Trehalose accumulation from cassava starch and release by a highly thermosensitive and permeable mutant of <Emphasis Type="Italic">Saccharomycopsis fibuligera</Emphasis>

Highly thermosensitive and permeable mutants are the mutants from which intracellular contents can be released when they are incubated both in low osmolarity water and at non-permissive temperature (usually 37°C). After mutagenesis by using nitrosoguanidine, a highly thermosensitive and permeable mutant named A11-b was obtained from Saccharomycopsis fibuligera A11-12, a trehalose overproducer in which the acid protease gene has been disrupted. Of the total trehalose, 73.8% was released from the mutant cells suspended in distilled water after they had been treated at 37°C overnight. However, only 10.0% of the total trehalose was released from the cells of S. fibuligera A11-12 treated under the same conditions. The cell volume of the mutant cells suspended in distilled water and treated at 37°C overnight was much bigger than that of S. fibuligera A11-12 treated under the same conditions. The cell growth and trehalose accumulation of the mutant were almost the same as those of S. fibuligera A11-12 during the cultivation at the flask level and in a 5-l fermentor. Both could accumulate around 28.0% (w/w) trehalose from cassava starch. After purification, the trehalose crystal from the aqueous extract of the mutant was obtained.