Production and optimization of indole-3-actic acid by rhodopseudomonas palustris

Abstract

Indole-3-acetic acid (IAA) is known to be an important phytohormone that helps to regulate plant growth and development. In this study, the optimum culture medium for the production of IAA by Rhodopseusomonaspalustris in shake flask culture was studied. Rhodopseudomonaspalustris is a purple non-sulfurbacteria which has been well recognised as one of the most metabolitically versatile bacteria. The research was divided into three parts. First, a pre-screening process based on Taguchi Design was conducted to identify the significant factors that could affect the production of IAA. The pre-screening indicated that three parameters were found to be significant, which include the concentration of tryptophan, glucose and potassium nitrate. These parameters were selected and used to optimize the production IAA by Response Surface Methodology (RSM). Lastly, a kinetic study for the bacterial growth and IAA production was investigated. The optimal amount of IAA was obtained after incubation of 48 hours at 35 °C in the presence of 5 g L-1 of tryptophan, 4.94 g L-1 of glucose and 0.60 g L-1 of KNO3, as recommended by the RSM. Under this condition, the experimental yield of IAA production was 80.77? 2.13 µg mL-1, which was in close agreement with the value predicted by the RSM model (77.64 µg mL-1). This was the highest yield of IAA that was reported compared to the IAA yields obtained from the 20 experiments designed under the RSM. The IAA production depends on growth stage as most of the IAA was produced during the stationary growth phase of Rhodopseudomonaspalustris. This study has successfully optimized the production of IAA by Rhodopseudomonaspalustris by statistical approach and proved that Rhodopaeudomonaspalustris has the potential to be used as plant bioenhancer or biofertiliser for plant growth development.