title: Overcoming the production limitations of Photorhabdus temperata ssp. temperata strain K122 bioinsecticides in low-cost medium.
abstract: For low-cost production of Photorhabdus temperata ssp. temperata strain K122 bioinsecticide, a cheap complex medium was optimized. Diluted seawater was used as the source of micronutrients, especially sodium chloride, involved in the improvement of cell density, culturability and oral toxicity of the bacterium P. temperata against Ephestia kuehniella larvae. Thus, the new formulated medium was composed only of 10 g/l of soya bean meal, used as the carbon and nitrogen main source, mixed in sevenfold diluted seawater. At such conditions, several limitations of P. temperata bioinsecticide productions were shown to be overcome. The appearance of variants small colony polymorphism was completely avoided. Thus, the strain K122 was maintained at the primary form even after prolonged incubation. Moreover, the viable but nonculturable state was partially overcome, since the ability of P. temperata cells to form colonies on the solid medium was prolonged until 78 h of incubation. In addition, when cultured in the complex medium, P. temperata cells were produced at high cell density of 12 × 10(8) cells/ml and exhibited 81.48% improvement of oral toxicity compared to those produced in the optimized medium. With such medium, the large-scale bioinsecticides production into 3-l fully controlled fermenter improved the total cell counts, CFU counts and oral toxicity by 20, 5.81 and 16.73%, respectively. This should contribute to a significant reduction of production cost of highly potent P. temperata strain K122 cells, useful as a bioinsecticide.
authors.affiliation: Laboratoire de Protection et Amélioration des Plantes Team of Biopesticides, Centre of Biotechnology of Sfax, Sfax University, PO Box 1177, 3018 Sfax, Tunisia.
authors.forename: Wafa
authors.initials: W
authors.lastname: Jallouli
authors.forename: Samir
authors.initials: S
authors.lastname: Jaoua
authors.forename: Nabil
authors.initials: N
authors.lastname: Zouari
mesh_terms: D000284:Administration, Oral; D000818:Animals; D061046:Biological Control Agents; D003470:Culture Media; D007306:Insecticides / Q000138:chemical synthesis / Q000378:metabolism; D007814:Larva / Q000378:metabolism; D007915:Lepidoptera / Q000378:metabolism; D010572:Pest Control, Biological / Q000379:methods*; D020637:Photorhabdus / Q000737:chemistry* / Q000254:growth & development* / Q000472:pathogenicity; D012623:Seawater / Q000737:chemistry; D012965:Sodium Chloride / Q000378:metabolism; D013025:Glycine max / Q000378:metabolism
chemical_list: D061046:Biological Control Agents; D003470:Culture Media; D007306:Insecticides; D012965:Sodium Chloride