Abstract:

In order to obtain safe and reliable new biological preservatives, Bacillus subtilis PNG27 fermented food
was used to improve its antibacterial activity. Skim milk powder and tomato juice as well as incubation temperature
and time were identified as key medium components and fermentation conditions by one-factor-at-a-time and Plackett-
Burman experimental designs. A Box-Behnken response surface methodology was used to determine the optimal medium
composition and fermentation conditions as 16.0 g/L wheat flour, 20.0 g/L skim milk powder, 200.0 mL/L soybean meal
hydrolysate, 40.0 mL/L tomato juice, 10.0 g/L NaCl, 50.0 mL of medium in a 250-mL triangular flask, and incubation
at 32.14 ℃ for 60.0 h. The maximum model-predicted diameter of the inhibition zone of the fermented broth under the
optimized conditions was increased by 42% for Pseudomonas fluorescens and by 47% for Bacillus pumilus compared with
those observed before the optimization.

Key words: B. subtilis, antibacterial activity, fermentation, soybean flour hydrolysate, optimization