INDOLE-3-ACETIC ACID PRODUCTION BY GEL-ENTRAPPED BACILLUS THURINGIENSIS IN THE PRESENCE OF ROCK PHOSPHATE ORE

Abstract

Bacillus thuringiensis in entrapped in k-carrageenan was capable of producing indole-3-acetic acid (IAA) in the presence of rock phosphate ore (RPO). After five repeated batch fermentation experiments, an average of 6.9 mg/L IAA was recorded in the presence of 1.5 g/L RPO and 4.7 mg/L IAA in the RPO-free control. The bacterium simultaneously solubilized phosphates with a maximum soluble P of 115 mg/L and 150 mg/L after the fourth batch cycle in 1.5 and 3.0 g/L RPO amendment, respectively. Addition of tryptophan to the media increased IAA production to 13.9 and 20.7 mg/L per batch on RPO-free and 1.5 g/L RPO-supplemented media with poor bacterial growth and RPO solubilization.

Keywords:

• Bacillus thuringiensis
• Batch fermentation
• Gel entrapment
• IAA production
• Phosphate solubilization

Acknowledgments

This work was supported by the COST Action 865, R&C and CTM2005- 06955 (MEC-Spain).

Notes

Results represent average of three replicates (average ± standard deviation).

Results represent average of three replicates (average ± standard deviation).

Tryptophan was amended at 0.01% concentration. Results represent average of three replicates (average ± standard deviation).