Pomological evaluation of some genotypes of figs (Ficus carica L.)

In order to enhance some cultivars of fig widespread in the Oasis of Gafsa located in the south of Tunisia (arid bioclimatic stage). Four cultivars of Fig (Ficus Carica L.) were evaluated 'Sawoudi', 'Bayoudhi', ' Mlouki ',' Assal '. The phenolic composition and antioxidant activities of skin, pulp and whole fruit were determinate. In this study the results showed that the total polyphenol contents of Assal cultivar were the highest in the various tissues (190.98-697.94 mg/100g FW). In all cultivars and whatever the tissue examined (whole fruit, peel, and flesh), the flavonoid content varied from 14.71 to 63.92 mg/100gFW). Also, Assal cultivar was the richest with flavonoids in comparison to other cultivars. The ortho-diphenol content varied from 8.21 to 118.62 mg/100g FW. Indeed, the flesh of Sawoudi and Bayoudhi cultivars had the higher ortho-diphenol content. On the other hand, Bayoudhi (flesh) was the more concentrated in anthocyanins which was around 2.8 mg/100g FW. However, the highest anthocyanin content in the peel was registrated in Sawoudi cultivar (0.934mg/100g FW). This cultivar had the most important antioxidant activity (p <0.05) evaluated by the four test DPPH, ABTS, reducing power and phosphomolybdenum. The comparison between the different cultivars has shown that Assal had the highest levels of total polyphenols and flavonoids as well as potential antioxidant activity. The results of the present study suggest that fig skin may be useful as a viable source of natural antioxidants for agri-food applications

Antioxidant properties of Enterobacter cloacae C3 lipopeptides in vitro and in model food emulsion

The present work aims to investigate the in vitro antioxidant activities of Enterobacter cloacae C3 lipopeptides, as well as the stability of sunflower oil in water (o/w) emulsion and the conservation of raw beef patties. The C3 lipopeptides were assayed for their antioxidant activity through five different tests. The C3 lipopeptides showed good in vitro antioxidant activities. Lipopeptides C3 exhibited important antioxidant properties in 10% sunflower o/w emulsions during prolonged storage (28 days) at 30°C. The effect of C3 lipopeptides on the oxidative stability of raw beef patties showed effectiveness effect in preventing oxidative degradation of lipids via thiobarbituric acid reactive substance and peroxide methods. Cytotoxicity test using human kidney HEK293 cells showed that studied lipopeptides was nontoxic substances. The results of this study indicate that lipopeptides C3 could be appropriate antioxidant agent in food models as inhibitors of lipid oxidation.Peer ReviewedPostprint (author's final draft

Effect of exogenous gibberellic acid on germination, seedling growth and phosphatase activities in Lettuce under salt stress

The effect of gibberellic acid on germination and seedling growth of lettuce variety, Vista, under salinity conditions was studied. A reduction in germination percentage, roots and shoots length and fresh weight were observed under salt stress. At the same time, acid phosphatase and phytase activities in roots were reduced by NaCl. The exogenous application of gibberellin increased germination percentage and improved length and fresh weight of roots and shoots under salt treatment. It also increased both acid phosphatase and phytase activities in roots under this constraint. The application of gibberellic acid compensated for the negative effect of salinity.Keywords: Acid phosphatase, germination, gibberellic acid, lettuce, phytase, salinity, seedling growt

The conservative effects of lipopeptides from Bacillus methylotrophicus DCS1 on sunflower oil-in-water emulsion and raw beef patties quality

Lipid oxidation was considered as a problem in food conservation. The present study aims to investigate the effect of lipopeptides DCS1 on the conservation of food models against lipid oxidation by determining the primary and the secondary oxidation products. Lipopeptides DCS1 are able to preserve the nutritional properties of the emulsion during 23¿days of storage, at a concentration of 0.0125% (w/w of emulsion), by slowing down the formation of hydroperoxides and malondialdehyde (MDA) compounds. The direct incorporation of lipopeptides in ground beef patties at a concentration of 0.5% (w/w of meat) was found to be more effective than gelatin film enriched with lipopeptides (2.5%, w/w of gelatin) as a coating, in inhibiting lipid oxidation. Furthermore, lipopeptides DCS1 are not toxic to human kidney cells HEK293 up to a concentration of 250¿µg/ml. The results indicate that lipopeptides DCS1 are effective for the preservation of fatty foods against lipid oxidation.Peer ReviewedPostprint (author's final draft

Antioxidant properties, antimicrobial and anti-adhesive acivities of DCS1 lipopeptides from Bacillus methylotrophicus DCS1

Background: The present work aims to investigate the antioxidant and antimicrobial activities as well as the potential of DCS1 lipopeptides produced by Bacillus methylotrophicus DCS1 strain at inhibition and disruption of biofilm formation. Results: The produced biosurfactants were characterized as lipopeptides molecules by using thin layer chromatography (TLC) and Fourier transform infrared spectroscopy (FT-IR). The DCS1 lipopeptides were assayed for their antioxidant activity through five different tests. The scavenging effect on DPPH radicals at a concentration of 1 mg mL−1 was 80.6%. The reducing power reached a maximum value of 3.0 (OD700 nm) at 2 mg mL−1 . Moreover, the DCS1 lipopeptides exhibited a strong inhibition of β-carotene bleaching by linoleic acid assay with 80.8% at 1 mg mL−1 and showed good chelating ability and lipid peroxidation inhibition. The in vitro antimicrobial activity of DCS1 lipopeptides showed that they display significant antibacterial and antifungal activities. The anti-adhesive activity of DCS1 lipopeptides was evaluated against several pathogenic microorganisms. The lipopeptides showed excellent anti-adhesive activity, even at low concentrations, in a polystyrene surface pre-treatment against all the microorganisms tested. Further, they can disrupt performed biofilms. Conclusion: This study shows the potentiality of DCS1 lipopeptides as natural antioxidants, antimicrobial and/or anti-adhesive agent for several biomedical and industrial applications

Isolation and characterization of kurstakin and surfactin isoforms produced by Enterobacter cloacae C3 strain

In this work, the extraction, structural analysis, and identification as well as antimicrobial, anti‐adhesive, and antibiofilm activities of lipopeptides produced by Enterobacter cloacae C3 strain were studied. A combination of chromatographic and spectroscopic techniques offers opportunities for a better characterization of the biosurfactant structure. Thin layer chromatography (TLC) and HPLC for amino acid composition determination are used. Efficient spectroscopic techniques have been utilized for investigations on the biochemical structure of biosurfactants, such as Fourier transform infrared (FT‐IR) spectroscopy and mass spectrometry analysis. This is the first work describing the production of different isoforms belonging to kurstakin and surfactin families by E cloacae strain. Three kurstakin homologues differing by the fatty acid chain length from C10 to C12 were detected. The spectrum of lipopeptides belonging to surfactin family contains various isoforms differing by the fatty acid chain length as well as the amino acids at positions four and seven. Lipopeptide C3 extract exhibited important antibacterial activity against Gram‐positive and Gram‐negative bacteria, antifungal activity, and interesting anti‐adhesive and disruptive properties against biofilm formation by human pathogenic bacterial strains: Salmonella typhimurium, Klebsiella pneumoniae, Staphylococcus aureus, Bacillus cereus, and Candida albicans

Structural characterization and identification of cyclic lipopeptides produced by Bacillus methylotrophicus DCS1 strain

Bacillus methylotrophicus DCS1 strain was isolated from diesel contaminated soil and screened for its ability to produce biosurfactants; it was found effective for the production of surface active molecules. The structural characterization of the isolated lipopeptides was studied by a variety of analytical techniques. The organic extract of DCS1 'lipopeptides was fractionated by silica gel column chromatography (60 Mesh). Fractions containing lipopeptides were collected and identified by tandem mass spectrometry MALDI-TOF-MS and MALDI-TOF MS2. The crude biosurfactants contains a mixture of homologous lipopeptides with molecular weights between 1016 and 1556 Da. Mass spectrometry analysis of partially purified lipopeptides revealed that it contains different isoforms belonging to three families: surfactin, iturin and fengycin. To identify lipopeptides isoforms, MALDI-TOF MS2 was used and ions representing characteristic fragmentations were detected. The mass spectrometry characterization revealed the presence of four variants of surfactin lipopeptides, four variants of pumilacidin that differ according to the-beta-hydroxy fatty acid chain length as well as the type of amino acid at position 7, five variants of iturin A/mycosubtilin varying in the beta-amino fatty acid chain length from C12 to C16, C16 iturin Cl, five isoforms of bacillomycin D varying in the beta-amino fatty acid chain length from C14 to C18, and six fengycin isoforms that differ according to the length of the beta-hydroxy fatty acid side chain as well as the amino acid at position 6. The capacity of B. methylotrohicus DCS1 strain to produce many lipopeptides isoforms belonging to different families and having a structural diversity is a very interesting characteristic that allows them to be used in various fields of biotechnological applications

Enhanced accumulation of root hydrogen peroxide is associated with reduced antioxidant enzymes under isoosmotic NaCl and Na2SO4 salinities

The inhibitory effect of salt stress on lettuce is one of the main reasons for the reduction of plant growth and crop productivity. In the present study, the response of two lettuce varieties Verte and Romaine to isoosmotic NaCl and Na2SO4 treatments were examined. Both varieties were grown in pots containing nutrient Hoagland solution with or without 100 mM NaCl or 77 mM Na2SO4. Relative growth rate (RGR), hydraulic parameters, root ion content, proline and several antioxidant activities in roots were measured after 12 days of treatment. After prolonged exposure to salt stress, relative growth rate and water content of lettuce significantly decreased. Roots accumulated high level of Na+ under both salts, whereas the accumulation of K+ and Ca2+ decreased. High level of Na+ inside the cells inhibited the K+ uptake and resulted in increased K+/Na+ ratio. In addition, salt stress also caused an increase in the accumulation of proline. This result suggests that proline may play a crucial role in protecting lettuce under salt stress especially in response to Na2SO4 treatment. Membrane damage estimated by electrolyte leakage (EL) increased especially in response to Na2SO4 treatment in both varieties, but Verte had significantly lower EL relative to Romaine under 100 mM NaCl. A reduction in the activities of CAT in both varieties under 100 mM, and GPX activity in Verte under Na2SO4 treatment coincided with an increase in H2O2 level, indicative of cellular damage and a general depression of the antioxidant enzymatic system in lettuce roots.Keywords: Lettuce, NaCl, Na2SO4, RGR, mineral nutrition, antioxidant activities, prolin

Combined effect of hormonal priming and salt treatments on germination percentage and antioxidant activities in lettuce seedlings

Hormonal priming is a pre-sowing treatment that improves seed germination performance and stress tolerance. To understand the physiology of hormonal priming and its association with post priming stress tolerance, we investigated the effect of hormonal priming with increasing gibberellic acid (GA3) concentrations (0, 3, 4.5 and 6 mM) on seedling growth and antioxidant system in lettuce. Germination percentage was higher in lettuce seedlings derived from primed seeds. Radicle and hypocotyl length and dry weight were reduced by salt treatment to a greater extent in non-primed than in primed seeds. Hormonal priming with 4.5 mM GA3 induced the most dramatic decreases in electrolyte leakage (EL) and malondialdehyde (MDA) levels. NaCl increased catalase (CAT) activity in primed and non-primed seeds. The total ascorbate level remained constant in both primed and non-primed seeds under NaCl constraint. These results suggest that hormonal priming might have increased the salt tolerance of lettuce seeds through enhancing the activities of antioxidant enzymes and reducing the membrane damage as estimated using EL and MDA biomarkers.Key words: Ascorbate, germination, hormonal priming, lettuce, salinity