Developing Production Methods for Different Microbial Strains and Beneficial Testing on Crop Species

  • Linah Y. Alghanmi

Student thesis: Master's Thesis


Microorganisms will play a significant role in the agricultural revolution in the coming decades and help meet the growing population's needs. Hence, understanding the impact of beneficial bacteria on crop development is key to the future of developing microbial products. The ability of PGPB to increase crop yields has been recently investigated in agriculture, as PGPB can support and protect plants under different stresses. Since PGPB interactions occur naturally, finding a method to apply beneficial bacteria while maintaining their efficiency and quality is a topic of interest. PGPB have been used as microbial inoculants, biofertilizers, and also as seed coatings. Preservation of microorganisms through desiccation has been used as the preferred method for long-term storage of microbial culture. The use of dry powders is favored over liquid cultures due to their ease of transportation and better quality control. For microbial preservation, freeze-drying has been defined as the most convenient and satisfactory preservation method for long-term storage. Freeze-drying is generally preferred over other drying techniques as it gives a high-quality dehydrated product. However, to reach a high-quality product, many parameters need to be monitored, such as bacterial cell concentration, growth medium, lyophilization buffer, rehydration, and duration of freeze-drying. In this research, SA190 was freeze-dried with 10% sucrose mixed with 5% trehalose as lyophilization buffer. Pseudomonas argentinensis SA190 was isolated from the root nodules of the desert plant Indigofera argentae in Saudi Arabia, specifically Jizan. The SA190 freeze-dried product was examined by several tests to assess the product viability and quality, such as accelerated test and water stability test. For future work, the effect of freeze-dried SA190 on plant growth and crop yield will be investigated. Moreover, optimization of the freeze-drying process, formulation, and packaging for commercial will be considered. In addition, bacterial strains isolated in DARWIN21 project with promising effects on plant growth, will be subjected to freeze-drying process.
Date of AwardJul 2021
Original languageEnglish (US)
Awarding Institution
  • Biological, Environmental Sciences and Engineering
SupervisorHeribert Hirt (Supervisor)


  • Freeze-drying
  • beneficial bacteria
  • plant-growth promoting bacteria
  • microbial preservation
  • lyophilization
  • Pseudomonas argentinensis

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