Fig. 1

FT-IR absorption spectra of biosurfactants produced by Bacillus atrophaeus 5-2a from ‘BB’ (a) and ‘BU’ media (b). BB for the fermentation medium used brown sugar, beef extract and peptone as the carbon and nitrogen sources; BU for the optimal medium used brown sugar and inorganic nitrogen urea as the carbon and nitrogen sources. The same as below, unless otherwise specified