In this study, the agitation and aeration rates were found to have
relationships with foam formation and surfactin enrichment. A maximum surfactin concentration
of 4.7 g/l of foam was obtained after 21 h of culture with an agitation rate of 150 rpm and
an aeration rate of 1 vvm in fed-batch culture. By controlling the foam overflow rate (fout) of
a fed-batch culture, surfactin concentration in the foam was continuously maintained above
4 g/l.