ELEPHANT GRASS (Pennisetum purpureum Schumach) IS A PROMISING FEEDSTOCK FOR ETHANOL PRODUCTION BY THE THERMOTOLERANT YEAST Kluyveromyces marxianus CCT 7735

ABSTRACT Elephant grass (Pennisetum purpureum Schumach) is regarded as a promising feedstock for second generation ethanol production, due to its high cellulose content, biomass production and rapid growth. The yeast Kluyveromyces marxianus CCT 7735 is capable of producing ethanol from agroindustrial residues, such as lignocellulosic biomass. Therefore, this study aimed to establish the optimal conditions for ethanol production by K. marxianus CCT 7735 from elephant grass. Five factors were evaluated: temperature (35-45 ºC), pH (4.5-5.8), agitation (50-150 rpm), cellulase concentration (7.5-22.5 FPU/mL) and elephant grass biomass (8-16% w/v). Enzymatic concentration (22.5 FPU/mL), biomass concentration (16% w/v) and temperature (38 ºC) were the significant optimized factors. K. marxianus CCT 7735 produced a high ethanol concentration (around 45.5 g/L) under these optimized conditions, which is considered feasible in terms of energy requirements in the distillation step.

摘要 象草（Pennisetum purpureum Schumach）因纤维素含量高、生物量产率可观且生长速度快，被视作第二代燃料乙醇生产的极具潜力的原料。马克斯克鲁维酵母（Kluyveromyces marxianus）CCT 7735可利用农林工业残渣（如木质纤维素生物质）生产乙醇。因此，本研究旨在确立马克斯克鲁维酵母CCT 7735以象草为底物生产乙醇的最优工艺条件。本次研究共评估了5项影响因素：温度（35~45℃）、pH值（4.5~5.8）、搅拌速率（50~150 rpm）、纤维素酶浓度（7.5~22.5 FPU/mL）以及象草生物质浓度（8%~16% w/v）。经优化筛选，纤维素酶浓度（22.5 FPU/mL）、生物质浓度（16% w/v）与温度（38℃）为对乙醇生产具有显著影响的关键因素。在上述优化条件下，马克斯克鲁维酵母CCT 7735可实现约45.5 g/L的乙醇产量，该产量在蒸馏环节的能耗要求层面具备工业化应用可行性。