The effect of nitrosoguanidine on carotene-synthesizing and pigment-free yeasts

A number of mutants with a demand for amino acids, vitamins and nitrous bases has been obtained under effect of nitrosoguanidine (0.05%) on the yeast Candida utilis and carotene-synthesizing yeast Rhodosporidium diobovatum, Rhodotorula glutinis var. glutinis and Rh. rubra. Concentration of auxotrophs due to the death of prototrophs has been achieved in the studied yeast, with the exception of Rh. rubra using additional treatment by levorin (200 units/ml). When selecting quickly growing mutants of carotene-synthesizing yeast obtained after treatment by nitrosoguanidine, the primary selection by the intensity of red-orange colour of the colonies proved to be more efficient than that by resistance to monoiodoacetic acid. The selected mutants of the pigmented yeast surpassed by primary culture as to the harvest of carotenoids (including beta-carotene) and biomass in the periodic and continuous processes.