RAPID SCREENING OF LEUCONOSTOC-MESENTEROIDES MUTANTS FOR ELEVATED PROPORTIONS OF ALTERNAN TO DEXTRAN

Certain isolates of the bacterium Leuconostoc mesenteroides, such as s train NRRL B-1355, have been found to produce alternan, a polysacchari de with unique properties of potentially high commercial value. Howeve r, all of these isolates also produce significant amounts of the polys accharide dextran, which would be costly to separate from alternan on a commercial basis. We developed a rapid screening method for the isol ation of L. mesenteroides mutants that produce elevated proportions of alternan to dextran. With this technique, a set of mutants of strain NRRL B-1355 was isolated, including strain NRRL B-21138, which produce d a high proportion of alternan to dextran and showed complete genetic stability after more than 60 generations.