Extracellular polysaccharide production by a Rhizobium sp. isolated from legume herb Crotalaria saltiana Andr.

Abstract

A symbiont, isolated from root nodules of Crotalaria saltiana Andr., was identified as Rhizobium sp. It produced large amount of extracellular polysaccharides (EPS) in broth culture in yeast extract mannitol (YEM) medium. The EPS production and growth started simultaneously, though they have different stationary phases. The symbiont produced maximum EPS (16 µg/mL) when the medium was supplemented with preferable carbon (glucose) 2%, nitrogen (glycine) 0.1%, and vitamin (biotin) 1 µg/mL. Attempts were made to optimize the cultural requirements for growth and EPS production. The EPS produced by the symbiont contained glucose and galactose. The possible role on Rhizobium root nodule symboiosis has been discussed in the light of EPS production.