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Molecules produced by microorganisms such as Bacillus sp are the subject of many studies. Their manifold applications interest a large range of industries. Several components are used in the agro alimentary industry, chemistry and/or pharmaceutical, as the case of lipopeptides. These molecules present emulisifier properties interesting in food production and also in crops protection via the biopesticides production. 
In order to use this molecule in a large scale, its production in reactor must be developed. Lipopeptides production is positively influenced by biofilm production and induces an important foam production. For these reasons, a biofilm reactor seems to be the more suitable. In this kind of reactor, such as the one developed by Q Zune et al., 2017, a biofilm is formed on a support in stainless steel (packing) suspended above the culture medium that recirculates permanently on the packing. However, this kind of reactor is not easily scalable. The output of the support out of the reactor is required for an industrial production in a larger scale. It is the reason why a biofilm reactor equipped with a column containing packings has been developed with the strains B. amyloliquefaciens GA1 in scale down. 

Unfortunately, this biofilm reactor with a tower meets some difficulties. A cellular lysis is observed and thereby, no biofilm is formed on packings. The light emitted by a near infrared spectrometer placed in the system had been initially considered as the trigger of the cellular lysis. And a possible link between light and the phenomenon of programmed cell death had been established via the study of the general stress response and the regulation network of B. subtilis. 

However, before this link had been demonstrated, the implication of the near infrared spectrometer in the phenomenon had been refuted. And the study of possible causes of this problem had been conducted. Different stresses present in the biofilm reactor and leading to the activation of the general stress response of B. subtilis had been studied (temperature and pH variation and nutrients and oxygen limitation). And an analysis of cells retention in column thanks to a compartments model had been carried out. 
These multiple researches have ended up with a biofilm formation thanks to a change of culture medium (MSgg). And, the compartments model has allowed highlighting the influence of air flow in column on cells retention on packings. Nevertheless, the precise cause of the lysis phenomenon observed with the former medium (Optimize medium) remains unknown.

Biofilm reactor, lipopeptides, MSgg, Optimized medium, Bacillus amyloliquefaciens GA1, compartments model, general stress response, programmed cell death --- Sciences du vivant > Biotechnologie