Suivi et caractérisation du colmatage par les matières organiques des membranes de microfiltration et d'ultrafiltration (application à la production d'eau potable)

Cette étude traite du colmatage des membranes basse pression par les matières organiques des eaux naturelles. Le premier objectif a été d'évaluer la capacité d'unités pilotes à apprécier le potentiel colmatant. Ces unités sont alimentées par de l'eau renouvelée quotidiennement ce qui permet de se rapprocher des conditions d'exploitation sur usine. Les profils de perte de flux enregistrés sur plusieurs campagnes d'essais sur site ont permis de valider l'intérêt de notre outil expérimental. Le second objectif portait sur la caractérisation du colmatage de nature organique. Une grande diversité de techniques analytiques a été développée. Quel que soit la membrane, le matériel colmatant englobe des substances humiques, des substances protéiques, des sucres aminés (parois microbiennes) et des polysaccharides. Les résidus microbiens composantes ubiquistes des eaux de surface et structures résultant d'un possible développement bactérien à la surface des membranes semblent constituer la source prépondérante du matériel colmatant.This project relates to NOM fouling of low pressure membranes. The first objective was to test the capacity of small pilot units to evaluate the fouling properties of natural and treated waters. Pilot testing was conducted on site (drinking water treatment plants). Flux decline recorded during several campaigns with different water qualities confirmed the efficacy of our pilot units to identify fouling problems based on a short time experiment. The second objective was to characterize the organic foulants using a large set of analytical tools. Our results showed the need to use both membrane surface autopsy and water quality characterization to identify membrane foulants. NOM foulant was found to be a mixture of proteins, polysaccharides, polyhydroxyaromatics and aminosugars. Residus of microorganisms (membrane cell walls, exopolymers) seem to play a major role in membrane fouling, phenomenon enhance in the humic type NOM.POITIERS-BU Sciences (861942102) / SudocSudocFranceF

Effect of storage of NF membranes on fouling deposits and cleaning efficiency

International audienc

Leukoencephalopathy with cysts and hyperglycinemia may result from NFU1 deficiency

Lipoic acid metabolism defects are new metabolic disorders that cause neurological, cardiomuscular or pulmonary impairment. We report on a patient that presented with progressive neurological regression suggestive of an energetic disease, involving leukoencephalopathy with cysts. Elevated levels of glycine in plasma, urine and CSF associated with intermittent increases of lactate were consistent with a defect in lipoic acid metabolism. Support for the diagnosis was provided by pyruvate dehydrogenase deficiency and multiple mitochondrial respiratory chain deficiency in skin fibroblasts, as well as no lipoylated protein by western blot. Two mutations in the NFU1 gene confirmed the diagnosis. The p.Gly208Cys mutation has previously been reported suggesting a founder effect in Europe

Mutations in human lipoyltransferase gene LIPT1 cause a Leigh disease with secondary deficiency for pyruvate and alpha-ketoglutarate dehydrogenase.

International audienceBACKGROUND: Synthesis and apoenzyme attachment of lipoic acid have emerged as a new complex metabolic pathway. Mutations in several genes involved in the lipoic acid de novo pathway have recently been described, but no mutation was found so far in genes involved in the specific process of attachment of lipoic acid to apoenzymes pyruvate dehydrogenase (PDHc), alpha-ketoglutarate dehydrogenase (alpha-KGDHc) and branched chain alpha-keto acid dehydrogenase (BCKDHc) complexes. METHODS: Exome capture was performed in a boy who developed Leigh disease following a gastroenteritis and had combined PDH and alpha-KGDH deficiency with a unique amino acid profile that partly ressembled E3 subunit (dihydrolipoamide dehydrogenase / DLD) deficiency. Functional studies on patient fibroblasts were performed. Lipoic acid administration was tested on the LIPT1 ortholog lip3 deletion strain yeast and on patient fibroblasts. RESULTS: Exome sequencing identified two heterozygous mutations (c.875C > G and c.535A > G) in the LIPT1 gene that encodes a mitochondrial lipoyltransferase which is thought to catalyze the attachment of lipoic acid on PDHc, alpha-KGDHc, and BCKDHc. Anti-lipoic acid antibodies revealed absent expression of PDH E2, BCKDH E2 and alpha-KGDH E2 subunits. Accordingly, the production of 14CO2 by patient fibroblasts after incubation with 14Cglucose, 14Cbutyrate or 14C 3OHbutyrate was very low compared to controls. cDNA transfection experiments on patient fibroblasts rescued PDH and alpha-KGDH activities and normalized the levels of pyruvate and 3OHbutyrate in cell supernatants. The yeast lip3 deletion strain showed improved growth on ethanol medium after lipoic acid supplementation and incubation of the patient fibroblasts with lipoic acid decreased lactate level in cell supernatants. CONCLUSION: We report here a putative case of impaired free lipoic acid attachment due to LIPT1 mutations as a cause of PDH and alpha-KGDH deficiencies. Our study calls for renewed efforts to understand the mechanisms of pathology of lipoic acid-related defects and their heterogeneous biochemical expression, in order to devise efficient diagnostic procedures and possible therapies