Impact of the environmental parameters on single cell protein production and composition by Cupriavidus necator.

Due to the rapid increase in the world's population, many developing countries are facing malnutrition problems, including famine and food insecurity. Particularly, the deficiency of protein sources becomes a serious problem for human and animal nutrition. In this context, Single Cell Proteins, could be exploited as an alternative source of unconventional proteins. The aim of the study was to investigate SCP production and composition by Cupriavidus necator under various environmental conditions, temperature and pH values. A mono-factorial approach was implemented using batch bioreactor cultures under well-controlled conditions. Results were compared in terms of bacterial growth and SCP composition (proteins, nucleic acids, amino acids and elemental formula). Complementary analyses were performed by flow cytometry to study cell morphology, membrane permeability and the presence of Poly(3-hydroxybutyrate) (PHB) production. Our data confirmed the ability of C. necator to produce high amount of proteins (69 %DW at 30 °C and pH7). The results showed that temperature and pH independently impact SCP production and composition. This impact was particularly observed at the highest temperature (40 °C) and also the lowest pH value (pH5) providing lower growth rates, cell elongation, changes in granularity and lower amounts of proteins (down to 44 %DW at pH5) and nucleic acids. These low percentages were related to the production of PHB production (up to 44 %DW at 40 °C) which is the first report of a PHB accumulation in C. necator under nutrient unlimited conditions.

Screening for Astragalus hamosus Triterpenoid Saponins Using HPTLC Methods: Prior Identification of Azukisaponin Isomers.

Due to their particular structural characteristics, the extraction and isolation of saponins from plants present a serious challenge. In this study, specific extraction protocols were first implemented to extract the secondary metabolites from Astragalus hamosus and, more precisely, the saponins. Subsequent purification of the extracts was based on a single chromatographic technique, high-performance thin-layer chromatography, applying two development systems: a one-step system that separated molecules according to their polarity and a multiple development system that made it possible to detect the triterpenoid saponins, azukisaponin or soyasapogenol at a retarded Rf of 0.2. The difficulties of detecting the Astragalus hamosus saponins encountered during the extraction and purification of the extracts have been highlighted and the strategy carried out to isolate the saponins has been discussed.

Evaluation and prevention of the negative matrix effect of terpenoids on pesticides in apples quantification by gas chromatography-tandem mass spectrometry.

The sample matrix can enhance the gas chromatography signal of pesticide residues relative to that obtained with the same concentration of pesticide in solvent. This paper is related to negative matrix effects observed in coupled gas chromatography-mass spectrometry ion trap (GC/MS2) quantification of pesticides in concentrated extracts of apple peel prepared by the Quick Easy Cheap Effective Rugged and Safe (QuEChERS) method. It is focused on the pesticides most frequently used on the apple varieties studied, throughout the crop cycle, right up to harvest, to combat pests and diseases and to improve fruit storage properties. Extracts from the fleshy receptacle (flesh), the epiderm (peel) and fruit of three apple varieties were studied by high-performance thin-layer chromatography hyphenated with UV-vis light detection (HPTLC/UV visible). The peel extracts had high concentrations of triterpenic acids (oleanolic and ursolic acids), reaching 25mgkg-1, whereas these compounds were not detected in the flesh extracts (<0.05mgkg-1). A significant relationship has been found between the levels of these molecules and negative matrix effects in GC/MS2. The differences in the behavior of pesticides with respect to matrix effects can be accounted for by the physicochemical characteristics of the molecules (lone pairs, labile hydrogen, conjugation). The HPTLC/UV visible method developed here for the characterization of QuEChERS extracts acts as a complementary clean-up method, aimed to decrease the negative matrix effects of such extracts.

Matrix-Matching as an Improvement Strategy for the Detection of Pesticide Residues.

More than 90% of the pesticides residues in apples are located in the peel. We developed a gas chromatography/ion trap tandem mass spectrometry method for investigating all detectable residues in the peel of 3 apple varieties. Sample preparation is based on the use of the Quick Easy Cheap Effective Rugged and Safe method on the whole fruit, the flesh, and the peel. Pesticide residues were quantified with solvent-matched and matrix-matched standards, by spiking apple sample extracts. Matrix effects dependent on the type of extract (fruit, flesh, or peel) and the apple variety were detected. The best data processing methods involved normalizing matrix effect rates by matrix-matched internal/external calibration. Boscalid, captan, chlorpyrifos, fludioxonil, and pyraclostrobin were the most frequently detected pesticides. However, their concentrations in the whole fruit were below European maximum residue levels. Despite negative matrix effects, the residues in peel were detected at concentrations up to 10 times higher than those in whole fruits. Consequently, other pesticide residues present at concentrations below the limit of quantification in the whole fruit were detected in the peel.

Pure short-chain glycerol fatty acid esters and glycerylic cyclocarbonic fatty acid esters as surface active and antimicrobial coagels protecting surfaces by promoting superhydrophilicity.

Pure glycerol fatty acid esters and glycerylic cyclocarbonic fatty acid esters have an amphiphilic structure, giving these biomolecules a broad range of physico-chemical and biological properties. Physico-chemical properties depend on chain lengths, odd or even carbon numbers on the chain, and glyceryl or cyclocarbonic polar heads. The spectrum of melting-point values for these molecules is large. Surface-activity is very important and through determination of the critical aggregation concentration (CAC), some fatty-acid esters are considered as solvo-surfactant biomolecules. Coupling these self-aggregation and crystallization properties, superhydrophilic surfaces were obtained. An efficient durable water repellent coating of various metallic and polymeric surfaces was allowed. Moreover, these fatty acid esters promoting superhydrophilicity showed biological activity against Gram positive, Gram negative, and yeast-like micro-organisms. Such surfaces coated by self-assembled fatty acid esters in a stable coagel state present a novel solution to surface-contamination risks from pathogen proliferation.

Antimicrobial and antioxidant properties of methanol extract, fractions and compounds from the stem bark of Entada abyssinica Stend ex A. Satabie.

BACKGROUND: The aim of this study was to evaluate the antimicrobial and antioxidant activities of the methanol extract, fractions and isolated compounds from Entada abyssinica stem bark, plant used traditionally against gastrointestinal infections. METHODS: The methanol extract of E. abyssinica stem bark was pre-dissolved in a mixture of methanol and water, and then partitioned between n-hexane, ethyl acetate and n-butanol. The ethyl acetate portion was fractionated by column chromatography and the structures of isolated compounds elucidated by analysis of spectroscopic data and comparison with literature data. Antimicrobial activity was assayed by broth microdilution techniques on bacteria and yeasts. The antioxidant activity was determined by DPPH radical scavenging method. RESULTS: Four known compounds [(5S,6R,8aR)-5-(carboxymethyl)-3,4,4a,5,6,7,8,8a-octahydro-5,6,8a-trimethylnaphthalenecarboxylic acid (1), methyl 3,4,5-trihydroxybenzoate (2), benzene-1,2,3-triol (3) and 2,3-dihydroxypropyltriacontanoate (4)] were isolated. Compared to the methanol extract, fractionation increased the antibacterial activities of the n-hexane and ethyl acetate fractions, while the antifungal activities increased in ethyl acetate, n-butanol and aqueous residue fractions. The isolated compounds were generally more active on bacteria (9.7 to 156.2 µg/ml) than yeasts (78.1 to 312.5 µg/ml). Apart from compound 1, the three others displayed DPPH· scavenging activity (RSa), with RSa50 values of 1.45 and 1.60 µg/ml. CONCLUSION: The results obtained from this study support the ethnomedicinal use of E. abyssinica in the treatment of gastrointestinal infections and the isolated compounds could be useful in the standardisation of antimicrobial phytomedicine from this plant.

An individual and a sex odor signature in kittiwakes?: study of the semiochemical composition of preen secretion and preen down feathers.

The importance of olfaction in birds' social behavior has long been denied. Avian chemical signaling has thus been relatively unexplored. The black-legged kittiwake provides a particularly appropriate model for investigating this topic. Kittiwakes preferentially mate with genetically dissimilar individuals, but the cues used to assess genetic characteristics remain unknown. As in other vertebrates, their body odors may carry individual and sexual signatures thus potentially reliably signaling individual genetic makeup. Here, we test whether body odors in preen gland secretion and preen down feathers in kittiwakes may provide a sex and an individual signature. Using gas chromatography and mass spectrometry, we found that male and female odors differ quantitatively, suggesting that scent may be one of the multiple cues used by birds to discriminate between sexes. We further detected an individual signature in the volatile and nonvolatile fractions of preen secretion and preen down feathers. These results suggest that kittiwake body odor may function as a signal associated with mate recognition. It further suggests that preen odor might broadcast the genetic makeup of individuals, and could be used in mate choice to assess the genetic compatibility of potential mates.