Optimisation of Potato Dextrose Agar Culture Medium for Actinobacteria Growth

The objective of this study was to optimise the potato dextrose agar (PDA) culture medium in terms of its potential for use in the growth of actinobacteria. The strain used in this study was a species of actinobacteria previously identified as Streptosporangium sp. (P1C3), characterised by slow growth (20 days of incubation), low aerial mycelium production, and no pigment production. To determine the optimal formulation, the Streptosporangium sp. (P1C3) strain was tested for incubation time and aerial mycelium growth across 27 formulations based on the PDA culture medium. A central composite rotational design (CCRD) experimental methodology was employed, where glucose concentration (g/L), yeast extract concentration (g/L), pH, and temperature were tested. Among the tested formulations, 01, 05, 09, and 13 showed a reduction in incubation time and complete aerial mycelium growth, which was linearly influenced by the four tested variables. Response surface analysis indicated that the optimal values for promoting aerial mycelium growth in the shortest incubation time were 10 g/L glucose concentration, from 1 g/L to 3 g/L yeast extract concentration, pH levels between 5.7 and 7.2, and temperatures between 24 °C and 32 °C. The optimisation of the PDA medium proved effective in improving the isolation of actinobacteria and enhancing the production of metabolites with potential antimicrobial activity.