Breeding of a mutant of Aureobasidium sp. with high erythritol production

Abstract

An erythritol-producing yeast, Aureobasidium sp. SN-124A, was successively mutated with UV irradiation and NTG treatment. One of the isolated mutants, SN-G42, had superior properties to the wild strain in the following three points. First, SN-G42 did not foam during cultivation while the wild strain foamed severely. This property of the mutant greatly facilitated its cultivation in the fermentor. Second, the mutant produced erythritol with 47.6% yield on a medium containing 22.5% glucose compared to 41.8% yield obtained with the wild strain. Third, the yield in the wild strain declined from 41.8% to 14.2% when the glucose concentration of the medium was increased from 22.5% to 47%. On the contrary, the yield in the mutant decreased only from 47.6% to 37.7% under the same conditions. As a result, the maximum erythritol concentration produced reached 164.8 mg/ml with the mutant while the highest value obtained with the wild strain was 110 mg/ml. These properties of the isolated mutant made it possible to produce erythritol on a commercial scale.