The effect of aeration conditions, characterized by the volumetric mass transfer coefficient KLa, on the fermentation kinetics of Bacillus thuringiensis kurstaki

• Published in: Journal of biotechnology 2015-09, Vol.210, p.100-106
• Main Authors: Mounsef, Jihane Rahbani, Salameh, Dominique, Louka, Nicolas, Brandam, Cedric, Lteif, Roger
• Format: Article
• Language: English
• Subjects: Aeration; Bacillus thuringiensis; Chemical and Process Engineering; Chemical engineering; Chemical Sciences; Engineering Sciences; Kinetics; KLa
• ISSN: 0168-1656; 1873-4863
• DOI: 10.1016/j.jbiotec.2015.06.387

•Bacillus thuringiensis fermentation kinetic was studied at different KLa values.•The variation curves of QO2max and μaverage had the same allure.•An oxygen limitation period up to 28h did not harm the production.•Linear increase of μaverage was observed as KLa increased between 13.3 and 65.5h−1.•The maximal toxin protein productivity was obtained for KLa of 65.5h−1. The aeration is a key factor for Bacillus thuringiensis growth, sporulation and δ-endotoxins production. The objective of our work was to study the effect of aeration on the fermentation kinetics of Bacillus thuringiensis kurstaki (Btk), cultivated in a cereal milling byproduct (CMB) mono-component medium, in order to improve the δ-endotoxins productivity. Aeration conditions were systematically characterized by the volumetric mass transfer coefficient KLa. In the 6% CMB culture medium, different values of the maximal specific oxygen uptake rate were obtained at different values of KLa. For KLa of 7.2h−1, the growth was inhibited and the sporulation was defective. There was a linear increase of the average specific growth rate and faster sporulation and liberation of spores and δ-endotoxins crystals when KLa was increased between 13.3h−1 and 65.5h−1. Similar kinetic was observed in cultures performed at KLa equal to 65.5h−1 and 106.2h−1. The highest toxins productivity of 96.1mgL−1h−1 was obtained in the 9% CMB culture medium for KLa of 102h−1. It was possible to track the evolution of the bacterial cells between vegetative growth, sporulation and liberation of mature spores by following the variation of the CO2 percent in the effluent gas.