Improvement of Photorhabdus temperata strain K122 bioinsecticide production by batch and fed-batch fermentations optimization

• Published in: Bioprocess and biosystems engineering 2012-11, Vol.35 (9), p.1505-1513
• Main Authors: Jallouli, Wafa, Jaoua, Samir, Zouari, Nabil
• Format: Article
• Language: English
• Subjects: Agricultural biotechnology; Biological and medical sciences; Biopesticides; Bioreactors; Biotechnology; Chemistry; Chemistry and Materials Science; Dissolved oxygen; Environmental Engineering/Biotechnology; Fermentation; Food Science; Fundamental and applied biological sciences. Psychology; Industrial and Production Engineering; Industrial Chemistry/Chemical Engineering; Insect control; Insecticides; Methods. Procedures. Technologies; Microbial engineering. Fermentation and microbial culture technology; Optimization techniques; Original Paper; Pest Control, Biological - methods; Photorhabdus - growth & development; Photorhabdus temperata
• ISSN: 1615-7591; 1615-7605
• DOI: 10.1007/s00449-012-0740-2

Optimization of a fermentation process for bioinsecticides production by Photorhabdus temperata strain K122 was investigated into fully controlled 3-L fermenter using an optimized medium (OM). Development of large-scale inocula showed that the composition of the growth medium greatly influenced the physiological state of P . temperata cells. The effect of pH, agitation and dissolved oxygen concentration (DO) on the growth, culturability and oral toxicity of P . temperata cells were also investigated. Indeed, maintaining the pH at 7 and controlling DO concentration at 50 % saturation throughout the fermentation process, improved biomass production, CFU counts and oral toxicity by 41.1, 35 and 32.1 %, respectively, as compared to cultures carried out in 500 mL shake flasks. At such conditions, 8 g/L glucose fed-batch fermentation, enhanced cell lysis and variants small colony (Vsm) polymorphism appearance. To overcome such limitations, glucose concentration should be maintained at 4 g/L. In this case, P . temperata cells were produced at high cell density and culturability reaching 4.5 and 1.2 × 10 9  cells/mL, respectively. In addition, the stability of the primary form was maintained for a long period in the stationary growth phase and Vsm polymorphism was completely avoided that can be crucial for scale-up the bioprocess of P. temperata bioinsecticide.