ABSTRACT
Bacillus subtilis RB14 is a strain that exhibits suppressibility against several plant pathogens in vitro and in vivo by producing lipopeptide antibiotics iturin and surfactin. A genetic locus that conferred the ability to produce surfactin was cloned from RB14 and reduced in size in B. subtilis MI113 in this laboratory. Surfactin is the most effective biosurfactant so far, and as such may have many potential industrial applications, which include uses related to oil recovery, emulsion stabilization, extra. Biosurfactants provide an advantage over synthetic surfactants because most are biodegradable and generally less toxic. Plasmid stability of the recombinant strain at different temperatures of main cultivation was evaluated by replica plating in both Solid-State Fermentation and Submerged Fermentation (SmF). In SmF, the nutrients and oxygen are homogeneously distributed in the liquid medium, and this accelerates the growth of the cells rather than production of surfactin as a secondary metabolite.
