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-3- acetic acid (IAA) production by Pseudomonas aeruginosa. Colorimetric analysis showed maximum IAA (132 ìg 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 Plackett- Burman method. The statistical optimization approach led to the production of 318 ìg 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 GC- MS 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.