Assessment of alkaline pretreatment for the production of bioethanol from eucalyptus, sugarcane bagasse and sugarcane straw
Assessment of alkaline pretreatment for the production of bioethanol from eucalyptus, sugarcane bagasse and sugarcane straw
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DOI：
10.1016/j.indcrop.2016.09.069
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发表时间：
2016-12-30
影响因子：
5.9
通讯作者：
Colodette, Jorge Luiz
中科院分区：
文献类型：
--
作者：
de Carvalho, Danila Morais;de Queiroz, Jose Humberto;Colodette, Jorge Luiz
采用半同步糖化发酵法（SSSF），研究了不同碱负荷（5%，10%，15%NaOH w/w，以干基计）下的碱预处理对桉树、甘蔗渣和秸秆化学组成的影响。通过增加预处理中的碱用量，大量的木质素、半纤维素和纤维素被分级。生物质的化学组成基于完全质量平衡表示。通过比较预处理生物质和未处理生物质的化学组成，评估了预处理过程中生物质的化学转化。在碱用量为5%~ 15%（NaOH w/w）时，预处理对桉木、甘蔗渣和稻草的脱木素率分别为11%~ 51%、22%~ 90%和60%~ 99%。甘蔗渣和稻草中木质素的去除率高于桉木，这是由于草类木质素中游离酚基和酯键的频率较高，使木质素在碱性条件下溶解度升高。实验还观察到甘蔗渣具有37%-45%的半纤维素和0.8%-11%的纤维素的去除。对于秸秆，更高量的碳水化合物被去除，在55%-66%的半纤维素和19%-36%的纤维素的范围内。在预处理过程中，桉木中的木质素和碳水化合物片段被转化为称为“假抽提物”的新结构。将伪浸提物和天然浸提物一起定量，从而使总浸提物含量增加3.3（5%NaOH）、3.5（10%NaOH）和2.9（15%NaOH）倍，与原始原料一致。用10%NaOH预处理的桉木、15%NaOH预处理的甘蔗渣和5%NaOH预处理的稻草的乙醇产率和体积生产率最高。在最佳预处理条件下，预处理后的甘蔗渣中葡萄糖的释放率仅为51%左右。甘蔗渣的乙醇浓度最高，为8.8 g L-1，乙醇产量为0.101 g（乙醇）/g（生物质），乙醇体积生产率为0.88 g L-1h（-1）。碱负荷是碱预处理的重要控制变量，对生物质的化学转化和乙醇生产具有决定性影响。(C)2016爱思唯尔B. V.保留所有权利。
The impact of alkaline pretreatment at different alkaline charges (5%, 10% and 15% NaOH w/w, on dry basis) on the chemical composition of eucalyptus, sugarcane bagasse and straw were compared with the subsequent bioconversion into ethanol, using semi-simultaneous saccharification and fermentation (SSSF). By increasing alkaline charge in pretreatments, substantial amount of lignin, hemicelluloses and cellulose were fractionated. The chemical composition of biomasses was expressed based on the complete mass balance. The chemical transformation of biomasses during pretreatments was assessed by comparing the chemical composition of pretreated biomasses and their untreated counterparts. Pretreatments promoted delignification in the range of 11%-51% for eucalyptus, 22%-90% for bagasse, and 60%-99% for straw for the alkaline charges in the range of 5%-15% (NaOH w/w). The removal of lignin from bagasse and straw was higher than that from eucalyptus, which was due to the combined effect of higher frequency of both, the free phenolic groups and the ester bonds in grass lignin that made the lignin solubility escalate in alkaline conditions. It was also observed that bagasse had a removal by 37%-45% hemicelluloses and 0.8%-11% cellulose. For straw, higher amount of carbohydrates was removed, in the range of 55%-66% hemicelluloses and 19%-36% cellulose. Fragments of lignin and carbohydrates were converted into new structures called "pseudo-extractives" in eucalyptus during pretreatments. Pseudo-extractives and native extractives were quantified together, thus increasing the total extractives contents by 3.3 (5% NaOH), 3.5 (10% NaOH) and 2.9 (15% NaOH) times, in line with the original raw materials. Maximum ethanol yield and maximum volumetric productivity of ethanol were achieved for eucalyptus pretreated using 10% NaOH, bagasse pretreated using 15% NaOH and straw pretreated using 5% NaOH. At the optimal pretreatment condition, just about 51% glucose was released from pretreated bagasse. Sugarcane bagasse presented the highest values for the respective parameters, namely: 8.8 g L-1 ethanol concentration, 0.101g(ethanol)/g(biomass) ethanol yield and 0.88 g L-1 h(-1) volumetric productivity of ethanol. Alkaline charge proved to be an important control variable for alkaline pretreatments, with determinant effect on chemical transformations of biomasses and result on ethanol production. (C) 2016 Elsevier B.V. All rights reserved.