The substrate specificities of sunflower and soybean phospholipases D using transphosphatidylation reaction

<p>Abstract</p> <p>Background</p> <p>Phospholipase D (PLD) belongs to a lipolytic enzyme subclass which catalyzes the hydrolysis and transesterification of glycerophospholipids at the terminal phosphodiester bond.</p> <p>Results</p> <p>In this work, we have studied the substrate specificity of PLDs from germinating sunflower seeds and cultured-soybean cells, using their capacity of transphosphatidylation. In the presence of a nucleophilic acceptor, such as [¹⁴C]ethanol, PLD catalyzes the production of phosphatidyl-[¹⁴C]-ethanol. The resulting product is easily identified since it is well separated from the other lipids by thin-layer chromatography. The main advantage of this assay is that the phospholipid used as substrate does not need to be radiolabelled and thus allow us a large choice of polar heads and fatty acids. <it>In vitro</it>, we observed that sunflower and soybean cell PLD show the following decreasing order of specificity: phosphatidylcholine, phosphatidylethanolamine and phosphatidylglycerol; while phosphatidylserine and phosphatidylinositol are utilized much less efficiently.</p> <p>Conclusions</p> <p>The substrate specificity is modulated by the fatty acid composition of the phosphatidylcholine used as well as by the presence of other charged phospholipids.</p

Strategy for improving extracellular lipolytic activities by a novel thermotolerant Staphylococcus sp. strain

<p>Abstract</p> <p>Background</p> <p>Extracellular bacterial lipases received much attention for their substrate specificity and their ability to function under extreme environments (pH, temperature...). Many staphylococci produced lipases which were released into the culture medium. Reports of extracellular thermostable lipases from <it>Staphylococcus </it>sp. and active in alkaline conditions are not previously described.</p> <p>Results</p> <p>This study focused on novel strategies to increase extracellular lipolytic enzyme production by a novel <it>Staphylococcus </it>sp. strain ESW. The microorganism needed neutral or alkaline pH values between 7.0 and 12.0 for growth. For pH values outside this range, cell growth seemed to be significantly inhibited. <it>Staphylococcus </it>sp. culture was able to grow within a wide temperature range (from 30 to 55°C). The presence of oils in the culture medium leaded to improvements in cells growth and lipolytic enzyme activity. On the other hand, although chemical surfactants leaded to an almost complete inhibition of growth and lipolytic enzyme production, their addition along the culture could affect the location of the enzyme. In addition, our results showed that this novel <it>Staphylococcus </it>sp. strain produced biosurfactants simultaneously with lipolytic activity, when soapstock (The main co-product of the vegetable oil refining industry), was used as the sole carbon source.</p> <p>Conclusion</p> <p>A simultaneous biosurfactant and extracellular lipolytic enzymes produced bacterial strain with potential application in soap stock treatment</p

A newly high alkaline lipase: an ideal choice for application in detergent formulations

<p>Abstract</p> <p>Background</p> <p>Bacterial lipases received much attention for their substrate specificity and their ability to function in extreme environments (pH, temperature...). Many staphylococci produced lipases which were released into the culture medium. Reports of thermostable lipases from <it>Staphylococcus </it>sp. and active in alkaline conditions are not previously described.</p> <p>Results</p> <p>A newly soil-isolated <it>Staphylococcus </it>sp. strain ESW secretes an induced lipase in the culture medium. The effects of temperature, pH and various components in a detergent on the activity and stability of <it>Staphylococcus </it>sp. lipase (SL1) were studied in a preliminary evaluation for use in detergent formulation solutions. The enzyme was highly active over a wide range of pH from 9.0 to 13.0, with an optimum at pH 12.0. The relative activity at pH 13.0 was about 60% of that obtained at pH 12.0. It exhibited maximal activity at 60°C. This novel lipase, showed extreme stability towards non-ionic and anionic surfactants after pre-incubation for 1 h at 40°C, and relative stability towards oxidizing agents. Additionally, the crude enzyme showed excellent stability and compatibility with various commercial solid and liquid detergents.</p> <p>Conclusions</p> <p>These properties added to the high activity in high alkaline pH make this novel lipase an ideal choice for application in detergent formulations.</p

Characterization of cellular toxicity induced by sub-lethal inorganic mercury in the marine microalgae Chlorococcum dorsiventrale isolated from a metal-polluted coastal site

Mercury (Hg) is a global pollutant that affects numerous marine aquatic ecosystems. We isolated Chlorococcum dorsiventrale Ch-UB5 microalga from coastal areas of Tunisia suffering from metal pollution and analyzed its tolerance to Hg. This strain accumulated substantial amounts of Hg and was able to remove up to 95% of added metal after 24 and 72 h in axenic cultures. Mercury led to lesser biomass growth, higher cell aggregation, significant inhibition of photochemical activity, and appearance of oxidative stress and altered redox enzymatic activities, with proliferation of starch granules and neutral lipids vesicles. Such changes matched the biomolecular profile observed using Fourier Transformed Infrared spectroscopy, with remarkable spectral changes corresponding to lipids, proteins and carbohydrates. C. dorsiventrale accumulated the chloroplastic heat shock protein HSP70B and the autophagy-related ATG8 protein, probably to counteract the toxic effects of Hg. However, long-term treatments (72 h) usually resulted in poorer physiological and metabolic responses, associated with acute stress. C. dorsiventrale has potential use for Hg phycoremediation in marine ecosystems, with the ability to accumulating energetic reserves that could be used for biofuel production, supporting the notion of using of C. dorsiventrale for sustainable green chemistry in parallel to metal removalThis work was supported by grant from the Tunisian Ministry of Higher Education and Scientific Research. This work was also funded by the Spanish Ministry of Science and Technology (AEI) (projects AGL2014-53771-R and AGL2017-87591-R

Antidiabetic potential of mucilage fraction extracted from Astragalus gyzensis seeds

The objective of the current work is to extract a new mucilage fraction from Astragalus gyzensis Bunge. seeds, which are collected from the El-Oued province (septentrional Algerian Sahara) and evaluated for their antidiabetic potential. The mucilage fraction is obtained using hot water extraction followed by alcoholic precipitation of polysaccharides by cold ethanol (96%). The primary investigation was performed by describing the main structural features of the extract through colorimetric assays, Fourier-transform infrared spectroscopy and thin-layer chromatography analysis using two systems. Biological activity was also monitored by antidiabetic activity by testing the inhibition of α-amylase and α-glucosidase enzymes in vitro. The extraction yield was 20.69%. The chemical composition mainly consisted of 78.60±0.29% carbohydrates, among them 63.92±0.67% neutral sugar, 15.78±0.76% uronic acid, 8.08±0.04% proteins and 2.57±0.05% phenolic compounds. The results obtained by thin-layer chromatography analysis showed the dominance of mannose and galactose. Fourier-transform infrared spectrum showed characteristic bands expected galactomannans. The investigations highlighted the antihyperglycemic effect in a dose-dependent manner by the inhibition of the α-amylase enzyme (IC50=0.8±0.005 mg/mL). These factors make it suitable for the industrial application of dietary supplement fiber made for diabetic individuals. DOI: http://dx.doi.org/10.5281/zenodo.761853

Bioconversion en conditions hypersalines de structures aromatiques par des bactéries isolées du sous-produit de fermentation des olives en saumures

Dans ce travail, nous nous sommes intéressés à l'isolement de bactéries aérobies halophiles et/ou halotolérantes, capables de transformer et/ou de dégrader certains composés aromatiques. Ces isolements ont été recherchés à partir des eaux de fermentation des olives de table disponibles en Tunisie et plus généralement dans le pourtour méditerranéen. Une nouvelle souche halotolérante, Bacillus sp. YAS1 nouvellement isolée à partir des eaux de fermentation des olives de table, représente la première bactérie transformant le tyrosol en p-hydroxyphénylacétate en conditions salines. L'étude du métabolisme de différents composés aromatiques montre que la souche Bacillus sp. YAS1 emprunte une voie originale de bioconversion du tyrosol, sans dégradation ultérieure du noyau aromatique. Parmi les souches présentes dans ce type de biotope, deux souches ont été plus particulièrement étudiées, les souches IMPC et Mar. La souche IMPC est une bactérie halophile modérée, qui a été isolée après enrichissement sur l'acide-p-coumarique. La souche IMPC dégrade complètement l'acide p-coumarique via l'acide protocatéchuique en conditions hypersalines. Cette souche a la particularité de décarboxyler plusieurs composés cinnamiques en leurs dérivés d'acide benzoïque correspondants. La souche Mar a été aussi isolée après enrichissement sur l'acide férulique. Cette souche représente la première bactérie halophile capable de transformer l'acide férulique en acide vanillique dans des conditions hypersalines. Cette souche est très prometteuse pour la production de l'acide vanillique un composé important pour les applications biotechnologiquesAIX-MARSEILLE1-BU Sci.St Charles (130552104) / SudocSudocFranceF

Sulfated exopolysaccharides from Porphyridium cruentum: A useful strategy to extend the shelf life of minced beef meat

International audienc

Combined Effect of Spirulina Platensis and Punica Granatum Peel Extacts: Phytochemical Content and Antiphytophatogenic Activity

Biological control is one of the effective methods for managing plant diseases in food production and quality. In fact, there is a growing trend to find new bio-sources, such as marine algae and vegetal by-products. In this study, pomegranate (Punica granatum) peel (S1) and Spirulina platensis (S2) alone and in combinations, pomegranate peel/Spirulina: 25%/75% (S3) and 50%/50% (S4) were evaluated for antimycotoxigenic and antiphytopathogenic fungal properties. The chemical composition (moisture, dry matter, protein, lipid and ash) as well as total polyphenols, flavonoids and anthocyanins content were evaluated in the four extracts. Using agar diffusion and broth microdilution methods, the anti Fusarium oxysporum, Fusarium culmorum, Fusarium graminearum, Aspergillus niger and Alternaria alternata activities were measured and their correlations with phytochemical content were evaluated. Interestingly, combinations between Spirulina at 75% and pomegranate peel at 25% (S3) have a significant impact (p &lt; 0.05) on the antifungal activity compared to S1, S2 and S4. These findings underlie the effectiveness of biocontrols over standard fungicides and imply that existing methods can be further improved by synergistic effects while maintaining food safety in an eco-friendly manner

Microalgae xanthophylls: from biosynthesis pathway and production techniques to encapsulation development.

International audiencein the last 20 years, xanthophylls from microalgae have gained increased scientific and industrial interests. this review highlights the essential issues that concern this class of high value compounds. firstly, their chemical diversity as the producer microorganisms was detailed. then, the use of conventional and innovative extraction techniques was discussed. upgraded knowledge on the biosynthetic pathway of the main xanthophylls produced by photosynthetic microorganisms was reviewed in depth, providing new insightful ideas, clarifying the function of these active biomolecules. in addition, the recent advances in encapsulation techniques of astaxanthin and fucoxanthin, such as spray and freeze drying, gelation, emulsification and coacervation were updated. providing information about these topics and their applications and advances could be a help to students and young researchers who are interested in chemical and metabolic engineering, chemistry and natural products communities to approach the complex thematic of xanthophylls