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 sought 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 and actinomycetes
isolated using serial dilution technique and 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 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 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%. There is
need to carry out structure elucidation of the antibiotics from the selected
actinomycetes.
