Effect of tryptophane on synthesis of certain exometabolites by bacteria of genus Acinetobacter, Nocardia, Rhodococcus and their properties

Abstract

The study investigated the effect of tryptophan, a precursor of auxin biosynthesis, on the production and properties of exometabolites synthesized by Rhodococcus erythropolis IMV Ac-5017, Acinetobacter calcoaceticus IMV B-7241, and Nocardia vaccinii IMV B-7405. The strains were cultivated on media containing refined or waste sunflower oil, biodiesel waste, or ethanol as carbon sources, with tryptophan added at 300 mg/L. Tryptophan did not significantly affect surfactant production, which remained within 1.50–1.90 g/L, but increased phytohormone production by all three strains. Surfactants synthesized by N. vaccinii IMV B-7405 and R. erythropolis IMV Ac-5017 in the presence of tryptophan demonstrated 2–4-fold higher antimicrobial activity against phytopathogenic bacteria compared with surfactants obtained without the precursor. This enhanced activity was associated with an approximately 1.4-fold increase in NADP⁺-dependent glutamate dehydrogenase activity, an enzyme involved in aminolipid biosynthesis. The results demonstrate the potential of tryptophan supplementation for obtaining complex preparations of microbial surfactants and phytohormones for plant growth stimulation and biocontrol of phytopathogenic bacteria