| β-D-glucan, could offer texture like as fat, is applied to food flavourings, cheese and sausage as food additive; it has drawn more concerns in functional food and feed additives mainly due to the biological activity of immunoregulatory, antitumor, hypocholesterolemit and so on. At present, the utilization of yeast cell, in addition to yeasty flour products and wine-brewing, is mostly the production of yeast extracts applied on spice and culture medium, the remaining of the sediment is as fodder for sell. So, the further utilization of yeast cell on the production of yeast extracts and the extraction of high purityβ-D-glucan, could bring remarkable economic benefits. Consequently, the subject is gradually a hot spot. In order to improve the purity and yield ofβ-D-glucan and to avoid the environmental problems and degradation ofβ-D-glucan by use of stong acid and alkali, this study odopted a new method comprising hot water and enzyme extractions to extract pureβ-D-glucan from Saccharomyces cerevisiae. It includs the preparation of the cell walls, the extraction and purification ofβ-D-glucan, and analysis of the composition and structural.The results concluded from experiments were as follows.1. Yeast cell wall is separated by homogenizing combined with enzyme , The effects of the cell concentration, pressure and times of homogenization, autolysis time on effects of yeast autolysis were investigated. Using autolysis time, times of homogenization and quantity of enzyme as factors, the text results showed that the optimal conditions were autolysis time, 20 h; times of homogenization,4; quantity of enzyme,1.5% through orthogonal experiments. A new process comprising hot water extraction, removal of the lipids and protease treatment was studied for the isolation ofβ-D-glucan from yeast cell walls. The effects of different pH, solid-liquid ratio, extraction temperature and time on extraction ofβ-D-glucan were investigated. The optimum process conditions were determined as following: the solid-liquid ratio, 1:15; pH, 8; temperature, 120℃; time, 3 h. The purity ofβ-D-glucan was 41.51% respectively by the process. In order to improve the purity ofβ-D-glucan, lipid extraction and enzymatic treatment were used to remove the remaining proteins and lipids. Finaly,β-D-glucan is obtained in a purity of 80.16%, the yield is 25.4%.2. This study established a way, internal standard method, to determine the content ofβ-D-glucan, and comparised with external standard method. The results indicated that the Alabinose made a bid to the sample to determine the content ofβ-D-glucan by acidolysis, the computing result was multiplied by 0.9, the RSD is between 1.1%-1.68%.This way is the relative to mark and the advantage is low cost and measurable, applied to the laboratory testing.3. Dramatized by FTIR: Compared with the infrared spectra of curdlan,β-D-glucan extracted by the new method in addition to contain small amounts of protein, is almost unanimous. HPSEC confirmed that the mean relative molecular weight ofβ-D-glucan extracted by the new method is 2.4×106, is undegradated. The NMR confirmed thatβ-D-glucan extracted by the new and traditional method both containβ-1,3 chain, and contain small amounts ofβ-1,6 branches.There are obviously differences on the ratio ofβ-1,3 andβ- 1,6 glucosidic bond by both methods, the kinds of yeast cell significantly effect the ratio of β-1,3 glucosidic bond.
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