Co-immobilizated Saccharifying Enzymes And Yeast Ferment High-concentration Cassava Starch Mash To Produce Alcohol

The output of fuel alcohol which synthesized by grain as raw material is increasing rapidly, Due to the petroleum resources declining and international crude oil price rising. During the ethanol producing, energy consumption of cooking and distillation was the most. It accounted for 25%-30% of the whole stream consumption in the traditional cooking process. If the production process could improved, it would save most of the stream consumption in this part, which played an important role in reducing ethanol involvement load. In the system of high gravity fermentation, aluminium alginate gel as vector, which came from decomposition of endurance against phosphate, cassava starch producing ethanol was studied by co-immobilization of glucoamylase and yeast simultaneous saccharification and fermentation.At the basis of identifying the prescription of ADY active culture medium and co-immobilized enzymes multiplication active culture medium, the optimum condition of liguefaction was determined preliminarily by single factors: liquefaction temperature was 95℃, liquefaction time was 1.5 h, the adding dose ofα-amylase was 15U/g. The optimum condition of simultaneous saccharification and fermentation was determined by single factors: solid-liquid ratio was 1:2.0, pH value was 4.0-4.5, the dosage of ammonium sulfate was 0.5 g/L, the dosage of magnesium sulfate was 0.10 g/L, the dosage of potassium dihydrogen phosphate was 0.20 g/L, the dosage of glucoamylase was 250 U/g, the dosage of wet yeast was 2.5 g, gel filled rate was 50 %, fermentation temperature was 37℃. The process of simultaneous saccharification and fermentation was optimized through orthogonal experiment and effect analysis: gel filled rate was 50%, glucoamylase was 300 U/g, wet yeast was 2.5g, fermentation temperature was 37℃, pH value was 4.0-4.5, solid-liquid ratio was 1:2.0, ammonium sulfate was 0.5 g/L, magnesium sulfate was 0.20 g/L, potassium dihydrogen phosphate was 0.10 g/L. Under these condition, the ethanol content in the high-concentration mash of fermentation was 13.4%, the utilization rate of starch was 90.2%.Finally, co-immobilized enzymes was studied by experiment, such as stability of repeated use, storage stability and Km of enzymatic reaction, which was proved that, when enzymes was co-immobilized, the appetence of co-immobilized enzymes and substrate decreased, the value of Km increased; after using ten times repeatedly, the co-immobilized enzymes retained 83.47% of its initial activity, which also had excellent operation stability; the activity half-life of co-immobilized enzymes was 205.7 days, and it had high storage stability. In a word, all the character of co-immobilized enzymes had improved.