| Trehalose (α-D-glucopyranosyl-1-1-α-glucopyranose) is widely present in bacteria, yeasts, and fungi as well as some insects, invertebrates,vertebrates and plants. Recent results have shown that trehalose does not only primarily function as a reserve carbohydrate but also as a highly efficient protectant, enhancing the resistance of cellular components against adverse conditions such as high temperature, starvation, radiation, freezing, dehydration, high osmotic pressure,toxic reagents and high concentration of ethanol. These unique protective properties of trehalose make it an interesting compound for several applications, for example as cryoprotectant for cells in medicine, molecular biologyand microbiology, as an effective component in cosmetics, as a stabilizer for clinical reagents and bioproducts, and even as a preservative for fresh foodstuff. Therefore, much attention has been directed to inexpensive and effective means for producing trehalose.It is thought that starch is the best substrate for production of trehalose due to its low price, high conversion rate and easily obtained raw material.It was shown that S. fibuligera is a good producer of trehalose from starch. But the yeast strain can synthesize acid trehalase and neutral trehalase which can mobilize trehalose accumulated by the cells. Therefore, it is very necessary to delete or decrease the activity of acid and neutral trehalase in the yeast in order to increased trehalose production. Later, using chemical mutagenesis techniques to obtain a mutant strain which acidic and neutral trehalase activity significantly reduce. Trehalose yield was 19.1 g per 100g of cell dry weight used use soluble starch as the substrate, and trehalose yield was 24.0 g per 100g of cell dry weight used use corn starch as the substrate. It is not economical to use soluble starch or corn starch as the substrate for production of trehalose in a large scale. 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, we found that strain A11 accumulated more trehalose in the media containing corn starch than in those containg souble starch and corn strach. The results indicated that trehalose accumulation by S. fibuliger a A11 was optimal in the medium comprised of 2.0% cassava starch,4.0% hydrolysate of soybean cake at pH 5.5 and 30℃for 48 h. At the flask level, trehalose yield was 24.8 g per 100g of cell dry weight.At the end of 2-Lfermation, 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 mg/mL of reducing sugar and 0.21 mg/mL of total sugar were left in the fermented medium. In this paper, TCA and alcohol used to extract trehalose from the cells of strain All. After isolation and purification, the crystal trehalose was obtained from the culture.Based on the shortcomings of current extraction methods of trehalose from the yeast cells by using the toxic chemicals, a mutant A83 which was thermosensitive autolytic was obatined by chemical mutagenesis, the trehalose could be automatically releasedfrom the mutant cells under the conditions of the cell wall permeability changes at 37℃, and trehalose release rate was 44.7%.
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