Amal A. Ali and Wafaa A. Hafez( 2017). Enhancing of polyb-hydroxybutyrate in rhizobium sp. To stimulate plant growth under salt stress84 N. Egypt. J. Microbiol. Vol. 48, September, 2017.
Abstract: Rhizobia store energy in the lipid poly-3-hydroxybutyrate (PHB), which may enhance rhizobium survival when they are carbon limited, either in nodules or in the soil between hosts. In this study, the production of Poly-β-hydroxybutyrate (PHB) was determined in five strains of R.leguminosarum bv. trifolii 100,102,103, 111 and 2128 and the results indicated that the lowest PHB productivity was found in strain 111while the highest PHB productivity was in strain 102 then the effect of different carbon and nitrogen sources on PHB production in these strains was tested. Molasses supported maximum PHB production (1.1 g/ L) followed by glucose (0.61g/ L). Peptone as nitrogen source resulted in higher polymer production of PHB (0.59 g/L). Maximum PHB was obtained at 48 h. Post this incubation time the trend showed a decline in PHB yield. The results of field experiment on clover plants revealed that Chlorophyll, protein and nutrients content increased in case of molasses based inoculant followed by glucose & peptone based inoculants as compared to the control. Maximum fresh and dry yield was recorded in case of molasses based inoculant (42.62, 7.20 tons fed-1) following by glucose & peptone based inoculants (42.15, 7.17 tons fed-1) respectively compared to the control. The results obtained revealed that applying of PHB producing rhizobia led to improve many of soil variables such as, soil pH, EC and NPK concentrations as well as Fe, Mn and Zn contents with superiority for molasses based inoculant and glucose &peptone based inoculants.
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