Abstract
BACKGROUND: Biosurfactant production was investigated using two strains of Bacillus subtilis, one being a reference strain (B. subtilis 1012) and the other a recombinant of this (B. subtilis W1012) made able to produce the green fluorescent protein (GFP).
RESULTS: Batch cultivations carried out at different initial levels of glucose (G~0~) in the presence of 10 g L^−1^ casein demonstrated that the reference strain was able to release higher levels of biosurfactants in the medium at 5.0≤G~0~≤10 g L^−1^ (B~max~ = 104–110 mg L^−1^). The recombinant strain exhibited slightly lower levels of biosurfactants (B~max~ = 90–104 mg L^−1^) but only at higher glucose concentrations (G~0~ ≥ 20 g L^−1^). Under these nutritional conditions, the fluorescence intensity linked to the production of GFP was shown to be associated with the cell concentration even after achievement of the stationary phase.
CONCLUSION: The ability of the genetically‐modified strain to simultaneously overproduce biosurfactant and GFP even at low biomass concentration makes it an interesting candidate for use as a biological indicator to monitor indirectly the biosurfactant production in bioremediation treatments. Copyright © 2008 Society of Chemical Industry