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The strain ICA 8001 from Bradyrhizobium elkanii is broadly used in Cuba for soybean inoculant production. One culture medium designed to multiply this microorganism contains molasses and aqueous soybean extract, which are elements of a variable composition and origin providing considerable amounts of carbonated substrates. Therefore, concentrations of total soluble carbohydrates and reducing carbohydrates as well as N, P, K, Ca, Mg and Na contents were determined, to get a partial nutritional characterization of these components. Analyses showed substantial quantities of these bacterium-absorbing elements within cell growth. The influence of molasses and aqueous soybean extract concentrations on the specific strain growth rate μ (h-1) was estimated by varying molasses concentrations in Bradyfact medium from 3 to 20 g.L-1 and aqueous soybean extract from 5 to 20 g.L-1. Growth dynamics were recorded for each variant, besides calculating μ. Results proved that higher than 10 and 12,5 g.L-1 molasses and aqueous soybean extract concentrations, respectively, inhibit Bradyrhizobium elkanii ICA 8001 growth. This phenomenon could be mathematically and physiologically explained through two new kinetic models. This research work contributes to Bradyrhizobium physiological knowledge, since it makes evident the relationship between culture medium composition and microorganism nutritional requirements, also how culture medium design may ensure more effective inoculants containing high cell concentrations. [ABSTRACT FROM AUTHOR]

Lipo-chitooligosaccharides produced by rhizobia are a class of signalling molecules mediating nodule recognition and organogenesis in the Rhizobium--leguminous symbiosis. Their synthesis is determined by rhizobiumnodulating genes; therefore, they are commonly known as Nod factors. This review is a compilation of updated information on some general topics, as Rhizobium-leguminous interaction signals, nod factor structure, as well as their role in symbiosis. Besides, a research view about this subject in Cuba is presented, describing results related to the design and optimization of culture media with nod factor inducers, with quorum sensing, with nod factor anti-stress effect, with the use of nod factor synthesis-induced inoculants and other oligosaccharines, and with the possible beneficial effect of the latter ones on bacterium-leguminous symbiosis. [ABSTRACT FROM AUTHOR]

Culture media constitute the world of microorganisms under laboratory conditions, trying to simulate their natural habitat to satisfy their most vital needs as living beings. The design of a culture medium responds to demands of the microorganism in question and to the objective pursued with its multiplication; therefore, the selection of nutrients and their appropriate concentrations is a greatly important factor. However, the employment of an appropriate methodology makes possible the obtaining of an optimum culture medium, either for growth and/or metabolite production. Numerous methods and designs of optimization exist with dissimilar characteristics, advantages and limitations that determine their use in diverse branches of investigation. The complete and fractional factorial designs, Plackett Burman, Box-Behnken and the uniform designs were approached in the work. The optimization of medium components and environmental conditions guarantees remarkable yield increments of fermentative processes in a quick and economic way. Therefore, this review seeks to approach the principles and methods of optimization, as well as characterize and exemplify the application of most used designs in culture media optimization, with the objective of extending their use to agricultural biotechonology. [ABSTRACT FROM AUTHOR]

Cells need a source of energy carbon and other nutrients to grow in nature or under laboratory conditions. They also require adequate oxygen concentration, temperature and pH conditions. In this work, the behaviour of two Bradyrhizobium elkanii strains in different culture media, was studied. Different cell multiplication dynamics were evident to each strain under those culture media, as a result of its nutrient composition. Modified propagation medium was notable for both strains studied. [ABSTRACT FROM AUTHOR]