Cultivation of halotolerant bacteria as a basis of the microbial fertilizer “Biotilia”

Abstract

The ability of salt-resistant growth-promoting phosphate-solubilizing Priestia megaterium Cp-1 and nitrogen- fixing Rhodococcus jostii CA-6 strains to grow on the medium containing oil hydrocarbons (0.1 %) as the only carbon and energy source in the presence of heavy metal ions (0.1‒5.0 mmol/l) providing the enhanced viability in soil contaminated with hydrocarbons, heavy metal and sodium chloride was investigated. The optimum nutrient medium was selected for the growth and development of halotolerant strains Rh. jostii CA-6 and P. megaterium Ср-1 comprising as a product of sugar refining – molasses as the carbon source in an amount of 30 g/l (Meynell medium). Application of 48h culture of Rh. jostii СA-6 and 24h culture of P. megaterium Ср-1 for inoculation of the nutrient medium grown at the agitation rate of the shaker (180 ± 10) rpm appears to be the most efficient fermentation method. To reach the titer of viable strains at least 1.0·109 CFU/ml in submerged culture, the most appropriate procedure envisages the introduction of a seed material in an amount of 5 % of nutrient medium volume. Separately cultured strains P. megaterium Cp-1 and Rh. jostii CA-6 – the basic components of the microbial fertilizer “Biotilia” are mixed in the 1:1 ratio and preserve their vital characteristics at an elevated eco-significant level ((1.67‒2.2)·109 CFU/ml) in 3 months of storage in the temperature range of +4– +15 °C.