Process Biochemistry 47 (2012) 2020–2024 Contents lists available at SciVerse ScienceDirect Process Biochemistry jo u rn al hom epa ge: www .elsevier.com/locate/procbio Rotating discs bioreactor, a new tool for lipopeptides production Omar Chtioui, Krasimir Dimitrov ∗ , Frédérique Gancel, Pascal Dhulster, Iordan Nikov Laboratoire des Procédés Biologiques, Génie Enzymatique et Microbien (ProBioGEM), UPRES-EA 102, Université Lille Nord de France, Avenue Paul Langevin, 59655 Villeneuve d’Ascq Cedex, France a r t i c l e i n f o Article history: Received 22 May 2012 Received in revised form 29 June 2012 Accepted 10 July 2012 Available online 17 July 2012 Keywords: Rotating discs bioreactor Fengycin Surfactin Lipopeptide Biosurfactant Bacillus subtilis a b s t r a c t Microbial production of two biosurfactants, fengycin and surfactin, by Bacillus subtilis ATCC 21332 in a rotating discs bioreactor was studied. Simultaneous production of these lipopeptides was performed by free and cells immobilized on the surfaces of rotating discs. The aeration applied on surface allowed a non- foaming fermentation process and an important production of lipopeptides for low microbial growth in the culture medium. It was demonstrated that the selectivity of lipopeptides synthesis could be modified varying operating conditions and that the cells immobilization improved greatly fengycin synthesis. The maximal concentration of fengycin and surfactin obtained were 838 mg L -1 and 212 mg L -1 , respectively. The development of this bubble-less process could advance the scale-up of the fermenters for production of biosurfactants. © 2012 Elsevier Ltd. All rights reserved. 1. Introduction Surfactin and fengycin belong to two families of lipopeptides produced by the wild strain Bacillus subtilis ATCC 21332 [1,2]. These biosurfactants molecules represent interest for application in agriculture, petrol industry, pharmaceutical fields and pollution remediation [2,3]. Fengycin is also known as a strong antifungal [4]. The production of lipopeptides by B. subtilis in laboratory biore- actors with bubbling gas supply has been previously studied [2,5–7]. However, serious technical problems arose during lipopep- tide production in such bioreactors, such as an uncontrollable foaming and the necessity of intense cooling or washing processes. The use of chemical anti foams is not suitable because they can affect the physiology of the strain and make difficult the recovery of the pure products [8]. Hence, the extrapolation of these bioreactors to pilot or industrial scale remains still complicated. B. subtilis ATCC 21332 is considered as a strict aerobe. However, it was recently demonstrated that this strain is able to grow and to produce lipopeptides even at oxygen limited conditions [2,9]. Surfactin and fengycin were successfully produced in bubble-less regime, avoiding foam formation, using biofilm on solid carri- ers in a batch culture [1,9], as well as in a laboratory hollow fiber membrane air–liquid contactor [2]. Despite the good lipopep- tide yields obtained using the last technique, its scale-up seems ∗ Corresponding author. Tel.: +33 3 28 76 74 08; fax: +33 3 28 76 73 56. E-mail address: krasimir.dimitrov@polytech-lille.fr (K. Dimitrov). quite problematic. When cells were grown in biofilm conditions, it was found that the synthesis of both lipopeptides and especially fengycin production was greatly enhanced by the immobilization of microorganisms [9]. Biofilms are multi-cellular communities of microorganisms attached to a surface or interface. Bacteria seem to initiate biofilm formation in response to specific environmental cues, such as nutrient and oxygen availability [10]. The transi- tion from free-living organisms to sessile biofilm cells changes the specific production of secondary metabolites and increases cells resistivity. Taking into account the good colonization ability of B. subtilis on solid carriers [9], the aim of present work was to propose a non foaming fermentation process for surfactin and fengycin pro- duction by B. subtilis ATCC 21332 immobilized on the surfaces of rotating discs partially immersed in the fermentation broth. For this purpose a new laboratory scale rotating discs bioreactor was designed. The scale-up of such kind of reactors is relatively easy. In fact, rotating discs bioreactors are widely used in wastewater treat- ment because of their convenience, simple design, relatively low energy consumption, and easy maintenance [11], but their appli- cation for the production of molecules of interest remain still rare [12,13]. In order to advance the industrial production of biosurfactant lipopeptides using wild strains, the main objective of this study was to investigate the production capacity of a rotating discs bioreactor with surface aerated immobilized and planktonic cells of B. sub- tilis ATCC 21332. Another goal was to analyze the selectivity of the fermentation process in this bioreactor. 1359-5113/$ – see front matter © 2012 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.procbio.2012.07.013