Optimizing Carbon/Nitrogen Ratio for Biosurfactant Production by a Bacillus subtilis Strain
R. R. FONSECA,1 A. J. R. SILVA,2 F. P. DE FRANÇA,1 V. L. CARDOSO,3 AND E. F. C. SÉRVULO*,1
Abstract
A Bacillus subtilis strain isolated from contaminated soil from a refinery
has been screened for biosurfactant production in crystal sugar (sucrose)
with different nitrogen sources (NaNO3, (NH4)2SO4, urea, and residual
brewery yeast). The highest reduction in surface tension was achieved
with a 48-h fermentation of crystal sugar and ammonium nitrate.
Optimization of carbon/nitrogen ratio (3, 9, and 15) and agitation rate (50,
150, and 250 rpm) for biosurfactant production was carried out using complete
factorial design and response surface analysis. The condition of C/N
3 and 250 rpm allowed the maximum increase in surface activity of biosurfactant.
A suitable model has been developed, having presented great
accordance experimental data. Preliminary characterization of the bioproduct
suggested it to be a lipopeptide with some isomers differing from
those of a commercial surfactin.
Index Entries: Biosurfactant/production; crystal sugar; lipopeptide; surfaceactive substances; surfactin; Bacillus subtilis.
