Optimization of mosquitocidal toxins production by Lysinibacillus sphaericus under solid state fermentation using statistical experimental design

摘要

Taguchi’s experimental design of surface response methodology was applied tooptimize the culture medium conditions for Lysinibacillus sphaericus (Ls) mosquitocidal toxinsproduction under solid state fermentation (SSF). The predicted results of this design revealedthat the optimum culture medium conditions for the maximum mosquitocidal activity againstsecond instar Culex pipiens larvae were: 3.08 ± 0.05% substrate concentration, 33 ± 1.5% moisturecontent, 7.8 ± 0.1 initial pH, 1.35 ± 0.15% (5.7 × 107 CFU) inoculum size and 5.9 ± 0.2 daysincubation period. Sporulation titer of Lysinibacillus sphaericus (Ls 14N1) and mortality percentageof second instar Culex pipiens larvae of the fermented culture under these conditions were2.8 × 1010 CFU/g fermented culture and 97.5 ± 1%, respectively. The results of practical validationof the design were incomparable with the mathematical results. Sporulation titer was 2.7 × 1010CFU/g fermented culture; LC50 was 2.8 × 10-5 final fermented culture dilution and toxin proteinconcentration was 2.24 mg/g fermented culture.