Synthèse: Revue des Sciences et de la Technologie

Évaluation de l’activité antimicrobienne l’huile essentielle de la lavande (Lavandula stoechas)

Manel Lina Djendi — 2024-02-05

La multi-résistance microbienne pose de grands problèmes pour la santé publique. À cet effet, il ne reste que peu d’agents antimicrobiens effectifs contre certains microbes multi-résistants. Ce qui a pour conséquence majeure la recherche de nouveaux produits antimicrobiens. Cette étude vise l’évaluation de l’activité antimicrobienne l’huile essentielle de la Lavandula stoechas largement utilisée en médecine traditionnelle algérienne. Ainsi, des tests de sensibilité sur des microorganismes ont été effectués sur quatre souches bactériennes cliniques multi résistantes (Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, Staphylococcus aureus) et une levure (Candida albicans) en utilisant la technique des disques. Les résultats révèlent que l’huile essentielle extraite à partir des fleurs de Lavandula stoechas exerce une importante activité vis-à-vis d’Escherichia coli, Klebsiella pneumoniae une activité inhibitrice modérée sur la croissance de Pseudomonas aeruginosa et staphylococcus aureus, tandis qu’avec la levure Candida albicans une résistance est observée. Ces résultats démontrent que l’huile essentielle de Lavandula stoechas est une source prometteuse d’agents antimicrobiens, qui peut être adoptée à des fins thérapeutiques.

Diversité et structure des formations végétales de la forêt communautaire d’Alibi-1 au Togo

Atakpama Wouyo — 2024-02-05

Au Togo, l’on assiste ces dernières années à plusieurs initiatives de foresterie communautaire. La présente étude a : (i) évalué la diversité floristique et (ii) caractérisé la structure des formations ligneuses de la forêt communautaire d’Alibi-1 dans la région Centrale du Togo. L’analyse s’est basée 74 relevés floristiques, forestiers et écologiques. La flore recensée comprend 229 espèces appartenant à 166 genres et 51 familles. Les familles les plus diversifiées sont les Fabaceae (42 espèces), Malvaceae (18 espèces) et Poaceae (17 espèces). Cinq (5) groupements de relevés ont été discriminés : deux (2) groupements de savanes arborées/arbustives, deux (2) groupements de forêts claires/savanes boisées et un (1) groupement de forêts galeries/forêts denses sèches. La structure verticale et horizontale des groupements est en « J » renversé et en cloche dissymétrique gauche ressortant une forte représentativité des individus de faibles diamètres et de hauteurs. La densité et la surface terrière des arbres sont les plus élevées s’observent dans les savanes arborées/arbustives et les plus faibles dans les galeries forestières/savanes boisées. Une meilleure gestion de la biodiversité et des écosystèmes de cette forêt contribuera à l’amélioration des biens et services écosystémiques de cette dernière.

English Abstract

In recent years, there have been several community forestry initiatives in recent years in Togo. This study aimed to: (i) assess the diversity of plant species, and (ii) characterize woody plant community structure of in the Alibi-I community forest located in central Togo. Within 74 sample plots, floristic, forestry and ecological inventories were carried out. A total of 229 species were recorded. They belong to 166 genera and 51 families. Fabaceae (42 species), Malvaceae (18 species) and Poaceae (17 species) were the most diversified families. Five groups of plots were discriminated: two groups of wooded/shrub savannahs, two groups of open forest/wooded savannahs, and one group of gallery forest/dense dry forest. The diametric and height structure of the clusters is in the form of an inverted "J" and bell-lef dyssimetric. This shows a relatively high representation of small diameter and tall individuals. Density and basal area of the trees highest values were observed in trees/shrubs savannahs and the lowest in forest galleries/wooded savannahs. Better biodiversity and ecological management in this forest will help to improve its ecological goods and services.

Key words:

Biodiversity, structure, community forest, sustainable management, Togo.

Physiochemical characterization of a biosurfactant produced by bacteria isolated from pharmaceutical process water

Abed Belkacemi — 2024-02-05

The study was performed on samples from pharmaceutical process water. Only strains presumed to produce biosurfactants were selected depending on microbiological analyses. So, the main objective of this investigation was the isolation, identification and characterization of some microorganisms producing biosurfactants. These characteristics were compared with previous references. The capacity and conditions of biosurfactant production were determined via several tests such as the rate of biomass after incubation, pH, surface tension and emulsification index. Four strains have been identified, namely Pseudomonas Spp1, Pseudomonas Spp2, Flavobacterium spp and Serratia liquefaciens. The results obtained showed that the selected bacteria could produce biosurfactants with significant surface properties except for Pseudomonas Spp2. They were characterized in terms of structure, surface tension, emulsification capacity, thermal, and chemical stability. In addition, the emulsifying capacities were found to be very attractive; the best results were obtained for the products extracted from Pseudomonas Spp1, which were equivalent to those obtained from the reference (Bacilllus subtilis). Furthermore, all the biosurfactants have good thermal stability. However, their properties seem to be sensitive to pH; a basic pH leads to a lowering of the surface tension and an increase of the emulsifying capacity. Based on the spectral characteristics, the biosurfactants produced mainly by the isolated strains were found as glycolipid types.

Morphology and sexual dimorphism of the Salema Sarpa salpa (Linnaeus, 1758) on Annaba coasts

Lilia Labiba Groud — 2024-02-05

This work deals with the biometrics of the Salema Sarpa salpa from the coasts of eastern Algeria. Using metric and meristic criteria, the morphology of the species is characterized and compared to other individuals from different localities in the Mediterranean and the Atlantic. The Salema of the Annaba coasts show an isometry of growth of the majority of the metric characters considered (9 out of 16), both in females and in males, but it is not always the same characters. Two characters show sexual morphological dimorphism: the length of the maxilla and the diameter of the eye. Females are said to have a larger maxilla and orbital diameter. Regarding the numerical criteria, we note their greater extent in the Salema of the Annaba coast compared to the other Mediterranean and Atlantic populations studied.

Study of the electrochemical behavior of Al-Zn-In based sacrificial anodes in sea water

H. Ferkous — 2024-02-05

Cathodic protection is one of the most commonly used methods to protect steel structures immersed in seawater. This mode of protection may be used alone or associated with a coating, such as paint systems. This work aims to determine the durability of this protection system. We have studied the sacrificial nature of anodes made from Al-Zn alloy. The different materials used have been subjected to stationary and non-stationary electrochemical tests, especially electrochemical impedance spectroscopy (EIS), which is then characterized by EDX and SEM. In the case of sacrificial anodes, the results have highlighted the conditions of activation and passivation of these anodes, which are of particular industrial interest. A relationship has been established between the functioning of the studied anodes and the nature of the corrosion products. and revealing three areas of resistance and suggesting complex mechanisms for localized corrosion.