PLACKETT-BURMAN modeling of Saccharothrix texasensis MB15 IAA production on agricultural wastes
This work aims to the optimization of fermentation conditions by recovering agricultural waste (roots and leaves of wheat) for the biotechnological production of indole-3-acetic acid by strains of actinobacteria. Starting with eighteen actinobacteria strains from the collection of the Laboratory of Biology of Microbial Systems (LBSM, ENS of Kouba); a preliminary screening for the production of AIA was carried out in vitro under standard conditions on YT broth. A second screening of the selected strain Saccharothrix texasensis MB15's ability to produce IAA on a fermentation medium based on agricultural waste (wheat roots and leaves) was accomplished. The PLACKETT-BURMAN matrix was then used to build a mathematical and experimental optimization design of 11 in vitro fermentation conditions factors.
The results indicates that Saccharothrix texasensis strain MB15 is the best IAA producing strain. The strain MB15 is able to produce IAA on a medium based on the roots and leaves of wheat only. The optimal values for the modulating factors tested for maximum IAA production are: L-tryptophan 1.25 (g / L), initial microbial charge 5.106 (spore / L) and extract of wheat leaves at 50% w/v. The maximum IAA production of strain MB 15 was 140.5 μg / ml. Only thirty-five experiments were needed to assess the effect of 11 factors. The fit of the model was very good with an R2 = 0.94; RMSE = 8.798.
This work has shown us the effectiveness of the optimization by the matrixes of PLACKETT-BURMAN in determining the optimal conditions for a large production of IAA.