Abstract:
Antibiotic resistance is one of the biggest global problem of our times. The leading producers of antibiotics
that can be used to curb this problem are actinomycetes. This study was conceived to isolate antibiotic
producing actinomycetes from the soils of Menengai crater and identify the cultural and physical factors
that favoured production of antibiotics by selected actinomycetes. Soil samples were collected from 32
randomly selected sampling points within Menengai crater. The actinomycetes were isolated using serial
dilution technique. The actinomycetes were tested for antagonism against selected bacterial and fungal
pathogens using primary and secondary screening bioassays. Based on broad spectrum of activity and the
size of zone of inhibition, four potent actinomycetes were selected for further studies. The effect of growth
media, pH, temperature, incubation period, aeration, inoculum concentration, carbon source, nitrogen
source and salt concentration on growth and production of antibiotic metabolites was determined. The
actinomycetes isolated presented varying morphological characteristics. There was a significant difference
in the diameters of zones of inhibition produced by the test pathogens when subjected to the antibiotic
metabolites from the selected actinomycetes (F = 6.6046 P = 0.001338). The growth and production of
antibiotics by the selected actinomycetes was favoured by use of Luria Bertani as the culture medium, a pH
of 6, incubation temperature of 28oC, incubation period of 7d, aeration rate of 200rpm, inoculum
concentration of 1%, glycerol as carbon source, oat meal as nitrogen source and a salt concentration of
1.5%. The growth and production of antibiotics by the selected actinomycetes is affected by culture
medium, pH, incubation temperature, incubation period, aeration rate, inoculum concentration, carbon
source, nitrogen source and salt concentration. There is need to curry out structure elucidation of the
antibiotics from the selected actinomycetes.
