Statistical optimization for improved indole-3-acetic acid (iaa) production by Pseudomonas aeruginosa and demonstration of enhanced plant growth promotion

The present study was undertaken to study the statistical optimization of medium components for improved Indole-3acetic acid (IAA) production by Pseudomonas aeruginosa. Colorimetric analysis showed maximum IAA (132 μg mL-1) in the medium supplemented with tryptophan (0.5 g L-1). The maximum production was achieved after 96 h of incubation. Yeast extract, tryptophan and EDTA were identified as significant components influencing IAA production by Pseudomonas aeruginosa, using the PlackettBurman method. The statistical optimization approach led to the production of 318 μg mL-1 of IAA within 24 h of incubation. Statistical approach was found to be very effective in optimizing the medium components in a manageable number of experimental runs with overall 2.4 fold increase in IAA production. TLC and GCMS analysis further confirmed the IAA production in the cell filtrates of the strain. GC-MS analysis and tryptophan side chain oxidase confirmed the existence of atleast 2 possible pathways for IAA by this strain. Inoculation of P. aeruginosa culture filtrate enhanced seed germination (82.4%) and increase in root length and shoot length (~ 2.6 and ~ 1.1 folds over the control) of cowpea seeds over the control treatment under pot culture conditions.