Obtention d'hydrolysats inhibiteurs de l'Enzyme de conversion de l'angiotensine par fermentation de lactosérum caprin. Caractérisation de peptides d'intérêt biologique

L hydrolyse enzymatique des protéines du lactosérum (a-lactalbumine et b-lactoglobuline) permet la libération de peptides potentiellement bioactifs (antihypertenseurs, antibactériens, antitumoraux ). Au cours de cette étude, six hydrolysats potentiellement antihypertenseurs ont pu être obtenus après fermentation de lactosérum caprin par 25 microflores de fromages. L hydrolysat présentant l activité la plus importante provient de la fermentation du lactosérum par une co-culture de Lactobacillus paracasei et Candida parapsilosis issus de la microflore d un fromage de type Comté. Au cours de la fermentation, C. parapsilosis excrète au moins une protéase acide responsable de l hydrolyse de l a-la, celle-ci étant activée au cours de l acidification du milieu par la croissance de L. paracasei. Un peptide potentiellement antihypertenseur de séquence WLAHK a pu être identifié au sein de cet hydrolysat. Ce peptide présente un IC50 de l ordre de 8 M. Au cours d une digestion gastro-intestinale in vitro, celui-ci est dégradé par la chymotrypsine en deux peptides P1 et P2. Alors que le peptide WLAHK présente une activité inhibitrice de l ECA de 35% pour une concentration de l ordre de 4 g/ml, aucune activité n a pu être observée pour une même quantité de peptides P1 et P2 testée.LA ROCHELLE-BU (173002101) / SudocSudocFranceF

Balancing Energy Efficiency and Fossil Fuel: The Role of Carbon Pricing

International audienceEnergy efficiency is likely to remain a valuable support for meeting climate challenges because it involves using less primary energy to produce the same final service. We explore energy efficiency potential in relation to different fossil fuel extraction cost schemes crossed with a carbon pricing scenario built using various global carbon taxes. This sensitivity analysis relies on prospective studies conducted with the technical-and-economic, bottom-up optimization model TIAM-FR (TIMES Integrated Assessment Model), where energy efficiency is endogenized

Impacts of fossil fuel extraction costs and carbon pricing on energy efficiency policies

International audienceEnergy efficiency is llikely to remain a valuable support for meeting climate challenges because it involves using less primary energy to produce the same final service. However, efficient solutions adapted to industrial and construction stakeholders are being put into question by the recent drop in crude oil prices and the development of non-conventional resources, which reduce the incentive to save energy. These strategies are also very sensitive to carbon pricing, which can stimulate or weaken incentives created by crude oil prices. We explore energy efficiency potential in relation to different fossil fuel extraction cost schemes crossed with a carbon pricing scenario built using various global carbon taxes. This sensitivity analysis relies on prospective studies conducted with the technical-and-economic, bottom-up optimization model TIAM-FR (TIMES Integrated Assessment Model developed at the Center for Applied Mathematics MINES ParisTech), where energy efficiency is endogenized: thus, the system reaches the optimal efficiency level according to cost constraints. This representation has been implemented and calibrated for the industrial, residential and tertiary sectors to improve understanding of the balance between energy efficiency potential when considering fossil fuel extraction costs and carbon pricing patterns

Lactococcus lactis Diversity Revealed by Targeted Amplicon Sequencing of purR Gene, Metabolic Comparisons and Antimicrobial Properties in an Undefined Mixed Starter Culture Used for Soft-Cheese Manufacture

International audienceThe undefined mixed starter culture (UMSC) is used in the manufacture of cheeses. Deciphering UMSC microbial diversity is important to optimize industrial processes. The UMSC was studied using culture-dependent and culture-independent based methods. MALDI-TOF MS enabled identification of species primarily from the Lactococcus genus. Comparisons of carbohydrate metabolism profiles allowed to discriminate five phenotypes of Lactococcus (n = 26/1616). The 16S sequences analysis (V1–V3, V3–V4 regions) clustered the UMSC microbial diversity into two Lactococcus operational taxonomic units (OTUs). These clustering results were improved with the DADA2 algorithm on the housekeeping purR sequences. Five L. lactis variants were detected among the UMSC. The whole-genome sequencing of six isolates allowed for the identification of the lactis subspecies using Illumina® (n = 5) and Pacbio® (n = 1) technologies. Kegg analysis confirmed the L. lactis species-specific niche adaptations and highlighted a progressive gene pseudogenization. Then, agar spot tests and agar well diffusion assays were used to assess UMSC antimicrobial activities. Of note, isolate supernatants (n = 34/1616) were shown to inhibit the growth of Salmonella ser. Typhimurium CIP 104115, Lactobacillus sakei CIP 104494, Staphylococcus aureus DSMZ 13661, Enterococcus faecalis CIP103015 and Listeria innocua CIP 80.11. Collectively, these results provide insightful information about UMSC L. lactis diversity and revealed a potential application as a bio-protective starter culture

Bacteriocin Detection from Whole Bacteria by Matrix-Assisted Laser Desorption Ionization-Time of Flight Mass Spectrometry

Class I bacteriocins (lantibiotics) and class II bacteriocins are antimicrobial peptides secreted by gram-positive bacteria. Using two lantibiotics, lacticin 481 and nisin, and the class II bacteriocin coagulin, we showed that bacteriocins can be detected without any purification from whole producer bacteria grown on plates by matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF-MS). When we compared the results of MALDI-TOF-MS performed with samples of whole cells and with samples of crude supernatants of liquid cultures, the former samples led to more efficient bacteriocin detection and required less handling. Nisin and lacticin 481 were both detected from a mixture of their producer strains, but such a mixture can yield additional signals. We used this method to determine the masses of two lacticin 481 variants, which confirmed at the peptide level the effect of mutations in the corresponding structural gene