Various Brazilian soil samples were seeded in agar plates and several strains of antifungal antibiotic producing actinomycetes were isolated. Antibiotic biosynthesis elicitation media were developed and methods for determination of yields were studied. A total of 41 antifungal antibiotic producing strains of aerobic actinomycetes resulted. Among the antibiotics produced, 11 (26.8%) were grouped as macrolide tetraenes, 13 (31.7%) as pentaenes, 1 (2.4%) as oxo pentaene, 1 (2.4%) as hexaene and 6 (14.6%) as heptaenes. Several of these strains also produced antibacterial antibiotics, like polyether antibiotics. The remaining 9 active strains (21.9%) produced non polyene type of antifungals. A medium based on soybean milk favored extraordinarily the elicitation of polyenes biosynthesis by some native strains, while with other strains, this was not favored, while with others it was detrimental. The yields reached about 6,000 polyene units per mL. High polyene type antifungals producing actinomycetes were frequently isolated.
Antifungal antibiotics; Polyenes; Screening Brazilian Soils
