Plant growth promoting rhizobacteria (PGPR) are a specific group of multifunctional bacteria interacting beneficially with plants. They help to improve soil quality, promote crop growth, and sustain soil health. Among the known PGPRs, the Azospirillum, Azotobacter, Pseudomonas have been highlighted in both growth promotion and control of diseases. Ensuring the stability of the microorganism during production, formulation, distribution and storage has been a challenge for these species. In this context, the objective of this work was to develop liquid formulations, through a simplified process, that allows increase in the shelf life of these rhizobacteria for commercial application. The liquid formulation of efficient PGPR was prepared in sterilized liquid manure matkha khaad with the addition of four protective substances glycerol (2%), polyethylene glycol [PEG – 400 1%], polyvinylpyrrolidone-30 [PVP 1 %], and trehalose (1%), and their capacities for maintaining cell viability during storage in low, medium, and high temperature and pH ranges were evaluated. Trehalose (1 %) was chosen as a potential additive because it could maintain a relatively high population and conferred greater microbial vitality under various storage conditions matkha khaad is considered a safe, low-cost, and easy-to-process material, and this formulation would facilitate the practical use of PGPR in agriculture.
