Impact of foaming on surfactin production by Bacillus subtilis: Implications on the development of integrated in situ foam fractionation removal systems

•Small-scale batch foaming approach to assess the impact of foaming on cellular growth.•Foaming boosted surfactin titers, yields and productivities in B. subtilis.•Joint effect of foaming and glucose-limited conditions in surfactin production.•Stimulation of surfactin production via recycling foamed cells.•Fate of best surfactin producing B. subtilis cells within a foam recovery system.