Isolation of Indole Acetic Acid (IAA) producing Bacillus siamensis from peat and optimization of the culture conditions for maximum IAA production

Abstract

Indole acetic acid (IAA) is a phytohormone which one of the important compounds for plant growth and development, affecting as inducing cell elongation, cell enlargement and cell division. IAA synthesized both in the plants and microorganisms. For microorganisms, production of phytohormone IAA is one of the essential criteria for plant growth promotion. The aim of the present study was to isolate and screen IAA producing bacteria from peat land area in West Kalimantan and optimized some culture conditions for maximum IAA production. The production of IAA was determined in TSB and YEMB liquid medium and the optimization of IAA production in culture media was carried out at different of incubation time, L-Tryptophan concentrations, carbon and nitrogen sources, pH and temperature. The result revealed that maximum IAA production of Bacillus siamensis was achieved at 96 hours of incubation. The YEMB medium supplemented with 250 ppm of tryptophan was obtained as the best medium for IAA production (9.89 μg/ml). This bacterium produced optimum levels of IAA in the presence of sucrose (10.23 μg/ml) and tryptone (16.61 μg/ml) as carbon and nitrogen sources respectively. In the physical parameters, the maximum production of IAA was recorded at T 35°C (8.42 μg/ml) and a pH of 8.0 (13.29 μg/ml).