Caracterização fenotípica e produção de biopolímeros por bactérias isoladas de nódulos de guandu [(Cajanus cajan (L.) Millsp.]. 2009, 166f. / Phenotypic characterization and biopolymers production by bacteria isolated from pigeonpea [Cajanus cajan (L.) Millsp.] root nodules. Seropédica: UFRRJ, 2008. 166p.

Paulo Ivan Fernandes Júnior

The biological nitrogen fixation (BNF) is a natural process carried out by prokaryotes collectively called diazotrophs. Among the diverse microorganisms able to fix the atmospheric nitrogen, stand out those capable of set up mutualistic associations with legume plants in specialized structures called nodules. Thus the search for microorganisms able to establish efficient associations with plants of legume family had been the target of studies for the last decades. In recent years, further the prospecting for microorganisms able to establish efficient associations, the rhizobia have been the target of other biotechnology interests, such as the production of molecules of industrial interest, such as enzymes and biopolymers. These macromolecules are used in various branches of industry and the constant search for microorganisms able to produce new molecules is a source of innovation in these sectors. In this context, the aim of this study was to evaluate the phenotypic diversity of bacterial isolates from root nodules of three pigeonpea genotypes, as well as to evaluate the capacity of these bacterial isolates to produce exopolysaccharides, polyhydroxybutyrate and amylases. Eight soils were sampled four in Seropédica municipality (two samples were from Dystric Udult soils), and two from a Haplic Fragiudult soil), four in Pinheiral municipality (Xanthic Udox soil, Aqult soil, Rhodic Udult, and a Fluvaquent), all in Rio de Janeiro State, to set up a experiment to obtain the bacterial isolates. The experiment was set up at a factorial design of 3 (genotypes) x 8 (soils). The plants were harvest at 75 days after the emergence and the nodulation was evaluated. Five nodules for each plant were superficially disinfected and crushed in Petri dishes with YMA media containing Congo Red stain. After the purification of the bacterial isolates it was proceeded the cultural characterization, and evaluated the capacity of the bacterial strains to grow in culture media containing eight different carbon sources, antibiotics or salts and different temperatures. The isolates were authenticated in greenhouse sterile conditions and an experiment was carried out to evaluate the capacity of selected isolates to establish the symbiosis. The isolates presented a very diverse pattern to present intrinsic resistance to antibiotics and to grow eighth different carbon sources. It was also evaluated the capacity of the isolates to produce polyhydroxybutyrate, exopolysaccharides and amylase. The reology of selected EPS were also evaluated. The majority of isolates tested were able to present growth when incubated at 42C. Part of the isolates was able to grow in culture media with 3% of NaCl. Though 34% of the isolates were not able to nodulate the host plant, and from the isolates evaluated to establish the symbiosis all presented the same nodulation compared with the recommended strains. The isolates varied a lot regarding the production of PHB and EPS, showing strong influence of the carbon source used. The EPS rheology showed pseudoplastic behavior. Regarding the amylase production, one isolate had reached a degradation ha lo 2.7 times the colony size. These results show the biotechnological potential of these isolates, both for inoculants production and biopolymer production.

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