Isolation and Identification of Potassium Releasing Bacteria from Sugarcane Rhizosphere Soil and Optimization of Fermentation Condition

[Objectives]To isolate and optimize the potassium releasing bacteria from sugarcane rhizosphere soil in Baitu Town, Gaoyao District, Zhaoqing City, Guangdong Province, and then evaluate their potassium-releasing ability, and optimize the fermentation conditions of the strains with the best potassium-releasing ability, so as to provide a scientific basis for the development and production of potassium releasing bacteria fertilizer. [Methods] Potassium-solubilizing bacteria were isolated from sugarcane rhizosphere soil using potassium-feldspar powder as the potassium source of isolation medium by dilution coating method and plate streaking method. The isolated strains were identified by 16s rRNA sequence analysis. The potassium-releasing ability of each strain was determined by sodium tetraphenylborate (STPB) method, and the strain GK-37 with the optimal potassium-releasing ability was selected. The fermentation conditions of GK-37 strain were further optimized, and the effects of different carbon sources on its growth were mainly investigated. [Results] Seven strains of potassium-solubilizing bacteria were isolated and purified, and identified by 16s rRNA. They belonged to Pseudomonas knackmussii, Pseudomonas, Pseudomonas insulaes and Caballeronia zhejiangensis. Among the tested strains, strain GK-37 had the best potassium-releasing ability, and its potassium-releasing capacity was 26.99 mg/L. By optimizing the fermentation conditions of GK-37 strain, it was found that when the fermentation medium was sucrose as carbon source, the growth of the strain was the best. [Conclusions] In this study, the potassium releasing bacteria were successfully isolated and identified from the rhizosphere soil of sugarcane, and the strain GK-37 had high potassium-releasing ability. Through the optimization of fermentation conditions of GK-37 strain, sucrose was determined as the optimal carbon source. This study is expected to provide a valuable reference for the further development and production of potassium releasing bacteria fertilizer.