Abstract:

In order to understand the role of oxygen (O₂) in hydrothermal pretreatment of corn stover and optimize the ethanol production process of corn stover,corn stover was pretreated under three different hydrothermal pretreatment conditions:Ⅰ(195℃,15min), Ⅱ(195℃, 15min, 12bar O₂), and Ⅲ(195℃, 15min, 12bar O₂, 2g/L Na₂CO₃). Ethanol production from pretreated corn stover by simultaneous saccharification and fermentation (SSF) with baker yeast was studied. The results showed that corn stover was divided into solid cake and hydrolysate after pretreatment. Most of the cellulose remained in the solid cake while the hemicellulose and lignin were partially solubilized and degraded due to instability. Under the three pretreatment conditions, the overall yield of cellulose after pretreatment was 91.2%, 94.6% and 95.9%, the overall yield of hemicellulose was 74.5%, 50.3% and 68.2%, the lignin mass fraction in the solid cake was 25.2%, 17.5% and 13.7%, and the total yield of glucose after enzymatic hydrolysis was 64.8%, 65.8% and 67.6%, respectively. It showed that oxygen had little effect on the yield of cellulose and could promote the dissolution of hemicellulose. Oxygen mainly reacted with lignin and adding sodium carbonate (Na₂CO₃) facilitated the degradation of lignin, thereby effectively obtaining higher yield of cellulose and cellulase hydrolysis efficiency. After 142h of SSF, the highest ethanol concentration of 25.0g/L was obtained by baker yeast with substrate mass fraction of 8% corn stover pretreated under the condition Ⅲ, no obvious inhibition effect occurred during fermentation process.

Key words: corn stover, ethanol, pretreatment, simultaneous saccharification and fermentation(SSF)

摘要：

为了解氧气（O₂）在玉米秸秆湿热预处理中的作用，优化玉米秸秆酒精生产工艺，本文采用三种不同湿热预处理条件处理玉米秸秆，即条件1（195℃，15min）、条件2（195℃，15min，12bar O₂）和条件3（195℃，15min，12bar O₂，2g/L Na₂CO₃），并利用酿酒酵母对预处理后的玉米秸秆同步糖化发酵酒精工艺（SSF）进行了研究。实验结果表明：经过预处理，玉米秸秆分为固体滤饼与水解液两部分，其中绝大部分纤维素以固体形式保留在滤饼中，而半纤维素和木质素由于不稳定则发生了部分水解或降解。三种预处理条件下纤维素总体收率分别为91.2%、94.6%和95.9%，半纤维素总体收率分别为74.5%、50.3%和68.2%，固体滤饼中木质素质量分数分别为25.2%、17.5%和13.7%，纤维素酶解葡萄糖率分别为64.8%、65.8%和67.6%。表明氧气对纤维素收率影响不大，能够促进半纤维素的溶出。氧气主要与木质素发生反应，尤其与碱性物质碳酸钠（Na₂CO₃）结合，能够促进木质素降解，从而获得了较高的纤维素收率和纤维素酶解葡萄糖率。因此在底物质量分数8%，经过酿酒酵母142h发酵，经条件3处理的玉米秸秆获得的酒精浓度最高，最终酒精浓度达到25.0g/L，并且整个发酵过程没有明显的抑制作用产生。

关键词: 玉米秸秆, 酒精, 预处理, 同步糖化发酵