupo del potasio. El magma, así producido, evolucionó en distintas etapas de asimilación y cristalización fraccionada a distintas profundidades de la corteza. En la cámara magmática, de los niveles superiores de la corteza, la mezcla de un magma basáltico primitivo ascendente, con la de un magma andesítico-dacítico, conjutamente con los procesos de cristalización fraccionada y de contaminación cortical, producen la serie andesítica típica de cada volcán

Petrographic and geochemical studies of the southwestern colombian volcanoes

Les volcans actifs plio-quaternaires du sud-ouest de la Colombie sont situés dans la Zone Volcanique Nord (NVZ) des Andes. Ils appartiennent tous à la série calcoalcaline moyennement potassique typique des marges continentales actives. Les laves sont principalement des andésites et des dacites avec des teneurs en silice variant de 53% à 70%. Les analyses pétrographiques et géochimiques montrent que les phénomènes de cristallisation fractionnée, de mélange de magma et de contamination crustale sont impliqués à divers degrés dans la genèse des laves des volcans colombiens

Synthesis of the sulfur amino acids: cysteine and methionine

International audienceThis review will assess new features reported for the molecular and biochemical aspects of cysteine and methionine biosynthesis in Arabidopsis thaliana with regards to early published data from other taxa including crop plants and bacteria (Escherichia coli as a model). By contrast to bacteria and fungi, plant cells present a complex organization, in which the sulfur network takes place in multiple sites. Particularly, the impact of sulfur amino-acid biosynthesis compartmentalization will be addressed in respect to localization of sulfur reduction. To this end, the review will focus on regulation of sulfate reduction by synthesis of cysteine through the cysteine synthase complex and the synthesis of methionine and its derivatives. Finally, regulatory aspects of sulfur amino-acid biosynthesis will be explored with regards to interlacing processes such as photosynthesis, carbon and nitrogen assimilation

Sulfur Assimilation in Developing Lupin Cotyledons Could Contribute Significantly to the Accumulation of Organic Sulfur Reserves in the Seed

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Methionine Biosynthesis in Higher-Plants .1. Purification and Characterization of Cystathionine γ-Synthase from Spinach Chloroplasts

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