Two-step mutagenesis of Pullularia pullulans leading to clones producing pure pullulan with high yield

A wild strain of Pullularia pullulans, producing, under test conditions, 3 g l-1 of exopolysaccharide (pullulan) contaminated with melanin pigments, was mutagenized by UV irradiation to yield a clone producing white, uncolored product. UV irradiation of this clone gave new clones producing pure pullulan with high yield (about 10 g l-1 under test conditions and about 70 g l-1 under optimized conditions).