Bioproduction of Ascorbic Acid in Root Nodule and Root of the Legume Pulse Phaseolus mungo

The root nodules of Phaseolus mungo (L.), a herbaceous leguminous pulse, contain high amounts of ascorbic acid (AsA). A glucose pool present in the nodule might serve as precursor for AsA production. From root nodule, a Rhizobium sp. was isolated. The symbiont produced a large amount of AsA (290.5 μg/ml) from glucose-supplemented basal medium. The production of AsA by the symbiont was much greater than that of the control when the glucose (0.5%)-supplemented mineral medium was enriched with thiamine hydrochloride (20 μg/100 ml), biotin (20 μg/100 ml), and L-asparagine (0.2%). The possible role of the rhizobial production of AsA on rhizobia–legume symbiosis is discussed.