http://depot.umc.edu.dz/handle/123456789/4871 Sun, 31 May 2026 19:58:21 GMT 2026-05-31T19:58:21Z http://depot.umc.edu.dz/handle/123456789/14815 Exploration of Algerian ecosystems for the selection of Actinobacteria belonging to the genus Streptomyces developing potentialities of PGPR and antagonists of wheat phytopathogens Alloun, Wiem; Kacem Chaouche, Noreddine This work aims to isolate Actinobacteria strains with a growth promotion ability and the biocontrol potential of Fusarium culmorum, the wheat root rot-causing fungi. The exploration of terrestrial and aquatic Algerian ecosystems, i.e. the wheat rhizosphere in the Tiffeche region (Souk-Ahras) and the aquatic sediments of Lake Oubeira (El Taref), respectively, resulted in 102 native isolates. Therefore, 37 have morphological and cultural characteristics similar to the genus Streptomyces. These isolates were screened for their plant growth-promoting traits. These activities consist of the production of hydrogen cyanide (HCN), ammonia (NH3), and indole-3- acetic acid (IAA), as well as in vitro antagonism against F. culmorum. Among the auxin family, IAA constitutes a crucial phytohormone regulating specific tropic responses of plants and functions as a chemical signal between host plants and their symbionts. IAA derived from Actinobacteria grown on agricultural waste represents a more economical alternative than its synthetic homologous. Rhizospheric isolate AW 22 was positive for HCN and NH3 production, growth inhibition of F. culmorum with an index of 67.320±8.99% and high IAA content of 23.999±1.126 μg. mL-1 in standard growth conditions on yeast-tryptone broth (YTB) amended with 0.2% (w/v) L-Tryptophan. Thus, the AW22 isolate was selected for a polyphasic chemotaxonomic characterization and the optimization of the production process of this phytohormone. Molecular and phylogenetic analysis identified isolate AW22 as Streptomyces rubrogriseus, and its sequence was deposited in Genbank under accession ID OP176004. Analysis of the putative IAA produced by S. rubrogriseus AW22 on YTB using thin-layer chromatography (TLC) and (HPLC) revealed Rf values equal to 0.69 and a retention time of 3.711 min, equivalent to the authentic IAA. Artificial intelligence-based approaches (i.e. Behnken design from response surface methodology (BBD-RSM) with artificial neural networks (ANNs) coupled with the genetic algorithm (GA)) were employed to bioengineer in vitro and silico a suitable medium for maximum IAA bioproduction. According to the Box Behnken Design matrix, data were based on empirical studies involving the inoculation of AW22 in various cultural conditions and low-cost feedstocks notably, the spent coffee grounds (SCGs). Four input variables comprising L-Trp (X1), incubation T° (X2), initial pH (X3) and SCG concentration (X4) were screened via Plackett-Burman design (PBD) and served as BBD and ANN-GA inputs. The IAA yield constituted the output variable (Y in µg. mL-1). Upon training the model, the optimal conditions suggested by the ANN-GA model were X1= 0.6%, X2= 25.8°C, X3 = 9, X4=30%). An R2 of 99.98%, adding to an MSE of 1.86x10-5 at 129 epochs, postulated higher reliability of the ANN-GA approach in predicting responses, compared with BBD-RSM modeling exhibiting an R2 of 76,28%. Using the process parameters generated by ANN-GA AW 22 achieved a maximum IAA yield of 188.290±0.38 µg. mL-1. This optimization resulted in a 4.55-fold and 4.46- fold increase in IAA secretion after eight days of incubation, corresponding to ANN-GA and BBD-RSM models, respectively. These results confirm the validity of both models in maximizing IAA yield from the multifunctional S. rubrogriseus AW22 isolated for the first time in Algeria. Thu, 20 Jul 2023 00:00:00 GMT http://depot.umc.edu.dz/handle/123456789/14815 2023-07-20T00:00:00Z http://depot.umc.edu.dz/handle/123456789/14813 Recherche de micro-organismes producteurs d’hémi-cellulases à partir de la biomasse lignocellulosique ; valorisation des hémicelluloses dans les domaines des bio-polymères et les fermentations non agroalimentaires. Gares, Maroua; Kacem Chaouche, Noreddine; Evidente, Antonio The main objective of this work is to search for microorganisms capable of degrading lignocellulosic biomass by lignocellulosic enzymes and more particularly, hemicellulase. The exploration of soil samples from two forests and a former landfill in Constantine (Algeria), resulted in the selection of 16 microbial isolates. A single mold isolate (MGA) was selected for its high cellulase and hemicellulase activity. Molecular identification of MGA revealed it to be Aspergillus fumigatus ON226990. The selected strain was subsequently subjected to a scaling-up study to test its ability to grow and produce hemicellulase on a large scale. A. fumigatus showed an ability to grow in a liquid medium based on xylose as substrate, in 250 mL Erlenmeyer flasks, 2 and 20 liter bioreactors. In addition, three shaking speeds: 350, 500 and 650 rpm were tested in the 2 L bioreactor in order to follow the impact of the shear effect on the morphology of A. fumigatus. Indeed, this strain showed a certain ""robustness"" to the shear that can occur on an industrial scale; by increasing the agitation speed to 500 rpm, the mold forms free micro-pellets ensuring a good homogeneity in the culture medium. On the other hand, at agitation speeds lower than 300 rpm, the mycelium develops as macro-pellets. Furthermore, according to HPLC analyses, A. fumigatus showed a very high potential for production of endo-1,4-β-xylanase and xylan 1,4-β xylosidase during using corn xylan as substrate in a 2-L bioreactor fermentation. The production process in liquid medium, remains very expensive because of the high price of pure substrate. Therefore, the interest is redirected to the valorization of Stipa tenacissima (Alfa) as raw material for the production of hemicellulase by A. fumigatus. It is important to emphasize that this work is the first to have exploited Alfa as a raw material for the production of enzymes without pretreatment by A. fumigatus. For this purpose, the polymers of dried and ground esparto samples were analyzed by chemical methods (strong and dilute acid). Indeed, the results obtained by HPLC analysis show that this herb is mainly composed of 46-44% of cellulose and 12.5-13.33% of hemicellulose. On another aspect, experiments were statistically planned with the Box-Behnken design to optimize the production of xylanase and cellulase by A. fumigatus, using Alfa as the only carbon source, where the inputs are; pH, temperature, humidity and incubation time. The optimal conditions established by the response surface method for maximum xylanase production (841.78 U/gds) are: pH; 4.5, temperature; 30 °C, humidity; 89.19% and a fermentation time of 144 h, and for maximum cellulase production (74.41 U/gds): pH; 6, temperature; 31.61 °C, humidity; 90% for 144 h incubation. Subsequently, 11 factors, including organic and inorganic nitrogen sources, carbon and phosphorus sources, were screened using the Plackett-Burman design to investigate their influence on xylanase production. Malt extract, MgSO4, NaNO3 and (NH4)2SO4 were selected for further optimization using the Central-Composite design. The maximum xylanase production under the optimized conditions is 1659.41 U/gds, which represents a nearly 3-fold increase over the first xylanase production before optimization. Furthermore, the enzyme activity produced by A. fumigatus under the optimized conditions, is more efficient than that of commercial enzymes. This enzyme complex also showed its efficiency in the saccharification of Alfa, wheat straw, oat straw and wheat bran, compared to the saccharification of these substrates by commercial hemicellulase. A saccharification rate of 35.82% was observed with wheat bran, oat straw (25.91%), Alfa (21.29%) and wheat straw (2.29%) after 24 h of incubation. Finally, a cost-effectiveness study confirmed the value of xylanase production by A. fumigatus; enzyme production with Alfa is 3 times cheaper than with pure commercial xylan. Mon, 17 Jul 2023 00:00:00 GMT http://depot.umc.edu.dz/handle/123456789/14813 2023-07-17T00:00:00Z http://depot.umc.edu.dz/handle/123456789/14733 Recherche et isolement de microorganismes des milieux extrêmes algériens producteurs de métabolites d’intérêt sur différents substrats agro-industriels pertinents. Djelid, Hadjer; Kacem Chaouche, Noreddine; Flahaut, Sigrid In this study, the cellulolytic activity of bacteria isolated from various locations in an extreme algerian ecosystme was investigated. The salt lake of El M'Ghair was specifically examined (along with its nearby soil and water, as well as a nearby palmeraie). In fact, 9 of the 43 bacterial isolates were able to degrade carboxymethyl-cellulose (CMC) with varying cellulolytic index values. The analysis has shown that the bacterial isolate H1, which was isolated from the soil of a palmeraie near a lake, has the best cellulolytic potential, with a value of 5.5 of CI. The isolate's molecular analysis revealed that it belongs to the species Bacillus velezensis, whose accession numbers to GenBank (NCBI) are OM510337 for the 16S ARN and OM523097 for the gyrA. This strain exhibits optimal growth at 37 °C in 863 broth without NaCl, however, it resisted at 55 °C in the same medium with 10% NaCl, giving rise to its thermotolérance and halotolérance characteristics. The strain was inoculated on a medium containing 5% olive mill wastes (GO), 0.5% yeast extract, and 150 rpm stirring to test its capacity to hydrolyse lignocellulosic material and produce lipopeptides with biosurfactant activity. Indeed, during the 72 hours of fermentation, the olive mill wastes was hydrolyzed by the release of various oligosaccharides due to strain ability to produce a cellulase (CelH1). This degradation also made it possible to produce lipopeptides with surfactant and emulsifying activity. A significant positive correlation of the cellulase and biosurfactants production was observed (77%). The CelH1 enzyme was, then, purified 44.9 folds and recovered with a yield of 80% and a specific activity of 453.04 U/mg of protein, using only two successive steps: ultrafiltration and ion exchange chromatography. Indeed, the molecular mass of the enzyme was estimated at 26 kDa by SDS-PAGE, and its identification by LC-ESI-MS/MS analysis, showed that it covers 40% of the sequence of an endo-1,3-1,4-β-glucanase from family 16 of glycosyl hydrolases. After 48 hours of incubation under test conditions, the enzyme remained stable and displayed optimal enzymatic activity at pH 6.0-6.5 and at 60-65°C. The highest CelH1 activity was measured on barley β-glucan substrate (604.5 U/mL) followed by lichenan and CMC, confirming that the studied enzyme is an endo-1,4-β-glucanase . CelH1 is highly thermotolerant and halotolerant retaining 77% of its activity at 70°C and 70% in the presence of 4 M NaCl. The enzyme has a Vmax of 625 U/min/mL and a high affinity with barley β-glucan with a Km of 0.69 mg/mL. It has also shown a significant ability to release cello-oligosaccharides by hydrolyzing cellopentaose. Lipopeptides produced by B. velezensis H1 are partially purified using a C18 column. HPLC analysis of the lipopeptide extract showed that the B. velezensis H1 strain has the ability to produce at least two lipopeptides: surfactin and fengycin, on the GO-based medium. The biosurfactant and tensioactif potential of these products was demonstrated by a Drop Collapse test using olive oil and paraffin as hydrophobic substrates, a complete collapse of the lipopeptides drop was observed, due to the reduction of surface tension of the hydrophobic substrates under the effect of the lipopeptide extract. Thu, 25 May 2023 00:00:00 GMT http://depot.umc.edu.dz/handle/123456789/14733 2023-05-25T00:00:00Z http://depot.umc.edu.dz/handle/123456789/14219 Recherche et isolement de bactéries du genre Bacillus de différents écosystèmes particuliers algériens Rehamnia, Baraa; Kacem Chaouche, Noreddine; Lee, Natuschka With the discovery of numerous caves on planet Mars and the exploration of different types of caves on Earth, the interest and use of cave microorganisms has increased significantly during the last years. Hence, the purpose of this study is to present the first novel data on the presence of culturable, spore-forming bacteria in 10 different caves in Algeria, at depths down to 450 m. Two hundred fifty spore-forming isolates were obtained and their probiotic potential was tested with different methods (pathogenicity, growth at 37°C, survival in gastric juice and simulated intestinal fluid, antibiotic sensitivity, presence of digestive enzymes such as -galactosidase and gliadinase and cell surface properties). 13 of these tested strains (affiliated either to Bacillus or Paenibacillus, according to 16S rRNA analyses by FISH and gene sequencing) showed a rich spectrum of enzymatic and probiotic potential. These strains and their enzymes may therefore serve as useful candidates for future research in food processing and in reducing the effect of digestive disorders. These findings also suggest that novel strains with biotechnological potential can be discovered in pristine, subsurface ecosystems. Phylogenetic evaluation revealed that all selected isolates are affiliated to different Bacilli taxa within Firmicutes: B.gobiensis, B.subtilis, B.tequilensis, B.zhangzhouensis, B.pumilus, B.megaterium, B.simplex and B.pabuli. Sat, 17 Dec 2022 00:00:00 GMT http://depot.umc.edu.dz/handle/123456789/14219 2022-12-17T00:00:00Z