0000000000049492
AUTHOR
A. Durand
The arid–humid transition in the Sahara and the Sahel during the last deglaciation
At the time of the Last Glacial Maximum, the Sahara and Sahel regions of North Africa were extremely dry. New records of rainfall show that during the subsequent deglaciation, the transition from arid to humid conditions in these regions occurred synchronously in two main steps. Comparison with other records of palaeoclimate in Europe and the North Atlantic Ocean shows that certain common factors controlled changes in ocean and atmosphere dynamics during the deglaciation.
Cloning and expression of genes involved in conidiation and surface properties of Penicillium camemberti grown in liquid and solid cultures.
International audience; Based on bioinformatic data on model fungi, the rodA and wetA genes encoding, respectively, a RodA hydrophobin protein and the WetA protein involved in conidiation mechanisms, were PCR-cloned and characterized for the first time in Penicillium camemberti. These results, completed by a sequence of the brlA gene (available in GenBank), which encodes a major transcriptional regulator also involved in the conidiation mechanism, were used to compare, by qRT-PCR, the expression of the three genes in liquid and solid cultures in a synthetic medium. While expression of the brlA and wetA genes increased dramatically in both culture conditions after 4 days of growth, expressio…
Production d'arôme de noix de coco (pentyl-6-alpha-pyrone) par le champignon filamenteux Trichoderma
National audience
Influence of cell immobilization on the production of benzaldehyde and benzyl alcohol by the white-rot fungi Bjerkandera adusta, Ischnoderma benzoinum and Dichomitus squalens
International audience; Three white-rot basidiomycetes, Bjerkandera adusta, Ischnoderma benzoinum and Dichomitus squalens, were cultivated on a liquid medium supplemented with l-phenylalanine, a precursor for benzaldehyde (bitter almond aroma) and benzyl alcohol. Remarkable amounts of benzaldehyde (587 mg l−1) were found in cultures of B. adusta. Immobilization of this fungus on polyurethane foam cubes allowed an 8.3-fold increase of the production of benzaldehyde and a 15-fold increase of the productivity as compared with non-immobilized cells. Aryl-alcohol oxidase activity was only detected in B. adusta. This activity was also significantly enhanced in immobilized cells, suggesting that i…
Study on the solid-state production of a thermostable alpha-L-arabinofuranosidase of Thermoascus aurantiacus on sugar beet pulp
International audience
INRA-Dijon reactors for solid state fermentation: Designs and applications
45 ref.; International audience
Variabilité basse-fréquence des précipitations au Sahel et des températures de surface de l'océan Atlantique au cours du dernier siècle.
6 pages; International audience; Cette étude examine les téléconnexions entre les températures de surface de la mer (TSM) de l'océan Atlantique et la distribution zonale des précipitations au Sahel au cours du dernier siècle. Depuis la fin des années 60, les précipitations d'Afrique de l'Ouest présentent une tendance négative sur l'ensemble de la bande sahélienne. Pourtant, trois types de variabilité basse-fréquence des précipitations sahélienne sont observés : la côte atlantique (Dakar), le Sahel central (Nioro du Sahel et Mopti) et le Sahel oriental (Niamey, Maradi, Maïné-Soroa). Au cours du XXème siècle, les précipitations sont rarement reliées simultanément avec les TSM de l'Atlantique …
Breaks in the continental environmental equilibrium and intensity changes in aridity over the past 20 000 years in the Central Sahel
Abstract The record of arid climatic events in continental sedimentation is subject to the intensity of the climatic mechanism which generated them and to the nature of the environment which recorded them. In them Sahel, where the environmental equilibrium is particularly precarious, all types of arid climatic events are likely to be recorded. But the consequences of events of small global intensity (exceptional climatic events and local climatic anomalies) merge with the effects of the ⪡average climate⪢. On the other hand, climatic events on a global scale (climatic crises and climatostratigraphic events) are clearly pointed out, due to the large breaks in environmental equilibrium that th…
Une structure de transfert recherche-industrie : La plate-forme de predeveloppement en biotechnologie
National audience
Production d'arôme de noix de coco (pentyl-6-alpha pyrone) par le champignon filamenteux trichoderma
National audience
Chromosomes and the origins of apes and australopithecins
Comparison of molecular data suggests that the higher apes (Gorilla, Pan) and humankind (Homo) are closely related and that they diverged from the common ancestor through two speciation events situated very closely together in time. Examination of the chromosomal formulas of the living species reveals a paradox in the distribution of mutated chromosomes which can only be resolved by a model of trichotomic diversification. This new model of divergence from the common ancestor is characterized by the transition from (1) a monotypic phase to (2) a polytypic phase of three sub-species — pre-gorilla, pre-chimpanzee and preaustralopithecine. The quadruped ancestors ofAustralopithecus appear to ha…
A detailed record of recent climatic changes in a laminated lake record in the Sahel
International audience
Were climatic changes a driving force in hominid evolution?
International audience; A comparison of externalist and internalist approaches in hominid evolution shows that the externalist approach, with its claim that climate was responsible for the appearance of bipedalism and hominization, now seems to be ruled out by the biological, palaeogeographical, palaeontological and palaeoclimatic data on which it was based. Biological data support the embryonic origin of cranio-facial contraction, which determined the increase in cranial capacity and the shift in the position of the foramen magnum implying bipedalism. In the internalist approach, developmental biology appears as the driving force of hominid evolution, although climate exerts a significant …
Conversion of oleic acid to 10-hydroxystearic acid by Nocardia paraffinae
International audience
Development of a rapid and highly sensitive biochemical method for the measurement of fungal spore viability. An alternative to the CFU method
Abstract 1 A biochemical method, based on dehydrogenase activity (DHA) measurement, has been developed as an alternative to colony forming unit (CFU) enumeration, for assessing the viability of fungal spores. In viable cells, a tetrazolium salt (MTT) is reduced to a coloured formazan (MTTf) by cellular dehydrogenase enzymes. From the colorimetric assay developed by Mosmann for mammalian cells, the procedure has been adapted and optimised using P. digitatum spores as a model. Propan-2-ol has been selected as the best solvent to extract the MTTf from the spores. The sensitivity of the method has been considerably increased by determining the optimal conditions of incubation for the MTT reduct…
Substrate use and production of alpha-L-arabinofuranosidase during solid-state culture of Trichoderma reesei on sugar beet pulp
International audience
Production of gamma-decalactone in the genus Sporidiobolus
International audience
The biotechnology of flavours
International audience
Solid state fermentations: an attractive to submerged-liquid fermentations
International audience
Production of gamma-decalactone and 4-hydroxy-decanoic acid in the genus Sporidiobolus
International audience
Laboratory scale reacteur for aseptic solid state cultivation
International audience
Prospects for the microbial production of food flavours
The microbial production of natural flavours has been extensively studied during the past decade, and some processes are currently being exploited commercially. However, in the case of flavour compounds such as lactones and some aromatic compounds, the lack of basic information on their metabolism, as well as their high toxicity, are two main barriers to industrial production. The development of novel and cheap production processes, such as solid-state fermentation, may help overcome some of the current limitations of microbial flavour production, as well as widening the spectrum of biotechnologically accessible compounds.
Use of solid state fermentation to produce Beauveria bassiana for the biological control of european corn borer
The production process of a new bioinsecticide against european corn borer is described. The entomopathogenic fungus, Beauveria bassiana, is cultivated by Solid State Fermentation (SSF). The culture support chosen, clay microgranules, humidified with optimal nutritive solution, is incubated in optimal conditions during 48 hours, then dried for 5 days. The bioinsecticide can be directly used after harvesting, without formulation. This process is original for several reasons : - The granulometry (500 microm) and the bulk density (0.6) of the microgranules are compatible with the mechanical standard application of pesticides on corn. - The bioinsecticide could be produced in a pilot reactor of…
General principles of reactor design and operation for SSC
International audience
Kinetics of Thermoascus aurantiacus solid-state fermentation on sugar-beet pulp-polysaccharide alteration and production of related enzymatic activities
International audience; The fungal solubilization of cell wall components of sugar-beet pulp, during solid-state fermentation of Thermoascus aurantiacus, is reported here. The extracellular fungal enzyme activities related to the substrate degradation were also studied. In 120 h, more than 60% of the main sugar-beet pulp polysaccharides, i.e. pectins, arabinose- and glucose-containing polysaccharides, were rapidly brought into solution by the fungus. The slow accumulation of monosaccharides compared to the fast degradation of the polysaccharides suggested that most of the released sugars were consumed by the fungus. The analysis of the enzymes present in the water extracts of the solid-stat…
Glucosamine measurement as indirect method for biomass estimation of Cunninghamella elegans grown in solide state cultivation conditions
Glucosamine measurement has been tested as the indirect method to estimate the biomass produced by Cunninghamella elegans during solid state cultivation (SSC). The independence of this cell constituent content from the age and the conditions of the culture have been verified. The influence of the medium composition, in particular the nature of the carbon source on glucosamine amount is presented. Glucosamine can be considered as a well-adapted biomass indicator, with the necessity to establish for each medium tested a prior correlation between biomass and glucosamine amount. This correlation should be defined in submerged conditions before applying the biomass estimating method in SSC.
Production of 6-pentyl-alpha-pyrone by Trichoderma sp. from vegetable oils
International audience
The use lipase to overcome the toxicity of gamma-decalactone during its batch production with the yeast Sporidiobolus salmonicolor
International audience