Nutritional evaluation of cyanobacterium (Nostoc sp.) extract in Rhizobium cultures

Extracts from Nostoc sp. biomass (CE) were compared with yeast extract (YE) in the formulation of media for cultivation of Rhizobium etli and Bradyrhizobium japonicum. Growth depended on the rhizobium strain and also on the type and concentration of the extract. The growth kinetics of R. etli were substantially influenced by the addition of CE an YE at concentrations between 0.3 and 1% (w/v); cultures containing YE showed shorter lag periods and higher growth rates and those with CE presented higher growth yields. Depending on the extracts, a different behaviour was displayed by the cultures at the stationary phase; cell viability increased or remained fairly constant in cultures developed on CE, and those developed on high concentrations of YE showed a decline in viable cell counts.