ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

Optimization of indole-3-acetic acid production by Brevibacillus borstelensis UMM1 using Box–Behnken Design and artificial neural network modeling: impact on early growth of Oryza sativa

Uday M. Muddapur, Sakshi Kiran, Aejaz Abdullatif Khan, Aparna Shenvi, Ibrahim Ahmed Shaikh, Salah Dafallah, Basheerahmed Abdulaziz Mannasaheb, Sunil S. More, Basim H. Asghar, and Syed Mohammad Shakeel Iqubal

Department of Biotechnology, KLE Technological University, Vidyanagar, Hubballi, India

E-mail: aejaz@ibnsina.edu.sa

Received: 10 May 2025  Accepted: 1 September 2025

Abstract:

This study aimed to optimize environmental and nutritional conditions for maximum indole-3-acetic acid (IAA) production by a bacterial isolate using Box–Behnken Design (BBD) and evaluate its effect on early growth parameters of Oryza sativa (O. sativa) (rice paddy). Soil isolates were initially screened for IAA production and other plant growth-promoting traits, with isolate UMM1 showing the highest IAA potential. A one-factor-at-a-time (OFAT) approach identified key parameters—carbon source, nitrogen source, and tryptophan concentration—affecting IAA synthesis. Subsequent BBD optimization revealed that dextrose as carbon source, NaNO₃ as nitrogen source, 2-day incubation at 37°C, and varying tryptophan concentrations significantly enhanced IAA production in UMM1. TLC and HPLC analysis confirmed the identity and quality of the synthesized IAA. Greenhouse trials demonstrated that inoculation with UMM1 significantly improved vegetative growth of rice seedlings compared to controls. Molecular characterization by 16S rRNA sequencing identified UMM1 as Brevibacillus borstelensis (B. borstelensis) (PV426447) correlating IAA production with this species. The optimal conditions for maximum indole-3-acetic acid (IAA) production (89.46 μg/ml) were determined as follows: 1 g/ml tryptophan, an incubation period of 2 days, 1.5 g/ml dextrose, 0.4 g/L NaNO₃, and a temperature of 37 °C. These results confirm that BBD is an effective methodology for optimizing bacterial IAA synthesis. Additionally, they underscore the potential of B. borstelensis UMM1 as a bioinoculant for sustainable crop enhancement, which may reduce dependence on chemical fertilizers. This research provides valuable insights into bacterial optimization strategies for agricultural applications aimed at environmental sustainability.

Keywords: Brevibacillus borstelensis; PGB; Indole-3-acetic acid; Response surface methodology (RSM); Paddy crops

Full paper is available at www.springerlink.com.

DOI: 10.1007/s11696-025-04362-4

Chemical Papers 79 (12) 8935–8954 (2025)