Alcohol is one kind of efficient, clean and renewable energy, its will receive more and more attention during the development process in the future. The method which adds 10% ~ 15% ethanol in the fuel oil to obtain ethanol gasoline has been promoted in some provinces of China.
Wheat B starch is one by-product of wheat starch and gluten, and its output accounts for 10%-20% of the total flour.
There are plenty of pentose substance and protein in wheat B starch, which is difficult to be extracted and utilized. Generally, starch processing uses wheat as raw material, and the production utilization rate can reach about 75%, and the remaining 1/4 is disposed as waste, it causes environmental pollution at the same time, which has become a major problem.
In the waste liquid produced by starch processing, the starch granule is small, the viscosity is large, the hydrophilicity is strong, it is not easy to dry, and the commercial value is not high. It will increase the difficulty of pollution control it above waste liquid is directly discharged. At this time, it is significant to choose B starch as the raw material for fermentation of alcohol.
β-glucanase
It is the generic terms for various enzymes that catalytic hydrolysis of β-glucan. According to different modes of action,it can be divided into internal cutting type and external cutting type. The former exists in grain seeds, some fungi and some bacteria, and it can catalyze and hydrolyse β-glucan in the cell wall of grain.
Xylanase
Xylanase, also known as 1, 4-β-xylanase,it is produced by liquid fermentation, filtration, drying technology and so on , which can decompose the glycans in the wort, reduce the viscosity of the wort, improve the filtration capacity of the wort, avoid the production of non-carbohydrate turbidity, and it is used in brewing wine.
Pentosanase
Pentosan can be degraded under the catalysis of pentosanase. The addition of pentosanase can improve the mechanical performance of dough, effectively improve the aging of dough, and increase the volume and surface area of dough.
Pullulanase
Pullulan is a polymer of maltotriose linked by α-1, 6 glucosidic bonds. Pullulanase can hydrolyze pullulan sugar, and it is one kind of amylases, which can decompose α-1, 6 glucosidic bonds in the branch points of amylopectin, and finally get amylose.
According to the different fermentation processes , they can be divided into the following aspects：
Traditional fermentation process
Wheat B starch is mixed with warm water which is about 60 ℃, and then high temperature resistant α-amylase is added for high temperature cooking and liquefaction,then it is cooled to 60 ℃ for saccharification, and it is cooled to 30 ℃ for fermentation after the saccharification.
Simultaneous saccharification and fermentation
Simultaneous saccharification and fermentation ,namely the fermentation process of SSF method, which means wheat B starch is mixed with water at 60 ℃ to make slurry, amylase is added, the temperature is kept for 30 minutes, the temperature is raised to 105℃ for liquefaction which lasts for 2 hours, the saccharifying enzyme is added after the pH value is adjusted appropriately, then the yeast is inoculated, and the fermentation is carried out at 30 ℃ and constant oscillation is carried out.
Simultaneous liquefaction and saccharification fermentation of raw materials
Wheat B starch is mixed with warm water to make slurry, after the pH is adjusted to 4.5, amylase is added firstly, then saccharifying enzyme is added, moreover activated yeast is added, and the fermentation is carried out at 30 ℃. The amount of remaining reducing sugar, the total amount of remaining sugar and the amount of yeast in the feed solution are measured at the same interval, and the reaction is stopped when the period reaches 144 hours.
The material ratio during production process leads to the great impact on alcohol fermentation. When very less amount of water is added, the solution is too thick, which easily causes the local temperature to become too high;When plenty of water is added, the solution is too dilute,and the energy consumption of alcohol distillation is very high. When the material ratio is reduced, the residual total sugar is continuously reduced, and the alcohol yield can be increased by increasing the volume of fermentation liquid. Subsequently, with the continuous increase of fermentation liquid volume, it can be seen that the increase of fermentation liquid volume will reduce the alcohol content, and the material ratio is finally determined to be 1:4.5.
With the increase of amylase supplemental amount, residual total sugar content decreases at the beginning, and then the residual total sugar content increases slowly after reaching the certain degree, while the ethanol concentration increases at the beginning and then decreases later. When the amylase supplemental amount is 20U/g, the residual total sugar content is the lowest, and the fermentation efficiency is 77.57%.
When the amount of enzyme is too less, it leads to the result that starch saccharification rate is slow, which affects the alcohol fermentation. When the amount of enzyme is over abundant, the extra excess of sugar increases the reproduction of miscellaneous bacteria, which eventually leads to the low fermentation rate. When the compound enzyme dosage is 0.08%, the ethanol concentration is in the highest level, the residual total sugar is in the lowest level, the ethanol concentration is 9.2% in the fermentation liquid, and the fermentation efficiency is in the highest level which is close to 78%. Finally, the additive amount of selected compound enzyme is 0.08%.
Saccharomycetes has its optimum living and reproduction temperature, and the temperature is the most suitable for it when the temperature is 28 ~ 34 ℃. The temperature affects the self-propagation of bacteria. The optimal temperature of compound enzyme is 40 ~ 62 ℃. Combining the above two factors,when the fermentation temperature is 38℃, the alcohol degree is in the highest level, the ethanol concentration is 9.2%, and the fermentation efficiency is 77.57%.
（1）The optimal temperature of alcohol fermentation is 38 ℃, and the optimal ratio of material and liquid is 1:4.5.
（2）The optimal additive amount of high temperature resistant amylase is 20U/g, the optimal additive amount of compound enzyme is 0.08%, the culture time is 5 days, and the pH is 4.5.
（3）The optimal additive amount of high temperature resistant amylase is 20U/g, the optimal additive amount of compound enzyme is 0.08%, the culture time is 5 days, and the pH is 4.5. Under these conditions, the attainable alcohol concentration is 9.2% and the fermentation efficiency is 77.57%.