Abstract
This study aimed to determine the indole-3-acetic acid (IAA) production capacity of Bacillus subtilis strain ESU181, isolated from the roots of local Einkorn (Triticum monococcum) in Bolu, Türkiye. IAA production was monitored for bacterial cultures with or without L-tryptophan (Trp) supplementation in LB medium under different pH (6.5, 7.5, and 8.5) and temperature (30 °C and 37 °C) levels. Bacterial cultures were incubated for 96 h, and IAA concentrations were determined at 24-hour intervals using Salkowski's method. Among the tested conditions, the highest IAA production (6.936 ± 0.063 µg/mL) was obtained at pH 6.5 and 37 °C after 96 h incubation in LB medium supplemented with Trp. A significant increase in IAA synthesis was reported in Trp-supplemented cultures compared to without Trp-supplemented controls among all conditions (p B. subtilis strain ESU181 has strong IAA-producing capacity under optimized conditions, particularly in the presence of supplemented Trp. The results suggest that this native strain may be leveraged as a promising candidate for biofertilizer development, offering a sustainable strategy to promote plant growth via IAA production.Supplementary information
The online version contains supplementary material available at https://doi.org/10.1007/s13205-026-05083-5.