Conversion of cassava starch to trehalose by Saccharomycopsis fibuligera A11 and purification of trehalose

As one of the non-food crops, cassava is widely cultivated in some of the southern provinces of China as a source of starchy material for food and fermentation industry. In this study, cassava starch was used as the substrate for Saccharomycopsis fibuligera A11, a trehalose poor-assimilating mutant isolated from S. fibuligera sdu through chemical mutagenesis, to accumulate trehalose. The results indicated that trehalose accumulation by S. fibuligera A11 was optimal in the medium comprised of 20.0 g/l cassava starch, 20.0 g/l hydrolysate of soybean cake at pH 5.5 and 30 °C for 48 h. At the flask level, trehalose yield was 24.8 g per 100 g of cell dry weight. At the end of 2-l fermentation, trehalose yield was 25.8 g per 100 g of cell dry weight. This is the highest trehalose yield accumulated in the yeast cells reported so far. At the same time, 0.12 g/100 ml of reducing sugar and 0.21 g/100 ml of total sugar were observed in the fermented medium. After isolation and purification, the crystal trehalose was obtained from the culture extract.