Large-Scale Production of Rhizobium meliloti on Whey

Whey, a by-product of the cheese industry, can sustain the growth of fast-growing rhizobia. To avoid any latency of growth, rhizobial inoculum must be prepared under inducing conditions. In unsupplemented whey, the number of cells of Rhizobium meliloti Balsac reached 5 x 10 CFU/ml in 48 h of incubation. This is comparable to the yield obtained with yeast-mannitol broth, the standard medium for the growth of rhizobia. In raw whey supplemented with yeast extract (1.0 g/liter) and phosphate (0.5 g/liter), the number of cells reached 10 CFU/ml in 48 h of incubation. This is a twofold increase compared with the population normally obtained in industrial production. Whey represents a relatively inexpensive and efficient substrate medium for the large-scale production of fast-growing rhizobia.