Screening for Antimicrobial Activity of Bacillus Subtilis and Paenibacillus alvei Isolated from Rotten Apples Compost

New antimicrobial compounds are continuously required to combat antibiotic-resistant bacteria and pathogenic yeast as such resistance increasingly limits the effectiveness of current antimicrobial drugs. New screening approaches, including the search for novel targets and exploration of non-conventional places as sources of producer microorganisms, are needed. Rotten apples compost samples from the composting plant in Resen, Macedonia, were screened for microbial colonies which form a clear zone of inhibition. The isolated bacterial strains were further screened for their antimicrobial activity against different bacteria and fungi by diffusion agar method. The isolates were later identified as Paenibacillus alvei and Bacillus subtilis by morphological studies and sequencing of the 16S rRNA bacterial gene. The maximum growth of P. alvei and B. subtilis for different cultivation media, pH, temperature, time of incubation and glucose concentration were determined. Maximum growth of P. alvei and B. subtilis was observed in MHB, at pH 6 after 24 hours of incubation at 30 °C for P. alvei, and at pH 7 after 48 hours at 40 °C for B. subtilis. In conclusion, the identified strains with antimicrobial activity in this study are a useful addition to the worldwide effort for new antibiotic discovery.