IMPACTS OF LIQUEFACTION TIME AND ENZYMES ON ETHANOL YIELD OF VERY HIGH GRAVITY PROCESSFOR BEVERAGE ETHANOL PRODUCTION
Keywords:very high gravity, broken rice, ethanol yield, liquefaction time, enzymes.
Most beverageethanol plants in Vietnam have been using the conventional process for ethanol production including liquefaction (95 – 105 oC) of a mash containing less than 200 g/l dry matter, saccharification (60 – 62 oC), fermentation (30 – 32 oC) and distillation. In this work, we developed a simultaneous saccharification and fermentation (SSF) process of rice mash at very high gravity (VHG) and investigated the impacts of liquefaction time and different enzymes on the ethanol yield of SSF-VHG process. Broken ricewas dissolved in tap water to reach 308 g/l dry matter, then the mixture was liquefied at 85 oC for either 60 minor 120 min by using alpha-amylases(Liquozyme and Spezyme Alpha), beta-glucanases(Optimash TBG and Viscozyme). SSF of liquefied mash was performed at 30 oC with the simultaneous addition of glucoamylases(Distillase ASP, Spirizyme and Amigase Mega L)with and without of protease (Fermgen),active dry yeast (Ethanol Red at 1.5 × 107 cells/ml), urea (12 mM) and KH2PO4(4 mM). Under these conditions, SSF-VHG processes finished after 96 h and achieved 15.4 - 16.5 % v/v ethanol, which were equivalent to corresponding to ethanol yield of 83.5 - 89.5 % of the theoretical yield.The increasing liquefaction time and the usage of Liquozyme, Viscozyme showed positive effects on the ethanol yield of the SSF-VHG process. Therefore, these preliminary results could be of importance to optimize the SSF-VHG process.
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