Resistance to Heavy Metals and Enzymatic Production of Actinomycetes and Micromycetes Isolated from Soils of Lifoula and Dolisie Landfills (Republic of Congo)

Heavy metals are a cause of concern worldwide due to their negative effects in soils. This work aimed to study the growth and enzymatic production of actinomycetes and micromycetes in heavy metal-polluted soils from public dumps in Lifoula and Dolisie (Republic of Congo). The soil samples were sterilely taken from a depth of 5 to 10 cm and stored in the refrigerator at 4°C. Isolation, purification and identification were carried out on ELAL and PDA media after heat treatment of the samples at 60°C for 60 mn ; resistance to heavy metals by the growth test on ELAL and PDA media enriched with Lead (Pb), Copper (Cu), Zinc (Zn), Nickel (Ni), Chromium (Cr) and Tin (Sn), and production enzymatic on LB medium. The results obtained revealed that all actinomycete isolates belonged to the genus Streptomyces and mycelial isolates to the genera Penicillium (C1L and C1D), Aspergillus (C2L and C3D), Rhisopus (C2D) and Rhizomucor (C4D). Heavy metal resistance revealed that isolate A1L (Streptomyces sp.) was resistant to Pb, Cu and Sn ; isolate A1D (Streptomyces sp.) was tested for Pb and Ni ; isolate A3D (Streptomyces sp) with Pb, Ni and Sn. Isolates C1L (Penicillium sp.), C2D (Rhizopus sp.) and C3D (Aspergillus sp.) were the most resistant to all heavy metals with inhibition percentages less than 40%. Out of 11 isolates tested, 7 isolates (A1L, A2L, C1L, C2L, C1D, C2D, C3D) produced protease : 3 cm in diameter for isolate C1L. All isolates degraded tween 80 ; produces amylase and cellulase : 3 cm in diameter for C1D and C1L isolates and lipases with 2 cm for C4D. These results show that the soils of the Lifoula and Dolisie landfills contain microorganisms resistant to heavy metals and producers of enzymes. These isolates can be used in waste management and bioremediation of environments polluted by agri-food effluents.