Effect of Bacillus subtilis on some biochemical parameters of long-leaved mint and medicinal melissa under hydroponic cultivation

The aim of the study is to evaluate the effect of Bacillus subtilis rhizobacteria (strains 10-4 and 26D) on some biochemical parameters of Mentha longifolia L. and Melissa officinalis L. grown hydroponically in closed agroecosystems. For the first time, the content of 20 amino acids was analyzed for lemon balm and long-leaved mint under hydroponic cultivation conditions and with B. subtilis inoculation. Strain 10-4 effec-tively enhanced the synthesis of most essential amino acids in lemon balm and long-leaved mint leaves, with the exception of methionine (Met), the content of which was at the control level; strain 26D increased the accumulation of essential amino acids Lys, Val, Trp (for both crops), His (for mint), Phe, Leu+Ile, Thr (for lemon balm). Bacterial inoculation also contributed to an increase in the content of replaceable amino acids (Arg, Tyr, Pro, Ser, Ala, Gly, Cys-Cys). A significant increase in the level of most amino acids was found in plants treated with B. subtilis 10-4, with the exception of glutamic acid + glutamine (Glu + Gln) in long-leaved mint and lemon balm, as well as aspartic acid + asparagine (Asp + Asn) in long-leaved mint. In particular, an increase in the content of potassium and phosphorus in plants was observed, which had a positive effect on their growth and development. Moreover, a significant increase in the yield of essential oils was noted: when using strain 10-4, the yield of essential oil increased by 68 % for mint and by 121 % for lemon balm. It is important to note that inoculation with B. subtilis also contributed to a decrease in the level of nitrates in plant materials, which indicated the effective conversion of nitrate nitrogen into ammo-nium. The use of B. subtilis can be an effective technique for optimizing the nutritional properties of essen-tial oil crops, which is of interest to agronomy and the food industry.