Resumen

GOMEZ, Gretel; NAPOLES, María C; NUNEZ, R  y  MARTINEZ, J. Influencia de la concentración de melaza y extracto acuoso de soya sobre la velocidad específica de crecimiento de Bradyrhizobium elkanii ICA 8001. cultrop [online]. 2008, vol.29, n.4, pp. 21-26. ISSN 0258-5936.

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 m (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 m. 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

Palabras clave : Bradyrhizobium elkanii; molasses; seed extracts; soybean; inhibition; growth; models.