Field of the Invention
The present invention relates to a ferment useful in alcohol fermentation process, and
particularly to a composite yeast suitable for high concentration alcoholic fermentation.
Background of the Invention
In the domestic alcoholic fermentation industry, yeast alone or yeast in combination with
acid protease is often used to produce alcohol, with the maximum final alcohol content in the
mash being 11-12 v/v%. If the final alcohol content in the mash is further increased, the
content of residual reducing sugar and starch in the mash would be relatively high, resulting in
the decrease of alcohol yield for the raw material and the occurrence of pollution to the
environment due to wasted residual reducing sugar, residual starch and alcoholic mash.
Therefore, it has become a significant problem in urgent need of settling to increase the final
alcohol content in the mash while keeping the contents of residual reducing sugar and residual
starch at a relatively reasonable level.
As disclosed in the application "a composite yeast suitable for high concentration
alcohol fermentation ", filed on Dec 15th, 2003 by the present applicant, a composite yeast
comprising thermostable Saccharomyces cerevisiae, acid protease, phytase and cellulase is
used as a ferment for alcohol fermentation, which may result in the mash of standard raw
material such as corn, cassava, and wheat with a final alcohol content of 14.5-15.5v/v%, with
the residual reducing sugar content being controlled at 0.2-0.4w/v% and the residual starch
content being controlled at 1.0-2.0w/v%.
Disclosure of the Invention
The objective of the invention is to provide a composite yeast suitable for high

concentration alcohol fermentation, which can significantly improve the fermentation
efficiency for thermostable Saccharomyces cerevisiae, further increase the final alcohol
content in the mash, and reduce the content of residual reducing sugar and residual starch
based on the prior art, thereby reducing the pressure to the environmental protection.
The objective of the invention is achieved by a composite yeast suitable for high
concentration alcoholic fermentation which consists of thermostable Saccharomyces
cerevisiae, acid protease, phytase, cellulase, β-glucanase, and pectinase. The contents of the
ingredients described above are (by weight):
thermostable Saccharomyces cerevisiae 61-83%
acid protease 5-30%
phytase 3-10%
cellulase 2-10%
β-glucanase 1-2%
pectinase 1-2%
In a preferred embodiment, the compounding ratios of the ingredients for the composite
yeast in the present invention are (by weight):
thermostable Saccharomyces cerevisiae 61-78%
acid protease 10-20%
phytase 3-8%
cellulase 5-8%
β-glucanase 1-1.8%
pectinase 1-1.5%
In a more preferred embodiment, the compounding ratios of the ingredients for the
composite yeast in the present invention are (by weight):

thermostable Saccharomyces cerevisiae 75%
acid protease 12%
phytase 5%
cellulase 5%
β-glucanase 1.5%
pectinase 1.5%
The thermostable Saccharomyces cerevisiae in the present invention is a saccharifying
strain in the form of solid and particulate, with the content of active cells being generally 35
billion/g. Said Saccharomyces cerevisiae converts sugar into alcohol in alcoholic fermentation
process. It has the advantages of broad processing temperature range, thermostability, alcohol
resistance and high reproductive ability. Also, said yeast is suitable for producing rice wine,
liquor, fruit wine, spirits of wine, vinegars, and the like.
Acid protease, phytase, cellulase, p-glucanase, and pectinase act to decompose the raw
material and provide nutrients and stress tolerance protection.
Acid protease is an enzyme of grey solid powder with an enzymatic activity being higher
than 50,000 u/g; cellulase is an enzyme of grey solid powder with an enzymatic activity being
higher than 1,800 u/g; phytase is an enzyme of milk white solid powder with an enzymatic
activity being higher than 5,000 u/g; P-glucanase is an enzyme of light yellow solid powder
with an enzymatic activity being higher than 800 u/g; and pectinase is an enzyme of light
yellow solid powder with an enzymatic activity being higher than 2,000 u/g.
All the raw materials used in the composite yeast of the present invention are
commercially available.
As the composite yeast in the present invention is a microbial product, the ingredients
are measured by weight. For example, 100 g of the composite yeast product comprises 61-83 g

of thermostable Saccharomyces cerevisiae (i.e. more than 20 billion per gram), 5-30 g of acid
protease (2,500,000-15,000,000 u of enzymatic activity, calculated on the basis of the content
of 50,000 u/g, i.e. 2,500-15,000 u/g), 3-10 g of phytase (150,000-500,000 u of enzymatic
activity, calculated on the basis of the content of 5,000 u/g, i.e. 150-500 u/g), 2-10 g of
cellulase (36,000-180,000 u of enzymatic activity, calculated on the basis of the content of
1,800 u/g, i.e. 36-180 u/g), 1-2 g of (3-glucanase (8,000-16,000 u of enzymatic activity,
calculated on the basis of the content of 800 u/g, i.e. 8-16 u/g), and 1-2 g of pectinase
(20,000-40,000 u of enzymatic activity, calculated on the basis of the content of 2,000 u/g, i.e.
20-40 u/g).
In preparing of the composite yeast of the present invention, the compounding ratios of
the ingredients described above may depend on the types of the raw materials used by the
alcohol producer. The ingredients are thoroughly mixed together by mechanical or manual
agitation, and then packaged into desired specifications.
The composite yeast of the present invention has the advantages of increasing fermented
alcohol content, decreasing contents of residual starch and residual reducing sugar, reducing
the manufacturing cost of alcohol fermentation, and increasing the yield of wine. It also has
the benefits of readily purchasable raw materials, simple manufacture technology, and
convenient application. The composite yeast of the present invention can be used as a ferment,
for fermentation of standard raw materials such as corn, cassava, and wheat, resulting in a
mash liquor with a final alcohol content of 16.0-17.0v/v%, a residual reducing sugar being
controlled at 0.15-0.25w/v%, and the content of residual starch being controlled at 0.6-1.6
w/v%, thereby decrease the burden to the environmental protection.
Embodiments of the Invention

The invention will be further described in detail with reference to examples as follows;
however, the scope of protection in the present invention is not limited to these examples.
Examples 1-3
The ingredients of the examples 1-3 are precisely weighed according to the
compounding ratios listed in the table 1, agitated for thorough mixing, and packaged as
specified to give final products.

Example 4
In this example, corn is used as raw material, and the composite yeast of the present
invention is used, for alcohol fermentation. The protocol, amounts of each component being
used, and the results are as follows.
The protocol comprises:
1. pulverizing the raw materials: the corn powder is sieved with a mesh of a size of 1.5
mm.

2. moistening the raw materials: adding hot water of 60-70 □ therein according to the
final sugar content requirement, and moistening for 30 minutes.
3. liquefaction: adding thermostable amylase in the amount of 10-20 u/g raw materials,
liquefying at 95-97□ for 1.5-2 h, cooling to 32D, and adjusting with sulfuric acid to a pH of
4.2-4.5.
4. fermentation with the addition of yeast: adding 150-200 u/g of saccharifying enzyme,
0.02% (by weight) of the composite yeast of the present invention, and 0.05% (by weight) of
ammonium dihydrogen phosphate, and fermenting at 30-35 D for 65-68 h.
5. distillation: distilling by a conventional wine fermentation process to obtain alcohol,
with the final alcohol content being 16.0-17.0v/v%, the content of residual reducing sugar
being 0.15-0.25w/v%, and the content of residual starch being 0.6-1.6 w/v%.
Comparative results in alcohol fermentation using the composite yeast of the present
invention and using ordinary ferment are shown in table 2:
Table 2. Comparison of final alcohol contents when different ferments are used, residual
reducing sugar contents, and residual starch contents

WE CLAIM:
1. A composite yeast suitable for high concentration alcohol fermentation, consisting of
thermostable Saccharomyces cerevisiae, acid protease, phytase, cellulase, P-glucanase,
and pectinase.
2. A composite yeast according to claim 1, wherein the compounding ratios of the
ingredients are:
thermostable Saccharomyces cerevisiae 61-83wt%
acid protease 5-30wt%
phytase 3- 10wt%
cellulase 2-10wt%
P-glucanase l-2wt%
pectinase 1-2wt%.
3. A composite yeast according to claim 2, wherein the compounding ratios of the
ingredients are:
thermostable Saccharomyces cerevisiae 61-78wt%
acid protease 10-20wt%
phytase 3-8wt%
cellulase 5-8wt%
p-glucanase 1-1.8wt%
pectinase l-1.5wt%.
4. A composite yeast according to claim 3, wherein the compounding ratios of the
ingredients are:
thermostable Saccharomyces cerevisiae 75wt%
acid protease 12wt%
phytase 5wt%
cellulase 5wt%
β-glucanase 1.5wt%
pectinase 1.5wt%.

The present invention relates to a composite yeast for high concentration alcohol
fermentation, which comprises thermostable Saccharomyces cerevisiae, acid protease, phytase,
cellulose, β-glucanase, and pectinase, and is suitable for the high concentration alcohol
fermentation for various raw materials. In addition to normal fermentation, the composite
yeast of the present invention can degrade the raw materials, increase the nutrient ingredients
in the mash, promote the growth of yeast and provide stress tolerance protection.