Survival and viability of Bradyrhizobium japonicum in different liquid medium

The microbiological inoculants present on the market come in various formulations and forms. Inoculants used in pre-sowing bacterization of legumes in our country are traditionally prepared on peat as the highest quality carrier of bacteria. However, the requirements of the manufacturer are focused on liquid forms of inoculants. Therefore, the aim of this paper is to determine the optimal composition of the liquid medium that will support the growth of Bradyrhizobium japonicum, the soybean symbiont. Three liquid nutrient medium formulations were included in the study: mannitol-yeast medium, modified mannitol-yeast medium, and glycerol medium stored at two temperatures (4 and 25 °C), and B. japonicum cell viability was determined over 6 months. The results showed that the largest number of rhizobia (on average 4x109 zo 9x108) was obtained on yeast-mannitol medium at 4 °C as well as on modified yeast mannitol medium where their number remained constant throughout the storage time and was 5x107 cfu ml-1 at 25 °C. Further research should include testing other rhizobial protectors in order to increase the number of viable cells in longer time periods.