원문정보
초록
영어
Fluorescent pseudomonads are a group of plant growth promoting rhizobacteria (PGPR) which rigorously colonize roots and provide beneficial effects to plant development. The PGPR have been known to directly enhance plant growth by a variety of mechanisms, namely, fixation of atmospheric nitrogen that is transferred to the plant, production of siderophores that chelate iron and make it available to the plant root, solubilization of minerals such as phosphorus and synthesis of phytohormones. PGPR can also indirectly enhance plant growth via suppression of phytopathogens by a variety of mechanisms. One of the mechanisms includes the ability to produce siderophores that chelate iron and make it unavailable to pathogens. Other desirable features for a potent organism are that it should have the ability to synthesize anti-fungal metabolites, such as the antibiotic 2, 4-diacetylphloroglucinol (DAPG), hydrogen cyanide, and cell‐wall lysing enzymes, which suppress the growth of fungal pathogens. The fluorescent pseudomonad strain R81 is a root colonizing rhizobacteria which promotes the growth of many plants. Its broth containing a hydroxamate‐type siderophore and DAPG was used for preparing bioinoculant formulations for agronomical applications. Talc and aluminum silicate powders were used to develop inorganic carrier‐based formulations of the strain. The formulations of the bioinoculant were able to bring the natural contaminants in the non‐sterile carriers to acceptable limits in the presence of siderophore and DAPG, thus obviating the need of costly three‐time sterilization of the carriers. The shelf‐life of talc powder- and aluminium silicate‐based formulations could also be significantly increased. Glycerol was found to be the best carbon source for enhanced biomass production. Splitting of nitrogen source to NH4Cl and urea had a stabilizing effect on pH during batch cultivation. Both batch and fed batch processes were used for production of bacterial biomass and DAPG. Open loop feeding strategy such as exponential feeding of nutrients and closed loop feedback strategies using dissolved oxygen and pH signals were evaluated for fed‐batch cultivation of the pseudomonad for maximal production of DAPG.