Enzymatic Activity of Actinomycetes Isolated from the Soil of the Public Landfill of Lifoula (Republic of Congo)

Actinomycetes are Gram-positive filamentous bacteria that have colonized even the most hostile ecosystems. To date, they remain the main source of secondary metabolites and are currently at the origin of the development of several fields such as medical biology, pharmacology and ecology. This work aimed at the characterization of actinomycetes isolated from the soil of the public landfill of Lifoula (Brazzaville); with a view to the possible discovery of rare strains or strains with high enzymatic production potential for industrial use. Soil samples were taken from 2 different points of the landfill, between 5 and 10 cm deep. Inoculation on specific media was followed by enumeration, isolation, phenotypic identification of isolates and enzyme production using an agar well technique. The results showed loads of 70 and 73.30 x 104CFU/g on starch-casein medium compared to 53.30 and 56.60 x 104CFU/g on starch-casein enriched with yeast extract for samples 1 and 2, respectively. 20 isolates were recovered including 9 purified isolates: 6 isolates from sample 1 and 3 from sample 2. The skim milk clotting test was positive for 8 isolates and negative for isolate A2. Enzyme production diameters were amylase, 20 mm for isolates A1 and A7 compared to 14 mm for A4, A9 and A10; proteases, 38 to 50 mm for isolates A1, A2, A7 and A8 compared to 19 mm for A3, A4 and A6 and no production in A9 and A10; Cellulase, 20 mm for A3, A4, A6, A7, A8 and A10 compared to 15 mm for A1, A2 and A9; Lipases 30 mm for A6, A9 and A10 compared to 20 mm for A1, A2 and A8 and 15 mm for A3 and A4. These results suggest that the soil of the Lifoula landfill is rich in enzyme-producing actinomycetes, which can be used in a number of fields, including the food, textile and pharmaceutical industries.