A strain which dramatically increases the alcohol yield during alcohol fermentation
High-gravity alcohol fermentation can raise the utilization of equipment and reduce energy of distillation to cut down the production cost. However, high-gravity alcohol fermentation does harm to growth and survival of the yeast. Common yeast can produce 12% (V/V) alcohol in a general alcohol fermentation process. If it is improved to 16%, the energy of distillation could be reduced by about 25%. More over, since the optimal temperature for alcohol yeast fermentation is around 32℃, the growth and fermentation ability of yeast will be dramatically declined if the fermentation temperature exceeds 35℃. If the heat tolerance of the yeast is improved, the alcohol production could be processed at a higher temperature so as to speed up the fermentation and reduce the wastage of cooling water.
The invention publishes a method to construct a high-tolerance ability engineered strain of alcohol yeast. The strain in which a coding neutral trehalase gene was removed can accumulate higher content of trehalose. As we all know, trehalose is a kind of bio-activity protection material which can improve the tolerance of yeast against hard conditions. The strain, AY-18, with a high intracellular content of trehalose, can survive 85.15% at the high temperature of 52℃ for 60 minutes treatment and survive 95.12% in the condition of 20% alcohol for 4 hours. The alcohol concentration after fermentation will reach 18.2% (V/V).
The invention brings great economic benefit. For the engineered strain doesn’t need special fermentation equipments and conditions, it can be used at normal alcohol plant.
Main properties of high alcohol-producing strain
Ethanol tolerance：16~20%
Heat tolerance ：40~43 ℃
Osmotic tolerance: high-sweet tolerance >40%
Ethanol yield ：16%-18%（V/V）
Alcoholic fermentation in 5000 liter fermenter
Alcohol concentration in fermented mash ：15%~18%（V/V）
Fermentation cycle： 60～72h
Ethanol ratio：51.1%～52.3%
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