Mémoires de Master
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Item UTILISATION DES PRODUITS PHYTOSANITAIRES DANS LA REGION DE GHARDAIA(Université de Ghardaïa, 2026) BOUNADJI, Fadila; OULAD YAHIA, ImaneThis study investigates the phytosanitary products used in the Ghardaïa region, an area characterized by intensive agricultural activity. The main objective is to evaluate the degradation kinetics of pesticides in soil as a function of time and temperature. The methodology adopted is based on a mixed approach combining data collection from the Directorate of Agricultural Services (DSA) and the Directorate of Environment to identify the phytosanitary products commonly used in the study area, followed by an experimental investigation of the degradation kinetics of two major pesticides, namely malathion and linuron, in agricultural soil collected from the Ghardaïa region. The experiment was conducted under two exposure conditions: direct solar radiation and shaded conditions. The results revealed significant differences in the degradation behavior of the two pesticides. Malathion exhibited a faster degradation rate under direct solar radiation, with an average residual concentration of 13,68% compared with 15.98 %under shaded conditions. In contrast, linuron showed average residual concentrations of 72,72% under direct solar radiation and 39,74% under shaded conditions, highlighting the influence of the chemical properties of each pesticide on its persistence in soil. These findings contribute to a better understanding of pesticide fate in agricultural soils and provide a scientific basis for optimizing pesticide management practices while reducing the risk of environmental contamination.Item De la ferme à la table : étude des caractéristiques physico- chimiques et microbiologiques d’un fromage artisanal à identité locale ''El Gafs"(UNIVERSITE DE GHARDAIA, 2026) LAHRECHE, KHOULOUD; MOSBAH, FATIMA ZOHRATraditional cheese has become a staple food due to its high nutritional value and unique sensory characteristics. El Gafs cheese, made from raw milk (cow and goat raw milk) and coated with chamomile, rose and esparto grass, has never been the subject of previous studies. Hence the aim of this study is to evaluate both its physicochemical such as pH (pH meter), acidity (titration), dry matter (drying), lipids (Gerber acid-butyrometric method), minerals (calcination) and proteins (Kjeldahl method), microbiological quality (total mesophilic aerobic flora, lactic acid bacteria, lactococci, coliforms, yeasts and moulds, as well as testing for pathogenic bacteria) and sensory parameters (appearance, colour, odour, texture, firmness, taste, lactic flavour and overall acceptability through tasting). The results showed differences between the four cheese varieties in most of the criteria studied; Physicochemical analyses revealed significant differences among the El Gafs cheese varieties, with variations in pH (3.8–5.9), acidity (8–16 °D), dry matter (≈50–61%), proteins (18–39%), lipids (6–14%), and minerals (≈3–4%), influenced by the type of milk and the plant coating. The microbiological criteria revealed the presence of abundant lactic flora, which is characteristic of traditional cheeses made from raw milk, and they also showed the absence of Staphylococcus aureus, Salmonella spp., sulfite-reducing anaerobic bacteria (SRB) and Listeria monocytogenes. Sensory evaluation also revealed greater overall acceptance of the cow’s milk cheese coated with chamomile. The results suggest that the type of milk and the nature of the plant coating influence the characteristics of the cheeses studied. These findings contribute to a better understanding of the nutritional and sanitary quality of this traditional product.Item Recherche des Actinomycetota contribuant à la biosynthèse des nanoparticules d’argent pour des applications antimicrobiennes(Université de Ghardaia, 2026) ABBAS, MARIA; TEBBAKH, BOUCHRAThe main objective of this work is to investigate Actinomycetota involved in the biosynthesis of silver nanoparticles (AgNPs) intended for antimicrobial applications. For this purpose, ten Actinomycetota isolates (L1, L2, L3, L4, L5, L6, L7, L8, L9, and L10) were cultured in ISP2 medium. The biosynthesis of AgNPs was carried out using silver nitrate (AgNO3) as a metallic precursor and the Actinomycetota biomass extract as a reducing and stabilizing agent. The obtained nanoparticles were subsequently purified and dried. To optimize their synthesis, several parameters were studied, including AgNO3 concentration, pH, and temperature. The bioreduction of Ag + ions to Ag 0 was evidenced by the color change of the solution to dark brown, observed for strains L1, L3, L4, L6, L7, and L10 during extracellular synthesis, as well as for strains L1 and L4 during intracellular synthesis. This synthesis was also confirmed by UV-Visible spectrophotometric analysis, which revealed characteristic absorption peaks of silver nanoparticles at 340, 355, 365, 390, 400, 425, 440, and 455 nm. Furthermore, the antimicrobial activity of the synthesized AgNPs was evaluated against various pathogenic microorganisms using the agar well diffusion method. For this study, three strains presenting the most characteristic UV-Visible absorption profiles associated with high AgNP production (L3, L6, and L10) were selected. The results showed strong antimicrobial activity against Candida albicans, followed by moderate activity against Staphylococcus aureus and Aspergillus flavus, as well as weak activity against Pseudomonas aeruginosa. Comparative analysis of the different strains revealed significant variability in their antimicrobial efficacy. Strain L3 stood out with the broadest spectrum of action, inhibiting the growth of all tested microorganisms. It recorded the largest zones of inhibition against Candida albicans (20.67 mm), followed by Aspergillus flavus (13.33 mm), Staphylococcus aureus (12 mm), and Pseudomonas aeruginosa (11.33 mm). Strain L10 presented a more selective activity, limited against Candida albicans (19.83 mm) and against the Gram-positive bacterium Staphylococcus aureus (9.33 mm), without any effect on Pseudomonas aeruginosa or Aspergillus flavus. As for strain L6, it presented the lowest activity, acting only on Candida albicans with an inhibition zone of 17.33 mm, while remaining inactive against the other tested microorganisms.Item Étude comparative du genre Kineosporia fondée sur des approches moléculaires et chimiotaxonomiques utilisant les coefficients de Jaccard et d’Ochiai(Université de Ghardaïa, 2026) BEHISSA, Dounia; BELKACEM, MeriemThis research is based on a two-pronged methodological approach aimed at studying eight species of the genus Kineosporia (phylum Actinomycetota): K. aurantiaca, K. succinea, K. rhizophila, K. mikuniensis, K. rhammosa, K. babensis, K. mesophila, and K. corallincola. On the one hand, a chemotaxonomic analysis was conducted by applying Jaccard and Ochiai similarity coefficients to the chemical composition data of the cell walls. On the other hand, a molecular study was conducted based on 16S rRNA gene sequencing, coupled with bioinformatics algorithms for sequence alignment and genetic distance estimation. The main objective was to identify the most closely related species to Kineosporia corallincola (used as a reference) and to compare the results obtained by these two methods. The results revealed a partial divergence: the chemotaxonomic approach identifies K. aurantiaca as the species closest to K. corallincola, while the molecular analysis identifies K. babensis as the most closely related. This study thus highlights the complementary nature of chemotaxonomic and molecular approaches for reliable taxonomic classification.Item Analyse in silico d’allantoinase d’Actinopolyspora saharensis(Faculté des Sciences de la Nature et de la Vie et des Sciences de la Terre, Université de Ghardaia, 2026) LALI, Yousra; YAGOUB, AsmaAllantoinase (EC 3.5.2.5) is an enzyme belonging to the amidohydrolase family. It is involved in the purine catabolism by hydrolyzing the amide bond between N3 and C4 of allantoin, converting it into allantoate. This reaction constitutes a key step in the biosynthesis and degradation of purines as well as nitrogen recycling in many organisms, including bacteria, fungi, and plants. However, this enzyme is absent in humans, in whom purine metabolism terminates at the formation of uric acid. However, allantoinase remains poorly characterized, particularly in Actinopolyspora saharensis. This study therefore aimed to determine its physicochemical properties, subcellular localization, and 3D structure using bioinformatics approaches. These analyses revealed the acidic nature, stability, and hydrophilicity of this enzyme, as well as its cytoplasmic localization. Secondary structure prediction, performed using the SOPMA tool, revealed a predominance of loops (50.33%), followed by α-helices (27.79%) and β-sheets (21.88%). The AlphaFold tool generated the most reliable 3D structure model compared to other tools, including SWISS-Model, Phyre2, I-TASSER, and trRosetta. This protein model was validated using PROCHECK, ERRAT, and Verify 3D. Analysis of protein–protein interactions identified aspartate carbamoyltransferase as a major partner (confidence score: 0.999). Functional analysis using CD Search identified L-hydantoinase and allantoinase as conserved domains (E-value equal to 0). To assess the biotechnological potential of this enzyme, molecular docking was performed. Interesting results were obtained regarding the degradation of herbicides, with the best result observed for Nicosulfuron, which exhibited a binding energy of -8.2 kcal/mol, highlighting its potential for bioremediation applications. However, these findings are computational and require experimental validation.Item Etude phytochimique et évaluation des activités antioxydante et antibactérienne des extraits de Orobanche aegyptiaca Pers.(Faculté des Sciences de la Nature et de Vie et Sciences de la Terre, Université de Ghardaia, 2026) KIOUAS, Zineb; MOUSSA, SabrinaOrobanche aegyptiaca Pers. is a medicinal holoparasitic plant belonging to the Orobanchaceae family, commonly known by the vernacular name “El-Danone” and widely used in traditional medicine. The aim of this work is to carry out a phytochemical study and to evaluate the antioxidant and antibacterial activities of the plant extracts. The extraction of bioactive compounds from the aerial parts of the plant was performed using Soxhlet extraction with two solvents of different polarities: methanol and hexane yielding 21.04% and 1.56% for the methanolic and hexanic extracts, respectively. Quantitative analysis of total polyphenols, carried out using the Folin–Ciocalteu method, and flavonoids, determined by the aluminum chloride (AlCl₃) method, showed that the methanolic extract was the richest in phenolic compounds, with contents of 169.81 ± 3.18 µg GAE/mg extract for polyphenols and 11.64 ± 0.86 µg QE/mg extract for flavonoids. The in vitro antioxidant activity of the extracts was evaluated using four methods: total antioxidant capacity (TAC), DPPH and ABTS radical scavenging assays, and reducing power assay. The results demonstrated that the methanolic extract possessed a good antioxidant capacity (TAC = 197.81 ± 2.04 µg AAE/mg extract). In addition, this extract exhibited significant free radical scavenging activity against DPPH and ABTS radicals, with IC₅₀ values of 36.77 ± 0.96 µg/mL and 30.07 ± 2.10 µg/mL, respectively. It also showed a good reducing power with an A 0,5 value of 220.55 ± 3.03 µg/mL. The antibacterial activity was evaluated using the microdilution method in liquid medium on microplates. The obtained results showed that the methanolic extract exhibited greater antibacterial activity than the hexanic extract. The most sensitive bacterial strain was Escherichia coli, with MIC and MBC values of 31.25 mg/mL and 62.5 mg/mL, respectively. In conclusion, these results support the traditional use of this plant and open up prospects for future therapeutic applications.Item Étude in silico de la fluoroacétate déhalogénase d’Actinoalloteichus hoggarensis(Faculté des Sciences de la Nature et de la Vie et les Sciences de la Terre, Université de Ghardaïa, 2026) ABAYAHIA, Ikrame; ZERGOUN, SaraPer- and polyfluoroalkyl substances (PFAS) are persistent and widespread fluorinated organic pollutants that require the development of advanced remediation methods. The fluoroacetate dehalogenase from Actinoalloteichus hoggarensis is a promising microbial enzyme for the defluorination of these compounds. It is involved in the dehalogenation of fluoroacetate by breaking the strong carbon–fluorine (C–F) covalent bond via an SN2-type reaction mechanism, leading to the formation of glycolate. This enzyme was the subject of an in silico study aimed at characterizing its structural and functional properties. Analysis of the physicochemical properties of the protein sequence indicates that it is an acidic, thermostable, and hydrophobic protein. Furthermore, subcellular localization analysis suggests a cytoplasmic protein. The prediction of the secondary structure, performed using the SOPMA and PSIPRED tools, reveals a predominance of α-helices over β-sheets, with an estimated proportion of 43.49%. The three-dimensional structure of the enzyme, predicted by homology modeling using the SWISS-MODEL server, exhibits the highest structural quality compared to other servers. It was subsequently validated using the PROCHECK, ERRAT, and Verify3D tools. Furthermore, analysis performed with MOTIF Finder identified three domains characteristic of the α/β hydrolase superfamily. Molecular docking also allowed us to estimate the interaction energy with perfluorooctanesulfonic acid (PFOS) at −7.2 kcal/mol (Vina score), thereby predicting the enzyme’s potential to interact with the selected ligands. These results provide an important theoretical basis for elucidating the reaction mechanism of fluoroacetate dehalogenase as well as for engineering improved enzyme variants.Item In silico study of the anti-amylase activity of certain metabolites derived from marine organisms(Faculty of Natural Sciences, Life and Earth Sciences, University of Ghardaia, 2026) TFYECHE , Yousra; TIRICHINE, SanaDiabetes mellitus is a prevalent chronic metabolic disorder characterized by persistent hyperglycemia resulting from impaired insulin secretion or reduced insulin activity in target tissues, which prevents the efficient utilization and storage of glucose. Although several antidiabetic medications are currently available, their adverse effects continue to limit therapeutic effectiveness. In this context, inhibition of human pancreatic α-amylase (HPA), a key enzyme involved in carbohydrate digestion, represents an important therapeutic strategy for the management of Type 2 Diabetes Mellitus (T2DM). The present study adopted a stepwise in silico strategy aimed at identifying safe and potent HPA inhibitors from marine-derived secondary metabolites. Initially, an extensive literature survey was conducted to collect compounds previously extracted, purified, and chemically characterized from marine organisms. The selected molecules were then subjected to safety filtering based on cardiotoxicity and carcinogenicity predictions in order to retain only safe compounds. Subsequently, the remaining safe candidates were evaluated through molecular docking against HPA using AutoDock Vina, while interaction analysis and visualization were performed with Discovery Studio Visualizer. The results revealed that several marine metabolites display strong binding affinity toward the catalytic site of HPA and exhibit favorable pharmacokinetic and safety profiles. Among them, Mol7, Mol22, and Mol23, derived from Aspergillus and Streptomyces species, demonstrated the highest inhibitory potential with binding energies of - 10.0 kcal/mol and -9.5 kcal/mol, respectively. Importantly, all selected compounds showed stronger binding affinities than the reference inhibitor acarbose (-7.9 kcal/mol). These findings highlight the potential of marine-derived secondary metabolites as promising candidates for the development of novel HPA inhibitors for the treatment of T2DM. Nevertheless, further in vitro and in vivo studies are required to validate these computational predictions.Item Étude des traits morphologiques, des caractéristiques nutritionnelles et phytochimiques, ainsi que l’évaluation de l’activité antioxydante des graines de Vigna unguiculata (L.) Walp.(Faculté des Sciences de la Nature et de la Vie et Sciences de la Terre, Université de Ghardaia, 2026) YAHIA MalikaVigna unguiculata (L.) Walp., commonly known as cowpea, is a leguminous plant whose seeds are widely consumed due to their nutritional value and biological properties. The present study aimed to investigate the morphological, biometric, nutritional, and phytochemical characteristics, as well as the antioxidant activity, of two cowpea seed varieties: black and white. Morphological analysis showed that both varieties exhibited an oblong or D-shaped form with a smooth and shiny surface. Biometric measurements revealed differences in seed width, sphericity index, and weight, with the white variety displaying the highest values. Nutritional composition analysis indicated that black seeds contained higher levels of proteins (28.91%), lipids (1.14%), carbohydrates (58.61%), and ash (3.34%) than white seeds. Soxhlet extraction using 85% aqueous methanol provided the highest extraction yields, particularly for black seeds (3.92%), whereas hexane extracts showed lower yields (<1.2%). Colorimetric analysis revealed that methanolic extracts were the richest in polyphenols and flavonoids. The highest concentrations were recorded in the methanolic extract of black seeds, with 128.04 µg GAE/mg extract of total polyphenols and 5.37 µg QE/mg extract of total flavonoids. The antioxidant activity of the extracts was evaluated using several assays, including total antioxidant capacity (TAC), DPPH, ABTS, and FRAP. The results demonstrated that the methanolic extract of black seeds (BSME) exhibited the strongest antioxidant activity, with a TAC value of 169.80 ± 1.08 µg AAE/mg extract. Moreover, BSME showed a strong free-radical scavenging activity against DPPH and ABTS radicals, with IC₅₀ values of 58.89 µg/mL and 494.57 ± 13.34 µg/mL, respectively. Furthermore, the FRAP assay revealed a greater reducing power for methanolic extracts, particularly BSME, which exhibited an A₀.₅ value of 451.72 ± 13.02 µg/mL. In conclusion, the findings highlight the nutritional and therapeutic potential of Vigna unguiculata (L.) Walp. seeds, especially the black variety, which is distinguished by its higher content of bioactive compounds and its remarkable antioxidant activity.Item Effet de la méthode d’extraction aqueuse « macération et décoction » sur les différents composés et l'activité antioxydante des cladodes de l'Opuntia ficus-indica de la région de Ghardaïa(Faculté Science de la Nature et de la Vie et Sciences de la Terre - Université de Ghardaïa, 2025) HOUDJEDJE, Asma; BAAMMOUR CHIKH, HananThe young cladodes of Opuntia ficus-indica, consumed as a vegetable, are a valuable source of bioactive compounds and nutrients, and are the subject of our study on their antioxidant activity and nutritional value by analyzing primary and secondary metabolites as well as mineral content. Moisture content, phytochemical composition, mineral analysis, and quantitative determinations: primary metabolites, total polyphenols, total flavonoids, and antioxidant capacity were carried out following established experimental protocols on the dry matter and/or the two aqueous extracts prepared by maceration (Ex M) and decoction (Ex D). The results revealed the presence of flavonoids, polyphenols, alkaloids, free quinones, tannins, terpenes, and reducing compounds, while anthraquinones and saponins were absent. Nutritional analysis showed moisture, fiber, lipid, and ash contents of 92 ± 0,03%, 7,135 ± 0,3%, 1,763 %, and 26,69 ± 0,37%, respectively. Protein content was higher in the maceration extract (14,46 ± 0,01%) than in the decoction extract (10,02 ± 0,02%). Carbohydrates were 56.47% in the dry powder, 49.65% in Ex D, and 55.66% in Ex M. The energy value was low in fresh material (22 kcal/100 g), while the dry matter extracts were much more energetic (273–281 kcal/100 g DM). Total polyphenols and flavonoids were also more abundant in the maceration extract (53,53 ± 0,04 μg GAE/mg and 150,4 ± 0,03 μg RE/mg, respectively) than in the decoction extract. The maceration extract also contained higher levels of minerals, particularly Zn²⁺, Mg²⁺, P, Ca²⁺, and K⁺. Antioxidant activity assessed by the DPPH assay showed a strong IC₅₀, comparable to ascorbic acid, with 42,731 ± 0,46 mg/ml for the maceration extract and 49,643 ± 1,9 mg/ml for the decoction extract. Total antioxidant activity was 35,08 ± 0,06 μg AAE/mg for Ex M and 30,9 ± 0,00 μg AAE/mg for Ex D. According to our study, higher extraction temperatures have a negative impact on the levels of secondary metabolites and nutritional compounds in the aqueous extracts of the cladodes, consequently reducing their antioxidant activity.