Effets antimicrobiens de l’extrait hydrométhanolique de Thymus vulgaris (Thym) récolté dans la région de SETIF sur la croissance des germes spécifiques du yaourt : Streptococcus thermophilus et Lactobacillus bulgaricus

Abstract

This study examined the effect of methanol extracts of Thymus vulgaris harvested in the wilaya of Setif in northeastern Algeria on the two specific germs of yoghurt, namely Streptococcus thermophilus and Lactobacillus bulgaricus. The main bioactive compounds Of Thym were extracted by maceration of a sample of the crushed plant material in an aqueous methanol solution. After evaporation in vacuo of the methanol, the extracts obtained were diluted to 20%, 40%, 60%, 80 and 100%. The measurements and controls were carried out in triple tests and concerned the direct contact method, the diffusion method on disks, the CMI and the CMB. The study showed that increasing concentrations of bioactive extracts of thymus vulgaris resulted in strong bacterial activity against Streptococcus thermophilus and Lactobacillus bulgaricus; With inhibition diameters varying from 5.33 to 12.67 mm and from 5.67 to 13.33 mm, with inhibition levels ranging from 26.67 to 63.33% and 32.69 to 76.92% is a microbial growth which varies from 131.67.104 UFC / ml to 128.104 UFC / ml respectively. The minimal inhibitory concentration and the minimum bactericidal concentration are obtained with the thyme extract prepared at 60% for streptococcus thermophilus; the minimal inhibitory concentration for Lactobacillus bulgaricus is obtained with the extract prepared at 80% and the minimum bactericidal concentration observed at 60%. Thus the CMB / CMI ratio is equal to 1 and 0.75 respectively. The methanol extract of Thymus vulgaris of Setif appears to exert a bactericidal effect on the two specific germs of yoghurt Streptococcus thermophilus and Lactobacillus bulgaricus