Publications Scientifiques

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Author: search.filters.author.Khemili-Talbi, S.

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    Biodegradation of Petroleum hydrocarbons and Biosurfactant production by an extremely halophilic Archaea Halovivax sp. A21
    (Aljest, 2017) Khemili-Talbi, S.; Kebbouche-Gana, Salima; Akmoussi-Toumi, S.; Gana, M.L.; Lahiani,S.; Ferrioune ,I.; Angar,Y.
    Over the recent few years, biosurfactant has played an important role in the industrial application especially in oil recovery; even in high salinity conditions. The potential of biosurfactant production by the extreme halophilic archaeon Halovivax sp. A21 in the presence of petroleum hydrocarbons (2% v/v) as sole carbon source at high salinity (25% NaCl) has been investigated. The results show the ability of Halovivax sp. A21 to grow and reduce surface tension under an optimum range of pH (7-9), salinities (15-35% NaCl) and temperature (40-45°C) for an optimized volume of 100 ml of the medium for 1000 ml capacity Erlenmeyer flasks with an optimum agitation of 120 rpm. The rates of biosurfactant production on petroleum hydrocarbons were enhanced with increasing NaCl concentration in the medium with an optimum of 25%. Biosurfactant production by Halovivax sp. A21 showed high emulsifying activity (more than 80%) and decreased surface tension (24.5 mN/m). The stability of the produced biosurfactant was determined by different physico-chemical conditions like pH, temperature and salinity. Moreover, the partial purification of the derived biosurfactant by silica gel column chromatography and Thin-layer chromatography revealed that it belongs to the lipopeptide group. Although both catechol dioxygenases participated in the degradation of petroleum hydrocarbons, more induction of catechol 1,2 dioxygenase was observed than the catechol 2,3 dioxygenase which indicated the predominance of the ortho cleavage pathways in the petroleum hydrocarbons degradation by the halophilic strain Halovivax sp. A21. The results demonstrated that strain Halovivax sp. A21 was able to increase the bioavailability of insoluble hydrocarbons, thus facilitating their uptake and their biodegradation even at high salt concentration. Likewise, the search of novel biosurfactants in extremophiles, or the use of microorganisms that present excellent
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    Isolation and Identification of Entomopathogenic Bacteria from Algerian Desert Soil and their Effects against the Migratory Locust, Locusta migratoria (Linnaeus, 1758) (Orthoptera: Acrididae)
    (EGYPTIAN SOC BIOLOGICAL CONTROL PESTS, 2015) Oulebsir-Mohandkaci, H.; Khemili-Talbi, S.; Benzina, F.; Halouane, F.
    After isolation and characterization of some bacteria in the rhizosphere soil of the Algerian desert plants, a total of 17 bacterial strains were isolated. They are mobile, aerobic, with a positive catalase. From these bacterial strains, four were selected for their entomopathogenic potential and identified based on their genetic traits. The rDNA16S sequences of these named strains (B3, B4, B5 and B6) were recorded in the EMBL/EBI data bank and their phylogenetic analysis revealed that they belong to the genera; Pseudomonas, Bacillus and Enterobacter. This study was highlighted on their entomopathogenic activity against the 5th instar larvae of the migratory locust, Locusta migratoria (Linnaeus, 1758) (Orthoptera: Acrididae). The results obtained, one week after treatment, showed that the treated nymphs were highly sensitive to the tested isolates of bacteria, with mortality rates of 100, 98, 71 and 65% for Pseudomonas sp. strain B3 (HF911369), Pseudomonas sp. strain B4 (HF911366) Enterobacter sp. strain B6 (HF911368) and Bacillus sp. strain B5 (HF911367), respectively, in comparison to the control (3.33%)
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    Isolation of an extremely halophilic arhaeon Natrialba sp. C21 able to degrade aromatic compounds and to produce stable biosurfactant at high salinity
    (Springer, 2015) Khemili-Talbi, S.; Kebbouche-Gana, Salima; Akmoussi-Toumi, Siham; Angar, Yassmina; Gana, M.L
    Natrialba sp. strain C21 was isolated from oil contaminated saline water in Ain Salah (Algeria) and has exhibited a good potential for degrading phenol (3 % v/v), naphthalene (3 % v/v), and pyrene (3 % v/v) at high salinity with high growth, enzymatic activity and biosurfactant production. Successful metabolism of aromatic hydrocarbon compounds of the strain Natrialba sp. C21 appears to require the ortho-cleavage pathway. Indeed, assays of the key enzymes involved in the ring cleavage of catechol 1, 2-dioxygenase indicated that degradation of the phenol, naphthalene and pyrene by strain Natrialba sp. C21 was via the ortho-cleavage pathway. Cells grown on aromatic hydrocarbons displayed greater ortho-activities mainly towards catechol, while the meta-activity was very low. Besides, biosurfactants derived from the strain C21 were capable of effectively emulsifying both aromatic and aliphatic hydrocarbons and seem to be particularly promising since they have particular adaptations like the increased stability at high temperature and salinity conditions. This study clearly demonstrates for the first time that strain belonging to the genera Natrialba is able to grow at 25 % (w/v) NaCl, utilizing phenol, naphthalene, and pyrene as the sole carbon sources. The results suggest that the isolated halophilic archaeon could be a good candidate for the remediation process in extreme environments polluted by aromatic hydrocarbons. Moreover, the produced biosurfactant offers a multitude of interesting potential applications in various fields of biotechnology. © 2015 Springer Japan