Production of surfactin and fengycin by Bacillus subtilis in a bubbleless membrane bioreactor
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Surfactin and fengycin are lipopeptide biosurfactants produced by Bacillus subtilis. This work describes for the first time the use of bubbleless bioreactors for the production of these lipopeptides by B. subtilis ATCC 21332 with aeration by a hollow fiber membrane air–liquid contactor to prevent foam formation. Three different configurations were tested: external aeration module made from either polyethersulfone (reactor BB1) or polypropylene (reactor BB2) and a submerged module in polypropylene (reactor BB3). Bacterial growth, glucose consumption, lipopeptide production, and oxygen uptake rate were monitored during the culture in the bioreactors. For all the tested membranes, the bioreactors were of satisfactory bacterial growth and lipopeptide production. In the three configurations, surfactin production related to the culture volume was in the same range: 242, 230, and 188 mg l−1 for BB1, BB2, and BB3, respectively. Interestingly, high differences were observed for fengycin production: 47 mg l−1 for BB1, 207 mg l−1 for BB2, and 393 mg l−1 for BB3. A significant proportion of surfactin was adsorbed on the membranes and reduced the volumetric oxygen mass transfer coefficient. The degree of adsorption depended on both the material and the structure of the membrane and was higher with the submerged polypropylene membrane.
KeywordsBacillus subtilis Surfactin Fengycin Bubbleless membrane bioreactor Oxygen transfer Adsorption
This work received financial support from the Université Lille 1 Sciences et Technologies, the Région Nord-Pas-de-Calais, the Fonds Européen pour le Développement de la Recherche, and the Ministère de l’Enseignement et de la Recherche. We thank Dr. Sylvain Thuaudet from MEDOS for his collaboration and William Everett for the English proof reading.
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