High-throughput screening of Mucoromycota fungi for production of low- and high-value lipids

publishedVersio

Production et signalisation dépendante du monoxyde d'azote dans la lignée verte la surprise des microalgues

National audienc

Production et signalisation dépendante du monoxyde d'azote dans la lignée verte la surprise des microalgues

National audienc

The evolution of nitric oxide signalling diverges between the animal and the green lineages

International audienceNitric oxide (NO) is a ubiquitous signalling molecule with widespread distribution in prokaryotes and eukaryotes where it is involved in countless physiological processes. While the mechanisms governing NO synthesis and signalling are well established in animals, the situation is less clear in the green lineage. Recent investigations have shown that NO synthase (NOS), the major enzymatic source for NO in animals, is absent in land plants but present in a limited number of algae. First detailed analysis highlighted that these new NOSs are functional but display specific structural features and probably original catalytic activities. Completing this picture, analyses were undertaken in order to investigate whether major components of the prototypic NO/cyclic GMP signalling cascades mediating many physiological effects of NO in animals were also present in plants. Only few homologues of soluble guanylate cyclases, cGMP-dependent protein kinases, cyclic nucleotide-gated channels and cGMP-regulated phosphodiesterases, were identified in some algal species and their presence did not correlate with that of NOSs. In contrast, GSNO reductase, a critical regulator of S-nitrosothiols, was recurrently found. Overall, these findings highlight that plants do not mediate NO signalling through the classical NO/cGMP-signalling module and support the concept that S-nitrosation is a ubiquitous NO-dependent signalling mechanism

Production de molécules antifongiques par des bactéries levains dans les matrices laitières : Identification, mode d’action des molécules et interactions avec la matrice

Les protéines du lait constituent une véritable malle au trésor. Les avancées scientifiques actuelles sur le lait mettent de plus en plus en exergue la plasticité des protéines laitières, souvent décrites comme l’or blanc du lait. La capacité de ces protéines à former des assemblages aptes à fonctionnaliser des interfaces, eau-huile et eau-air, pour obtenir des émulsions et des mousses ; à texturer les produits ou encore à vectoriser des molécules d’intérêt offre un énorme potentiel d’innovation. Ce potentiel s’inscrit dans la tendance du Clean Label et la création de nouveaux produits laitiers 100% lait.Le projet PROFIL (PROtéines Fonctionnalisées pour l’Industrie Laitière) a été bâti sur ces extraordinaires découvertes. Il réunit sept partenaires académiques et un consortium de 10 industriels laitiers regroupés au sein du consortium BBA.L’objectif de la journée du 21 septembre est de partager avec les chercheurs, académiques et industriels les résultats marquants de PROFIL qui seront présentés par six doctorants

Antifungal Microbial Agents for Food Biopreservation—A Review

Food spoilage is a major issue for the food industry, leading to food waste, substantialeconomic losses for manufacturers and consumers, and a negative impact on brand names.Among causes, fungal contamination can be encountered at various stages of the food chain(e.g., post-harvest, during processing or storage). Fungal development leads to food sensorydefects varying from visual deterioration to noticeable odor, flavor, or texture changes but canalso have negative health impacts via mycotoxin production by some molds. In order to avoidmicrobial spoilage and thus extend product shelf life, different treatments—including fungicidesand chemical preservatives—are used. In parallel, public authorities encourage the food industryto limit the use of these chemical compounds and develop natural methods for food preservation.This is accompanied by a strong societal demand for ‘clean label’ food products, as consumers arelooking for more natural, less severely processed and safer products. In this context, microbial agentscorresponding to bioprotective cultures, fermentates, culture-free supernatant or purified molecules,exhibiting antifungal activities represent a growing interest as an alternative to chemical preservation.This review presents the main fungal spoilers encountered in food products, the antifungalmicroorganisms tested for food bioprotection, and their mechanisms of action. A focus is madein particular on the recent in situ studies and the constraints associated with the use of antifungalmicrobial agents for food biopreservation

Microtiter plate cultivation of oleaginous fungi and monitoring of lipogenesis by high-throughput FTIR spectroscopy

Background Oleaginous fungi can accumulate lipids by utilizing a wide range of waste substrates. They are an important source for the industrial production of omega-6 polyunsaturated fatty acids (gamma-linolenic and arachidonic acid) and have been suggested as an alternative route for biodiesel production. Initial research steps for various applications include the screening of fungi in order to find efficient fungal producers with desired fatty acid composition. Traditional cultivation methods (shake flask) and lipid analysis (extraction-gas chromatography) are not applicable for large-scale screening due to their low throughput and time-consuming analysis. Here we present a microcultivation system combined with high-throughput Fourier transform infrared (FTIR) spectroscopy for efficient screening of oleaginous fungi. Results The microcultivation system enables highly reproducible fungal fermentations throughout 12 days of cultivation. Reproducibility was validated by FTIR and HPLC data. Analysis of FTIR spectral ester carbonyl peaks of fungal biomass offered a reliable high-throughput at-line method to monitor lipid accumulation. Partial least square regression between gas chromatography fatty acid data and corresponding FTIR spectral data was used to set up calibration models for the prediction of saturated fatty acids, monounsaturated fatty acids, polyunsaturated fatty acids, unsaturation index, total lipid content and main individual fatty acids. High coefficients of determination (R2 = 0.86–0.96) and satisfactory residual predictive deviation of cross-validation (RPDCV = 2.6–5.1) values demonstrated the goodness of these models. Conclusions We have demonstrated in this study, that the presented microcultivation system combined with rapid, high-throughput FTIR spectroscopy is a suitable screening platform for oleaginous fungi. Sample preparation for FTIR measurements can be automated to further increase throughput of the system.publishedVersio

Determination of stocking density limits for Crassostrea gigas larvae reared in flow-through and recirculating aquaculture systems and interaction between larval density and biofilm formation

WOS:000407887300001International audienceThe first aim of this study was to determine the stocking density limits for Pacific oyster Crassostrea gigas larvae reared in flow-through system (FTS) and recirculating aquaculture systems (RAS). The second aim was to examine biofilm formation on the larval tank wall and its interaction with larvae growth. Three larvae concentrationswere tested: 50, 150, and 300mL(-1). Chemical parameters and larvae performance were measured. The biofilm was observed by scanning electron microscopy, and its bacterial composition was investigated by pyrosequencing analysis of part of the 16S rRNA gene. The highest growth (13 mu mday(-1)), survival (87%) and metamorphosis (50%) rates were observed in FTS at 50 larvaemL(-1), while lower and similar performances occurred at 150 larvaemL(-1) in both systems. At 300 larvaemL(-1), performances dropped with occurrence of mortality. Biofilm thickness increased with larval density. The pioneer bacteria were coccobacilli followed by filamentous bacteria. The latter constituted abundant braids at the end of rearing at high larval concentrations. The first colonizers were mainly Rhodobacteraceae (alpha-Proteobacteria). The filamentous bacteria were Saprospirae (Bacteroidetes) and Anaerolineae (Chloroflexi). The biofilm was also made up of other minor groups, including Actinobacteria, Planctomycetes, delta-, gamma-Proteobacteria, and Flavobacteriales. The biofilm'scompositionwas more similar to that found in a sewage reactor than in open-sea collectors, which might negatively influence larval rearing due to potential metabolites. This first study on biofilms provides insights into the interaction between rearing density and larvae performance

: Antifungal lactobacilli combinations: identification of antifungal compounds produced in dairy products

Fungi are commonly responsible for dairy product spoilage, which leads to substantial economic losses for the dairy industry as well as consumer dissatisfaction. Lactic acid bacteria can play an active role in the bioprotection of fermented dairy product, by producing a large range of antifungal metabolites. In a previous study, 3 binary combinations of lactobacilli strains were selected from a screening of the antifungal activity of 32 strains tested as adjunct cultures in yogurt and cheese models and the applicability of 2 of them in dairy products was validated at the pilot scale in sour cream and semi-hard cheese. Thus, the aim of the present study was to investigate the compounds produced by these antifungal cultures in these dairy products with a potential role in the observed antifungal activity. Using four different analytical methods including high performance liquid chromatography and gas chromatography combined or not with mass spectrometry, 53 compounds with known antifungal activity were detected in at least one of the four dairy products analyzed. Each antifungal culture produced a cocktail of 2 to 27 compounds, depending on the product. Acetic acid, diacetyl, hydroxyphenyllactic acid, pyruvic acid, phenyllactic acid, succinic acid, decanoic acid and some long-chain unsaturated fatty acids were the most commonly identified compounds. Their concentrations markedly differed according to the considered dairy product. Lactic, acetic, and citric acids were the most abundant compounds, while most of the other compounds were present in concentrations <100 mg/kg. Thirty-one compounds were in significantly higher concentrations (p. value < 0.05) in at least one product inoculated with 1 or more of the tested antifungal cultures compared to the controls without antifungal culture. Overall, by analyzing the antifungal compounds in 4 dairy products, this study provides an expanded view of compounds produced by efficient antifungal cultures