http://depot.umc.edu.dz/handle/123456789/5050 2026-05-01T04:46:46Z http://depot.umc.edu.dz/handle/123456789/14734 Production de protéases thermostables par des moisissures thermophiles isolées à partir de sources thermales terrestres de l’Est algérien. Talhi, Imen; Dehimat, Laid The exploitation of the different samples collected from terrestrial thermal springs distributed between the wilayas of Guelma, Khenchela and Mila made it possible to obtain 53 thermophilic fungal isolates. A screening on agar medium based on skimmed milk showed that 23 isolates have a proteolytic activity, of which four (1, 6, 34 and 37) among them are considered as potential producers of proteases, were retained. The isolate 37 was selected for the rest of the work due to the thermostability of its proteases. Molecular characterization by PCR, using the ITS1/ITS4 primer, has shown that isolate 37 has a 99% similarity with Mycothermus thermophilus. The sequence of the amplification product has been deposited in the Gen-Bank database (NCBI) under accession number MK770356. The production of proteases in solid culture was much higher than in both liquid and submerged cultures. Various agro-food wastes were initially explored for the production of thermostable proteases at a lower cost, including wheat bran which proved to be the best substrate for better enzyme production. In addition, a statistical approach consisting of two designs was used to determine the optimal culture conditions allowing the greatest production of these enzymes. The use of the Plackett-Burman plan made it possible to screen the variables; temperature, spore concentration and humidity which have the most significant effect on protease production. Box-Behnken analysis showed a 6.17-fold improvement in protease production (1187.03 U/mL). This improvement was observed under the optimum conditions of 47% moisture content, 5 × 105 spores/g inoculum concentration and temperature of 42°C. The zymography technique demonstrated that the selected strain produced four proteases. These proteases are very active over a wide pH range of 8.0 to 12.0 with an optimum of activity at pH 9.0, at an optimum temperature of 60°C and they retained more than 60% of their activity at the same temperature after heat treatment for 90 min. Likewise, these thermostable alkaline proteases showed great stability towards nonionic surfactants and oxidizing agents, after a pre-incubation of 1 h at 40°C, and extreme stability towards surfactants anionic. The extracted enzymes showed excellent stability and compatibility with some commercial laundry detergents. The results of the washing performance analysis revealed considerable removal of stains from human blood and egg yolk by the enzyme extract. The eco-friendly raw protease hair removal treatment of cow and goat skin has shown very high levels of hair removal. The protein hydrolysates as well as the chitosan resulting from the valorization of shrimp waste by the proteases of the studied strain, showed an important biological activity. Finally, the purification report shows that the protease was purified with a yield of 1.73%, a purification factor of 1.027 and a specific activity of 3124.53 U/mg. Characterization of the partially purified enzyme reveals a pH of 9 and an optimum temperature of 60°C. 2023-03-18T00:00:00Z http://depot.umc.edu.dz/handle/123456789/13435 Capacité des actinobactéries isolées à partir des stations d’épuration des eaux usées ainsi que Labrys portucalensis F11 à dégrader certains pesticides. Boufercha, Oumeima; Boudemagh, Allaoueddine In this study, physico-chemical analysis was conducted to evaluate the functionality and quality of effluent from the wastewater treatment plant (WWTP) of Ibn Ziad, Oued El Athmania and Sidi Merouane. The physico-chemical results revealed that the effluents of wastewater at the outlet of the three WWTPs were loading with lower organic matter than the inlet. From the samples of raw, treated wastewater and from the aeration basins of these WWTPs, 15 strains of actinobacteria were isolated and purified. On the basis of morphological, physiological and biochemical characteristics, combined with phylogenetic analysis of the 16S RNAr gene; 13 isolates were affiliated to the genus Streptomyces sp., one to the genus Actinomadura sp. and another isolate to Micrococcus sp. Preliminary screening of these strains on minimum agar media separately supplemented with 17 different pesticides resulted in the selection of 13 strains capable of degrading 9 different pesticides as the sole carbon source. Secondary screening on minimum liquid medium allowed us to evaluate the degradation kinetics of the pesticides 2,4-dichlorophenol (2,4-DCP) and thiamethoxam by the selected actinobacteria strains. Streptomyces sp. ML and OV were considered as the most efficient strains for the degradation of these two pesticides. In this work we also studied the biodegradation of thiamethoxam by the bacterial strain Labrys portucalensis F11. The results show that this strain can degrade 41%, 35% and 100% of thiamethoxam (10,84 mg/L) as sole source of carbon-nitrogen, carbon-sulfur and carbon, respectively after 30 days of incubation. Periodic feeding with sodium acetate resulted in faster degradation of thiamethoxam. Detection and identification of biodegradation intermediates were performed by UPLCQTOF/MS/MS and the chemical structure of 12 metabolites was proposed. Degradation of thiamethoxam by strain F11 is achieved mainly by dechlorination reactions, nitrate reduction and oxadiazine ring cleavage. The impact of thiamethoxam and its degradation intermediates on the germination of Lactuca sativa, the bioluminescence of Vibrio fescheri as well as on the Toxi-Chromo assay showed that L .portucalensis F11 efficiently degrades thiamethoxam to non-toxic metabolites. The present work demonstrates that actinobacteria and L .portucalensis F11 can be used effectively for the detoxification of such sites contaminated by these pesticides. 2022-07-13T00:00:00Z http://depot.umc.edu.dz/handle/123456789/5108 Etude de la biodiversité des actinobactéries dans quelques eaux thermales de la région Est de l’Algérie. Medjemadj, Maissa; Boudemagh, Allaoueddine The presence and biodiversity of Actinobacteria in four Algerian hot springs was explored using water samples from four thermal springs located in northeastern Algeria. Twenty-three morphologically distinct isolates were isolated and identified. Analysis of the 16S rRNA sequences showed that the isolates were assigned to the Streptomycetaceae, Nocardiaceae and Microbacteriaceae families, the majority being affiliated to the genus Streptomyces. The metabolic diversity of the strains was also explored using the api® galleries (BioMérieux). From the batch of isolated actinobacteria, 4 actinobacteria were selected and studied further. This characterization concerns spore morphology by electron microscopic examination, tolerance to different pH and sodium chloride concentrations, growth at different temperatures and G+C content and chemotaxonomy. The in-depth study revealed that these strains are thermotolerant, halotolerant bacteria and prefer an alkaline pH. The G+C content of these strains is quite low and ranges from 41% to 66%. Their cell walls are type I and their phospholipid profiles are type PII. The characteristic cellular fatty acids detected are AnteisoC15: 0, Iso-C15: 0, Iso-C16: 0, Anteiso-C17: 0 and Iso-C17: 0.The menaquinones present mainly are MK-9 (H6) and MK-9 (H8). These strains have several enzymes which are biotechnologicaly very interesting, such as cellulases, xylanases, lipases and proteases. The antimicrobial activity of these 4 strains was carried out against 6 bacteria and 2 filamentous fungi. These facultative thermophiles actinobacteria are capable of producing antagonist antibiotic compounds against at least one test bacteria studied. 2021-12-16T00:00:00Z http://depot.umc.edu.dz/handle/123456789/5107 Criblage des souches d’actinobactéries pour leurs pouvoirs PGPR; Essais in vitro et in planta sur Solanum lycopersicum L., Triticum durum Desf., et Daucus carota L. Djebaili, Rihab; Kitouni, Mahmoud; Del Gallo, Maddalena Abiotic stress due to climate change and phytopathogens attacks lead to several damages in agricultural crops. Excessive use of chemicals in agriculture causes environmental pollution and loss of agricultural lands with fertile soils. Plant growth-promoting bacteria (PGPB) are an alternative strategy for sustainable agriculture. Among PGPBs, actinomycetes have recently gained increasing attention for their ability to alleviate plant stress and improve agricultural productivity. This study aimed to select actinomycetes strains with plant growth promoting traits, their plantroots association capacities, and their biostimulating effects without and with salt stress as well as the biocontrol power against several fungal and bacterial plant pathogens. The strains were studied for their phosphate solubilization capacity, indole-3-acetic acid (IAA), hydrocyanic acid (HCN), and ammonia (NH3) production, and several enzymatic activities. Bacteria-root associations were studied by scanning electron microscopy (SEM), and a greenhouse experiment was performed to assess the inoculation effects on Solanum lycopersiumL.. Likewise, these strains were tested for in vitro halotolerant ability by several PGP tests with different salt concentrations (i.e., 0, 0.25, 0.5, 0.75, 1, 1.25, and 1.5 M NaCl) and by a greenhouse experiment on Triticum durum. The presence of 1-aminocyclopropane-1-carboxylate deaminase activity was also studied. Moreover, the strains were screened for their in vitro biocontrol activity by soluble and volatile compounds production against the fungal strains Fusarium oxysporum f. sp. radicis-lycopersici (FORL) and Rhizoctonia solani (RHS). The post-interaction events fungus-PGPB were analyzed by scanning electron microscopy. The antibacterial activity was evaluated against Pseudomonassyringae, Pseudomonas corrugata, Pseudomonas syringaepv. actinidiae, and Pectobacteriumcarotovorum subsp. carotovorum. Strains showing good in vitro biological control activities were studied for their antifungal and antibacterial activity using the cell culture filtrate (CFS). The consortium of potent strain was applied on Solanum lycopersicum L. and Daucus carota L. for in planta biocontrol activity. Among sixty actinomycetes, fourteen strains exhibited plant growth promoting characteristics. These strains were able to solubilize the phosphate, produce ammonia, and showed several enzymatic activities at different rates. The scanning electron microscopy revealed a good in vitro plant root association and colonization abilities. The actinomycetes inoculation influenced positively the tomato growth parameters. These strains exhibited important in vitro PGP traits under different salt concentrations. Most strains (86%) had 1-aminocyclopropane-1-carboxylate deaminase activity with significant amounts of ketobutyric acid. In the greenhouse experiment, inoculation with actinomycetes strainsimproved the durum wheat morpho-biochemical parameters, which recorded a significantly higher content of chlorophyll and proline than those of uninoculated controls both under normal and stressed conditions. Strains H12 (Streptomyces albidoflavus) and H14 (Nocardiopsisaegyptica) showed good in vitro antifungal activity with diffusible and volatile compounds (inhibition up to 85%) and antibacterial activity (diameter of inhibition> 10 mm). SEM micrographs showed morphological deterioration of the fungal filaments and changes in their structures. The CFS of potent strains was also active in fungal and bacterial pathogens inhibition (minimum inhibitory concentration up to 0.2%). The consortium was also able to alleviate the infection symptoms and allow a normal growth of the infected plants compared to the control. The obtained results demonstrate the efficacy of halotolerant actinomycetes strains as a biofertilizer and biocontrol agent for plant diseases management and for the alleviation of negative effects of salt stress in plants. 2021-11-11T00:00:00Z