Mboukou Kimbatsa Irène Marie Cecile^{1, 2}, Ignoumba Evariste Mesmin^{1, 3}, Gatsé Elgie Viennechie^{1, 3}, Nkounkou Bendo Yvestha Hanselme^{1, 3}, Morabandza Cyr Jonas^{1, 2,}

The influence of temperature, pH and NaCl on the growth and antimicrobial activity of nine (09) actinomycete isolates from the soil of the Lifoula landfill site was studied. The growth and antimicrobial production of the isolates was carried out on LB medium previously inoculated with pathogenic strains of E. coli, S. aureus and A. niger as a function of temperature, pH and NaCl concentration. The results showed that from the 9 isolates, 7 isolates (A1, A2, A3, A6, A7, A9 and A10) or 77.77% produced biosurfactants: 91.66% for A1 and 25% for A2 versus 0% for A4 and A8. Isolates A6, A7 and A9 showed significant antimicrobial activity, with growth inhibition between 11 and 21mm: A7 at 15, 20 and 16mm; A6 at 13 and 11 and A9 at 21, 11 and 12mm diameter for E. coli, S. aureus and A. niger respectively. Maximum growth pH for A6, A7 and A9 isolates was 9, while maximum antimicrobial production pH was 7. Maximum growth temperatures were 25 and 45°C for A6 and A9 versus 45°C for A7; maximum antimicrobial production temperatures were 37°C for A6 and A9 versus 25°C for A7. The maximum NaCl content for growth of all three isolates was 0%, and for antimicrobial production 0.5% for A6 and A9 versus 0% for A7. Extraction of biosurfactants, antibiotics and antifungals indicate that isolates A6, A7 and A9 are producers of antimicrobials inhibiting the growth of E. coli; S. aureus; A. niger, with isolate A9 showing greater performance in inhibiting the growth of target microorganisms. The use of actinomycetes could represent an alternative in the fight against antibiotic resistance.

Actinomycetes, antimicrobial, LB medium, soil, pathogenic strain