Optimization and production of salicylic acid by rhizobacterial strain <italic>Bacillus licheniformis </italic> MML2501

Abstract

The Rhizobacterial isolate Bacillus licheniformis MML2501 effectively inhibited the mycelial growth of fungal pathogens viz., Macrophomina phaseolina, Fusarium udum, Fusarium oxysporum, Bipolaris oryzae, Pyricularia oryzae, Alternaria alternata and Curvularia lunata. Bacillus licheniformis MML2501 was tolerant to heavy metals such as zinc, cobalt and selenium. B. licheniformis MML2501 was tolerant to fungicides such as propiconazole and tridemorph and showed moderate tolerance to tricyclazole and it was showed resistant to antibiotics such as ampicillin, streptomycin, bacitracin, cephalotitin, erythromycin and oxytetracycline. Bacillus licheniformis MML2501 produced salicylic acid (SA), with a maximum yield of 18 µg/ml in optimized culture conditions such as pH 7.0, temperature 30°C, casaminoacids at a concentration of 0.4 % and at 200 rpm shaken condition. SA produced by Bacillus licheniformis MML2501 was further confirmed by TLC and HPLC analyses, in which the Rf value and retention time of 0.61 and 5.24 min, respectively were matching with that of authentic SA. Therefore the present study suggests that the rhizobacterial strain Bacillus licheniformis MML2501 has merits to be a beneficial bacteria for the crop protection through systemic resistance.