Optimisation of a cost-effective culture medium for the large-scale production of Bacillus subtilis UTB96

Abstract

Fermentation optimisation to achieve high biomass and high efficiency of a biocontrol product is millstone in biocontrol sciences. Here, a Placket–Burman design used for comparison and screening of some environmental factors that are effective on bacterial biomass of Bacillus subtilis UTB96. A response surface methodology used to determine the optimal points for three factors including pH, temperature and C/N ratio where the biomass is high. The results of response surface methodology application showed that the optimum conditions for maximum production of biomass in the medium occurs at pH 7, temperature 30 °C and C/N ratio of 23:1. Bacteria derived from optimised conditions either from laboratory or semi-industrial bioreactors, showed a considerable increase in biomass and also, their antagonistic activity against Phytophthora drechsleri in a plate assay. However, optimisation of culture medium in a laboratory bioreactor decreased the antagonistic activity against Aspergillus flavus. Application of the optimised culture medium in both semi-industrial and laboratory bioreactors reduced the length of the lag phase of bacterial growth.