Optimization of Indole 3-acetic acid (IAA) production by Acetobacter diazotrophicus Ll isolated from Sugarcane

Based on morphological, cultural and biochemical characteristics, a newly isolated bacterium from the stem of the Indian sugarcane variety Co 740 was identified as Acetobacter diazotrophicus and was designated as L1. Cultural and nutritional conditions were optimized for indole 3-acetic acid (IAA) production. The effect of increasing sucrose concentration and different nitrogen sources on IAA production were studied. Shaking increased the production of IAA. The isolate produced high amount of IAA (26.28 μg/ml) when basal medium (pH 6) was supplemented with sucrose (12% w/v), yeast extract (0.05 g/l), L-tryptophan (1.2 g/l) and NH₄Cl (0.1% w/v) at 200 rpm. IAA production increased up to 2.6 fold over control. Inoculation with A. diazotrophicus Ll increased root and shoot biomass as well as IAA level of the fresh root tissue of maize plant. The results indicated that A. diazotrophicus Ll produced high amount of IAA than reported earlier.