Comparative study of Lactic Acid Bacteria in soy juice fermentation.

Objectifs/ObjectivesThe study aims to improve knowledge over LAB characteristics to ferment a commercial soy juice. Matériels et Méthodes/Materials and methodsFirst 280 strains of LAB from 23 different species of Lactococcus, Streptococcus, Lactobacillus and Leuconostoc genera were tested for their abilities to ferment soy juice containing sucrose, raffinose or stachyose as carbon source and to acidify synthetic media containing sucrose, raffinose or stachyose as unique carbon source. Then, fermented soy juices (FSJ) were produced by 10 h of fermentation (inoculation level 1 %), followed by 14 days of storage at 4 °C. The scents of FSJ were sensorially characterized and FSJ’s primary and secondary metabolites were analyzed. Résultats principaux/Main ResultsWithin 48 h, 39 % of L. lactis strains, 82 % of Lactobacillus strains and all S. thermophilus strains could acidify the synthetic medium with sucrose, as previously described in fermentation patterns of these species. 101 strains representing 18 species could use raffinose and 12 strains representing 6 species could use stachyose. 94 % of the strains that could use sucrose could also ferment soy juice, whose sucrose is the major sugar. Interestingly, 3 strains from species never tested to ferment soy juice, L. kunkeei, L. xiangfangensis and L. pontis revealed abilities to ferment soy juice. Among the 280 strains, 116 strains could acidify soy juice below 6.0 pH units within 10 h. Among the 116 corresponding FSJs, the scents of 48 FSJs were judged as acceptable. The use of sucrose was species-dependent: less residual sucrose was present in FSJs from strains of L. plantarum, L. pentosus, L. lactis, L. delbrueckii and L. coryniformis species compared to S. thermophilus strains. None of the strains used raffinose nor stachyose. S. thermophilus strains produced more lactic acid and less acetic acid than the other strains, in agreement with their homolactic metabolism. Due to acetic acid, FSJs from L. plantarum were more frequently described as ‘sour’. In addition, some strains presented specific traits. For example, CIRM-BIA2115 of L. plantarum produced a floral scent in FSJ likely related to the production of phenylethan-1-ol observed.  ConclusionThe present study is an advance on the knowledge of LAB diversity and their capacity to ferment soy juice. It shows that LAB capacity to use sucrose is important to ferment soy juice and highlights the importance of screening due to the diversity of LAB metabolism

Optimizing lactic fermentation of soy juice

Optimizing lactic fermentation of soy juice. STLOpenday

Identification des interactions positives entre bactéries lactiques en fermentation de jus de soja

Lactofermented soy juices represent an interesting alternative to milk yogurt to increase the part of plant-based proteins in our diet. The choice of lactic acid bacteria (LAB) used for soy juice fermentation is crucial as it determines the organoleptic and nutritional properties of the product. LAB metabolisms are however not well known in soy juice fermentation. In this thesis, 276 strains of 25 species were screened in synthetic media on their ability to ferment stachyose, raffinose and sucrose as unique source of carbon and soy juice. We showed that i) LAB capacity to catabolize sucrose is important to ferment soy juice ii) S. thermophilus strains are the most efficient to ferment soy juice iii) Lactobacillus LAB produce diverse aromatic notes according to the specie and the strain. LAB association can help to improve fermentation, the organoleptic and the nutritional properties.We associated then LAB in duo according to their metabolic complementarities. One coculture out of 32 improved the organoleptic properties of fermented soy juices compared to the monocultures. One coculture out of 12 reduced of 30% the SJ fermentation time (L. plantarum CIRM-BIA777 (Lp777) and L. delbrueckii CIRM-BIA865 (Ld865)).Genomic, metabolomics and transcriptomics approaches were set up to identify the molecular bases of these two LAB cooperation. These approaches revealed three factors of stress of LAB in soy juice fermentation: the limitation of sucrose, the limitation of free amino acids and the oxidative stress. The level of these three stresses were lowered with Lp777 and Ld865.Le jus de soja lactofermenté représente une alternative intéressante au yaourt laitier pour augmenter la part de protéines végétales dans l’alimentation. Le choix des bactéries lactiques (LAB) utilisées pour la fermentation du jus de soja est crucial car il détermine les qualités organoleptiques et nutritionnelles des produits. Les métabolismes des LAB sont cependant mal connus en jus de soja. Dans cette thèse 276 souches de 25 espèces de LAB ont été évaluées sur leur aptitude à fermenter du jus de soja ou des milieux de culture contenant du stachyose, du raffinose ou du saccharose comme unique source de carbone. Nous avons montré que i) la capacité à cataboliser le saccharose est un critère déterminant pour identifier des souches capables de fermenter le jus de soja, ii) les souches de S. thermophilus sont les plus efficaces pour fermenter le jus de soja, iii) les Lactobacillus apportent des notes aromatiques variées selon l’espèce et la souche. L’association de LAB pour améliorer lesfermentaires, organoleptiques et nutritionnelles a été évaluée. Nous avons associé des LAB en duos selon leurs complémentarités métaboliques. Une coculture sur 32 a permis d’améliorer les qualités organoleptiques du produit par rapport aux monocultures. Une coculture sur 12 a permis de réduire de 30% le temps de fermentation du jus de soja par rapport aux monocultures (L. plantarum CIRM-BIA777 (Lp777) et L. delbrueckii CIRM-BIA865 (Ld865))

Maladie de Hodgkin de l'adulte (cinq ans de l'expérience avignonnaise)

AIX-MARSEILLE2-BU Méd/Odontol. (130552103) / SudocPARIS-BIUM (751062103) / SudocSudocFranceF

Design and mathematical optimization of multi-strain ecosystems in winery

International audienceFor food processing, fermentation by microorganisms allows food preservation and production of several fermented products, among the most consumed are bread, cheese, beer and wine. In all these anthropic environments, microbes form communities where individual microorganisms interact in various ways such as competition, predation, commensalism or mutualism that may have a tremendous effect on the final product quality. Exploiting these interactions by ecological engineering (by choosing the good partners in the good proportions) appears to be a promising strategy for improving fermented food. However, it demands a profound understanding of the interaction's mechanisms and an exponential number of experiments to assess all possible microbes combination. To meet these challenges in winery, we choose to guide our ecological designs by a mathematical model simulating the microbial and metabolic dynamics of the oenological fermentation. We perform a deep phenotyping of fermentation driven by different yeast-yeast combination that gives us the necessary information to build a mathematical model (of ordinaries differential equations) that simulate the dynamic of mixed cultures from isolated cultures data. With this model, we test different inoculation protocols (which strain/species, in what proportion and at which time) and evaluate their performance for maximizing different functional traits

Investigation of Methanol Oxidation over Au/Catalysts Using Operando IR Spectroscopy: Determination of the Active Sites, Intermediate/Spectator Species, and Reaction Mechanism

International audienc

Investigation of Methanol Oxidation over Au/Catalysts Using Operando IR Spectroscopy: Determination of the Active Sites, Intermediate/Spectator Species, and Reaction Mechanism

International audienc

Comparative study of Lactic Acid Bacteria in soy juice fermentation.

Objectifs/ObjectivesThe study aims to improve knowledge over LAB characteristics to ferment a commercial soy juice. Matériels et Méthodes/Materials and methodsFirst 280 strains of LAB from 23 different species of Lactococcus, Streptococcus, Lactobacillus and Leuconostoc genera were tested for their abilities to ferment soy juice containing sucrose, raffinose or stachyose as carbon source and to acidify synthetic media containing sucrose, raffinose or stachyose as unique carbon source. Then, fermented soy juices (FSJ) were produced by 10 h of fermentation (inoculation level 1 %), followed by 14 days of storage at 4 °C. The scents of FSJ were sensorially characterized and FSJ’s primary and secondary metabolites were analyzed. Résultats principaux/Main ResultsWithin 48 h, 39 % of L. lactis strains, 82 % of Lactobacillus strains and all S. thermophilus strains could acidify the synthetic medium with sucrose, as previously described in fermentation patterns of these species. 101 strains representing 18 species could use raffinose and 12 strains representing 6 species could use stachyose. 94 % of the strains that could use sucrose could also ferment soy juice, whose sucrose is the major sugar. Interestingly, 3 strains from species never tested to ferment soy juice, L. kunkeei, L. xiangfangensis and L. pontis revealed abilities to ferment soy juice. Among the 280 strains, 116 strains could acidify soy juice below 6.0 pH units within 10 h. Among the 116 corresponding FSJs, the scents of 48 FSJs were judged as acceptable. The use of sucrose was species-dependent: less residual sucrose was present in FSJs from strains of L. plantarum, L. pentosus, L. lactis, L. delbrueckii and L. coryniformis species compared to S. thermophilus strains. None of the strains used raffinose nor stachyose. S. thermophilus strains produced more lactic acid and less acetic acid than the other strains, in agreement with their homolactic metabolism. Due to acetic acid, FSJs from L. plantarum were more frequently described as ‘sour’. In addition, some strains presented specific traits. For example, CIRM-BIA2115 of L. plantarum produced a floral scent in FSJ likely related to the production of phenylethan-1-ol observed.  ConclusionThe present study is an advance on the knowledge of LAB diversity and their capacity to ferment soy juice. It shows that LAB capacity to use sucrose is important to ferment soy juice and highlights the importance of screening due to the diversity of LAB metabolism

Evidence and characterization of a new decamolybdocobaltate cobalt salt : an efficient precursor for hydrotreament catalyst preparation

International audienceHeteropolyanions (HPAs) based on molybdenum and cobalt could be used as an alternative to the conventional ammonium heptamolybdate and cobalt nitrate precursors for the preparation of Co-Mo/ Al2O3 hydrotreating catalysts. With this objective in mind, a cobalt salt of decamolybdocobaltate anion has been synthesized. This salt allows us to prepare catalyst with a Co/Mo atomic ratio of 0.5 corresponding to the optimum value encountered with classical catalyst preparation. The crystal structure refinement has been performed and reveals the formation of a new heteropolyoxomolybdate related to the wellknown Anderson structure. Its structural, spectroscopic, and thermal properties have been investigated by physical techniques such as thermogravimetric analysis mass spectroscopy, X-ray diffraction, X-ray absorption spectroscopy, and vibrational spectroscopy. With the use of this new HPA precursor, initial catalytic results show a significant improvement of hydrodesulfurization catalytic performance