Process for rapid production of fuel alcohol in high yield with high reactant concentration and low product concentration by direct enzymatic liquefaction and acid saccharification of yam

The invention discloses a method for producing fuel alcohol with high reagent and low product through liquefying and acid-saccharifying. The method comprises the steps of: rapidly soaking fresh yams at high/low temperature, wet-grinding to obtain slurry, liquefying with enzyme, acid-saccharifying to obtain glucose solution, adjusting pH with sodium carbonate and magnesium carbonate, fermenting, vacuum boiling, extracting alcohol, introducing mother liquid to the origin tank, adding new sugar solution to scaled volume, fermenting till no CO2 production, extracting alcohol with general method, press-filtrating the mother liquid to recover yeast dregs. Compared with the ropy, large volume mother liquid containing dregs and much water in traditional fermentation, the mother liquid of the invention has little organic matter, and has the advantages of low oxygen consumption, short period, and low cost, thus it is easy to reach the discharge standards. Yeast dregs is fine protein and nucleic acids source, can be multiple-utilized, profits for national food protection and stability, avoids pollution caused by mixed bacteria, reduces environmental pollution, saves water, energy, food, workshops, equipments and labors, improves yield, shortens production period, and reduces production cost.