稀碱预处理棕榈残渣制备纤维乙醇

Pretreatment of oil palm residues by dilute alkali for cellulosic ethanol production

摘要:

以棕榈残渣 (Empty fruit bunch，EFB) 为原料，通过预处理、酶解、发酵等过程制备纤维乙醇。首先对比了碱、碱/过氧化氢等预处理条件对棕榈残渣组成及酶解的影响，结果表明稀碱预处理效果较好。适宜的稀碱预处理条件为：NaOH浓度为1％，固液比为1∶10，在40 ℃浸泡24 h后于121 ℃下保温30 min，在该条件下，EFB的固体回收率为74.09％，纤维素、半纤维素和木质素的含量分别为44.08％、25.74％和13.89％。对该条件下预处理后的固体样品，以底物浓度5％、酶载量30 FPU/g底物酶解72 h，纤维素和半纤维素的酶解率分别达到84.44％和89.28％。进一步考察了酶载量和底物浓度对酶解的影响以及乙醇批式同步糖化发酵，当酶载量为30 FPU/g底物，底物浓度由5％增加至25％时，利用酿酒酵母Saccharomyces cerevisiae (接种量为5％，V/V)发酵72 h后乙醇的浓度分别为9.76 g/L和35.25 g/L，可分别达到理论得率的79.09％和56.96％。

Abstract:

In the study, we used oil palm residues (empty fruit bunch, EFB) as raw material to produce cellulosic ethanol by pretreatment, enzymatic hydrolysis and fermentation. Firstly, the pretreatment of EFB with alkali, alkali/hydrogen peroxide and the effects on the components and enzymatic hydrolysis of cellulose were studied. The results show that dilute alkali was the suitable pretreatment method and the conditions were first to soak the substrate with 1% sodium hydroxide with a solid-liquid ratio of 1:10 at 40 °C for 24 h, and then subjected to 121 °C for 30 min. Under the conditions, EFB solid recovery was 74.09%, and glucan, xylan and lignin content were 44.08%, 25.74% and 13.89%, respectively. After separated with alkali solution, the pretreated EFB was washed and hydrolyzed for 72 h with 5% substrate concentration and 30 FPU/g dry mass (DM) enzyme loading, and the conversion of glucan and xylan reached 84.44% and 89.28%, respectively. We further investigated the effects of substrate concentration and enzyme loading on enzymatic hydrolysis and ethanol batch simultaneous saccharification and fermentation (SSF). The results show that when enzyme loading was 30 FPU/g DM and substrate concentration was increased from 5% to 25%, ethanol concentration were 9.76 g/L and 35.25 g/L after 72 h fermentation with Saccharomyces cerevisiae (inoculum size 5%, V/V), which was 79.09% and 56.96% of ethanol theory yield.